Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

This study addresses transpiration in a tropical evergreen mountain forest in the Ecuadorian Andes from the leaf to the stand level, with emphasis on nocturnal plant-water relations. The stand level: Evapotranspiration (ET) measured over 12 months with the Eddy-Covariance (ECov) technique proved as the major share (79%) of water received from precipitation. Irre- spective of the humid climate, the vegetation transpired day and night. On average, 15.3% of the total daily ET were due to nocturnal transpiration. Short spells of drought increased daily ET, mainly by enhanced nighttime transpiration. Following leaf transpiration rather than air temperature and atmospheric water vapor deficit, ET showed its maximum already in the morning hours. The tree level: Due to the humid climate, the total water consumption of trees was generally low. Nevertheless, xylem sap flux measurements separated the investigated tree species into a group showing relatively high and another one with low sap flux rates. The leaf level: Transpiration rates of Tapirira guianensis, a member of the high- flux-rate group, were more than twice those of Ocotea aciphylla, a representative of the group showing low sap flux rates. Representatives of the Tapirira group operated at a rela- tively high leaf water potential but with a considerable diurnal amplitude, while the leaves of the Ocotea group showed low water potential and small diurnal fluctuations. Overall, the Tapirira group performed anisohydrically and the Ocotea group isohydrically. Grouping of the tree species by their water relations complied with the extents of the diurnal stem circum- ference fluctuations. Nighttime transpiration and hydrological type: In contrast to the isohy- drically performing trees of the Ocotea group, the anisohydric trees showed considerable water vapour pressure deficit (VPD)-dependent nocturnal transpiration. Therefore, we con- clude that nighttime ET at the forest level is mainly sourced by the tree species with aniso- hydric performance.

Abstract:

Background: Since the 1990’s, afforestation programs in the páramo have been implemented to offset carbon emissions through carbon sequestration, mainly using pine plantations. However, several studies have indicated that after the establishment of pine plantations in grasslands, there is an alteration of carbon pools including a decrease of the soil organic carbon (SOC) pool. The aim of this study is to investigate the impact of the establishment of pine plantations on the carbon stocks in different altitudes of the páramo ecosystem of South Ecuador. Results: At seven locations within an elevational gradient from 2780 to 3760 m a.s.l., we measured and compared carbon stocks of three types of land use: natural grassland, grazed páramo, and Pinus patula Schlltdl. & Cham. plantation sites. For a more accurate estimation of pine tree carbon, we developed our own allometric equations. There were significant (p < 0.05) differences between the amounts of carbon stored in the carbon pools aboveground and belowground for the three types of land use. In most of the locations, pine plantations revealed the highest amounts of aboveground and belowground carbon (55.4 and 6.9 tC/ha) followed by natural grassland (23.1 and 2.7 tC/ha) and grazed páramo sites (9.1 and 1.5 tC/ha). Concerning the SOC pools, most of the locations revealed significant lower values of plantations’ SOC in comparison to natural grassland and grazed páramo sites. Higher elevation was associated with lower amounts of pines’ biomass. Conclusions: Even though plantations store high amounts of carbon, natural páramo grassland can also store substantial amounts above and belowground, without negatively affecting the soils and putting other páramo ecosystem services at risk. Consequently, plans for afforestation in the páramo should be assessed case by case, considering not only the limiting factor of elevation, but also the site quality especially affected by the type of previous land use.

Abstract:

Tropical mountain ecosystems are threatened by climate and land-use changes. Their diversity and complexity make projec- tions how they respond to environmental changes challenging. A suitable way are trait-based approaches, by distinguishing between response traits that determine the resistance of species to environmental changes and efect traits that are relevant for species’ interactions, biotic processes, and ecosystem functions. The combination of those approaches with land surface models (LSM) linking the functional community composition to ecosystem functions provides new ways to project the response of ecosystems to environmental changes. With the interdisciplinary project RESPECT, we propose a research framework that uses a trait-based response-efect-framework (REF) to quantify relationships between abiotic conditions, the diversity of functional traits in communities, and associated biotic processes, informing a biodiversity-LSM. We apply the framework to a megadiverse tropical mountain forest. We use a plot design along an elevation and a land-use gradient to collect data on abiotic drivers, functional traits, and biotic processes. We integrate these data to build the biodiversity- LSM and illustrate how to test the model. REF results show that aboveground biomass production is not directly related to changing climatic conditions, but indirectly through associated changes in functional traits. Herbivory is directly related to changing abiotic conditions. The biodiversity-LSM informed by local functional trait and soil data improved the simulation of biomass production substantially. We conclude that local data, also derived from previous projects (platform Ecuador), are key elements of the research framework. We specify essential datasets to apply this framework to other mountain ecosystems.

Abstract:

Abstract Conversion of tropical forests is among the primary causes of global environmental change. The loss of their important environmental services has prompted calls to integrate ecosystem services (ES) in addition to socio-economic objectives in decision-making. To test the effect of accounting for both ES and socio-economic objectives in land-use decisions, we develop a new dynamic approach to model deforestation scenarios for tropical mountain forests. We integrate multi-objective optimization of land allocation with an innovative approach to consider uncertainty spaces for each objective. These uncertainty spaces account for potential variability among decision-makers, who may have different expectations about the future. When optimizing only socio-economic objectives, the model continues the past trend in deforestation (1975–2015) in the projected land-use allocation (2015–2070). Based on indicators for biomass production, carbon storage, climate and water regulation, and soil quality, we show that considering multiple ES in addition to the socio-economic objectives has heterogeneous effects on land-use allocation. It saves some natural forest if the natural forest share is below 38%, and can stop deforestation once the natural forest share drops below 10%. For landscapes with high shares of forest (38%–80% in our study), accounting for multiple ES under high uncertainty of their indicators may, however, accelerate deforestation. For such multifunctional landscapes, two main effects prevail: (a) accelerated expansion of diversified non-natural areas to elevate the levels of the indicators and (b) increased landscape diversification to maintain multiple ES, reducing the proportion of natural forest. Only when accounting for vascular plant species richness as an explicit objective in the optimization, deforestation was consistently reduced. Aiming for multifunctional landscapes may therefore conflict with the aim of reducing deforestation, which we can quantify here for the first time. Our findings are relevant for identifying types of landscapes where this conflict may arise and to better align respective policies.

Abstract:

Soils of Páramo ecosystems regulate the water supply to many Andean populations. In spite of being a necessary input to distributed hydrological models, regionalized soil water retention data from these areas are currently not available. The investigated catchment of the Quinuas River has a size of about 90 km2 and comprises parts of the Cajas National Park in southern Ecuador. It is dominated by soils with high organic carbon contents, which display characteristics of volcanic influence. Besides providing spatial predictions of soil water retention at the catchment scale, the study presents a detailed methodological insight to model setup and validation of the underlying machine learning approach with random forest. The developed models performed well predicting volumetric water contents between 0.55 and 0.9 cm3 cm? 3. Among the predictors derived from a digital elevation model and a Landsat image, altitude and several vegetation indices provided the most information content. The regionalized maps show particularly low water retention values in the lower Quinuas valley, which go along with high prediction uncertainties. Due to the small size of the dataset, mineral soils could not be separated from organic soils, leading to a high prediction uncertainty in the lower part of the valley, where the soils are influenced by anthropogenic land use.

Abstract:

In 201 3, the “Platform for Biodiversity and Ecosystem Monitoring and Research in South Ecuador” (www.TropicalMountainForest.org) was launched as a knowledge transfer program in the biodiversity hotspot of the southern Ecuadorian Andes, jointly funded by the German Research Foundation (DFG) and Ecuadorian non-university partners. One of the overall aims of the transdisciplinary program is to design science-directed recommendations for an ecologically sustainable, economically profitable and socially compatible use of the mainly rural land. The second major goal of the program is the development of functional indicators that are crucial for the monitoring of impacts of environmental change on the ecosystem and its functions. They encompass abiotic, abiotic-biotic and biotic-biotic interrelations, and are sensitive - though to different extent - to subtle changes in the environment. Therefore, it is not only the interaction per se, which has to be examined. In addition to that the quantification of the response to certain environmental stressors is needed. Representing the fundament of ecosystem functioning, biodiversity as such or certain functional taxa can be monitored for an assessment of the ecosystem’s state. Important further criteria for the selection of an indicator are general applicability, easiness of handling and stability against pitfalls. This book “Landscape Restoration, Sustainable Use and Cross-scale Monitoring of Biodiversity and Ecosystem Functions: A Science-directed Approach for South Ecuador” presents in its first part a compilation of sustainable land use concepts that have been proven for application in the Provinces Loja and Zamora Chinchipe and beyond, given comparable environmental conditions. The second part describes functional indicators as well as their development, monitoring and application. Both parts start with introductory chapters on the major aims of the respective transdisciplinary program, followed by contributions showing how land use concepts can be used to achieve sustainable management and ecosystem services, as well as how functional indicators can be used to assess and monitor the stability of biodiversity and ecosystem functions. It should be stressed that this book has not the aim to present only a scientific summary of the developed systems. Instead, it targets on stakeholders as our non-university partners and beyond which are in charge of environmental planning and ecosystem function surveillance in Ecuador. In the manner of a technical handbook, it gives a comprehensible introduction to the land use option or the indicator, followed by hints how to apply, implement and assess the developed systems. The book is and was complementing our three pillars of capacity building which also includes stakeholder workshops on the developed land use options and indicators, and demonstration plots in the field. With this book the authors highly acknowledge the generous funding of the research by the German Science Foundation (DFG) and the logistic, administrative and practical support by the foundation Naturaleza y Cultura Internacional (Loja and Del Mar). Such research requires also fruitful collaboration with local academic institutions, the Universidad Tecnica Particular de Loja, the Universidad Nacional de Loja, the Universidad de Cuenca, the Universidad de Azuay, and the local weather service INAMHI. These partnerships were a great experience in capacity building on both sides, as evidenced by a number of academic degrees obtained and by numerous joint publications. The authors are also grateful for the support of our nonuniversity research partners beyond NCI, namely ETAPA EP (Empresa Pública Municipal de Telecomunicaciones, Agua potable, lcantarillado y Saneamiento de Cuenca- Ecuador), the Gobierno Municipal de Zamora and the regional water fund FORAGUA (Fondo Regional del Agua). Further, sincere thanks are owed to the Ecuadorian Ministry of the Environment (MAE) for permission to conduct research in South Ecuador. The Editors

Abstract:

The relative importance of catchment's water provenance and flow paths varies in space and time, complicating the conceptualization of the rainfall-runoff responses. We assessed the temporal dynamics in source areas, flow paths, and age by End Member Mixing Analysis (EMMA), hydrograph separation, and Inverse Transit Time Proxies (ITTPs) estimation within a headwater catchment in the Ecuadorian Andes. Twenty-two solutes, stable isotopes, pH, and electrical conductivity from a stream and 12 potential sources were analyzed. Four end-members were required to satisfactorily represent the hydrological system, i.e., rainfall, spring water, and water from the bottom layers of Histosols and Andosols. Water from Histosols in and near the riparian zone was the highest source contributor to runoff throughout the year (39% for the drier season, 45% for the wetter season), highlighting the importance of the water that is stored in the riparian zone. Spring water contributions to streamflow tripled during the drier season, as evidenced by geochemical signatures that are consistent with deeper flow paths rather than shallow interflow through Andosols. Rainfall exhibited low seasonal variation in this contribution. Hydrograph separation revealed that 94% and 84% is preevent water in the drier and wetter seasons, respectively. From low-flow to high-flow conditions, all the sources increased their contribution except spring water. The relative age of stream water decreased during wetter periods, when the contributing area of the riparian zone expands. The multimethod and multitracer approach enabled to closely study the interchanging importance of flow processes and water source dynamics from an interannual perspective.

Abstract:

To improve the current knowledge of the rainfall–runoff phenomena of tropical montane catchments, we explored the usefulness of several hydrological indicators on a nested cloud forest catchment (76.9 km2). The used metrics belong to 5 categories: baseflow mean transit time, physicochemical properties of stream water, land cover, topographic, and hydrometric parameters. We applied diverse statistical techniques for data analysis and to contrast findings. Multiple regression analysis showed that mean transit times of base flow could be efficiently predicted by sodium concentrations (higher during baseflows) and temperatures of stream water, indicating a major influence of geomorphology rather than topographic or land cover characteristics. Principal component analysis revealed that no specific subset of catchment indicators could be identified as prevailing descriptors for all catchments. The agglomerative hierarchical clustering analysis provided concomitant results, implying larger levels of dissimilarity between smaller subcatchments than between larger ones. Overall, results point out an intricate interdependence of diverse processes at surface and subsurface level indicating a high level of heterogeneity. Disregarding heterogeneity of nested or paired catchments could lead to incomplete or misleading conclusions, especially in tropical mountain regions where pronounced spatial and temporal gradients are present.

Abstract:

The comparatively long research history within the study area allowed to develop well-grounded hypotheses on how the hydrological system within the study area should behave (Bogner et al., 2014; Boy et al., 2008; Bücker et al., 2011, 2010; Crespo et al., 2012, 2011; Fleischbein et al., 2006; Goller et al., 2005). Based on those earlier findings made within the study area and the hydrological research conducted elsewhere in tropical mountain cloud forests (see Bonell and Bruijnzeel, 2004; Bruijnzeel, 2004; Bruijnzeel et al., 2011 for recent overviews) provided the background to shape the research conducted within this dissertation around the focal point of global change impacts on the hydrological cycle inside the study area (see chapter 1.3).Separated into three chapters, each representing a scientific research paper, this thesis will address the issue on how to evaluate effects of land-use change on the hydrological cycle (chapter 2), how stable water isotopes are distributed over space and time within the study area (chapter 3) and how stable water isotopes can be used in hydrological models to assist this analysis of global change impacts in the future (chapter 4). All of the research conducted for this dissertation was performed in the Rio San Francisco catchment within South Ecuador.

Abstract:

The present study is composed of three interlinked research papers described in three respective chapters: Chapter 2: “Understanding uncertainties when inferring mean transit times of water trough tracer-based lumped-parameter models in Andean tropical montane cloud forest catchments” deals with the estimation of mean transit times and explores the most reliable transit time distribution functions for 32 sampled sites in the catchment, which included 18 soil water sites, 2 streamwater sites in the main river, 7 streamwater tributaries, 2 small creeks and 3 springwaters. For the analysis, seven lumped-parameters models were tested. Besides, for each simulation, uncertainties were accounted through applying the Generalized Likelihood Uncertainty Estimation approach (GLUE). Chapter 3: “Sampling frequency trade-offs in the assessment of mean transit times of tropical montane catchment waters under semi-steady-state conditions”. This chapter describes the effect of sampling resolution data on the results provided by lumped-parameter models. Based on the insights from results described in Chapter 2, only selected models and sampled sites were screened for intercomparison. The results of this topic were aimed to account the degree of reliability of mean transit time estimations. Chapter 4: “Multi-criteria assessment of water dynamics reveal subcatchment variability in a seemingly homogeneous montane rainforest catchment”. By considering a nested catchment approach (main river outlet and its seven tributaries), mean transit times and other diverse catchment characteristics data (e.g., hydrometric and topographic indices, physicochemical properties of stream waters) were used to perform diverse statistical and modelling techniques, such as bivariate and multivariate analysis, Principal Component Analysis (PCA), Cluster Analysis, EMMA, Hydrological and Chemical modelling. All of which allowed to gain insights on the key factors governing the flow processes in each analysed site.

Abstract:

As a consequence of the remote location of the Andean páramo is knowledge on their hydrologic functioning limited, notwithstanding this alpine tundra ecosystem act as water towers for a large fraction of the society. Given the harsh environmental conditions in this region is year-round monitoring cumbersome, and it would be beneficially if the monitoring needed for the understanding of the rainfall-runoff response could be limited in time. To identify the hydrological response and the effect of temporal monitoring a nested (n?=?7) hydrological monitoring network was set up in the Zhurucay catchment (7.53?km2), south Ecuador. The research questions were: (1) can event sampling provide similar information in comparison to continuous monitoring, and (2) if so, how many events are needed to achieve a similar degree of information? A subset of 34 rainfall runoff events was compared to monthly values derived from a continuous monitoring scheme from December 2010 to November 2013. Land cover and physiographic characteristics were correlated with eleven hydrological indices. Results show that despite some distinct differences between event and continuous sampling, both datasets reveal similar information; more in particular the monitoring of a single event in the rainy season provides the same information as continuous monitoring, while during the dry season 10 events ought to be monitored.

Abstract:

Few high-elevation tropical catchments worldwide are gauged, and even fewer are studied using combined hydrometric and isotopic data. Consequently, we lack information needed to understand processes governing rainfall–runoff dynamics and to predict their influence on downstream ecosystem functioning. To address this need, we present a combination of hydrometric and water stable isotopic observations in the wet Andean páramo ecosystem of the Zhurucay Ecohydrological Observatory (7.53?km2). The catchment is located in the Andes of south Ecuador between 3400 and 3900?m?a.s.l. Water samples for stable isotopic analysis were collected during 2?years (May 2011–May 2013), while rainfall and runoff measurements were continuously recorded since late 2010. The isotopic data reveal that andosol soils predominantly situated on hillslopes drain laterally to histosols (Andean páramo wetlands) mainly located at the valley bottom. Histosols, in turn, feed water to creeks and small rivers throughout the year, establishing hydrologic connectivity between wetlands and the drainage network. Runoff is primarily composed of pre-event water stored in the histosols, which is replenished by rainfall that infiltrates through the andosols. Contributions from the mineral horizon and the top of the fractured bedrock are small and only seem to influence discharge in small catchments during low flow generation (non-exceedance flows?<?Q35). Variations in source contributions are controlled by antecedent soil moisture, rainfall intensity, and duration of rainy periods. Saturated hydraulic conductivity of the soils, higher than the year-round low precipitation intensity, indicates that Hortonian overland flow rarely occurs during high-intensity precipitation events. Deep groundwater contributions to discharge seem to be minimal. These results suggest that, in this high-elevation tropical ecosystem, (1) subsurface flow is a dominant hydrological process and (2) (histosols) wetlands are the major source of stream runoff. Our study highlights that detailed isotopic characterization during short time periods provides valuable information about ecohydrological processes in regions where very few basins are gauged.

Abstract:

This study focuses on the investigation of the mean transit time (MTT) of water and its spatial variability in a tropical high-elevation ecosystem (wet Andean páramo). The study site is the Zhurucay River Ecohydrological Observatory (7.53?km2) located in southern Ecuador. A lumped parameter model considering five transit time distribution (TTD) functions was used to estimate MTTs under steady-state conditions (i.e., baseflow MTT). We used a unique data set of the ?18O isotopic composition of rainfall and streamflow water samples collected for 3 years (May 2011 to May 2014) in a nested monitoring system of streams. Linear regression between MTT and landscape (soil and vegetation cover, geology, and topography) and hydrometric (runoff coefficient and specific discharge rates) variables was used to explore controls on MTT variability, as well as mean electrical conductivity (MEC) as a possible proxy for MTT. Results revealed that the exponential TTD function best describes the hydrology of the site, indicating a relatively simple transition from rainfall water to the streams through the organic horizon of the wet páramo soils. MTT of the streams is relatively short (0.15–0.73 years, 53–264 days). Regression analysis revealed a negative correlation between the catchment's average slope and MTT (R2?=??0.78, p?<?0.05). MTT showed no significant correlation with hydrometric variables, whereas MEC increases with MTT (R2?=??0.89, p?<?0.001). Overall, we conclude that (1) baseflow MTT confirms that the hydrology of the ecosystem is dominated by shallow subsurface flow; (2) the interplay between the high storage capacity of the wet páramo soils and the slope of the catchments provides the ecosystem with high regulation capacity; and (3) MEC is an efficient predictor of MTT variability in this system of catchments with relatively homogeneous geology.

Abstract:

Tropical montane ecosystems of the Andes are critically threatened by a rapid land-use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest–pasture–urban) on stream physico-chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico-chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land-use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf-shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land-use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of native vegetation and riparian buffers to promote ecological integrity and functioning of tropical Andean stream ecosystems.

Abstract:

High landscape diversity is assumed to increase the number and level of ecosystem services. However, the interactions between ecosystem service provision, disturbance and landscape composition are poorly understood. Here we present a novel approach to include uncertainty in the optimization of land allocation for improving the provision of multiple ecosystem services. We refer to the rehabilitation of abandoned agricultural lands in Ecuador including two types of both afforestation and pasture rehabilitation, together with a succession option. Our results show that high compositional landscape diversity supports multiple ecosystem services (multifunction effect). This implicitly provides a buffer against uncertainty. Our work shows that active integration of uncertainty is only important when optimizing single or highly correlated ecosystem services and that the multifunction effect on landscape diversity is stronger than the uncertainty effect. This is an important insight to support a land-use planning based on ecosystem services.

Abstract:

Precipitation event samples and weekly based water samples from streams and soils were collected in a tropical montane cloud forest catchment for 2 years and analyzed for stable water isotopes in order to understand the effect of sampling frequency in the performance of three lumped-parameter distribution functions (exponential-piston flow, linear-piston flow and gamma) which were used to estimate mean transit times of waters. Precipitation data, used as input function for the models, were aggregated to daily, weekly, bi-weekly, monthly and bi-monthly sampling resolutions, while analyzed frequencies for outflows went from weekly to bi-monthly. By using different scenarios involving diverse sampling frequencies, this study reveals that the effect of lowering the sampling frequency depends on the water type. For soil waters, with transit times on the order of few weeks, there was a clear trend of over predictions. In contrast, the trend for stream waters, which have a more damped isotopic signal and mean transit times on the order of 2 to 4 years, was less clear and showed a dependence on the type of model used. The trade-off to coarse data resolutions could potentially lead to misleading conclusions on how water actually moves through the catchment, notwithstanding that these predictions could reach better fitting efficiencies, fewer uncertainties, errors and biases. For both water types an optimal sampling frequency seems to be 1 or at most 2 weeks. The results of our analyses provide information for the planning of future fieldwork in similar Andean or other catchments.

Abstract:

Future climate projections from general circulation models (GCMs) predict an acceleration of the global hydrological cycle throughout the 21st century in response to human-induced rise in temperatures. However, projections of GCMs are too coarse in resolution to be used in local studies of climate change impacts. To cope with this problem, downscaling methods have been developed that transform climate projections into high resolution datasets to drive impact models such as rainfall-runoff models. Generally, the range of changes simulated by different GCMs is considered to be the major source of variability in the results of such studies. However, the cascade of uncertainty in runoff projections is further elongated by differences between impact models, especially where robust calibration is hampered by the scarcity of data. Here, we address the relative importance of these different sources of uncertainty in a poorly monitored headwater catchment of the Ecuadorian Andes. Therefore, we force 7 hydrological models with downscaled outputs of 8 GCMs driven by the A1B and A2 emission scenarios over the 21st century. Results indicate a likely increase in annual runoff by 2100 with a large variability between the different combinations of a climate model with a hydrological

Abstract:

Hillslopes are the dominant landscape components where incoming precipitation becomes groundwater, streamflow or atmospheric water vapor. However, directly observing flux partitioning in the soil is almost impossible. Hydrological hillslope models are therefore being used to investigate the processes involved. Here we report on a modeling experiment using the Catchment Modeling Framework (CMF) where measured stable water isotopes in vertical soil profiles along a tropical mountainous grassland hillslope transect are traced through the model to resolve potential mixing processes. CMF simulates advective transport of stable water isotopes 18O and 2H based on the Richards equation within a fully distributed 2-D representation of the hillslope. The model successfully replicates the observed temporal pattern of soil water isotope profiles (R2 0.84 and Nash– Sutcliffe efficiency (NSE) 0.42). Predicted flows are in good agreement with previous studies. We highlight the importance of groundwater recharge and shallow lateral subsurface flow, accounting for 50 and 16% of the total flow leaving the system, respectively. Surface runoff is negligible despite the steep slopes in the Ecuadorian study region.

Abstract:

Increasing demands for livelihood resources in tropical rural areas have led to progressive clearing of biodiverse natural forests. Restoration of abandoned farmlands could counter this process. However, as aims and modes of restoration differ in their ecological and socio-economic value, the assessment of achievable ecosystem functions and bene?ts requires holistic investigation. Here we combine the results from multidisciplinary research for a unique assessment based on a normalization of 23 ecological, economic and social indicators for four restoration options in the tropical Andes of Ecuador. A comparison of the outcomes among afforestation with native alder or exotic pine, pasture restoration with either low-input or intense management and the abandoned status quo shows that both variants of afforestation and intense pasture use improve the ecological value, but low-input pasture does not. Economic indicators favour either afforestation or intense pasturing. Both Mestizo and indigenous Saraguro settlers are more inclined to opt for afforestation.

Abstract:

Weekly samples from surface waters, springs, soil water and rainfall were collected in a 76.9 km² mountain rain forest catchment and its tributaries in southern Ecuador.Time series of the stable water isotopes (oxygen-18 and deuterium) were used to calculate mean transit times (MTTs) and the transit time distribution functions (TTDs) solving the convolution method for seven lumped-parameter models. For each model setup, the generalized likelihood uncertainty estimation (GLUE) methodology was applied to find the best predictions, behavioral solutions and parameter identifiability. For the study basin, TTDs based on model types such as the linear–piston flow for soil waters and the exponential–piston flow for surface waters and springs performed better than more versatile equations such as the gamma and the two parallel linear reservoirs. Notwithstanding both approaches yielded a better goodness of fit for most sites, but with considerable larger uncertainty shown by GLUE. Among the tested models, corresponding results were obtained for soil waters with short MTTs (ranging from 2 to 9 weeks). For waters with longer MTTs differences were found, suggesting that for those cases the MTT should be based at least on an intercomparison of several models. Under dominant baseflow conditions long MTTs for stream water ? 2 yr were detected, a phenomenon also observed for shallow springs. Short MTTs for water in the top soil layer indicate a rapid exchange of surface waters with deeper soil horizons. Differences in travel times between soils suggest that there is evidence of a land use effect on flow generation.

Abstract:

This study presents the spatial and temporal variability of ?18O and ?2H isotope signatures in precipitation of a south Ecuadorian montane cloud forest catchment (San Francisco catchment). From 2 September to 25 December 2010, event sampling of open rainfall was conducted along an altitudinal transect (1800 to 2800 m a.s.l.) to investigate possible effects of altitude and weather conditions on the isotope signature. The spatial variability is mainly affected by the altitude effect. The event based ?18O altitude effect for the study area averages ?0.22‰ × 100 m?1 (?2H: ?1.12‰ × 100 m?1). The temporal variability is mostly controlled by prevailing air masses. Precipitation during the times of prevailing southeasterly trade winds is significantly enriched in heavy isotopes compared to precipitation during other weather conditions. In the study area, weather during austral winter is commonly controlled by southeasterly trade winds. Since the Amazon Basin contributes large amounts of recycled moisture to these air masses, trade wind-related precipitation is enriched in heavy isotopes. We used deuterium excess to further evaluate the contribution of recycled moisture to precipitation. Analogously to the ?18O and ?2H values, deuterium excess is significantly higher in trade wind-related precipitation. Consequently, it is assumed that evaporated moisture is responsible for high concentrations of heavy isotopes during austral winter.

Abstract:

Die tropischen Bergregenwälder Ecuadors gehören zu den artenreichsten Ökosystemen der Erde. Aufgrund ihrer Höhenlage und daraus bedingt besonderen klimatischen Bedingungen sind sie Lebensraum für zahlreiche Tier und Pflanzenarten. Zugleich sind sie durch intensive Landnutzung, Abholzung und Brandrodung bedroht. Die Bedeutung der Landnutzung bezüglich der Belastung, Wechselwirkungen und Auswirkungen von Nutzungsänderungen auf den Wasser und Stoffhaushalt zeigt einmal mehr die Notwendigkeit des Ressourcenmanagements für Gewässer in dieser Region. Das Forschungsgebiet des Rio San Francisco liegt im tropischen Bergregenwald von Süd-Ecuador. Hier wurden zwischen September 2011 und November 2011 die notwendigen Feldarbeiten durchgeführt und die hydrogeochemischen Reaktionen der Stoffflüsse in unterschiedlich genutzten Teileinzugsgebieten auf Niederschlagsereignisse untersucht. Dazu wurden Daten zur chemischen Zusammensetzung, pH und elektrischer Leitfähigkeit aus verschiedenen Flüssen bei unterschiedlichen Niederschlagsereignissen aufgenommen. Verdünnungseffekte und Aufkonzentrationen führen bei Niederschlagsereignissen zur Veränderung der chemischen Zusammensetzung der abflussgenerierenden Prozesse. Die Interaktionen dieser Prozesse, wie Grundwasserzustrom, Oberflächenabfluss und Zwischenabfluss im Boden, wurden im Zusammenhang mit Stoffausträgen in den unterschiedlichen Teileinzugsgebieten im Rahmen dieser Arbeit analysiert. Eine Ver??nderung des Abflusses resultiert üblich in eine Veränderung der chemischen Zusammensetzung des Flusswassers. Dieser Zusammenhang wird häufig in Form von Hysteresis Kurven dargestellt. Das Ziel dieser Arbeit ist es, die Beziehung zwischen Flussabfluss und quantitativer chemischer Veränderung unterschiedlicher Parameter zu erkennen und diese in Form von Hysteresis Kurven zu erklären. Während des Untersuchungszeitraums konnten 16 „Events“ aufgenommen werden und auf Hysteresis Effekte untersucht werden. Resultate zeigten keine einheitlichen Hysteresis Formen für die einzelnen Parameter und die Rotationsrichtung der einzelnen Kurven variierte bedeutsam. Die graphische Interpretation lieferte zudem keine hinreichende Erklärung zu den abflussgenerierenden Prozessen.

Abstract:

This thesis presents the spatial and temporal variability of d²H and d18O isotope signatures in the precipitation of a south ecuadorian montane cloud forest catchment. During the investigation period from 02.09.2010 to 25.12.2010 event sampling of freefall and throughfall was conducted along an altitudinal transect (1800m a.s.l. to 2800m a.s.l.) to investigate possible effects of altitude and land use on the isotope signature in precipitation. The data is further used to determine deuterium excess and the temporal variability during the investigation period. Temporal variability is mostly controlled by the prevailing air mass. During most time of the year, the study area is strongly affected by tropical trade winds. Due to the large input of reevaporated moisture to the air masses, which takes place during their passage over the amazon basin and during the orographic uplift at the slopes of the Andes, trade wind-related precipitation is highly enriched in heavy isotopes. High values in deuterium excess, which is used to asses the contribution of reevaporated moisture in precipitation, were observed during times of strong influence of trade winds. From Mid-October on, an ebbing of trade winds from the amazon basin was observed and the influence of other air masses rose. This change in weather patterns is consistent with considerably lower isotope signatures and deuterium excess in precipitation. Therefore, it can be concluded that the degree of reevaporation is low-er at that time. Spatial variability is mainly affected by the altitude effect, which reaches values of -1,12‰ × 100m-1 in the case of d²H and -0,22‰ × 100m-1 in the case of d18O in the study area. On average, throughfall is enriched compared to freefall by 2,28‰ of ²H and 0,31‰ of d18O, respectively. In combination with measurements of the isotope signatures of adjacent streams the data from this study allows determining and quantifying preferential path ways of water in the catchment and can be used to validate a hydrologic simulation model and to generate mixing models that allow to quantify the mean residence time of water in the catchment.

Abstract:

Der tropische Bergregenwald Ecuadors, welcher als „Hot Spot für Biodiversität“ (MYRES et al., 2000) gilt, ist einer der am stärksten bedrohten Ökosysteme weltweit. Um dieses Ökosystem besser zu verstehen und neue Erkenntnisse über Funktionsweisen der ökologischen Kreisläufe zu gewinnen, ist die Analyse vorhandener Umweltbedingungen und die damit verbundene Informationsbeschaffung von besonderer Bedeutung. Auch die interdisziplinäre Deutsche Forschergruppe (DFG) 816 Ecuador (Biodiversity and Sustainable Management of a Megadiverse Mountain Ecosystem in South Ecuador) hat sich die Aufgabe zum Ziel gesetzt das Gesamtökosystem „tropischer Bergregenwald“ besser zu verstehen und untersucht seit 1997 in insgesamt 25 Teilprojekten die Biodiversität und Ökosystemfunktionen, sowie Ökosystemleistungen und das Ökosystemmanagement. Im Rahmen dieser Masterarbeit soll, integriert in die Forschergruppe, ein Modell zur flächenhaften Vorhersage von Bodenkohlenstoff im Flusseinzugsgebiet des Rio San Francisco durch Punktdaten und Geländevariablen entwickelt werden. Die Arbeit ist in die Forschergruppe D4 „Catchment scale hydro-biogeochemical fluxes and aquatic diversity under global change“ eingegliedert und soll zum Verständnis hinsichtlich funktionaler Zusammenhänge und Prozesse im Ökosystem „tropischer Bergregenwald“ beitragen. In den letzten Jahren wurden verstärkt Modelle zur Beschreibung ökologischer Prozesse und der Klärung von Zusammenhängen zwischen dem Ökosystem, seinen Funktionen und Kompartimenten entwickelt, so werden beispielsweise auch im Kompartiment Boden immer häufiger Modelle zur Beschreibung und Analyse von Bodeneigenschaften herangezogen. Dabei spielt die Vorhersage von Bodeneigenschaften, was als digitale Bodenkartierung (Digital Soil Mapping, kurz DSM) bezeichnet wird eine entscheidende Rolle (Mc BARTNEY et al., 2003). Durch die digitale Bodenkartierung werden lückenhafte Punktdaten auf eine gesamte Fläche übertragen und in einem räumlichen Raster dargestellt. Diese Form der Modellierung bildet dabei ökologische Prozesse nach und schätzt die zu prognostizierenden Daten. Bodeneigenschaften können somit flächendeckend, sowie mit geringerem Kostenund Zeitaufwand zur Verfügung gestellt werden. Auch schwer zugängliche Bereiche, die eine Beprobung kaum möglich machen, können durch die digitale Bodenkartierung abgedeckt werden. Die Vorteile der Regionalisierung von Bodeneigenschaften mittels leicht zugänglicher Daten lässt das Digital Soil Mapping immer populärer werden. Eine besonders gut geeignete Regionalisierungsmethode für die digitale Bodenkartierung sind Entscheidungsbäume in Form von Klassifikationsund Regressionsbäumen (VASQUES et al., 2008). Der Ansatz des Klassifikationsund Regressionsbaums (kurz CART) kann durch die Erweiterung nach dem Ansatz Random Forest (kurz RF) verbessert werden. Dabei wird im Gegensatz zu einem Entscheidungsbaum ein „Wald von Entscheidungsbäumen“ erzeugt. Dieser kombinierte Ansatz wurde bereits von WIESMEIER et al. (2010) in einem Untersuchungsgebiet in der Inneren Mongolei angewendet und zeigt dort, dass besonders die Kombination beider Methoden (CART und RF) ein vielversprechendes Modell zur räumlichen Vorhersage von Bodeneigenschaften unter anderem auch des Bodenkohlenstoffgehalts ist. Auch durch LIEß et al. (2009) wurden bereits Modelle zur digitalen Bodenkartierung im Untersuchungsgebiet der Forschungsstation angewendet mit dem Ergebnis, dass sich durch CART Bodentypen realistisch vorhersagen lassen. Bodenkohlenstoff, der in dieser Arbeit die Zielvariable darstellt, spielt eine wichtige Rolle im globalen Kohlenstoffkreislauf. Böden stellen einen großen Speicher für organischen Kohlenstoff dar, der für die Nährstoffversorgung und das Wasserspeicherungsvermögen von Bedeutung ist. Der organische Kohlenstoff gelangt durch tote organische Substanz oder Bodenorganismen in den Boden. Dort erfolgen Stabilisierungsund Umwandlungsprozesse. Durch Erosion und Landnutzungswandel kann der im Boden gebundene Kohlenstoff wieder frei gesetzt werden (SCHEFFER und SCHACHTSCHABEL, 2010). Auch hinsichtlich der globalen Klimaerwärmung ist der im Boden gebundene Kohlenstoff ein wichtiger Parameter um Klimaund Bodenbedeckungsveränderungen besser verstehen und vorhersehen zu können (JOBBÁGY und JACKSON, 2000). Besonders in tropischen Bergregenwäldern sind Kohlenstoffgehalte und Kohlenstoffvorräte, sowie die vertikale Verteilung des Kohlenstoffgehalts bisher weitestgehend unbekannt (MOSER et al., 2011), weshalb eine Methode zur Modellierung und Vorhersage des Bodenkohlenstoffgehalts für das Untersuchungsgebiet der Forschungsstation Estación Científica San Francisco (ECSF) im tropischen Bergregenwald Ecuadors von hohem Interesse ist. Ziel dieser Masterarbeit ist, das Digital Soil Mapping im Flusseinzugsgebiet des Rio San Francisco auf Anwendbarkeit zu überprüfen. Es bildet somit eine Grundlage für zukünftige Modellierungsansätze im Einzugsgebiet der Forschungsstation. Des Weiteren gilt es die zum jetzigen Zeitpunkt vorliegenden Punktdaten des Bodenkohlenstoffgehalts flächendeckend vorherzusagen. Die erstellte Bodenkohlenstoffkarte stellt eine wichtige Informations-grundlage für weiterführende Modellierungen und Untersuchungen, beispielsweise von hydrologischen Prozessen und des bio-geochemischen Stoffkreislaufes dar. Die Ergebnisse der Arbeit werden für die gesamte DFG Forschergruppe ein Erkenntniszugewinn sein.

Abstract:

Zu den artenreichsten, aber auch gefährdetsten Ökosystemen unserer Erde zählen tropische Bergnebelwälder (Doumenge et al., 1995). Über die Funktionsweisen dieser empfindlichen Ökosysteme ist bisher noch nicht viel bekannt. Daher kann noch nicht abgeschätzt werden, inwieweit die Abholzung der Wälder sich auf die kleinskaligen Prozesse in diesen Ökosystemen auswirkt (Bücker et al., 2009). Im Jahre 1990 betrug in Ecuador die bewaldete Landesfläche 13.817.000 Hektar. 2010 waren es nur noch 9.865.000 Hektar Wald (FAO, 2010). In dieser Zeitspanne von 20 Jahren gingen also allein in Ecuador rund 4 Millionen Hektar Wald verloren. Die jährliche Abholzungsrate zwischen 2005 und 2010 betrug in dieser Region 1,89 % (FAO, 2010). Die Gründe für den weltweiten Verlust von Waldfläche sind vielfältig. Wenn in landwirtschaftlichen Gemeinschaften der Bedarf an Lebensmitteln und anderen agrarwirtschaftliche Gütern steigt, so muss der Ertrag einer bereits bewirtschafteten Fläche gesteigert werden (Marcoux, 2000). Kann dies nicht erreicht werden, wird meist neues Land für den Anbau von landwirtschaftlichen Gütern durch Abholzung der Wälder bereitgestellt (Marcoux, 2000). Ein weiterer Grund für die Abholzung der Wälder ist der Bedarf an Brennholz. Mehr als die Hälfte der Erdbevölkerung lebt in ländlichen Gebieten. Diese Menschen sind von der Nutzung der Wälder als Energielieferant abhängig (Marcoux, 2000). Neben diesen beiden gibt es noch viele weitere Gründe, die weltweit den Verlust von Wäldern verursachen. In Ecuador ist der wichtigste Grund für die Abholzung der Regenwälder die Umwandlung in Weideland (Günter et al., 2006). Die Abholzung von Wäldern hat schwerwiegende Konsequenzen für die Abflussmenge und die Erosion, also das Bodenmaterial, das vom Regenwasser abgeschwemmt und so vom Land in die Flüsse getragen wird (Neill et al., 2006). Werden Wälder durch Weideland ersetzt, so beeinflusst dies die hydrologischen Eigenschaften von Böden und das Gleichgewicht zwischen Niederschlägen und Evapotranspiration. Daraus resultieren fast ausnahmslos höhere Abflussmengen in Wassereinzugsgebieten (Neill et al., 2006).

Abstract:

In den komplexen Ökosystemen der Erde spielen Böden eine äußerst wichtige Rolle. Sie bieten den Lebensraum für Tiere und Pflanzen, Nutzungsfläche für menschliche Tätigkeiten und stellen eine wichtige Komponente des globalen Kohlenstoffkreislaufs dar, der unter anderem einen Einfluss auf das irdische Klima hat. Dadurch beeinflussen Böden und ihre Eigenschaften das Leben der Organismen auf unserem Planeten auf verschiedenen Ebenen. Allerdings gibt es bisher nur wenige Studien über Böden unter Urwald und unter entwaldeten Weideflächen im Ökosystem Bergregenwald (Makeschin et al., 2006). Die Abholzung von Nebelwäldern in Gebirgsregionen, zur Vermehrung von Weideflächen, gefährdet deren Rolle bezüglich Hydrologie und Bodenerhaltung (Stadtmüller, 1986). Sie zu schützen verringert das Risiko großflächiger Erosionen, des Verlustes endemischer Arten und einzigartigen Landschaften, sowie der Abnahme der Biodiversität und das Verschwinden wertvollen Erbmaterials (Stadtmüller, 1986). Ein besseres Verständnis der Auswirkungen von Entwaldungen auf die Bodeneigenschaften ist wichtig, um Weideflächen auf nachhaltige Weise zu bewirtschaften und die Konsequenzen der Abholzung präzise zu bewerten.

Abstract:

Tropical mountainous cloud forests belong to the most diverse ecosystems on earth. If you ask scientists which features characterize these ecosystems, then the answers are as diverse as is the flora and fauna within them: persistent cloud cover, reduced solar radiation due to cloud cover, distinctly structured vegetation forms, suppressed evapotranspiration as a consequence of high relative humidity, stripping of clouds by tree canopies and resulting large amount of throughfall, reduced canopy heights, high rainfall rates, gnarled tree trunks at increasing altitudes, substantial epiphyte biomass, moss-covered stems, organic rich and typically wet soils, and – last but not least – extremely high biodiversity with a paramount endemism (Bruijnzeel et al., 2011).

Abstract:

The main objective of this dissertation was to identify the rainfall runoff processes that control the discharge generation of the study areas. The research uses multi techniques including hydrometric data analysis, tracers (isotopes and chemical constituents) and conceptual modeling. The research questions were (i) in which way streamflow is controlled by micro-climate, precipitation pattern, slope, land cover and soil properties, amongst other catchment properties?, (ii) what are the main sources of water within the study areas?, and how the soil properties are influencing the runoff generation?, and (iii) could the identified conceptual model, using previous knowledge, be applied for the studied areas in the south of Ecuador?