Modelling CO2 Impacts on Forest Productivity
Modelling CO2 Impacts on Forest Productivity
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DOI：
10.1007/s40725-015-0014-8
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发表时间：
2015-06-01
影响因子：
9.5
通讯作者：
Werner, Christian
中科院分区：
文献类型：
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作者：
Hickler, Thomas;Rammig, Anja;Werner, Christian
基于过程的模型是了解森林生态系统动态和功能的重要工具。在几乎所有的模型中，森林生产力在很大程度上是由光合作用输入的碳(C)驱动的，光合作用对二氧化碳的升高产生强烈的积极反应(ECO(2))。然而，模拟的森林生产力在木材生产方面的增长远远高于实验和观测证据所表明的水平，至少在那些没有考虑养分限制的模型中是如此。实验结果表明，在大多数被研究的系统中，ECO(2)导致了地下碳分配的增加，而没有持续地促进木材生产。这种地下碳的转移，也增强了养分的吸收，似乎比我们目前的模型中模拟的要大。然而，由于缺乏真实生态系统的实验数据，特别是来自热带的实验数据，大问题仍然没有得到解决，二氧化碳水平的增加是否已经并将导致森林生产力在林分水平的木材生长量方面大幅增加。为了减少不确定性，有必要发展新的理论，在模型中实施，并严格将模型结果与观测结果进行比较。它们的范围从生理测量，“自由空气二氧化碳增加”实验的结果，到森林清查，树木年轮和C-13分析(作为水利用效率变化的替代)。模型中需要解决的关键问题包括C和养分循环的耦合，树木碳汇容量的限制，分配的动态变化，以及树木种群动态对林分生产力的潜在反馈。
Process-based models are important tools for understanding the dynamics and functioning of forest ecosystems. In nearly all models, forest productivity is largely driven by carbon (C) input via photosynthesis, which reacts strongly positive to elevated CO2 (eCO(2)). The simulated increases in forest productivity in terms of wood production, however, have been much higher than experimental and observational evidence suggests, at least in thosemodels that did not account for nutrient limitations. Experimental results show that in most investigated systems, eCO(2) leads to increasing allocation of C below ground, without sustained enhancements of wood production. This translocation of C below ground, which also enhances nutrient uptake, appears to be larger than simulated in our current models. However, because of a lack of experimental data from real ecosystems, in particular from the tropics, the big question remains unresolved whether increasing levels of CO2 have and will lead to substantially increased forest productivity in terms of stand-level wood increment. To reduce the uncertainties, it will be necessary to develop new theory, implement that in models, and rigorously compare model results with observations. They range from physiological measurements, results from "free air CO2 enrichment" experiments to forest inventories, tree rings and C-13 analyses (as a proxy for changes in water use efficiency). Key issues that should be addressed in the models include the coupling of C and nutrient cycles, limitations to the C sink capacity of trees, dynamic changes in allocation, and potential feedbacks from tree population dynamics on stand productivity.