Evaluation Of Community Characteristics And Close-to-natural Restoration Status In Successional Stages Of Pinus Massoniana Plantations

The conditions of site selection in Zhenlong Forest Farm,Huashan Forest Farm and Paiyangshan Forest Farm were similar,with different forest ages,using the method of cluster investigation.Plantations of Pinus massoniana in different management modes and different latitudes were used to analyze the species composition and diversity of Pinus massoniana plantations community.The biomass models of shrub layer in different Pinus massoniana plantations were constructed,and the biomass distribution pattern and community structure change of different Pinus massoniana plantations community were analyzed,and the quantitative analysis was used to analyze the biomass distribution pattern of different Pinus massoniana plantations community.The characteristics of soil-ecohydrology function of different Pinus massoniana plantations were analyzed.Finally,a restoration evaluation model was established to evaluate and predict the close-to-natural restoration status of different Pinus massoniana plantation.The following conclusions were drawn:(1)There were 117 species of woody plants(belonging to 42 families and 79 genera)recorded by Pinus massoniana plantations of different forest ages,the species richness gradually increased from Yz to Rz stage,but decreased gradually from Rz stage to Oz stage.The similarity among Pinus massoniana plantations communities in adjacent restoration stage was higher than that among non-adjacent communities,and the substitution rate of species between non-adjacent communities was higher.A total of 84 species of woody plants,belonging to 36 families and 62 genera,were recorded in Pinus massoniana plantations under different management modes,the species richness of D1 community was the highest,the species distribution of D2 community was more uniform,and the species diversity of M2 community was lower.The similarity between D1 and D2 communities was high,and the similarity between M2 community and D1 and D2 was low.A total of 208 species of woody plants belonging to 47 families and 112 genera were recorded under Pinus massoniana plantations in different latitudes,with the decrease of latitude,the proportion of tropical species in the community increased and the distribution of temperate species decreased gradually.The species diversity of middle latitudes stands was poor,and the highest(Yh)and low latitudes(Mp,Op)were found in the young forest,the middle-aged forest and the over-mature forest,respectively.The species difference between the middle and low latitudes of over-mature forest(Oz-Op)was the greatest,and the difference of species between mid-latitude and low-latitude medium-ages forest(Mz-Mp)communities was the smallest,and the species difference in the middle ages forest community gradually increased with the increase of the latitude difference.(2)Three models were used for regression analysis of shrub layer and stand trees in community.The results showed that the fitting effect of dry biomass and whole plant aboveground part biomass was better,and the evaluation indexes of model?:W=a×D~b×H~c were the best.The aboveground biomass of Pinus massoniana plantations in different forest ages was:Oz>Rz>Mz>Yz.The aboveground biomass of Pinus massoniana in each forest was from large to small:Oz>Rz>Mz>Yz.The proportion of biomass under the forest increased gradually with the increase of forest ages.The aboveground biomass of Pinus massoniana plantations community and Pinus massoniana in different management modes were as follows:D1>D2>M2.In Pinus massoniana plantations of different latitudes,the aboveground biomass of middle-aged Pinus massoniana plantations community from large to small:middle latitude>low latitude>high latitude.Young and over-mature Pinus massoniana plantations community biomass was the lowest in mid-latitude(Yz,Oz);The aboveground biomass of Pinus massoniana from large to small was low latitude>middle latitude>high latitude,while the highest aboveground biomass of young forest and over-mature forest was high latitude(Yh)and low latitude(Op),respectively.(3)With the increase of forest age,the chemical potential of each species in the community varied from-9.75 to 9.86,which reflected the adaptability of species in Pinus massoniana plantations community of different forest ages.And the species with good adaptability increased gradually and tended to be stable with the growth of the plantations.The community eco-exergy increased rapidly with the growth of forest ages,and the specific eco-exergy decreased.Except Pinus massoniana,the species with less genetic information and its biomass ratio gradually increased.The variation range of species chemical potential of Pinus massoniana plantations in different management modes was-7.20 to 10.60,and 33species with better adaptation were the most in D1.There were 25 species in D2 community.The M2 community was the least,with 23 species.The adaptability of Pinus massoniana in M2 community was not as good as D1 and D2.The community eco-exergy of Pinus massoniana was D1>D2>M2,and the specific eco-exergy of Pinus massoniana was D2>D1>M2.The variation of chemical potential of Pinus massoniana plantations in different latitudes ranged from-9.75 to 11.17.There were 21 and 40 species with good adaptability in Yz and Yh respectively,among which 8 species were common.The adaptive species in Mh,Mz and Mp were 45,30 and 49 species,7 species were common.34 species with good adaptability in Oz and 32 species in Op,of which species 11 were common.Middle-aged Pinus massoniana plantations has the largest Mp in low latitude,the smallest Mh in high latitude,the smallest Yz and Oz in middle latitude between young forest and over-mature forest,and the smallest structure in middle latitude Pinus massoniana plantations.(4)The maximum water-holding capacity of the litter of Pinus massoniana plantations at different ages and the moisture-holding capacity were the largest in Mz,the soil-ecological hydrological function index of Yz was the smallest,and the ecological hydrological function index of the Oz community was the largest.In different management modes,the maximum water holding capacity and the soil permeability of the litters were the largest in D1,the maximum water holding capacity and the soil organic carbon content of the soil were the largest in D2,and the soil bulk density was the smallest;the soil-ecological hydrological function index of the soil was the largest,and the ecological hydrological function index of the M2 soil was the smallest.Middle-aged Pinus massoniana plantations with different latitudes the maximum water holding capacity,the maximum water holding capacity of the soil and the soil organic carbon content are the largest in the mid-latitude(Mz),and the soil bulk density was the smallest;the soil permeability was the least of the low-latitude(Mp).The change trend of the indexes in the young forest and the overripe forest were not consistent,and the soil-ecological hydrological function index of the young-age forest,the middle-aged forest and the overripe forest of the Pinus massoniana was the largest in the mid-latitude of different latitudes.(5)With the close-to-natural restoration of the Pinus massoniana plantations,the community recovery degree increased gradually,and the community recovery degree of Yz,Mz and Rz was 25.0%,43.3%and 52.3%,respectively,and the community recovery degree of Oz was 88.2%.In different management modes,the community recovery degree of D1and D2 was small,51.9%and 49.1%,respectively,and the recovery of M2 is the smallest,which is 37.8%,and the difference in community recovery between D1 and D2 is large.In the Pinus massoniana plantations with different latitudes,in addition to the young-age forest,the middle and overripe aged forest was the highest in middle-latitude.Bray-Curtis index recovery rate was the slowest,and the peak value was reached at 31 years;the recovery rate of the eco-exergy was centered,peaking at 28 years,and the soil-ecological hydrological function index was the fastest,the reaching its peak in 21 years.It can be seen from the logistic model that,when the 95%of the state of the potential reference system was to be restored,the simulation of the function index and the community recovery degree from the Bray-Curtis index,the eco-exergy,the soil-ecological hydrological function index and the community recovery degree was worth more than 0.95,and the time reaches 0.95 or more,respectively,was 100 years,86 years,85 years and 91 years,respectively;and the rate of recovery of each index after 120 years was very slow,and the rate was 0.1 percentage point per decade As follows,it can be considered that the community had basically returned to the frame of potential reference state at this time.