Forest Ecosystems (Apr 2025)
Sensitivity of gross primary production and evapotranspiration to heat and drought stress in a young temperate plantation in northern China
Abstract
Assessing the sensitivities of ecosystem functions to climatic factors is essential to understanding the response of ecosystems to environmental change. Temperate plantation forests contribute to global greening and climate change mitigation, yet little is known as to the sensitivity of gross primary production (GPP) and evapotranspiration (ET) of these forests to heat and drought stress. Based on near-continuous, eddy-covariance and hydrometeorological data from a young temperate plantation forest in Beijing, China (2012–2019), we used a sliding-window-fitting technique to assess the seasonal and interannual variation in ecosystem sensitivity (i.e., calculated slopes, SGPP-Ta, SET-Ta, SGPP-EF, and SET-EF) in GPP and ET to anomalies in air temperature (Ta) and evaporative fraction (EF). The EF was used here as an indicator of drought. Seasonally, daily SGPP-Ta, SET-Ta, and SGPP-EF were greatest in summer, reaching maxima of 1.12 ± 0.56 g C·m−2·d−1⋅°C−1, 1.36 ± 0.56 g H2O·m−2·d−1⋅°C−1, and 0.37 ± 0.35 g C·m−2·d−1, respectively. Evapotranspiration was constrained by drought, especially during the spring-to-summer period, SET-EF reaching −0.51 ± 0.34 g H2O·m−2·d−1. Variables EF, Ta, soil water content (SWC), vapor pressure deficit (VPD), and precipitation (PPT) were the main controls of sensitivity, with SGPP-Ta and SET-Ta increasing with Ta, VPD, and PPT (<50 mm·d−1) during both spring and autumn. Increased drought stress during summer caused the positive response in GPP and ET to decrease with atmospheric warming. Variable SET-EF intensified (i.e., became more negative) with decreasing EF and increasing Ta. Interannually, annual SGPP-Ta and SET-Ta were positive, SGPP-EF near-neutral, and SET-EF negative. Interannual variability in SGPP-Ta, SET-Ta, SET-EF, and SGPP-EF was largely due to variations in bulk surface conductance. Our study suggests that the dynamics associated with the sensitivity of ecosystems to changes in climatic factors need to be considered in the management of plantation forests under future global climate change.
