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| Home > Publications database > Water and climate feedbacks of common European land use types under warm and dry conditions 2018 |
| Home > Publications database > Water and climate feedbacks of common European land use types under warm and dry conditions 2018 |
| Conference Presentation (After Call) | FZJ-2020-00568 |
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2019
Abstract: The year 2018 was characterized by less precipitation, higher potential evapotranspiration, and a larger sum of growing degree days than usual over large regions of Europe. This provides an opportunity to study the feedbacks to expect more frequently under a changing future climate from a landscape originally equilibrated to cooler and wetter conditions. We here focus on feedbacks related to ecosystem services such as atmospheric heating or cooling, CO2 uptake, and freshwater production. The network of eddy-covariance stations promoted by initiatives like ICOS (www.icos-re.eu) and TERENO (www.tereno.net) is now dense enough to compare these feedbacks between 2018 and previous years. The network spans different locations in Europe that are affected by varying drought intensities and have different land uses such as forest, grassland, crop and wetland. Analysis of these data shows that the sensible heat flux (heating of the atmosphere by the surface) was consistently and considerably larger than usual across the drought-affected sites. Net ecosystem productivity (CO2 uptake) was considerably reduced on average, but not consistently across all drought-affected sites, and latent heat flux (evapotranspiration) was reduced only slightly on average, with a large variability of both positive and negative changes depending on site. Typical factors enhancing the preservation or even increase of evapotranspiration and productivity, included a usually cool and wet climate, a large reservoir of stored soil or surface water, and perennial vegetation. In contrast, water-limited sites or sites characterized by early harvest of crops in 2018 and a bare soil afterwards, tended to show strong reductions in evapotranspiration and productivity. Despite the opposing changes in absolute evapotranspiration, the fraction of precipitation used for evapotranspiration increased clearly across drought-affected sites. Based on these findings and evidence from cropped sites with and without the application of catch crops after harvest, we discuss the potential of land management to modulate ecosystem service responses to increased temperatures and drought and the resulting trade-offs: Maintaining an active plant canopy and thus evapotranspiration mitigates atmospheric warming both locally through smaller sensible heat fluxes and globally through preservation of CO2 uptake. However, this comes at the cost of reduced groundwater recharge and surface water discharge.
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