Ecosystem nitrogen retention is regulated by plant community trait interactions with nutrient status in an alpine meadow

Abstract

Biotic nitrogen (N) retention is an important ecosystem function in the context of ongoing land‐use intensification, N deposition and global warming. However, a paucity of experimental evidence limits understanding of how different plant community components influence N retention in terrestrial ecosystems. In this investigation, we conducted a 15N labelling experiment to test how plant community properties, including plant species richness/diversity, dominance and functional traits, influence plant N uptake and retention under different nutrient availabilities. A 3‐year experiment examined the effects of adding N (10 g N m−2 year−1) and phosphorus (P) (5 g P m−2 year−1) to an alpine meadow on the Qinghai‐Tibetan Plateau. Results show that 15N retention increased with the addition of N and P; the addition of P produced the largest increase of 15N retention in plant and soil N pools. Changes in soil nutrient conditions also facilitated different plant community controls on ecosystem N retention. Ecosystem 15N retention was influenced by species richness and root biomass in the control plots; whereas the N addition treatment showed an important effect of community‐weighted means (CWM) of specific leaf area, and plots with additional P recorded lower CWM of root nitrogen content (root N) and larger CWM root:shoot ratios as important determinants. Synthesis. Ecosystem N retention was influenced by conservative and exploitative plant species and/or their traits under N deficient and abundant conditions, respectively, whereas species richness and community plant biomass were most influential under middle condition. The discovery of an interaction between plant community traits and nutrient biogeochemistry as a mechanism for ecosystem N retention offers a means to predict how vegetation in alpine meadow ecosystems will respond to expected global change.

Revealing Fungal Communities in Alpine Wetlands through Species Diversity, Functional Diversity and Ecological Network Diversity

“…When analyzing the influence of environmental factors on the fungal community, it was found that nitrogen (nitrate, ammonium and total nitrogen) was the most important environmental factor affecting the fungal community in alpine lakeside wetlands. A large number of reports show that the diversity of nitrogen uptake patterns of plants in the Qinghai-Tibet Plateau is relatively high, thereby enriching plant diversity in the plateau [51,52]. Plants are an essential source of nutrients for soil fungal communities, and fungal communities are closely related to plant communities [53][54][55].…”

Glacier forelands reveal fundamental plant and microbial controls on short‐term ecosystem nitrogen retention

“…Thus, our findings from the late growing season may not reflect ecosystem N uptake and retention in the early growing season. The average total amount of 15 N retained in our systems was relatively high (73%) compared to N retention in temperate grasslands (Wang et al, 2018, De Vries, Bloem, et al, 2012, Templer et al, 2012, and comparable to shrubland N retention (Templer et al, 2012). However, it is important to note that we only collected intact soil cores that included plants, whereas plant cover was sparse during early successional stages.…”

Synchronous Responses of Plant Functional Traits to Nitrogen Deposition From Dominant Species to Functional Groups and Whole Communities in Alpine Grasslands on the Qinghai-Tibetan Plateau

“…Soil acidity derived directly or indirectly from N deposition ( Liu et al, 2012 ; Greaver et al, 2016 ) can lead to migration of metals, a loss of basic cations, an imbalance among N-containing compounds, and the ultimate alteration of THE composition of a plant community ( Stevens et al, 2010 ; Laliberté et al, 2014 ). N is generally known to be the limiting factor in most terrestrial ecosystems ( Jing et al, 2016 ; Wang et al, 2018 ). Some scholars believe that an increasing N deposition rate may lead to the transition from N limitation to N saturation in ecosystems ( Lu et al, 2010 ), which may benefit the coexistence of species by excluding non-nitrophilous plants ( Bobbink et al, 2010 ).…”

“…N deposition can positively affect the functional groups of grass by promoting their growth and negatively impacting other functional groups, such as forbs by limiting their growth ( Johansson et al, 2012 ; Borer et al, 2014 ; Humbert et al, 2016 ; Zhang et al, 2020 ). Until present, the limited studies from temperate and tropical forests have shown inconsistent results about the responses of the functional traits of plants to N deposition, i.e., some scholars stated that functional traits were the conductors of the N deposition on communities ( Wang et al, 2018 ), whereas some other scholars reported that plant traits were not related to N deposition ( Moreau et al, 2015 ). In addition, it is even less clear about the responses of functional traits of plants from dominant species to functional groups, and whole communities in different types of grassland to N deposition were consistent with the same or different.…”

“…As for alpine grassland ecosystems on the QTP, few researchers other than Wang et al (2018) have explored the effects of N addition on the functional traits of plants of the alpine meadow. AS is one of the most important ecosystems on the QTP, and cultivated grassland (CG) is the key intervention to prevent severe grassland degradation driven mainly by climatic change and livestock overgrazing ( Zhao et al, 2017 ; Zhang et al, 2020 ); both of them are critically important for sustainable development of both upstream and downstream regions.…”