Enhanced spring phenological temperature sensitivity explains the extension of carbon uptake period in temperate forest protected areas

Abstract

Land surface phenology (LSP) and its trend are important for understanding the vegetation–climate relationship. However, whether LSP and LSP trends for different forest communities vary with the intensity of forest disturbance and the main cause of the change is still unclear. In this study, LSP indicators and their temperature sensitivity (Ts) were obtained for coniferous (Larch Coniferous forests (LC) and Spruce Fir Korean Pine forests (SFKP)), mixed (Broadleaf Korean Pine forests (BKP) and Spruce Fir Broadleaf forests (SFB)), and broadleaf (Aspen White Birch forests (AWB) and White Birch forests (WB)) communities in protected (Fenglin National Natural Reserve, FNNR) and unprotected (Lilin Experimental Forest Farm, LEFF) areas in Northeastern China from remote sensing and climate data. Statistical comparisons of the LSP, LSP trends, and Ts were conducted for various forest communities in both FNNR and LEFF. The results show that the values of mean start of the season (SOS) and mean end of the season (EOS) in FNNR were significantly different from those in LEFF, and the SOS, EOS, and the length of season (LOS) trends for various forest communities in FNNR were significantly different from those in LEFF, except for the SFB. In broadleaf forests, both the mean LOS and LOS trends for various forest communities were significantly higher in FNNR. However, significantly higher LOS but lower LOS trends in FNNR were identified for coniferous and mixed forests. In addition, the SOS Ts for various forest communities in FNNR were significantly higher than those in LEFF, and the Ts for broadleaf forests in FNNR were significantly lower than that in other forest communities. The results of this study suggest that the carbon uptake periods of most temperate forest communities are apparently enhanced by the high spring phenological Ts in protected areas, which provides important insights into future carbon sequestration potential and forest management strategies for temperate forests in Northeastern China.