中国西南喀斯特地区植被变化时空特征及其成因

2000年以来,国家在中国西南喀斯特地区开展一系列生态治理工程,该地区退化生态系统得到一定程度的恢复,而2008年开展石漠化综合治理工程以来该地区的植被覆盖和生产力如何变化尚不清楚。本研究利用遥感增强型植被指数(EVI)和总初级生产力(GPP)数据,研究2000—2015年西南喀斯特地区植被EVI年均值和GPP年总量的时空变化特征,重点探讨2008年以来石漠化综合治理工程、气候变化等因素对植被覆盖及生长的影响,进而评估石漠化综合治理工程的成效。结果表明,2000—2015年西南喀斯特地区植被EVI总体显著增加,其中2008—2015年植被EVI均值和变化率分别比2000—2007年高6.9%和85.7%,EVI显著增加的区域占西南喀斯特地区的13.4%;该区域GPP年总量亦呈显著增加趋势(20.58 g C m-2a-1)。2008—2015年气温和降水对植被EVI变化趋势的贡献仅占28.3%,退耕还林还草等生态恢复措施、大气CO2浓度、大气氮沉降的增加可能是该区域植被覆盖显著增加的主要贡献因子。在100个首批石漠化综合治理试点县中,大部分试点县植被EVI的变化趋势受非气候因子的影响,其中治理面积大的县受非气候因子的影响显著高于治理面积小的县,表明石漠化综合治理工程的实施有效地促进了试点县植被覆盖的增加。

Spatial and temporal patterns of changing vegetation and the influence of environmental factors in the karst region of Southwest China

Degraded ecosystems in the karst region of Southwest China have been restored to some extent through a series of ecological conservation projects that started in 2000. However, changes in vegetation during the ongoing rocky desertification control projects occurring in this region since 2008 are not well understood. In this study, we used an enhanced vegetation index (EVI) and gross primary productivity (GPP) derived from remote sensing data to investigate the temporal and spatial patterns of EVI and GPP during 2000-2015. Particularly, we focus on changes since 2008 and the responses of vegetation trends to multiple environmental factors in this region. Results show that the annual EVI increased drastically between 2000 and 2015. In particular, the mean and increasing trend of EVI in 2008-2015 was larger than in 2000-2007 by 6.9% and 85.7%, respectively. Ecosystems with significant increase in EVI accounted for 13.4% of the study area in 2008-2015, where annual GPP also increased remarkably with an average growth rate of 20.58 gC m^-2 a^-1. The contributions of temperature and precipitation to increase in EVI were 28.3%. Land cover changes due to the rocky desertification control projects and increase in atmospheric carbon dioxide and atmospheric nitrogen deposition could be the major factors causing increase in EVI. Furthermore, when we divided the 100 pilot counties in the first stage of the rocky desertification control projects into four groups according to their total area of conservation, the EVI trend attributed to non-climatic factors differed significantly among the four groups. Counties with higher conservation efforts had a larger EVI attributed to non-climatic factors, which indicated that the rocky desertification control projects play an important role in increasing vegetation cover.