Sensitivity of forest composition and productivity to climate change in mixed broadleaved-Korean pine forest of Northeastern China

Abstract

Temperate forest is one of the largest forest biomes and is undergoing remarkable shifts in forest composition and ecosystem productivity under warming climates. However, there are considerable uncertainties when predicting future dynamics of temperate forest ecosystems partly because of the uncertainties in future climate predictions. Sensitivity analysis provides an effective mean to evaluate the uncertainties in the predicted forest responses to climate change. Here we evaluated the sensitivity of forest composition and productivity to climate change in the mixed broadleaved-Korean pine forest, a keystone temperate forest type in northeast China. In this study, we used a process-based forest dynamic model, FORMIND, to simulate and predict the response of the mixed broadleaved-Korean pine forest under climate change based on plant functional types (PFTs), and we performed model calibration using forest investigation. We then designed a factorial experiment to quantify the sensitivity to temperature and precipitation of forest composition and ecosystem productivity. Results showed that the uncertainty in future climate predictions could result in divergent responses of forest composition and ecosystem productivity to climate change over the 21st century. The response of PFTs to climate (temperature and precipitation) varied in terms of aboveground biomass. Both shade-tolerant and shade-intolerant PFTs exhibited higher sensitivity (>80% for most of the PFTs) to temperature than precipitation, yet they responded oppositely to climate warming with shade-tolerant PFTs generally increasing but shade-tolerant PFTs decreasing. Moderate shade-tolerant PFTs showed higher precipitation sensitiveness (>50%). Such differences in response and sensitivity of PFTs to climate change are related to PFTs’ competitiveness. Ecosystem productivity exhibited a higher sensitivity (≥50%) to temperature than to precipitation. There was more increase in ecosystem respiration than gross primary productivity (GPP) under warming climate, leading to a decrease in carbon sequestration and net ecosystem exchange (NEE). Our study addresses the importance of evaluating the sensitivity of a forest ecosystem model to climate change, which is relatively less studied. The insight from the study may help design effective forest management strategies to cope with future climate change.