Effects of short-term grazing exclusion on plant phenology and reproductive succession in a Tibetan alpine meadow.

Juntao Zhu,Yaojie Liu,Yangjian Zhang

doi:10.1038/srep27781

Abstract

Grazing exclusion (GE) has been widely considered as an effective avenue for restoring degraded grasslands throughout the world. GE, via modifying abiotic and biotic environments, inevitably affects phenological development. A five-year manipulative experiment was conducted in a Tibetan alpine meadow to examine the effects of GE on phenological processes and reproductive success. The study indicated that GE strongly affected phenological development of alpine plant species. Specifically, the low-growing, shallow-rooted species (LSS), such as Kobresia pygmaea, are more sensitive to GE-caused changes on upper-soil moisture and light. GE advanced each phonological process of K. pygmaea, except in the case of the treatment of fencing for 5 years (F5), which postponed the reproductive stage and lowered the reproductive success of K. pygmaea. Increased soil moisture triggered by GE, especially in the upper soil, may stimulate growth of LSS. However, the thick litter layer under the F5 treatment can influence the photoperiod of LSS, resulting in suppression of its reproductive development. These findings indicate that plant traits associated with resource acquisition, such as rooting depth and plant height, mediate plant phenology and reproductive responses to grazing exclusion treatments.

Highlights

Grazing exclusion (GE) has been widely considered as an effective avenue for restoring degraded grasslands throughout the world
Compared to the grazing treatment, grazing exclusion (GE) significantly increased litter layer depth (P < 0.05), except for F1 (Fig. 2B, P > 0.05).There were significant differences in litter layer weight and depth between treatments F5 and F4, F3 (Fig. 2, P < 0.05).The five fencing treatments caused no significant effects on total soil content of C, N, P or the C/N ratio (Table 1, P > 0.05)
As shown in the present study, the weight and depth of the litter layer increased with the length of the grazing exclusion period

Summary

Introduction

Grazing exclusion (GE) has been widely considered as an effective avenue for restoring degraded grasslands throughout the world. The thick litter layer under the F5 treatment can influence the photoperiod of LSS, resulting in suppression of its reproductive development These findings indicate that plant traits associated with resource acquisition, such as rooting depth and plant height, mediate plant phenology and reproductive responses to grazing exclusion treatments. Few studies have examined the effects of GE on plant phenology Abiotic environmental factors, such as temperature[14], water (precipitation and soil moisture)[15], photoperiod[16] and soil nutrients[17], combined with the biotic factors, such as plant life history[15], influence phenological processes and reproductive success[18]. Changes in abiotic factors can lead to significant consequences for phenological development, there is still a severe shortage of information on responses of phenological processes and reproductive success to GE, especially for the alpine grassland ecosystem.

Methods

Results

Conclusion