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Daytime temperature contributes more than nighttime temperature to the weakened relationship between climate warming and vegetation growth in the extratropical Northern Hemisphere
Ecological Indicators ( IF 6.9 ) Pub Date : 2021-09-16 , DOI: 10.1016/j.ecolind.2021.108203
Zhoutao Zheng 1 , Yangjian Zhang 1, 2, 3 , Juntao Zhu 1 , Nan Cong 1
Affiliation  

Global warming has boosted vegetation growth to a large extent, but this stimulation effect has significantly weakened in recent years. Among the set of possible driving forces, the asymmetric daytime and nighttime warming effect has been largely neglected. To improve our understanding on the relationship between vegetation growth and global warming, this study tries to attribute the respective effects of daytime and nighttime temperature on vegetation growth and reveal their temporal trends in the extratropical Northern Hemisphere (30–90 °N). The results showed there had been significant warming trends in growing season maximum (TMX, 0.37 °C per decade) and minimum temperatures (TMN, 0.38 °C per decade) during 1982–2015, especially in high latitudes of the NH. Under the asymmetric diurnal warming, the effects of TMX and TMN on normalized difference vegetation index (NDVI) exhibited distinct temporal variations between mid- (<55 °N) and high latitudes (>55 °N). The positive correlation between NDVI and TMX (RNDVI-TMX) weakened in high latitudes, as well as the negative correlation between NDVI and TMN (RNDVI-TMN). However, the RNDVI-TMX and RNDVI-TMN changed little in mid-latitudes. Moreover, the weakening effect of TMX on NDVI was more apparent than that of TMN in high latitudes. The area with significantly (p < 0.1) positive RNDVI-TMX and significantly (p < 0.1) negative RNDVI-TMN both shrank from 1982–1998 to 1999–2015, with prior (15.97%) twice the latter one (7.09%) in shrunk area in high latitudes. With regard to vegetation type, decline in area with significantly (p < 0.1) positive RNDVI-TMX and negative RNDVI-TMN was extremely obvious in savannas, deciduous broadleaf forests and deciduous needleleaf forests. Besides, we also disclosed the poor performance of ecosystem process models in capturing the dynamic relationship between vegetation growth and diurnal temperature, which might be caused by their totally relying on diurnal mean temperature, instead of daytime and nighttime temperature, in forcing the models. This study can further advance our understandings on ecosystem responses to climate warming, and efficiently improve performance of ecosystem models.



中文翻译:

北半球温带气候变暖与植被生长之间的关系减弱,白天温度的贡献大于夜间温度

全球变暖在很大程度上促进了植被生长,但近年来这种刺激作用明显减弱。在一系列可能的驱动力中,不对称的白天和夜间变暖效应在很大程度上被忽略了。为了加深我们对植被生长与全球变暖之间关系的理解,本研究试图将白天和夜间温度对植被生长的各自影响归因于其在温带北半球(30-90°N)的时间趋势。结果表明,在 1982-2015 年期间,生长季最大值(TMX,每十年 0.37 °C)和最低温度(TMN,每十年 0.38 °C)有显着的变暖趋势,特别是在北半球高纬度地区。在不对称的昼夜变暖下,TMX 和 TMN 对归一化差异植被指数 (NDVI) 的影响在中纬度(<55 °N)和高纬度(> 55 °N)之间表现出明显的时间变化。NDVI 与 TMX (RNDVI-TMX ) 在高纬度地区减弱,以及 NDVI 与 TMN (R NDVI-TMN )之间的负相关。然而,R NDVI-TMX和 R NDVI-TMN在中纬度地区变化不大。此外,在高纬度地区,TMX对NDVI的减弱作用比TMN更为明显。从1982-1998年到1999-2015年,显着( p  < 0.1)正R NDVI-TMX和显着( p  < 0.1)负R NDVI-TMN的区域都缩小了,之前(15.97%)是后者(7.09%)的两倍) 在高纬度地区的收缩区。关于植被类型,面积下降显着(p  < 0.1)正 R NDVI-TMX而负R NDVI-TMN在稀树草原、落叶阔叶林和落叶针叶林中极为明显。此外,我们还揭示了生态系统过程模型在捕捉植被生长与昼夜温度之间的动态关系方面表现不佳,这可能是由于它们完全依赖日平均温度而不是白天和夜间温度来强制模型。这项研究可以进一步加深我们对生态系统对气候变暖反应的理解,并有效提高生态系统模型的性能。

更新日期:2021-09-16
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