Excess radiation exacerbates drought stress impacts on canopy conductance along aridity gradients
Excess radiation exacerbates drought stress impacts on canopy conductance along aridity gradients
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DOI：
10.5194/bg-19-4197-2022
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发表时间：
2022-09
期刊：
影响因子：
4.9
通讯作者：
Jing Wang;X. Wen
中科院分区：
文献类型：
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作者：
Jing Wang;X. Wen
抽象的。所有共存物种的气孔导度(GS)调节干旱和半干旱草原的蒸腾作用。然而，干旱胁迫对冠层导度(Gs)的影响还存在争议，非生物和生物约束对Gs的交互影响仍然知之甚少。在这里，我们使用叶片有机质源水(Δ18O)上方的~(18)O富集作为Gs的替代，以增加对这些影响的理解。沿干旱梯度在黄土高原(LP)、内蒙古高原(MP)和青藏高原(TP)建立了3个草地样带，它们的太阳辐射和温度条件不同。结果表明，随着样带内干旱程度的增加，气孔导度一直呈下降趋势。在干旱程度一定的情况下，由于低温和高辐射，TP上的GS低于其他两个高原上的GS。干旱胁迫对气孔导度的主要决定因素是LP和MP上的土壤水分(SM)，而TP上的水汽压差(VPD)。在样带内，太阳辐射通过干旱胁迫对Gs表现出持续的负效应，而温度对TP的Gs有负效应，而对LP和MP没有影响。叶面积和非生物因子的交互作用使气孔导度的解释变异性在LP和MP上分别增加了17%和36%，但在TP上并非如此，因为气候对气孔导度有压倒性的影响。这些结果强调了综合多种胁迫因素和植物特性来确定Gs的空间变异性的必要性。
Abstract. Stomatal conductance (gs) of all coexisting species regulates transpiration in arid and semiarid grasslands prone to droughts. However, the effect of drought stress on canopy conductance (Gs) is debated, and the interactive effects of abiotic and biotic constraints on Gs remain poorly understood. Here, we used 18O enrichment above the source water (Δ18O) of leaf organic matter as a proxy for Gs in order to increase the understanding of these effects. Three grassland transects were established along aridity gradients on the Loess Plateau (LP), the Inner Mongolian Plateau (MP), and the Tibetan Plateau (TP), which differ with respect to solar radiation and temperature conditions. Results showed that Gs consistently decreased with increasing aridity within transects. Gs on the TP was lower than that on the other two plateaus for a given level of aridity due to low temperature and high radiation. The primary determinant of drought stress on Gs was soil moisture (SM) on the LP and MP, whereas it was the vapor pressure deficit (VPD) on the TP. Solar radiation exhibited a consistently negative effect on Gs via drought stress within transects, while temperature had negative effects on Gs on the TP but no effect on the LP or MP. Adding the interaction of leaf area and abiotic factors increases the percentage of explained variability in Gs by 17 % and 36 % on the LP and MP, respectively, although this is not the case on the TP, where the climate exerts an overwhelming effect. These results highlight the need to integrate multiple stressors and plant properties to determine spatial variability in Gs.