中国东北样带植被净初级生产力时空动态遥感模拟

 中国东北样带(Northeast China Transect, NECT)是中纬度半干旱区的国际地圈-生物圈计划(IGBP)陆地样带之一, 是全球变化研究的 重要手段与热点。该研究应用生态系统碳循环过程CASA(Carnegie-Ames-Stanford Approach)模型分析了NECT从1982~1999年植被净初级生产力 (Net primary productivity, NPP)的时空变异及其影响因子。结果表明, 1) 1982~1999年NECT植被NPP为58 ~ 811 g C·m^–2·a^–1, 平均为426 g C·m^–2·a^–1, 大体上呈现由东向西逐渐递减的趋势; 2)研究时段内NECT的总NPP变异范围是0.218 ~ 0.325 Pg C, 平均为0.270 Pg C (1 Pg = 10¹⁵ g); 3) NECT的总NPP在过去18年内整体呈显著性增加趋势, 其中从1982~1990年样带NPP呈显著性增加趋势, 而后期1991~1999样带NPP没 有显著性变化趋势; 4)沿NECT不同植被类型对气候变化的响应特征是不同的, 在研究时段内, 农田、典型草原和草甸草原表现出最大的NPP增加 量, 而典型草原、荒漠草原对气候变化表现出高的敏感性; 5) NECT植被NPP的空间分布格局是由年降水量的分布格局所决定, 而NPP的时间变异 则由年降水量、年太阳总辐射的变化所影响驱动。

SPATIAL-TEMPORAL VARIATIONS IN NET PRIMARY PRODUCTIVITY ALONG NORTHEAST CHINA TRANSECT (NECT) FROM 1982 TO 1999

Aims Net primary productivity (NPP) and its responses to global climate change have been important issues of global change research. Accurately estimating spatial patterns and temporal dynamics of NPP of terrestrial ecosystems is important to human society and is necessary for understanding the carbon cycle of the terrestrial biosphere. The Northeast China Transect (NECT), one of the International Geosphere-Biosphere Programme terrestrial transects, is an ideal region for identifying effects of climate change on spatial-temporal variations in NPP. Methods We investigated NPP derived from a carbon model (Carnegie-Ames-Stanford Approach, CASA) and its spatial-temporal variations along NECT 1982–1999 time series data sets of normalized difference vegetation index (NDVI) at 8 km spatial resolution and paired ground-based information on vegetation, climate, soil and solar radiation, after validating the CASA model using NPP data from 33 stations along NECT. Important findings The 18-year averaged annual NPP along NECT was 426 g C·m^–2·a^–1, ranging from 58 to 811 g C·m^–2·a^–1 and decreased from east to west, which is consistent with the distribution of precipitation. Total annual NPP changed from 0.218 to 0.325 Pg C over the 18 years, with an average of 0.270 Pg C. Two distinct periods (1982–1990 and 1991–1999) of NPP variations were observed, separated by a sharp reduction during 1990–1991. From 1982 to 1990, a significant increase of 0.007 5 Pg C·a^–1 was observed; from 1991 to 1999, annual NPP showed no marked trend. From 1982 to 1999, annual NPP showed a significant increase, accounting for 56.65% of the whole transect, and the largest annual NPP increase during 1982–1999 appeared in cultivated land, typical steppe and meadow steppe, accounting for 62.6% of the increment of the whole region, while desert steppe and typical steppe showed higher sensitivity to climate change. Spatial distribution of NPP along NECT is determined by the pattern annual precipitation, and temporal variation of NPP is influenced by changes in annual precipitation and annual total solar radiation.