Comparative Study On Community Characteristics Of Several Abandoned Cunninghamia Lanceolata Forests In Zhejiang Province

Zhejiang Province is located in a subtropical region and its zonal vegetation is evergreen broad-leaved forest.Due to historical factors and frequent human activities,a large number of primary forests have been cut down and destroyed.In the middle and late stages of the last century,a large number of Cunninghamia lanceolata(Chinese fir)was planted for the needs of production development.The Chinese fir forest has therefore become the main plantation type in the province,which has the characteristics of simple structure,poor resistance to adversity,and low species diversity.With the expansion of the number and area of nature reserves and the implementation of con-commercial forest protection policy,the remaining large areas of Chinese fir forest in the past,after giving up the management mode of artificial forest(abandoning management),closed hillsides to facilitate afforestation,and the natural succession are gradually completed to restore the native species.In this study,we selected Chinese fir forest communities as the starting point and established 6 one-hectare forest dynamic monitoring sample plots to conduct vegetation survey in 4 nature reserves of Zhejiang Province.Each woody plant with DBH(diameter at breast height)≥ 1 cm was surveyed and species name,DBH,height and coordinates were recorded.Through the community species composition,structure,species diversity and spatial distribution pattern of the analysis,to explore the trend of community succession and community recovery mechanism to provide the reference,to the recovery of the zonal forest community for Chinese fir forest and provide scientific evidence for adaptive management,help to make reliable forest management decisions,the better development of forest ecosystem function and value.The main conclusions are as follows:(1)There was little difference in the number of species families and genera,but there was some difference in the number of species.The species richness of the non-cutting communities was significantly lower than that of the cutting communities,and different cutting intensities had little effect on the species richness of the subtree layer and shrub layer.But only communities that experienced high levels of cutting had more species entering the canopy.In each abandoned Chinese fir forest,the importance value of Chinese fir decreased gradually with the gradual improvement of cutting degree,and the dominant position of Taxodiaceae and Cunninghamia also decreased.In addition,the community diameter class structure of all the plots showed an inverted "J" shape,which indicated that the natural recovery of the community was good after the abandonment.The diameter class structure of Chinese fir was different in different communities,which was mainly affected by the cutting mode of Chinese fir before abandonment.(2)4 indicators are selected to describe the species diversity of the community:Simpson index(D),Shannon-Wiener index(H),Pielou’s evenness index(P),and species richness(S).The species diversity indices in the low,medium and high cutting plots were significantly higher than those in the non-cutting plots.Three diversity indices(D,H,P)had the same variation pattern in each community,while S was not completely consistent with their values.Through the analysis of the whole plot,it is found that the number of Chinese fir(abundance and relative abundance)was significantly negatively correlated with species diversity at sampling scales of 10 m × 10 m(small),20 m × 20 m(medium),and 50 m × 50 m(large).When the scale reached 100 m ×100 m,the correlation between them weakens or even disappears,which may be caused by more habitat heterogeneity at a large scales.By classifying the number of Chinese fir and analyzing the variance of species diversity between groups,we found that the higher the number of Chinese fir was,the lower the species diversity was at the three scales.Among them,when the relative abundance of Chinese fir reaches 30%,the community species diversity decreases significantly.(3)Through the comparison of the Complete Spatial Randomness model and the Heterogeneous Poisson process model,the main factors influencing the abandoned Chinese fir forest habitat heterogeneity is Chinese fir itself,the community of the results of the planting and cutting Chinese fir decided the habitat heterogeneity degree,this has nothing to do with the cutting intensity,and related to the cutting way.The more uniform the individual distribution of Chinese fir retained after cutting,the lower the degree of habitat heterogeneity in the sample plot.The more concentrated the individual distribution of Chinese fir retained after cutting,the higher the degree of habitat heterogeneity in the sample plot.The spatial association between Chinese fir and the main broad-leaved species was different in the communities composed of different species.In the broad-leaved communities dominated by evergreen species,Chinese fir was usually positively correlated with dominant evergreen species,but not with dominant deciduous species.In the broad-leaved communities dominated by deciduous species,there was a negative correlation between Chinese fir and dominant evergreen species,and a positive correlation or no correlation between Chinese fir and other dominant deciduous species except that there was a good coexistence between Chinese fir and Albizia kalkora.