青藏高原草地物候的空间尺度效应

Spatial scale effects of grassland phenology on the Qinghai-Tibet Plateau

准确的高山植被物候遥感产品是维持生态平衡、正确反映地表能量平衡及冰冻圈稳定的基础性数据。然而,目前常用于提取物候的遥感数据空间分辨率多样,基于不同空间尺度提取的物候可能存在尺度效应,但该问题目前并未受到广泛关注。本文利用10 m分辨率Sentinel-2、500及5600 m分辨率MODIS遥感数据,使用NDGI植被指数,基于GEE云平台提取了2022年青藏高原地区相应空间分辨率的物候产品,探讨了不同空间分辨率物候差异,定量分析了物候产品的空间尺度效应,并阐明了其随地形复杂度的变化。研究发现,相比于高空间分辨率遥感产品(10 m),较粗空间分辨率(500、5600 m)的春季物候存在明显的滞后现象。使用不同空间分辨率遥感产品探测草地物候时,尺度效应普遍存在,其中,秋季物候的尺度效应小于春季物候。另外,植被物候的尺度效应受地形影响,且随地形复杂度增大而增大。

Accurate high-altitude vegetation phenology remote sensing products are fundamental data for maintaining ecological balance,accurately reflecting surface energy balance,and stabilizing the cryosphere.However,currently used remote sensing data for phenology extraction have diverse spatial resolutions,and phenology extracted based on different spatial scales may exhibit scale effects,which have not received widespread attention.In this study,utilizing Sentinel-2 data with a spatial resolution of 10 m,MODIS data with spatial resolutions of 500 and 5600 m,and employing the NDGI vegetation index,phenology products with corresponding spatial resolutions for the Qinghai-Tibet Plateau in 2022 were extracted on the Google Earth Engine(GEE)cloud platform.The study explored the differences in phenology at different spatial resolutions,quantitatively analyzed the scale effects of phenology products,and elucidated their variations with terrain complexity.The research revealed that,compared to high spatial resolution remote sensing products(10 m),there is a noticeable lag phenomenon in the spring phenology of coarser spatial resolution(500 and 5600 m).When detecting grassland phenology using remote sensing products with different spatial resolutions,scale effects are generally present,with the scale effect of autumn phenology being smaller than that of spring phenology.Additionally,the scale effect of vegetation phenology is influenced by terrain and increases with the complexity of terrain.