气候变化与人为活动对三江源草地生产力影响的定量研究

近数十年来在气候变化和生态工程实施的背景下,作为我国重要的生态屏障的三江源地区的气候条件和人为干扰都发生了明显的变化。本研究借助CASA模型和气候生产力模型,结合对土地利用/覆盖变化(LUCC)的分析,定量评估了气候变化、LUCC和草地管理措施对三江源草地净初级生产力(NPP)变化的影响。结果表明,1)2001-2012年间,三江源草地总面积增加了6749 km²,草地的平均NPP下降了5.47%,总NPP下降了5.00%。 2)由新增加的草地带来的NPP总量为1293.12 Gg C,由转出草地带来的NPP总量损失为215.42 Gg C。 3) 2012年气候总NPP比2001年下降了20.27%,而人为总NPP增加了41.51%。12年间气候变化的趋势不利于草地植被的生长,而人为活动对草地植被的负面影响力有明显减弱。4)由气候因素引起的草地总NPP变化量为-165.28 Tg C,而管理措施引起的总NPP变化量为140.03 Tg C; LUCC导致的草地总NPP变化量为2.22 Tg C。草地管理措施的改进对遏制草地退化起到了决定性作用。

Quantitative assessment of relative roles of climate change and human activities on grassland net primary productivity in the Three-River Source Region,China

The Three-River Source Region (TRSR),a region with key importance for the ecological security of China,has been affected by climate change and by changes in human activities driven by a series of ecological restoration projects in recent decades.In this study,we analyzed land use and cover change (LUCC)in the TRSR and the consequent changes in grassland net primary productivity (NPP).For this analysis,we used the CASA (Carnegie-Ames-Stanford Approach)model,a climatic production model,and land use data for the study area from 2001 and 2012,which were derived from the MODIS global land cover product.The contribu-tions of LUCC,land management measures,and climate change to NPP variations were analyzed quantitative-ly.The results showed that,during the 12 years,the net increase in grassland area was 6749 km2 ,and the av-erage NPP and total NPP of grassland decreased by 5 .47% and 5 .00%,respectively.New grassland contribu-ted 1293.12 Gg C (Gg= 109 g)to total NPP,while the loss of grassland led to a decrease of 215.42 Gg C.The climatic total NPP of grasslands decreased by 20.27% and the anthropogenic total NPP increased by 41.51%. These results indicate that climate conditions have negatively affected vegetation growth,whereas human activities have favorably affected vegetation recovery.The contributions of climate change,LUCC,and improved management measures to the variation in total NPP were -165.28 Tg C,2.22 Tg C,and 140.03 Tg C,respectively.Therefore, improving grassland management measures can significantly reduce grassland deterioration due to climate change.