| Evergreen deciduous broad-leaved mixed forest is the main vegetation type in subtropical mountain area of China,which has important ecological and economic value.Mulinzi National Nature Reserve in Southwest Hubei Province has both well preserved mature community communities and secondary forest communities in different restoration stages.Research on the short-term dynamics of the mixed evergreen and deciduous broad-leaved forest communities at different recovery stages can better grasp the community dynamics,and provided scientific basis for the protection,restoration and sustainable management of forest ecology in this area.This study uses two survey data of 30 sample plots of 25-year-old secondary forest after clear-cutting in the mid-1990s(SF25),40-year-old secondary forest after clear-cutting in the early 1980s(SF40)and Mature forest(MF)in the Mulinzi Nature Reserve in2014 and 2019,analyzed the community species composition and diversity and the renewal dynamic characteristics of the top 5 dominant species at different levels of important value,and compared the renewal dynamics and differences of the community structure and dominant species populations at different restoration stages.The main results were as follows:(1)The number of families,genera,and species of the community at different stages of recovery was not much different,but the number of individuals varies significantly.The number of families and genera has not changed in the past five years,the number of species has decreased slightly,and the total number of individuals has decreased significantly.The rate of decline was as follows SF25>SF40>MF.The variation of species diversity at different levels was relatively small,and the overall performance is relatively high species diversity,low dominance and uniformity.In the two surveys,the average values of Shannon-wiener diversity index,Simpson dominance index and Pielou evenness index were all SF40>SF25>MF.The composition of the top 30 species with important values has changed very little during the five years.Only a few species have entered or exited.The size and ranking of important values have changed to a certain extent,but the magnitude of change was small.(2)From the point of view of the average DBH,the average DBH of Schima superba in mature forest decreased in 5 years,while the average DBH of other dominant species has increased to varying degrees.The overall increase was as follows SF25>SF40>MF,in which secondary forest was significantly larger than that of mature community.In terms of the average breast height cross-sectional area,the average DBH cross-sectional area of the 4 dominant species in the SF25 has decreased,the SF40 has2 species,the MF has 1 species,and the rest have increased.The average increment performance was SF25>SF40>MF,among them,the SF25 was significantly larger than the SF40 and MF.(3)The results of the two surveys showed that the dominant species of the community at different stages of recovery were all with a higher average annual mortality rate than the annual average recruitment rate,and the community showed a negative growth.Among them,there were 13 species of negative growth type populations in SF25,11 species of SF40,and 7 species of MF.In addition,the species with the highest mortality and replenishment rates at different stages of recovery were mainly concentrated in the sub-arbor layer and shrub layer.(4)The niche breadth values of dominant species at various levels at different restoration stages showed an overall downward trend during the five years,the species with the largest changes were mainly concentrated in the sub-arbor and shrub layers,but the changes were relatively small.Among them,there were 10 species in which the niche breadth of secondary forests and aging forests have declined in 20 years,and 9 in SF40.The niche overlap value of the dominant species at different levels in SF25 increased slightly,and SF40 and MF decreased slightly.Among them,there were 2 pairs of SF25 and MF with decreasing niche overlap and 8 pairs with increasing niche,and SF40 with 2 pairs of decreasing niche overlap and increasing There were 6 pairs of species,and the other 2 pairs remain unchanged.(5)The dominant species in the SF25 sub-arbor layer and MF shrub layer changed from a non-significant negative correlation to a non-significant positive correlation.The dominant species in the arbor layer of the SF40 changed from an insignificant positive correlation to a significant positive correlation.The number of positive-associated species of dominant species at different stages of restoration was increasing.The number of positive-associated species of dominant species in different recovery stages showed an increasing trend,but the degree of association was weak,and the change was not significant,and remained basically stable.In addition,the number of positiveassociated species in the old forest was more than that in the secondary forest. |
