| The subtropical evergreen and deciduous broad-leaved mixed forest is a vegetation type jointly predominated by the forest canopy evergreen and deciduous species,formed by varying degrees of ingredients of fallen leaves caused by subtropical evergreen broad-leaved forest to adapt to the low-temperature environment at the northern latitude or a high elevation.Due to the complex landform and vertical climate differentiation,a large area of subtropical evergreen and deciduous broad-leaved mixed forest in Hubei Jinzi Mountain Forest Farm of State-owned in Lichuan,and its contiguous regional has been preserved.This region is the core area of eastern Sichuan-western Hubei among the endemic centers of Chinese seed plants,it’s also the key region of biodiversity conservation with priority in china.However,no systematic research has been carried out on main dominant populations structure,dynamics based on forest dynamics polt.This work relies on national identity forest ecosystem research station in Hubei Enshi,and the 6 hm2 forest dynamic monitoring plot in accordance with the standards and technical specifications of CTFS was established in Jinzi Mountain Forest Farm of State-owned in Lichuan.Based on first phase dynamic monitoring data of woody plants,using the population structure was instead of age classes,survival analysis function,dynamic indices,time sequence,niche and other research methods to analyze the structure and dynamics of 6 main dominant populations.The results showed as the following:(1)There were a total of 196 types of woody species and 4 3847 individuals DBH(diameter at breast height)more than I cm,which belong to 52 families and Ⅲgenera in Jinzi mountain forest dynamics plot.Among them,there are 69 species of evergreen trees,which belong to 26 families and 44 genera,including 1 6567 individuals,and 127 species of deciduous trees,belonging to 44 families and 81 genera,2 7280 individuals.The 2 species with the largest important value(Ⅳ)of tree layer,arbor sub-layer and shrub layer were the Castanea henryi and Carpinus fargesiana,Ficus heleromorpha and Metapanax davidii,Eurya alata and Camellia cuspidata,respectively.Among them,C.henryi population IV is the largest,which belongs to the constructive species.E.alata populations of IV after C.henryi,the dominant position in the shrub layer significantly.Evergreen and Deciduous Broad-Leaved Mixed Forest in Jinzi Mountain is a co-dominant community which is composed of many heliophilous plants and a handful of shade-tolerant plants.(2)C.henryi population with DBH<7.5 cm only accounted for 6.84%of the total population.The spindle-shaped size and height structure indicated a depression tendency for this population.C.fargesiana population of young individuals richness,Size and height of the structure between the inverse J-shaped and spindle-shaped,which belonging to increasing and declining alternatively population,and the number of individuals fluctuates.The size and height structure of the 4 populations(F.heteromorpha,M.davidii,E.alata and C.cuspidata)showed the inverse J-shaped.These populations can natural regenerate well,belonging to increasing populations.Most of species belong to increasing population and the whole community is in a positive succession.(3)The survival rate of C.henryi population was low for young individuals,The peak value of mortality rate was in the Ⅱ age class.The mortality rate was reached maximum at Ⅷ age class,the survival curve of the population approached to Deevey-Ⅲ type.The individual concentration of population showed slightly decreasing at the early stage,fluctuation at the middle stage and depressing at the late stage,respectively.The survival rate of C.fargesiana population was high for young ages,the mortality rate of middle age individuals were fluctuation and mortality rate were increase quickly after V age class,the survival curve of the population tends to Deevey-Ⅱ type.The population reduced slightly at the early stage,fluctuation at the middle stage and declined at old ages.The mortality rate of F.heteromorpha and M.davidii showed a decreasing trend with the increase of age class,while the E.alata and C.cuspidate population increased with age.The survival curve of the population tends to Deevey-Ⅱ type.The F.heteromorpha showed a sharper reduction at the early stage,fluctuation at the middle stage and declined at old ages.M.davidii,E.alata and C.cuspidate showed a sharper reduction at the early stage,grew stably at middle ages and declined at old ages.(4)The structure of the lowest C.henryi population growth,in the early state of recession type and minimum sensitivity to external interference.In the next 8 years,the young and middle aged individuals will decay,and the number of aging individuals will increase.C.fargesiana population structure belongs to the growth type,was sensitive to external interference.The time sequence analysis predicted that the number of the individuals DBH<7.5 cm will slightly reduced and the individual DBH ≥7.5 cm increased obviously.F.heteromorpha population structure of high growth,the growth of random interference under the condition of the highest,was sensitive to environmental change.The population of young,middle age and aged individuals will increase with the extension of recovery period.The other 3 population(M.davidii,E.alata and C.cuspidata)showed a stable growth type,which was less sensitive to environmental change,and the population growth rate increased with the extension of recovery period.(5)The main dominant populations were more fully share the environmental resources,and there was no significant difference between the interspecific niche release and compression.The descending order of niche breadth value was to some extent in accordance with that of important values,interspecific niche similarity was more than 0.5 accounted for 53.33%of the total number interspecifices.The niche overlap value of more than 0.50 of the total 46.67%species pairs,the common use of a group of environmental resources or the degree of joint use of small,the competition that the use of environmental resources between various groups is not fierce.C.henryi and F.heteromorpha with lager niche breadths present a lager overlap with other populations. |
