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Schlagwörter:
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Zusammenfassung:
Water resources play a vital role in ecosystem stability, human survival, and social
development in drylands. Human activities, such as afforestation and irrigation, have had a large
impact on the water cycle and vegetation in drylands over recent years. The Badain Jaran Desert (BJD)
is one of the driest regions in China with increasing human activities, yet the connection between
human management and the ecohydrology of this area remains largely unclear. In this study, we
firstly investigated the ecohydrological dynamics and their relationship across different spatial scales
over the BJD, using multi-source observational data from 2001 to 2014, including: total water storage
anomaly (TWSA) from Gravity Recovery and Climate Experiment (GRACE), normalized difference
vegetation index (NDVI) from Moderate Resolution Imaging Spectroradiometer (MODIS), lake extent
from Landsat, and precipitation from in situ meteorological stations. We further studied the response
of the local hydrological conditions to large scale vegetation and climatic dynamics, also conducting a
change analysis of water levels over four selected lakes within the BJD region from 2011. To normalize
the effect of inter-annual variations of precipitation on vegetation, we also employed a relationship
between annual average NDVI and annual precipitation, or modified rain-use efficiency, termed
the RUEmo. A focus of this study is to understand the impact of the increasing planted vegetation
on local ecohydrological systems over the BJD region. Results showed that vegetation increases
were largely found to be confined to the areas intensely influenced by human activities, such as
croplands and urban areas. With precipitation patterns remaining stable during the study period,
there was a significant increasing trend in vegetation greenness per unit of rainfall, or RUEmo over
the BJD, while at the same time, total water storage as measured by satellites has been continually
decreasing since 2003. This suggested that the increased trend in vegetation and apparent increase in
RUEmo can be attributed to the extraction of ground water for human-planted irrigated vegetation.
In the hinterland of the BJD, we identified human-planted vegetation around the lakes using MODIS
observations and field investigations. Four lake basins were chosen to validate the relationship
between lake levels and planted vegetation. Our results indicated that increasing human-planted
vegetation significantly increased the water loss over the BJD region. This study highlights the value
of combining observational data from space-borne sensors and ground instruments to monitor the
ecohydrological dynamics and the impact of human activities on water resources and ecosystems over the drylands.
