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The state of the regional carbon cycle: Results from a constrained coupled ecosystem-atmosphere model.

机译:区域碳循环的状态:来自受约束的生态系统-大气耦合模型的结果。

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The global net uptake of carbon (C) by the terrestrial biosphere averaged 1.4 Gt C y-1 during the 1990s. Although temperate forests have been identified as significant contributors to this uptake, the underlying biological mechanisms through which this uptake has occurred have remained a matter of debate, largely because many of the spatiotemporal scales on which these mechanisms operate are not yet accessible to direct, continuous measurement. To fill this gap in our understanding, in this thesis I develop a new terrestrial biosphere model, version 2 of the Ecosystem Demography model (ED2).; I used ED2 to simulate carbon dioxide (CO2) fluxes, water fluxes, and tree growth and mortality rates at Harvard Forest. These simulation results were compared to eddy covariance data and biometry data, and model parameters were adjusted until the model was in accord with the data. The optimized model gave greatly improved predictions of net ecosystem productivity and of growth and mortality rates at both Harvard Forest (hardwood-dominated) and at Howland Forest (conifer-dominated).; I also used the model to predict regional vegetation dynamics and C fluxes. The simulated region encompassed the northeastern U.S. and southern Quebec (from 41°N to 52°N and from 80°W to 65°W). The modeled regional growth and mortality rates compared favorably to the observed rates.; I then performed a factor analysis to determine mechanisms driving interannual variability in the regional C fluxes. I found that meteorological variability had a strong, non-linear effect, suppressing both photosynthesis and respiration. The interannual variability in the total land-atmosphere C flux was primarily controlled by interannual variability in heterotrophic respiration. In particular, the years in which the land most strongly acted as a C sink were the years in which dry summers most strongly suppressed heterotrophic respiration.; Finally, I investigated the atmospheric signatures of CO2 fluxes using ED2 coupled to a new, mass-conserving version of the Regional Atmospheric Modeling System developed here. The coupled model successfully predicted altitudinal gradients of CO2 as observed by aircraft under a variety of meteorological conditions, but it underpredicted the gradient on several sunny, warm days.
机译:在1990年代,陆地生物圈的全球净碳吸收(C)平均为1.4 Gt C y-1。尽管已确定温带森林是这种吸收的重要贡献者,但发生这种吸收的基本生物学机制仍存在争议,主要是因为这些机制所依据的许多时空尺度尚无法直接,连续地获得。测量。为了填补我们的理解中的空白,在本文中,我开发了一个新的陆地生物圈模型,即生态系统人口统计学模型(ED2)的版本2。我使用ED2来模拟哈佛森林中的二氧化碳(CO2)通量,水通量以及树木生长和死亡率。将这些仿真结果与涡动协方差数据和生物特征数据进行比较,并调整模型参数,直到模型与数据一致为止。优化的模型大大改善了哈佛森林(硬木为主)和豪兰森林(针叶树为主)的净生态系统生产力以及增长率和死亡率的预测。我还使用该模型预测了区域植被动态和碳通量。模拟区域包括美国东北部和魁北克南部(从41°N到52°N和从80°W到65°W)。建模的区域增长率和死亡率与观察到的比率相比是有利的。然后,我进行了因子分析,以确定驱动区域C通量年际变化的机制。我发现气象变异具有强烈的非线性效应,抑制了光合作用和呼吸作用。陆地总大气C通量的年际变化主要受异养呼吸的年际变化控制。特别是,土地最强地充当碳汇的年份是干旱的夏季最强烈地抑制异养呼吸的年份。最后,我使用ED2和此处开发的区域节约大气模型系统的一种新的,节省质量的方法,研究了ED2与CO2通量的大气特征。耦合模型成功地预测了在各种气象条件下飞机观测到的CO2的垂直梯度,但在几个晴天,温暖的日子却预测不足。

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