亚热带山地丘陵区植被NPP时空变化及其与气候因子的关系————以湖南省为例

以湖南省为研究区,采用250 m×250 m空间分辨率的MODIS-NDVI数据,结合相应时间段的气象数据,使用改进的CASA模型,模拟并分析该区域2000-2013年间的植被NPP的时空变化特征,并借助统计分析方法对不同土地覆盖类型中植被NPP的变化趋势及其显著性,NPP与气候因子的相关性进行量化分析.结果表明:① 该区域的净初级生产量年际变化特征明显,年净初级生产量分布在41.62~125.40 Tg C/yr之间,平均值为86.34 Tg C/yr,总体来看,14年间湖南省植被净初级生产量呈波动减少趋势,年际减少趋势为2.70 Tg C/yr;② NPP空间分布差异较大,基本特点是西高东低,南高北低,从西南向东北呈逐渐递减趋势,其中,各植被分区的NPP有明显差异;③ 2000-2013年,湖南省植被NPP呈极显著增加(slope >0,p < 0.01),显著增加(slope > 0,0.01 ≤ p < 0.05),无明显变化(p ≥ 0.05),极显著减少(slope < 0,p < 0.01)和显著减少(slope < 0,0.01 ≤ p < 0.05)的区域分别占总面积的比例为5.40%,2.02%,61.64%,16.79%和14.15%.植被NPP变化趋势总体上显示为减少的趋势,而不同土地覆盖类型的植被NPP变化趋势及显著性存在较大差异,其中草地的NPP变化趋势最为显著,接着依次是森林,其他土地,建设用地和农田;④ 分析不同土地覆盖类型的植被NPP对气候因子的响应,发现NPP与降水量之间的相关关系强于其与温度的相关关系.

Spatial and temporal variability of the net primary production (NPP) and its relationship with climate factors in subtropical mountainous and hilly regions of China:A case study in Hunan province

In this study, we selected Hunan province as the study area. The vegetation NPP and its changes from 2000 to 2013 were calculated using improved Carnegie-Ames-Stanford Approach (CASA) model with MODIS-NDVI data at a 250 m×250 m spatial resolution and meteorological data. Furthermore, we quantitatively analyzed the correlation between NPP and climate for various land-cover types so as to provide reliable information for local environment and sustainable development. The results indicate that: (1) The annual amount of NPP decreased from 41.62 Tg C/yr in 2000 to 125.40 Tg/yr in 2013, with an average being about 86.34 Tg C/yr. In general, the total amount of NPP has decreased obviously since 2000, with an annual rate of about 2.70 Tg C/yr. (2) The annual NPP from 2000 to 2013 had significant spatial differences throughout the study area, decreasing from the southwest to the northeast. There were obvious differences over various vegetation divisions. (3) According to the changes rate of NPP from 2000 to 2013, the study area could be divided into five regions, namely, extremely remarkable increase rate (slope > 0, p < 0.01), remarkable increase rate (slope > 0, 0.01 ≤ p < 0.05), unnoticeable rate (p ≥ 0.05), extremely remarkable decrease rate (slope < 0, p < 0.01) and remarkable decrease rate (slope < 0, 0.01 ≤ p < 0.05), which accounted for 5.40%, 2.02%, 61.64%, 16.79% and 14.15%, respectively. In general, NPP decreased from 2000 to 2013 over different land-cover types, among which, the most significant change took place in grassland and forestland, followed by other types of land, construction land and farmland. (4) The spatial distribution of NPP had higher correlation with precipitation than with temperature.