Journal Article

Different effects of grazing and nitrogen addition on ecosystem multifunctionality are driven by changes in plant resource stoichiometry in a typical steppe

Zhang, Xiumin, Hou, Fujiang, Hu, Junqi, Wang, Mengyuan, He, Xiong Zhao, Wang, Zhen, Li, Lan

2022

Overview

Purpose Herbivore grazing and nitrogen (N) input may alter the multiple ecosystem functions (i.e., multifunctionality, hereafter) associated with carbon (C), N, and phosphorus (P) cycling. Most studies on variations in plant diversity, soil biotic or abiotic factors, and linkages to ecosystem functions have focused on grazing or N enrichment alone. Few studies have combined these two factors to explore the role of plant resource stoichiometry (C:N:P ratios) in ecosystem multifunctionality (EMF) control. Here, we evaluated the direct and indirect effects of stocking rate (0, 2.7, 5.3, and 8.7 sheep ha − 1 ) and N addition rate (0, 5, 10, and 20 g N m − 2 yr − 1 ) on a range of ecosystem functions and EMF via changing plant diversity, soil pH and plant resource stoichiometry in a typical steppe on the Loess Plateau. Results We found that increasing stocking rate and interaction between grazing and N addition significantly decreased EMF, while increasing N addition rate significantly promoted EMF. Grazing decreased soil NH 4 + -N, soil NO 3 − -N, aboveground biomass, and plant C, N, and P pools, but increased soil total N and P at 8.7 and 5.3 sheep ha − 1 , respectively. N addition increased soil NH 4 + -N, NO 3 − -N, and total P. Plant aboveground biomass, and plant C, N, and P pools increased at the lower N addition rate (≤ 5 g N m − 2 yr − 1 ) under grazing. The structural equation models indicated that (1) EMF was driven by the direct effects of grazing and the indirect effects of grazing on plant resource stoichiometry and soil pH; (2) EMF increased with increasing N addition rates, but such positive response of EMF to increasing N addition rates was alleviated at high levels of plant resource stoichiometry and diversity; and (3) the indirect effects of plant diversity induced by grazing and N addition had moderate effects on EMF via the variations of plant resource stoichiometry. Conclusions This study demonstrated grazing and N addition had contrasting effects on ecosystem multifunctionality in a typical steppe, and highlighted the capacity of plant diversity in balancing plant elements that serve as a key mechanism in the maintenance of EMF in response to intensive grazing and N enrichment.

• Publisher: Springer Nature,Springer International Publishing,Springer,Springer Nature B.V
• Subject: Abiotic factors / aboveground biomass / Agriculture / Biological diversity / Biomass / Biomedical and Life Sciences / carbon / China / Ecological function / Ecological research / Ecology / Ecosystem components / Ecosystems / Electromagnetic fields / Environmental aspects / equations / Grazing / herbivores / Life Sciences / Low frequency / Multivariate statistical analysis / Nitrogen / Nitrogen content / Nitrogen enrichment / pH effects / Phosphorus / Plant diversity / Plant physiological ecology / Plant Physiology / Plant resources / Plant Sciences / Research Article / sheep / Soil chemistry / Soil pH / Soil Science & Conservation / Soils / species diversity / Steppes / Stoichiometry / total nitrogen