The Impacts Of Shading, Fertilization And Cutting On Growth Of Three Grasses In Qinghai-Tibet Plateau

A study was conducted with Elymus nutans,Festuca ovina,Poa crymophila—three common grasses with different nutrition niche in community in eastern region of Qinghai-Tibet,to assess the effects of shading,fertilization,cutting on their growth responses.It will provide theoretical evidence for management of grassland by discovering the life history strategies of plant adapted to such a special environment in Qinghai-Tibet plateau.The conclusions are summarized as follow:1.All three grasses had biomass compensatory continuum,tolerance strategies to damage can be improved.The best compensatory growth of Festuca ovina and Poa crymophila were for unfertilized plants in 43.5%light,while Elymus nutans was for unfertilized in 6.74%light.For Festuca ovina,the fertilized clipped plants had better compensation than the unfertilized plants,but a reverse perform for Elymus nutans and Poa crymophila.The earlier clipped plants had better compensation for Elymus nutans and Festuca ovina,but a reverse perform for Poa crymophila.Under the same light and fertilization conditions,it would be the best compensatory growth,when three-cutting frequency for Elymus nutans,two-cutting frequency for Poa crymophila and one-cutting frequency for Festuca ovina.Elymus nutans is more suitable to be disturbance for many times than the others.Mild cutting is good for Festuca ovina and Poa crymophila,while severe cutting is good for Elymus nutans.2.The relative growth rate for all these three grasses was higher in the open than in 6.74%light.The fertilization addition decreased the relative growth rate for all these three clipped grasses.For Elymus nutans and Festuca ovina,the earlier clipped plants had higher relative growth rate compared to the later clipped plants,but a reverse perform for Poa crymophila.For Festuca ovina and Poa crymophila,mild clipped plants had higher relative growth rate compared to the heavy clipped plants.Cutting intensity had no effect on the relative growth rate for Elymus nutans.For Festuca ovina,the plants with three- cutting frequency had the highest relative growth rate compared to other frequency,where there was no insignificant effect for Elymus nutans and Poa crymophila.3.As far as the model of plant response to cutting,C-S-R is suitable for those species which had the similar habit and similar ability against the disturbance,MAF model is usually suitable for those species with same timing of herbivory.The growth response of all these species to cutting supported the minimum resource requirement theory.The plants with the highest relative growth rate had the best compensation for Poa crymophila.4.With the grown of these grasses,both below-ground and above-ground biomass increased.For the growth of all the studied species,program,when light was limited, Elymus nutans and Festuca ovina would be invested more biomass to the below-ground than above-ground,but a reverse for the Poa crymophila.For Elymus nutans and Festuca ovina,the plants tended to allocate more biomass to below-ground than to above-ground as for the limited fertilization.Elymus nutans and Festuca ovina would be invested more biomass to below-ground than above-ground for cutting treatment.Under light and fertility interactions,for Elymus nutans and Poa crymophila,the plants allocated more biomass to above-ground compared to below-ground,but a reverse perform for Festuca ovina.At the multi-effect of all factors,Elymus nutans would be allocated more biomass to above-ground.This is likely to be a consequence of reallocation of resources into the above-ground at expense of root growth for Elymus nutans.For Festuca ovina and Poa crymophila,there was no trade-off relationship between the increased above-ground biomass and below-ground biomass.5.In non-artificial clipped conditions,the largest above-ground biomass of Elymus nutans were for fertilized plants at 43.5%light,while Festuca ovina was for unfertilized plants in the open.For Poa crymophila,there was for fertilized plants in the open.6.Under conditions of unfertilized,6.74%light,earlier initial time for cutting,serious and three times cutting,Elymus nutans has the highest compensation with 5.613 compensation index.The increased aboveground biomass are at expense to the belowground biomass,by increasing the more leaf numbers and thicker leaf.At fertilized plots,43.5%light conditions,when was earlier,mildly and once cut,Festuca ovina has the best compensation with 1.680 compensation index;Under unfertilized plot,43.5%light conditions,when Poa crymophila was later,mildly and twice cut,the compensation is the best and compensation index is 5.980.7.For Elymus nutans,fertilized plot,43.5%light intensity,later-mild-once cutting treatment resulted in made the highest aboveground biomass with 1.464 compensation index,and it is 6.500g;For Festuca ovina,when at natural light,fertilized plot, earlier-mild-once cutting lead to the best desirable growth with 1.163 compensation index, while the aboveground biomass is 0.752g.For Poa crymophila,when fertilized,at natural light,it has the best growth after later-mild-twice cutting,the aboveground biomass is up to 2.391 g,and the corresponding compensation index is 1.546.