Spatial Pattern And The Influence Factors Of Aquatic Plant Diversity In The Northwest Arid Areas

Geographic patterns of species diversity and their underlying mechanisms have long been the focus of macro-ecology and biogeography.Although the need to understand large-scale pattern is well recognized,most studies in this field of research concern terrestrial vertebrtates and higher plants and marine realms,whereas aquatic macrophytes has far received considerly less attention.In this study,the aquatic plants diversity in arid areas in Northwest China as the research object,the species and community diversity were studied using field investigation method on the arid zone from July to October in 2015 and 2016,the main survey contents are the 516 sample points of aquatic plant community composition,distribution,biomass and other aspects of macrophytes.This paper Studies the regional level of aquatic plant richness,vertical distribution pattern change rule;Aquatic plant richness spatial pattern formation mechanism and verify the diversity pattern of main hypothesis in the Northwest arid areas;Aquatic plants ?-diversity of spatial differentiation;Aquatic plant diversity of b-spatial pattern of influencing factors.The main research results are as follows:1)There were 134 species collected belonged to 32 families,52 genera accorss the northernwest China.Among them,3 familes,4 genera and 5 species belong to free-floating plant,4 familes,5 genera and 5species belong to floating plant,8 familes,9 genera and 39 species belong toemergent plant,and 17 familes,35 genera and 85 species belong to submerged plant.The aquatic plants 94.11% of families,81.25% of genera,and 59.82% of species were collected in the Northwest arid areas.2)Aquatic plants the horizontal and vertical distribution pattern has certain regularity in the Northwest arid areas,in the study areathe richness showed a hump-shaped pattern along latitudinal,longitudinal,and altitudinal gradient.Namely,the Northwest arid areas in central and elevation of the middle area(1000-1500m)has the highest ?-diversity in the northwest arid areas,there's an obvious peak.3)This paper explore aquatic plant species richness spatial pattern in the Northwest arid areas and test several hypotheses concerning geographic diversity patterns.Multivariate regression and variation partitioning analyses were used to examine the relative effect of area,climate and geometric constraints on spatial richness patterns,and also the differences among life community.The geometric constraint,water-energy dynamics and species-area relationship explained 97.7% of total variance,Independent explanation 27.3%,5.4% and 2.7%,respectively,joint explained the species richness pattern of 89.3%,63.1% and 44.6%.The geometric constraints were most important in explaining the species diversity patterns within the study region.And Area and water-energy showed a weak but essential role in explaining the species diversity patterns.4)Research results show the Species turnover in latitudinal direction zones increased,the species replacement rate increased and then decreased from south to north,the Species turnover and replacement rate is relatively stable within the scope of the latitude 37.5~50°N.While other latitude range of the Species turnover increases with the distance between the sample decreases,the species replacement rate is just the opposite.The Species turnover was stronger in the longitudinal direction of the studied region,the species replacement rate declined obviously,the species turnover and replacement rate relative to other area is the most stable within the scope of longitude 81~87°E.5)Variation partitioning analyses were used to climate,altitude,water quality and space variables for the contribution rate of ?-diversity,explain the northwest arid areas of aquatic plants ?-diversity change mechanism.Our results showed that climate variations were stronger and water quality and PCNM variations relative weaker role in explaining the species ?-diversity patterns within the study region.But the joint effects of each variation were high in explaining the species ?-diversity patterns.Beside climate,latitude,water quality and PCNM variations,other environmental factors have essential role in the species ?-diversity patterns in the northwest China.