The Characteristics Of Species Diversity And Its Environmental Explanation In The Artificial And Natural Restored Forests Of JiuLian Mountain

Human activities have caused massive loss of forest resources,with the continuous reduction and fragmentation of the primary forest area,the bare land or secondary forest was gradually formed,which also accelerated the rate of species extinction.The impact of global biodiversity loss on ecosystem function is one of the most concerned fields in ecology.Therefore,there is a current concern whether the forest can be restored to the levels before after human disturbance.Thus,we should pay attention to the differences between the artificial restoration model and the natural restoration model in the community structure,species diversity,phylogenetic diversity,and the role of environmental factors in the recovery process of species diversity and phylogenetic diversity.Three typical forest communities including undisturbed primary evergreen broad-leaved forest,natural restoration of 36 years old secondary forest and the artificial restoration of 42 years old Cunninghamia lanceolata forest were sampled as1 ha plot respectively in Jiulian mountain.Based on the inventory of the calculations of species diversity and phylogenetic diversity(including ? and ? diversity)and the determination of environmental factors for these three forests,we analyzed the variations of community structure,diversity and environmental factors and explored that how environmental factors drive the change pattern of species diversity and phylogenetic diversity under the natural and artificial restoration modes.The main research results are as follows:(1)There is a similarity between secondary forest and Chinese fir forest in dominant family and breast-height basal area,but there is a big difference between these two forests and the primary forest in the main tree species,and a large species turnover rate for the succession progress.The diameter class distribution of the primary forest was close to the exponential decline with the inverted "J" type,indicating the community was more stable than the other two forest types.Compared with the secondary forest,the diameter class distribution of Cunninghamia lanceolata forest is closer to the inverted "J" type exponential decline,except a smaller proportion in small trees.In the vertical structure,the secondary forest is more multilayer than Chinese fir forest,but the dwarf individuals are less than Cunninghamia lanceolata forest,which may be due to the natural thinning.The accumulation rate of adult trees was lower than that of Chinese fir forest.(2)For the index of ? diversity,the order of species diversity level: the primary forest > secondary forest > Cunninghamia lanceolata forest.There is a clustering phylogenetic structure for both primary forest and secondary forest,while as a phylogenetic divergence for the Chinese fir forest;For the index of ? diversity,thespecies diversity and phylogenetic diversity were significantly different within and between different forest types,the primary forest showed a clustering phylogenetic structure,which indicates a relatively close phylogenetic relation,and similar species composition.However,there were significant differences in species composition between primary forest and Cunninghamia lanceolata forest,as well as between secondary forest and Cunninghamia lanceolata forest.(3)There is a significant difference among different forest types for environmental factors.In terms of soil chemical properties,the primary forest has the highest nutrient content,the organic carbon content of secondary forest was lower than that of Chinese fir forest,and the content of total phosphorus and ammoniacal nitrogen was significantly higher than Chinese fir forest.Compared with the other forest types,the secondary forest has stronger light intensity,smaller leaf area index and larger canopy openness.(4)Species diversity was significantly influenced by environment factors both in the artificial recovery model(Chinese fir forest-primary forest)and natural recovery mode(secondary forest-primary forest),and most of variations in species diversity(73% and 78%)can be explained by environmental factors.The interaction among soil,light and topography could explain the largest amount of diversity's variations.Moreover,elevation,leaf area index,available phosphorus,canopy openness played an important role in regulating species diversity in both natural and artificial recovery modes.Furthermore,soil factors explained alone the more variation in natural recovery mode,while the topography and soil explained a lot of variation alone.(5)There is difference in effects of environmental factors on phylogenetic structure under different recovery modes.Soil ammonium nitrogen,nitrate nitrogen and leaf area index had significant positive correlation with the phylogenetic diversity under Chinese fir forest-primary forest mode,.Net relatedness index was positively related with soil total phosphorus and slope aspect and negatively related with soil available phosphorus.Therefore,the content of available nitrogen and phosphorus in soil were the main factors in affecting the phylogenetic structure under the artificial restoration mode.Under the natural restoration model(secondary forest-primary forest),thephylogenetic diversity was significantly negatively correlated with available phosphorus,and significantly positively correlated with elevation.Additionally,there was no significant relationship between environmental factors and net relatedness index.Soil available phosphorus and elevation are the main factors in affecting the phylogenetic structure in natural restoration mode.In a word,there were some differences in community structure,species diversity and phylogenetic diversity among Chinese fir forest,secondary forest and primary forest.From artificial recovery mode(Chinese fir forest-primary forest)and naturalrecovery mode(secondary forest-primary forest).Species diversity and phylogenetic diversity are recovered in the process of community succession.Soil,topography and light play a larger role in the process of biodiversity recovery.However,the role of environmental factors is different in phylogenetic diversity recovery under different restoration models.In summary,as it is more similar in species diversity and phylogenetic structure,the community structure and diversity were helpful for community succession under the natural restoration model from secondary forest to primary forest.