Browsing by Subject "Thailand"

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Assessment of hydrology and dynamics of pesticides in a tropical headwater catchment in Northern Thailand
(2013) Hugenschmidt, Cindy; Streck, Thilo
The dissertation deals with assessment of hydrology and the dynamics of pesticides in a tropical headwater catchment in northern Thailand. Rainfall and runoff characteristics are recorded and investigated, pesticide dynamics during single events are monitored and studied. Finally, a hydrological model is applied.
Collaborative water governance in Thailand : much ado about nothing?
(2015) Kanjina, Sukit; Hoffmann, Volker
The river basin committee (RBC) framework was first introduced in Thailand in 2002, and the current one adopted in 2007 has been implemented in all 25 river basins located in the country ever since. By all accounts, the RBC framework is innovative as far as Thailand’s administrative system and water resource sector are concerned. It was only recently that the former started to promote non-public sector participation, and the underlying legal framework expressly requires that representatives of the non-public sector, such as water user organizations and local experts, be included in the RBC together with those representing the public agencies concerned. The latter envisions the RBC as a new mechanism for managing water resources by using a river basin as a managerial unit. Based on the RBC framework’s prescription, it can be seen that Thailand is moving toward collaborative water governance, where both public and non-public sector representatives take part in decision making on water resource-related issues in their respective river basin. This study empirically examines the implementation process and outcomes of the RBC framework by using the Ping RBC arrangement as an illustrative case. It aims specifically to explore the formation and management of the RBC, its collaborative processes and participation, and the outcomes it generates. To this end, semi-structured interviews were conducted with key informants such as the officials responsible from Water Resources Regional Office 1 (WRO 1), and Ping RBC members; and an informal interview was applied as well with some DWR officials. In addition, relevant activities were observed through non-participant observation, while related documentary data, e.g. documents on the RBC framework, also were collected. The data gathered were analyzed by means of qualitative content analysis. It was found overall that the Ping RBC framework was established by following relevant directives. Ping RBC members include representatives from the public sector such as the Royal Irrigation Department (RID) and Department of Water Resources (DWR), as well as the provincial governors concerned and representatives from the non-public sector, including water user organizations (agricultural, industrial, commercial, service, and tourism sectors), local government organizations (LGOs), and the expert group; while WRO 1 serves as the secretariat. In addition, other governing bodies were established as well, including one river basin sub-committee, five provincial river basin working groups, and 20 sub-river basin working groups who, similar to Ping RBC members, represented both the public and non-public sector at the river basin, provincial, and sub-river basin level. It was discovered that regarding RBC management the Ping RBC and its governing bodies were governed by the lead organization-governed form, where WRO 1 played the leading role and left no room for involvement from other members. For example, it called the meetings and prepared their agenda. Indeed, meetings were the only activity organized for these river basin governing bodies and they were infrequent (e.g. twice per year for the Ping RBC). Furthermore, they were organized with a formal format, where the officer responsible normally provided information to the meeting, with virtually no deliberation or discussion. With these meetings being the only activity where members of the river basin governing bodies could get together, it was apparent that face-to-face dialogue, which is a crucial element in leading to others elements in a collaborative process, such as trust and shared understanding, was simply non-existent. Interaction between the secretariat and members of the river basin governing bodies, as well as among the members also failed to occur. Participation in the Ping RBC setup involved just information sharing, as members of the Ping RBC and its governing bodies were provided with only data on, for example, drought and flood situations. The governing bodies of the Ping River Basin, especially the Ping RBC, took part in approving river basin management and development frameworks as well as annual river basin management and development plans. However, their approval was unnecessary because the frameworks and annual plans in question were a collection of project plans gathered from the public agencies concerned and LGOs located in the river basin. They were prepared based on relevant policies and directives, with no need for approval from the Ping RBC setup before submission for national budget allocation. Since the frameworks and annual plans were the only outputs produced, it was therefore apparent that the Ping RBC framework performed virtually no functions to fulfill its mandates such as a water resource management plan, water user priority or water allocation. Evidently, the Ping RBC framework is an ineffective mechanism that is characterized by lack of collaboration, participation and outcomes, which have impacts on water resource management in the river basin. A similar result can be expected from the other 24 RBCs operating under the same administrative system and legal framework. Therefore, Thailand is still far from achieving collaborative governance in its water resource sector. Clearly, this unsuccessful RBC framework was influenced by the Thai administrative system; for instance, the public agencies involved have to follow their own policies and directives, thereby failing to make the RBC framework their top priority and only passively participating in the setup. However, the underlying cause is due largely to the RBC framework’s lack of authority. This is because the legal framework regulating the RBC framework has limited legal authority; consequently, virtually no authority is delegated to this arrangement. Accordingly, the RBC framework has no full authority regarding water resource management as its decisions, if any, can be enforced upon only public agencies and state-owned enterprises. Furthermore, it also has less authority when compared to other public bodies governed by superior legal frameworks; as such, it cannot force active participation in the RBC arrangement, and is not officially recognized (e.g. by the budget allocation system). It can be seen as important that with no authority delegated, non-public sector representatives do not share any decision making power despite their inclusion into the framework concerned. Therefore, to avert the same result generated by the RBC framework in moving toward collaborative water governance, policy changes are needed regarding its authority and implementation process at the national level, or at the DWR. Ideally, a change is required at the national level by passing a comprehensive legal framework, i.e. a Water Act. By this law, the RBC framework’s authority in managing water resources is secured and the framework itself is officially recognized. Arrangements for implementation of the RBC framework also can be prescribed, e.g. a budget allocation system recognizing the RBC framework and creating the RBC’s own office. However, this option is rather difficult to achieve, if not impossible, due to the lack of political support. A more probable change at the national level would be to issue a new regulation that revises the RBC framework, which can be done more easily than passing a law. Essentially, under this new regulation, the new RBC framework would be based at the provincial level. As such, the RBC would be abolished, while the provincial RBC and its governing bodies would be transformed to ‘collaborative watershed partnerships’ focused on a provincial river basin master/action plan. By this new regulation, the public bodies concerned would be obliged to follow the plan mentioned when preparing their water resource-related projects/programs, which would be applicable within authority of the regulation. In addition, diverse activities (e.g. meetings and capacity building) should be organized in order to support both the river basin governing bodies and implementing units of the DWR. The DWR should change its policies regarding implementation of the RBC framework, if there is no change at the national level, and the RBC framework continues to be carried out under the current regulation. It is essential in this circumstance for the DWR to encourage a revision of the RBC structure in order to make it less complex and more manageable, and shift the focus from the RBC itself to the river basin governing bodies at the provincial and sub-river basin level. Besides capacity building activities, and frequent and less formal meetings, the DWR should also direct its implementing units to facilitate the river basin governing bodies in order to develop a river basin management plan for respective provinces. This should be based on the problems and needs of the sub-river basins located in those particular provinces; and presented through the public agencies and LGOs concerned for consideration and inclusion in their own plans. This might be the only way to increase the likelihood of some elements of the river basin management plan being realized, given that the RBC framework has no authority or official recognition.
Conflicts of human land-use and conservation areas : the case of Asian elephants in rubber-dominated landscapes of Southeast Asia
(2017) Harich, Franziska K.; Treydte, Anna C.
Over the last decades, expanding rubber plantations in Southeast Asia have continuously diminished natural habitat, thereby increasing conflicts between human land-uses and nature conservation. The consequences are manifold, with short-term economic benefits for smallholder farmers and long-term costs for species diversity and ecosystem services (ESS). Sustainable wildlife populations are critical for ecosystem functioning but the ongoing habitat degradation and conflicts with people threaten the survival of larger mammal populations. This trend is particularly problematic if the respective species in decline are keystone species such as the Asian elephant (Elephas maximus), which holds important ecological functions in maintaining tree diversity. Continuous land-use transformations increase the importance of conservation efforts for biodiversity within the agricultural matrix. The major aim of this thesis’ work was to analyze the potential of rubber-dominated landscapes in sustaining wild mammal populations while considering the risk of conflicts due to wildlife damage as well as the ecological importance of mammals. As a first step, the literature on wild mammals in rubber and oil palm plantations was analyzed to provide an overview on species diversity found in these systems. Our review showed that species richness was highly reduced in the plantations compared to the forest and that most species in the farms were rather visitors than residents. For a detailed assessment of species richness and presence in rubber plantations, transect and camera trap surveys were conducted in the farm-forest transition zone of the Tai Rom Yen National Park in southern Thailand. Furthermore, farmers were interviewed on the kind and extent of wildlife damage. With 35 recorded wildlife species, the forest was found to hold the highest diversity while more than 70% of these mammals were still found at the forest edge. However, a strong decline of species diversity and presence was observed in the farmland. Crop damage by wildlife affected 40% of all interviewed farmers. In 85% of all rubber damage incidents, young trees were affected, which had not yet been tapped. Elephants were most frequently named as damage causing species. Nevertheless, damage to rubber occurred only in half of the elephant visits, indicating that this crop species was not particularly attractive to wildlife. To account not only for the costs inflicted through elephant damage but also for the ecological benefits elephants provide, the potential of these megaherbivores for seed dispersal was assessed as a crucial ecological function in forest ecosystems. Feeding experiments with elephants were conducted and germination success of ingested and fresh control seeds of a tree species with characteristic mega-faunal syndrome fruits (Dillenia indica L.) was monitored. Seeds ingested by elephants showed a significantly higher and earlier likelihood for germination compared to control seeds. The exemplary tree species in our experiments did not solely depend on but benefited from elephant consumption for germination. This highlights the risks of long-term negative implications for certain tree species and entire ecosystems if elephant and other large mammal populations further decline. Biodiversity is an integral component of ecosystem functioning and the provisioning of services. However, a challenge in the evaluation of ESS is the allowance for the many facets of biodiversity assessments. We therefore developed a methodology for including multiple levels of species diversity into an ESS evaluation model. Diversity data of animal groups and plants derived from our data collections and from literature were normalized using the most diverse habitat as benchmark. Through this approach we obtained a comparable habitat suitability matrix for different land-use systems, which was then applied to different land-use scenarios. The outcomes confirmed that a conservation focused scenario scored higher habitat suitability for all species as well as for threatened ones compared to two other scenarios with no or limited conservation measures. Increasing conflicts between human land-use and nature conservation as a result of shrinking resources pose imminent risks for the diversity and resilience of ecosystems. This thesis provides an assessment of the current state of and conflicts with wildlife diversity in rubber-dominated landscapes surrounding protected areas. The results of this thesis can serve as a basis for the development of measures to consolidate farming and conservation interests. Although intensively managed plantations cannot substitute for natural forests, efforts are required to conserve multiple levels of biodiversity within the farming landscape. High species diversity will maintain ecosystem functions and services sustainably, which both human and wildlife communities rely on for their long-term persistence.
Crop yield and fate of nitrogen fertilizer in maize-based soil conservation systems in Western Thailand
(2021) Wongleecharoen, Chalermchart; Cadisch, Georg
The increase in food demand and land scarcity in high-potential lowland areas have forced cropping intensification with a transformation of land use from subsistence to permanent agriculture in remote hillside in Southeast Asia. This change and inappropriate land use are the prime cause of soil degradation by erosion, which have negatively affected the agricultural systems productivity and sustainability in Thailand. Therefore, vulnerable land in sloping terrain is classified as unsuitable for continuous production of arable crops unless conservation measures are introduced to stabilize the landscape. Even though conservation practices can stabilize sloping land, farmers have not been widely adopted the measures due to various constraints, such as crop area loss and crop-tree competition. To improve land use management, a two-year study (2010-2011) was conducted at the Queen Sirikit research station (13°28’N, 99°16’E), Ratchaburi Province, Thailand, on a hillside with a slope of around 20%. The treatments consisted of (T1) maize (Zea mays L.) mono-crop under tillage and fertilization, (T2) maize intercropped with chili (Capsicum annuum L.) under tillage and fertilization, (T3) maize intercropped with chili, application of minimum tillage plus Jack bean (Canavalia ensiformis (L.) DC) relay cropping and fertilizer application, (T4) maize intercropped with chili, application of minimum tillage with Jack bean relay cropping and fertilizer application plus perennial hedges of Leucaena leucocephala (Lam.) de Wit, (T5) as T3 but without fertilization, and (T6) as T4 but without fertilization. There was an additional plot of chili sole cropping to calculate the land equivalent ratio (LER). The first part of the study evaluated yield performance and nitrogen use efficiency (NUE) of crops using the 15N isotope technique under diverse fertilized cropping systems during the first year. Maize grain yields were lower in T2 (3.1 Mg ha-1), T3 (2.6 Mg ha-1) and T4 (3.3 Mg ha-1) than in the control (T1) (6.7 Mg ha-1). The total returns from maize and chili yields were 1,914, 5,129, 3,829, 3,900, 3,494, and 2,976 USD ha-1, for T1, T2, T3, T4, T5 and T6, respectively. Higher economic returns in mixed crop systems, by selling both maize and chilies, compensated for the maize area loss by intercropping. Maize 15NUE was highest in T2 (53.5%), being significantly higher than in T1 (47.0%), T3 (45.5%), and T4 (45.7%). Overall system’s NUE in T2 (56.8%) was comparable to T1 (53.8%) and T4 (54.5%) but significantly lower in T3 (48.6%). Minimum tillage and hedgerows (despite their positive filter effect) did not increase NUE but adversely affected maize growth during the establishment phase. The second part of the study examined nitrogen fertilizers fate and quantified partial nitrogen budgets at plot level over two cropping seasons for various maize-based cropping systems with or without fertilizer application. Overall plant uptake of fertilizer 15N applied to maize was 48.6-56.8% over the first season, while residual fertilizer 15N recovery of plants was only 2.3-4.9% over the subsequent season. The quantity of applied labelled N remaining in the soil at the end of season 1 and season 2 was 6.2-28.1% and 7.7-28.6%, respectively. Thus, 60.0-76.0% in season 1 and 12.7-31.3% in season 2 of the applied fertilizer 15N were accounted for within the plant-soil system. Consequently, 24.0-40.0% and 12.9-16.1% of labelled fertilizer N were not accounted for at the end of season 1 and season 2, respectively. The derived N balance over two years revealed severe soil N depletion under T1 (-202 kg N ha-1), T5 (-86 kg N ha-1) and T6 (-48 kg N ha-1), and a slightly negative N budget under T2 (-5 kg N ha-1). In contrast, T3 (87 kg N ha-1) and T4 (62 kg N ha-1) had positive N balances. The increase of N input via additional N fertilizer applied to chili and symbiotic N2 fixation of legumes, and the reduction of N losses by soil erosion and unaccounted fertilizer N (probably lost via leaching, volatilization and denitrification) were the main factors of the positive N balances under maize-chili intercropping systems with conservation measures and fertilization (T3 and T4). Maize yield decline under T1, T2, T5 and T6 in season 2 was related to negative N balances, while maize yield increase under T3 and T4 was related to positive N balances. However, maize-chili intercropping with fertilization had some advantage (LER > 1.0) relative to sole species cropping. Moreover, total returns from crop yields in season 2 of all maize-chili intercroppings (1,378-1,818 USD ha-1) were higher than chili sole cropping (1,321 USD ha-1), which pointed to its crucial role in decreasing production risk by reducing yield loss by pests and diseases observed in chili plants. The third part of the study used combined data of stable isotope discrimination and electrical resistivity tomography (ERT) to improve understanding of competition at the crop-soil-hedge interface. Hedges significantly reduced maize grain yield and aboveground biomass in rows close to hedgerows. ERT revealed water depletion was stronger in T1 than in T4 and T6, confirming time domain reflectometry (TDR) and leaf area data. In T4, water depletion was higher in maize rows close to the hedge than rows distant to hedges and maize grain δ13C was significantly less negative in rows close to the hedge ( 10.33‰) compared to distant ones ( 10.64‰). Lack of N increased grain δ13C in T6 ( 9.32‰, p ≤ 0.001). Both methods were negatively correlated with each other (r= 0.66, p ≤ 0.001). Combining ERT with grain δ13C and %N allowed identifying that maize growth close to hedges was limited by N and not by water supply. In conclusion, the results suggested a significant positive interaction between mineral N fertilizer, intercropping systems and soil conservation measures in maintaining or improving crop yields and N balances in Thailand’s hillside agriculture. Simultaneously, combining ERT imaging and 13C isotopic discrimination approaches improved the understanding of spatial-temporal competition patterns at the hedge-soil-crop interface and pointed out that competition in maize-based hedgerow systems was driven by nitrogen rather than water limitation. Therefore, sustainable agriculture might be achieved if farmers in Thailand combine soil conservation measures with appropriate and targeted N fertilizer use.
Introduction of micro-sprinkler systems to mango production into theuplands Northern Thailand
(2011) Müller, Joachim; Spreer, Wolfram; Schulze, Karin; Srikasetsarakul, Umavadee; Ongprasert, Somchai
In order to asses water saving potentials of advanced irrigation methods in irrigated mango production in Northern Thailand, micro sprinklers have been introduced and compared into the area. Three micro sprinkler treatments were established on two commercial orchards: a. Full irrigation based on climate data, b. Partial Rootzone Drying, c. Farmer?s decision. These treatments were compared to the traditional irrigation methods. It was found that by the introduction of micro sprinklers, farmers were able to increase their water use efficiency, while the fruit size distribution was more favourable for export marketing.
Measuring and modelling resource use competition at the crop-soil-hedge interface on a hillside in Western Thailand
(2015) Hussain, Khalid; Cadisch, Georg
Thailand’s western uplands are facing severe soil loss and runoff problems due to intensive cultivation of cash crops for high food, feed, fiber, and fuel demand by an increasing population. Thus the Land Development Department and the International Board for Soil Research and Management in Thailand are promoting the use of soil conservation measures such as contour hedgerows, grass barriers and agroforestry systems based on fruit trees and annual crops. Although such measures have been shown to be effective in controlling soil erosion, farmers often are reluctant to adopt such practices as inclusion of trees reduces the cropped area and yields competition for available resources with crops. Hence, a better understanding of the underlying processes at the crop-soil-hedge interface is needed to design soil conservation systems that are more attractive for farmers. It was hypothesized that soil conservation systems with hedgerows and intercropping will induce spatial patterns of resource use which can be linked to competition while planting patterns affect canopy characteristics and light distributions. This study focused on the following objectives; (i) to improve understanding of competition at the crop soil hedge interface by combining stable isotope discrimination, electrical resistivity tomography and time domain reflectometry, (ii) to identify the effects of intercropping and hedgerows on maize biomass accumulation, nitrogen concentration and light use efficiency, (iii) to evaluate the competition between maize hedges at crop-soil-hedge interface, (iv) to explore possible mitigating options to cope with competition between hedge and maize by using a modelling approach. A field trial was laid out in randomized complete block design with three replicates at Queen Sirikit research farm, Ban Bo Wi village (13°28´ N and 99°15´ E), Suan Phueng District, Ratchaburi province in western Thailand with 20-25% slope magnitude. The experiment was established in 2009 while the research presented here was carried out during the 2010 and 2011 maize growing seasons. Six cropping treatments with following management practices were investigated: (T1, control) maize [Zea mays L.) monocrop, tillage, with fertilizer application (farmer’s practice; (T2) maize intercropped with chili (Capsicum annuum L. cv. Super Hot), tillage and fertilizer application; (T3) maize intercropped with chili, minimum tillage, fertilizer application, and Jack bean (Canavalia ensiformis (DC) L.) relay cropping; (T4) maize intercropped with chili, minimum tillage, fertilizer application, Jack bean relay cropped, and leucaena (Leucaena leucocephala (Lam.) de Wit) hedgerows; (T5) and (T6) as (T3) and (T4), respectively, but both without fertilizer application. Tillage was carried out manually by hoe to around 0-20 cm depth. Plots were 13 x 4 m. Fertilizer was applied to maize at a rate of 62, 22, 36 kg ha-1 of N, P, and K, respectively. Urea (N) application to maize was done in two splits as 31 kg ha-1 of N one month after sowing maize and another split of 31 kg ha-1 of N two months after sowing maize Chili received 92 kg N ha-1 at the time of transplanting and 92 kg ha-1 N as top dressing one month after transplanting. The impact of competition at the crop-soil-hedge interface was studied in 2011, two years after establishment of soil conservation measures, to exclude the establishment period of leucaena with a potentially weak impact on maize. At this time, highest above ground biomass (AGB) production of maize of 1364 g m-2 was witnessed in T2 being statistically different from all other treatments, except T4 and T3; while lowest above ground biomass production of 1034 g m-2 was observed in T5. In hedgerow treatments, maize rows planted distant to hedges produced 46% and 73% higher AGB than maize growing in rows close to the hedgerow (p≤0.0001) in T4 and T6, respectively. Similar effects were observed for plant height, grain nitrogen concentration and grain yield. Mean grain δ13C was significantly higher in T6 (-9.32‰) than in T4 (-10.49‰) and T1 (-10.55‰). Generally, higher δ13C signals mean higher water availability; however the higher δ13C signals in unfertilized T6 treatment imply that lack of nutrients may have led to increased δ13C values. Similarly in T4, δ13C signals were significantly higher in maize grains originating form rows planted close to hedges (10.33‰, p≤0.0001) than samples obtained from maize rows distant to hedges (-10.64‰). These results point out that competition at the crop-soil-hedge interface was driven by nutrient rather than water limitation. The electrical resistivity tomography (ERT) imaging further supported this finding showing that maize monocrop showed higher soil moisture depletion patterns than hedge intercrop with fertilizer (T4) treatment, while hedge intercrop without fertilization (T6) depleted soil moisture least. Light use efficiency (LUE) for maize above ground biomass production was statistically higher LUEAGB (1.56 g DM MJ-1) in maize and chilli intercrop (T2) than in maize sole cropping LUEAGB (1.23 g DM MJ-1). In T4 and T6 maize rows planted close to hedgerows had lower LUEAGB than rows distant to hedgerows. The land equivalent ratio showed that inclusion of hedgerows with fertilizer application in the intercropping treatment enhanced land utilization by 21%. The Water, Nutrient and Light Capture in Agroforestry (WaNuLCAS) model simulated AGB with R2= 0.83, RMSE=6.3, EF=0.82 and CD=1.4 during calibration while model validation also showed promising results with R2= 0. 76, P<0.001, RMSE=4.6 and EF=0.69. Simulations also pointed to major nutrient limitation between maize rows planted close to hedgerows. Simulations showed that negative impacts of hedgerows on crops can be reduced by managing fertilizer application in hedge adjacent maize rows leading to a successful application of agroforestry systems on a long-term basis not only for soil conservation but also for sustainable crop production in tropical uplands. The study figured out the scope of stable isotopic discrimination, ERT, light use efficiency and modelling approaches for evaluating resource use competition at crop-soil-hedge interface on hillside agriculture. The combination of isotopic discrimination and ERT measurements provided useful information for identification of cause-impact relationships. Spatial LUE patterns provided insights for canopy light harvest under various soil conservation options. Furthermore, light use data was also helpful in validation of WaNuLCAS model which did not only provide multiple options to figure out resource use competition at crop-soil-hedge interface but also allowed to test mitigation options for sustainable crop production in tropical uplands. Model scenarios showed that negative impacts of hedgerows on crops growing close to hedges can be reduced by applying minute additional doses of fertilizer only to the crop rows planted close to hedgerows, leading to a sustainable crop production along with soil conservation. Productivity evaluation of investigated cropping systems showed that inclusion of hedgerows and intercropping in tropical hillside agriculture is promising in enhancing crop production and thus can be adopted by farmers with yield advantage.
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.
Thermal imaging for assessment of maize water stress and yield prediction under drought conditions
(2022) Pradawet, Chukiat; Khongdee, Nuttapon; Pansak, Wanwisa; Spreer, Wolfram; Hilger, Thomas; Cadisch, Georg
Maize production in Thailand is increasingly suffering from drought periods along the cropping season. This creates the need for rapid and accurate methods to detect crop water stress to prevent yield loss. The study was, therefore, conducted to improve the efficacy of thermal imaging for assessing maize water stress and yield prediction. The experiment was carried out under controlled and field conditions in Phitsanulok, Thailand. Five treatments were applied, including (T1) fully irrigated treatment with 100% of crop water requirement (CWR) as control; (T2) early stress with 50% of CWR from 20 days after sowing (DAS) until anthesis and subsequent rewatering; (T3) sustained deficit at 50% of CWR from 20 DAS until harvest; (T4) late stress with 100% of CWR until anthesis and 50% of CWR after anthesis until harvest; (T5) late stress with 100% of CWR until anthesis and no irrigation after anthesis. Canopy temperature (FLIR), crop growth and soil moisture were measured at 5‐day‐intervals. Under controlled conditions, early water stress significantly reduced maize growth and yield. Water deficit after anthesis had no significant effect. A new combination of wet/dry sponge type reference surfaces was used for the determination of the Crop Water Stress Index (CWSI). There was a strong relationship between CWSI and stomatal conductance (R² = 0.90), with a CWSI of 0.35 being correlated to a 64%‐yield loss. Assessing CWSI at 55 DAS, that is, at tasseling, under greenhouse conditions corresponded best to the final maize yield. This linear regression model validated well in both maize lowland (R² = 0.94) and maize upland fields (R² = 0.97) under the prevailing variety, soil and climate conditions. The results demonstrate that, using improved standardized references and data acquisition protocols, thermal imaging CWSI monitoring according to critical phenological stages enables yield prediction under drought stress.
Towards regionalisation of soils in Northern Thailand and consequences for mapping approaches and upscaling procedures
(2008) Schuler, Ulrich
The purpose of this study was to identify the key factors of soil formation and distribution in North-western Thailand in order to enable predictive mapping. Further objectives were to investigate different soil mapping approaches, regarding their suitability for specific areas and scales and to assess the potential of local (soil) knowledge for soil mapping and land use planning. In order to cover the essential petrographic inventory of North-western Thailand three different petrographic areas were selected. The investigated topics were petrographic diversity, spatial organisation of soils and variability of their physical and chemical properties, as well as local soil knowledge of farmers in the respective areas. In addition thematic maps were generated comprising geology, WRB soil groups, and different soil properties. Soil mapping was carried out by using four different methods, the intensive mapping approach, maximum likelihood method, randomised grid cell approach, as well as elicitation of local knowledge. The intensive mapping approach comprised transect investigations, investigation points of the randomised grid cell approach, and additional investigation points, which were selected for areas with increased soil and petrographic variability. All maps based on the intensive mapping approach contained the highest sampling point density and maximum amount of information. These maps were used as a reference for the other mapping approaches applied here.