The Role And Mechanism Of Plant Bud Bank And Gap Disturbance In Grassland Vegetation Restoration

Plants maintain community structure through regeneration dynamics, which consists of the seed and bud banks. This study focus on the bud bank and the mechanism of gap disturbance of seedling establishment by reseeding. We conducted a series of field work and lab analysis to explore the role of bud bank and gap disturbance in the grassland restoration, from the perspective of seed and bud banks.Firstly, mechanism of gap disturbance on seedling establishment by reseeding Stipa krylovii and Agropyron cristatum was evaluated. Stipa and wheatgrass were sowed monocultured separately. Factors:1) gap size (0,10cm,20cm,40cm in diameter),2)gap type, including shoot gap and root gap. Our results show:l) gap disturbance increased the rate of successful seedling establishment of stipa and wheatgrasss,2) the samller of gap size,the higher of soil moisture, root gap have the higher soil moisture than that of shoot gap,3) gap disturbance increased the growth performance of both species(biomass, leaves per plant, tillers per plant), and root gap have the better performance than that of shoot gap,4)with the increase of gap size, the survival rate of wheat grass decreased, in contrast, survival rate of stipa will increased, both of that significantly higher than control,5) the risk of herbivory of wheat grass will increased with the gap size increase, and no affects with stipa.Secondly,, an field experiment was set to evaluate the response mechanism of renegation from seed bank to the gap disturbance. Factors:1) gap size (10cm,20cm,40cm in diameter),2) gap type, including shoot gap and root gap,3)existing time of gap (1year,2year,3year). There are8replicates with each treatment plot. Also plant survey data were used to analysis. Results shows:1) existing time of gap increased the number of colonizaiton species in gap significantly, however,the species number will stay stable when it reach the roof, about5,2) colonized species in gap have very significantly similarity with neighbour plants,3) with the increase of the gap size, colonized speices in gap and tillers increased,4) root gap have significantly positive effects on regenation of plant, the number of colonized species in root gap was significantly higher than that of light gap,5) gap creation provide the opportunity of regenation for rare species.Thirdly, a field survey experiment was conducted to characterize the bud bank density of total and different functional groups under different stage of successional grassland communities. There were6sites chosen as replicates, then divide them into two groups by stage of succession. One is mixed prairie which was dominate by perennial casepitose grass, the other is introduced prairie which was dominate by perennial rhizomatous grass. Our results show:1) bud bank density(n/m2) of same precipitation area but alter from different succession stage of grassland community is not significant, total bud bank density of community has no consequent relationship with composition of plant species, and there is no effect of land use and management history on total bud bank density;2) long-term grazing and hay may change the structure of functional groups of total bud bank, and increase the risk of invasion of introduce grass;3) bud bank of casepitose grassland community was dominated by crown bud, in contrast, bud bank of rhizomatous grassland community was dominated by rhizome bud, bud bank density of forb was far smaller than that of gramineae. Forthly, an experiment was conducted to evaluate the persistence of smooth brome in response to different management strategies in terms of bud bank density and viability. Treatment:control(CK),fire(F), fire+mowing(FMl), and fire+mowing twice (FM2). Our results shows:1) fire and mowing(mimic hay) treatment have negative effects on the bud bank density of soomth brome significantly in the first grwoing season, it decrease the bud numbers per plant and outgrowths significantly,2) bud bank of smooth brome have the potential to regrowth into the above ground tillers, and persist to fire and mowing treatment; there is an regeneraton dynamic between bud bank and tillers,3) fire and mowing treatment trigger and change the mechanism of bud viability-dormancy, which will increase the number of active bud and ratio of active bud, to recapture the above ground tiller density,4)fire and mowing treatment increased density of above ground tillers of smooth brome.In conclusion, this study found that the bud bank is very important for the maintance of structure of grassland community, plants or plant population can regulate the viability-dormancy mechanism of bud bank to regenation itself or restore from a disturbance. Gap distubance creates the suitable microsite for seedling regenation from seed or bud, different species differ in their response strategies to coping with the gap disturbance...