Hydrological Response of Alpine Wetlands to ClimateWarming in the Eastern Tibetan Plateau

Alpine wetlands in the Tibetan Plateau (TP) play a crucial role in the regional hydrological cycle due to their strong influence on surface ecohydrological processes; therefore, understanding how TP wetlands respond to climate change is essential for projecting their future condition and potential vulnerability. We investigated the hydrological responses of a large TP wetland complex to recent climate change, by combining multiple satellite observations and in-situ hydro-meteorological records. We found different responses of runoff production to regional warming trends among three basins with similar climate, topography and vegetation cover but different wetland proportions. The basin with larger wetland proportion (40.1%) had a lower mean runoff coefficient (0.173 ± 0.006), and also showed increasingly lower runoff level (−3.9% year−1, p = 0.002) than the two adjacent basins. The satellite-based observations showed an increasing trend of annual non-frozen period, especially in the wetland-dominated region (2.64 day·year−1, p \u3c 0.10), and a strong extension of vegetation growing-season (0.26–0.41 day·year−1, p \u3c 0.10). Relatively strong increasing trends in evapotranspiration (ET) (~1.00 mm·year−1, p \u3c 0.01) and the vertical temperature gradient above ground surface (0.043 °C·year−1, p \u3c 0.05) in wetland-dominant areas were documented from satellite-based ET observations and weather station records. These results indicate recent surface drying and runoff reduction of alpine wetlands, and their potential vulnerability to degradation with continued climate warming

Carbon translocation from glacial and terrestrial to aqueous systems – characteristics and processing of dissolved organic matter in the endorheic Tibetan Lake Nam Co watershed

The Tibetan Plateau (TP) comprises sensitive alpine environments such as grassland biomes. Climatic changes and intensifying land use threaten these ecosystems. Therefore, it is important to understand the response of ecosystems to changing biotic and abiotic factors. The translocation of dissolved organic matter from glacial and terrestrial to aqueous systems is an important aspect of this response, specifically when characterizing changing conditions of freshwater resources and sensitive limnic ecosystems on the TP. Via changes in its chemical composition, characteristics, transformation and processing of DOM can be tracked. Three catchments of the Nam Co watershed of the TP (Niyaqu, Qugaqie and Zhagu) and the lake were investigated to understand how site specific terrestrial processes and seasonality affect the composition of DOM and alteration of organic compounds in streams and the lake of this endorheic basin. Four hypotheses were tested: H1 The natural diversity in the Nam Co watershed controls site specific effects on DOM composition. H2 Seasonal effects on DOM composition are driven by warm and moist summers influenced from the Indian summer monsoon (ISM) and cold and dry winters. H3/ H4a Site specific effects on DOM diminish by means of biological decomposition and photooxidation of DOM during the stream path / in the lake. Alongside H4b organic matter of the Nam Co Lake is independent from catchment influences, given by an autochthonous source of DOM. A multi-parameter approach was applied, consitsing of water chemistry parameters (pH, electric conductivity, cations and anions, dissolved inorganic carbon), concentration of dissolved organic carbon (DOC), DOM characteristics (chromophoric DOM, fluorescence DOM and δ13C of DOM) and DOM ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Sampling was conducted for three seasons, freshet in 2018, the phase of the ISM in 2019 and post-ISM baseflow in 2019. Alongside a watershed-wide plant cover estimate was composed, to explore the link between differences in DOM characteristics and degree of green plant cover. Sampling covers stream water, as well as endmember samples such as: glacial effluents, water of springs and water from an alpine wetland. The lake was covered by sampling the brackish zone and the lake pelagial and the lake surface. The composition of DOM differed between the three endmember groups and between stream samples of catchments. Glaciers showed a dual DOM source, indicating a glacial microbiome and compounds derived from burned fossil fuels. Springs differed based on their geographic location. Upland waters showed limited inputs of alpine pastures: lowland springs displayed influences of yak faeces with microbial reworked DOM, indicated by less negative δ13C and nitrogen. Wetlands were distinguished by more eutrophic conditions by highest concentrations in DOC and high amounts in N-heteroatoms. Streams were site specific with input sources derived from glaciers, wetlands, groundwater, intense animal husbandry and a plant-derived phenolic signature from alpine pastures aligned to the degree of plant cover. Seasonality affected DOM characteristics in stream water. During freshet, DOM was plant-derived, as was during baseflow conditions. A flush of dissolved organic carbon, accompanied by a compositional shift towards more microbial derived DOM was observed during the ISM season. Processing of DOM in streams was limited to the biolabile fraction of DOM of the glacial biome. Transformation of DOM was overruled by the constant input of plant derived phenolic DOM compounds from alpine pastures. Consequentially, the brackish intermixing zone showed the inflow of terrestrial DOM into the lake. In contrast, lake water exhibited distinct DOM characteristics, by lowest amounts in aromatic molecular compounds and DOM rich in 13C. This suggested intense processing of phenolic, terrestrial derived DOM by photooxidation, as well as a seasonally stable autochthonous DOM source derived from algae and microorganisms in lake water. In conclusion, DOM characteristics are largely influenced by local endmembers such as glaciers, springs and wetlands. Seasonality shows that shifts in the onset, and changes in the intensity of the ISM can largely modify DOM composition. Processing of DOM took place mainly in the lake. The study revealed that DOM is suited to function as a monitoring agent in this lake watershed. Hence, DOM is a helpful tool to understand changes in ecosystems, and forthcoming, to safeguard sensitive ecosystems of the TP.Deutsche Forschungsgemeinschaft (DFG)/International Research Training Group (GRK 2309/1)/317513741/E

A baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change

This report forms part of a larger research programme on 'Reinterpreting the Urban-Rural Continuum', which conceptualises and investigates current knowledge and research gaps concerning 'the role that ecosystems services play in the livelihoods of the poor in regions undergoing rapid change'. The report aims to conduct a baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. The appraisal is conducted at three spatial scales: global, regional (four consortia areas), and meso scale (case studies within the four regions). At all three scales of analysis water resources form the interweaving theme because water provides a vital provisioning service for people, supports all other ecosystem processes and because water resources are forecast to be severely affected under climate change scenarios. This report, combined with an Endnote library of over 1100 scientific papers, provides an annotated bibliography of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. After an introductory, section, Section 2 of the report defines water-related ecosystem services and how these are affected by human activities. Current knowledge and research gaps are then explored in relation to global scale climate and related hydrological changes (e.g. floods, droughts, flow regimes) (section 3). The report then discusses the impacts of climate changes on the ESPA regions, emphasising potential responses of biomes to the combined effects of climate change and human activities (particularly land use and management), and how these effects coupled with water store and flow regime manipulation by humans may affect the functioning of catchments and their ecosystem services (section 4). Finally, at the meso-scale, case studies are presented from within the ESPA regions to illustrate the close coupling of human activities and catchment performance in the context of environmental change (section 5). At the end of each section, research needs are identified and justified. These research needs are then amalgamated in section 6

The glacial–terrestrial–fluvial pathway: A multiparametrical analysis of spatiotemporal dissolved organic matter variation in three catchments of Lake Nam Co, Tibetan Plateau

The Tibetan Plateau (TP) is a sensitive alpine environment of global importance, being Asia's water tower, featuring vast ice masses and comprising the world's largest alpine grasslands. Intensified land-use and pronounced global climate change have put pressure on the environment of the TP. We studied the tempo-spatial variability of dissolved organic matter (DOM) to better understand the fluxes of nutrients and energy from terrestrial to aquatic ecosystems in the TP. We used a multiparametrical approach, based on inorganic water chemistry, dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) characteristics (chromophoric DOM, fluorescence DOM and δ13C of DOM) in stream samples of three catchments of the Nam Co watershed and the lake itself. Satellite based plant cover estimates were used to link biogeochemical data to the structure and degradation of vegetation zones in the catchments. Catchment streams showed site-specific DOM signatures inherited from glaciers, wetlands, groundwater, and Kobresia pygmaea pastures. By comparing stream and lake samples, we found DOM processing and unification by loss of chromophoric DOM signatures and a change towards an autochthonous source of lake DOM. DOM diversity was largest in the headwaters of the catchments and heavily modified in terminal aquatic systems. Seasonality was characterized by a minor influence of freshet and by a very strong impact of the Indian summer monsoon on DOM composition, with more microbial DOM sources. The DOM of Lake Nam Co differed chemically from stream water samples, indicating the lake to be a quasi-marine environment in regards to the degree of chemical modification and sources of DOM. DOM proved to be a powerful marker to elucidate consequences of land use and climatic change on biogeochemical processes in High Asian alpine ecosystems

Linkages between Atmospheric Circulation, Weather, Climate, Land Cover and Social Dynamics of the Tibetan Plateau

The Tibetan Plateau (TP) is an important landmass that plays a significant role in both regional and global climates. In recent decades, the TP has undergone significant changes due to climate and human activities. Since the 1980s anthropogenic activities, such as the stocking of livestock, land cover change, permafrost degradation, urbanization, highway construction, deforestation and desertification, and unsustainable land management practices, have greatly increased over the TP. As a result, grasslands have undergone rapid degradation and have altered the land surface which in turn has altered the exchange of heat and moisture properties between land and the atmosphere. But gaps still exist in our knowledge of land-atmosphere interactions in the TP and their impacts on weather and climate around the TP, making it difficult to understand the complete energy and water cycles over the region. Moreover, human, and ecological systems are interlinked, and the drivers of change include biophysical, economic, political, social, and cultural elements that operate at different temporal and spatial scales. Current studies do not holistically reflect the complex social-ecological dynamics of the Tibetan Plateau. To increase our understanding of this coupled human-natural system, there is a need for an integrated approach to rendering visible the deep interconnections between the biophysical and social systems of the TP. There is a need for an integrative framework to study the impacts of sedentary and individualized production systems on the health and livelihoods of local communities in the context of land degradation and climate change. To do so, there is a need to understand better the spatial variability and landscape patterns in grassland degradation across the TP. Therefore, the main goal of this dissertation is to contribute to our understanding of the changes over the land surface and how these changes impact the plateau\u27s weather, climate, and social dynamics. This dissertation is structured as three interrelated manuscripts, which each explore specific research questions relating to this larger goal. These manuscripts constitute the three primary papers of this dissertation. The first paper documents the significant association of surface energy flux with vegetation cover, as measured by satellite based AVHRR GIMMS3g normalized difference vegetation index (NDVI) data, during the early growing season of May in the western region of the Tibetan Plateau. In addition, a 1°K increase in the temperature at the 500 hPa level was observed. Based on the identified positive effects of vegetation on the temperature associated with decreased NDVI in the western region of the Tibetan Plateau, I propose a positive energy process for land-atmosphere associations. In the second paper, an increase in Landsat-derived NDVI, i.e., a greening, is identified within the TP, especially during 1990 to 2018 and 2000 to 2018 time periods. Larger median growing season NDVI change values were observed for the Southeast Tibet shrublands and meadows and Tibetan Plateau Alpine Shrublands and Meadows grassland regions, in comparison to the other three regions studied. Land degradation is prominent in the lower and intermediate hillslope positions in comparison to the higher relative topographic positions, and change is more pronounced in the eastern Southeast Tibet shrublands and meadows and Tibetan Plateau Alpine Shrublands and Meadows grasslands. Geomorphons were found to be an effective spatial unit for analysis of hillslope change patterns. Through the extensive literature review presented in third paper, this dissertation recommends using critical physical geography (CPG) to study environmental and social issues in the TP. The conceptual model proposed provides a framework for analysis of the dominant controls, feedback, and interactions between natural, human, socioeconomic, and governance activities, allowing researchers to untangle climate change, land degradation, and vulnerability in the Tibetan Plateau. CPG will further help improve our understanding of the exposure of local people to climate and socio-economic and political change and help policy makers devise appropriate strategies to combat future grassland degradation and to improve the lives and strengthen livelihoods of the inhabitants of the TP

Understanding changes in the water budget driven by climate change in cryospheric-dominated watershed of the northeast Tibetan Plateau, China

Glacial retreat and the thawing of permafrost due to climate warming have altered the hydrological cycle in cryospheric-dominated watersheds. In this study, we analysed the impacts of climate change on the water budget for the upstream of the Shule River Basin on the northeast Tibetan Plateau. The results showed that temperature and precipitation increased significantly during 1957–2010 in the study area. The hydrological cycle in the study area has intensified and accelerated under recent climate change. The average increasing rate of discharge in the upstream of the Shule River Basin was 7.9 × 10 6  m 3 /year during 1957–2010. As the mean annual glacier mass balance lost −62.4 mm/year, the impact of glacier discharge on river flow has increased, especially after the 2000s. The contribution of glacier melt to discharge was approximately 187.99 × 10 8  m 3 or 33.4% of the total discharge over the study period. The results suggested that the impact of warming overcome the effect of precipitation increase on run-off increase during the study period. The evapotranspiration (ET) increased during 1957–2010 with a rate of 13.4 mm/10 years. On the basis of water balance and the Gravity Recovery and Climate Experiment and the Global Land Data Assimilation System data, the total water storage change showed a decreasing trend, whereas groundwater increased dramatically after 2006. As permafrost has degraded under climate warming, surface water can infiltrate deep into the ground, thus changing both the watershed storage and the mechanisms of discharge generation. Both the change in terrestrial water storage and changes in groundwater have had a strong control on surface discharge in the upstream of the Shule River Basin. Future trends in run-off are forecasted based on climate scenarios. It is suggested that the impact of warming will overcome the effect of precipitation increase on run-off in the study area. Further studies such as this will improve understanding of water balance in cold high-elevation regions

Changes and driving forces analysis of alpine wetlands in the first meander of the Yellow River based on long-term time series remote sensing data

IntroductionAs a vital component of the ecosystem of the Qinghai-Tibet Plateau, alpine wetlands coexist with their vulnerability, sensitivity, and abundant biodiversity, propelling the material cycle and energy flux of the entire plateau ecosystem. In recent decades, climate change and human activities have significantly altered the regional landscape. Monitoring and assessing changes in the alpine wetlands on the Qinghai-Tibet Plateau requires the efficient and accurate collection of long-term information.MethodsHere, we interpreted the remote sensing data of the first meander of the Yellow River of alpine wetlands from 1990 to 2020 based on Google Earth Engine (GEE) platform, using geographic information system (GIS) and landscape pattern index to analyze the spatial and temporal evolution of wetland landscape patterns, and the primary drivers of changes in wetland area were explored by GeoDetector.ResultsOur result showed that most wetland areas were found in regions with gradients less than 12° and elevations between 3315 and 3600 m. From 1990 to 2010, the area of alpine wetland in the study area decreased by 25.43%. During the period between 2010 and 2020 to the 1990s, the wetland area decreased by 322.9 km2. Conversion to and from grassland was the primary form of wetland transfer out and in, respectively. The overall migration of the wetland centroid in the study area was to the southwest between 1990 and 2010 and to the north between 2010 and 2020. The geometry of the wetland landscape was relatively simple, the landscape was relatively intact, and patches retained a high level of agglomeration and connectivity. However, their level of agglomeration and connectivity was disrupted. A quantitative analysis of the factor detector in GeoDetector revealed that the DEM, slope, and evaporation were the most important driving factors influencing the change of wetland area, with socioeconomic development also influencing changes in the wetland area to a lesser extent.DiscussionUsing interaction detectors, it was discovered that the interaction of various driving factors could better explain the long-term variations in wetland areas, with a greater degree of explanation than that of each driving factor alone

Climate change impact on the hydrological functioning of mountain lakes: a conceptual framework

Mountain lakes are distinctive water bodies that attract the great attention of researchers. They not only serve as a crucial water resource for the inhabitants of the upland regions but also as an important destination for millions of tourists who are attracted by the beauty of these water bodies. With the increasing concern about global warming, mountain lakes are experiencing changes in their hydrological processes and meanwhile can act as reflectors of those changes. Specifically, due to the fragility of these water bodies, understanding the consequences is significant as it can help to find out whether climate change causes degradations in lake hydrological functioning. The interactions of hydrological processes in mountain lakes with external drivers are usually hard to explain explicitly owing to their complexity. To deal with that problem, scholars tend to use conceptual frameworks, which help to reveal the dependence of a lake on particular hydrologic factors. To identify factors influencing lake hydrological function and their sensitivity to changing climate, a literature analysis was undertaken. The focus was on the Canadian Rocky Mountains where 5155 water bodies were identified using GIS. The main literature sources used to identify factors influencing lake hydrologic function were peer-reviewed articles and books. In total, 10 natural drivers critical for lake hydrological function and 2 main reflectors of climate change impacts on mountain lakes as well as 38 additional sub-factors that characterize each of the factors and reflectors, were identified. Based on that, a conceptual framework for mountain lake hydrological functioning was developed. The major problem that affected the thorough testing of the conceptual framework was a limited number of observations across lakes in the research area. Nevertheless, the conceptual framework is flexible and might be tested across many mountainous regions worldwide that experience climatic changes. Such an opportunity can be realized through the use of quantitative statistical techniques available for large datasets. Overall, the conducted research stresses the problem of a poor degree of hydrological exploration of lakes in mountain regions and presents a useful approach to represent complex interactions of natural drivers and intra-lake processes under rising temperatures

Insights into mountain wetland resilience to climate change: An evaluation of the hydrological processes contributing to the hydrodynamics of alpine wetlands in the Canadian Rocky Mountains

Hydrological conditions play an important role in provisioning the exceptionally valuable ecosystem services and functions of wetlands. In alpine areas, wetland functions and services are expected to be very sensitive to climate-mediated changes in hydrology. However, few field studies of alpine wetland hydrology currently exist, thus limiting understanding of how wetlands will respond to warming and drying, and how their ecosystem services and functions will change. This study examines key processes contributing to the hydrological stability of alpine wetlands in Banff National Park, AB, Canada. During the two-year study, snowmelt timing differed by over three weeks, allowing for the examination of water table patterns under comparatively wet and dry conditions. Contrary to expectations, water table positions were relatively stable in each study year, particularly in the peat-bearing soils. Hydrophysical and hydrochemical data together provide evidence that the observed stability is in part due to groundwater contributions, which made up as much as 53% of the water budget in one peatland. Soil conditions also appear to play a role in stabilizing water table regimes. The results suggest that alpine wetlands, and peatlands in particular, may be more resilient to changes in climate than currently thought. Mineral wetlands, comparatively, may have limited adaptive capacity