Can Overgrazing Responses Be Disentangled by Above- and Below-Ground Traits?

Hui Zhang,Shree Prakash Pandey,Qifang He,Kai Jiang,Chen Wang

doi:10.3389/fevo.2021.573948

Hui Zhang, Shree Prakash Pandey + Show 3 more

Open Access

https://doi.org/10.3389/fevo.2021.573948

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Abstract

Understanding functional traits that capture species response to overgrazing can help optimize ecosystem functioning. However, most studies have ignored the effects of life-form on the response of above- and below-ground traits to overgrazing. Here, we determined whether the above- and below-ground traits respond similarly to overgrazing; and does the response of above- and below-ground traits to overgrazing vary between the species of annual vs. perennial life-forms. We compared common grassland species between fenced and overgrazed meadows at four elevations (from 3000 to 3600 m), spanning an area of ∼200 square kilometers on the Qinghai-Tibetan Plateau. We found overgrazing resulted in large removal of perennial species at all elevations, which forced perennial species to alter their above- and below-ground traits so that they could shift from resource conservation to resource acquisition to avoid overgrazing. In contrast, overgrazing promoted annual species at all elevation, thus annual species did not make any response to overgrazing. These findings bridge the gap in the literature for the influence of annual vs. perennial life-forms on species-specific response at both above-, and below-ground levels during overgrazing. More important, these results can facilitate selecting species for sustainable ecosystem managements and restoration from overgrazing.

Highlights

Optimizing ecosystem functions has become a challenging task for agro-ecosystem management, as demands for food supply are ever-increasing (Orwin et al, 2018)
When dividing all species into annual and perennial species separately, we found annual species was promoted in the overgrazed meadow
When performing principal component analysis (PCA) separately for annual and perennial species, we found that perennial species in fenced and overgrazed meadows were significantly separated by all the above- and below-ground traits measured at all elevations (Figure 4 and Supplementary Table 2)

Summary

Introduction

Optimizing ecosystem functions (e.g., productivity and nitrogen retention) has become a challenging task for agro-ecosystem management, as demands for food supply are ever-increasing (Orwin et al, 2018). Understanding of functional traits that capture responses of species to overgrazing can help in understanding vegetation composition dynamics. This in turn requires better understanding of above- and below-ground traits that respond to overgrazing as compared to landscapes that are not overgrazed (Orwin et al, 2010; Mouillot et al, 2011). Use of the key functional traits that can capture species-specific response to overgrazing can help in selecting species to restoration from overgrazing (Orwin et al, 2018)

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