Distinguishing Stoichiometric Homeostasis of Soil Microbial Biomass in Alpine Grassland Ecosystems: Evidence From 5,000 km Belt Transect Across Qinghai-Tibet Plateau.

Jihui Fan,Tianyuan Liu,Ying Liao,Yiying Li,Xuyang Lu,Yan Yan

doi:10.3389/fpls.2021.781695

Abstract

The biogeographic characteristics of soil microbial biomass stoichiometry homeostasis and also its mechanisms are commonly thought to be key factors for the survival strategies and resource utilization of soil microbes under extreme habitat. In this work, we conducted a 5,000-km transect filed survey in alpine grassland across Qinghai–Tibet Plateau in 2015 to measure soil microbial biomass carbon (MBC) and nitrogen (MBN) across alpine steppe and meadow. Based on the differences of climate and soil conditions between alpine steppe and meadow, the variation coefficient was calculated to investigate the homeostatic degree of MBC to MBN. Furthermore, the “trade-off” model was utilized to deeply distinguish the homeostasis degree of MBC/MBN between alpine steppe and meadow, and the regression analysis was used to explore the variability of trade-off in response to environmental factors in the alpine grassland. The results showed that the coefficient of variation (CV) of MBC/MBN in alpine meadow (CV = 0.4) was lower than alpine steppe (CV = 0.7). According to the trade-off model, microbial turnover activity of soil N relative to soil C increased rapidly and then decreased slightly with soil organic carbon (SOC), soil total nitrogen (STN), and soil water content across alpine meadow. Nevertheless, in alpine steppe, SOC/STN had a positive effect on microbial turnover of soil N. These results suggested that water, heat, and soil nutrients availability were the key factors affecting the C:N stoichiometry homeostasis of soil microbial biomass in Qinghai–Tibet Plateau (QTP)’s alpine grassland. Since the difference of survival strategy of the trade-off demands between soil C and N resulting in different patterns and mechanism, the stoichiometry homeostasis of soil microbial biomass was more stable in alpine meadow than in alpine steppe.

Highlights

Ecological stoichiometry focuses on the balance and limitation of energy and multiple chemical elements in various ecosystems (Agren and Weih, 2020; Zhang et al, 2020), involving competition, herbivory, mutualism, food webs, and biogeochemistry (Sterner and Elser, 2002; Zhou et al, 2021)
For the mean values of climate (MAP, aridity index (AI)) and soil (SWC, soil total nitrogen (STN), soil organic carbon (SOC), soil bulk density (SBD)) variables, MAP ranged from 295.24 to 480.16 mm (Figure 4A), AI ranged from 25.18 to 41.80 (Figure 4C), soil water content (SWC) ranged from 11.21 to 27.67% (Figure 4D), STN ranged from 1.08 to 2.38 g/kg (Figure 4E), SOC ranged from 13.47 to 39.64 g/kg (Figure 4F), and SBD ranged from 1.06 to 0.84 g/cm3 (Figure 4H) from alpine steppe to meadow based on regional study of Qinghai–Tibet Plateau (QTP)
Based on the trade-off model (Figure 2), the overall benefit was, respectively, toward MBN/STN and microbial biomass carbon (MBC)/SOC across alpine meadow and steppe, respectively (Figure 5), indicating that soil microbes tended to the turnover of soil C and N on the ecosystem scale of alpine meadow and steppe, respectively

Summary

Introduction

Ecological stoichiometry focuses on the balance and limitation of energy and multiple chemical elements in various ecosystems (Agren and Weih, 2020; Zhang et al, 2020), involving competition, herbivory, mutualism, food webs, and biogeochemistry (Sterner and Elser, 2002; Zhou et al, 2021) This theory can be quantified to research on the relationship between biology and environment, biological interaction, and biogeochemical cycle during the process of energy flow and material cycle (Crous et al, 2019; Wang et al, 2021; Zhou et al, 2021). There have existed various geographical scales of its research including individual (Abail and Whalen, 2018), population (Andersen et al, 2004), community (Fanin et al, 2017), ecosystem (Yu et al, 2010; Wang et al, 2021), national (Zhang et al, 2018), and global (Galbraith and Martiny, 2015) scale, and it has been explored in forest (Bai et al, 2019), wetland (Julian et al, 2020), grassland (Yu et al, 2011; Dijkstra et al, 2012), and aquatic (Gong et al, 2018) ecosystems

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