高寒山区一年生混播牧草生态位对密度的响应

Abstract

Niche refers to the space-time position of a population occupied and the functional relationship between it and related population.Niche including the requirements of the species on the environment and the influence of environment on species,it reflects the interaction between species and habitats quantitatively.Density-dependent is one of the important selecting pressure in nature,which makes the ground light competition between the neighborhood.by changing the number of populations within each plant availability of resources.Therefore,niche and density gradient are inseparable.To analyze the dynamic distribution rules of niche of mixed pasture from the density gradient is a significant approach to study the strategy of plant population ecological adaptation.Study sites are located in the HuangCheng town(37°58'26″ N,101°47' 34″ E) which belongs to an upper reaches ShiYang River,SuNan county of alpine region(2530 m) lying in the north of Qilian Mountains.In replacement series experiments,the two species of planting densities were varied but the total density was held constantly.It was used to build mixed-seeding meadow of Avena sativa L.and Vicia vilosa Roth in June 15,2010.This study set up seven grass-legume seeding ratios: KY(1∶0),A(8∶2),B(6∶4),C(5∶5),D(4∶6),E(2∶8),KM(0 ∶1) which maintains about 300 plants total density constantly.There are total of 21 plots(2 m × 5 m) adopted randomized block arrangement with three replications.We recorded the phonological period,plant-height and branch(tiller) number of mixed grasses every 10 days started from July 17,2010 to August 27,2010.The sampling area is 50 cm × 50 cm in every plot,the mixed grasses were separately placed into an oven at 65 ℃ for 8 hours according to the block order until it reached the constant weight,thus the biomass were recorded respectively.Niche breadth is the metric of plants scale on environment and natural resource utilization,niche overlap occurs when two or more species to take possession of or make use of a certain kind of resources(space,nutrient content,food,etc) together.Under density dependant,the niche breadth of Avena sativa L and Vicia vilosa Roth and the niche overlap of the two species transfer occurred to some extent during the growing period of grasses.The results showed that:(1) With the growth of forage,the density of Avena sativa L niche breadth decreases gradually and Vicia vilosa Roth showed a gradually increasing tendency in all group of mixed grassland,niche overlap of Vicia vilosa Roth and Avena sativa L.showed a reducing tendency.(2) In mixed grassland with Avena sativa L relative density decreases and the relative density increase of Vicia vilosa Roth..Avena sativa L niche breadth decreases gradually and Vicia vilosa Roth showed a gradually increasing tendency,the niche overlap of Avena sativa L and Vicia vilosa Roth increases gradually.To sum up,in the course of grass growth,density dependence lead the resource allocation strategies of the two mixed pasture response to intraspecific,interspecific competition adjusted.Mixed pasture competition ability' s change led to its niche in a certain degree of metastasis and differentiation,which made the relationship between species and community structure tend to be stable.To form a mutual stability and mutual influence ecological system,achieve maximum resource utilization.