人类活动对西南山地植被覆盖变化的影响——以重庆市为例

Analysis of human activities as driving forces of vegetation cover changes in mountainous areas of Southwest China from 2000 to 2020:a case study in Chongqing

植被覆盖变化是生态环境变化的重要指标,定量解析其中的人类活动作用一直是生态领域研究的热点。以重庆市为例,基于遥感、气象以及统计数据,利用GIS技术和残差法,从归一化植被指数(NDVI)和土地利用/覆盖(LUCC)整合分析视角,探究西南山地2000—2020年植被覆盖变化的时空特征,深入解析人类活动影响。研究表明:(1)近20年间研究区植被覆盖呈整体上升趋势且空间异质性强,渝东南和渝东北地区植被覆盖以及恢复趋势明显优于渝中地区。(2)残差分析表明人类活动对植被覆盖变化同时存在正向和负向两个方面的影响,以正向影响为主导。(3)林地未变区和耕地未变区对植被覆盖变化的贡献程度最大(两者共达到84.18%),退耕还林贡献率仅为1.24%。(4)封禁育林面积与林地未变区植被覆盖变化存在极显著正相关关系(R^(2)=0.82),同时封禁育林生态工程能够较好地解释林地未变区残差变化。研究建立了LUCC对植被覆盖变化影响的贡献率清单,定量揭示封禁育林生态工程对植被覆盖恢复的重要作用,对丰富区域植被覆盖变化驱动研究具有一定参考价值。

The variation of vegetation coverage is an important indicator of environmental changes.Quantifying impact of human activities on vegetation coverage change has been a hot topic in the field of ecology.Although various vegetation coverage restoration projects have been conducted,relevant researches mainly focused on the project of returning farmland to forest.The role of afforestation project in vegetation restoration is limited at the qualitative acknowledge,without relevant quantitative research reported.In this paper,with Chongqing city as the study area,based on remote sensing,meteorological and statistical data,under the support of GIS technology and residual trend method,the spatiotemporal characteristics of vegetation cover change and the effect of human activities from 2000 to 2020 in mountainous areas of Southwest China were studied from the integrated perspective of normalized difference vegetation index(NDVI)and land-use and land-cover change(LUCC)analysis.The results are as follows:(1)In the recent 20 years,the vegetation coverage in the study area increased overall,and the spatial heterogeneity was strong.The status of vegetation coverage and its restoration tendency in northeast and southeast of Chongqing were superior to center area.(2)Residual analysis showed that human activities had both positive and negative effects on vegetation cover change,while the positive effects were dominant.Areas experiencing the positive impacts of human activity on vegetation coverage restoration were mainly concentrated in the southeast and northeast parts of the study area.In contrast,areas experiencing the negative impacts of human activity were mainly distributed in the center part of the study area.Areas surrounding the urban area of counties could also suffer the negative impacts of human activity.(3)The area of unchanged forestland and the unchanged cultivated land had the greatest influence on the change of vegetation cover(those two land use conversion typesa totaltotally account for 84.18%),and the contribution rate of returning farmland to forest was only 1.24%.(4)There was a significantly positive correlation between the area of afforestation project and the change of vegetation coverage in the area of unchanged forestland(R^(2)=0.82),and the ecological engineering of forest conservancy could explain the residual change of NDVI in the unchanged forest area.The contribution rate list of land-use and land-cover change to vegetation cover change was established in this study,which quantitatively revealed the important role of afforestation project on vegetation cover restoration.The results could provide important reference for the research of vegetation coverage change at regional scale.