退化草地阿尔泰针茅生殖株丛与非生殖株丛的空间格局

Abstract

Spatial pattern is important in plant ecology as it affected the dynamics of plant populations,communities and ecosystem processes,which can reveal the dynamic and stability of population and community structure.Stipa krylovii,the zonal vegetation in alpine degraded grassland,has a great significance for understanding reproductive strategies of grassland resources with studies on spatial pattern of sexual plants and vegetative plants of S.krylovii population.In this study for two main aims: First,to describe the scale transformation of spatial pattern along with the different plot;Second,to analyze the effect of aboveground biomass and plant height on the spatial pattern.Study sites locates in the Ma Changtan grassland in SuNan country of the north Qilian Mountain(38°47′22.1″—38°52′11″ N,99°45′11.7″—99°57′41.2″ E).In early August,2011,we recorded aboveground biomass,plant height and fine-scale(0—100 cm) spatial pattern of sexual plants and vegetative plants of S.krylovii population from 2 m×2 m grids(2 cm×2 cm quadrats) in four plots under four kinds of degradation gradients: no degradation,light degradation,moderate degradation and heavy degradation.The measured value and the value of upper and lower envelopes were calculated by the Visual Fortran 6.5 based on the coordinate getting by GetData Graph Digitizer 2.22,the point pattern analysis and Monte Carlo stochastic simulation method were used to quantitatively analyze spatial pattern,the excel software was used to construction,the number of Monte Carlo stochastic simulation was 20 times with the step of 2 cm.The results showed that:(1) Under no degradation conditions,the spatial pattern of sexual plants and vegetative plants were aggregated at different scale,the sexual plants were aggregated at 94—100 cm scales,the vegetative plants were aggregated at 22—46 cm scales.(2) In the process of natural pasture degeneration,along with the aboveground biomass and plant height changed,the reduplication of aggregated between sexual plants and vegetative plants developed,the scale changed form 18—19 cm and 54—68 cm to 45—78 cm.(3) Along with the aboveground biomass and plant height of the sexual plants developed,the aggregated was the important pattern type,the aggregated scale changed form 11—19 cm and 54—82 cm to 25—92 cm.(4) Along with reduction of aboveground biomass and plant height of the vegetative plants,the aggregated and regular were the important pattern types,the aggregated scale changed form 18—68 cm to 45—78 cm,as well as the regular scale changed form 0—9 cm to 0—19 cm.To sum up,the spatial pattern of sexual plants and vegetative plants of S.krylovii population were changed on the different scale and degradation gradient.The changes of aboveground biomass,as well as the plant height,are not only the antecedent conditions affecting scale transformation of spatial pattern,but also the critical factors of population′s status and function change.It may reflect the adaptive approach of regeneration and reproduction when S.krylovii population in the face of the outside interference.