Study On The Ecological Niche Of Desert Plants In The Eastern Qaidam Basin

Plant niche research is one of hotspots in the field of ecology and geography research in recent years.Ecological niche can not only show the realistic results of inter-species relationship,but also the dynamics and causes of the occurrence and development of community characteristics,inter-species competition and evolution.From the aspects of resources and environment gradient analysis of plant population niche is the important method of the research on ecological niche,it can explore different plant utilization efficiency of resources and environment,the same plant in different degree of resource utilization and the coexistence relationship between species.The Qaidam basin,located in the northeast of Qinghai-tibet plateau,has developed a remarkable desert landform under the conditions of dry inland and high cold.It is the representative of the typical desert basin in China.Desert shrub is the main advantage of plants,and the existence of the community are beneficial to the recovery and reconstruction of desert ecosystem,so accurately assess the desert plants in the region of the niche has important ecological significance.In this paper,soil and plants collected in 27 typical samples in eastern Qaidam basin were studied.By analyzing the distribution characteristics of soil factors such as soil moisture content,bulk density,organic matter,p H,total salt and total nitrogen in horizontal and vertical directions,the ecological niche characteristics of 13 dominant desert plants in 6 soil dimensions were calculated based on the Levins niche width formula and Pianka ecological niche overlap formula.The main results are as follows:(1)Spatial distribution of physical and chemical factors in soil.In the horizontal direction,the soil moisture content is significant,and the soil moisture content in the sample land east of Delingha-Dulan is significantly higher.Second,the closer to the central basin,the lower the soil moisture content is;The soil bulk density change is small,the data distribution is concentrated,and the soil bulk density is high in the central part of the basin,reflecting the poor soil structure and poor soil quality;The organic matter content of the samples in the east of dulan was significantly higher than that in other samples in the basin,and the organic matter content in the center of the basin was less and the differences between the typical samples were not obvious;The soil in the basin is seriously alkaline,and in the horizontal direction,the p H fluctuation is slow,and the variation degree is the smallest among the six physicochemical factors(6%);The total nitrogen content of soil was low and the variation was high.It is similar to soil moisture content in horizontal distribution,but its change is more prominent.In addition to the high nitrogen content of meadow soil in the natural state,the abandoned cultivated land also showed a high nitrogen content,indicating that the transformation of the land which was offered by human was far-reaching;Soil full salt: its overall content is high,and it is significantly changed in the horizontal direction.The soil which has high salt content is mostly seen in the basin,the alluvial plain and the margin of the flood fan in the basin,and the most prominent in the vicinity of the gahai lake.In the vertical direction,the soil moisture content shows that the subsurface content is slightly higher than the other two layers,but the difference is not significant.The vertical variation varies with the surface community,and the vertical fluctuation of soil moisture content in meadow area is greater than that of desert plants.Soil bulk density shows a tendency to increase slowly with the deepening of soil depth,which is more intense in relatively moist meadow.From the soil profile,the soil bulk density of each layer is almost uniformly distributed,and the proportion of each layer is about33%.The vertical distribution of soil organic matter content is obvious,and the soil organic matter content in most samples decreases with the deepening of soil laye.This rule is more significant in the environment with relatively moist samples,and the difference between soil layers is significant.The soil p H value is small and the vertical distribution is more uniform.In the vertical direction,the expression of totalnitrogen of soil is more complex,in which the vertical direction of the better sample in the habitat is shown as the regularity of decreasing gradually with the increase of soil depth.(2)Ecological niche characteristics of desert plants13 kinds of desert plants in 6 soil factors on the average niche breadth from big to small in turn is: Ceratoides latens,Reaumuria songonica,Achnatherum splendens,Phragmites communis,Sympegma regelii,Salsola abrotanoides,Nitraria tangutorum,Kalidium foliatum,Kobresia Willd,Ephedra sinica,Calligogum kozlovi,Haloxylon ammodendron,Tamarix ramosissima,Among them,in the soil moisture content,bulk density and organic matter,the Ceratoides latens of chenopod occupy the largest ecological niche width.In soil p H,total salt,and total nitrogen,the Reaumuria songonica has the widest niche breadth.Secondly,the species with large niche width do not occupy the highest overlap value in the niche overlap,but are in a middle position.The position of Ceratoides latens and Reaumuria songonica in ecological niche breadth and niche overlap is relatively high,which plays an important role in community construction.Seventy-eight species have an ecological niche overlap value on each soil factor < 0.3,the proportion of the total logarithm is 76%.This indicates that the overall ecological niche of the plant in the eastern part of Qaidam basin is low,the competition is small,and the community is in a relatively stable state.