Studies On The Population Distribution Pattern Of Poisonous Plants And Its Correlation With Plateau Pika,AM Fungi In The Tibetan Plateau Alpine Medow

The plant population distribution patterns are composed of random distribution,aggregation distribution and uniform distribution,which could not only showed the dynamic development of plant population,but also could describe the succession of vegetation community.In the degradation of grassland ecosystem,the dominant position of the grass was been threatened and replaced by the poisonous plants.Arbuscular mycorrhizal(AM)fungus is one of the most important microorganisms in soil ecosystem.In grassland,AM fungi were widely spread and had different effects on the grass and poisonous plants.The mycorrhizal symbiosis could be defined as a continuum from parasitism to mutualism.There is an undiscovered problem that whether the grass could be benefit from the mycorrhizal symbiosis and the poisonos plants could be prohibated by the mycorrhizal symbiosis in natural habitats?Based on the above,this research was carried out to studiy on the population distribution pattern of the poisonous plants and its correlation with plateau pika,AM fungi in the Tibetan Plateau alpine meadow.The study included four experiments.The first experiment is to investigate the correlation between the distributing characteristics of poisonous plants and plateau pika.The second one is to investigate the population distribution pattern and the relevance of the poisonous plants indifferent seasons in alpine meadow of the Tibetan Plateau.The third one is to explore whether the activities of plateau pika affect the response of poisonous plants on native AM fungi.The last is to explore the effects of different AM fungi on the growth of Elymus nutans,in order to select the most suitable AM fungal species and achieve the maximum benefit.The main results are as follows:1)The plant biodiversity index,the evenness index and the Margalef richness index were determined,and the correlations between distributing characteristics of poisonous plants and plateau pika were analyzed.The results indicated that the spreading of poisonous plants is significant negatively related to plateau pika(P<0.05)in the Tibetan Plateau alpine meadow.2)By using the variance/abundance methods,seven poisonous plants in growth period,blossom period and seed stage were investigated in aggregation distribution pattern.According to the Moristia index and other indexes,it was suggested that the aggregation intensity of these poisonous plants were different in growth period.In blossom period,the aggregation degree of Gentiana macrophylla.Ajuga ovalifolia,Trollius chinensis,Gentianopsis paludosa is low,and the aggregation degree of Ajuga ovalifolia,Saussurea hieracioides is high,the aggregation degree of Anaphalis lacteal increases at the same time.The relationships of G macrophylla-A.lacteal(P<0.01),T.chinensis-A.ovalifolia(P<0.01),T.chinensis-A.lacteal(P<0.01),and the relationships of S.hieracioides-L.virgaurea(P<0.05),S.hieracioides-T.chinensis(P<0.05)were all significant positive correlation(P<0.05).3)By the influence of plateau pika,the colonization rates of seven poisonous plants to indigenous AM fungi were different in different seasons.The plateau pika significantly increased the colonization rates of G.macrophylla and A.ovalifolia(P<0.01),L.virgaurea,T.chinensis,A.lactea to native AM fungi(P<0.05),but decreased the response of S.hieracioides to native AM fungi(P<0.01).There was no significant inflence of G.paludosa to native AM fungi.4)AM fungi could promoted the growth of Elymus nutans in greenhouse.AM fungi caused significantly improvements on the fresh weight and biomass,root length,plant height,tiller number and leaf number(P<0.05).Secondly,G.versiforme could significantly promote the growth of E.nutans in the different soil moistures.There were mutualistic symbiotic relationships between AM fungi and grass that formed a close relationship with AM fungi,plant species and environment factors.