Study On Species Composition And Population Distribution Pattern Of Potaninia Mongolica Desert In Eastern Alashan

Potaninia mongolica belongs to the genus Potaninia in the Rosaceae family.It is a remnant species of ancient monospecific genus.Due to the special reproduction method of P.mongolica,interspecific competition and habitat fragmentation,the population has been decreasing,which belongs to a national secondary key protected plant in China.In this paper,we analyzed the community characteristics and diversity,interspecific associations,and population distribution patterns of P.mongolica in the eastern Alashan Desert to provide an effective scientific basis for the rational conservation of P.mongolica.Results of the study include:1.A total of 48 species belonging to 14 families and 38 genera were obtained from the surveyed 14 P.mongolica community.Among them,Gramineae and Chenopodiaceae were dominant,both accounting for 20.83 % of the total number of species.The P.mongolica community had shrubs and semi-shrubs as the basic life form,each accounting for20.83% of the total number of species,and herbaceous plants were relatively abundant,with 33.33% of annual herbs and 25% of perennial herbs.The water ecological type is absolutely dominated by arid life,with 79.19%,of which typical arid life and super(strong)arid life account for 39.58% and 35.42% respectively.There are 14 geographical components of the zone system,with Gobi component and Gobi-Mongolian component dominating,accounting for 22.92% and18.75% of the total number of species,respectively.2.There were three association group of P.mongolica deserts investigated: P.mongolica typical desert,P.mongolica-grass desert and P.mongolica-broadleaved herb desert,which were further divided into 14 associations.α-diversity index analysis showed that there were some variability in community diversity among the association,with P.mongolica-Cleistogenes songorica+Peganum nigellastrum having the highest among all association,followed by P.mongolica+Sarcozygium xanthoxylon-Stipa breviflora and P.mongolica-Stipa glareosa.The lowest association diversity was P.mongolica-Pennisetum flaccidum,whose dominant species role was obvious,low uniformity and lowest Shannon-Wiener diversity index.β diversity analysis showed the highest Cs value(0.923)and the highest similarity coefficient between the P.mongolica-Allium mongolicum and P.mongolica+S.xanthoxylon-S.breviflora,and the lowest β diversity among the communities.The smallest Cs value(0.207),the lowest similarity coefficient and the greatest β-diversity among the communities were found among P.mongolica+Reaumuria soongarica-Allium polyrrhizum and P.mongolica-P.flaccidum,P.mongolica-S.glareosa and P.mongolica-P.flaccidum,P.mongolica+Tetraena mongolica+R.soongarica and P.mongolica-P.nigellastrum.3.The interspecific relationships among species in the eastern Alashan desert P.mongolica community were mainly negative,but the species pairs showing significant(P<0.05)positive associations were higher than those showing significant negative associations.Among the three tests,the χ~2 test and Spearman’s rank correlation test were generally consistent,with significance rates of 21.4% and 21.3%,respectively,while the Pearson correlation test had a significance rate of only 9%.The significance rates of all three tests were low,indicating that the sheep spurge community in the study area as a whole was loosely interspecies related.For the established species of P.mongolica,the positive correlations were found in Oxytropis aciphylla,Ajania achilleoides and Krascheninnikovia ceratoides,and the negative correlations were found in A.scoparia and S.xanthoxylon,among which O.aciphylla and A.scoparia were consistent in both methods.4.The Alxa population of P.mongolica was dominated by class II plants,accounting for 69%,whereas class I plants accounting for only5% of the total population.However,the Alxa population was observed to be stable because of asexual reproduction.On the other hand,for the Erdos population,the proportion of class II and class III plants were similar,and no class I plants were observed,which resulted in limited population renewal by seed propagation.The Alxa population was randomly distributed,with class I and II plants predominantly distributed in clusters at small and medium scales and randomly distributed at large scales.Nevertheless,the Erdos population was predominantly distributed in clusters,both in general and at all size scales,which was strongly related to interspecific competition.There was a significant negative correlation between class III and I individuals of the Alxa population at small and medium scales,reflecting the inhibition effect of the senior individuals on the young individuals.However,class II and III plants of the Erdos population showed a positive association with increasing scale range,suggesting a positive interaction between mature age classes of P.mongolica.