Effects Of Precipitation Changes On Seed Germination And Community Diversity Of Desert Plants In Junggar Desert

Arid area is the largest terrestrial ecosystem with scarcity of water as the key limiting factor.With intensification global climate change,the precipitation change has an important impact on arid areas.The precipitation change may affect seed germination,even directly related to the successful establishment of seedlings.It will eventually have a dramatic impact on the population.At present,most researches have been focusing on the characteristics of seed germination in laboratory experiments.However,the research on how germination characteristics impact population persistence and community diversity in field habitat is rare.Therefore,under intensification precipitation change,through investigation the demographic characteristics and special germination characteristics of four annual species of Salsola L(Salsola affinis,Salsola korshinskyi,Salsola nitraria,Salsola brachiata)in Junggar Desert,and 8 dominant species(Haloxylon ammodendron?Haloxylon persicum?Seriphidium terraealbae?Calligonum leucocladum?Salsola affinis?Schismus arabicus?Tetracme recurvata?Corispermum lehmannianum)with a high frequency of distribution and high value were selected as the research object.We used split plot experiment for changing snowfall and rainfall supply,the effects of snowfall,rainfall and their interaction on seed germination and plant growth are analyzed.The regression analysis of plant diversity with precipitation,snowfall and March-June rainfall in the Gurbantunggut Desert fro m 2009 to 2018 was also carried out.The relationship between seed germination characteristics and population persistence,the effects of precipitation on seed germination characteristics,plant growth,physiological characteristics was summarized.The main results are as follows:(1)The number of individuals of all populations changed drastically in a single year.Approximately 41.6%-100%of seedlings germinated in spring were dead.Germination heterochrony in Salsola L.was a more efficient way for the continuation and growth of population.Fruit heteromorphism bore no direct relationship to germination heterochrony.Germination heterochrony was caused by precipitation characteristics and short seed longevity of Salsola L.annuals,which was an effective survival strategy for plant to adapt to changing environments in arid area.(2)Snowfall and rainfall changes can affect the seed germination,seedling survival,initial germination time,germination duration and time to 50%germination percentage of the eight tested species.But,different life forms have different responses to precipitation changes.The germination percentage of perennial herb and ephemeral plants were significantly affected by snowfall,but germination percentage of shrub plants were significantly affected by snowfall,rainfall and their interaction.Survival rate of ephemeral plants were only significantly affected by snowfall,rainfall.However,survival rate of Arbors and perennial herb were extremely significantly affected by snowfall,rainfall and their interaction,and annual plants were only significantly affected by rainfall.(3)The response of seed germination percentage and seedling survival rate to snowfall and rainfall changes is interspecies difference.The germination percentage of Seriphidium terraealbae and Schismus arabicus were extremely significantly affected by snowfall,but Calligonum leucocladum and Tetracme recurvata were extremely significantly affected by snowfall,rainfall and their interaction.On the survival rate of seedlings,Haloxylon ammodendron and Tetracme recurvata were significantly affected by snowfall,Haloxylon persicum,Seriphidium terraealbae and Corispermum lehmannianum were extremely significantly by snowfall,rainfall and their interaction.But Salsola affinis and Schismus arabicus were extremely significantly by rainfall.(4)Snowfall and rainfall changes can affect the plant height,root length,total biomass,and root-shoot ratio of the eight tested species during the seedling stage,vegetative stage,and reproductive stage.However,there were some differences between species.The morphological characteristics of Seriphidium terraealbae,Calligonum leucocladum and Tetracme recurvata were significant differences under snowfall and rainfall changes,but other five species are not.Moreover,the snowfall and rainfall changes also can affect reproductive output and reproductive allocation,but there have interspecies difference.The reproductive output of the Salsola affinis,Schismus arabicus,Tetracme recurvata and Corispermum lehmannianum were significantly affected by snowfall and rainfall.However,the reproductive allocation of the Salsola affinis,Schismus arabicus and the Tetracme recurvata were generally low under all treatments,less than 20%.With the increase of rainfall,reproductive allocation of Salsola affinis and Tetracme recurvata were decreased,and with the increase of snowfall,the Tetracme recurvata and Corispermum lehmannianum shows the pattern of increasing first and then decreasing.(5)With the increase of snowfall and rainfall,proline,soluble sugar,relative conductivity and malondialdehyde of plant will decrease significantly in seedling and vegetative stage.(6)Mean annual precipitation,the C_v of mean monthly precipitation,mean annual snowfall,and mean annual rainfall in desert exhibited an increasing trend from 1988 to 2018.Species richness was positively correlated with March-June rainfall.The species abundance was positively correlated with mean annual precipitation and March-June rainfall.There was a significant positive correlation between Gleason index and mean annual precipitation,mean annual snowfall and March-June rainfall.(7)Mean annual precipitation did not significantly affect the coverage of different plant life-forms,but the species abundance of perennial plants,shrubs and arbor plants and the species richness of ephemeral plants were significantly affected by mean annual precipitation.Mean annual snowfall also did not significantly affect the coverage of different plant life-forms,but the species abundance of perennial plants and arbor plants,and the species richness of perennial plants of ephemeral plants were significantly affected by mean annual snowfall.The coverage of arbor plants and ephemeral plants,the species abundance and species richness of perennial plants and ephemeral plants March-June rainfall.(8)We analyzed the relationship between species abundance of tested species and mean annual precipitation,mean annual snowfall and March-June rainfall using regression analysis.The results show that only Haloxylon persicum,Seriphidium terraealbae,Schismus arabicus and Corispermum lehmannianum in actual community were consistent with the results of field experiment.The response of other four species to snowfall and rainfall was not consistent with the actual community.This indicates that seed germination and seedling establishment can only predict community diversity to a certain extent.