2000—2020年中国荒漠化潜在发生范围区林草覆被时空变化特征

Spatial and temporal characteristics of forest and grass cover in the potential range of desertification in China from 2000 to 2020

干旱地区林草植被生长动态变化是研究荒漠化形成发展和演变过程的重要依据。本文基于改进方向性像元二分模型构建的2000—2020年中国荒漠化潜在发生范围区(PEDC)年植被覆盖度数据集,采用Sen+Mann-Kendall时间序列趋势变化检测方法,分析了2000—2020年PEDC,特别是林草覆盖区的植被生长状况时空变化特征。研究结果表明:①2000—2020年,PEDC平均植被覆盖度为0.284,改进的植被覆盖度估算结果能够较好地反映研究区植被覆盖状况,估算精度为86.98%。PEDC植被生长状况不断趋好,其中干旱区表现最为突出,显著增加区域达到了48%,而亚湿润干旱区平均增长量最大为0.1。②林草生态恢复工程措施效果显著,但植被恢复是个长期缓慢的过程,特别是林草面积的恢复。2000—2010年林草面积增加较少(0.002%);2010—2020年增加较多(0.371%)。③2000—2020年PEDC林地植被改善最明显,草地则较为稳定,植被覆盖度显著性增加区域分别为76.4%和71.8%。其中林地植被覆盖度在亚湿润干旱区增长量最大为0.15,而整个研究区草地增长了0.06。本文更深入地掌握PEDC林草覆盖区长时间序列植被生长状况,为进一步制定和实施各项生态工程提供重要信息参考。

The investigation of the dynamic changes of vegetation growth in arid areas is important to the study of the formation,development,and evolution of desertification.By using the Sen+Mann-Kendall method to detect the change of the time series trend,this paper analyzed the spatio-temporal variation characteristics of the vegetation cover in the potential extent of desertification in China(PEDC)from 2000 to 2020,especially in the forest and grasscovered area,based on the data set of annual vegetation coverage obtained by the improved directional dimidiate pixel model.The research results show that:(1)The average vegetation coverage of the PEDC is 0.284,the improved vegetation coverage estimation result well reflects the vegetation coverage,and the estimation accuracy is 86.98%.The vegetation growth situation is getting better,among which the arid area has the most prominent performance,with a significant increase of 48%,while the average increase in the sub-humid arid area is 0.1.(2)The ecological restoration projects of the forest and grass sector are effective,but vegetation restoration is a long and slow process.In terms of forest and grass area,the increase is small(0.002%)from 2000 to 2010 and relatively large(0.371%)from 2010 to 2020.(3)The forest quality of PEDC has improved most obviously among all vegetation types,while the grassland is relatively stable,and the areas of forestland and grassland which have seen significant increase account for 76.4%and 71.8%respectively from 2000 to 2020.Among them,the vegetation coverage of forestland increased by 0.15 in the sub-humid arid region,while that of grassland increased by only 0.06.This study can provide an in-depth understanding of the long-term vegetation growth status in the PEDC,especially in the forestgrass coverage area,and provide important information for the further formulation and implementation of various ecological projects.