Glacier outlines in the Ala Archa valley, Kyrgyzstan between 1968-2017

The inventory contains shapefiles of the glacier area in the Ala Archa valley for the years 1968, 1975, 1994, 2010 and 2017. The Ala Archa valley lies in the Kyrgyz Ala-Too (Kyrgyz range) which represents the north-western part of the Tien Shan. The area is very important for scientific research and the freshwater supply for the greater Bishkek region, as it lies in the vicinity of Bishkek, the capital of Kyrgyzstan. The Mapping of the glaciers was conducted based on declassified satellite imagery obtained from the USGS for the days 19/08/1968, 11/07/1975 and Landsat imagery for the days 01/09/1994, 28/08/2010 and 31/08/2017. The satellite images were carefully selected in order to find cloud cover-free images in the summer months (July-Aug-Sept). The classification of the glaciers is based on the normalized difference snow index (NDSI) method and was enhanced manually

Response of water fluxes and biomass production to climate change in permanent grassland soil ecosystems

Effects of climate change on the ecosystem productivity and water fluxes have been studied in various types of experiments. However, it is still largely unknown whether and how the experimental approach itself affects the results of such studies. We employed two contrasting experimental approaches, using high-precision weighable monolithic lysimeters, over a period of 4 years to identify and compare the responses of water fluxes and aboveground biomass to climate change in permanent grassland. The first, manipulative, approach is based on controlled increases of atmospheric CO2 concentration and surface temperature. The second, observational, approach uses data from a space-for time substitution along a gradient of climatic conditions. The Budyko framework was used to identify if the soil ecosystem is energy limited or water limited. Elevated temperature reduced the amount of non-rainfall water, particularly during the growing season in both approaches. In energy-limited grassland ecosystems, elevated temperature increased the actual evapotranspiration and decreased aboveground biomass. As a consequence, elevated temperature led to decreasing seepage rates in energy-limited systems. Under water-limited conditions in dry periods, elevated temperature aggravated water stress and, thus, resulted in reduced actual evapotranspiration. The already small seepage rates of the drier soils remained almost unaffected under these conditions compared to soils under wetter conditions. Elevated atmospheric CO2 reduced both actual evapotranspiration and aboveground biomass in the manipulative experiment and, therefore, led to a clear increase and change in seasonality of seepage. As expected, the aboveground biomass productivity and ecosystem efficiency indicators of the water-limited ecosystems were negatively correlated with an increase in aridity, while the trend was unclear for the energy-limited ecosystems. In both experimental approaches, the responses of soil water fluxes and biomass production mainly depend on the ecosystems’ status with respect to energy or water limitation. To thoroughly understand the ecosystem response to climate change and be able to identify tipping points, experiments need to embrace sufficiently extreme boundary conditions and explore responses to individual and multiple drivers, such as temperature, CO2 concentration, and precipitation, including non-rainfall water. In this regard, manipulative and observational climate change experiments complement one another and, thus, should be combined in the investigation of climate change effects on grassland

Response of water balance components to climate change in permanent grassland soil ecosystems

Abstract. Hydrological processes are affected by changing climatic conditions. In grassland areas, changes in the ecosystem water balance components will alter aboveground biomass production (AGB), which in turn is of great importance for ecological and economic benefits of grassland. However, the effects of climate change on the ecosystem productivity and water fluxes are often derived from climate change experiments. It is still largely unknown whether and how the experimental approach itself affects the results of such studies. The aim of this investigation was to identify the effects of climate change on the water balance and the productivity of grassland ecosystems by comparing results of two contrasting approaches of climate change experiments. The first (manipulative) climate change approach uses increased atmospheric CO2 concentrations and surface temperatures. The second (observational) approach uses data from a space-for-time substitution approach along a gradient in climatic conditions. The climate change effects on the ecosystem’s water balance was determined by using high-precision weighable monolithically lysimeters at each site over a period of four years, including the exceptionally dry year 2018. The aridity index, defined as the grass-reference evapotranspiration (ET0) to precipitation (P), was used to characterize the hydrological status of the regime (i.e. energy- or water limited system). The observational approach (grassland ecosystem moved to a drier and warmer site), resulted in a large decrease of precipitation (P) and non-rainfall water (NRW), an increase in actual evapotranspiration (ETa) and upward directed water fluxes from deeper soil and hence a decline of seepage water as well a decrease in AGB and water use efficiency (WUE). The manipulative approach (grassland ecosystem treated in place) resulted in decreasing P and NRW under conditions of elevated temperature but responded with increasing NRW for elevated CO2 as compared to the reference. Similarly, an elevated CO2 and heating increased the ecosystem’s water loss by ETa. However, the effect of increasing CO2 on ETa was largely compensated by the opposite effect of an elevated temperature in the combined treatment. The seepage water rate also increased with elevated CO2, whereas it clearly decreased for the heating treatment as compared to the reference. All treatments led to a reduction of the grassland productivity in terms of the AGB and to reduced WUE as compared to the grassland ecosystem under reference conditions. The consideration of changes in NRW and P by the treatments needs to be considered in climate change experiments to avoid an over- (elevated temperature) or underestimation (elevated CO2) of the effects of climate change on ecosystems response, especially for sites where water limitation plays a role. The impact of drought periods on seepage rates (potentially leading to groundwater recharge) was more pronounced for the relatively humid site with a longer ETa period without water stress than for a relatively dry site. The hydroclimatological and ecohydrological indicators were similarly affected by changes in temperature, atmospheric CO2 concentrations, and precipitation in both manipulative and observational climate change experiments except for the responses of ETa and AGB in the dry and warm year 2018. The resulting response differences between the two climate change approaches were explained by the actual soil moisture status. The results suggest that energy limited ecosystems tend to increase their ETa and AGB production (excluding effects from elevated CO2 and temperature), but water limited ecosystems respond with a decrease in ETa as a result of water stress, which leads to a clear decline of AGB. The results also suggest that climate change experiments should account for the possible change of the hydrological status of the ecosystem and impose sufficiently extreme levels of climatic conditions within their set-up to allow such changes to occur for capturing the full response of the ecosystem. The results may help to better understanding the impact of climate change on future ecosystem functioning