基于地形梯度的湘西地区生态系统服务价值时空变化

为探究土地利用和生态系统服务价值（ecosystem service value，ESV）随不同地形因子变化的情况，本文利用湘西地区1990年、1995年、2000年、2005年、2010年及2015年6期遥感数据、野外调研数据和统计数据，分析了湘西不同土地利用类型在不同地形梯度上的变化、生态系统服务价值的时空变化及土地利用格局与ESV的相关性。研究结果表明：1）受人类活动影响较大的土地利用类型如耕地和建设用地主要分布在较低高度及坡度梯度上，山体南面和东面方向各类型土地面积较大。林地在不同地形梯度上均为最主要的土地利用类型。建设用地面积在不同地形梯度上随时间均明显呈增加趋势。2） ESV在海拔梯度上表现为先减少后增加，且海拔越高，ESV随时间变化的增长幅度越小；ESV随坡度增大而增大，且25年间最小坡度梯度上增长量最多；ESV随着地形位指数上升而增大；坡向变化中，东南方向出现ESV最低值，西北方向出现ESV最高值，东和西北方向ESV随时间增长量最大。3）相关性分析表明，林地、草地在坡度和地形位梯度上的变化与ESV变化呈正相关。湘西地区土地利用变化及生态系统服务价值随地形变化的差异明显。本研究为合理布局和保护我国南方丘陵山地区域的生态用地，发挥湘西地区的生态屏障作用提供了理论依据和决策支持。

Spatial-temporal changes of ecosystem service values in Xiangxi region based on terrain

To understand the change of land use and ecosystem service value (ESV) on different terrain gradients, this study used remote sensing data, field data and statistic data of Xiangxi region in 1990, 1995, 2000, 2005, 2010 and 2015 to analyze the change of each land use types along the gradients of elevation, slope, aspect and terrain index, which were classified into five levels by quantile method, respectively. The study also evaluated the ESV with XIE Gaodi''s method to explore the spatio-temporal change of ESV in Xiangxi region. And R Studio and Pearson correlations were used to analyze correlation between areas changes of different land use types and change of ESV with terrain gradients. The results showed that:1) areas of different land use types were significantly different on different terrain gradients. The human-activity-affected cropland and construction land mainly distributed on low gradients of elevation, slope and terrain index, while the natural systems, such as forestland and grassland, were mainly on high gradients of the three terrain factors. The south and east slopes were with larger areas of each land use type. Forestland occupied about 70% area on every terrain gradient, and the construction land area significantly increased on every terrain gradient over 25 years. 2) ESV decreased first and then increased with increasing elevation. From 1990 to 2015, ESV increased at lower elevation gradient, however, change was slighter at higher elevation, and it even decreased on the highest elevation gradient. ESV increased with slope growth. Over 25 years, ESV increased most on the lowest slope gradient. In a similar way, ESV evenly increased with increasing terrain index gradient. ESV was the lowest in southeast slope, highest in northwest slope, and increased most in east and northwest slopes from 1990 to 2015. 3) Correlations between change of land use types areas and ESV with gradients of elevation, slope, aspect, terrain index were different. On elevation gradient, grassland area change significantly positively correlated with ESV change. On slope gradient, forestland and grassland areas changes both had extremely positive correlation with ESV change. On aspect gradient, cropland and unused land areas changes had extremely negative correlation with ESV change, while forestland had a significant positive correlation. On terrain index gradient, areas changes of forestland and grassland were significantly correlated with change of ESV. In summary, the changes of land use and ESV were obviously different regarding topography. Forestland and grassland were two important land use types for improvement of ESV in mountain area of Xiangxi region.