Modeling demographic-driven vegetation dynamics and ecosystem biogeochemical cycling in NASA GISS's Earth system model (ModelE-BiomeE v.1.0)

Abstract

Abstract. We developed a demographic vegetation model, BiomeE, to improve the modeling of vegetation dynamics and ecosystem biogeochemical cycles in the NASA Goddard Institute of Space Studies' ModelE Earth system model. This model includes the processes of plant growth, mortality, reproduction, vegetation structural dynamics, and soil carbon and nitrogen storage and transformations. The model combines the plant physiological processes of ModelE's original vegetation model, Ent, with the plant demographic and ecosystem nitrogen processes that have been represented in the Geophysical Fluid Dynamics Laboratory's LM3-PPA. We used nine plant functional types to represent global natural vegetation functional diversity, including trees, shrubs, and grasses, and a new phenology model to simulate vegetation seasonal changes with temperature and precipitation fluctuations. Competition for light and soil resources is individual based, which makes the modeling of transient compositional dynamics and vegetation succession possible. Overall, the BiomeE model simulates, with fidelity comparable to other models, the dynamics of vegetation and soil biogeochemistry, including leaf area index, vegetation structure (e.g., height, tree density, size distribution, and crown organization), and ecosystem carbon and nitrogen storage and fluxes. This model allows ModelE to simulate transient and long-term biogeophysical and biogeochemical feedbacks between the climate system and land ecosystems. Furthermore, BiomeE also allows for the eco-evolutionary modeling of community assemblage in response to past and future climate changes with its individual-based competition and demographic processes.

Demographic disequilibrium and growth-mortality asymmetry of forests across climate gradients

“…The former are better understood as they act at shorter timescales and have been extensively studied with models and experiments, whereas the latter act at longer time scales and usually exhibit uncoupling with the former(4), making them the main source of uncertainty in forest performances. Although forest demography has long been investigated and is getting increasingly concerned in Earth system models in recent years (3,(6)(7)(8)(9), our knowledges are still quite limited in the laws governing tree growth and mortality along climate gradients and their consequences on forest structure dynamics.…”

“…It In mathematics, difficulties in solving the PDE model derive from the definition on the boundary condition (i.e., saplings recruitment). Current studies of forest dynamic modeling usually define recruitment as a function of reproduction with detailed considerations on the age-or size-specific reproductivity of different species (8,9,21,24). This introduces a great deal of complexity to the model solution.…”

Feasibility of Formulating Ecosystem Biogeochemical Models From Established Physical Rules

“…Additionally, in most existing EBMs, plant canopies are at best represented with only two big leaves, one sun‐lit and the other shaded (i.e., the two‐big‐leaf approximation; (e.g., Dai et al., 2004), while fine roots are only included implicitly via parameterizations (Wang et al., 2010; Weng et al., 2022; Zhu et al., 2019). As a result, ecosystem performance associated with different canopy structures and root traits cannot be assessed with these models.…”