Browsing by Subject "Landnutzung"

Now showing 1 - 16 of 16

Agent-based modeling of human-environment interactions in a smallholder agricultural system in the Atlantic Forest (Ribeira Valley, SP, Brazil)
(2021) Munari, Lucia Chamlian; Berger, Thomas
Shifting cultivation systems (SCSs) have been practiced all over the tropics for centuries as the primary subsistence strategy for smallholders. However, since the mid-20th century, SCSs have been submitted to changes, driven by a combination of geographic, economic, socio-political, and demographic factors. Consequently, land use changes lead to agricultural intensification and the replacement of more profitable and permanent practices. The implementation of forest conservation policies (FCPs) is one of the changing drivers to SCSs. They have been designed to reduce or eliminate it, criminalize traditional practices, restrict resources access, displace locals, and increase inequalities and land conflicts. In Brazil, SCSs have been practiced by smallholders and indigenous groups, including Quilombolas, descendants of African enslaved who rebelled against the Portuguese regime. After the abolition of slavery, they remained spread over the country without any state legitimation. Their recognition and rights to ancestors land were possible only in 1988, with the Brazilian Constitution. The Ribeira Valley (Southeastern Brazil) is home to dozens of Quilombos, one of the most significant Atlantic Forest remnants, and high biodiversity. Its first Quilombos were formed in the 18th century and relied on SCS to survive, relatively isolated, up to the 1950s. However, in the context of SCS changes, Quilombos are under a transitional process in different dimensions, including constraints to their traditions by FCPs, generating conflicts. Inspired by this challenging scenario, the Thesis goals are to evaluate Quilombolas’ socioeconomic conditions and the perception of FCPs implementation and integrate two modeling tools. The tools will model the impact of agricultural transitions on family wealth, income, landscape structure, and tree community β diversity and model the impact of FCPs over the equal economic and ecological dimensions. Socioeconomic data were gathered in 2017 in 14 communities through interviews of 164 farmers. Quilombolas’ perception of FCPs and constraints for agricultural practice were investigated. The modeling implementation used MPMAS (Mathematical Programming-based Multi-Agent Systems) to simulate land use change in agriculture and forestry. MPMAS was integrated (through land use maps) with a Generalized Dissimilarity Modeling tool (GDM) to predict beta diversity as a function of environmental variation. The modeling exercise was implemented for Pedro Cubas territory, a Quilombo with 52 households located in Eldorado (SP). A combination of primary and secondary data from different sources was used, including a socioeconomic census of 2014 and a collection of tree data in 2016. Five economic/political scenarios were created for comparisons, with a baseline and four different counterfactual situations, varying in market access and FCPs versions. Seven yield curve scenarios and 30 Sobol’ repetitions were combined, totalizing 1050 simulations. A tradeoff analysis was applied over the political scenarios. MPMAS sensitivity/uncertainty analyses revealed variation on staples consumptions among yield curve scenarios, the sensitivity of income to different parameters, and each income source relevance. The GDM calibration highlighted the importance of climate predictors for tree species, indicating vulnerability to potential climate variability. Results revealed that only 32% of the families were practicing SCS in 2017, but it was still relevant for food security. 83% of the interviewees were unsatisfied with the FCPs, especially the timing of issuing the licenses for SCS. The political scenarios comparison indicates that agricultural intensification caused an improvement in average income. Still, it was accompanied by economic inequality, diminished rotation of plots, lower diversity of habitats, and a less permeable landscape structure (on fallows and because of the emergence of pasture and perennial areas). GDM results showed a significant change in landscape structure/tree community for at least 10% of the territory in the last decades. Regarding FCPs implementation, scenario comparison showed that well-being conditions improved when FCPs were excluded, although more ecological impacts occur. However, such effects refer to only 2.6% of the territory where 90% is covered by mature forest, and GDM indicates that the total ß diversity would not be significantly affected. The tradeoff analysis showed that FCPs are significant for conservation in the present context when perennials and pasture areas occur. In the isolated scenario case, when SCS is the only economic activity, a combination of good well-being and conservation performances was found, suggesting it is causing even lower environmental impacts. I recommend more flexible policies for SCS implementation in the Quilombos in general, for the potential of improving well-being conditions by impacting a small share of the territories. FCPs flexibilization would be even more relevant to the communities that don’t have access to alternatives to SCS.
Assessing alternative options to improve farming systems and to promote the adoption of low-carbon agriculture in Mato Grosso, Brazil
(2018) Carauta, Marcelo; Berger, Thomas
Currently, our society faces a significant challenge to eradicate hunger and poverty while preserving natural resources and reducing greenhouse gas (GHG) emissions. In this context, Brazil plays an important role since it is one of the most significant players in global food production and hosts a variety of ecosystems and a significant share of the Earths biodiversity. The federal state of Mato Grosso (MT) is located at the most dynamic agricultural frontier in the Cerrado-Amazon transition zone and leads the national production of grain, fiber, and meat. The need to balance agricultural production and environmental protection shifted the focus of Brazilian land-use policy toward sustainable agriculture. The federal government pledged to reduce its GHG emissions and implemented policies to enforce it. Brazils low-carbon agricultural plan offers credit with low-interest rate to farmers who want to implement sustainable agriculture practices. These include the restoration of degraded pasture, adoption of integrated systems, no-till agriculture, biological nitrogen fixation, commercial forests, treatment of animal wastes, and climate change adaptation. The present thesis contributed to the CARBIOCIAL project (“Carbon-optimized land management strategies for southern Amazonia”), a German-Brazilian cooperation to investigate viable carbon-optimized land management strategies maintaining ecosystem services under changing climate conditions in the Southern Amazon. In this context, this thesis examines options to improve farming systems in MT and evaluates policy measures that could promote the adoption of low-carbon agricultural systems. The work is divided into three parts: The first part is subdivided into three chapters (chapters 1, 2 and 3) and offers an overview on land use change in Brazil and explores land use decisions of farmers in MT, where highly dynamic double-crop systems currently prevail. The second part is subdivided into two chapters (chapters 4 and 5) and is dedicated to evaluating alternative options to improve farming systems in MT. The third part is subdivided into three chapters (chapters 6, 7 and 8) and investigates factors that may influence farmers to adopt IAPS, evaluates policy measures to promote the adoption of low-carbon agricultural systems, and provides a detailed quantification of individual GHG emissions of a large variety of agricultural practices and the aggregate emissions resulting from their current use in MT. To this end, this thesis develops an Integrated Assessment (IA) approach that simulates farm-level decision-making and agricultural land use change. It introduces a novel approach to evaluate the full distribution of GHG emissions related to the agricultural land-use change in MT. Our IA approach integrates three software packages: MPMAS (Mathematical Programming-based Multi-Agent Systems), MONICA (Model for Nitrogen and Carbon in Agro-ecosystems) and CANDY (Carbon and Nitrogen Dynamics). Data to parameterize the model was gathered from several sources, such as field experiments, statistical offices, farm level surveys from private consultancies, life-cycle inventory databases, extension services, expert interviews, and literature. This thesis presents the first extensive study on crop yield response in MT by simulating yields in response to different climatic conditions, soil types, sowing dates, crop rotation schemes, fertilization amounts, and macro-regions. The simulation results show that biophysical constraints still play a crucial role on yield gaps in MT whereas socio-economic constraints have a slight yield-increasing effect. This thesis further examines alternative ways to improve the farming systems in MT by investigating the role of sunflower adoption in increasing farm income. We have found a substantial potential for sunflower cultivation in MT with positive impacts on both farm and regional level. Additionally, we identified bottlenecks for sunflower diffusion such as the distance from farm gate to processing facility. Regarding Brazilian agricultural policy, we have found that the Brazilian low-carbon agricultural program contributed to the adoption of integrated systems. However, we observed different adoption rates through macro-regions and types of integrated systems. Furthermore, our simulations additionally show that the ABC program also contributed to the adoption of less GHG-emitting practices, but its performance is subjected to agent expectations on prices and yields
Compound-specific 13C fingerprinting for sediment source allocationin intensely cultivated catchments
(2018) Brandt, Christian; Cadisch, Georg
The loss of fertile topsoil due to soil degradation and erosion not only threatens crop productivity, but also induces sedimentation of aquatic systems and leads to social-, economical-, and environmental problems in many regions of the world. The abandonment of shifting cultivation in favor of intensive mono-cultural cropping systems on sloping land accompanied by rainfall detachment and surface runoff induced soil erosion is one of the most pressing environmental and agricultural problems in the highlands of Southeast Asia. Informed soil management strategies require knowledge on the main sediment sources in a catchment. Compound-specific stable isotope (CSSI) fingerprinting, based on δ13C values of fatty acid methyl ester (FAME), allows identifying hot-spots of soil erosion, particularly with regard to assigning sediment sources to actual land uses. In this regard, we assessed the potential of the CSSI – fingerprinting approach to assign sediment sources to specific land use types in various intensely cultivated catchments. In a first step we improved the statistical procedure to identify sediment sources in a heterogeneous agricultural catchment in the mountainous northwestern region of Vietnam. In a next step we tested the CSSI-fingerprinting under different agro-ecological conditions to evaluate its global applicability, using an aligned protocol. Finally, we integrated CSSI-fingerprinting and fallout radio nuclide (FRN, 210Pbex, 137Cs) analysis to estimate past net erosion rates linked to land use types. In conclusion, the integrated Bayesian SIAR-CSSI approach was an appropriate tool to identify and assign sediment sources to actual land uses in small and heterogeneous catchments. This methodology was also suitable to identify hot-spots of soil erosion in contrasting catchments of different sizes and agro-ecological zones. Integrating CSSI-fingerprinting and fallout radio nuclide analysis to determine past sediment budgets provided insight into the impact of specific land use changes on soil retrogression and degradation. Such knowledge is of great value for informed and effective soil conservation through evidence-based land management and decision making.
Coupling pyrolysis with mid-infrared spectroscopy for the characterization of soil organic matter
(2021) Nkwain Funkuin, Yvonne; Cadisch, Georg
Soil organic matter (SOM) is known to play an important role in the global carbon cycle due to its ability to sequester atmospheric carbon dioxide (CO2) and maintenance of soil physical, chemical, and biological properties. Due to the growing need to enhance the understanding of SOM composition and dynamics as influenced by natural and anthropogenic factors, in addition to the limited ability to exist analytical techniques to provide in-depth knowledge into the constituents of SOM, a lot of research is currently focused on the development of new techniques to address the aforementioned concerns. In this study, a novel analytical technique, pyrolysis coupled with mid-infrared spectroscopy (Py-MIRS) was developed and applied to study SOM bulk chemistry in soils by measuring certain mid-infrared organic functional groups. Secondly, the developed Py-MIRS technique was applied to soil samples from different long term experiments to investigate the effects of agricultural management practices and land uses by monitoring the different functional groups. Lastly, the implications of methodological considerations of diffuse reflectance Fourier transform mid-infrared spectroscopy (DRIFTS) on specific mid-infrared functional groups and quality indices were investigated on soils from a number of long-term field experiments. Py-MIRS was developed by testing critical experimental conditions like pyrolysis temperature, heating rate, and time using a range of reference standard compounds varying in chemical and structural composition and bulk soils. As a next step in the methodological development, the suitability of the newly developed Py-MIRS was further evaluated by testing the effect of long-term management and land use on the molecular composition of SOM in bulk soils taken from long-term field experiments in Ultuna, Sweden, and Lusignan, France. The newly developed Py-MIRS technique and the evaluation of the effect of drying temperatures on peak areas obtained with DRIFTS demonstrate progress in the use of pyrolytic and spectroscopic techniques in the domain of SOM characterization. Py-MIRS revealed its potential as a rapid, reproducible, and effective technique to yield information on SOM molecular composition with minimal constraints due to mineral interferences and secondary thermal reactions. Py-MIRS also provided some insights into sustainable practices that improve SOM quality. However, the technique requires further development and testing on different clay mineralogies and land uses.
Impact of land use change on soil respiration and methane sink in tropical uplands, Southwestern China
(2020) Lang, Rong; Cadisch, Georg
Land use conversion could modulate soil CO2 emissions and the balance between CH4 oxidation and production via changing soil physical, chemical and biological properties. Large areas of natural forests have been converted to rubber plantations in Southeast Asia, but its impact on soil CO2 and CH4 fluxes has not been sufficiently understood. This study was conducted in Xishuangbanna, Southwestern China, aiming to quantify the impact of this land use change on soil CO2 and CH4 fluxes and to clarify mechanisms responsible for the differences between natural forests and rubber plantations. Dynamics of soil respiration rates in two land uses were compared, and a mixed effect model was used in studying the interference of soil moisture on estimating temperature sensitivity (Q10) of soil respiration (Chapter 2). The land use change impact on the ability of soils to function as CH4 sink was firstly assessed with surface CH4 fluxes measured by static chambers, and then assessed with gas concentration profiles determined from soil probes. Confounded controlling factors and land use effects were disentangled, and the pathway of interactions between CH4 processes and mineral nitrogen was identified (Chapter 3). The concentration gradient method and one-dimensional diffusion-oxidation model were applied to quantify the vertical distribution of CH4 uptake in soil profiles, and to separate the relative control by gas diffusivity and by methanotrophic oxidation on CH4 uptake (Chapter 4). Distinct different temporal patterns of soil respiration were observed on sites during most of the rainy season: forest maintained a high soil respiration rate, while soil respiration in rubber plantations became suppressed (by up to 69%). Forest soils thus emitted the highest amount of CO2 with an annual cumulative flux of 8.48 ± 0.71 Mg C ha-1 yr-1, compared to 6.75 ± 0.79, 5.98 ± 0.42 and 5.09 ± 0.47 Mg C ha-1 yr-1 for 22-year-old rubber, rubber-tea intercropping, and 9-year-old rubber, respectively. Adding a quadratic soil moisture term into the regression model accounted for interference of moisture effect on the effect by soil temperature, therefore, improved temperature sensitivity assessments when high soil moisture suppressed soil respiration under rubber plantations. The static chamber method showed that soils under natural forest were stronger CH4 sinks than soils under rubber plantations, with annual CH4 fluxes of -2.41 ± 0.28 kg C ha-1 yr-1 and -1.01 ± 0.23 kg C ha-1 yr-1, respectively. Water-filled pore space was the main factor explaining the differences between natural forests and rubber plantations. Although soils under rubber plantations were more clayey than soils under natural forest, this was proved not to be the decisive factor driving higher soil moisture and lower CH4 uptake in the former soils. Concentration gradients method showed that CH4 consumption in 0-5 cm soil was significantly higher in natural forests than in rubber plantations, with a mean CH4 flux of -23.8 ± 1.0 and -14.4 ± 1.0 ug C m-2 h-1 for forest and rubber plantations, respectively. The atmospheric CH4 oxidized by top 10 cm soil accounted for 93% and 99% of total consumption for forest and rubber plantations, respectively. CH4 diffusivity at four sampled depths were significantly lower in rubber plantation than in forest. This reduced CH4 diffusivity, caused by altered soil water regime, predominately explained the weakened CH4 sink in converted rubber plantations. Estimated isotopic fractionation factor for carbon due to CH4 oxidation was 1.0292 ± 0.0015 (n=12). Modeling 13CH4 distribution in soil profiles using a diffusion-oxidation model explained the observations in the dry season, but suggested CH4 production in subsoil in the rainy season. In summary, converting natural forests into rubber plantations tended to reduce soil CO2 emissions, but this conversion substantially weakened CH4 uptake by tropical upland soils. The altered soil water regime and conditions of soil aeration under converted rubber plantations appear to have a pronounced impact on processes of gaseous carbon fluxes from soils. The clarified mechanisms in this study could improve the regional budget of greenhouse gases emissions in response to land use change and climate change.
Land use change and its impact on soil properties using remote sensing, farmer decision rules and modelling in rural regions of Northern Vietnam
(2017) Nguyen, Thanh Thi; Cadisch, Georg
After the Indo China war in 1954, a dramatic rise in population in Northwest Vietnam led to an increased demand of agricultural land for food security requirements. Slash and burn systems which existed for many hundreds of years were replaced by intense cash crop systems, particularly maize production. Maize cropping was further expanded to steeper sloping areas, resulting in a risk of soil degradation. Therefore, investigating Land Use Change (LUC) and its impact on soil properties were considered in this study. The study aimed to identify LUC in 1954, 1973, the 1990s and 2007 in Chieng Khoi commune, Yen Chau district, Son La province, Vietnam using available remote sensing data. Furthermore, a detailed land use map classification method was developed using farmers’ decision rules. Based on farmers’ crop decision rules and, food requirement and population information, a simple LUC model was developed to simulate LUC annually from 1954 to 2007. Moreover, total soil nitrogen and carbon were determined under a chronosequence of intense cultivation. Thus, developing a modelling tool had the aim to assess the impacts of LUC on soil fertility at watershed level. The first case study (Chapter 3) presented the LUC assessment, using available remote sensing data combined with farmer information. Forest areas decreased from 1954 to 2007, except in the 1990s because of policies that aimed to encourage and support afforestation programmes to increase forest land. However, planted forest has since decreased again since 1999 whereas agricultural land has increased dramatically. Agricultural land expanded to both natural forest and planted forest areas until 2007 legally (with encouragement of agroforestry) and illegally thereafter (at the border between cultivated land and forest). The establishment of an artificial lake in Chieng Khoi commune opened the accessibility to forest land surrounding the lake, with a forest area of 929 ha remaining in 2007 compare to more than 2,500 ha in 1954. Paddy rice areas did not change because of their specific location (lower and flat lands), but production increased and was intensified by two cropping seasons per year due to irrigation improvements and a continuous water supply from the artificial lake. The second case study (Chapter 4) presented the development of a LUC model, using the outputs from the first case study comprising farmers’ decision rules and food requirements for an increased population. For later periods, the influence of market orientation factor was considered. The model successfully simulated the expansion of cultivation areas and replacement of forest land by agricultural land. Simulations were at accepted level of accuracy comparing actual and simulated LUC (Goodness-of-fit – GOF values greater than 0.7 and Figure of merit - FOM values greater than 50%). The third case study (Chapter 5) demonstrated an investigation of the soil fertility dynamic under intense cultivation and the development of a simple dynamic and spatially-explicit modelling tool to assess the changes in soil fertility. The Dynamic of total Carbon and Nitrogen distribution (DyCNDis) model was constructed using field data combined with literature information. The field data showed that, under a decade of maize mono cultivation in slope areas, both nitrogen and carbon were largely depleted. Furthermore, the DyCNDis model showed an acceptable level of validation (modelling efficiency – EF of 0.71 and root mean square error - RMSE of 0.42) to simulate nitrogen and carbon under intense maize cultivation at watershed level. Additionally, the model identified hotspot areas of 134 ha (18.9% of total upland cultivation areas) that are threatened by soil degradation through intense cultivation over a long-term period. In conclusion, the combination of qualitative and quantitative approaches allowed assessing impacts of LUC on environmental services such as soil fertility through the developed DyCNDis modeling tool. The combination of improved LUC analysis with a simple spatial dynamic soil fertility modeling tool may assist policy makers in developing alternative implementation strategies for local stakeholders in regions which face data limitations. The modelling tools developed in this study were able to successfully simulate LUC and to identify locations where soil conservation methods at watershed level need most urgently to be applied to avoid soil degradation. The model tools were able to simulate the trends rather than values of agricultural area expansion and reduction of soil nitrogen and carbon. The developed approaches could be linked and coupled to other modelling tools to economically consider benefits or ecological concerns toward sustainable crop production in remote and rural regions.
Linkages between poverty and sustainable agricultural and rural development in the uplands of Southeast Asia
(2008) Zeller, Manfred; Beuchelt, Tina; Fischer, Isabel; Heidhues, Franz
Most of the upland areas of Southeast Asia are characterized by insufficient infrastructure, low productivity in smallholder crop and animal production, mounting environmental problems such as soil and forest degradation and loss of biodiversity, increasing population pressure, and widespread poverty, particular in rural areas. While some upland areas in South East Asia have been experiencing considerable progress during the past twenty years, others have stagnated or even declined with respect to economic, social and environmental objectives of development. The purpose of the paper is to describe major trends regarding sustainable development in the upland areas of selected countries in South East Asia, and review explanatory approaches for the observed trends based on case studies from Cambodia, Laos, Thailand, Vietnam, and Indonesia. The conceptual framework for this paper builds on the critical triangle of sustainable rural development. Here, equity or poverty alleviation, economic growth, and the protection of the environment are the three major policy objectives. We further distinguish three explanatory approaches for land use change and agricultural and rural development. Apart from the market approach and the population approach, we suggest that future studies should focus more on governance issues as a major driving force of land use change. The governance approach appears particularly relevant for upland areas which are often politically and institutionally marginalized. The paper begins with a review of definitions of sustainability, and proceeds with a conceptual analysis of the two-way linkages between poverty and the environment, and poverty and economic growth in rural areas. This is followed by empirical findings from research on agriculture and forestry as the major land uses in upland areas of selected South East Asian countries. Based on the results of different case studies from Cambodia, Laos, Vietnam and Indonesia, we seek to contrast stories of relative success with those of failure. The paper concludes with implications for rural and agricultural development policies, and suggests future areas of research.
Linking farm economics and hydrology: Model integration for watershed-level irrigation management applied to Chile
(2010) Arnold, Thorsten; Berger, Thomas
As largest user of fresh water, the agricultural sector must resolve conflict of objectives ranging from economic goals of farmers to societal and environmental targets. Research must deliver tools to manage these objectives simultaneously. Single disciplines have resolved numerous problems with disciplinary solutions. However, problems emerging from interactions and feedbacks between disciplines can only be assessed with interdisciplinary tools and managed by institutions that coordinate across departments. Such complex problems are becoming an epochal task for Natural Resource Management (NRM). A number of modeling tools exist for irrigation management at watershed level that quantify biophysical processes and water quality. Simultaneously, agricultural economics developed production planning methods for allocating water resources optimally. However, integrated planning support tools are not available that take into account both domains and their interactions. Within a larger research project, it was the objective of this Ph.D. project to develop and test methods that integrate two complex modelling softwares for irrigation management. The distributed runoff model WaSiM-ETH quantifies water flows and evapotranspiration. The dynamic land use model MP-MAS is a multi-agent system in which farmers use economic reasoning to derive cropping decisions under given environmental conditions. Furthermore, the MP-MAS software contains the bucket model EDIC, which parameterizes the distribution of water from rivers to individual farmers through the canal system. Finally, the MP-MAS software was extended with a crop yield model with complementary irrigation. Model integration is understood as service provided within a research context. This context is defined by the study region, the project setting and by the strategic decisions within the research project - such as the choice of partner institutions and disciplines. Within the Maule River watershed in Chile (Linares Province, Region VII), the project ?Integrating Governance and Modeling? assessed the use of water in agriculture. Empirical research questions as well as modeling software were also part of this research context. Integration requires the conceptual, the technical and the procedural level. Conceptual integration describes processes and interactions between farmers, the canal system as distribution infrastructure and the natural system. It also describes how farmers plan and produce within this environment. Here, scale-dependent processes like irrigation efficiency or access to water by individuals were scrutinized. Technical integration is the implementation of the conceptual system into source code, e.g. by adapting legacy software, and by creating a software layer for hierarchical coupling of all software components. Procedural integration is the calibration, analysis, error eradication and validation of these models within the research context. Calibration and analysis of integrated model components is a step-by-step procedure. For all relevant processes and interactions, empirical data was first compiled and cross-evaluated. Then, standalone model components were calibrated so that interactions were parameterized as boundary conditions that are consistent across all disciplines. Empirical data pinpointed conceptual inconsistencies in the description of interactions, and standalone models were improved together with project partners. Ultimately, model components were coupled in such ways that interactions can be analyzed dynamically at minimum model- and software complexity. The calibration process along transdisciplinary cause-effect-chains resulted in the improvement of disciplinary models and model results. For example, the relevance of access to water beyond legalized water rights became apparent when empirical data and models were combined. Also, the calibration of the EDIC model required consistent use of data from all four disciplines and improved the calibration of the MP-MAS model. For the WaSiM-ETH model, an irrigation module was developed that is consistent across scales and reflects the needs of extension workers. Finally, model integration and coupling is discussed as research process. The process of calibrating a model with four components is not only a technical challenge for modellers and data management, but also a procedural challenge with regards to cooperation beyond disciplinary institutions and cultures. The structure of the integration process should be robust against errors and equally facilitate knowledge transfer between disciplines, iterative calibration across disciplines. Success factors are suggested to reduce transaction cost during the integration process.
Mitigate habitat degradation in the semiarid Brazil : potential and limitation of the endemic tree Spondias tuberosa Arruda
(2017) Mertens, Jan Heiko; Sauerborn, Joachim
Semiarid regions cover 15 % of the global land mass and are inhabited by approximately one billion people. Due to the strong rural character of these regions the well-being of 13 % of the world’s population relying directly or indirectly on their ecosystem services. One of the most densely populated semiarid region is the Caatinga biome, that is located in the Brazilian Northeast. Its climate is hot semiarid (BSh) with little, erratic, and seasonal precipitation, ranging from 250 to 900 mm per year. The average annual temperatures range from 23°C to 27°C. An evapotranspiration above 2000 mm per year results in a negative water balance during 7 to 11 months. The deciduous natural Caatinga vegetation ranges from tropical dry forest to open shrubby vegetation, with a seasonal herbaceous layer. Loss of its natural vegetation due to wood extraction, pasturing, and inappropriate land-use led to habitat degradation in up to 80 % of the area of the Caatinga biome. A degraded habitat jeopardizes the ecosystem services of the biome and poses a direct threat to its dwellers. In order to mitigate further habitat degradation an alternative land-use strategy is necessary to substitute or cut back prevailing land-use. The agro-industrial utilization of the fructiferous multipurpose tree Spondias tuberosa Arruda (Anacardiaceae), endemic to the Caatinga, has the potential to be a viable alternative to current irrigation farming and extensive animal husbandry. The current utilization of S. tuberosa is limited to extractivism of its fruits that lacks sustainability and appears to be a finite resource. The natural population of S. tuberosa presents a weakening natural regeneration with a resultant over aged S. tuberosa population. Poor natural regeneration results from a multifactorial problem. At this juncture, S. tuberosa is not considered endangered based on the criteria of the International Union for Conservation of Nature, due to lacking information for a Red List of Threatened Species threat assessment. However, the combination of expected changing environmental conditions within the Caatinga and restricted natural regeneration of S. tuberosa, both discussed in literature, provides a strong evidence, that the S. tuberosa faces a high risk to become extinct. This work aims to provide a first basis for a scientifically-backed, extensive cropping system for S. tuberosa on disturbed Caatinga sites meliorated by the use of biochar, clay substrate, and goat manure. The effect of biochar, clay substrate, and goat manure with or without additional mineral fertilization as soil conditioner in planting holes were tested in a 23-months field experiment in a marginal Arenosol. Further, it was studied, whether changed soil physical conditions support establishment and development of one-year-old S. tuberosa seedlings. At given application rates neither biochar nor clay substrate significantly affected soil physical parameters of the experimental soil. The application rate of 10 % v/v clay substrate, chosen from literature, seems to be too little to be affective on the experimental Arenosol, that was poor in fine particles (< 0.02 mm). The utilized biochar were proven hydrophobic and presumingly little porous duo to a low pyrolysis temperature. Both combined could explain the absence of a significant biochar‑mediated change of soil physical parameters. Goat manure significantly increased total porosity, and significantly reduced soil bulk density. The water content at permanent wilting point, and volumetric water content within the planting holes during the experiment were significantly increased owing to melioration with goat manure. Due to a strong correlation (R2 = 0.75) of water content at field capacity and water content at permanent wilting point, the available water capacity, an important target parameter for plant production, remained unchanged. Neither stem growth nor seedling survival was significantly affected by initial nutrient supplies or melioration. Conversely, fine root growth and root tuber growth were significantly affected by melioration. Goat manure in the planting holes led to significantly reduced fine root dry matter. Since fine root dry matter showed a weak but significant negative correlation with soil water content, the fine root reduction was evidently caused by increased soil water content resulting from goat manure application. The goat manure application also affected tuber growth significantly, and led to larger tubers. In contrast to the fine roots, root tuber growth did not respond to soil water content but showed a significant correlation with soil bulk density and total porosity. Reduced soil bulk density and increased soil porosity after goat manure addition application led to higher tuber volume.
Modeling the influence of coastal vegetation on the 2004 tsunami wave impact
(2014) Laso Bayas, Juan Carlos; Cadisch, Georg
A tsunami causes several effects once it reaches inland. Infrastructure damage and casualties are two of its most severe consequences being mostly determined by seaquake intensity and offshore properties. Nevertheless, once on land, the energy of the wave is attenuated by gravity (elevation) and friction (land cover). Despite being promoted as ‘bio-shields’ against wave impact, proposed tree-belt effects lacked quantitative evidence of their performance in such extreme events, and have been criticized for creating a false sense of security. The current study analyzed some of the land uses in sites affected by the 2004 tsunami event, especially in coastal areas close to the coast of Indonesia, more specifically on the west coast of Aceh, Sumatra as well as on the Seychelles. Using transects perpendicular to the coast, the influence of coastal vegetation on the impact of the 2004 tsunami, particularly cultivated trees, was modeled. A spatial statistical model using a land cover roughness coefficient to account for the resistance offered by different land uses to the wave advance was developed. The coefficient was built using land cover maps, land use characteristics (stem diameter, height, and planting density), as well as a literature review. The spatial generalized linear mixed models used showed that while distance to coast was the dominant determinant of impact (casualties and infrastructure damage), the existing coastal vegetation in front of settlements also significantly reduced casualties, in the case of Aceh, by an average of 5%. Despite this positive effect of coastal vegetation in front of a settlement, it was also found that dense vegetation behind villages endangered human lives and increased structural damage in the same case, most likely due to debris carried by the backwash. The models initially developed in Aceh were adapted and tested for the effects that the same tsunami event caused in the Seychelles, where the intensity of the event was a tenth of that in Aceh. These new models suggested no direct effect of coastal vegetation, but they indicated that vegetation maintained dunes decreased the probability of structural damage. Additionally, using satellite imagery with higher resolution than that of the first study and/or from different years before the tsunami, corresponding land roughness coefficients were developed and tested with the existing models. The new models showed no signs of further increase of goodness of fit (AIC). Nevertheless, weather conditions at the acquisition dates as well as coverage and lack of image availability diminished the predictive power of these models. Overall, more than advocating for or against tree belts, a sustainable and effective coastal risk management should be promoted. This planning should acknowledge the location (relative to the sea) of settlements as the most important factor for future coastal arrangements. Nevertheless, it should also consider the possible direct and indirect roles of coastal vegetation, determined by its spatial arrangement as shown in the study models. Sustainability of these measures would only occur when coastal vegetation is regarded as a livelihood provider rather than just as a bio-shield. Practical examples could include, e.g. rubber plantations or home gardens in front of settlements, while leaving escape routes or grasslands and coconut plantations behind these. Therefore, the enforcement of educational programs, the setup and maintenance of effective warning systems and the adequate spatial allocation of coastal vegetation bringing tangible short and mid term benefits for local communities, as well as its adaption to local customs should be considered.
Rainforestation farming on Leyte island, Philippines - aspects of soil fertility and carbon sequestration potential
(2007) Marohn, Carsten; Sauerborn, Joachim
This study aimed at investigating rainforestation systems in Leyte, Philippines, under different aspects: Characterisation of typical soils in Leyte with respect to physical, chemical and biological parameters relevant for tree growth, possible contributions of rainforestation to restoring soil fertility, performance of a recently planted rainforestation system under different microclimatic and soil conditions, potential of the rainforestation approach for projects under the umbrella of the Clean Development Mechanism (CDM). Soils in Leyte can be grouped into a volcanic and a calcareous category. The latter were formed on coralline limestone and are high in pH and Ca2+ and Mg2+. Contents of organic matter are high while concentrations of plant available PBray are low. Volcanic soils are characterised by low pH and CEC as well as extremely low PBray contents. Organic matter levels are below those of the calcareous soils but still moderate. In any analysed soil, N would not limit tree growth. Pore volume and water infiltration were propitious for all sites, which is relevant in the context of erosion. For calcareous soils, drought and reduced rootability due to clayey subsoil posed the most relevant constraints. The frequently claimed role of rainforestation in the rehabilitation of degraded soils was assessed in a paired plot approach. Chemical and biological soil parameters under 10 year old rainforestation were contrasted with adjacent fallow or Gmelina sp. Clear tendencies across all seven sampled sites were lower available Mg2+ and pH under rainforestation. Other differences were less distinct. Generally, a depletion of soil reserves e.g. in basic cations can be explained by uptake into the plants. A feed-back of these elements to the topsoil via leaf litter, however, could be observed only for available P. In conclusion, plant uptake of single elements can reach orders of magnitudethat reduce soil stocks. At the same time, generally lower pH under rainforestation may have contributed to elevated losses, especially of basic cations. A general improvement of the sampled soils in terms of chemical or biological characteristics through rainforestation could not be observed. To evaluate plant performance six timber and four fruit species, most native, were interplanted on a 1ha plot. Rainforestation, commonly understood as high-density closed canopy system was modified to a less dense 5x5m grid, interplanted with Musa textilis. The plot varied strongly on a small scale due to heterogeneous canopy closure and relief. Methodologically, the entire area was divided into 10 subplots in representative positions to be sampled. Soil physical and chemical properties, microbial activity, PAR and root length density were determined and correlated to plant survival and growth at consecutive inventories. For Musa textilis, the most sensitive species, which was used as an indicator, logistic regressions were calculated to determine the influence of all relevant parameters on survival rates. The most important predictors for survival were organic matter contents, parameters related to biological activity and leaf litter production, which resembled canopy closure and thus indirectly light intensity and soil moisture. To assess growth, multiple regressions were formulated for biomass at five inventories. Corg and NLOM were the most relevant variables determining the regressions used for biomass and growth of abaca. Assessing the potential of rainforestation for Clean Development Mechanism (CDM) measures, amounts of sequestered CO2 during 10 and 20 years, respectively, were estimated under different management options using the WaNuLCAS model. Despite all given uncertainty associated with modelling, one very obvious finding was the dominant role of soil carbon for the plot balance: Appropriate soil management, especially during land preparation (e.g. clearing vs. enrichment planting) is of paramount importance. Looking at the modelled contribution of various tree species to the carbon balance, Musa textilis had a significant influence only during the very first years; later on, the principal share of carbon was bound in the tree component. Here, exotic Gmelina arborea built up biomass more quickly than a rainforestation plot composed of native Shorea contorta and Durio zibethinus, but was then overtaken. In absolute quantities of CO2 sequestration, magnitudes matched inventory and modelled data given in various literature sources for Leyte and the Philippines. Relative to earlier inventory data from two rainforestation sites, modelled values overestimated growth.
Sediment, carbon and nitrogen capture in mountainous irrigated rice systems
(2016) Slaets, Johanna I. F.; Cadisch, Georg
Anthropogenic influences have caused landscapes to change worldwide in the last decades, and changes have been particularly intense in montane Southeast Asia. Traditional swiddening cropping systems with low environmental impacts have been largely replaced by forms of permanent upland cultivation, often with maize. The associated soil fertility loss at the plot scale is well documented. In valley bottoms of these areas, paddies have been cultivated for centuries, and are considered some of the most sustainable production systems in the world – in part maintained by the influx of fertile sediments through irrigation. Altered cropping patterns on the slopes therefore also have potential repercussions on rice production, and hence on food security, but the consequences of shifted sediment and nutrient redistribution at the landscape scale are not well understood. In order to assess these effects, methodologies were developed in this thesis that enable low-cost, continuous monitoring of sediment and nutrient transport in irrigated watersheds (Chapter 2), as well as quantification of the uncertainty on constituent loads (Chapter 3). These methods are applied in a case study to determine sediment, organic carbon and nitrogen trap efficiency of paddy rice fields in a mountainous catchment in Vietnam (Chapters 4 and 5). The upland area had an average erosion rate of 7.5 Mg ha-1 a-1. Sediment inputs to the paddy area consisted of 64 Mg ha-1 a-1, of which irrigation water provided 75% and the remainder came from erosion during rainfall events. Erosion contributed one third of the sand inputs, while sediments from irrigation water were predominantly silty, demonstrating the protective effect of the reservoir which buffered the coarse, unfertile material. Almost half of the total sediment inputs were trapped in the rice area. As all of the sand inputs remained in the rice fields, the upland-lowland linkages could entail a long-term change in topsoil fertility and eventually a rice yield loss. Quantification of nutrient re-allocation in Chapter 5 showed that irrigation was even more important as a driver of sediment-associated organic carbon and nitrogen inputs into the rice fields, contributing 90% of carbon and virtually all nitrogen. Direct contributions from erosion to the nutrient status of the paddies were negligible, again underscoring the protective function of the surface reservoir in buffering irrigated areas from unfertile sediment inputs. 88% of the sediment-associated organic carbon and 93% of the nitrogen were captured by the rice fields. Irrigation water additionally brought in dissolved nitrogen, resulting in a total nitrogen input of 1.11 Mg ha 1 a-1. Of this amount, 24% was determined to be in the plant-available forms of ammonium and nitrate, a contribution equivalent to 66% of the recommended nitrogen application via chemical fertilizer. The dependence of paddy soil fertility on agricultural practices in the uplands illustrates the vulnerability of irrigated rice to unsustainable land use in the surrounding landscape. Unfortunately, alternatives for upland land use that are not detrimental to soil quality are hard to come by, due to the economic reality of high maize prices on the world market. Conservation measures and agroforestry systems offer potential, but without some form of payment for environmental services, adoption rates remain low. Finding sustainable solutions is especially urgent as climate change is likely to increase the number of extreme rainfall events and hence intensify the redistribution processes already taking place. In this light, the role of trapping elements in landscapes such as paddy fields and surface reservoirs becomes more important as well. As these features are widely spread throughout tropical landscapes, their role in global sediment and nutrient cycles must be taken into account. The methodologies developed in this thesis, for sediment and nutrient transport monitoring and for uncertainty assessment, can aid in closing the data gap that currently hinders a reliable assessment of the consequences of anthropogenic and climate change, both on food security and on environmental impacts, locally, regionally and globally.
Sensitivity of land-atmosphere coupling strength in dependence of land cover and atmospheric thermodynamics over Europe
(2023) Jach, Lisa; Wulfmeyer, Volker
Biogeophysical feedbacks between the land surface and the atmosphere have been identified to heavily control the climate system. Land-atmosphere (L-A) coupling strength is a concept to quantify the feedback processes. However, the quantification is still subject to uncertainties, in particular, in the context of land surface influences on local convective precipitation. On the one hand, feedback processes are the result of a chain of complex interactions between various components in the L-A system all exhibiting spatiotemporal variability. On the other hand, L-A coupling strength is not a directly measurable quantity. It can be assessed with different scientific approaches, which makes the quantification dependent on the methodology and the availability of suitable data sets. The aim of this doctoral thesis is to investigate the impact of changes in the vegetation cover and the atmospheric thermodynamic conditions on the long-term coupling signal between the land surface and the triggering of deep moist convection during the European summer. The ‘convective triggering potential – low-level humidity index’ framework, which is a commonly used L-A coupling metric, classifies a day in favor for L-A coupling or not, based on the prevailing thermodynamic conditions in the atmosphere. The daily classifications are used to measure the frequency of days with favorable conditions during the study period, and to identify regions with high frequencies of favorable conditions as coupling hot spots. The framework is applied to model output from regional climate model (RCM) simulations with WRF-NoahMP with diverging land cover conducted over the historical period 1986-2015 for the Euro-CORDEX domain. Impacts of changes in vegetation cover are analyzed by comparing the L-A coupling strength from two sensitivity experiments with idealized extreme land use and land cover changes (LULCCs) against a simulation with realistic land cover. A posteriori modifications to the temperature and moisture output fields of the simulation with realistic land cover were implemented to analyze impacts of systematic changes in the atmospheric thermodynamic conditions. A potential coupling hot spot with predominantly positive feedbacks was identified over Eastern Europe. In Southern Europe and Europe’s coastal areas, the coupling is regularly inhibited by very dry, very wet or stable conditions in the atmosphere. The location of the hot spot appeared insensitive to LULCCs and changes in the thermodynamic conditions. None of the sensitivity tests within a realistic range of temperature and moisture modifications for a recent climate period, led to a disappearance of the hot spot or to overcome the causes for inhibiting coupling in the respective areas in summer. Nevertheless, the experiments demonstrated also considerable variance of the coupling strength within the hot spot region. LULCCs changed the turbulent heat fluxes from the land surface, and thus the atmospheric boundary layer (ABL) heating and moistening. This impacted the boundary layer development of each day. It also caused changes in the average thermodynamic characteristics during the study period, which changed the frequency of favorable pre-conditioning for convection triggering and enhanced the variance in the coupling strength in the hot spot. Both effects were identified to influence the land surface control on the occurrence of convective precipitation. Furthermore, the sensitivity tests with a posteriori modifications revealed uncertainties in the predominant atmospheric response to differently wet surfaces around the Black Sea, shown by a disagreement in the predominant coupling pathway between the modification cases. The findings further indicate uncertainty in whether the hot spot expands over Central Europe, as the feedback signal was sensitive to changes in temperature and moisture. Additionally, the model has a warm and dry bias in this area, which suggests an overestimation of the humidity deficit. The large humidity deficit, in turn, was the inhibiting factor for a high frequency of occurrence of favorable pre-conditions for deep moist convection. The analyses reveal a sensitivity of the L-A coupling strength and atmospheric response to the prevailing land surface and atmospheric conditions in the hot spot. This highlights the need to consider both the land surface state and its impact on L-A coupling strength with respect to predictions of convective precipitation events in strongly coupled regions (and periods). Given that L-A coupling provides predictive skill for climate projections and seasonal forecasts, improved understanding about causes of variability in L-A coupling strength is crucial for improvements therein.
Simulating the impact of land use change and climate change on the supply of ecosystem services in a rubber-dominated watershed in Southwestern China
(2020) Thellmann, Kevin; Asch, Folkard
This cumulative PhD thesis investigates the expansion of rubber (Hevea brasiliensis Müll. Arg.) plantations and the ensuing multiple impacts on biodiversity and the supply of ecosystem services (ESS) in a mountainous watershed in Xishuangbanna Prefecture, Southwestern China. In recent decades, the study area, the Nabanhe Reserve, saw the expansion of rubber plantations and the loss of extensive forest areas, which led to a substantial decline in ESS. Workshops with regional stakeholders resulted in the development of three future land use scenarios for Nabanhe Reserve (2015 – 2040), varying in their degree of rubber expansions, management options and reforestations efforts. In the first study, the InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) modeling framework was used to analyze the impact of these rubber expansion scenarios on selected ESS: sediment retention, water yield, habitat quality, and carbon sequestration. In addition, a model for assessing potential rubber yields was developed and implemented in ArcGIS. The analysis also included different statistical weighting methods to include rankings for the preference of ESS from three contrasting stakeholder groups (prefecture administration, tourists, off-site citizens). The study concludes that the integrated ESS indices would be overestimated without the inclusion of the stakeholder groups. The second study introduced a new method to identify potential tipping points in the supply of ESS. Here, time-series data derived from InVEST have been combined with a sequential, data-driven algorithm (R-method) to identify potential tipping points in the supply of ESS within two contrasting scenarios of rubber expansion in Nabanhe Reserve. The tipping point analysis included hydrological, agronomical, and climate-regulation ESS, as well as multiple facets of biodiversity. The model results showed regime shifts indicating potential tipping points, which were linked to abrupt changes in rubber yields, in both scenarios and at varying spatial scales. The study concludes that sophisticated land use planning may provide benefits in the supply of ESS at watershed scale, but that potential trade-offs at sub-watershed scales should not be neglected. The third study focused on modeling hydrological ESS (water yield and sediment export) in Nabanhe Reserve under multiple scenarios of land use and climate change in order to assess how both drivers influence the supply of these ESS. Three rubber expansion scenarios were analyzed in combination with multiple climate change scenarios using the InVEST modeling framework. Simulation results showed that the effect of land use and land management decisions on water yield in Nabanhe Reserve are relatively minor (4% difference in water yield between land use scenarios), when compared to the effects that future climate change will exert on water yield (up to 15% increase or 13% decrease in water yield compared to the baseline climate). Changes in sediment export were more sensitive to land use change (15% increase or 64% decrease) in comparison to the effects of climate change (up to 10% increase). The study concludes that in the future, particularly dry years may have a more pronounced effect on the water balance in Nabanhe Reserve as the higher potential evapotranspiration increases the probability for periods of water scarcity, especially in the dry season. In conclusion, the studies showed detrimental consequences induced by rubber expansions for all assessed ESS, with the exception of rubber yields. Further continuing the trend of rubber expansions in the study area is not the best option in terms of integrated ESS supply on a landscape scale. Land use planning alternatives, such as rubber expansions restricted to suitable areas only, in combination with reforestation efforts at less suitable locations, may be used to keep crucial environmental functions intact. Policy regulations at the local level, if properly assessed with spatial models and integrated stakeholder feedback, have the potential to buffer the typical trade-off between agricultural intensification and environmental protection. The implementation of these regulations might still pose a considerable challenge. The methods introduced in this Dissertation can easily be transferred to regions facing comparable land use situations, as InVEST and a large amount of the utilized spatial datasets are freely available.
Simulating the impact of land use change on ecosystem functions in data-limited watersheds of Mountainous Mainland Southeast Asia
(2015) Lippe, Melvin; Cadisch, Georg
The presented PhD thesis deals with the development of new modelling approaches and application procedures to simulate the impact of land use change (LUC) on soil fertility, carbon sequestration and mitigation of soil erosion and sediment deposition under data-limited conditions, using three mountainous watersheds in Northern Thailand, Northern and North-western Vietnam as case study areas. The first study investigated if qualitative datasets derived during participatory processes can be used to parameterize the spatially-explicit, soil fertility-driven FALLOW (Forest, Agroforest, Low-value Landscape Or Wasteland?) model. Participatory evaluations with different stakeholder groups were conducted in a case study village of Northwest Vietnam to generate model input datasets. A local colour-based soil quality classification system was successfully integrated into the FALLOW soil module to test scenarios how current or improved crop management would impact the evolution of upland soil fertility levels. The scenario analysis suggested a masking effect of ongoing soil fertility decline by using fertilizers and hybrid crop varieties, indicating a resource overuse that becomes increasingly irreversible without external interventions. Simulations further suggested that the success rate of improved cropping management methods becomes less effective with increasing soil degradation levels and cannot fully restore initial soil fertility. The second case study examined the effects of LUC on the provisioning of long-term carbon sinks illustrated for a case study watershed in Northern Thailand. Based on land use history data, participatory appraisals and expert interviews, a scenario analysis was conducted with the Dyna-CLUE (Dynamic and Conversion of Land use Effects) model to simulate different LUC trajectories in 2009 to 2029. The scenario analysis demonstrated a strong influence of external factors such as cash crop demands and nature conservation strategies on the spatial evolution of land use patterns at watershed-scale. Coupling scenario-specific LUC maps with a carbon accounting procedure further revealed that depending on employed time-averaged input datasets, up to 1.7 Gg above-ground carbon (AGC) could be built-up by increasing reforestation or orchard areas until 2029. In contrast, a loss of 0.4 Gg in AGC stocks would occur, if current LUC trends would be continued until 2029. Coupled model computations further revealed that the uncertainty of estimated AGC stocks is larger than the expected LUC scenario effects as a function of employed AGC input dataset. The third case study examined the impact of land use change on soil erosion and sediment deposition patterns in a small watershed of mountainous Northern Vietnam using a newly developed dynamic and spatially-explicit erosion and sediment deposition model (ERODEP), which was further coupled with the LUCIA (Land Use Change Impact Assessment) model building on its hydrological and vegetation growth routines. Employing available field datasets for a period of four years, ERODEP-LUCIA simulated reasonably well soil erosion and sediment deposition patterns following the annual variations in land use and rainfall regimes. Output validation (i.e. Modelling Efficiency=EF) revealed satisfying to good simulation results, i.e. plot-scale soil loss under upland swiddening (EF: 0.60-0.86) and sediment delivery rates in monitored streamflow (EF: 0.44-0.93). Cumulative sediment deposition patterns in lowland paddy fields were simulated fairly well (EF: 0.66), but showed limitations in adequately predicting silt fractions along a spatial gradient in a lowland monitoring site. In conclusion, data-limited conditions are a common feature of many tropical environments such as Northern Thailand and Northern/North-western Vietnam. Environmental modellers, decision makers and stakeholders have to be aware of the trade-offs between model complexity, input demands, and output reliability. It is not necessarily the challenge of data-limitations, but rather the decision from the very beginning if the aim is to develop a new model tool or to use existing model structures to support environmental decision making. Future modelling-based investigations in data-limited areas should combine scientifically-based approaches with participatory procedures, because scientific assessment can support environmental policy making, but stakeholders’ decision will finally determine the provisioning of ecosystem functions in the long run. A generic assessment framework is proposed as synthesis of this study to employ dynamic and spatially-explicit models to examine the impact of LUC on ecosystem functions. The application of such a generic framework is especially useful in data-limited environments such as Mountainous Mainland Southeast Asia, as it not only provides guidance during the modelling process, but also supports the prioritisation of input data demands and reduces fieldwork needs to a minimum.
Spatial and temporal variations of microorganisms in grassland soils : influences of land-use intensity, plants and soil properties
(2019) Boeddinghaus, Runa S.; Kandeler, Ellen
Grassland ecosystems provide a wide range of services to human societies (Allan et al., 2015) and plants and soil microorganisms have been identified as key drivers of ecosystem functioning (Soliveres et al., 2016). Therefore, understanding soil microbial distributions and processes in agricultural grassland soils is crucial for characterizing these ecosystems and for predicting how they may shift in a changing environment. Yet we are only beginning to understand these complex ecosystems, which account for about 26% of the world’s terrestrial surface (FAOSTATS, 2018), making it especially urgent to gain better insights into the effects of land-use intensity on soil microbial properties and plant-microbe interactions. This thesis was conducted to evaluate the impact land-use intensity has on soil microbial biogeography of grasslands with respect to both spatial patterns and temporal changes in soil microbial abundance, function (in terms of enzyme activities), and community composition. It also investigated the relationships between plants and the spatial and temporal distributions of soil microorganisms. Thereby both, land-use intensity effects and plant-microbe interactions, were assessed in light of ecological niche and neutral theory. This thesis is based on three observational studies conducted on from one to 150 continuously farmed, un-manipulated grassland sites in three regions of Germany within the Biodiversity Exploratories project (DFG priority program 1374). The first study assessed the effects of land-use intensity and physico-chemical soil properties on the spatial biogeography of soil microbial abundance and function in 18 grasslands sites from two of the three regions, sampled at one time point. The second study analyzed spatial and temporal distributions of alpha- and beta-diversity of arbuscular mycorrhizal fungi in a low land-use intensity grassland with six sampling time points across one season. The third study investigated both legacy and short-term change effects of land-use intensity, soil physico-chemical properties, plant functional traits, and plant biomass properties on temporal changes in soil microbial abundance, function, and community composition in 150 grassland sites across three regions, with particular regard to direct and indirect land-use intensity effects. Although the three studies used different approaches and assessed different soil microbial properties, general patterns were detectable. Abiotic soil properties, namely pH, nitrogen content, texture, and bulk density played fundamental roles for spatial and temporal microbial biogeography. Since these factors were specific and unique for each investigated site, they formed the background based on which other processes occurred. In addition to abiotic soil properties, impacts of land-use intensity and plants were detected, though to various degrees in the three studies. Land-use intensity played a much smaller role than anticipated in the first and third study. No influence on the spatial distribution of soil microbial abundance and function could be detected in the first study. In the third study, short-term changes in and legacy effects of land-use intensity played a minor role with respect to short-term changes in soil microbial abundance, function, and community composition. Where detected, changes in land-use intensity had a direct and negative effect on soil microbial properties in structural equation modelling; i.e., increases in land-use intensity reduced, e.g., soil microbial enzyme activities, while legacy effects of land-use intensity were shown to act both directly and indirectly on soil microbial properties. Thereby indirect legacy effects were mediated via plant functional traits. Only one of the three studies detected minor plant diversity effects on soil microbial properties. Instead, functional properties of the plant communities, i.e., plant functional traits, biomass, and nutritional quality, were significantly related to spatial and temporal distributions of soil microorganisms. Finally, the findings of the three studies suggest that processes related to niche and neutral theory both drive spatial and temporal patterns of soil microbial properties at the investigated plot scale (up to 50 m × 50 m). This thesis concluded that in order to gain deeper insights into the complex functions and processes occurring in grassland ecosystems, a multidisciplinary approach investigating fundamental physico-chemical site characteristics, microbial soil properties, and plants is necessary. The results of the thesis suggest that focus be turned to functional properties of plant and microbial communities, as they are closely intermingled, provide more detailed insights into plant-microbe interactions, and are able to reflect effects of human impacts on grassland soils better than diversity measures.