Manipulative experiments demonstrate how long-term soil moisture changes alter controls of plant water use
Manipulative experiments demonstrate how long-term soil moisture changes alter controls of plant water use
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DOI：
10.1016/j.envexpbot.2017.12.010
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发表时间：
2018-08-01
影响因子：
5.7
通讯作者：
McDowell, Nate G.
中科院分区：
文献类型：
--
作者：
Grossiord, Charlotte;Sevanto, Sanna;McDowell, Nate G.
树木蒸腾取决于未来可能发生变化的生物和非生物因素，包括降水和土壤湿度状况。虽然短期树液通量对土壤湿度和蒸发需求的响应一直是人们关注的主题，但在土壤湿度条件长期变化下，树液通量对这两个因素的相对敏感性很少得到实验确定。我们测试了土壤湿度的长期人工变化如何影响树木水平液通量对日大气蒸汽压差（VPD）和土壤湿度变化的敏感性，以及这些影响在不同森林类型和环境中的普遍性。暴露于相对长期（2 ~ 6年）的土壤湿度降低会降低树液通量对每日VPD和相对可提取水（REW）变化的敏感性，导致即使在高土壤湿度和最佳VPD下，树液通量也会降低。相反，长期灌溉的树木对日VPD和REW的敏感性显著增加，但仅在最缺水的地点。土壤湿度调控的相对变化与树液通量对VPD和REW变化的敏感性的相对变化之比在不同的站点上相似，这表明常绿树种对不同环境下长期土壤湿度状态的调节机制是共同的。总体而言，我们的研究结果表明，土壤水分有效性的长期变化，以及随后对这些新条件的调整，可能在未来控制森林用水方面发挥关键且越来越重要的作用。
Tree transpiration depends on biotic and abiotic factors that might change in the future, including precipitation and soil moisture status. Although short-term sap flux responses to soil moisture and evaporative demand have been the subject of attention before, the relative sensitivity of sap flux to these two factors under long-term changes in soil moisture conditions has rarely been determined experimentally. We tested how long-term artificial change in soil moisture affects the sensitivity of tree-level sap flux to daily atmospheric vapor pressure deficit (VPD) and soil moisture variations, and the generality of these effects across forest types and environments using four manipulative sites in mature forests. Exposure to relatively long-term (two to six years) soil moisture reduction decreases tree sap flux sensitivity to daily VPD and relative extractable water (REW) variations, leading to lower sap flux even under high soil moisture and optimal VPD. Inversely, trees subjected to long-term irrigation showed a significant increase in their sensitivity to daily VPD and REW, but only at the most water-limited site. The ratio between the relative change in soil moisture manipulation and the relative change in sap flux sensitivity to VPD and REW variations was similar across sites suggesting common adjustment mechanisms to long-term soil moisture status across environments for evergreen tree species. Overall, our results show that long-term changes in soil water availability, and subsequent adjustments to these novel conditions, could play a critical and increasingly important role in controlling forest water use in the future.