中国集中连片特困区退耕还林还草生态效应评估

集中连片特困地区作为我国生态环境脆弱区是退耕还林还草的主战场,其退耕成效直接反映了退耕还林还草工程的整体实施效果,为新征程中巩固和拓展退耕还林还草成果提供经验镜鉴。以《中国农村扶贫开发纲要(2011-2020年)》文件明确的14个集中连片特困地区作为研究区域,基于2000-2020年生态系统年总初级生产力(AGPP)数据集和归一化植被指数(NDVI)数据集,对比分析集中连片特困区的退耕区和未退耕区AGPP和NDVI的年际变化差异,以此来评估集中连片特困地区实施退耕还林还草工程的生态效应。研究发现:(1)2000-2020年,集中连片特困区退耕还林还草面积为178554km²,占2000年耕地总面积的44.71%;(2)研究期内,退耕区与未退耕区AGPP和NDVI整体表现出增长趋势,其中退耕区AGPP和NDVI呈现极显著和显著上升趋势的面积分别占总面积的69.07%和86.51%,未退耕区的占比分别为65.88%和72.61%,且退耕区AGPP和NDVI的年均值和相对变化率均高于未退耕区;(3)2000-2020年整个区域、退耕区以及未退耕区AGPP和NDVI年际变化趋势大体一致,均表现出线性递增态势,且退耕区AGPP和NDVI的增长始终高于整个集中连片特困区和未退耕区。因此,研究通过探讨原集中连片特困区退耕还林还草对AGPP和NDVI的影响,为进一步调整和优化退耕还林还草政策提供了参考依据。

Evaluation of the ecological effect of returning farmland to forest and grassland in the former concentrated contiguous impoverished area of China

As a fragile ecological environment area in China, the former concentrated contiguous impoverished areas is the main battlefield for returning farmland to forests and grasslands. Its effect of returning farmland to forests and grasslands directly reflects the overall effect of the implementation of the project of returning farmland to forests and grasslands, whicht provides a mirror of the experience of consolidating and expanding the results of returning farmland to forests and grasslands in the new journey. Taking 14 concentrated contiguous impoverished areas specified in the document "China’s Rural Poverty Alleviation and Development Programme (2011-2020)" as the study area, based on the 2000-2020 ecosystem annual gross primary productivity (AGPP) dataset and the normalised vegetation index (NDVI) dataset, we compared and analysed the inter-annual changes in the AGPP and NDVI of fallowed and un-fallowed areas in the concentrated contiguous impoverished areas, in order to assess the ecological effect of implementing the project of returning farmland to forests and grasslands in the concentrated contiguous impoverished areas. The study found that: (1) from 2000 to 2020, the area of returning farmland to forests and grasslands in the concentrated contiguous impoverished area was 178554 km², accounting for 44.71% of the total area of arable land in 2000. (2) During the study period, AGPP and NDVI in the fallow and non-fallow areas showed an overall increasing trend, with 69.07% and 86.51% of the total area in the fallow area showing highly significant and significant increasing trends in AGPP and NDVI, respectively, while the proportion in the non-fallow area being 65.88% and 72.61%, respectively. The annual mean and relative rate of change of AGPP and NDVI were higher than those of the non-returned farmland area. (3) From 2000 to 2020, the inter-annual trends of AGPP and NDVI in the whole region, the fallow area and the non-fallowed area were generally consistent, showing a linear increasing trend. The growth of AGPP and NDVI in the fallow area was always higher than that in the whole of the concentrated contiguous impoverished area and the non-fallowed area. Therefore, this study provides a reference basis for further adjusting and optimizing the policy of returning farmland to forest and grassland by exploring the impacts of returning farmland to forest and grassland in the former concentrated contiguous impoverished area on AGPP and NDVI.