Signatures of plant water stress in the near surface air: How is the diurnal temperature range related to ecosystem drought response at a broadleaved forest site?

Water stress shifts the partitioning of turbulent heat fluxes towards sensible heat and therefore leaves an imprint of higher temperatures in the near surface atmosphere during the day (Ghausi et al., 2025), specifically the diurnal temperature range and in relative humidity. This temperature range therefore carries the information of soil water stress, as has been confirmed in global analyses with eddy covarince data (Chauhan et al., in review). Here we investigate how the diurnal temperature range in turn relates to ecosystem indicators of soil water stress at the daily, seasonal and annual time scale at the temperate broadleaved forest site Hohes Holz in the ICOS network (DE-HoH). For this, we apply the same method as described byChauhan et al. and Ghausi et al. 2025, and derive a soil water limitation factor based on the difference between observedand theoretical (non-water limited) diurnal temperature range. We compare this atmospherically-derived soil water limitation factor to the observed ecosystem variables indicating short-term reaction to water stress (reduction in GPP) and long-term integrated water stress (tree growth, δ13C).