北京“百万亩造林”对浅山区生物多样性的影响评价

目的]人工造林对生物多样性恢复和城市森林功能发挥的影响深远,科学评估人工造林对生态系统恢复速度及稳定性的影响是实现生物多样性保护的基础。方法]采用格网法获取北京浅山区276个样本单元,根据2010年、2015年和2018年土地利用类型数据,选择多样性、丰富度、均匀度和优势度4个测算指标,分别测算各期生物多样性指数及时空格局,运用OLS回归和分位点回归评价"百万亩"造林对浅山区生物多样性的影响方向和程度。结果](1)2018年北京市浅山区林地覆盖率达到51.66%,林地面积较2015年增加了3 400hm~2,且林地二级类型间变化较大;(2)2018年北京市浅山区多样性指数、丰富度指数、均匀度指数和优势度指数均值分别为0.432、0.544、0.504和0.276,多样性和均匀度有小幅度降低,但丰富度和优势度提升明显。(3)不同分位水平下,人工造林对浅山区生物多样性的影响方向和程度并不一致,在10%分位水平下,样本单元内林地面积的快速增加均对各项生物多样性指数有显著的促进作用,但影响程度不同。结论]人工造林应综合考虑源地物种分布状况、造林类型和优势林种等多方面因素,才能最大程度发挥其对生物多样性的修复和保护作用。

BIODIVERSITY IMPACT ASSESSMENT OF "ONE MILLION MU AFFORESTATION" IN THE SHALLOW MOUNTAIN AREA OF BEIJING

Artificial afforestation has a profound impact on the restoration of biodiversity and the function of urban forest. The scientific evaluation of the impact of artificial afforestation on the rate and stability of ecosystem restoration is the basis of biodiversity conservation. Grid method is used to obtain 276 samples unit shallow mountainous area of Beijing, according to a 2010, 2015 and 2018 data of land use types, choose diversity, richness, evenness and dominance of four measurement indicators, measuring periods respectively biodiversity index and space time structure, use of OLS regression and quantile regression evaluation "one million mu of afforestation" in shallow mountain direction and degree of the influence of biological diversity. As a result, there are three conclusions as follows. Firstly, in 2018, the forest coverage rate in shallow mountainous areas of Beijing reached 51.66%, and the forest area increased by 3 400hm2 compared with that in 2015. Secondly, in 2018, the mean values of diversity index, richness index, evenness index and dominance index in shallow mountainous areas of Beijing were 0.432, 0.544, 0.504 and 0.276, respectively. The diversity and evenness decreased slightly, but the richness and dominance increased significantly. Thirdly, at different subdivision levels, the direction and extent of the influence of artificial afforestation on biodiversity in shallow mountainous areas are not consistent. At the 10% subdivision level, the rapid increase of forest area in the sample unit has a significant promoting effect on various biodiversity indexes, but the degree of influence is different. Artificial afforestation should take into account the distribution of species in the source region, the type of afforestation and the dominant forest species, so as to give full play to its role in the restoration and protection of biological diversity.