Abstract
AbstractLand surface models (LSMs) are a vital tool for understanding, projecting, and predicting the dynamics of the land surface and its role within the Earth system, under global change. Driven by the need to address a set of key questions, LSMs have grown in complexity from simplified representations of land surface biophysics to encompass a broad set of interrelated processes spanning the disciplines of biophysics, biogeochemistry, hydrology, ecosystem ecology, community ecology, human management, and societal impacts. This vast scope and complexity, while warranted by the problems LSMs are designed to solve, has led to enormous challenges in understanding and attributing differences between LSM predictions. Meanwhile, the wide range of spatial scales that govern land surface heterogeneity, and the broad spectrum of timescales in land surface dynamics, create challenges in tractably representing processes in LSMs. We identify three “grand challenges” in the development and use of LSMs, based around these issues: managing process complexity, representing land surface heterogeneity, and understanding parametric dynamics across the broad set of problems asked of LSMs in a changing world. In this review, we discuss progress that has been made, as well as promising directions forward, for each of these challenges.
Highlights
The land surface is the only part of the Earth system that is directly experienced by the majority of humans, terrestrial animals, and plants
Driven by the need to address a set of key questions, Land surface models (LSMs) have grown in complexity from simplified representations of land surface biophysics to encompass a broad set of interrelated processes spanning the disciplines of biophysics, biogeochemistry, hydrology, ecosystem ecology, community ecology, human management, and societal impacts
We identify three “grand challenges” in the development and use of LSMs, based around these issues: managing process complexity, representing land surface heterogeneity, and understanding parametric dynamics across the broad set of problems asked of LSMs in a changing world
Summary
The land surface is the only part of the Earth system that is directly experienced by the majority of humans, terrestrial animals, and plants. Representations of numerous processes that are known to impact the dynamics of systems relevant to these questions have been incrementally added to LSMs. As a result, land surface models have expanded from their initial simple biophysical configurations (Sellers et al, 1986), to include representations of soil moisture dynamics, stomatal functioning, land surface heterogeneity, surface hydrological processes, plant and soil carbon cycling, dynamic vegetation distributions, fire, urban environments, land cover and management, nitrogen cycling and crops (Lawrence et al, 2019, Figure 1), and latterly plant demographic processes (Fisher et al, 2018; Sato et al, 2007; Weng et al, 2017), phosphorus cycling, (Goll et al, 2017; Reed et al, 2015; Yang et al, 2014), and plant hydraulics (Joetzjer et al, 2018; Kennedy et al, 2019). Within each of these three “grand challenges” we describe the nature of the challenge, illustrate ongoing developments, and propose pathways within which research and model development might best be structured to meet the important but comprehensively difficult task of predicting the future of the terrestrial surface and biosphere
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