Effects of soil C:N:P stoichiometry on biomass allocation in the alpine and arid steppe systems.

Xiaodan Wang,Xingxing Ma,Yan Yan

doi:10.1002/ece3.2710

Abstract

Soil nutrients strongly influence biomass allocation. However, few studies have examined patterns induced by soil C:N:P stoichiometry in alpine and arid ecosystems. Samples were collected from 44 sites with similar elevation along the 220‐km transect at spatial intervals of 5 km along the northern Tibetan Plateau. Aboveground biomass (AGB) levels were measured by cutting a sward in each plot. Belowground biomass (BGB) levels were collected from soil pits in a block of 1 m × 1 m in actual root depth. We observed significant decreases in AGB and BGB levels but increases in the BGB:AGB ratio with increases in latitude. Although soil is characterized by structural complexity and spatial heterogeneity, we observed remarkably consistent C:N:P ratios within the cryic aridisols. We observed significant nonlinear relationships between the soil N:P and BGB:AGB ratios. The critical N:P ratio in soils was measured at approximately 2.0, above which the probability of BGB:AGB response to nutrient availability is small. These findings serve as interesting contributions to the global data pool on arid plant stoichiometry, given the previously limited knowledge regarding high‐altitude regions.

Highlights

Biomass allocation is an important variable in the terrestrial ecosystem carbon cycle
Quantitative understandings of the biomass allocation patterns are of fundamental importance to ecological management (Niklas, 1994)
A linear regression analysis with soil nutrient elements as the independent parameter was conducted to test whether the soil C:N:P stoichiometry affected biomass allocation (BGB:Aboveground biomass (AGB)) levels in the alpine and arid steppe

Summary

Introduction

Biomass allocation is an important variable in the terrestrial ecosystem carbon cycle. The functional equilibrium hypothesis suggests that plants respond to variations in environmental conditions by allocating biomass at any given time across various organs to capture nutrients, water, and light and to maximize growth rates (Bloom, Chapin, & Mooney, 1985; Evans, 1972; Marcelis, Heuvelink, & Goudriaan, 1998). Based on this hypothesis, relative plant growth rates are determined by the product of the net nitrogen (N) uptake rate per unit of root mass, by plant N concentrations and by the fraction of biomass invested in roots (Garnier, 1991; McConnaughay & Coleman, 1999). Rather than considering ratios at specific times, it describes the overall relationship between the total amount of one organ (for example, the shoot mass) and another (for example, the root mass; Niklas, 1994)

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