Decadal drought deaccelerated the increasing trend of annual net primary production in tropical or subtropical forests in southern China.

Wantong Wang,Junhua Yan,Jinxia Wang,Xingzhao Liu,Guoyi Zhou

doi:10.1038/srep28640

Abstract

Previous investigations have identified that the effects of climate change on net primary production (NPP) of global forests have varied both spatially and temporally, and that warming has increased the NPP for many forests. However, other factors, such as available soil water for plant growth, could limit these incremental responses to warming. In our investigation we have quantified the responses of NPP of tropical or subtropical forests in southern China to warming and drought stress over the past three decades (1981 to 2012) using data from five forest research stations and satellite measurements. NPP, mean annual temperature (MAT) and annual days without rainfall showed an increase of 0.076 g C m−2 a−2 (standardized), 0.057 °C a−1 (standardized) and 0.067 d a−1 (standardized) during the study period, respectively. However, incremental NPP was deaccelerated at a rate of approximately 20.8% per decade. This deacceleration was primarily caused by a decrease in available soil water which resulted from warming (mainly occurring in winter and autumn) and the changes in rainfall pattern. The result indicates that intensifying drought stress would limit future increases of forest NPP in southern China.

Highlights

Net primary production (NPP) is an important measure of terrestrial ecosystem functioning[1]
There are still some urgent questions which need to be answered, such as (1) how will the tropical and subtropical evergreen broadleaved forests (TEBF) ecosystems’ NPP changes under such a long-term warming and the consequences of drought stress; and (2) what are the main limiting climate factors affecting NPP in this region, and what impact do they have? In this study, we compiled and analyzed NPP data based on the Advanced Very High Resolution Radiometer (AVHRR) GloPEM NPP data[24] (1981–2000) and the MOD17A3 NPP data[25] (2001–2012), and analyzed the corresponding climatic variables and soil moisture across five forest field research stations in the TEBF (Fig. 1 and Table 1) from 1981 to 2012
The results showed that annual NPP was strongly positively correlated with annual days without rainfall (r = 0.510, P < 0.001) and Mean annual temperature (MAT) (r = 0.508, P < 0.001); whereas it was significantly negatively correlated with mean annual relative humidity (MARH) (r =−0.491, P < 0.001), annual days with small rainfall (r =−0.352, P < 0.001), and the soil water content of the top 50 cm (r =−0.320, P = 0.025)

Summary

Introduction

Net primary production (NPP) is an important measure of terrestrial ecosystem functioning[1]. Zhou et al, investigating TEBF biome changes based on the observations from established permanent plots over the past four decades, reported that TEBF ecosystems have undergone a transition from cohorts with few large individuals to ones with a larger number of smaller individuals. They suggested that these subtropical forests were under threat due to their lack of resilience to these changes[22]. We synthesized the latest findings on the effect of drought stress on TEBF ecosystems and carbon cycling

Methods

Results

Conclusion