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sur le développement des zones arides et semi-arides

Titre : Effects of Increasing Temperature and Water on the Seed Germination and Seedling Survival in the Soil Seed Bank of Seriphidium Transiliense Desert Grassland

Auteur : 石宇堃

Grade : Master 2022

Université : Xinjiang Agricultural University

Résumé
Seriphidium transiliense desert is an important grassland type of Xinjiang desert grassland.However,it has experienced extensive degradation,because of overgrazing and human disturbance.With time goes by,grassland desertification and exposed surface area gradually expanded,so it is urgent to restore the management.Soil seed bank plays an important role in the recovery and reconstruction of degraded grassland,and its seed germination density and germination time directly affect the degree of vegetation restoration.Temperature and precipitation is the main ecological factors affecting seed germination.At present,the climate in Xinjiang is changing to"warm and wet",and it deserves attention that their interaction impect on the germination of soil seed bank seeds.Therefore,in this paper,a two-factor experimental design was adopted to study the effects of simulated temperature（control,the temperature increase of 2℃,4℃,6℃,indicated by T0,T2,T4,T6 in order）and simulated water addition（control,water increase of 5%,10%,15%,20%,indicated by W0,W1,W2,W3,W4 in order）on the species,quantity dynamics and plant diversity of seed germination plants in the soil seed bank in the 0-10 cm soil layer of Seriphidium transiliense desert grassland.The similarity between the soil seed bank and the existing seedling community and the existing vegetation community in the field plot was analyzed.It provides a basis for vegetation restoration of Seriphidium transiliense desert grassland in the future under warm and wet climate.The main results are as follows :（1）The total number of seeds germinating and the number and diversity of species in the germinable soil seed bank of Seriphidium transiliense desert grassland in the 0～10 cm soil layer showed an increasing trend with increasing precipitation and an increasing trend with increasing temperature,while the interaction of temperature and precipitation did not have a significant effect on it.The total number of germinated seeds,the number of germination of dicotyledonous plants and the number of germination of annual herbaceous plants in the seed bank of germinable soil under T2W4 treatment were the highest,with 350.29,318.45 and191.07 No·m-2in the 0～5 cm soil layer,and 159.23,159.23 and 127.38 No·m-2in the 5～10cm soil layer,respectively 159.23,127.38 No·m-2.（2）The dynamics of germination and extinction in the desert soil seed bank of Seriphidium transiliense had different responses to the temperature changes of different precipitation.The increase of precipitation had no significant effect on the dynamics of the cumulative germination number of seeds and the number of dead seedlings in the soil seed bank.The temperature was too high（T≥6℃）will lead to a decrease in plant survival rate.Under the interaction of temperature increase and water increase,the germination period of seeds will be advanced,and the plant will complete its life cycle ahead of schedule.（3）The Sorensen similarity between the germinated soil seed bank of Seriphidium transiliense desert grassland and the existing vegetation in the field increased with the increase of precipitation and decreased with the increase of temperature in the 0～10 cm soil layer.Fluctuation trend,the variation range was 0.24～0.50,0.25～0.52,0～0.15,and the similarity coefficients showed that the seed germination period was higher than the seedling survival period.（4）In summary,within the experimental design range,the increase of precipitation promoted the seed germination of soil seed bank in Seriphidium desert grassland in Seriphidium transiliense,while the increase of temperature inhibited the seed germination.Moderate warming and water increase（T≤T4,W≤W4）had no significant effect on seed germination and seedling settlement,while excessive warming and no water increase（T≥6℃,W0）was not conducive to seed germination of soil seed bank in degraded desert grassland.

Mots clés : Increasing temperature ;Seriphidium transiliense desert grassland ;Soil seed bank ;Seedling settlement ;Similarity of community ;

Présentation (CNKI)