榆林地区植被时空分异特征及其影响因素研究

植被作为反映陆地生态系统和气候的重要指标，对研究全球或区域生态环境变化具有重要作用。以地处黄土高原生态脆弱区的榆林市为研究区，基于地理探测器模型，选取坡向、坡度、气温、降水和土壤类型5类自然因子，土地利用类型、人口密度和GDP 3类人文因子，分析榆林地区植被空间分异特征及其驱动力，并揭示了促进植被生长影响因子的最适宜特征。结果表明，（1）研究区2000—2018年植被覆盖趋向改善，NDVI呈现增加趋势，增速为0.11/10a,2008年以后植被增长较为明显；NDVI在2018年中高等级（0.6—0.8）面积比2000年中高等级面积明显增加；中高等级集中于榆林市东部黄土丘陵区，中低等级（0.2—0.4）集中于榆林市西北部的风沙区，植被覆盖呈现东部高西北低的空间分布特征。（2）人口密度和气温因子较好地解释植被NDVI空间分异性，是影响NDVI空间分异性的主要因子，GDP、土地利用类型和坡度是次级影响因子，其他因子对NDVI空间分异存在间接影响；坡向、降水和土壤类型因子与其他自然、人文因素对植被空间分布影响存在显著性差异。（3）自然、人文因子对榆林市NDVI的影响存在交互作用，因子之间的交互...

Spatio-temporal Variations and Influencing Factors of Vegetation in Yulin

As an essential indicator that reflects terrestrial ecosystem and climate, vegetation plays an important role in the study of global or regional ecological environment changes. Based on the Geographic Detector Model, five categories of natural factors(i.e.,aspect, slope, temperature, precipitation, and soil type) and three categories of human factors(i.e., land use type, population density,and GDP) were selected to analyze the spatial differentiation characteristics and driving forces of vegetation in the Yulin area. In addition, the study revealed top factors that promote vegetation growth in this area. The results show that the vegetation coverage in the study area had improved from 2000 to 2018. The Normalized Differential Vegetation Index(NDVI) suggested an increasing trend with a growth rate of 0.11/10 and a faster growing rate after 2008. Areas with a medium-high NDVI value(0.6-0.8) had increased significantly from 2000 to 2018. The medium-high NDVI was concentrated in the eastern loess hilly area of Yulin, while the mediumlow NDVI(0.2-0.4) in the wind-sand area in the northwest of Yulin. The vegetation cover exhibited spatial characteristics of high in the east and low in the northwest. Second, among the factors examined in the study, the population density and temperature were main factors affecting NDVI and could better explain its spatial variability, while GDP, land-use type, and slope were secondary influencing factors. Significant differences existed among the effects of slope direction, precipitation, soil type, and other natural or human factors on the spatial distribution of vegetation. Finally, the natural and human factors had an interactive effect on the NDVI in Yulin as these factors enhanced each other or had a non-linear relationship. Overall, the results of this study further revealed the type and range of influencing factors that promote vegetation growth. The combination of natural and human factors showed a more prominent impact on vegetation, providing scientific evidence for local governments to guide vegetation and ecological restoration.