中国植被覆盖度时空特征及其影响因素分析

植被覆盖度是衡量植被生长状况和描述生态系统环境的重要指标,以2001～2018年MODIS NDVI数据集为基础,采用混合像元二分模型,计算中国植被覆盖度(FVC),分析中国年FVC的时空变化特征,探讨FVC对气候和人类活动干扰的响应机制,以及人类活动对FVC影响的未来变化特征。结果表明:(1)中国FVC整体呈上升趋势;西北的年均FVC明显低于东南的年均FVC;除青藏高原FVC为下降趋势外,其余均呈上升趋势,且该趋势具有一定持续性。(2)各植被类型中,混交林的年均FVC最高,草原的年均FVC最低;而农作物变化率最大,混交林变化率最小,且未来将由改善转为退化趋势,其余均表现为持续性改善。(3)中国FVC与气温呈负相关、与降水呈正相关,且降水对FVC的影响强于气温,表明降水是影响FVC变化的主要因素。(4)中国人类活动对FVC的影响程度整体表现为增强趋势,未来人类活动影响力以反向持续性为主。表明未来18a中国FVC受人类活动的影响有所下降。

Spatiotemporal Characteristics of Fractional Vegetation Coverage and Its Influencing Factors in China

Abstract：Fractional vegetation coverage is an important index to measure vegetation growth and describe ecosystem environment. Based on the MODIS NDVI data set from 2001 to 2018, the fractional vegetation coverage in China was calculated using mixed pixel dichotomy model. Then, the spatial and temporal characteristics of annual fractional vegetation coverage in China are analyzed. To explore the response mechanism of fractional vegetation coverage to climate and human disturbance, and the future change characteristics of human disturbance to fractional vegetation coverage. The results show that: (1) fractional vegetation coverage in China is on the rise as a whole. The fractional vegetation coverage in Northwest China is significantly lower than that in Southeast China. Except the fractional vegetation coverage of the Qinghai-Tibet Plateau is declining, the others are on the rise, which has a certain sustainability. (2) Among all vegetation types, the average annual fractional vegetation coverage of mixed forest is the highest, while that of grassland is the lowest. The change rate of crop vegetation is the largest, while that of mixed forest is the smallest, and it will change from improvement to degradation in the future. The other types showed continuous improvement. (3) Fractional vegetation coverage is negatively correlated with temperature and positively correlated with precipitation in China. Moreover, precipitation has a stronger impact on fractional vegetation coverage than temperature. This indicates that precipitation is the main factor affecting the change of fractional vegetation coverage. (4) The impact of human activities on fractional vegetation coverage in China shows an increasing trend as a whole. In the future, the influence of human activities will be mainly reverse persistence. This indicates that the fractional vegetation coverage in China will be affected by human activities in the next 18 years.