Effect of grazing removal on aboveground vegetation and soil seed bank composition in sub-alpine grasslands of northern Iran

Abstract

Background: Knowledge about vegetation and soil seed bank composition and the processes that contribute to vegetation recovery after the removal of heavy grazing is lacking in sub-alpine ecosystems.

Aims: In order to assess the effects of large herbivores on above-ground vegetation (AGV) and soil seed bank (SSB) characteristics, intensively sheep-grazed areas were compared to adjacent areas where grazing had been removed 10 years previously in a sub-alpine grassland of northern Iran.

Methods: A total of 40 4-m² (2 m × 2 m) plots were established in each treatment, and soil samples were collected from each plot within a depth of 10 cm. Plant species composition was determined for each plot during the flowering stage of herbaceous species in June 2011. The seedling emergence method was used to estimate SSB composition.

Results: A total of 45 species (23 annuals and 22 perennials) emerged from the soil samples of the grazed area, while the number of species emerged from the soil samples of the previously grazing area was 76 (37 annuals and 39 perennials). The removal of grazing led to a significant increase in species richness and seed density in the SSB. Species turnover of AGV was higher, and that of the SSB was similar for grazed areas compared with areas that were formerly grazed. Detrended correspondence analysis ordination of AGV composition showed a clearly separate structure between grazed plots and plots where grazing has been removed, while the segregation was less clear for SSB composition.

Conclusions: We concluded that restoration of locally degraded sites cannot rely on the SSB when grazing is stopped simultaneously and unvegetated gaps are colonised by vegetative growth rather than by seed.

Keywords:

• mountainous habitat
• restoration
• sheep grazing
• species richness
• species turnover

Acknowledgements

We would like to acknowledge the Iranian University of Tarbiat Modares for technical and financial support. The authors are grateful to Dr Sayed Hassan Zali for the identification of certain plant species, and to Dr Denis Poinsot, Prof. A. Prinzing and A. Nys for useful comments on earlier drafts. Special thanks to four anonymous reviewers for their valuable comments and Angus Garbutt for editing the English.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Reza Erfanzadeh

Reza Erfanzadeh is a plant ecologist. He is interested in plant diversity conservation and reservation. He studies on the recovery of vegetation by soil seed bank in very degraded-intensive grazed areas. He has also started studying on the potential of soil seed bank for restoration of grasslands after fire.

Paria Kamali

Paria Kamali is a rangeland researcher and interested in the various aspects of using of the plant communities in the rangelands (medicinal and industrial plants) and conservation of plant diversity, especially in arid and semi-arid areas.

Hassan Ghelichnia

Hassan Ghelichnia is interested in rangeland management, inventory and monitoring. He works on the plant diversity in relation to management and environmental variables. He works on plant systematic in the rangeland and forest fields.

Julien Pétillon

Julien Pétillon is a biologist. He studies on the interaction between plant and animals in the grasslands, including the ecological niche and diversity of spiders.