全球森林生态系统净初级生产力的空间格局及其区域特征

净初级生产力（Net Primary Productivity）是生态系统碳循环过程中的一个重要组成部分，森林生态系统的NPP占全球陆地生态系统的65%，深入了解全球森林生态系NPP的空间变异规律，是理解全球碳收支格局的基础。本论文以收集获得的野外站点实测NPP数据为基础，对全球森林生态系统NPP的空间分布格局及其区域特征进行综合分析得出：全球森林生态系统的NPP呈现出随着纬度升高而降低的趋势，北半球森林生态系的NPP随着纬度的升高显著降低，南半球森林生态系统的NPP则纬向规律不显著。全球各个大洲之间森林生态系统的NPP整体上差异不显著，只有南美洲森林生态系统的NPP显著高于亚洲、欧洲和北美洲的森林生态系统。全球森林生态系统的NPP呈现出从寒冷性气候区域向温暖性气候区域逐渐增大的趋势。经典的Miami模型能够较合理地估算当前气候条件下森林生态系统NPP的空间分布格局。在全球尺度上，年均温（r2约为0.50）较年降水（r2约为0.40）与森林生态系统的NPP有更强的相关性。这些研究结果为进一步探讨全球陆地生态系统碳源汇功能奠定了一定的基础。

SPATIAL PATTERN AND REGIONAL CHARACTERISTICS OF GLOBAL FOREST ECOSYSTEM NET PRIMARY PRODUCTIVITY

NPP(Net primary productivity) is one of the most important components of the ecosystem carbon cycle. Forest ecosystem NPP accounts for 65% of global terrestrial ecosystem NPP. It is significant for understanding the world carbon budget to research the spatial variation of forest ecosystem NPP on a global scale. In this paper, we collected data on the NPP of global forest ecosystem derived from field measurements during five decades(1961~2008). A total of 711 NPP measured sites were included, in which 142 sites from the forest ecosystem database developed by Luyssaert et al., 514 sites from the doctoral dissertation by Luo Tianxiang, and 55 sites from other published papers. These NPP measured sites were distributed across Asia(564 sites), Europe(47 sites), North-America(66 sites), South-America(25 sites), Oceania(7 sites)and Africa(2 sites), spanning from 37.42°S to 66.37°N in latitude, and from 156.25°W to 167.15°E in longitude. These sites in six climate zones:tropical(26 sites), subtropical(337 sites), temperate(209 sites), boreal(69 sites), polar(18 sites)and alpine(52 sites)zones. Then, we analyzed spatial patterns and regional characteristics of global forest ecosystem NPP. The results indicated that: 1)On a global scale, the NPP of forest ecosystem showed markedly decreasing trend with an increase in latitude, decreasing by 11.05g C/m2/a with 1°increase of latitude. In the North Hemisphere, forest NPP displayed similar latitudinal patterns, decreasing by 11.71g C/m2/a with 1°N increase of latitude. However, in the South Hemisphere, it showed weak variation trend with latitudinal gradients 2)There was no significant difference of forest ecosystem NPP among Asia, Europe and North-America. Only forest ecosystem NPP in the South-America(921±379g C/m2/a)was notably higher compared with other continents(650±300g C/m2/a in Asia, 651±270g C/m2/a in Europe, and 589±260g C/m2/a in North-America) 3)Forest ecosystem NPP tended to decrease from warm climate zones to cold climate zones. It was largest in the tropical zone(1078±340g C/m2/a)notably higher than in other climate zones, whereas smallest in the polar zone(367±167g C/m2/a)notably lower than in other climate zones 4)It was reasonable to estimate global forest ecosystem NPP under current climate conditions using the classic Miami model 5)Mean annual temperature (r2 about 0.50)was better correlated with forest ecosystem NPP than mean annual precipitation(r2 about 0.40)on a global scale. These research results are helpful to discussing the carbon sink/source of terrestrial ecosystem further.