重牧对荒漠草原主要植物种和功能群组织力的影响

Effect of Heavy Grazing on the Organization Ability of Main Plant Species and Functional Groups in a Desert Steppe

在内蒙古短花针茅荒漠草原区连续12年进行对照和高载畜率二处理的随机区组试验,测定样方内植物种类、高度、密度和生物量,评价重度放牧对群落组织力的影响,并从主要物种和功能群角度剖析群落组织力改变的主导原因。结果显示:(1)重牧区群落组织力下降至对照区的69%,转变为少数植物占绝对优势的简单结构群落。(2)主要物种的年度组织力均值排序由对照区的短花针茅>冷蒿>无芒隐子草>木地肤>银灰旋花>细叶韭>栉叶蒿>狭叶锦鸡儿,转变为重牧区的短花针茅>冷蒿>无芒隐子草>银灰旋花>栉叶蒿>木地肤>细叶韭>狭叶锦鸡儿,其中无芒隐子草组织力显著增加,木地肤、细叶韭、狭叶锦鸡儿组织力显著下降。(3)功能群的年度组织力均值排序,由对照区的多年生禾草>灌木、半灌木>多年生杂草>一年生草本,转变为重牧区的多年生禾草>灌木、半灌木>一年生草本>多年生杂草,其中优势功能群多年生禾草组织力显著增加,物种最丰富的多年生杂草的组织力显著下降。重牧区优势物种和主导功能群组织力的上升或不变,非优势物种及多物种功能群组织力的下降,表明群落自组织能力下降的主要原因是群落物种多样性减少、组成结构变差。组织力参数的年度动态反映出围封禁牧对群落自组织能力的恢复起至关重要的作用。

The objective of the study was to find the influence of long-term overgrazing on the organization ability of grassland community.AStipa breviflora steppe in Inner Mongolia with control and heavy grazing were studied by randomized block test in 12 years.The species,height,density and biomass of plant in samples were tested.The effects of heavy grazing on community organization ability were evaluated.The reasons of it were analyzed from the changing of main species and functional groups.The results showed that organization ability of community dropped to 69%of it with no grazing.It transformed into a simple structural community which dominated by less plants.The annual mean values of main species organization ability were ranked.In no grazing area,the sequence of organization ability from high to low was：Stipa breviflora,Artemisia frigida,Cleistogenes songorica,Kochia prostrata,Convolvulus ammannii,Allium tenuissimum,Neopallasia pectinata,Caragana stenophylla;in heavy grazing area,the sequence of organization ability from high to low was：Stipa breviflora,Artemisia frigida,Cleistogenes songorica,Convolvulus ammannii,Neopallasia pectinata,Kochia prostrata,Allium tenuissimum,Caragana stenophylla.Organization ability of Cleistogenes songoricain heavy grazing area increased significantly.Kochia prostrata,Allium tenuissimumand Caragana stenophylladecreased significantly.The annual mean values of functional groups organization ability were ranked too.In no grazing area,the sequence was：perennial grasses,shrubs and semi-shrubs,perennial forbs,annual grasses;in heavy grazing area,the sequence was：perennial grasses,shrubs and semi-shrubs,annual grasses,perennial forbs.Organization ability of perennial grasses in heavy grazing area was greater than that in no grazing area.It was less than that with no grazing for perennial forbs which had most species.Organization ability of dominant species and functional groups were raised or remained the same in heavy grazing area.In the same time,organization ability of no dominant species and functional group with most species declined,which indicated that the main reason of community self-organizing ability decreasing is that diversity decreased and the composition of communication got worse.In addition,the annual dynamic curves of organization ability showed that forbidding grazing is crucial to the recovery of community self-organizing ability.