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首页> 外文期刊>Agricultural and Forest Meteorology >Increasing altitudinal gradient of spring vegetation phenology during the last decade on the Qinghai-Tibetan Plateau.
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Increasing altitudinal gradient of spring vegetation phenology during the last decade on the Qinghai-Tibetan Plateau.

机译：近十年来，青藏高原春季植被物候的海拔梯度逐渐增加。

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摘要

Spring vegetation phenology in temperate and cold regions is widely expected to advance with increasing temperature, and is often used to indicate regional climatic change. The Qinghai-Tibetan Plateau (QTP) has recently experienced intensive warming, but strongly contradictory evidence exists regarding changes in satellite retrievals of spring vegetation phenology. We investigated spatio-temporal variations in green-up date on the QTP from 2000 to 2011, as determined by five methods employing vegetation indices from each of the four sources: three Normalized Difference Vegetation Index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR), Systeme Pour l'Observation de la Terre (SPOT), MODerate resolution Imaging Spectroradiometer (MODIS), and the Enhanced Vegetation Index (EVI) from MODIS. Results indicate that, at the regional scale, all vegetation indices and processing methods consistently found no significant temporal trend (all P>0.05). This insignificance resulted from substantial spatial heterogeneity of trends in green-up date, with a notably delay in the southwest region, and widespread advancing trend in the other areas, despite a region-wide temperature increase. These changes doubled the altitudinal gradient of green-up date, from 0.63 days 100 m-1 in the early 2000s to 1.30 days 100 m-1 in the early 2010s. The delays in the southwest region and at high altitudes were likely caused by the decline in spring precipitation, rather than the increasing spring temperature, suggesting that spring precipitation may be an important regulator of spring phenological response to climatic warming over a considerable area of the QTP. Consequently, a delay in spring vegetation phenology in the QTP may not necessarily indicate spring cooling. Furthermore, the phenological changes retrieved from the widely used AVHRR NDVI differed from those retrieved from SPOT and MODIS NDVIs and MODIS EVI, necessitating the use of multiple datasets when monitoring vegetation dynamics from space.
机译：人们普遍预计，温带和寒冷地区的春季植被物候将随着温度的升高而发展，并且通常用于指示区域气候变化。青藏高原（QTP）最近经历了强烈的变暖，但是关于春季植被物候的卫星检索变化存在强烈矛盾的证据。我们调查了2000年至2011年QTP上绿化日期的时空变化，该变化是通过五种方法从四个来源中的每一个使用植被指数来确定的：高级超高分辨率辐射计（NDVI）的三个归一化植被指数（NDVI）（ AVHRR），地面观测系统（SPOT），中等分辨率成像光谱仪（MODIS）和MODIS的增强植被指数（EVI）。结果表明，在区域范围内，所有植被指数和加工方法均未发现明显的时间趋势（所有P> 0.05）。无关紧要的原因是，尽管整个区域温度升高，但绿化日期趋势在空间上存在很大的异质性，其中西南地区明显延迟，而其他地区则普遍存在前进趋势。这些变化使绿化日期的高度梯度增加了一倍，从2000年代初的0.63天100 m -1 到2010年代初的1.30天100 m -1 。西南地区和高海拔地区的延迟可能是由于春季降水减少而不是春季温度升高引起的，这表明春季降水可能是QTP在相当大的区域内对气候变暖的春季物候响应的重要调节因子。 。因此，QTP中春季植被物候的延迟可能未必表明春季冷却。此外，从广泛使用的AVHRR NDVI检索到的物候变化与从SPOT和MODIS NDVI和MODIS EVI检索到的物候变化不同，因此在监测来自太空的植被动态时必须使用多个数据集。

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