Community Structure And Succession Of Typical Restoration Community In The Hilly And Gully Loess Plateau, China

The objects of this investigation were4kinds of typical restoration community in theHilly and Gully Loess Plateau,They are man-made Robinia pseudoacacia forest, man-madeCaragana korshinskii forest, secondary Betula platyphylla forest and secondary Quercuswutaishanica forest. Studied the structure of community by species composition, speciesdiversity, population structure of dominant species and point pattern analysis, and tried toexplain the succession mechanism. Objective was providing a theoretical basis for mechanismof revegetation. The main results of this paper are as follows:1. Plants of Rosaceae and Compositae are mian members respectively which built thebush community and grass community in this area. Most of these plants are drought tolerant;Species richness of secondary forest much greater than man-made forest, because there aremore difference environment in secondary community, and this phenomenon is good for morespecies; Species richness is consistent with the laws of grass>bush>arbor in man-madeforest and secondary forest; Species diversity often conform to increase first and thendecrease in man-made fores,and accords with pioneer community> late-successionalcommunities.2. In the sample plots, the DBH class structure of Populus young and middle ageR.pseudoacacia man-made forest were reverse “J”-shaped,which indicates that theirpopulation quantity is increasing; Population of man-made Platycladus orientalis forest wasstability.But the mature R.pseudoacacia man-made forest’s continuous persistent regenerationcapability was lack. The DBH class structure of B.platyphylla was bimodal.The individualswith large DBH and small were abundant,and relatively few medium DBH were found.Theresult indicets that canopy B.platyphylla trees with large DBH are in the advantage positionand the small trees which have a large quantity may fail to become medium trees due to lackof enough light. The DBH class structure of Q.wutaishanica showed a approximately normaldistribution,suggesting they are stable in short future. Q.wutaishanica is a kind of zonalityspecies,and they can continue to develop into a climax.3. In this study, B.platyphylla had a random distribution at almost all scales,it indicating aslight environmental pressure as a dominant species. Q.wutaishanica was clumped at smallscale, and had a random distribution at other scales,This spatial pattern indicates that Q.wutaishanica are also in an advantage position. Populus davidiana were significantlyscattered at scale of14～17m and had a random distribution at other scales.P.tabulaeformiswere significantly clumped at small scale because Pinus tabulaeformis has heavy seeds andsaplings always occur around the mother tree. The analysis of interspecific correlations of themain populations showed that B.platyphylla had negative correlations with Q.wutaishanicaand in small scale and positive correlations at scale of5～8m and21～22m.There was apositive correlations between Q.wutaishanica and P.tabulaeformis at scale of13～22m,suggesting that they can coexist at these scales.No significant correlations were observedbetween other species pairs.Spatial distribution pattern of standing trees is affected by theirbiological property at small scales,whereas depends on the heterogeneity of environment atlarge scales,such as light,moisture or nutrient.With the growth of forest age,rivalry of saplingsled to a disperse pattern,finally,it will be developed into random pattern.Interspecificcorrelations of populations had not shaped an obvious correlation and always tended torandom at the early stage of succession.With the development of succession,mutuallybeneficial species will be closed to each other,conversely, they will be far away.All species beconserved in climaxes will tend to positive correlations for the stability of community.Infuture, secondary B.platyphylla forest in Ziwuling mountain on Loess Plateau will change intoa model of multi-species mixed forest, later, this community will become Quercus-Pinusmixed forest and remain stable in a long period of time, and finally this community will betaken place of pure Q.wutaishanica forest.