Abstract: Forest-typed nature reserves play an important role in supporting primary productivity, vegetation biomass, carbon storage, and biodiversity conservation, along with its crucial ecological functions. Understanding the ecological change in these regions could provide a fundamental and scientific basis for assessing the effectiveness of ecological protection initiatives. We comprehensively analyzed the spatiotemporal variations of fraction vegetation coverage (FVC), which was derived from MOD09 reflectance data in forest-typed reserves in China over the past 20 years. We employed trend analysis, nuclear density analysis, re-scaling range analysis to examine these changes. Correlation analysis was conducted to examine the relationship between these changes and climate patterns, using TerraClimate climate reanalysis data. The results showed that the average FVC in forest-typed nature reserves was 52.29% from 2000 to 2020, significantly higher than that of the non-farmland areas. There were significant differences in FVC among these reserves, with higher coverage in the south and lower coverage in the north. In general, 98.29% of these regions exhibited an increasing trend of FVC over the past 20 years. The sub-humid temperate and humid temperate ecological regions of Shanxi, northern Hebei, western Liaoning, and Shandong experienced faster increases in FVC, with an annual increasing rate of 0.61% and 0.58%·respectively, compared to average rate 0.26% per year of all reserves. The increase of FVC in these regions is expected to have strong sustainability in the future, while vegetation coverage in the southern China remained relatively stable. In terms of climatic factors, 44% of the reserves had exhibited varying degrees of warming trends over the past two decades. On average, air temperature increased by 0.013 ℃·a^-1, resulting in accelerated vegetation growth. Precipitation remained stable and had different effects on vegetation cover in different regions. In addition to the influence of rising temperature, a series of ecological projects have played a significant role in the restoration of vegetation in the sub-humid temperate regions with faster growth rate of vegetation coverage.

Key words: forest-typed natural reserve, fraction vegetation coverage, climatic factor