土壤水分对黄土丘陵区演替序列种种间竞争的影响

Interspecific Competition of Six Succession Series Species with Different Soil Moisture Treatments in Loess Hilly Region

种间竞争是不同物种为争夺资源发生的相互关系,对群落植被演替、恢复有重要意义。同时水分是黄土丘陵区植物生长的限制因素,该区多物种种间水资源竞争研究较少,为此选取该区6种演替序列种,采用种对试验法研究其对土壤水分变化的竞争响应。结果表明:(1)除狗尾草外,其他5种植物的生长指标和土壤水分变化趋势基本一致,地下部分变化程度大于地上部分。不同植物最适水分条件不同。(2)单位竞争能力与总竞争能力相似地反映植物种间竞争状况。狗尾草和白羊草在中高水竞争力均高于同组的猪毛蒿、达乌里胡枝子,低水反之。铁杆蒿随着水分减少,竞争力低于茭蒿。受水分胁迫时,达乌里胡枝子、白羊草的竞争力>茭蒿、铁杆蒿>猪毛蒿、狗尾草,即演替后期种竞争能力>演替中期>演替初期,符合演替生态位理论。竞争的不对称随着环境生产力的增加而降低。随着演替中土壤水分的减少,物种耐水分胁迫的能力逐渐增强,从而促使演替的继续。

Interspecific competition refers to the relationship between species competing for resources,which is critical to community succession and vegetation recovery.As an essential and important resource for growth,water exerts the significant effect on formation and development of interspecific relations.However,the interspecific competition for water in the hilly loess arid region was little known,where the water remained the main constraint resource for growth.Six succession series species were selected to study their competitive response to soil moisture change based on the pot experiments.The results showed that:(1)six species′growth conditions with the different soil moisture treatments were not the same at both monoculture and pair-wise treatment,biomass and height of all five species showed a similar trend with soil moisture except for Setaria viridis,and the biomass of belowground varied more greatly than that of aboveground,interspecies competition had affected the growth of plants;(2)total competition intensity and pergram competition intensity similarly reflected the status of interspecies competiton,the competiton of S.viridis and Bothriochloa ischaemum was greater than its counterpart species Artemisia scoparia,Lespedeza dahuricain medium and high water conditions while the reverse pattern occurred in low water condition.Artemisia sacrorum′s competiton was lower than Artemisia giraldii with decrease of soil moisture.The competitiveness ranked as the order:L.dahurica,B.ischaemum>A.sacrorum,A.giraldii>S.viridis,A.scoparia under water stress,showing that the competition of late succession species was larger than succession mid-early stage and complying with the succession niche theory.Different plants had different optimal soil moisture.Competition asymmetry intensified the effects of water deficiency on the plant growth.Asymmetry of interspecies competition was caused by accessing resource asymmetry of relative and neighbor species.Theplants′tolerance ability gradually increased with decrease of soil moisture in the process of succession,thus prompting further community succession.