Responses Of Seed Rain, Seed Bank And Seedling Regeneration To Simulated Warming And Nitrogen Application In Leymus Chinensis Community

Globe warming and Nitrogen addition are the hot issues in the realm of global change, and as one of the main types of the ecological system of the land, the grassland has an important role in the response and regulation to the globe warming .The propagule bank of the vegetation is forced to change in these ecological incidents, as well as the key driving factor to impact and change the succession of vegetation. Therefore, the research on the the mechanism of the response of the propagule bank to globe change is the key step to reveal the response of grassland to globe change and also of significance to explain and predict the interaction of grassland ecosystem with globe change and the theory of vegetation regeneration.This thesis focuses on Leymus chinenisis(Trin.)Tzvel. Grassland in Songnen plain.We simulated warming by achieving with Infrared Radiator and nitrogen (N) application by receiving ammonium nitrate in vivo. We examined seed rain, seed bank and seedling regeneration responses to manipulations of four treatments: ambient, warming, N application, and warming plus N application during the year 2008 and the year 2009. The result showed that:Under warming treatment, for the herbaceous plant functional group, the quantity of seed rain and seed bank was decreased, the ratio of the number of seedling that from clonal growth with sexual growth was decreased; for the weed plant functional group, the quantity of seed rain and seed bank was accelerated, the ratio of the number of seedling that from clonal growth with sexual growth was accelerated; for the whole vegetation, the quantity of seed rain and seed bank was accelerated, the ratio of the number of seedling that from clonal growth with sexual growth was accelerated, the richness of plant species and the simpson parameter was decreased, the density of the vegetation was decreased, the variation of the coefficient of similarity among standing vegetation, seed rain, seed bank and seedling regenerating from seed was not inerratic when compared with the control treatment.Under N application, for the herbaceous plant functional group, the quantity of the seed rain and seed rain was a little changed, the quantity of seed bank was decreased, the ratio of the number of seedling that from clonal growth with sexual growth was accelerated; for the weed plant functional group, the quantity of the seed rain and the seed bank was accelerated, the ratio of the number of seedling that from clonal growth with sexual growth was decreased; for the whole vegetation, the quantity of the seed rain and seed bank was accelerated, the ratio of the number of seedling that from clonal growth with sexual growth was accelerated, the richness of the plant species was almost not changed, the simpson parameter was decreased, the density of the vegetation was changed a little, the vaule of the coefficient of similarity among standing vegetation, seed rain, seed bank and seedling regenerating from seed was accelerated when compared with the control treatment.Under warming plus N application, for the herbaceous plant functional group, the quantity of seed rain was almost not changed, the quantity of the seed bank was accelerated, the ratio of the number of seedling that from clonal growth with sexual growth was accelerated; for the weed plant functional group, the quantity of the seed rain and seed bank was accelerated separately, the ratio of the number of seedling that from clonal growth with sexual growth was decreased; for the whole vegetation, the quantity of the seed rain was accelerated, the quanlity of seed bank was almost not changed, the richness of the plant species was decreased, the simpson parameter was decreased significantly, the density of the vegetation was accelerated, the vaule of the coefficient of similarity among standing vegetation, seed rain, seed bank and seedling regenerating from seed was decreased when compared with the control treatment.The change mode of the ratio of the number of seedling that from clonal growth with sexual growth for gramineae and the weed is opposite under different treatment, and the response of the ratio of the number of seedling that from clonal growth with sexual growth for the vegetation is more dependent on the response of the seed.