Impacts of nitrogen deposition on terrestrial plant diversity: a meta-analysis in China

Abstract

Aims With the global atmospheric nitrogen (N) deposition increasing, the effect of N deposition on terrestrial plant diversity has been widely studied. Some studies have reviewed the effects of N deposition on plant species diversity; however, all studies addressed the effects of N deposition on plant community focused on species richness in specific ecosystem. There is a need for a systematic meta-analysis covering multiple dimensions of plant diversity in multiple climate zones and ecosystems types. Our goal was to quantify changes in species richness, evenness and uncertainty in plant communities in response to N addition across different environmental and experimental contexts. Methods We performed a meta-analysis of 623 experimental records published in English and Chinese journals to evaluate the response of terrestrial plant diversity to the experimental N addition in China. Three metrics were used to quantify the change in plant diversity: species richness (SR), evenness (Pielou index) uncertainty (Shannon index). Important Findings Results showed that (i) N addition negatively affected SR in temperate, Plateau zones and subtropical zone, but had no significant effect on Shannon index in subtropical zones; (ii) N addition decreased SR, Shannon index and Pielou index in grassland, and the negative effect of N addition on SR was stronger in forest than in grassland; (iii) N addition negatively affected plant diversity (SR, Shannon index and Pielou index) in the long term, whereas it did not affect plant diversity in the short term. Furthermore, the increase in N addition levels strengthened the negative effect of N deposition on plant diversity with long experiment duration; and (iv) the negative effect of ammonium nitrate (NH4NO3) addition on SR was stronger than that of urea (CO(NH2)2) addition, but the negative effect of NH4NO3 addition on Pielou index was weaker than that of CO(NH2)2 addition. Our results indicated that the effects of N addition on plant diversity varied depending on climate zones, ecosystem types, N addition levels, N type and experiment duration. This underlines the importance of integrating multiple dimensions of plant diversity and multiple factors into assessments of plant diversity to global environmental change.

Microbial mediators of plant community response to long‐term N and P fertilization: Evidence of a role of plant responsiveness to mycorrhizal fungi

“…Although elevated N and P could promote plant productivity as most natural terrestrial land areas are N and P limited (Du et al, 2020), soil N and P loadings threaten biodiversity and ecosystem functions important to human well-being (Tilman & Lehman, 2001). Plant diversity and plant community stability have been shown to decline with N (Han et al, 2019;Isbell et al, 2013;Reich, 2009;Simkin et al, 2016) and P accumulation (Ceulemans et al, 2014;Gilbert et al, 2009). Diversity loss in response to nutrient enrichment is often accompanied by changes in species composition, with native and perennial grassland species frequently showing greater vulnerability to decline than non-native or annual species (Avolio et al, 2014;Bai et al, 2010;Clark & Tilman, 2008;Flores-Moreno et al, 2016;Foster et al, 2011).…”

Global negative effects of nutrient enrichment on arbuscular mycorrhizal fungi, plant diversity and ecosystem multifunctionality

“…Nutrient addition results in increased aboveground biomass, and subsequent aboveground competition for light changes the plant community and results in reduced species richness (Suding et al ., 2005; Hautier et al ., 2009; Borer et al ., 2014). In addition, nutrient addition also may reduce plant diversity through soil acidification, ammonium toxicity, altered plant–soil relationships, and increased sensitivity to secondary stress such as pests and drought and other disturbances (Soons et al ., 2017; Han et al ., 2019; Midolo et al ., 2019). However, responses of AMF to nutrient enrichment are highly variable.…”

Environmental impacts of nitrogen emissions in China and the role of policies in emission reduction

“…In an old-growth subtropical forest in southern China, N additions of greater than 100 kg N ha −1 yr −1 decreased the abundance of understory seedlings, ferns and mosses, but did not affect canopy trees and shrubs [116]. A recent meta-analysis of experimental results in China concluded that N addition negatively affected plant biodiversity in grasslands and forest understory communities; the effects varied by climatic zone, N addition level and duration [117]. However, there are relatively few reports from eastern and southern China [117], where high-level N deposition has occurred for decades.…”

“…A recent meta-analysis of experimental results in China concluded that N addition negatively affected plant biodiversity in grasslands and forest understory communities; the effects varied by climatic zone, N addition level and duration [117]. However, there are relatively few reports from eastern and southern China [117], where high-level N deposition has occurred for decades. In these regions, N addition experiments likely underestimate the negative effects because high-level N deposition may have already caused a shift in plant species composition towards that better adapted to high N availability before the experiments began.…”