Recent trends in Inner Asian forest dynamics to temperature and precipitation indicate high sensitivity to climate change
Recent trends in Inner Asian forest dynamics to temperature and precipitation indicate high sensitivity to climate change
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DOI：
10.1016/j.agrformet.2012.12.006
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发表时间：
2012-12
影响因子：
6.2
通讯作者：
B. Poulter;N. Pederson;Hongyan Liu;Zaichun Zhu;R. D’Arrigo;P. Ciais;N. Davi;D. Frank;C. Leland
中科院分区：
文献类型：
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作者：
B. Poulter;N. Pederson;Hongyan Liu;Zaichun Zhu;R. D’Arrigo;P. Ciais;N. Davi;D. Frank;C. Leland
半干旱生态系统在调节全球气候方面发挥着重要作用，这些生态系统在人类世的命运取决于温度，降水和CO2之间的相互作用。然而，在寒冷干旱的环境中，降水并不是森林生产力的唯一限制因素。降水和气温变化之间的相互作用可能会增强土壤水分胁迫，同时延长生长季节的长度，对净碳吸收的后果尚不清楚。本研究利用卫星遥感、树木年代学和动态全球植被模型（DGVM）模拟来量化森林动态对十年气候变化和趋势的敏感性，评估了亚洲内陆森林（蒙古和北方中国）生产力和物候的近期趋势。在1982年和2010年之间的光合有效辐射分数（FPAR）的趋势表明，约7%的地区在春季（3月，4月，5月）绿化，和3%的面积“布朗宁”在夏季（6月，7月，8月）。这些FPAR的卫星观测得到了LPJ DGVM模拟的NPP趋势的证实。春季绿化趋势FPAR主要是由降水的长期趋势，而夏季布朗宁趋势与降水减少。来自25个站点的树木年轮数据证实，年生长增量主要受蒙古夏季降水（6月、7月、8月）和中国北方春季降水（3月、4月、5月）的限制，前一年滞后效应相对较弱。IPCC CMIP 3模型的气候预测集合表明，气温变暖（春季，夏季）预计将与夏季降水量增加有关，这与CO2相结合，导致NPP大幅增加，甚至可能增加蒙古草原的森林覆盖率。在缺乏对植物生长的强烈的直接CO2施肥效应的情况下（例如，由于养分限制）、水分紧张或较高的自养呼吸作用减少碳的增加导致生产力下降和森林覆盖损失。因此，这些半干旱生态系统的命运似乎取决于CO2施肥效应的大小和微妙之处，需要在干旱系统中进行实验观测，以测试和完善植被模型。
Semi-arid ecosystems play an important role in regulating global climate with the fate of these ecosystems in the Anthropocene depending upon interactions among temperature, precipitation, and CO2. However, in cool-arid environments, precipitation is not the only limitation to forest productivity. Interactions between changes in precipitation and air temperature may enhance soil moisture stress while simultaneously extending growing season length, with unclear consequences for net carbon uptake. This study evaluates recent trends in productivity and phenology of Inner Asian forests (in Mongolia and Northern China) using satellite remote sensing, dendrochronology, and dynamic global vegetation model (DGVM) simulations to quantify the sensitivity of forest dynamics to decadal climate variability and trends. Trends in photosynthetically active radiation fraction (FPAR) between 1982 and 2010 show a greening of about 7% of the region in spring (March, April, May), and 3% of the area ‘browning’ during summertime (June, July, August). These satellite observations of FPAR are corroborated by trends in NPP simulated by the LPJ DGVM. Spring greening trends in FPAR are mainly explained by long-term trends in precipitation whereas summer browning trends are correlated with decreasing precipitation. Tree ring data from 25 sites confirm annual growth increments are mainly limited by summer precipitation (June, July, August) in Mongolia, and spring precipitation in northern China (March, April, May), with relatively weak prior-year lag effects. An ensemble of climate projections from the IPCC CMIP3 models indicates that warming temperatures (spring, summer) are expected to be associated with higher summer precipitation, which combined with CO2causes large increases in NPP and possibly even greater forest cover in the Mongolian steppe. In the absence of a strong direct CO2fertilization effect on plant growth (e.g., due to nutrient limitation), water stress or decreased carbon gain from higher autotrophic respiration results in decreased productivity and loss of forest cover. The fate of these semi-arid ecosystems thus appears to hinge upon the magnitude and subtleties of CO2fertilization effects, for which experimental observations in arid systems are needed to test and refine vegetation models.