1993—2015年中国草地净初级生产力格局及其与水热因子的关系

Net Primary Productivity Pattern of Grassland in China and Its Relationship with Hydrothermal Factors During 1993-2015

[目的]估算1993—2015年中国草地净初级生产力(net primary productivity,NPP),分析其时空变化格局及与水热因子的关系,了解这一时期中国草地生态系统的生产力水平及其对水热因子变化的响应。[方法]基于长时间序列遥感数据,气象数据和植被类型数据,运用CASA模型(Carnegie-AmesStanford Approach)估算草地净初级生产力,利用一元线性回归、二阶偏相关分析以及GIS空间分析方法,探讨草地NPP的变化趋势以及与对水热因子的关系。[结果](1)1993—2015年,中国草地NPP年均总量为7.595×10^(14) g(以C计),单位面积NPP均值为296.76g/m^2/a。总体上,草地NPP呈现从东部到西部、从南部到北部逐渐减少的空间分布特征。(2)1993—2015年草地NPP总量以-1.415×1012 g/a的线性速率(p>0.05)波动式下降。其中,1993—2010年草地NPP总量以-2.312×10^(12) g/a的线性速率(p<0.05)显著降低,2011—2015年草地NPP总量以7.00×10^(11) g/a的线性速率(p>0.05)波动式上升。1993—2015年,NPP呈减少态势的面积大于NPP呈增加态势的面积且40.40%的草地NPP呈现显著性变化。(3)年际变化上,除去2011年以来草地NPP的波动性变化,草地NPP与太阳总辐射和降水量的二阶偏相关性显著,与年平均气温没有表现出显著的相关关系。空间分布上,草地NPP与太阳辐射显著偏相关的面积>与降水显著偏相关的面积>与气温显著偏相关的面积。[结论]1993—2015年,中国草地NPP总体上呈现普遍降低、局部改善的变化特征。这种变化主要受到太阳总辐射和降水量的影响,受温度变化的影响较弱。

[Objective] To estimate the net primary productivity （NPP） of grassland in China during the period from 1993 to 2015, and analyze the relationship between NPP and hydrothermal factors, in order to understand the productivity of grassland and the impacts of climate change on ecosystems.[Methods] Based on long-term remote sensing data, meteorological data and vegetation type data, we used CASA model （Carnegie-Ames-Stanford approach） to estimate the NPP of grassland in China. The variation of NPP and the responses of NPP to hydrothermal factors were calculated by using one-way linear regression, second-order partial correlation analysis and GIS spatial analysis.[Results] ① The total annual NPP of grassland was 7.60×1014 g （measured in term of carbon）, and the annual average NPP per unit area was 296.76 g/（m2·a）. The NPP of grassland decreased gradually from south to north, and from east to west in China. ② The total NPP of grassland in China decreased undulately with the linear rate of -1.415×1012 g/a （p〉0.05） from 1993 to 2015. The total NPP of grassland decreased significantly at a rate of -2.312×1012 g/a （p〈0.05） from 1993 to 2010, while increased at a rate of 7.00×1011 g/a （p〉0.05） from 2011 to 2015. In total, the area of grassland with decreasing NPP was larger than that with increasing NPP, and the NPP in 40.40% grassland changed significantly. ③ Annually, the second-order partial correlation between NPP and total solar radiation and precipitation was statistically significant, while that between NPP and annual mean temperature was insignificant. In terms of area, the significant partial correlation area between NPP and solar radiation was the biggest, followed by that between NPP and precipitation, and the significant partial correlation area between NPP and annual mean temperature was the smallest.[Conclusion] Grassland NPP in China declined widely while increased locally from 1993 to 2015. This variation was mainly affected by total solar radiation and precipitation.