Biogeophysical feedbacks trigger shifts in the modelled vegetation-atmosphere system at multiple scales
Biogeophysical feedbacks trigger shifts in the modelled vegetation-atmosphere system at multiple scales
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DOI：
10.5194/bg-7-1237-2010
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发表时间：
2010-01-01
期刊：
影响因子：
4.9
通讯作者：
Rietkerk, M.
中科院分区：
文献类型：
--
作者：
Dekker, S. C.;de Boer, H. J.;Rietkerk, M.
陆地植被通过改变辐射、动量和水文平衡来影响气候。本文有助于正在进行的辩论的问题，是否积极的植被和气候之间的地球物理反馈可能会导致植被和气候的多重平衡和随之而来的突然政权的转变。一些模拟研究认为，在地方到区域尺度上的植被-气候反馈可能足够强大，可以在气候系统中建立多个状态。中等复杂性地球模型PlaSim用于研究区域到全球尺度气候系统对植被干扰的恢复力。我们假设，通过两个极端的初始化的生物量，积极的植被气候反馈将保持在不同的吸引域的植被-大气系统。事实上，从不同的初始生物量分布开始的模型集成发散到明显不同的气候-植被状态的非生物（降水和温度）和生物（生物量）变量。此外，我们发现，在这些状态之间有几个其他的稳定状态，依赖于微扰的规模。从这里绘制了全球易感性地图，显示了低弹性和高弹性的区域。模型的结果表明，主要是北方和季风地区有低的干扰，即不稳定的生物量平衡，与积极的植被气候反馈，其中扰动引起的生物量进一步加强。扰动不仅影响单个植被-气候单元的相互作用，而且由于相邻单元构成空间植被-气候反馈，还引起大气环流空间格局的变化。大的扰动可能会触发系统向另一个稳定状态的突然转变。虽然在我们的模拟中使用的模型设置是相当简单的，我们的研究结果强调，耦合的反馈在多个尺度的植被气候模型是必不可少的，迫切需要了解系统动力学的改善预测的生态系统响应的人为气候强迫的变化。
Terrestrial vegetation influences climate by modifying the radiative-, momentum-, and hydrologic-balance. This paper contributes to the ongoing debate on the question whether positive biogeophysical feedbacks between vegetation and climate may lead to multiple equilibria in vegetation and climate and consequent abrupt regime shifts. Several modelling studies argue that vegetation-climate feedbacks at local to regional scales could be strong enough to establish multiple states in the climate system. An Earth Model of Intermediate Complexity, PlaSim, is used to investigate the resilience of the climate system to vegetation disturbance at regional to global scales. We hypothesize that by starting with two extreme initialisations of biomass, positive vegetation-climate feedbacks will keep the vegetation-atmosphere system within different attraction domains. Indeed, model integrations starting from different initial biomass distributions diverged to clearly distinct climate-vegetation states in terms of abiotic (precipitation and temperature) and biotic (biomass) variables. Moreover, we found that between these states there are several other steady states which depend on the scale of perturbation. From here global susceptibility maps were made showing regions of low and high resilience. The model results suggest that mainly the boreal and monsoon regions have low resiliences, i.e. instable biomass equilibria, with positive vegetation-climate feedbacks in which the biomass induced by a perturbation is further enforced. The perturbation did not only influence single vegetation-climate cell interactions but also caused changes in spatial patterns of atmospheric circulation due to neighbouring cells constituting in spatial vegetation-climate feedbacks. Large perturbations could trigger an abrupt shift of the system towards another steady state. Although the model setup used in our simulation is rather simple, our results stress that the coupling of feedbacks at multiple scales in vegetation-climate models is essential and urgent to understand the system dynamics for improved projections of ecosystem responses to anthropogenic changes in climate forcing.