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Atmosphere‐Soil Interactions Govern Ecosystem Flux Sensitivity to Environmental Conditions in Semiarid Woody Ecosystems Over Varying Timescales
Journal of Geophysical Research: Biogeosciences ( IF 3.7 ) Pub Date : 2020-06-09 , DOI: 10.1029/2019jg005554
Kimberly E. Samuels‐Crow 1 , Kiona Ogle 1, 2, 3 , Marcy E. Litvak 4
Affiliation  

Water and CO2 flux responses (e.g., evapotranspiration [ET] and net ecosystem exchange [NEE]) to environmental conditions can provide insights into how climate change will affect the terrestrial water and carbon budgets, especially in sensitive semiarid ecosystems. Here, we evaluated sensitivity of daily ET and NEE to current and antecedent (past) environment conditions, including atmospheric (vapor pressure deficit [VPD] and air temperature [Tair]) and moisture (precipitation and soil water) drivers. We focused on two common southwestern U.S. (“Southwest”) biomes: pinyon‐juniper woodland (Pinus edulis , Juniperus monosperma ) and ponderosa pine forest (Pinus ponderosa ). Due to differences in aridity, rooting patterns, and plant physiological strategies (stomatal and hydraulic traits), we expected ET and NEE in these ecosystems to respond differently to atmospheric and moisture drivers, with longer response timescales in the drier pinyon‐juniper woodland. Net sensitivity to drivers varied temporally in both ecosystems, reflecting the integrated influence of interacting drivers and antecedent precipitation patterns. NEE sensitivity to VPD and soil moisture (and ET sensitivity to deep soil moisture [Sdeep]) was higher in the ponderosa forest. ET and NEE in both ecosystems responded almost instantaneously to Tair, VPD, and shallow soil moisture (Sshall), and increases in any of these drivers weakened the carbon sink and enhanced water loss. Conversely, Sdeep and precipitation influenced ET and NEE over longer timescales (days to months, respectively), and higher Sdeep enhanced the carbon sink. As climate changes, these results suggest hotter and drier conditions will weaken the carbon sink and exacerbate water loss from Southwest pinyon‐juniper and ponderosa ecosystems.

中文翻译:

在不同的时间尺度上,大气-土壤相互作用决定了生态系统通量对半干旱木质生态系统中环境条件的敏感性。

对环境条件的水和CO 2通量响应(例如,蒸散量[ET]和净生态系统交换[NEE])可以提供有关气候变化将如何影响陆地水和碳收支的见解,特别是在敏感的半干旱生态系统中。在这里,我们评估了日常ET和NEE对当前和以前(过去)环境条件的敏感性,包括大气(蒸气压亏缺[VPD]和空气温度[T air ])和水分(降水和土壤水)驱动因素。我们针对两种常见的美国西南部(“西南”)生物群落:pinyon-桧林地(松果刺柏monosperma)和美国黄松林(黄松)。由于干旱,生根模式和植物生理策略(口腔和水力性状)的差异,我们预计这些生态系统中的ET和NEE对大气和水分驱动因子的反应不同,而在较干燥的Pinyon-Juniper林地中响应时间更长。在两个生态系统中,对驱动器的净敏感性在时间上有所变化,反映了相互作用的驱动器和先前的降水模式的综合影响。在美国黄松林中,NEE对VPD和土壤水分的敏感性(和ET对深层土壤水分[S deep ]的敏感性)更高。ET和NEE在这两个生态系统的响应几乎瞬间至T空气,VPD,以及浅层土壤水分(S),而任何这些驱动因素的增加都会削弱碳汇并增加水的流失。相反,在更长的时间范围内(分别为数天至数月),S和降水会影响ET和NEE,而更高的S深会增强碳汇。随着气候的变化,这些结果表明更热和更干燥的条件将削弱碳汇,并加剧西南半松和黄松生态系统的水分流失。
更新日期:2020-08-10
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