College of Geographical Science, Inner Mongolia Normal University, Hohhot 010022, China; Inner Mongolia Key Laboratory of Remote Sensing and Geographic Information Systems, Inner Mongolia Normal University, Hohhot 010022, China; Department of Natural Resources, Wulanchabu 012000, China.
College of Geographical Science, Inner Mongolia Normal University, Hohhot 010022, China.
Sci Total Environ. 2023 Feb 10;859(Pt 2):160373. doi: 10.1016/j.scitotenv.2022.160373. Epub 2022 Nov 19.
We investigate the spatiotemporal patterns and environmental controls of the end of the vegetation growing season (EOS) in autumn across the alpine and temperate grasslands of China from 2001 through 2020, focusing on whether the EOS is likely a "dryness effect" due to drought or a "coolness effect" caused by cold temperature in autumn. The results show that the EOS date is earlier (∼6 days earlier on average) in alpine grasslands than in temperate grasslands. During 2001-2020, a slight non-significant delay of 1.0 day/decade is observed for the regional averaged EOS, which is mostly induced by the delayed EOS in 64.4 % of the study region. Preseason temperature (1-2 months before the EOS) exerts a positive control on the EOS in most of the alpine grasslands and some regions of the eastern part of the temperate grasslands, while drought with a mean length of 3.2 months before the EOS exerts positive effects on the EOS in the central, southwestern, and western parts of the temperate grasslands and in the northeastern part of the alpine grasslands. The positive effects of temperature and drought are very likely phenomena reflecting that the EOS is the "coolness effect" associated with lower temperatures in autumn and the "dryness effect" due to drought, especially meteorological drought without consideration of soil moisture, in late summer and/or early autumn, respectively. Our findings are supported by an analysis of the spatial patterns of the cold degree days (CDD) and EOS sensitivity to the CDD. However, the negative effects of drought are also found in eastern temperate grasslands, likely caused by decreased temperature accompanied by increased moisture. The results presented here highlight the importance of incorporating the impacts of droughts on EOS variability, as well as their interactive effects with temperature, into current vegetation autumn phenology models for grasslands.
我们研究了 2001 年至 2020 年期间中国高山和温带草原秋季植被生长季结束（EOS）的时空模式和环境控制因素，重点关注 EOS 是否可能是由于干旱引起的“干燥效应”或秋季低温引起的“寒冷效应”。结果表明，高山草原的 EOS 日期比温带草原更早（平均早约 6 天）。在 2001-2020 年期间，区域平均 EOS 观察到轻微的非显著延迟，为 1.0 天/十年，这主要是由于研究区域 64.4%的 EOS 延迟所致。 preseason 温度（EOS 前 1-2 个月）对大多数高山草原和部分温带草原东部地区的 EOS 具有正控制作用，而 EOS 前 3.2 个月的干旱对温带草原中部、西南部和西部地区以及高山草原东北部的 EOS 具有正影响。温度和干旱的积极影响很可能是反映 EOS 是与秋季低温相关的“寒冷效应”和由于干旱（尤其是不考虑土壤水分的气象干旱）引起的“干燥效应”的现象，特别是在夏末和/或初秋。我们的研究结果得到了冷度日（CDD）的空间格局分析和 EOS 对 CDD 敏感性的支持。然而，在东部温带草原也发现了干旱的负面影响，这可能是由于温度降低伴随湿度增加所致。这里提出的结果强调了将干旱对 EOS 变化的影响以及它们与温度的相互作用纳入当前草原植被秋季物候模型的重要性。
