2001-2013年中国灌木生态系统净初级生产力的时空变化特征及其对气候变化的响应

Temporal and spatial variation characteristics of China shrubland net primary production and its response to climate change from 2001 to 2013

植被净初级生产力(NPP)是陆地生态系统碳库的主要来源,NPP的变化反映了生态系统对气候变化及土地利用变化的响应。在我国广泛地分布着相当于国土面积20%的灌木林,其NPP在中国陆地生态系统碳平衡过程中发挥着重要作用。该文利用CASA(Carnegie-Ames-Stanford Approach)模型估算了中国6类主要灌木生态系统2001–2013年的NPP,并分析了其季节和年际间的变化趋势及其与气候变化之间的关系。结果显示:中国灌木生态系统的年平均NPP为281.82 g·m^(–2)·a^(–1),其中亚热带常绿灌木年平均NPP最高为420.47 g·m^(–2)·a^(–1),而高寒荒漠灌木半灌木年平均NPP最低为52.65 g·m^(–2)·a^(–1)。在2001–2013年间,中国灌木生态系统的NPP以1.23 g·m^(–2)·a^(–1)的速度显著增加,其相对变化速率达到了5.99%,其中高寒荒漠灌木半灌木、温带荒漠灌木半灌木、温带落叶灌木以及亚热带常绿灌木的NPP都显著增加,温带落叶灌木的NPP增长最快,达到3.05 g·m^(–2)·a^(–1),亚高山常绿灌木则以0.73 g·m^(–2)·a^(–1)的速率显著下降,亚高山落叶灌木则无显著变化趋势。不同灌木生态系统的NPP对不同季节气候变化的响应不同,但总体上中国灌木生态系统NPP的变化更多受到降水变化的影响,此外,春季气温升高也对NPP的增加起到积极的促进作用。

Aims Net primary production（NPP） is the input to terrestrial ecosystem carbon pool.Climate and land use change affect NPP significantly.Shrublands occupy more than 20% of the terrestrial area of China,and their NPP is comparable to those of the forests.Our objective was to estimate China shrubland NPP from 2001 to 2013,and to analyze its variation and response to climate change.Methods We used a Carnegie-Ames-Stanford Approach（CASA） model to estimate the NPP of six shrubland types in China from 2001 to 2013.Furthermore,we used Theil-Sen slope combined with Mann-kendall test to analyze its spatial variation and a linear regression of one-variable model to analyze its inter-and intra-annual variation.Finally,a multi-factor linear regression model was used to analyze its response to climate change.Important findings We found the annual mean NPP of China shrubland was 281.82 g·m^–2·a^–1.The subtropical evergreen shrubland has the maximum NPP of 420.47 g·m^–2·a^–1,while the high cold desert shrubland has the minimum NPP of 52.65 g·m^–2·a^–1.The countrywide shrublands NPP increased at the rate of 1.23 g·m^–2·a^–1,the relative change rate was 5.99%.The temperate deciduous shrubland NPP increased the fastest with a speed of 3.05 g·m^–2·a^–1 and subalpine evergreen shrubland had a decreasing trend with a speed of –0.73 g·m^–2·a^–1.Moreover,the other four shrublands NPP had a growing trend,only subalpine deciduous shrubland NPP did not change significantly.The response of NPP to climate change of different seasons varies to different shrubland types.In general,the NPP variation was mainly affected by precipitation,and the spring warming also contributed to it.The increase of countrywide shrubland NPP may promote its contribution to the regional ecosystem function.