Increased rainfall and nitrogen alter colonization and extinction during postgrazing steppe succession

Prepared by Hong-Wei Yu & Wei-Ming He

Photos of the field experiment, northeastern Inner Mongolia, China: (a) Rainfall collectors and irrigation pipes at the beginning of the experiment, and (b) watered and fertilized experimental plots. Photo credit: Wei-Ming He.

Steppes are among the most important grassland types, and a high proportion of steppes have suffered from overgrazing. During the steppe restoration, plant species can often appear and disappear simultaneously. Meanwhile, steppe restoration is usually accompanied by the changes in rainfall and nitrogen availability. Thus, these changes can strongly influence species loss and gain during steppe restoration. Based on five-year experimental data, we found that increases in rainfall and nitrogen enhanced species loss and gain at the same time. Importantly, the rates of species loss and gain were equal, thereby allowing the total number of plant species to sustain stable. This study provides a mechanism explaining how the total number of plant species can maintain unchanged during postgrazing restoration.

Effectiveness of experimental manipulations: (c) soil water content along the rainfall gradient, (d) soil available nitrogen (including nitrate and ammonium) along the nitrogen gradient, and (e) soil pH along the nitrogen gradient. +14%: a 14% increase in rainfall amount over the ambient rainfall; +28%: a 28% increase in rainfall amount over the ambient rainfall; N5: an addition of 5 g N m-2 yr-1; N10: an addition of 10 g N m-2 yr-1. The different letters represent a significant difference at P = 0.05. Figure from the original paper.

This is a plain language summary for the paper of Hong-Wei Yu & Wei-Ming He published in the Journal of Vegetation Science (