Soil moisture dominates the interannual variability in alpine ecosystem productivity by regulating maximum photosynthetic capacity across the Qinghai-Tibetan Plateau

Zhang, Tao; Tang, Yuanyuan; Xu, Mingjie; Zhao, Guang; Cong, Nan; Zheng, Zhoutao; Zhu, Juntao; Niu, Ben; Chen, Zhi; Zhang, Yang‐Jian; Chen, Ning; He, Yongtao; Yu, Guirui

doi:10.1016/j.gloplacha.2023.104191

Cited by 7 publications

(2 citation statements)

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“…In general, SIF trended upward with rising SM levels in July. This observation underscores the dominant role of SM in driving vegetation growth within the region, a finding that aligns with prior research [8,55]. Strong land-atmosphere interactions fortified the negative VPD-SM coupling in the TRHR during July, thus increasing the probability of compound droughts.…”

Section: Discussionsupporting

confidence: 87%

“…In mountain grassland regions, increased temperatures favor an earlier vegetation growth period and an increase in vegetation photosynthesis [54]. An increase in SM can enhance the maximum photosynthetic capacity of mountain ecosystems, thereby promoting vegetation growth [55]. Overall, the SIF showed a decreasing trend with an increasing VPD in the TRHR (Supplementary Materials, Figure S8).…”

Section: Discussionmentioning

confidence: 94%

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Substantial Reduction in Vegetation Photosynthesis Capacity during Compound Droughts in the Three-River Headwaters Region, China

Miao,

An,

Zhang

et al. 2023

Remote Sensing

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Solar-induced chlorophyll fluorescence (SIF) is a reliable proxy for vegetative photosynthesis and is commonly used to characterize responses to drought. However, there is limited research regarding the use of multiple high-resolution SIF datasets to analyze reactions to atmospheric drought and soil drought, especially within mountain grassland ecosystems. In this study, we used three types of high-spatial-resolution SIF datasets (0.05°), coupled with meteorological and soil moisture datasets, to investigate the characteristics of atmospheric, soil, and compound drought types. We centered this investigation on the years spanning 2001–2020 in the Three-River Headwaters Region (TRHR). Our findings indicate that the TRHR experienced a combination of atmospheric drying and soil wetting due to increases in the standardized saturation vapor pressure deficit index (SVPDI) and standardized soil moisture index (SSMI). In the growing season, atmospheric drought was mainly distributed in the southern and eastern parts of the TRHR (reaching 1.7 months/year), while soil drought mainly occurred in the eastern parts of the TRHR (reaching 2 months/year). Compound drought tended to occur in the southern and eastern parts of the TRHR and trended upward during 2001–2020. All three SIF datasets consistently revealed robust photosynthetic activity in the southern and eastern parts of the TRHR, with SIF values generally exceeding 0.2 mW· m−2·nm−1·sr−1. Overall, the rise in SIF between 2001 and 2020 corresponds to enhanced greening of TRHR vegetation. Vegetation photosynthesis was found to be limited in July, attributable to a high vapor pressure deficit and low soil moisture. In the response of CSIF data to a drought event, compound drought (SVPDI ≥ 1 and SSMI ≤ −1) caused a decline of up to 14.52% in SIF across the source region of the Yellow River (eastern TRHR), while individual atmospheric drought and soil drought events caused decreases of only 5.06% and 8.88%, respectively. The additional effect of SIF produced by compound drought outweighed that of atmospheric drought as opposed to soil drought, suggesting that soil moisture predominantly governs vegetation growth in the TRHR. The reduction in vegetation photosynthesis capacity commonly occurring in July, characterized by a simultaneously high vapor pressure deficit and low soil moisture, was more pronounced in Yellow River’s source region as well. Compound drought conditions more significantly reduce SIF compared to singular drought events. Soil drought evidently played a greater role in vegetation growth stress than atmospheric drought in the TRHR via the additional effects of compound drought.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 94%