Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA.
Glob Chang Biol. 2020 Aug;26(8):4478-4494. doi: 10.1111/gcb.15188. Epub 2020 Jun 20.
Tropical forests are a key determinant of the functioning of the Earth system, but remain a major source of uncertainty in carbon cycle models and climate change projections. In this study, we present an updated land model (LM3PPA-TV) to improve the representation of tropical forest structure and dynamics in Earth system models (ESMs). The development and parameterization of LM3PPA-TV drew on extensive datasets on tropical tree traits and long-term field censuses from Barro Colorado Island (BCI), Panama. The model defines a new plant functional type (PFT) based on the characteristics of shade-tolerant, tropical tree species, implements a new growth allocation scheme based on realistic tree allometries, incorporates hydraulic constraints on biomass accumulation, and features a new compartment for tree branches and branch fall dynamics. Simulation experiments reproduced observed diurnal and seasonal patterns in stand-level carbon and water fluxes, as well as mean canopy and understory tree growth rates, tree size distributions, and stand-level biomass on BCI. Simulations at multiple sites captured considerable variation in biomass and size structure across the tropical forest biome, including observed responses to precipitation and temperature. Model experiments suggested a major role of water limitation in controlling geographic variation forest biomass and structure. However, the failure to simulate tropical forests under extreme conditions and the systematic underestimation of forest biomass in Paleotropical locations highlighted the need to incorporate variation in hydraulic traits and multiple PFTs that capture the distinct floristic composition across tropical domains. The continued pressure on tropical forests from global change demands models which are able to simulate alternative successional pathways and their pace to recovery. LM3PPA-TV provides a tool to investigate geographic variation in tropical forests and a benchmark to continue improving the representation of tropical forests dynamics and their carbon storage potential in ESMs.
热带森林是地球系统功能的关键决定因素，但仍然是碳循环模型和气候变化预测中的主要不确定性来源。在本研究中，我们提出了一个更新的陆地模型（LM3PPA-TV），以改进地球系统模型（ESMs）中对热带森林结构和动态的表示。LM3PPA-TV 的开发和参数化利用了来自巴拿马巴罗科罗拉多岛（BCI）的大量热带树种特征和长期野外普查数据集。该模型基于耐荫热带树种的特征定义了一种新的植物功能型（PFT），实现了基于实际树木异速生长的新生长分配方案，纳入了对生物量积累的水力限制，并为树枝和树枝掉落动态创建了一个新的隔室。模拟实验再现了 BCI 上林分水平碳和水通量的日变化和季节性模式，以及平均冠层和林下树木的生长速率、树木大小分布和林分水平的生物量。在多个地点的模拟捕捉到了热带森林生物群落中生物量和大小结构的相当大的变化，包括对降水和温度的观察到的响应。模型实验表明，水分限制在控制森林生物量和结构的地理变异方面起着主要作用。然而，模型未能模拟极端条件下的热带森林，以及对古热带地区森林生物量的系统低估，突出了需要纳入水力特征和多个 PFT 的变化，以捕捉热带地区不同的植物区系组成。全球变化对热带森林的持续压力要求模型能够模拟替代的演替途径及其恢复的速度。LM3PPA-TV 提供了一种工具，用于研究热带森林的地理变异，并为继续提高 ESMs 中热带森林动态及其碳储存潜力的表示提供基准。
