Community Structure And Characteristic Regeneration Of Four Typical Broad-leaved Secondary Forests In Qinling Mountains

This paper carried research on community strcture and regeneration characteristics of thefour broad-leaved secondary forests of Qinling mountains, to provide theoretical reference forthe nature regeneration of the forests and near-nature recovery. Though the investigations ofthe typical sample plots, taking the important value of tree species and woody plantregeneration layer, diameter structure and height class structure of dominant tree species andregeneration type of woody plant layer as the index, we analyzed regenerationcharacteristics of the four broad-leaved secondary forests and the effects of different factorson the regeneration layer by the densities of the regeneration layer.The results showed that the important value of Betula albo-sinensis was178.12,occupying59.4%of the total number of tree species, which was the constructive species.There were25tree species among59woody species in regenerational layer, occupying42.4%of the total number of woody plant species.Shrubs species are in the majority of theregeneration woody plant seedlings, the advantage position of Betula albo-sinensis in thecommunity renewal layers is not obvious.Betula albo-sinensis secondary forest woody plantseedlings in the number of40-60cm height class within a maximum of the total amount,0-20cm height class distribution very little.The main regeneration type in renewal woodyplant was sprouting. The effect of stand density on saplings and seedlings density was similar,both the saplings density and the seedlings density climb up and then decline with the standdensity increasing. The sunny slope (SW40°)direct was benificial to saplings. As changingdirection to shady slop, the seedlings density increased but sapling density showed varyingdegrees of reduction.There were various effects of altitude on Betula albo-sinensis secondaryforests regeneration woody plant.When the altitude rose up from1825m to2449m, the densityof seedings decreased gradually, while the density of saplings increased. The density ofsaplings decreased and the density of seedlings increased with the altitude increased to2467m.The results showed that the important value of Betula platyphylla was139.68, occupying 46.5%of the total number of tree species, which was the constructive species. There were26tree species among50woody species in regenerational layer, occupying52%of the totalnumber of woody plant species.Shrubs species are in the majority of the regeneration woodyplant seedlings, the advantage position of Betula platyphylla in the community renewal layersis not obvious.Betula platyphylla secondary forest woody plant seedlings in the number of60-80cm height class within a maximum of the total amount,0-20cm height class distributionvery little.The main regeneration type in renewal woody plant was sprouting. The effect ofimpact factors on saplings and seedlings density in Betula platyphylla secondary forest wassimilar to Betula albo-sinensis secondary forest.The results showed there were25species in tree layer. Quercus aliena var. acuteserrataoccupied dominant status in community, its important value was149.18. The subdominantspecies was Pinus armandii, Carpinus cordata, ect. There were25tree species among41woody species in regenerational layer, occupying68%of total amount. The dominant specieswas Acer grosseri, Litsea pungens,ect. The seedlings bank was abundent, the height class andage class were lower. The main regeneration type was seedling. The effect of stand density onsaplings or seedlings density was different, the saplings and seedlings density was increasedwith the stand density from720trees·hm-2up to1460trees·hm-2, then decreasing with the standdensity increasing. The saplings density decreased continuously with the stand densityincreasing. There were various effects of slop direct on the seedlings or saplings. The sunnyslop (SW3°)direct was benificial to sapling or seedlings.The seedlings density decreasedsharply. As changing direction to shady slop, the seedlings density increased. The saplingsdensity decreased nevertheless. The saplings density increased as altitude from1083m up to1547m, then decreasing with altitude up to1882m. The seedlings density increased fromlower altitude to higher altitude.The results showed that the important value of Quercus variabilis was180.56, occupying60.2%of the total number of tree species, which was the constructive species. The resultsshowed there were33species in tree layer. Quercus variabilis occupied dominant status incommunity, its important value was149.18. There were25tree species among41woodyspecies in regenerational layer, occupying68%of total amount. The seedlings bank wasabundent. The main regeneration type was seedling. The effect of impact factors on saplingsand seedlings density in Quercus variabilis secondary forest was similar to Quercus valienasecondary forest.The Betula albo-sinensis and Betula platyphylla forests are at the end of succession,were in the degenerate stage. The population of Quercus aliena var. acuteserrata had greatregeneration ability, The population of Quercus variabilis had certain regeneration ability.Stand density, altitude, slope direction and soil pH value were the main influencingfactors on regeneration.