| Grassland ecosystem is a main part of the global ecosystem,which provides many ecological goods and services for animals,plants and human.Grazing has caused 80%grassland degradation in different degrees without effective fencing and grazing ban to restore it in China.Precipitation pattern changes,as an important phenomenon of global climate change,have an important impact on grassland ecosystem.Studying the effects of precipitation changes on grassland plant ecosystem and soil microbial communities during the restoration of degraded steppe,provides a theoretical basis for understanding the impact of global climate change on grassland ecosystem,rational utilization of grassland resources and implementation of measures for biodiversity conservation and restoration of degraded grassland.This study is based on the field control test platform to simulating precipitation changes in the natural restoration area of typical degraded grassland in Xilingol League,three rainfall levels were set for the experiment(natural precipitation,50% increase of precipitation and 50% decrease of precipitation).To investigate the effects of precipitation changes on plant diversity,grassland productivity,soil physicochemical properties,soil bacterial community and soil fungal community structure and their diversities in the restoration process of typical degraded steppe.The main results are as follows:1.There was a significant positive linear correlation between precipitation and grassland productivity,plant community,plant diversity,plant richness.Ggrassland productivity increased significantly in the second year.The increase of precipitation promoted the restoration of grassland productivity,plant community diversity and richness,induced dominant species of degraded steppe vegetation were changed from Artemisia frigida to Leymus chinensis and Leymus chinensis.In addition,Soil temperature and p H decreased significantly with the duration of grazing ban.The soil p H and soil water content were significantly decreased and the soil organic matter content was significantly increased after increasing rainfall by 50% and decreasing rainfall by50%.2.The dominant phyla of soil bacterial community were Actinobacteria(37.81-66.18%),Proteobacteria(17.82-28.36%),Bacteroidetes(1.57%-13.72%),Bacillomonas(4.92-7.50%),Firmicutes(1.15%-8.18%),and Acidobacteria(1.90%-10.52%).Reducing rainfall by 50% reduced the relative abundance of Planctomycetes and Rokubacteria.The relative abundance of Proteobacteria,Bacteroidetes and Firmicutes increased and the relative abundance of Entotheonellaeota decreased due to grazing time and increase rainfall by 50%.The forbidden grazing time was the main driving force of the change of bacterial community composition,and the increase rainfall by 50% promoted the change.3.The dominant fungal phyla in the soil fungal community were Ascomycetes(61.00%-65.38%),Basidiomycetes(10.96%-12.11%),Balloomycetes(4.52-5.18%)and Zygomycetes(4.28%-4.79%).Reducing rainfall by 50% increased the relative abundance of Rozellomycota and Blastocladiomycota,while decreased the relative abundance of Zygomycota and Cercozoa.The restoration of grazing prohibition and the increase rainfall by 50% would lead to the decrease of the relative abundance of Ascomycota and increase of the relative abundance of Basidiomycota.And the effect of grazing prohibition time on the fungal community structure was more greater.4.There was a significant negative correlation between the forbidden grazing time and bacterial community abundance,fungal community diversity.The increase and decrease of rainfall had a direct and significant positive effect on the abundance of bacterial and fungal communities.Soil temperature,water content and available phosphorus content had significant positive effects on the abundance and diversity of bacterial communities.Soil temperature,water content and organic matter content had significant positive effects on the abundance and diversity of fungal communities. |
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