Effects Of Warming On Seed Germination And Seedling Settlement In Soil Seed Bank Of Sagebrush Desert Grassland

Sagebrush desert grassland is an important part of grassland animal husbandry in xinjiang.However,a large area of Seriphidium transiliense desert grassland was degraded due to unreasonable utilization,It has seriously restricted the development of grassland ecology and production function,so it is urgent to restore the management.Soil seed bank plays an important role in the restoration and reconstruction of degraded ecosystem,and its seed germination quantity and germination ability directly affect the degree of vegetation restoration.Temperature is one of the main factors affecting seed germination,while the climate in Xinjiang is warming,and its impact on the germination of soil seed bank seeds is worthy of attention.Therefore,in this paper,the ten-day average temperature of 23a urumqi city was taken as a control,and the artificial climate box method was used to simulate differernt temperature increase[in the first year:control(CK),increased by 2℃(T2),increased by 4℃(T4),increased by 6℃(T6),the second year:decreased by2℃(T-2),control(CK),increased by 2℃(T2),increased by 4℃(T4)]to moderated degradation S.transiliense desert grassland the influence of seed germination types in the soil,quantity and dynamic,the germination seedling settled community characteristics and plant diversity.The similarity between soil germinable seed bank,existing seedling community and existing vegetation community in the field was analyzed by using community similarity coefficient.It provides a reference for vegetation restoration and succession of degraded sagebrush desert grassland under future climate warming.The main results are as follows:(1)The number of germinated species in the soil seed bank and the similarity between the number of germinated species and the aboveground vegetation in the S.transiliense desert grassland in the soil layer of 0-10 cm under the moderate warming treatment(CK-T4,T-2-T4)did not change significantly,Compared with the CK,the number of germinated species and their similarity coefficient with aboveground vegetation decreased by 57%(33%)and 41%(29%)respectively when the temperature increase reached T6.With the increase of temperature,the total seed germination density,the number of perennial herbs and dicotyledon plants in the germinable soil seed bank of S.transiliense desert grassland of 0-5 cm and 5-10 cm soil layer decreased.The germination number of annual herbs varied in different years,but moderate warming can promote the germination of annual herbs.Subshrubs and monocotyledons were not sensitive to the effect of warming.(2)Excessive warming is not conducive to the settlement and survival of germinable soil seed bank seedlings in S.transiliense desert grassland.The height,coverage,density and biomass of the settlement community of seedlings from 0-5(5-10)cm soil layer increased first and then decreased with the increase of temperature,all of which reached the highest level in T4,Compared with the control,when the temperature increase reached T4,the each indexes increase by 242%(51%),346%(13%),53%(75%),446%(30%)in turn,and T6 was the lowest,all of which were 0.There were differences in response to temperature increase in the number of resident seedlings,in the range of CK～T4,increasing temperature promoted the increase of Chenopodium glaucum height,coverage,density and biomass,but all indexes did not reach a significant level,However,its height and density decreased significantly when the temperature increased to T6,The effect of increasing temperature on Atriplex patens,Allium chrysanthum,Eremopyrum triticeum,Amaranthus retroflexus and Trigonella ammophilus was not significant.Moderate temperature increase did not affect the similarity coefficient between the seedling settled community and aboveground vegetation,but the similarity coefficient is 0 when the temperature is excessively increased.(3)The shannon-wiener index of germinable soil seed bank and existing seedling community in S.transiliense desert grassland was 0-1.3,0-0.2,the Pielou index was 0-0.9,0-0.3,and the Patrick index was 0-4.6,0-1.4.and all indexes showed a downward trend with the increase of temperature.The 0-5 cm soil layer decreased obviously compared with the 5-10 cm soil layer.(4)In conclusion,the increase of temperature inhibited the germination of seeds in the soil seed bank of S.transiliense desert grassland,Moderate increase in temperature had little effect on germination species number,seedling survival number and similarity with aboveground vegetation,while excessive increase in temperature was not conducive to seedling survival,reduced germination species number and similarity with overland vegetation,and may not conducive to the restoration of degraded sagebrush desert grassland.