Forest ecosystems play an essential role in the global water supply (e.g., through hydrological regulation) and carbon (C) sequestration. On the one hand, as a significant C sink, forests store C long-term in biomass. On the other hand, C and water cycle are tightly coupled; this means, forests generally store and sequester C more efficiently than other shorter vegetation (e.g., grass), but also use more water (i.e., through evapotranspiration). This leads to a huge challenge for all stakeholders: How do we manage forests to provide an optimal balance of water supply and C sequestration under a variable climate?
The overall objective of this project is to improve understanding and advance knowledge about the coupling mechanisms between C and water cycles and the response of C and water fluxes to climate variability and extremes.
Forests store C long-term in biomass by capturing CO2 from the atmosphere and increase C stock in soils through the input from organic matters (e.g., deadwood, litter). This high potential attracts much political attention and shifts national strategies to reduce CO2 emission and mitigate climate change by enhancing woody biomass productivity and expanding plantation forests to maximise the capacity of storing C. Recent studies show that actions with an emphasis on increasing biomass productivity and forest cover alter water cycle, deplete soil water, and compromise water supply and soil carbon stock. So, managing forests to enhance carbon sequestration may have a negative impact on water availability for human use through the complex interplay of water and C cycles. This concern is especially acute under global warming that is associated with increasing hot waves and prolonged droughts. An increase in drought stress and a decrease in forest growth may curb C sequestration and threaten regional freshwater supply. This raises uncertainty about the extent to which forests will be able to contribute to climate change mitigation in the long term. While countries such as Germany aim to achieve C-neutrality by 2050, until now, little is known about the consequences of global warming on both C and water fluxes at the national level.
This project is funded by the German Academic Exchange Service (DAAD) (Grant-ID: 57510261).