Robust Ecosystem Demography (RED version 1.0): a parsimonious approach to modelling vegetation dynamics in Earth system models
Robust Ecosystem Demography (RED version 1.0): a parsimonious approach to modelling vegetation dynamics in Earth system models
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DOI：
10.5194/gmd-13-4067-2020
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发表时间：
2020-09-07
影响因子：
5.1
通讯作者：
Cox, Peter M.
中科院分区：
文献类型：
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作者：
Argles, Arthur P. K.;Moore, Jonathan R.;Cox, Peter M.
气候预测的不确定性很大一部分来自土地碳吸收表示的不确定性。动态全球植被模型（DGVM）在其代表的再生和竞争的资源，这导致不同的响应大气CO2和气候的变化。更先进的基于队列的补丁模型现在正在最新的DGVM中建立。这些模型通常试图模拟树木的大小分布，作为树木大小（质量或树干直径）和年龄（自干扰以来的时间）的函数。这种方法可以捕捉到随机干扰事件对森林结构和生物量的整体影响，但在更新二维概率密度函数（pdf）时，增加了参数的数量和模糊性的成本。在这里，我们提出了强大的生态系统人口统计（RED），其中的PDF被折叠到单一维度的树质量。RED的目的是保留更复杂的队列DGVM代表森林人口的能力，同时也是参数稀疏和分析可解的稳定状态。每个植物功能类型（PFT）的人口被划分为质量类与固定的基线死亡率沿着与假设的幂律缩放的增长率与质量。RED的分析平衡解允许使用单一参数-参考质量（mu（0））的树木的死亡率与生长率之比-根据观察到的森林覆盖率校准模型。我们表明，RED因此可以校准到ESA LC_CCI（欧洲航天局土地覆盖气候变化倡议）覆盖数据集的9个PFT。使用净初级生产力和凋落物输出从英国地球系统模型（UKESM），我们能够诊断的空间变化的干扰率与此观察到的植被图相一致。RED的解析形式绕过了旋转数值模型的需要，使其在地球系统模型（ESM）中的应用具有吸引力。特别是当模型参数也是高度稀疏的时候。
A significant proportion of the uncertainty in climate projections arises from uncertainty in the representation of land carbon uptake. Dynamic global vegetation models (DGVMs) vary in their representations of regrowth and competition for resources, which results in differing responses to changes in atmospheric CO2 and climate. More advanced cohort-based patch models are now becoming established in the latest DGVMs. These models typically attempt to simulate the size distribution of trees as a function of both tree size (mass or trunk diameter) and age (time since disturbance). This approach can capture the overall impact of stochastic disturbance events on the forest structure and biomass but at the cost of increasing the number of parameters and ambiguity when updating the probability density function (pdf) in two dimensions. Here we present the Robust Ecosystem Demography (RED), in which the pdf is collapsed onto the single dimension of tree mass. RED is designed to retain the ability of more complex cohort DGVMs to represent forest demography, while also being parameter sparse and analytically solvable for the steady state. The population of each plant functional type (PFT) is partitioned into mass classes with a fixed baseline mortality along with an assumed power-law scaling of growth rate with mass. The analytical equilibrium solutions of RED allow the model to be calibrated against observed forest cover using a single parameter - the ratio of mortality to growth for a tree of a reference mass (mu(0)). We show that RED can thus be calibrated to the ESA LC_CCI (European Space Agency Land Cover Climate Change Initiative) coverage dataset for nine PFTs. Using net primary productivity and litter outputs from the UK Earth System Model (UKESM), we are able to diagnose the spatially varying disturbance rates consistent with this observed vegetation map. The analytical form for RED circumnavigates the need to spin up the numerical model, making it attractive for application in Earth system models (ESMs). This is especially so given that the model is also highly parameter sparse.