Controls on gross production by a semiarid forest growing near its warm and dry ecotonal limit
Controls on gross production by a semiarid forest growing near its warm and dry ecotonal limit
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DOI：
10.1016/j.agrformet.2012.10.001
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发表时间：
2013-02-15
影响因子：
6.2
通讯作者：
Goulden, Michael L.
中科院分区：
文献类型：
--
作者：
Fellows, Aaron W.;Goulden, Michael L.
气候变化预计将使温度和水资源供应的空间格局向极地和向上倾斜，同时植被分布也会发生变化。生长在其南部或低海拔范围限制附近的植被可能特别容易受到死亡和流离失所的影响。我们调查了位于南加州圣哈辛托山脉森林下限上方的橡树和松树林对初级生产总值 (GPP) 的控制。当地气候为地中海山地气候，该林在 20 世纪 90 年代初以及 2002 年至 2004 年期间经历了大规模的死亡，同时还发生了长期干旱。冬季保持高二氧化碳吸收率，夏季获取土壤深处的水，为全年的生长季节提供了条件。尽管经常出现寒冷的夜晚，该地点的常绿植物全年仍保持光合作用活跃。在气温低于 8 摄氏度时观察到二氧化碳吸收率很高，这比其他生态系统报道的温度要低。冬季寒冷对GPP影响较小，冬季变暖对GPP影响较小。植被从土壤、腐泥土和裂隙花岗岩基岩中吸取水分，以支持干燥夏季的蒸腾作用和二氧化碳吸收，从而进一步延长了生长季节。获得土壤和风化层深处可靠的水分供应对于该地区大树的生存至关重要。如果蒸发率增加或年际降水量变化导致深层风化层水分更频繁或更严重地消耗，这些树木可能容易受到气候变化的影响。(C) 2012 Elsevier B.V. 保留所有权利。
Climate change is expected to move the spatial patterns of temperature and water availability poleward and upslope, with concomitant shifts in vegetation distribution. Vegetation growing near its southern or low-elevation range limit may prove especially susceptible to mortality and displacement. We investigated the controls on Gross Primary Production (GPP) by an oak and pine stand located just above the lower forest limit in Southern California's San Jacinto Mountains. The local climate was montane Mediterranean, and the stand experienced extensive mortality in the early 1990s and from 2002 to 2004 coincident with extended droughts. The maintenance of high rates of CO2 uptake in winter, and access to water deep in the soil column in summer, allowed for a year-round growing season. The evergreens at the site remained photosynthetically active year-round despite frequent freezing nights. High rates of CO2 uptake were observed at air temperatures below 8 degrees C, which is colder than has been reported for other ecosystems. Winter cold exerted a minor limitation on GPP, and winter warming would have a small effect on GPP. Vegetation withdrew water from the soil, saprolite, and fractured granitic bedrock to support transpiration and CO2 uptake during the dry summer, which further expanded the growing season. Access to a reliable supply of moisture deep in the soil and regolith appears critical for the survival of large trees at the site. These trees may prove vulnerable to climate change if increasing evaporation rates or interannual precipitation variability causes a more frequent or severe depletion of deep regolith moisture.(C) 2012 Elsevier B.V. All rights reserved.