我国荒漠植被生产力动态及其与水热因子的关系

为了探讨近30 a来我国干旱区荒漠植被的净初级生产力(NPP)及其与水热因子相关性随时间的变化，运用CASA(Carnegie Ames Stanford approach)模型估算我国荒漠植被1982—2015年生长季的NPP，并运用线性回归和GIS空间分析方法分析了NPP的时空变化特征，利用滑动相关系数分析了荒漠植被NPP与水热因子的关系。结果表明：① 单位面积NPP均值为42 g·m^-2·a^-1，NPP整体水平较低。空间上呈西北部、东部边缘较高，中部、南部和中东部较低的分布特征。② 荒漠植被NPP年均总量为5.783×1013g·a^-1。从荒漠植被NPP的年际变化来看，1982—2015年中国荒漠植被NPP总量以1.64×1012g·(10a)^-1的线性速率（P=0.054）上升，荒漠植被生长状况总体上不断改善，但总量趋势呈现阶段性变化，1982—1993年荒漠植被NPP总量呈极显著增长态势（1.25×1012 g·a^-1，P<0.01）； 1993—2006年NPP总量呈极显著降低态势（-6.42×1011 g·a^-1，P<0.01）； 2006—2015年NPP总量缓慢增长（1.70×1011 g·a^-1，P>0.05）。从空间变化来看，47.65%的荒漠植被NPP呈增加态势，主要分布在阿拉善高原、天山北麓、塔里木盆地西部边缘、柴达木盆地的东南边缘、阿尔金山南麓和昆仑山脉。③ 从荒漠植被NPP与各气候因子之间的相关关系随时间的变化来看，NPP与气温的滑动相关系数随时间的变化保持为负相关，与降水、干燥度的滑动相关系数保持为正相关，与太阳总辐射的滑动相关系数随时间变化并未表现出显著的变化趋势。总体上，荒漠植被与水热因子的相关关系在研究时段均有进一步减弱的态势，即荒漠植被NPP对气候因子的变化愈来愈不敏感。

Dynamic State of Desert Vegetation Productivity andIts Relationship with Water-Heat Factors in China

In this paper, the CASA (Carnegie-Ames-Stanford Approach) model was used to estimate the NPP ofdesert vegetation in its growing season from 1982 to 2015, and the linearregression and GIS spatial analysis methods were applied to analyze the spatiotemporal variation of NPP. The purposesof the study were to explore the net primary productivity of desert vegetationand its correlation with water-heat factors in China’s arid regions in recentthree decades. The sliding correlation coefficient was used to analyze the relationship between NPP and water-heatfactors. The results showed that: ① The average NPP per unit area was 42 g·m^-2·a^-1,and the overall level of NPP was low. Spatially, it was higher in the northwesternand eastern margins but lower in the central, southern and mid-eastern regions; ② The average annual NPP of desert vegetation was 5.78×10¹³ g·a^-1. For the interannual variation, the linear change rate of the total NPP of desert vegetation was1.64×10¹² g·(10a)^-1 (P=0.054)in China from 1982 to 2015, desert vegetation was generally improved, but thetotal change trend was staged. The total amount of NPP showed an extremely significant growthtrend (1.25×10¹² g·a^-1, P<0.01) during the period of1982-1993, it was significantly decreased from 1993 to 2006 (-0.64×10¹² g·a^-1, P<0.01), and increased slowly during the period of 2006-2015(0.17×10¹² g·a^-1, P>0.05). From the perspectiveof spatial change, 47.65% NPP of desert vegetation was in an increase trend, whichwas mainly distributed in the Alashan Plateau, north piedmont of the TianshanMountains, western marginal zone of the Tarim Basin, southeastern marginal zoneof the Qaidam Basin, south piedmont of the Altun Mountains, and KunlunMountains; ③ From theperspective of the change of correlation betweendesert vegetation NPP and climatic factors with the time, the slidingcorrelation coefficient between NPP and temperature was negatively correlated with the time, but positively correlated between NPP andprecipitation and dryness. There was no significant variation of slidingcorrelation coefficient between NPP and total solar radiation with the time. Ingeneral, the correlation between desert vegetation and water-heat factors wasfurther weakened during the study period, that is, the desert vegetation NPP wasincreasingly insensitive to the change of climatic factors.