Linking changes of forage production and digestibility with grassland community assembly under nitrogen enrichment

Xiao-Tao Lü,Zhuo-Yi Liu,Seeta Sistla,Yan-Yu Hu,Shuang-Li Hou,Zhi-Wei Zhang,Guo-Jiao Yang,Cong Ding

doi:10.1186/s13717-021-00308-2

Abstract

BackgroundForage production is the fundamental ecosystem service of grasslands. Although forage consumption occurs at community level, most studies focused on species-level changes of forage quality. The quantitative and qualitative changes of forage production are driven by species-specific trait, intra-specific plasticity, and species turnover. We examined the changes in forage production and digestibility after 5-year factorial treatments of nitrogen (N) addition and mowing in a temperate steppe and linked such changes to community assembly under the Price equation framework.ResultsNitrogen addition significantly reduced species richness, increased forage production, but did not change forage digestibility (indicated by the total Ca+Mg concentrations). Mowing did not affect forage production and digestibility. The positive effects of N addition on forage production were driven by the enhancement of abundance of the remaining species following N enrichment, rather than by species loss or species gain. The species identity effects could offset the effects of species richness loss or gain on forage production and digestibility.ConclusionsOur results highlight the importance of a community perspective in addressing the quantitative and qualitative changes of forage production under global change pressure of N enrichment. Species identity is important in determining the contribution of different processes of community assembly to ecosystem services.

Highlights

Grasslands, the largest terrestrial biome on earth, provide important goods and services (Gibson 2009)
Because the partitions of element concentration could not be directly summed, we evaluated the relative contribution of each Price component on the N-induced variation of community-level summing of Ca and Mg concentrations (CM) following the method of Teurlincx et al (2017), which based on the contribution of each component to the changes of nutrient content (NC) and biomass (B) in the comparison community: ΔCMpj = ((NCbase + ΔNCpj)/(Bbase + ΔBpj)) ‐ (NCbase/ Bbase) (9) in which, NCbase refers to the summing content of Ca and Mg in base community, Bbase refers to the biomass of base community, ΔNCpj refers to changes of Ca and Mg content due to the component pj, and ΔBpj refers to changes of biomass due to the component pj
The losses of species richness were due to higher species loss than species gain, with both being significantly higher than 0, indicating the occurrence of species turnover following N addition (Fig. S1)

Summary

Introduction

Grasslands, the largest terrestrial biome on earth, provide important goods and services (Gibson 2009). Forage production ranks among a fundamental grassland ecosystem service, with the productivity and quality of forage largely depending upon species diversity and community composition. Compared with our knowledge about the quantitative changes of primary production in response to the changes of biodiversity and community composition, much less is understood about its qualitative changes, such as the forage digestibility. Such knowledge gaps hinder our ability to predict the responses of grassland fundamental services to global change drivers, because both plant diversity and community composition in grasslands are sensitive to global changes (Zavaleta et al 2003). We examined the changes in forage production and digestibility after 5-year factorial treatments of nitrogen (N) addition and mowing in a temperate steppe and linked such changes to community assembly under the Price equation framework

Methods

Results

Discussion

Conclusion