Improved representation of phosphorus exchange on soil mineral surfaces reduces estimates of phosphorus limitation in temperate forest ecosystems

[摘要] Phosphorus (P) availability affects the response ofterrestrial ecosystems to environmental and climate change (e.g., elevatedCO 2 ), yet the magnitude of this effect remains uncertain. Thisuncertainty arises mainly from a lack of quantitative understanding of thesoil biological and geochemical P cycling processes, particularly the Pexchange with soil mineral surfaces, which is often described by a Langmuirsorption isotherm. We first conducted a literature review on P sorption experiments andterrestrial biosphere models (TBMs) using a Langmuir isotherm. We thendeveloped a new algorithm to describe the inorganic P exchange between soilsolution and soil matrix based on the double-surface Langmuir isotherm andextracted empirical equations to calculate the sorption capacity andLangmuir coefficient. We finally tested the conventional and new models of Psorption at five beech forest sites in Germany along a soil P stock gradientusing the QUINCY (QUantifying Interactions between terrestrial NutrientCYcles and the climate system) TBM. We found that the conventional (single-surface) Langmuir isotherm approachin most TBMs largely differed from P sorption experiments regarding thesorption capacities and Langmuir coefficients, and it simulated an overly low soilP-buffering capacity. Conversely, the double-surface Langmuir isothermapproach adequately reproduced the observed patterns of soil inorganic Ppools. The better representation of inorganic P cycling using the double-surfaceLangmuir approach also improved simulated foliar N and P concentrations as well asthe patterns of gross primary production and vegetation carbon across thesoil P gradient. The novel model generally reduces the estimates of Plimitation compared with the conventional model, particularly at the low-Psite, as the model constraint of slow inorganic P exchange on plantproductivity is reduced.

[学科分类] 大气科学