《ECOLOGY》| 卫星遥感归一化植被指数低估了过去30年青藏高原高寒草地植被生长的变化
Sep.27.2021
摘要
卫星遥感归一化植被指数(NDVI)是研究植被物候动态的重要手段，越来越多地应用于揭示植被生长对气候变化的响应。然而，由于缺乏长期野外观测的证据，卫星遥感NDVI数据在“捕捉”植被物候长期变化方面的效率仍待进一步探讨。同时，气候变化常常导致植被组成的变化，这种改变是否会影响卫星遥感NDVI数据对植被物候监测的效率尚不清楚。基于此，我们通过对1982-2014年高寒草地植物生物量季节动态的长期监测，评估了基于NDVI数据的遥感物候变化与基于生物量动态的地面观测物候变化之间的匹配性。通过研究发现，全球生态模拟与制图研究组(GIMMS)的NDVI数据能够“捕捉”到过去33年中地面观测的生长物候的整体提前，但未探测到2000-2014年期间的变化;而中分辨率成像光谱仪(MODIS)的NDVI数据则与地面观测较为一致，在2000年后也显示出物候的提前趋势。然而，这两类卫星遥感NDVI数据所指示的生长物候提前幅度均小于地面观测。进一步分析发现，草地物种组成的长期变化(禾草丰度增加、杂类草丰度降低)能够减弱遥感物候的提前幅度，但不影响地面观测物候的提前幅度。这些发现表明，卫星遥感NDVI数据所指示的生长物候对气候变化的响应异于地面观测，部分原因是由于植物群落组成长期变化的影响。
Sep.27.2021
Abstract
Satellite-derived normalized difference vegetation index (NDVI) data are increasingly relied on to reveal the growth responses of vegetation to climate change, yet the vegetation growth tracking accuracy of these data remains unclear due to a lack of long-term field data. Here, we adopted a unique field-measured seasonal aboveground biomass dataset from 1982–2014 to assess the potential of using satellite-derived NDVI data to match field data in regard to the interannual variability in seasonal vegetation growth in a Tibetan alpine grassland. We revealed that Global Inventory Monitoring and Modeling System (GIMMS) NDVI data captured the advancement of field-measured vegetation growth throughout the entire study period but not from 2000–2014, while MODIS NDVI data still observed this advancing trend after 2000 to a limited extent. However, satellite-derived NDVI data consistently underestimated the advancement degree of field-measured vegetation growth, regardless of whether GIMMS or MODIS NDVI data were considered. We tentatively attribute this underestimation to an increased ratio of grass biomass to forb biomass, which could delay the advancement of NDVI development but not affect that of field-measured biomass development. Our results suggest that satellite-derived NDVI data may miss critical responses of vegetation growth to global climate change, potentially due to long-term shifts in plant community composition.
ECOLOGY《生态学》出版报告生态学研究基本要素的文章。重点是记录重要的生态学现象。该杂志发表了一系列广泛的研究，包括迅速扩大的主题、技术、方法和概念的范围：从古生态学到当今的现象；进化、种群、生理、社区和生态系统生态学，以及生物地球化学；包括描述性、比较性、实验性、数学、统计和跨学科方法。
原文链接link！
https://doi.org/10.1002/ecy.3518
点击“阅读原文”可阅览文章
— END —