The effect of vertically resolved soil biogeochemistry and alternate soil C and N models on C dynamics of CLM4

[摘要] Soils are a crucial component of the Earth system; they comprise a largeportion of terrestrial carbon stocks, mediate the supply and demand ofnutrients, and influence the overall response of terrestrial ecosystems toperturbations. In this paper, we develop a new soil biogeochemistry model forthe Community Land Model, version 4 (CLM4). The new model includes a verticaldimension to carbon (C) and nitrogen (N) pools and transformations, a morerealistic treatment of mineral N pools, flexible treatment of the dynamics ofdecomposing carbon, and a radiocarbon (¹⁴C) tracer. We describe themodel structure, compare it with site-level and globalobservations, and discuss the overalleffect of the revised soil model on Community Land Model (CLM) carbondynamics. Site-level comparisons to radiocarbon and bulk soil C observationssupport the idea that soil C turnover is reduced at depth beyond what isexpected from environmental controls for temperature, moisture, and oxygenthat are considered in the model. In better agreement with observations, therevised soil model predicts substantially more and older soil C, particularlyat high latitudes, where it resolves a permafrost soil C pool. In addition,the 20th century-C dynamics of the model are more realistic than those of thebaseline model, with more terrestrial C uptake over the 20th century due toreduced N downregulation and longer turnover times for decomposing C.

[学科分类] 地球化学与岩石