Keep Difference Density Of Mother Tree Have Influence Of Community Structure Of Natural Secondary Forest Of Pinus Massoniana

Using community ecology investigation method, to study the community structure and Pinus massoniana population spatial distribution pattern, community diversity, community stability, soil nutrient composition of Pinus massoniana secondary forest formed by keeping different parent trees after clear cutting, so as to analyze the the recovery condition and succession tendency for Pinus massoniana secondary forests, in order to provide the theory basis for natural vegetation restoration and reconstruction of Pinus massoniana forest community,forest management and biodiversity protection; provide scientific support and guidance for afforestation. Main conclusions are as follows:(1)community characteristics: the natural secondary forest has the characteristics of species diversity, the tree layer have 17 species,belonging to 13 families, 15 genera, common species have Pinus massoniana, Quercus alien,Liquidambar formosana and Cyclobalanopsis glaucoides; The shrub layer have 25 species, belonging to 22 families, 23 genera, common species have Camellia oleifera, Lyonia ovalifolia,Myrsine africana, Lindera glauca; The herb layer have 6 species,belonging to 5families, 6 genera, common species have Dicranopteris dichotoma, LopHatherum gracile, Miscanthus floridulus. Compared to artificial forest under the similar condition, the tree layer structure of natural secondary forest is more abundant, shrub layer and herb layer has no much difference. Whole crown density is big of tree layer, an average of 80%; the shrub layer is relatively abundant, coverage of 30%; the herb layer structure is relatively drab, average coverage of 15%. In general, the whole community to the use full of space. Two surveys in 2002 and 2004,the biggest density of Pinus massoniana forest are C treatment(keep Pinus massoniana trees 3 plants/mu); the survey in 2014, D treatment(keep Pinus massoniana trees 4 plants/mu) have 266 Pinus massoniana plants / 600 m2 after natural thinning nearly half, the other processing Pinus massoniana natural thinning is larger, A treatment(keep Pinus massoniana trees 1 plant/mu) have maximum up to three quarters, it has to do with competition of other tree species in the community. In 2014,the average diameter of Pinus massoniana have breast height is 8.27 cm,tree diameter of each processing secondary forest have the highest proportion in 5cm< D≦8 cm.(2)Pinus massoniana population distribution pattern is clumped in natural secondary forest, cluster degree have certain differences. Pinus massoniana population distribution pattern analysis can help to have a better understanding for the relationship between species and habitats andspecies in the community. The mean variance ratio index(ID), poly block index(IP) and Morisita index(M) value are greater than 1 in the four treatment types of Pinus massoniana natural secondary forest, Pinus massoniana population structure types are gathered distribution. By t-test values show that the mean variance ratio index is extremely significant difference(ID), meaning that Pinus massoniana population very significantly cluster distribution; Negative binomial parameter(K)values are greater than zero and gradually increasing with respect in four treatment types of Pinus massoniana natural secondary forest, show that concentration are decreases; Average congestion index(m*) are larger in four treatment types, where D treatment reached 19.79 for average congestion index, Pinus massoniana crowded effect is the biggest.(3)The characteristics of community biodiversity: compared to artificial forest under the similar condition, the Simpson index, Shannon Wiener index, richness index is relatively large in tree layer of Pinus massoniana natural secondary forest. Each index than the gap is not big in the shrub layer and herb layer.A and B treatment(keep Pinus massoniana trees 1, 2 plants/mu) have diversity significantly greater than C and D treatment(keep Pinus massoniana trees 3,4plants/mu) in tree layer of natural secondary forest. Margalef index have maximum of 2.09,Simpson index has maximum value of 0.72 and Shannon- Wiener index has A maximum value 1.66 in tree layer of the formation of Pinusmassoniana forest with A treatment.D treatment(keep Pinus massoniana trees 4 plants/mu) were greater than A, B, C for diversity of shrub layer and herb layer. After each treatment formation of the secondary community evenness index were characterized: tree layer > herb layer >shrub layer, B treatment is the most uniformly distributed in tree layer. D treatment is the most uniformly distributed in shrub layer. The greater uniformity of the tree layer, the ecological concentration is relatively smaller, the shrub layer distribution is relatively uniform of D treatment,ecological concentration is relatively small, this is in line with a lot of research results. Study of correlation of each treatment and every level found that diversity index and evenness index was significantly correlated.(4)The soil nutrient characteristics: Difference is not big of pH in the whole community. Because the soil is 0 to 30 cm in the surface, in addition to the no. 4 and no. 9 samples, other sample area difference is small of soil organic matter, content are between 40 and 55 g/kg. Total amount distribution content of nutrient from large to small is: the overall total potassium, total nitrogen, total phosphorus, no. 4 and no. 9 sample distribution is large of full capacity, the potential of soil nutrient reserves is large, and it is consistent with the organic matter content distribution.Available content appears as biggest in B treatment, more conducive to plant growth and development. By correlation analysis of soil nutrientand species diversity, found that effective phosphorus with the tree layer and shrub layer of diversity index, evenness index, richness index was significantly negative correlation, pH and total nitrogen were very significant positive correlation with the diversity of the shrub layer, pH and total nitrogen was significantly positive correlation with the evenness of the shrub layer. and the other soil nutrient index were not significant with species diversity. In addition to the total nitrogen content and effective phosphorus content have significant correlation effects on species diversity, other soil nutrient index of species diversity.(5) The community stability characteristics: the community stability was evaluated by Godron method, get the intersection are far away from point(20,80), certain state of instability with all, its relatively stable size order: B treatment(reserved Pinus massoniana trees 1plants/mu), D treatment(reserved Pinus massoniana trees 4 plants/mu), C treatment(reserved Pinus massoniana trees 3 plants/mu), A treatment(reserved Pinus massoniana trees 2 plants/mu). B and D treatment has good processing stability, it has to do with both the community structure and species diversity. Stability index method is used to determine the community stability, B treatment’ stable values are relatively high in the secondary forest, stable value maximum 1.1195, but the stable value is low in the whole the Pinus massoniana forest, The whole community is still in the competition on the succession stages.Studies show that retain a certain Pinus massoniana parent trees for afforestation is feasible.