Dryland ecosystem processes

Trees store carbon fixed through photosynthesis as nonstructural carbohydrates (NSCs). When current carbon assimilation is limited, these carbon reserves can be remobilized to support respiration, growth, and survival. This stored carbon thus plays an important role in helping trees withstand and recover from drought. However, it remains unclear how trees store and remobilize NSCs in response to drought. 

Radiocarbon (¹⁴C) techniques are powerful tools for studying carbon cycling. Atmospheric ¹⁴C concentrations increased sharply following nuclear weapons testing in the 1950s and 1960s and have since declined over time. Trees incorporate this atmospheric ¹⁴C signal through photosynthesis and retain it in their tissues. By comparing the ¹⁴C content of stored carbon with the historical atmospheric ¹⁴C record, we can estimate its age and infer how long it has been stored and how rapidly carbon pools turn over within the tree.

The long-term irrigation experiment at Pfynwald forest in southern Switzerland includes control, irrigation, and irrigation-stop treatments, which provide contrasting water histories and are associated with distinct carbon source–sink dynamics, as reflected in differences in photosynthesis, respiration, and growth. In this study, we investigate how these contrasting conditions affect carbon storage and remobilization in Scots pine (Pinus sylvestris) by analysing radiocarbon (¹⁴C) signatures in trees.

We further assess how the patterns observed under these long-term treatments differ from the short-term responses induced by the newly established VPD and drought treatments.

Link to the main project “Ecosystem Processes in Arid Regions” at the Max Planck Institute.