The Influence Of Degradation And Fencing On Soil Seed Bank And Their Relationship With The Above Vegetation In Alpine Grassland

Soil seed bank can provide community propagules, it plays an important role in the ecosystem.In order to explored the characteristics of different types of soil seed banks in different seasons, we analyzed"heitutan",natural grassland and degraded artificial grassland in April,August and December.For different altitudes and interferences by human, investigation and germination in geen house were applied to study the communities and the soil seed banks of Nyainqentanglha in dangxiong.It aims to provide a references for alpine grassland management and use.The results of this study were:1)The characteristics of the soil seed banks in the Three Rivers area:①The range of soil seed bank density in the Three Rivers area:2173.381-9452.362 viable seeds m-2, showed:"heitutan"> degraded artificial grassland> natural grassland.seeds in soil were remained about 64%-75%in August, were 2386.351-6973.386 viable seeds m"2.②There were obviously significant vertical distribution in soil, most species and seeds distributed in the topsoil. The upper layer of soil were suitable for seed germination, particularly in degraded artificial grassland. Compared to the updating of natural grassland, the way of "heitutan" and degraded artificial grassland were closer.The same species might not choose germination in the different grasslands. Contribution of soil seed bank for updating were affected by the above environment. Different strategies might be used by same species in different habitats.③Similarity of soil seed bank and aboveground vegetation in different grasslands and months were low (<0.33). Natural grassland contain gramineae, sedges, forbs. Besedes gramineae, the seed banks of "heitutan" and degraded artificial grassland were made of Kunlun Artemisia, Polygonwn and Cardamine, Which gramineae appeared more in degraded artificial grassland and sedges only appeared in natural sedge grassland seed bank.④Significant correlations was found between K and the number and species of seeds in April.2)The changes of the soil seed bank in the Three Rivers area between different months:①The changes of soil seed banks from April to August to December,no significant differents in natural grassland;decreased and then increased in "heitutan";significantly reduced in degraded artificial grassland.②Come to the number of species in the soil seed bank, April> December> August; diversity in heitutan:April> December> August, diversity in natural grassland:April> August December, diversity in degraded artificial grassland:December> April> August; the similarity of the ground vegetation, the lowest in August.3) The characteristics of the soil seed banks and vegetations of different altitudes in Nyainqentanglha southern slope:①When the altitudes rising,the changes of diversity of plant community unimodal distribution pattern in the southern slope of Nyainqentanglha, meaning the index of Shannon-Wiener,Simpson,Pielou,and species richness were increased and then decreased with the altitudes rising. And the relationship between the altitudinal and the index of Shannon-Wiener,Simpson,Pielou, species richness would be well explained by unimodal function. It was significant correlation between altitude and Shannon-Wiener index,and extrmely significant correlation between Simpson dominant index and coverage,but no significant correlation about the index of Pielou.②The soil seed bank in August in the southern slope of Nyainqentanglha,were 0-1245.05 viable seeds m-2,and also had obvious vertical distribution. Similarity between soil seed bank and aboveground vegetation was very low (Cs<0.2),and the maximum appeared in the middle elevations. With the altitude lowing, seed density and number of species in soil seed banks were found increased and then decreased. Maximum seed density appeared in the altitude of 4966m outside the fence, and in the altitude of 4809m inside the fence.4) The effects of fencing in different altitudes in Nyainqentanglha southern slope:①Fencing significantly improved the coverage at different altitudes of the southern slope of Nyainqentanglha, and the relative frequency of Kobresia (p<0.05).②The distribution of persistent soil seed bank of altitude showed unimodal distribution pattern,and changed after fencing.