Ecosystem Structure And Health Assessment Of Mixed Forest Of Pine And Oak In Huanglong Mountain

Due to excessive logging in Huaglong Mountain,the forest resources are mainly secondary forest,and the forest is characterized by low quality,low efficiency,low productivity and poor community stability.The implementation of the‘Natural Forest Protection Project'has effectively protected most of the degraded secondary forests.After a long period of natural restoration,the forest stands in natural regeneration and succession,complex forest conditions and diverse succession patterns were formed.In order to make the forest better play its ecological function in Huaglong Mountain,taking the mixed forest of pine and oak as the research object,forest structure,species diversity and niche,spatial structure were investigated to assess the health of the forest ecosystem so that to guide future forest management in theory,and to promote the sustainable and healthy development of forest.The major findings of this work include:1.The mixed forest of pine and oak was in the early successional stage,not reached a steady state.The diameter distribution showed as an inverted‘J'type,riching in saplings in the forest and regeneration resources.The tree height distribution was relatively messy,which was related to the early stage of succession.2.The species richness and abundance were scale dependent.The richness variance with increasing of the scale showed a tendency:slowly increased–decline–increased,but the coefficient of variation decreased.When the scale increased continually to 2500 m~2,the coefficient of variation showed a slight increasing trend.The multivariate variance increased almost monotonically with the increase of sampling scale,but the coefficient of variation decreased.There was no obvious correlation between the species niche breadth and niche overlap.Due to the niche breadth reflects the species resource utilization status,different biological and ecological characteristics of species were not completely consistent with the satisfaction of resources.Therefore,species with wide niche,the niche overlap was not necessarily high.3.As a dominant species of the population,Pinus tabulaeformis had obvious advantages in population density and basal area.The average mingling in the stand was0.683,indicating that the stand belongs to the category of intensity mixed.The mixed degree of P.tabulaeformis was the lowest in all tree species.The average size ratio in the stand was0.487,indicating that there was no statistical difference in the size differences of trees.The average angle was 0.538,showing that the distribution of tree position in this stand type was aggregation distribution,but the degree of clustering was low.The openness of the stand was0.21,and the forest growth space was in a critical state of serious shortage and deficiency.By cutting trees to adjust the spatial structure of forest,and the cutting intensity was 7%,64trees were cut.4.The distribution pattern of main tree species changed obviously along with the scales in the mixed forest of pine and oak.P.tabulaeformis,Acer ginnala and Populus davidiana population were aggregated at a small scale of 0-5m,yet mostly randomly distributed at other scales.Quercus liaotungensis population was aggregated at most scales,and the degree of aggregation was higher than the other three populations.In the spatial correlations of the main tree populations,P.tabulaeformis and Q.liaotungensis population were positively correlated at most scales,with only a small correlation at the scales of 32-35m and 37-40m.P.tabulaeformis and A.ginnala,P.tabulaeformis and P.davidiana population were positively or negatively correlated at several scales,however no correlation was found at most scales.A.ginnala and Q.liaotungensis,A.ginnala and P.davidiana population showed a different degree of negative correlation,indicating that there was a strong competition among them.5.The distribution pattern of individuals at different developmental stages of P.tabulaeformis population changed with scales,showing that the saplings and small trees expressed as aggregated distribution at small scales,and the gathered strength higher in plot I,with the scales increased,individuals tended to be randomly distributed,middle and large trees showed random distribution,the correlation between the different growth stage individuals,saplings and small,saplings and middle trees were significantly positive correlation at the small and middle scales,no significant correlation at large scales,saplings and large trees were negative correlation at some scales,no significant correlation between small and large,middle and large trees.6.The comprehensive evaluation of forest ecosystem health showed that unhealthy samples accounted for 16%of the total assessed area,mid-healthy samples for 36%,sub-health samples for 28%,and healthy samples for 20%.The mixed forest of pine and oak in Huanglong Mountain was in a mid-healthy state.