Use of a simulation model and ecosystem flux data to examine carbon-water interactions in ponderosa pine.
Use of a simulation model and ecosystem flux data to examine carbon-water interactions in ponderosa pine.
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DOI：
10.1093/treephys/21.5.287
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发表时间：
2001-03
期刊：
影响因子：
4
通讯作者：
M. Williams;B. Law;P. Anthoni;M. Unsworth
中科院分区：
文献类型：
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作者：
M. Williams;B. Law;P. Anthoni;M. Unsworth
干旱胁迫对森林生态系统的结构和功能起着重要的决定作用，因为碳循环和水文循环之间存在着密切的联系。我们使用了一个详细的模型，土壤-植物-大气连续体，研究碳吸收和水文循环之间的联系，在一个成熟的，开放的美国黄松（美国黄松Dougl。（法律除外）在东部俄勒冈州的Metolius河在2年期间（1996-1997）。该模型参数化的植被结构，土壤性质和气象的当地测量，并测试对独立的测量生态系统的潜在能量（LE）和碳通量和土壤含水量。虽然2年有非常不同的降水制度，每年吸收的C和总蒸腾量在这两年是相似的，根据直接观测和模拟。有重要的差异，蒸发蒸腾的比例，并在从土壤剖面的水分提取模式，取决于夏季风暴的频率。模拟结果表明，在夏末最大水分限制期间，植物保持一个显着恒定的蒸散通量，因为深生根，而C积累速率的变化是由大气蒸汽压赤字和气孔导度之间的相互作用。敏感性分析与模型建议高度保守的植被配置策略，集中在地下访问土壤体积足够大，以缓冲夏季干旱，并优化占降水的年际变化。该模型表明，增加叶面积的分配将大大提高生产力，但在某些年份会有更大的土壤水分枯竭和干旱胁迫的相关风险。通过构建稀疏的树冠和深根系统，这些林分在短期内平衡了生产力的下降，并在长期内避免了风险。
Drought stress plays an important role in determining both the structure and function of forest ecosystems, because of the close association between the carbon (C) and hydrological cycles. We used a detailed model of the soil-plant-atmosphere continuum to investigate the links between carbon uptake and the hydrological cycle in a mature, open stand of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) at the Metolius river in eastern Oregon over a 2-year period (1996-1997). The model was parameterized from local measurements of vegetation structure, soil properties and meteorology, and tested against independent measurements of ecosystem latent energy (LE) and carbon fluxes and soil water content. Although the 2 years had very different precipitation regimes, annual uptake of C and total transpiration were similar in both years, according to both direct observation and simulations. There were important differences in ratios of evaporation to transpiration, and in the patterns of water abstraction from the soil profile, depending on the frequency of summer storms. Simulations showed that, during periods of maximum water limitation in late summer, plants maintained a remarkably constant evapotranspirative flux because of deep rooting, whereas changes in rates of C accumulation were determined by interactions between atmospheric vapor pressure deficit and stomatal conductance. Sensitivity analyses with the model suggest a highly conservative allocation strategy in the vegetation, focused belowground on accessing a soil volume large enough to buffer summer droughts, and optimized to account for interannual variability in precipitation. The model suggests that increased allocation to leaf area would greatly increase productivity, but with the associated risk of greater soil water depletion and drought stress in some years. By constructing sparse canopies and deep rooting systems, these stands balance reduced productivity in the short term with risk avoidance over the long term.