Nitrogen addition increases sexual reproduction and improves seedling growth in the perennial rhizomatous grass Leymus chinensis

Song Gao,Jiao Wang,Junfeng Wang,Johannes M. H. Knops

doi:10.1186/s12870-020-2307-8

Abstract

BackgroundThe Eurasian steppe is an important vegetation type characterized by cold, arid and nitrogen poor conditions. At the Eastern edge, including in the Songnen grassland, the vegetation is dominated by Leymus chinensis (henceforth L. chinensis) and is increasing threatened by elevated anthropogenic nitrogen deposition. L. chinensis is a perennial grass that mainly reproduces vegetatively and its sexual reproduction is limited. However, sexual reproduction plays an important role influencing colonization after large disturbances. To develop an understanding of how elevated nitrogen deposition changes the plant community structure and functioning we need a better understanding how sexual reproduction of L. chinensis changes with nitrogen enrichment. Here we report on a field experiment where we added 10 g N m− 2 yr− 1 and examined changes in seed traits, seed germination and early seedling growth.ResultsNitrogen addition increased seed production by 79%, contributing to this seed increases were a 28% increase in flowering plant density, a 40% increase in seed number per plant and a 11% increase in seed weight. Seed size increased with a 42% increase in large seeds and a 49% decrease in the smallest seed size category. Seed germination success improved by 10% for small seeds and 18% for large seeds. Combined, the increased in seed production and improved seed quality doubled the potential seed germination. Subsequent seedling above and below-ground biomass also significantly increased.ConclusionsAll aspects of L. chinensis sexual reproduction increased with nitrogen addition. Thus, L. chinensis competitive ability may increase when atmospheric nitrogen deposition increases, which may further reduce overall plant diversity in the low diversity Songnen grasslands.

Highlights

The Eurasian steppe is an important vegetation type characterized by cold, arid and nitrogen poor conditions
In many grasslands, the diversity of the vegetation is driven by a diversity of low abundance broadleaf forbs, whereas most of the biomass is contributed by a low diversity of grasses [1]
Some aspects of sexual reproduction such as the flowering plant number and seed density varied among the years, whereas the seed number per plant and thousand seed weight did not vary among the years (Table 1)

Summary

Introduction

The Eurasian steppe is an important vegetation type characterized by cold, arid and nitrogen poor conditions. L. chinensis is a perennial grass that mainly reproduces vegetatively and its sexual reproduction is limited. In more stressful grasslands, such as the Songnen grasslands, which have a high pH, arid climate and strong nitrogen limitation [2], the overall plant diversity is low and the grass component can be dominated by a single species, such as L. chinensis [3]. In such a vegetation the structure and functioning of the entire ecosystem is closely associated with the traits and ecology of the dominant species. Larger seeds are beneficial because of increased seedling growth especially under unfavorable conditions [7]

Methods

Results

Discussion

Conclusion