The Similarity between Species Composition of Vegetation and Soil Seed Bank of Grasslands in Inner Mongolia, China: Implications for the Asymmetric Response to Precipitation.

Menghong Shen,Jingrong Li,Huifang Zhang,Yanyan Lv,Baoping Meng,Jianguo Zhang,Yi Sun,Shuhua Yi,Li Chang

doi:10.3390/plants10091890

Abstract

The asymmetric response of productivity to precipitation was recently proposed as an early warning signal for the shifts in temperate grassland function in China. It was hypothesized that the asymmetry was influenced by the increased growth of the newly emerged seedlings from the soil seed bank. Therefore, the seed density in the soil seed bank and the similarity between species composition of the vegetation and the soil seed bank should be maximized where asymmetry was maximized. However, this knowledge was still limited and unconfirmed. In this study, the desert steppe, typical steppe and the transition zone between them (with the highest asymmetry) were selected for studying the similarity index in both 2018 (dry year) and 2019 (wet year). Plant species composition was monitored in situ using an unmanned aerial vehicle. Soil seed bank samples were collected, and the seed bank density and species composition were then examined and identified in the laboratory. Results showed that: (1) The variation in vegetation species richness between the two years was the highest (41%) in the transition zone (p < 0.05), while it was only 7% and 13% for the desert steppe and typical steppe, respectively. The presence of herbaceous species mainly caused the differences in variation among three grassland types. (2) Seed density was the highest in the transition zone (114 seeds/m2 and 68 seeds/m2 in the transient and persistent soil seed bank, respectively) (p < 0.05). Additionally, herbaceous species were the main components of the soil seed bank. (3) The similarity index was the highest in the transition zone (p < 0.05), with 38%/44% and 33%/44% for the transient/persistent soil seed bank in 2018 and 2019, respectively. Our study demonstrated that variation in vegetation species composition was very similar to the composition of the seeds accumulated in the soil seed bank. These results warrant further investigation for the mechanism of asymmetric response of productivity to precipitation.

Highlights

Grasslands play a crucial role in both carbon and water cycles
These results suggested that in the extremely dry years the zone was more similar to the desert steppe, and in extremely wet years it was more similar to the typical steppe
To test the hypothesis [13] of whether new seedlings or the growth of the existing plants contribute to the asymmetry, the dynamic changes in vegetation species and their normalized difference vegetation index (NDVI) should be monitored

Summary

Introduction

Grasslands play a crucial role in both carbon and water cycles. The semi-arid and arid grasslands are experiencing frequent and intense droughts [1,2], which inevitably cause changes in the function, structure, and composition of grassland ecosystems [3,4,5]. Hu et al (2018) found that the asymmetry was maximized at the transition zone between the desert steppe and typical steppe in Inner Mongolia, China [13], and it was proposed to be such a warning signal for the temperate grassland ecosystems [13]. These results suggested that in the extremely dry years the zone was more similar to the desert steppe, and in extremely wet years it was more similar to the typical steppe.

Objectives

Methods

Results

Discussion

Conclusion