Testing Associations of Plant Functional Diversity with Carbon and Nitrogen Storage along a Restoration Gradient of Sandy Grassland.

Xiaoan Zuo,Peng Lv,Xueyong Zhao,Xiyuan Yue,Xin Zhou,Jing Zhang,Shaokun Wang

doi:10.3389/fpls.2016.00189

Abstract

The trait-based approach shows that ecosystem function is strongly affected by plant functional diversity as reflected by the traits of the most abundant species (community-weighted mean, CWM) and functional dispersion (FDis). Effects of CWM and FDis individually support the biomass ratio hypothesis and the niche complementarity hypothesis. However, there is little empirical evidence on the relative roles of CWM traits and FDis in explaining the carbon (C) and nitrogen (N) storage in grassland ecosystems. We measured plant functional traits in the 34 most abundant species across 24 sites along a restoration gradient of sandy grassland (mobile dune, semi-fixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China. Thereafter, we calculated the CWM traits, the functional divergence of each single trait (FDvar) and the trait dispersion of multiple traits (FDis). We also measured the C and N storage in plant, litter, root, and soil. Using a stepwise multiple regression analysis, we further assessed which of the functional diversity components best explained C and N storage in the sandy grassland restoration. We found consistent links between C or N storage and leaf traits related to plant resource use strategy. However, the CWM of plant height was retained as an important predictor of C and N storage in plant, litter, soil, and total ecosystem in the final multiple models. CWMs of specific leaf area and plant height best predicted soil C and N storage and total ecosystem N storage. FDis was one of good predictors of litter C and N storage as well as total ecosystem C storage. These results suggest that ecosystem C and N pools in the sandy grassland restoration are primarily associated with the traits of the most abundant species in communities, thereby supporting the biomass ratio hypothesis. The positive associations of FDis with C storage in litter and total ecosystem provide evidence to support the niche complementarity hypothesis. Both functional traits of dominant species and traits’ dispersion in plant communities could contribute to explaining total ecosystem C storage. Thus, single- and multi-trait indices of functional composition play a crucial role in predicting C storage in sandy grasslands.

Highlights

Accelerating declines in species diversity of terrestrial ecosystem have greatly affected ecosystem function (Butchart et al, 2010; Selmants et al, 2013)
Our results suggest that the dominant species’ traits reflected by Community weighted means (CWM) are the important predictors of ecosystem C and N storage; functional dispersion (FDis) is only important for ecosystem C storage in sandy grassland restoration
Our results have clearly illustrated the important roles of CWM traits and FDis in explaining the C and N storage in sandy grassland restoration

Summary

Introduction

Accelerating declines in species diversity of terrestrial ecosystem have greatly affected ecosystem function (Butchart et al, 2010; Selmants et al, 2013). Many components of species diversity are used to access the relationship between biodiversity and ecosystem function (Tilman, 1997; Díaz et al, 2007; Mace et al, 2012). Phenological, and physiological traits in response to environmental changes, different plant species differing in their ability to capture, store and input C and N to the soil, are a major driver of C and N storage in terrestrial ecosystems (Knops et al, 2002; Cortez et al, 2007; Cornwell et al, 2008; Carrera et al, 2009; Conti and Díaz, 2013). The body of empirical evidence which focus on the relationships between plant functional diversity and C or N storage in natural grassland ecosystems is still lacking (Cavanaugh et al, 2014)

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