Browsing by Subject "Climate change"

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Biogenic Greenhouse Gas Emissions from Agriculture in Europe - Quantification and Mitigation
(2002) Freibauer, Annette; Zeddies, Jürgen
This dissertation analyses relevant potential mitigation strategies of biogenic greenhouse gases (GHGs) in the agriculture of the European Union (EU) in light of the Kyoto Protocol. It identifies where important sources and mitigation potentials are located and what uncertainty, environmental ancillary effects and costs are associated with them. Literature reviews are performed and methodologies for environmental assessment and GHG accounting are further developed. On this basis, GHG emissions are quantified and reduction potentials are assessed at European level. In 1995, European agriculture emitted 0.84 ± 0.29 Tg N2O, 8.1 ± 1.9 Tg methane (CH4) and 39 Tg ± 25 carbon dioxide (CO2), which adds up to 470 ± 80 Tg CO2-equivalents or 11% of the overall anthropogenic greenhouse gas emissions of the EU. The detailed methodology developed here adequately resolves regional specifics of agricultural conditions and reduces the methodological uncertainty in the estimates to half of the one in the official national inventories. European agricultural soils will at maximum sequester carbon in the order of 100 Tg a-1 CO2 over the coming years, which may also provide other environmental benefits. The biological potential of bioenergy in the EU allows to substitute for 400 to 800 Tg a-1 CO2-equivalents. From an environmental perspective, the use of perennials, especially of residues and woody biomass, is preferable to intensively grown annual crops. The biological potential for technical GHG reduction measures in EU agriculture is between 100 and 200 Tg a-1 CO2-equivalents. Promising measures promote the extensivation of arable cropping by reducing nitrogen inputs, technological innovation in animal husbandry, which is best accompanied by a further decline in animal numbers, as well as rewetting drained organic soils. Most measures will provide ancillary environmental benefits. Changing the socio-economic and political frame conditions may enhance the GHG mitigation potential.
Climate change adaptation, social networks, and agricultural extension reforms in Ethiopia
(2016) Tensay, Teferi Mequaninte; Bennewitz, Jörn
Research on the impact of climate change in sub-Saharan Africa shows that climate change is expected to cause an increased frequency of extreme events such as high temperature and rainfall intensity, droughts and floods, desertification, and spread of animal and human diseases. These extreme events are likely to have a negative impact on food security. Using the case of Ethiopia, this thesis analyses the role that social network and agricultural extension can play in enhancing farmers’ ability to adapt to climate change. The thesis builds on recent research, which has highlighted the role of social networks and extension in promoting adaptation to the negative impacts of climate change. Social networks between farmers can build community resilience and increase adaptation to climate change. They also affect technology adoption and climate change adaptation through social learning, joint evaluation of new technologies and collective action. Current research on social networks in Ethiopia has mainly focused on the effects of network size on technology adoption and there is no empirical study on which types of social networks matter the most, and how do such types of social networks matter for climate change adaptation. Agricultural extension is expected to facilitate climate change adaptation through training and education of farmers, enabling them to anticipate climate change and to update their knowledge, attitudes and adaptive capabilities in response to climate change. In addition to their well-established function of promoting technologies and natural resource management practices, agricultural extension services are expected to play new roles in building farmers’ social networks and supporting climate change adaptation strategies. There are various studies on agricultural extension reforms in Ethiopia, but there are still gaps in this literature, especially regarding the capacity of the extension service to promote adaptation to climate change and to promote social networks. The purpose of this thesis is, therefore, to fill these knowledge gaps and to contribute to the current debate on the dynamic links between climate change, social networks and extension reforms. The thesis combines quantitative and qualitative methods for analysis of three inter-related research topics. First, the thesis examines farmers’ vulnerabilities to climate change and the role of adaptation in increasing productivity at the household level. Second, it assesses how the different types of social networks are related with the adoption of sustainable land management practices for climate change adaptation. Third, by examining what works and what does not work well in the agricultural extension reforms in Ethiopia, the thesis investigates the interactions between climate change, social networks and extension reforms in Amhara region of Ethiopia. The thesis is based on a mixed methods approach. It combines a quantitative analysis, using World Bank data from a survey conducted in 2011 covering 1338 farmers. The analytical methods include a probit model, an OLS analysis and an endogenous switching regression model. Qualitative research methods included Focus Group Discussions (FGDs) combined with an individual scoring technique, and a Climate Vulnerability and Capacity Analysis. The study on climate change adaptation found that the effects of climate change and adaptation practices differ across agro-ecological zones and adopter groups. In the kolla agro-ecologies, the major hazards were drought, floods, and migration. In contrast, snowfall, landslides and crop diseases were the main hazards in the dega and woyna-dega agro-ecologies. Erratic rainfall, soil erosion and livestock diseases were common hazards to all agro-ecologies. Households’ responses to the hazards were differed across the different agro-ecologies. In the kolla agro-ecologies, the most common coping strategies were reducing the number of daily meals, migration, livestock selling and utilization of irrigation. In the dega and woyna-dega agro-ecologies common coping strategies included: changing consumption patterns; adopting drought resistant crops (sorghum and millet); sale of chickens, eggs, sheep, goats, eucalyptus trees; soil conservation and tree planting; zero grazing and water harvesting. In all agro-ecologies, local institutions support communal adaptation strategies such as communal water harvesting and irrigation schemes, reforestation, rangeland enclosure and prevention of soil erosion. The empirical results also revealed that farmers who implemented climate change adaptation strategies have significantly increased their food productivity and food security, compared to farmers who did not implement such strategies. The findings regarding the relationship between social networks and sustainable land management revealed that networks with relatives have a positive impact on planting trees, but the impact of such networks on soil conservation was found to be negative. This finding can be interpreted as an incidence of self-interested behavior, since farmers may plant trees as a means of securing land holdings. When farmers are faced with the risk of losing their land to relatives, due to common heritage, they prefer planting trees to soil conservation. Farmers can reclaim all their investment costs by cutting trees, should they lose their land holding rights to relatives. In contrast, it would be difficult to regain soil conservation investment costs in this case. Friendship networks were found to be insignificant in both planting trees and soil conservation, while neighborhood ties only had a significant association with tree planting. This suggests the potential contributions of friendship and neighborhood networks, which can significantly affect sustainable land management practices, but may remain untapped. The analysis of extension conducted as part of this thesis suggests that a uniform reform approach, as pursued in Ethiopia, does not fit well with the diverse agro-ecologies and extension challenges in the country. While the number of service providers increased substantially, they still lack skills, incentives and resources, which affect their work motivation and job performance. Moreover, the planning, monitoring and evaluation system was found not to be very effective in regularly assessing what has been achieved at the farmers’ training centers and what remains to be done in the future. Similarly, there is room to improve partnerships and linkages of actors, especially by including key actors that are currently missing. Based on the above findings, this thesis derived the following policy implications: 1. The potential capacity of schools and religious organizations in supporting climate change adaptation should be tapped. The case study identified agricultural extension, health extension, NGOs, cooperatives, indigenous institutions (Iddir, Kirre, Jiggie, Debo, Iquib), microfinance institutions, schools, local governments, youth and women groups as key institutions providing rural services. However, extension organizations, cooperatives/unions, local governments and NGOs were the only institutions providing services relevant for climate change adaptation. Surprisingly, important local institutions (schools and religious organizations) did not have any short or long term plans to support climate change adaptation efforts despite the fact that they have the social capital to plan and implement some communal strategies such as terracing and planting trees on communal lands. 2. The regional and national policies should support local climate change adaptation strategies. The study showed that adaptation efforts should not be left to only farmers and local governments. Regional and national policies should support the local adaptation strategies. It was found that the absence of communal land and natural resource use policies was encouraging farmers to over utilize natural resources, and the long delay in land use rights (certification) was discouraging farmers from making long term investments on their land (e.g., tree planting and soil conservation). Therefore, the findings suggest that it would be useful to promote the introduction of communal land and natural resource use policy and a speedy land certification process. 3. The potential contributions of social networks as alternative channels of extension services should be tapped. The findings revealed that funds for agricultural extension are declining and extension managers should look for alternative source of funding and move away from a “one-size-fits-all” thinking to a “best fit” approach. It needs to become a priority for the current extension system to better understand what types of social networks matter most for technology adoption. 4. The findings also indicate that extension reforms should consider current agricultural challenges, especially climate change. In dega and woyna-daga agro-ecologies, the main challenges were getting information on climate change related hazards (rainfall and temperature), commercial marketing (cooperative development, price and new markets), post-harvest handling (drying and storage technique). In the kolla agro-ecologies, the major problems were lack of dry land farming methods (contour plowing, mulching, strip farming, summer fallow, seedbed preparation and planning in rows). So far, the extension system is not geared towards addressing these different challenges, which calls for aligning the extension reforms to the different local farming systems. 5. It can also be derived from the findings of this study that the regional government should design a new incentive system for the extension service. The case study showed that current incentives are inconsistent with the regional goal of promoting commercially oriented agriculture. Service providers in the region were found to lack the soft skills, incentives and resources to provide commercially oriented services. This finding calls for designing a new incentive system, which may include better salary, improved career prospects, and recognition as well as incentives for extra work. Such provisions will motivate and enable frontline service providers. 6. The governance and management structures of the Agricultural Development Partners’ Linkage Advisory Councils (ADPLACs) should be redesigned. The case study revealed that when measured against indicators such as information sharing and feedback, joint planning, monitoring, evaluation and implementation, the linkages between farmers, NGOs and research institutes were very weak. This calls for redesigning the governance and management structures of the Agricultural Development Partners’ Linkage Advisory Councils (ADPLACs), which was responsible for facilitating the partnership and linkages of extension actors in the region. 7. The findings of this thesis also suggest that the roles of NGOs and the private sector in the provision of extension service should be enhanced. The case study found that key actors such as the private sector and NGOs were missing from effective provision of extension services. The private sector and NGOs may have a comparative advantage in activities such as provision of improved seeds, fertilizers, pesticides, vaccination, deworming and artificial inseminations. NGO and private sector engagement in these areas will allow the regional government to free up and reallocate funds to its broader extension strategies such as development of new incentive schemes, education and training, technical advisory services, sustainable natural resource management practices and organizing farmers to link them with new markets.
Climate change and agricultural structural change : the relevance for machinery use and acquisition in Germany
(2021) Mendoza Tijerino, Francisco Antonio; Berger, Thomas
This thesis is a contribution to the research project “Regional Climate Change,” funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG – Forschergruppe 1695 Regionaler Klimawandel). The projects objective was to learn about the vulnerability and sensitivity of typical land systems in Southwest Germany and identify suitable strategies for adaptation. The doctoral work contributes with empirical and methodological insights of farmers likely management adaptations in light of the farm managerial challenges arising from climate and structural change in Germany. The agricultural structure in Germany has strongly changed in the last 60 years. Where before numerous small-scale and labor-intensive farms were observed, it is now the place where fewer and highly mechanized farms contribute to agricultural production. The ongoing agricultural structural change in Germany is characterized by a trend in which many farms exit the agricultural sector, and the remaining --growth-oriented-- farmers take over the land, reorganize their farm business, and expand their operations. Nevertheless, this trend of farm growth, which is expected to continue in the future, poses significant challenges at the farm management level: Decisions on machinery use and acquisition play a crucial role in shaping the farm cost structure, and represent a critical element for maintaining competitiveness. Particularly for the expansion efforts, farm managers face a highly complex decision-making process to acquire the proper machinery capacities for field operations. Moreover, an additional factor will need to be considered for adequate decision-making: Climate change developments and the uncertainties associated with this process will likely increase the complexity of the farmers decision-making regarding the best reorganizational strategies towards farms expansion. Changes in the natural conditions for crop growth and development will likely result in management adaptations, e.g., changing the timing for fieldwork operations or changing land-use patterns. An analysis of the complex interactions and interdependencies between the environment and the farm system, on the one hand, and the resources and production possibilities available to the farm manager in the course of farm expansion on the other hand, require adequate tools of analysis. This work analyzes three dimensions of farm machinery management in the context of climate change and agricultural structural change. The first element of analysis corresponds to an examination of the sensibility of land-use and machinery investment decisions to climate change scenarios with the agent-based MPMAS model constructed for Central Swabian Jura in Southwest Germany. The Central Swabian Jura MPMAS model is a constitutive part of the bioeconomic modeling system MPMAS_XN. The MPMAS_XN system integrates the agricultural economic agent-based software MPMAS and the plant-soil modeling software Expert-N (XN) into a fully coupled system. The assessment of the sensibility and responsiveness of the MPMAS component revealed complex adaptation responses of land-use and machinery investment decisions as a result of shifted timing in fieldwork operations (e.g., harvesting or fertilization tasks). The second element of analysis corresponds to an examination of economies of size arising from farm machinery use and acquisition decisions in arable farms that follow a typical crop rotation practiced in Germany. For the analysis, a whole-farm multiperiod mathematical program implemented in the agent-based software MPMAS was employed. Optimizations were run and evaluated at a broad range of farm sizes and two distinctive distributions of availability of fieldwork days estimated for Southwest Germany. The results allowed observing patterns of optimal farm machinery demand and cost curves for several evaluated farm sizes and distributions of available fieldwork days distributions. The third main element of this work corresponds to a methodological contribution to the MPMAS_XN model system. Within this element, the implementation, functioning, and potential of an external theory-based MPMAS module are presented. The external module represents dynamics for joint machinery investments among simulated farm agents and serves as an enhancing methodological contribution for analyzing and representing farm machinery management in the agent-based software MPMAS.
Climate change, cattle herd vulnerability and food insecurity : adaptation through livestock diversification in the Borana pastoral system of Ethiopia
(2013) Megersa Bati, Bekele; Valle Zárate, Anne
Climate change is one of the dominant drivers of changing patterns in precipitation, rise in temperature and increasing frequency of extreme weather events that present a major challenge to livestock production in arid and semi-arid environments. In the Borana region of southern Ethiopia, the resulting reduction in the resilience of rangelands and heavy cattle losses associated with recurrent droughts pose serious challenges to cattle pastoralism. This study aimed at investigating regional manifestations of climate change and variability, and their impacts on cattle production and household food security, as well as the role of livestock species diversification as an adaptation strategy of Borana pastoralists in southern Ethiopia. The study involved the use of questionnaire surveys, participatory discussions and monthly meteorological data from 1970 to 2011. A total of 242 households sampled from Yabelo and Dire districts of the Borana zone were surveyed between August 2011 and December 2011. Data collection also included cattle herd histories, which were reconstructed for a period spanning five major droughts (between 1980 and 2011), and household-level livestock mortalities due to the 2010/2011 drought. With the use of 24-hour food recalls, data on individual dietary diversity were collected from 339 respondents during the beginning (September) and the end of the short rains (December). Besides descriptive analyses, a range of statistical models including general linear models, generalized linear mixed models, generalized additive models, ordered and binary logit models, and a proportional hazard regression model were applied to different data sets using SAS version 9.3. Herders? perceptions showed that rainfall has become more unpredictable with lower amounts and shorter durations, while temperature and the frequency of droughts have increased. The analysis of empirical data revealed a similar declining trend in annual precipitation and cattle holdings, while droughts became more frequent. A spectral analysis of annual rainfall series showed a quasi-periodic cycle of about 8.4 years for annual precipitation with recurring droughts every 4.2 dry years. The Borana herders suffered heavy cattle losses and experienced severe food insecurity in consequence of increased climate variability. Hence, the study showed that climate change and variability have impacts on cattle production, pointing to a critical future for the sustainability of cattle pastoralism in southern Ethiopia. Analysis of the data on food security showed a high prevalence of food insecurity (78%) and low dietary diversity, with the majority of the households (81%) merely consuming one to three food groups. A large number of the respondents consumed no fruits, vegetables (93%) and meat (96%), suggesting a high risk of micronutrient deficiencies given the declining trend in milk intake. Livestock diversification indeed significantly has improved dietary intake and household food security. Households with large herd sizes, farmland sizes and large family sizes, or households having off-farm income sources were also found to be better-off compared to their counterparts. Analysis of the data on livestock species composition showed that all of the respondents were keeping cattle, while 94%, 85% and 40% kept goats, sheep and camels, respectively. Recurrent droughts, bush encroachment and increased cattle herd vulnerability were among the major drivers of livestock diversification. Species diversity fulfilled a broad spectrum of the herders? livelihood priorities, of which milk production and cash revenues from live animal sales were of highest importance. Adaptability assessments based on a set of nine adaptive traits showed that camels had the highest adaptive capacity, followed by goats, while cattle were the least adapted species. Species vulnerability to drought also reflected the adaptability patterns with cattle being the most vulnerable to drought followed by sheep, and camels being the most tolerant species. In general, the present study showed that climate change and its variability posed a challenge to cattle production, with recurrent droughts causing enormous mortalities and worsening household food insecurity. The adaptation measure of herders through diversifying their herd composition was found to alleviate food insecurity and reduce vulnerability to the periodic climatic shocks. To further enhance herders? adaptive capacity, implementing adaptation strategies aimed at proactively reducing vulnerability to climate risks and enhancing ex-post risk management capacity are vitally important.
Climate variability, social capital and food security in Sub-Saharan Africa : household level assessment of potential impacts and adaptation options
(2015) Assfaw, Tesfamicheal Wossen; Berger, Thomas
Climate variability and poor distribution of rainfall often causes serious agricultural production losses and worsens food insecurity. Given that the direct effects of climate change and variability are transmitted through the agricultural sector, improving farm households capacities to adapt to the adverse effects of climate-related shocks is an important policy concern. This thesis applied a stochastic Agent-based Model (ABM) that is capable of simulating the effects of different adaptation options by capturing the dynamic changes of climate and prices, as well as the dynamic adaptive process of different farm households to the impacts of these changes. The agent-based simulations conducted in this thesis address the special challenges of climate and price variability in the context of small-scale and subsistence agriculture by capturing non-separable production and consumption decisions, as well as the role of livestock for consumption smoothing. To ensure the reliability and usefulness of results, the model was validated with reference to land-use and overall poverty levels based on observed survey values. In particular, the study used disaggregated socio-economic, price, climate and crop yield data to quantify the impacts of climate and price variability on food security and poverty at the household level. Furthermore, the study explicitly captured crop-livestock interactions and the “recursive” nature of livestock keeping when examining the effects of climate and price variability. The thesis additionally examined how specific adaptation strategies and policy interventions, especially those related to the promotion of credit, improved seed varieties, fertilizer subsidy and off-farm employment, affect the distribution of household food security and poverty outcomes. In addition to impacts on household food security and poverty, the study further considered indirect impacts through changes in the price of agricultural inputs and livestock holding. In terms of coping strategies, the simulation results in this thesis show that the effects of climate and price variability on consumption are considerable, but smaller for those households with relatively large livestock endowments. In addition, the study also found that farm households with a large plantation area of eucalyptus were able to cope with the effects of variability. Therefore, our results suggest that self-coping strategies are important but not sufficient and should be complemented with appropriate policy interventions. In terms of policy interventions, the study found that policy intervention through the expansion of credit and fertilizer subsidy along with innovation through the promotion of new crop varieties that are resilient and adapted to local conditions are the most effective adaptation options for the case of Ethiopia. In addition, the simulation results underscore that adaptation strategies composed of a portfolio of actions (such as credit and fertilizer subsidy along with new technologies) are more effective compared to a single policy intervention. For Ghana, the study suggests that if expansion of production credit is complimented by irrigation, it can provide a way to achieve food security under climate and price variability. In order to design a best-fit intervention instead of a ‘one size fits all’ approach, it is important to capture the distribution of effects across locations as well as households. The great strength of this study is its agent-based nature, which enables exploration of how effects are distributed across farm households. The simulation results clearly show that poor farms are vulnerable to climate and price variability, under which they suffer food insecurity, while a small group of wealthy farms are better off due to higher prices achieved when selling crops. The result from this thesis further underscores the need for improving adaptive capacity, as a large proportion of farm households are unable to shield themselves against the impacts of price and climate variability. In what follows, the study further applied standard micro-econometric techniques to examine the role of social capital and informal social networks on consumption insurance and adoption of risk mitigating land management practices. In particular, the thesis provides evidence of the effects of different dimensions of social capital on the adoption of soil and water conservation practices across households holding different levels of risk-aversion. The results of the study underscore that social capital plays a significant role in enhancing the adoption of improved farmland management practices and suggests that the effect of social capital across households with heterogeneous risk taking behaviour is different. Finally, by combining household panel data, weather data, self-reported health shocks and detailed social capital information, the last section is able to analyze how social capital buffers some of the implications of weather shocks.
Communicating climate change : how proximising climate change and global identity predict engagement
(2018) Loy, Laura Sophia; Trepte, Sabine
The majority of scientists express an urgent need to limit climate change in order to ensure sustainable development, but our societies are not reacting decisively enough to achieve this goal. My research aims to understand how news about climate change can be communicated to convey scientific knowledge and support climate protection. Proximising climate change by focussing on local instead of global or remote consequences has been recommended as a promising communication strategy. The reasoning is that many people seem to perceive climate change as a phenomenon that affects mainly other people in far-off places (i.e., psychological socio-spatial distance). Proximising might bring climate change closer. However, the recommendation still lacked convincing empirical evidence. Thus, my research investigated the communication of proximity vs. distance in news coverage. Specifically, I examined the process assumed to be behind proximising effects, namely a reduction of the psychological socio-spatial distance of climate change, which might increase issue relevance and in turn promote climate protective behaviour and climate change knowledge. In Study 1 (N = 498), people were asked to what extent the news communicated climate change as something affecting mainly other people in distant locations. The more they perceived news communication as socio-spatially distant, the higher their psychological socio-spatial distance of climate change and the lower relevance they attributed to the issue. Perceived communicated socio-spatial distance was indirectly and negatively related with climate protective behavioural knowledge through higher psychological socio-spatial distance. Study 2 (N = 99) found no evidence that communicating socio-spatial proximity vs. distance of climate change in a news text influences psychological socio-spatial distance, relevance attributed to the news text, climate protective behaviour, and climate change knowledge. However, the test power was not sufficient to detect small effect sizes. In Study 3 (N = 508), proximising climate change in a news text decreased the psychological socio-spatial distance of climate change and indirectly and positively predicted climate protective behaviour as well as climate change knowledge through lower psychological socio-spatial distance and higher relevance attribution. While the indirect relations were small, stronger relations might arise if people repeatedly receive local information. I thus suggest that it is worthwhile to complement news about global climate change with reports about regional impacts. As a second objective, I aimed to illuminate whether the concept of a global identity helps to explain why proximising might not always be necessary or useful. I assumed that the more people identify with people all over the world, the more relevant they evaluate climate change to be and the more they are motivated to take climate protective action and acquire climate change knowledge. Moreover, I supposed that people with a strong global identity might evaluate climate change as relevant regardless of whether they perceive that the consequences mainly affect other people in distant places. In other words, a global identity might bridge the psychological socio-spatial distance of climate change. In Study 1, global identity positively predicted the relevance attributed to climate change and climate protective behaviour, as well as climate change knowledge indirectly through relevance attribution. In Study 2, the global identity dimension of self-investment positively predicted climate protective behaviour. However, global identity did not bridge the psychological socio-spatial distance of climate change in either study. I further reasoned that the negative relation between psychological socio-spatial distance and relevance attribution might be weaker if global identity is made salient. In other words, a salient global identity might bridge the psychological socio-spatial distance of climate change. In Study 3, before reading the news text, participants watched either a control video or a video showing a man dancing with people all over the world, which communicated a feeling of connectedness. While participants who received the control video evaluated the news text as less relevant as their psychological socio-spatial distance of climate change increased, there was no such relation among participants who received the connectedness video. Moreover, communicated proximity vs. distance in the news text did not indirectly predict climate protective behaviour and climate change knowledge in the latter group. This suggests that communicating connectedness might be a way to bridge the distance of climate change communication and render issues that are perceived as affecting mainly other people in far-off locations more relevant to recipients.
Differences in mucilage properties and stomatal sensitivity of locally adapted Zea mays in relation with precipitation seasonality and vapour pressure deficit regime of their native environment
(2023) Berauer, Bernd J.; Akale, Asegidew; Schweiger, Andreas H.; Knott, Mathilde; Diehl, Dörte; Wolf, Marc‐Philip; Sawers, Ruairidh J. H.; Ahmed, Mutez A.
With ongoing climate change and the increase in extreme weather events, especially droughts, the challenge of maintaining food security is becoming ever greater. Locally adapted landraces of crops represent a valuable source of adaptation to stressful environments. In the light of future droughts—both by altered soil water supply and increasing atmospheric water demand (vapor pressure deficit [VPD])—plants need to improve their water efficiency. To do so, plants can enhance their access to soil water by improving rhizosphere hydraulic conductivity via the exudation of mucilage. Furthermore, plants can reduce transpirational water loss via stomatal regulation. Although the role of mucilage and stomata regulation on plant water management have been extensively studied, little is known about a possible coordination between root mucilage properties and stomatal sensitivity as well as abiotic drivers shaping the development of drought resistant trait suits within landraces. Mucilage properties and stomatal sensitivity of eight Mexican landraces of Zea mays in contrast with one inbred line were first quantified under controlled conditions and second related to water demand and supply at their respective site of origin. Mucilage physical properties—namely, viscosity, contact angle, and surface tension—differed between the investigated maize varieties. We found strong influences of precipitation seasonality, thus plant water availability, on mucilage production (R2 = .88, p < .01) and mucilage viscosity (R2 = .93, p < .01). Further, stomatal sensitivity to increased atmospheric water demand was related to mucilage viscosity and contact angle, both of which are crucial in determining mucilage's water repellent, thus maladaptive, behavior upon soil drying. The identification of landraces with pre‐adapted suitable trait sets with regard to drought resistance is of utmost importance, for example, trait combinations such as exhibited in one of the here investigated landraces. Our results suggest a strong environmental selective force of seasonality in plant water availability on mucilage properties as well as regulatory stomatal effects to avoid mucilage's maladaptive potential upon drying and likely delay critical levels of hydraulic dysfunction. By this, landraces from highly seasonal climates may exhibit beneficial mucilage and stomatal traits to prolong plant functioning under edaphic drought. These findings may help breeders to efficiently screen for local landraces with pre‐adaptations to drought to ultimately increase crop yield resistance under future climatic variability.
Editorial: Seed behavior in response to extreme environments
(2023) Zhu, Jinlei; Wang, Lei
Effects of elevated soil temperature and altered precipitation patterns on N-cycling and production of N2O and CO2 in an agricultural soil
(2016) Latt, Yadana Khin; Kandeler, Ellen
Both temperature and precipitation regimes are expected to change with climate change and are, at the same time, major environmental factors regulating biogeochemical cycles in terrestrial ecosystems. Therefore, crop water availability, soil nitrogen transformations, losses, and uptake by plants as well as CO2 emissions from soil are likely to be changed by climate change. Agriculture is known to be one of the most important human activities for releasing significant amounts of N2O and CO2 to the atmosphere. Due to global concern about the changing climate, there has been a great interest in reducing emissions of N2O and CO2 from agricultural soils. CO2 and N2O are produced in soil primarily by microbial processes. Their production and emissions from the soil are controlled by a number of environmental variables including inorganic N availability, soil temperature and water content. Agricultural management practices, such as irrigation, affect these environmental variables and thus have the potential to dramatically alter N2O and CO2 emissions from the soil. The present study is titled "Effects of elevated soil temperature and altered precipitation patterns on N cycling and production of N2O and CO2 in an agricultural soil". The objectives of this study were: to determine the effects of elevated soil temperature on N cycling in a winter wheat cropping system, to investigate the short-term response of N2O and CO2 fluxes during rewetting of soils after extended dry periods in summer, and to determine the effects of different degrees of rewetting on the CO2 emission peaks after rewetting in laboratory incubations. In the 1st experiment, we used the Hohenheim Climate Change (HoCC) experiment in Stuttgart, Germany, to test the hypothesis that elevated soil temperature will increase microbial N cycling, plant N uptake and wheat growth. In the HoCC experiment, soil temperature is elevated by 2.5°C at 4 cm depth. This experiment was conducted at non-roofed plots (1m x 1m) with ambient (Ta) and elevated (Te) soil temperature and with ambient precipitation. In 2012, winter wheat (Triticum aestivum) was planted. C and N concentrations in soil and aboveground plant fractions, soil microbial biomass C and N (Cmic and Nmic), mineral N content (NH4+ - N and NO3- - N), potential nitrification and enzymes involved in nitrogen cycling were analyzed at soil depths of 0-15 and 15-30 cm at five sampling dates. The plants were rated weekly for their phenological development and senescence behavior. We found that an increase in soil temperature by 2.5oC did not have a persistent effect on mineral N content and the activity of potential nitrification within the soil. Plant growth development also did not respond to increased soil temperature. However microbial biomass C and N, and some enzyme activities involved in N-cycling, tended to increase under elevated soil temperature. Overall, the results of this study suggested that soil warming by 2.5oC slightly stimulates soil N cycling but does not alter plant growth development. In the 2nd experiment, in 2013, the effects of a change in the amount and frequency of precipitation patterns on N2O and CO2 emissions were studied after the two dry periods in summer in the HoCC experiment. N2O and CO2 gas samples were taken from four subplots (1m x 1m) of each roofed plot exposed to ambient (Ta) or elevated (Te) soil temperature and four precipitation manipulations (ambient plot, reduced precipitation amount, reduced precipitation frequency, and reduced precipitation amount and frequency). We found that CO2 emissions were affected only by temperature, but not by precipitation pattern. It can be said that N2O and CO2 emissions after rewetting of dry soil were not altered by changing precipitation patterns during dry periods in summer. In the year 2014, using laboratory incubations, we also measured the short-term response of CO2 production to a rewetting of dry soil to different volumetric water contents for 24 hours. This study was conducted by manipulating microcosms with agricultural soil from the HoCC experimental site, which had been exposed to severe drought conditions of three months duration for each of the last six years. The results showed that CO2 production increased with increases in the water content of soils by rewetting at 5%, 15%, 25%, 35% and 45% VWC. With increasing water additions more peaks in CO2 production were detected and different temporal patterns of CO2 emission were affected by adding different amounts of water. It might be due to the fact that with greater water additions successively larger pore sizes were water filled and therefore different bacterial groups located in different pore size classes might have contributed to CO2 production. In summary, the results from field study suggested that climate warming will affect N cycling in soils in an agricultural cropping system. The results from both field and microcosm rewetting experiments contribute to a better understanding of C and N dynamics in soil by investigating the effect of varying soil water content on the emission of N2O and CO2.
Environmental and farm management effects on food nutrient concentrations and yields of East African staple food crops
(2021) Fischer, Sahrah; Cadisch, Georg
Hidden hunger affects two billion people worldwide, particularly children and pregnant women. Human health and well-being are dependent on the quality and quantity of food consumed, particularly of plant-based foods. Plants source their nutrients from the soil. Essential nutrients for both, plants and humans, therefore, predominantly originate from the soil. Very little is known about the influence of environmental factors (e.g. soil types and abiotic factors, such as weather), or farm management choices (e.g. fertilisation or agrobiodiversity), on nutrient concentrations of edible crop parts. The main aim of this thesis was, therefore, to analyse the effects of soil fertility, farm management, and abiotic factors such as drought, on the quantity (yields) and quality (nutrient concentrations) of essential macro- (Mg, P, S, K, Ca) and micronutrients (Fe, Zn, Mn and Cu), of the edible parts of three East African staple food crops, i.e. maize (Zea mays L.), cassava (Manihot esculenta} Crantz), and matooke (East African Highland Banana (Musa acuminata Colla)), and discuss the resulting implications for food and nutrition security. Two research areas were selected in East Africa, one with a high fertility soil (Kapchorwa, Uganda - Nitisol) and one with a low fertility soil (Teso South, Kenya – Ferralsol). In each region, 72 households were randomly selected, and leaf and edible crop parts, and soil samples collected on three fields per household, organised by distance (closest, mid-distance, and farthest field). Maize and cassava were collected in Teso South, maize and matooke were collected in Kapchorwa. Yields, fertilizer usage and species richness (SR) and diversity (SD) were recorded per field. The total nutrient concentrations were measured in all samples collected (soils and plant parts). A drought occurring in the second rain season of 2016 provided the opportunity to analyse water stress effects on crop quantity and quality (Chapter 2). Edible part samples and yields collected in both seasons were compared. Soil chemical and physical properties, together with farm management variables, were compared to edible part nutrient concentrations and yields using a Canonical Correspondence Analysis (CCA) (Chapter 3). To understand the strength of association between the measurements routinely done by agronomists (leaf measurement) and nutritionists (edible part measurement), samples of each crop were collected, and were compared to each other and to yields, using a bivariate linear mixed model (Chapter 4). During the severe drought, nutrient concentrations in Kapchorwa decreased significantly from normal to drought season in both crops. In contrast, during the moderate drought in Teso South, nutrient concentrations increased significantly in both crops. Lacking nutrient phloem mobility is suggested to play a vital role in mobilisation of micronutrients (Fe, Mn, and Cu), as shown by their decreased concentration under severe drought in the yields of both crops in Kapchorwa (Chapter 2). Soil type had a very strong effect on food nutrient concentrations. Maize grain nutrient concentrations and yields, for example, were significantly higher for all nutrients measured on higher fertility soils. Maize grain had the highest correlations with soil factors. In contrast, corresponding correlations to management factors were much weaker (Chapter 3). Concerning the comparison of nutrient concentrations in different plant parts, low phloem mobile nutrients Ca, Mn, Fe, Zn, and Cu showed the largest differences in correlations between leaves and edible parts. In the same comparison, perennial crops (matooke and cassava) showed lower correlations between leaves and edible parts, than annual crops (maize) (Chapter 4). Environmental factors, such as drought impacted food nutrient concentrations. Severe drought caused a potential “double-burden” for consumers, decreasing both yields and nutrient concentrations, particularly of micronutrients. Considering food nutrient concentrations, apart from yield, as response variables in agronomic trials (e.g. fertilisation or soil improvement strategies) would contribute towards discounting the notion that crops growing on fertile soils always produce healthy and high-quality foods. Leaves may provide information on plant health, however, do not provide enough information to gauge both yields and food quality, particularly regarding micronutrients. The results also showed that measuring the edible part is vital to assessing food quality, particularly due to the observed effects of nutrient mobility, affecting particularly micronutrients and Ca. Ending hunger and improving food and nutrition security for all, particularly when confronted with global change issues such as degrading soils and a changing climate, requires a collaborative effort by all disciplines concerned.
Genotypic responses of rainfed sorghum to a latitude gradient
(2016) Abdulai, Alhassan Lansah; Asch, Folkard
Climate change poses various challenges to crop production systems. Coping with the changing climate requires adaptation strategies that will enhance the resilience of crop production systems to the resultant aberrant weather. However, the impacts of the changing climate are extremely difficult to predict because the associated extreme events result in a complex of abiotic stresses. These stresses act singly or in synergy with others to affect physiological processes at the different growth and development stages of crop plants. Currently, the physiological and phenological (developmental) response mechanisms of crops, as well as adaptation of cultivars to these stresses are not very clear and well understood. The complex interactions between crops and abiotic stresses make it difficult to accurately predict crop responses to climate change using the available crop growth models that have been parameterized and validated using some climate scenarios. While prediction of the complex ideotype-trait combinations may benefit breeders, physiological models that are well validated for target environments are equally important. Therefore, this study investigated elite grain sorghum genotypes from three races (Caudatum, Durra, and Guinea) and a Guinea-Caudatum composite, with different degrees of sensitivity to photoperiod and adaptation to a wide range of latitude locations, for their grain yield and yield stability responses to different environments. The aim was to calibrate growth models in for use in quantifying climate change effects on rainfed sorghum production systems. Field experiments were established to investigate the yield performance and yield stability of ten genotypes in eighteen environments created from a factorial combination of three locations (along a latitudinal gradient) and three monthly-staggered dates of sowing within years in 2008 and 2009. Field trials to study the phenology of seven of the ten genotypes were also established in a similar fashion in 2009 and 2010. Data were also collected on yield and other traits for the first two dates of sowing on six of the genotypes used for the yield performance trial to analyze the relations between grain yield and the selected traits and also evaluate the potential of path analysis in improving understanding of trait yield relations of grain sorghum. Mean grain yields of 0 to 248 g m were recorded across environments and from 74 to 208 g m-2 across the 10 genotypes and generally reduced with delayed sowing. Grain yield was significantly influenced by the main and interactive effects of location, year, sowing date, and genotype, necessitating the assessment of yield superiority and stability for each of the ten cultivars. The only two Caudatum cultivars (Grinkan and IRAT 204) were ranked among the top three by six of the indices. The study also brought to the fore that some yield stability indices correlate perfectly or very highly and could be substituted one for the other when assessing yield stability of sorghum. Very strong correlations were found between grain yield and each of shoot biomass, panicle weight, the number of grains per panicle, and threshing ability across environments, but path coefficient analysis confirmed that these traits are auto-correlated, with grains per panicle being the major mediating trait in all the relationships. Relationships between grain yield and the remaining traits were weak to medium and very inconsistent across the environments. This study brings to the fore, the location- and / or environment-specific adaptation of existing genotypes which should be exploited for tactical adaptation to changed climates, whiles genotypes with general or wider adaptations to environments are being sought. The phenology study showed that for photoperiod sensitive (PPS) genotypes, the number of days from emergence to panicle initiation and the number of leaves increased with latitude and decreased with sowing date, a day-length difference between locations of < 8 minutes increasing crop duration of some varieties by up to 3 weeks and decreasing number of leaves by up to 11 for the same sowing date. Some varieties exhibited photoperiod-insensitivity at one location and photoperiod-sensitivity at another location, indicating the complex nature of photoperiod responses. The study also showed that existing models do not accurately simulate the effect of latitude on the phenology of PPS sorghum, and latitude has to be taken into account in adjusting coefficients to improve the accuracy of such simulations. We conclude that genotypic response of rainfed sorghum is influenced by latitude, sowing date, and their interactions, but very little by years. Some existing cultivars could be deployed as tactical adaptive measures, while efforts are intensified to develop strategic adaptive measures. If changes in rainfall and temperature reduce the length of growing seasons, genotypes which are currently adapted to higher latitudes could easily be shifted southwards to lower latitudes, while those at lower latitudes may fit poorly into the new environments. A large potential for contributing to food security exist for the low latitudes if climates change in the direction predicted in future. It is absolutely necessary to develop new models that will be able to accurately simulate effects of sowing date and latitude on phenology. More research is needed to understand physiological response mechanisms of the pronounced latitude effects on sorghum phenology.
Impact of climate change on future barley (Hordeum vulgare L.) production in Ethiopia
(2022) Gardi, Mekides W.; Graeff-Hönninger, Simone
Summary Barley (Hordeum vulgare L.) is the fourth major cereal crop in the world, and it accounts for 8% of the total cereal production in Ethiopia based on cultivation location. Farmers may face unpredictable rainfall and drought stress patterns, such as terminal drought, in which rainfall ends before crops reach physiological maturity, posing a challenge to crop production. Furthermore, climate change is expected to reduce crop production/yield due to increases in carbon dioxide (CO2) and ozone (O3) concentrations, temperatures, and extreme climate events such as floods, storms, and heatwaves, highlighting the importance of taking action to develop climate-resilient cultivars and secure future crop production. Against this background, a meta-analysis study was conducted to synthesize and summarize to assess the overall effect of elevated CO2 (eCO2), and its interaction with nitrogen (N) and temperature on barley grain yield and yield components. A climate chamber experiment was carried out to identify the impacts of projected CO2 enrichment (eCO2) on a set of landraces and released cultivars of Ethiopian barley. The crop-climate modeling approach was used to simulate future climate change and to identify the impacts of climate change on selected barley genotypes and study locations in Ethiopia. Furthermore, adaption options were simulated and identified. Publication I, aimed to answer how eCO2 and its interaction with N and temperature affects barley yield at a global level. Peer-reviewed primary literature (published between 1991-2020) focusing on barley yield responses to eCO2, temperature, and N were searched on different search engines. The response of five yield variables of barley was synthesized and summarized using a meta-analysis technique. Different experimental factors which might affect the estimation of the response of barley yield to eCO2 were calculated. The results revealed that eCO2 increased barley yield components such as vegetative biomass (23.8%), grain number (24.8%), and grain yield (27.4%) at a global level. Barley vegetative biomass and grain yield were increased under the combination of eCO2 with the higher N level (151-200 kg ha-1) compared to the lower levels. Grain number and grain yield were increased when eCO2 combined with temperature level (21-25°C) this response was not evident. The response of barley to eCO2 was different among genotypes and experimental conditions. Publication II, the genetic diversity of Ethiopian barley was screened under eCO2 enrichment in a controlled exposure experiment. The experiment was conducted at the Institute of Landscape and Plant Ecology, the University of Hohenheim in 2019. A total of 30 (15 landrace and 15 released cultivars) were grown under two levels of CO2 concentration (400 and 550 ppm) in climate chambers. Plant-development-related measurements and water consumption were recorded once a week and yield was measured at the final harvest. A significant increment in plant height by 9.5 and 6.7%, vegetative biomass by 7.6 and 9.4%, and grain yield by 34.1 and 40.6% in landraces and released cultivars, respectively were observed due to eCO2. The effect of eCO2 was genotype-dependent, for instance, the response of grain yield in landraces ranged from -25% to +122%, while it was between -42% to 140% in released cultivars. The water-use efficiency of vegetative biomass and grain yield significantly increased by 7.9 and 33.3% in landraces, with 9.5 and 42.9% improvement in released cultivars, respectively under eCO2. Comparing the average response of landraces versus released Ethiopian barley cultivars, the highest percentage yield change due to eCO2 was recorded for released cultivars. However, higher actual yields under both levels of CO2 were observed for landraces. Publication III, Current and future climate change, its impact on Ethiopian barley production, and adaptation options were simulated using the DSSAT-CERES-Barley model. Climate change scenarios were set up over 60 years using Representative Concentration Pathways (4.5 and 8.5), and five Global Climate Models. The changes in Ethiopian climate and barley production were calculated from the baseline period (1981-2010). Different sowing dates, sowing densities, and fertilizer levels were tested as climate change impact mitigation strategies in a sensitivity analysis. The analysis of a crop-climate model revealed an increasing trend of temperature (1.5 to 4.9 °C) and a mixed trend of rainfall (-61.4 to +86.1%) in the barley-producing locations of Ethiopia. The response of two Ethiopian barley cultivars was simulated under different climate change scenarios and a reduction of yield up to 98% was recorded for cv. Traveler while cv. EH-1493 exhibited a reduction of up to 63%. Even though a similar trend was observed for most of the studied locations, cv. EH-1493 showed a yield gain of up to 14.7% at Holeta. The sensitivity analysis on potential adaptation options indicated that the negative effects of climate change could be mitigated by earlier sowing dates, with a 25% higher sowing density and a 50% higher fertilizer rate than the current recommendation. The results of the present dissertation show the change in the Ethiopian climate and its impact on barley production. Barley production could benefit from eCO2; however, the response varied among genotypes, additional stress, and experimental condition. A reduction of barley grain yield under different climate change scenarios was observed mainly due to increasing temperature. However, the reduction could be minimized through different adaptation options. The information from the current dissertation could be used to identify agro-economic implications of CO2 enrichment and climate variability on yield regarding appropriate genotype selection and adaptation of regional cropping systems (e.g., management and breeding strategies). Further experimental studies assessing crop production, nutritional quality, and adaptation options under multifactor climate conditions should be carried out to increase basic understanding and identify genotypes for future breeding programs.
Impacts of temperature increase and change in precipitation pattern on ecophysiology, biomass allocation and yield quality of selected crops
(2023) Drebenstedt, Ireen; Högy, Petra
Climate change poses a challenge for the production of crops in the twenty-first century due to alterations in environmental conditions. In Central Europe, temperature will be increased and precipitation pattern will be altered, thereby influencing soil moisture content, physiological plant processes and crop development in agricultural areas, with impacts on crop yield and the chemical composition of seeds. Warming and drought often occur simultaneously. The combination of multiple abiotic stresses can be synergistic, leading to additive negative effects on crop productivity. To date, little information is available from multi-factor experiments analyzing interactive effects of warming and reduced precipitation in an arable field. In addition, one major issue of studying climate change effects on crop development in the long-term is that weather conditions can vary strongly between years, e.g., with hot and dry summers in comparison to cool and wet ones, which directly affects soil moisture content and indirectly affects crop development. Thus, considering yearly weather conditions seems to be important for the analyses of climate change effects on aboveground biomass and harvestable yield of crops. The aim of the present work was to identify single and combined effects of soil warming (+2.5 °C), reduced summer precipitation amount (-25%), and precipitation frequency (-50%) on crop development, ecophysiology, aboveground biomass and yield as well as on yield quality of wheat, barley, and oilseed rape grown in the Hohenheim Climate Change (HoCC) field experiment. This thesis presents novel results from the HoCC experiment in the long-term perspective. Thus, aboveground biomass and yield data (2009-2018) of the three crops were analyzed with regard to their inter-annual variability, including annual fluctuations in weather conditions.This thesis consists of three publications. In the first and second publication a field experiment within the scope of the HoCC experiment was conducted with spring barley (Hordeum vulgare L. cv. RGT Planet) and winter oilseed rape (Brassica napus L. cv. Mercedes) in 2016 and 2017. The objective was to investigate the impacts of soil warming, altered precipitation pattern and their interactions on biomass production and crop yield. In addition, it was examined, whether the simulated climate changes affecting barley photosynthesis and the seed quality compounds of oilseed rape. In the third publication, long-term plant productivity data of wheat, barley, and oilseed rape were evaluated, including aboveground biomass and yield data from the field experiment in 2018 with winter wheat (Triticum aestivum L. cv. Rebell).
Influence of land use on abundance, function and spatial distribution of N-cycling microorganisms in grassland soils
(2015) Keil, Daniel; Kandeler, Ellen
This thesis focuses on the influence of land use on the abundance, function and spatial distribution of N-cycling microorganisms in grassland soils, but also on soil biogeochemical properties, as well as on enzyme activities involved in the carbon-, nitrogen-, and phosphorous cycle. The objective of this thesis was tackled in three studies. All study sites that were investigated as part of this thesis were preselected and assigned according to study region and land use within the framework of the “Exploratories for Functional Biodiversity Research – The Biodiversity Exploratories” of the Deutsche Forschungsgemeinschaft priority program 1374. The first study addressed the question whether land-use intensity influences soil biogeochemical properties, as well as the abundance and spatial distributions of ammonia-oxidizing and denitrifying microorganisms in grasslands of the Schwäbische Alb. To this end, a geostatistical approach on replicated grassland sites (10 m × 10 m), belonging to either unfertilized pastures (n = 3) or fertilized mown meadows (n = 3), representing low and high land-use intensity, was applied. Results of this study revealed that land-use intensity changed spatial patterns of both soil biogeochemical properties and N-cycling microorganisms at the plot scale. For soil biogeochemical properties, spatial heterogeneity decreased with higher land-use intensity, but increased for ammonia oxidizers and nirS-type denitrifiers. This suggests that other factors, both biotic and abiotic than those measured, are driving the spatial distribution of these microorganisms at the plot scale. Furterhmore, the geostatistical analysis indicated spatial coexistence for ammonia oxidizers (amoA ammonia-oxidizing archaea and amoA ammonia-oxidizing bacteria) and nitrate reducers (napA and narG), but niche partitioning between nirK- and nirS-type denitrifiers. The second study aimed at whether land-use intensity contributes to spatial variation in microbial abundance and function in grassland ecosystems of the Schwäbische Alb assigned to either low (unfertilized pastures, n = 3), intermediate (fertilized mown pastures, n = 3), or high (fertilized mown meadows, n = 3) land-use intensity. Plot-scale (10 m × 10 m) spatial heterogeneity and autocorrelation of soil biogeochemical properties, microbial biomass and enzymes involved in C, N, and P cycle were investigated using a geostatistical approach. Geostatistics revealed spatial autocorrelations (p-Range) of chemical soil properties within the maximum sampling distance of the investigated plots, while greater variations of p-Ranges of soil microbiological properties indicated spatial heterogeneity at multiple scales. An expected decrease in small-scale spatial heterogeneity in high land-use intensity could not be confirmed for microbiological soil properties. Finding smaller spatial autocorrelations for most of the investigated properties indicated increased habitat heterogeneity at smaller scales under high land-use intensity. In the third study, the effects of warming and drought on the abundance of denitrifier marker genes, the potential denitrification activity and the N2O emission potential from grassland ecosystems located in the Schwäbische Alb, the Hainich, and the Schorfheide region were investigated. Land use was defined individually for each grassland site by a land-use index that integrated mowing, grazing and fertilization at the sites over the last three years before sampling of the soil. It was tested if the microbial community response to warming and drought depended on more static site properties (soil organic carbon, water holding capacity, pH) in interaction with land use, the study region and the climate change treatment. It was further tested to which extent the N2O emission potential was influenced by more dynamic properties, e.g. the actual water content, the availability of organic carbon and nitrate, or the size of the denitrifier community. Warming effects in enhanced the potential denitrification of denitrifying microorganisms. While differences among the study regions were mainly related to soil chemical and physical properties, the land-use index was a stronger driver for potential denitrification, and grasslands with higher land use also had greater potentials for N2O emissions. The total bacterial community did not respond to experimental treatments, displaying resilience to minor and short-term effects of climate change. In contrast, the denitrifier community tended to be influenced by the experimental treatments and particularly the nosZ abundance was influenced by drought. The results indicate that warming and drought affected the denitrifying communities and the potential denitrification, but these effects are overruled by study region and site-specific land-use index. This thesis gives novel insights into the performance of N-cycling microorganisms in grassland ecosystems. The spatial distribution of soil biogeochemical properties is strongly dependent on land-use intensity, as in return is the spatial distribution of nitrifying and denitrifying microorganisms and the ecosystem services they perform. Yet, future work will be necessary to fully understand the interrelating factors and seasonal variability, which influence the ecosystem functioning and ecosystem services that are provided by N-cycling soil microorganisms at multiple scales.
Kyoto and the carbon content of trade
(2010) Felbermayr, Gabriel; Aichele, Rachel
A unilateral tax on CO2 emissions may drive up indirect carbon imports from non-committed countries, leading to carbon leakage. Using a gravity model of carbon trade, we analyze the effect of the Kyoto Protocol on the carbon content of bilateral trade. We construct a novel data set of CO2 emissions embodied in bilateral trade flows. Its panel structure allows dealing with endogenous selection of countries into the Protocol. We find strong statistical evidence for Kyoto commitments to affect carbon trade. On average, the Kyoto protocol led to substantial carbon leakage but its total effect on carbon trade was only minor.
Measuring and modelling carbon stocks in rubber (Hevea brasiliensis) dominated landscapes in Subtropical China
(2019) Yang, Xueqing; Cadisch, Georg
Rubber plantation has been rapidly expanded in Montane Mainland South East Asia in past decades. Limited by long-term monitoring data availability, the impacts of environmental change on rubber trees carbon stock development still not fully understood. Against global warming background, in order to better facilitate regional forest management, we applied synergetic approach combining field survey and modelling tools to improve predictions of dynamic carbon stock changes. The trade-off analysis regarding to rubber carbon stock and latex production optimization was further discussed in view of sustainable rubber cultivation. The first study explored the impact of regional land-use changes on landscape carbon balances. The Naban River Watershed National Nature Reserve (NRWNNR), Xishuangbanna, China, was selected as a case study location. Carbon stocks were evaluated using the Rapid Carbon Stock Appraisal (RaCSA) method based on tree, plot, land use and landscape level assessments of carbon stocks, integrating field sampling with remote sensing and GIS technology. The results showed that rubber plantations had larger time-averaged carbon stocks than non-forest land use types (agricultural crops, bush and grassland) but much lower than natural forest. During 23 years (1989-2012), the whole landscape of the nature reserve (26574 ha) gained 0.644 Tg C. Despite rubber expansion, the reforestation activities conducted in NRWNNR were able to enhance the carbon stocks. Regional evaluation of the carbon sequestration potential of rubber trees depends largely on the selection of suitable allometric equations and the biomass-to-carbon conversion factor. The second study developed generic allometric equations for rubber trees, covering rotation lengths of 4-35 years, within elevation gradient of 621-1,127 m, and locally used rubber tree clones (GT1, PRIM600, Yunyan77-4) in mountainous South Western China. Allometric equations for aboveground biomass (AGB) estimations considering diameter at breast height (DBH), tree height, and wood density were superior to other equations. We also tested goodness of fit for the recently proposed pan-tropical forest model. The results displayed that prediction of AGB by the model calibrated with the harvested rubber tree biomass and wood density was more accurate than the results produced by the pan-tropical forest model adjusted to local conditions. The relationships between DBH and height and between DBH and biomass were influenced by tapping, therefore biomass and C stock calculations for rubber have to be done using species-specific allometric equations. Based on the analysis of environmental factors acting at the landscape level, we noticed that above- and belowground carbon stocks were mostly affected by stand age, soil clay content, aspect, and planting density. The results of this study provide reference for reliable carbon accounting in other rubber-cultivated regions. In the last study, we explored how rubber trees growth and production response to climate change and regional management strategies (cultivation elevation, planting density). We applied the process-based Land Use Change Impact Assessment tool (LUCIA) calibrated with detailed ground survey data to model tree biomass development and latex yield in rubber plantations at the tree, plot and landscape level. Model simulation showed that during a 40-year rotation, lowland rubber plantations (< 900m) grew quicker and had larger latex yield than highland rubber (≧900m). High planting density rubber plantations showed 5% higher above ground biomass than those at low- and medium-planting density. The mean total biomass and cumulative latex yield per tree over 40 years increased by 28% and 48%, respectively, when climate change scenarios were modelled from baseline to highest CO2 emission scenario (RCP 8.5). The same trend of biomass and latex yield increase with climate change was observed at plot level. Denser plantations had larger biomass, but the cumulative latex production decreased dramatically. The spatially explicit output maps produced during modelling could help maximize carbon stock and latex production of regional rubber plantations. Overall, rubber-based system required for appropriate monitoring scale in both temporal aspect (daily-, monthly-, and yearly-level) and in spatial aspect (pixel-, land use-, watershed-, and landscape- level). The findings from present study highlighted the important application of ecological modelling tools in nature resources management. The lessons learned here could be applicable for other rubber-cultivated regions, by updating with site-specific environmental variables. The significant role of rubber tree not limited in its nature latex production, it also lies in its great carbon sequestration potential. Our results here provided entry point for future developing comprehensive climate change adaption and mitigation strategies in South East Asia. By making use of interdisplinary cooperation, the sustainable rubber cultivation in Great Mekong Regions could be well realized.
Microeconometric analysis of the impacts of climate change on German agriculture : applications and extensions of the Ricardian approach
(2015) Chatzopoulos, Thomas; Lippert, Christian
The so-called Ricardian approach is an econometrics-based climate change impact assessment frequently used by agricultural and environmental economists. The intuition behind this approach is that, in the long run, the optimal behavior of farms is climate-dependent. In essence, the approach explores the role of climate in determining farm profitability and potential adaptation, by regressing economic or behavioral measures of agricultural outcomes against climatic and various other land and site attributes. The overall output of the approach enables (i) the identification of profitability differentials due to climate differentials, (ii) marginal implicit pricing of climate, and (iii) a probabilistic exploration of long-run adaptation strategies. This cumulative dissertation took up the challenge of improving specific conceptual and methodological aspects of the Ricardian approach in order to render it a more realistic impact assessment tool. In particular, we aimed at a more efficient treatment of the variables that proxy climate, and at the imposition of structure on equations that can reflect adaptation. Three empirical studies were pursued for over 270,000 German farms at three spatial scales: districts (N = 439), community associations (n = 3,515), and communities (n = 9,684). For this reason, secondary data of various formats (e.g., farm census records, measurements by weather stations, digital images) on a host of characteristics (e.g., farm-specific, climatic, topographical, geographical) were extensively processed (e.g., integrated, geocoded, spatially interpolated, zonally rearranged) and spatially matched. We took a multi-model and multi-stage approach from an instrumental-variables (IV) perspective, which we coupled with advances from the subfield of spatial econometrics. From an empirical viewpoint, our results showed that historical climate change has generally been beneficial to the sector as a whole. The impact of historical mean annual temperature (precipitation) on average land rental prices is positive (concave). Indicatively, permanent-crop and vegetable farms value temperature more than the rest farm types, whereas forage farms, and to a certain extent mixed farms, stand out for their resilience to precipitation. Climate change in the near decades is likely to be beneficial, but the magnitude of benefits depends on the farm type one looks at.
Modeling and spatiotemporal mapping of water quality through remote sensing techniques: A case study of the Hassan Addakhil dam
(2021) El Ouali, Anas; El Hafyani, Mohammed; Roubil, Allal; Lahrach, Abderrahim; Essahlaoui, Ali; Hamid, Fatima Ezzahra; Muzirafuti, Anselme; Paraforos, Dimitrios S.; Lanza, Stefania; Randazzo, Giovanni
With its high water potential, the Ziz basin is one of the most important basins in Morocco. This paper aims to develop a methodology for spatiotemporal monitoring of the water quality of the Hassan Addakhil dam using remote sensing techniques combined with a modeling approach. Firstly, several models were established for the different water quality parameters (nitrate, dissolved oxygen and chlorophyll a) by combining field and satellite data. In a second step, the calibration and validation of the selected models were performed based on the following statistical parameters: compliance index R2, the root mean square error and p-value. Finally, the satellite data were used to carry out spatiotemporal monitoring of the water quality. The field results show excellent quality for most of the samples. In terms of the modeling approach, the selected models for the three parameters (nitrate, dissolved oxygen and chlorophyll a) have shown a good correlation between the measured and estimated values with compliance index values of 0.62, 0.56 and 0.58 and root mean square error values of 0.16 mg/L, 0.65 mg/L and 0.07 µg/L for nitrate, dissolved oxygen and chlorophyll a, respectively. After the calibration, the validation and the selection of the models, the spatiotemporal variation of water quality was determined thanks to the multitemporal satellite data. The results show that this approach is an effective and valid methodology for the modeling and spatiotemporal mapping of water quality in the reservoir of the Hassan Addakhil dam. It can also provide valuable support for decision-makers in water quality monitoring as it can be applied to other regions with similar conditions.
The need to decipher plant drought stress along the soil-plant-atmosphere continuum
(2023) Schweiger, Andreas H.; Zimmermann, Telse; Poll, Christian; Marhan, Sven; Leyrer, Vinzent; Berauer, Bernd J.
Lacking comparability among rainfall manipulation studies is still a major limiting factor for generalizations in ecological climate change impact research. A common framework for studying ecological drought effects is urgently needed to foster advances in ecological understanding the effects of drought. In this study, we argue, that the soil–plant–atmosphere‐continuum (SPAC), describing the flow of water from the soil through the plant to the atmosphere, can serve as a holistic concept of drought in rainfall manipulation experiments which allows for the reconciliation experimental drought ecology. Using experimental data, we show that investigations of leaf water potential in combination with edaphic and atmospheric drought – as the three main components of the SPAC – are key to understand the effect of drought on plants. Based on a systematic literature survey, we show that especially plant and atmospheric based drought quantifications are strongly underrepresented and integrative assessments of all three components are almost absent in current experimental literature. Based on our observations we argue, that studying dynamics of plant water status in the framework of the SPAC can foster comparability of different studies conducted in different ecosystems and with different plant species and can facilitate extrapolation to other systems, species or future climates.
Nitrous oxide emissions and mitigation strategies : measurements on an intensively fertilized vegetable cropped loamy soil
(2011) Pfab, Helena; Müller, Torsten
Nitrous oxide (N2O) is a potent greenhouse gas which is also involved in stratospheric ozone depletion. There is consensus that a reduction in N2O emissions is ecologically worthwhile. Agricultural soils are the major source of N2O emissions in Germany. It is known that high N-fertilization stimulates N2O emissions by providing substrate for the microbial production of N2O by nitrification and denitrification in soils. However, outside the vegetation period, winter freeze/thaw events can also lead to high N2O emissions. Winter emissions constitute about 50% of total emissions in Germany. Therefore, annual datasets are a prerequisite for the development of N2O mitigation strategies in regions with winter frost. Many studies have investigated mitigation strategies for N2O emissions from agricultural soils. However, N2O release from vegetable production has seldom been studied. None of the existing trace gas measurements on intensive vegetable production is representative for the climatic conditions of Southern Germany. Due to the high fertilizer N-input (resulting in high levels of mineral N in the soil) and N-rich residues in late autumn, high annual N2O emissions are to be expected. N2O fluxes were measured from a soilcropped with lettuce and cauliflower in Southern Germany by means of the closed chamber method, at least weekly, for two years. An additional study was conducted using 15 N labeled ammonium sulfate nitrate (ASN) fertilizer and exchange of labeled and unlabeled residues to obtain information about the sources (fertilizer, residues, soil internal mineralization) of N2O emissions. Different mitigation strategies such as fertilizer reduction, addition of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) and banded fertilization were evaluated with respect to their reduction potential on an annual base. Fertilizer reduction is supposed to decrease the soil mineral N level, reducing the available substrate for N2O producing microorganisms. DMPP is a chemical compound which inhibits nitrification enzymatically. In banded fertilization, ammonium rich fertilizer is applied in a depot. This high concentration is also supposed to inhibit nitrification as it is toxic to microorganisms. N2O emissions should be firstly reduced directly by this inhibition of nitrification and secondly, by a lower nitrate content in soil resulting in less N2O release due to denitrification. A high temporal variability in N2O fluxes was observed with emission peaks after N-fertilization, after the incorporation of crop residues (especially in combination with N-fertilization), after rewetting of dry soil and after thawing of frozen soil in winter. Total cumulative annual emissions were 8.8 and 4.7 kg N2O-N ha-1 a-1 for the first and second experimental year in the conventionally (broadcast) fertilized treatment. This treatment was fertilized according to the German Target Value System. N2O emission factors were 1.6 and 0.8%. This is within the range of 0.3 - 3% which is cited in the Guidelines for the Calculation of National Greenhouse Gas Inventories proposed by the Intergovernmental Panel of Climate Change (IPCC). A positive correlation was found in both years between the mean nitrate content of the top soil and the cumulative N2O emissions of all treatments (r2=0.44 and 0.68) as well as between the N-surpluses and the cumulative N2O emissions of the different fertilizer levels during the first year (r2=0.95). Fertilizer reduction from fertilization according to good agricultural practice following the recommendations of the German Target Value System reduced annual N2O emissions by 17% in the first experimental year without yield reduction. For the second year, the reducing effect was 10%, but statistically not significant. Another fertilizer reduction of a further 20% reduced N2O emissions, but also resulted in lower lettuce yields in the first year. Therefore, an additional fertilizer reduction is not recommendable. This work provides, for the first time, annual datasets on the effect of DMPP-application on N2O emissions. Addition of DMPP significantly reduced annual N2O emissions by > 40% during both years, there was also a pronounced effect, both during the vegetation period and winter. The reason for the reducing effect in winter is not yet clear because the degradation of the active agent DMPP is temperature dependent and should take about 6 to 8 weeks under summer climatic conditions. However, we still observed significant reductions in N2O emissions in winter, about 3 months after the application. Furthermore, a reduction in CO2 release was observed indicating a possible influence on heterotrophic activities or at least on their C-turnover. Due to its high N2O mitigation potential, further investigations concerning the functional and structural changes in microbial biomass after DMPP application are needed. Banded fertilization with ASN did not result in the expected reduction in N2O emissions on an annual base. Even when exchanging the ASN fertilizer by nitrate-free ammonium sulfate, N2O emissions were not diminished. We assume that the high emissions were derived from the microbially intact surroundings of the depots, where nitrification was not inhibited and nitrate concentrations were probably very high, creating ideal conditions for denitrification. After one year, the major part of the fertilizer-15N was found in the soil. Only between 13 -15% of the fertilizer was taken up by the marketable plant parts. 1.4% of the 15N was lost as N2O-N. Total 15N recovery was 70% after one year. The losses of non-recovered N were probably caused by nitrate leaching or as gaseous compounds such as N2 or NOx. Compared to cereal production systems, the N use efficiency of this vegetable production system is much lower, even with an optimized fertilization strategy. The measurement of 15N abundances in the N2O revealed that the most significant part of the emissions (38%) was derived from the fertilizer-N which had been taken up by cauliflower residues. N2O emissions directly derived from lettuce and cauliflower fertilizer contributed 26% and 20% respectively while N2O emissions from soil internal N pools accounted for 15%. The contribution of lettuce residues was negligible due to their low amount of C and N. The reason for the high importance of the cauliflower residues was ascribed to the temporarily C-limitation of the system and the provision of electron donators by organic material. Furthermore, O2 is consumed during their degradation leading to the formation of anaerobic microsites when soil moisture is high. These sites offer ideal conditions for denitrification. Especially the combination of mineral N-fertilization and input of organic substance was found to increase N2O emissions. Therefore, the influence of a de-synchronization of the incorporation of crop residues and the mineral N-fertilization by waiting periods of up to 3 weeks was tested in an additional field trial during the cultivation of chard. The longer the waiting time between incorporation of crop residues and N-fertilizer application was, the lower were the N2O emissions. However, the effect was not statistically significant on an annual base. In an additional microcosm incubation model study, the effect of reduced and increased input as well as of different C/N-ratios of cauliflower residues was analyzed. It was shown that due to the high nitrate level in the microcosms only the amount of residue input has an effect on the N2O emissions. The N2O emissions increased with increased amount of cauliflower residues. Although the emission factors were within the range given by the IPCC, the absolute annual N2O emission was high in intensive vegetable production due to the high N-input. Further research is required in order to fully understand the effect of DMPP on the processes of N2O production in the field. Our study underlines the importance of avoiding N-surpluses and of strategies for residue management to reduce N2O emissions in intensive vegetable production.