土地利用变化对三峡库区重庆段植被净初级生产力的影响

研究土地利用变化对区域植被净初级生产力(Net Primary Productivity,NPP)的影响对于明确区域植被固碳能力与土地利用变化的关系,以及维持生态系统结构稳定具有重要意义。以三峡库区重庆段为例,基于2000—2015年MOD17A3数据和土地利用数据,分析研究区NPP时空分布特征并从景观生态学的角度探讨土地利用变化对区域植被NPP的影响。研究表明:(1)NPP年均值16年间波动不大,空间分布上从东到西逐渐减少;(2)研究期内林地面积增加,耕地和草地面积减小,而NPP总量从25.6 TgC增加到了28.5 TgC,其中耕地NPP约占总量的44%,林地次之(40%),草地最少(14%),2000—2005年、2005—2010年、2010—2015年土地利用变化对NPP变化的贡献率分别为26.49%、59.76%、17.27%;(3)区域生态景观指数中的香农多样性指数SHDI、斑块密度PD与NPP呈正相关,而聚合度AI与NPP呈负相关,景观格局类型和景观格局变化均影响区域植被NPP的增长。要提高区域植被NPP,需优化土地利用格局,增加景观异质性和斑块密度,重视培育幼龄林,并控制成熟林的数量。

Effects of land-use changes on vegetation net primary productivity in the Three Gorges Reservoir Area of Chongqing

It is significant to study the impact of land-use changes on vegetation net primary productivity (NPP) both for elucidating the relationship between the carbon assimilation ability of vegetation and the land-use changes on a regional scale, and for maintaining stability in ecosystem structures. By using the section of the Three Gorges Reservoir Area (TGRA) in Chongqing as a study area, we analyzed the spatio-temporal distribution of NPP and the impact of land-use changes on the regional NPP in term of landscape ecology based on the land-use maps and remote sensing data MOD17A3 from 2000 to 2015. The results revealed that the average annual NPP did not change much in over 16 years and it spatially decreased from east to west. During the study period, the areas of woodland increased, whereas the areas of farmland and grassland declined. The total NPP increased from 25.6 TgC to 28.5 TgC, in which comprised 44% in farmland, 40% in woodland, and 14% in grassland. The rates of NPP variations induced by land-use changes in 2000-2005, 2005-2010, and 2010-2015 were 26.49%, 59.76%, and 17.27% respectively. Shannon''s diversity index (SHDI) and patch density (PD) were positively correlated with NPP, whereas the aggregation index (AI) was negatively correlated with NPP. Both the types and their changes of landscape patterns increased NPP. To improve the regional vegetation NPP, some measures, which includes optimizing the land-use pattern, increasing the landscape heterogeneity and patch density, emphasizing the cultivation of young forest, and controlling the number of mature forests, need to be adopted by local governments in the future.