| Artificial close-to-nature mixed forestry was a kind of multifunctional and high efficiency sustainable management.It was aiming at the problems of current plantation management,based on the close-to-nature management theory,through replanting native hardwood species to adjust the single-structure pure forest,built more forest layer,different ages,multi-species of mixed forest,developing multifunction benefits of artificial forest.This study chose Pinus massoniana conifer-braodleaved mixed plantation as object in tropical forestry experiment center of Chinese academy of forestry,analysised the transformation effect and competitive strength of Pinus massoniana artificial forest,characteristics of canopy factor in different stand age,and niche characteristics and interspecific relationships of dominant tree species.It was concluded stand structure,growth dynamics and interspecific relationships of Pinus massoniana coniferbraodleaved mixed plantation,designed two silvicultural regimes for the artificial close-to nature management.It could provide operation parameters and technical support for the sustainable multifunction forest management in subtropical of China.The main conclusions in this paper are as follows:(1)The transformation of Pinus massoniana artificial forest had obtain remarkable effect.Through comparative analysing stand structure of five kinds of close-to nature transformation forest,we knew that selective cutting and complementing could enrich forest species diversity and improve stand quality in the short term,as the complementing trees species gradually into the main forest layer,as well as the mutual growth mechanism between tree species,could guide the forest to multiple layers,uneven-aged,and tree species mixed close-to-nature forest,and provided reference for multi-function forest management in China.After eight years operation in pinus massoniana plantation,mixed forest had shown obvious advantages in species compositoin,stand structure,species diversity and stand growth compared with pure forest.In the short-term effect of operation,A2 forest stand had the highest growth rate,lowest mortality of complementing trees,highest tree volume growth,had the most obvious effect transformation,was the optimal transformation model in the short term.A4 transformation modle had the most implementing tree species,at higher altitudes,poorer site conditions.With the improvement of site conditions by broad leaved tree species and the effect of implementing,it was expected the optimal transformation modle in poor stand conditions,played the largest forest potential productivity.(2)Through analysing the interspecific competition relationships of Pinus massoniana clsoe-to-nature transformation forest,could provide technical parameters for designing silvicultural regimes.P.massoniana in pure forest competition indices were greater than in the mixed forest.Through effective cutting wood and reasonable implementing,could effectively reduce the pressure of competition of masson pine.Masson pine pure forest only existed intraspecific competition.Pinus massoniana interspecific competition indices in the mixed forests was greater than in the pure forest.The intraspecific competition of pinus massoniana was significant difference in mixed forest and pure forest,and the average competition indices of mixed forest were less than the pure forest in different classes.Fast-growing tree species Quercus griffithii and Manglietia glauca produced interspecific competition pressure firstly to Pinus massoniana.The competition index of pinus massoniana was decreased gradually with the increase of at breast diameter height,when the diameter more than 25 cm,the competitive pressures of pinus massoniana were gradually reduce in mixed forest and pure forest;when less than 25 cm,the competitive pressures of pinus massoniana was greater.(3)By studying the canopy factors of artificial P.massoniana forest in different stand age stage,could directly reflect the competitive ability and the growth space of tree species,and provide reliable parameters for the forest management.We knew that the crown mainly distributed in 1.0-3.0m,it was increased with age of forest;ratio of crown length is mainly distributed between 0.2 to 0.6,it was decreased with age of forest.The variation coefficien of crown and ratio of crown were significantly larger in mature forest and over-mature forest,the crown and crown length of strong vitality tree species were stronger.The poor vitality tree species were easily broken by the affect of cutting and typhoon.It had smaller crown and higher under branch height.The crown with diameter at breast height showed significant linear relationship,and the ratio of crown length with under branch heightn and tree heigh s showed significant linear relationship.We established multivariate linear model with tree size,competition,site conditions factors as variables,improved the accuracy of model,and suggested that the crown and crown length ratio of P.massoniana were affected by factors in different age stage varying.In order to improve the prediction precision and usability of model,based on the multivariate linear model model,we established the crown and crown length ratio of P.massoniana linear mixed effects model.Its precision(R2)reached 0.72 and 0.987 respectively.(4)Based on analysising the niche and interspecific relationships of dominant species in study area,could reveal the distribution,environment adaptability and the relationship.The important value and niche width of 30 species were positively correlated.As the main plantation tree species,P.massoniana and Cunninghamia lanceolata was advantage obviously in this area,had strong ecological adaptability,the biggest important values and niche width.In addition,the fast-growing tree species had the greater niche width with natural regeneration ability and environment adaptation.The ecological overlap between tree species were smaller.It shows that they had weaker competition for resources in plantation community.The community structure was stability.The advantage tree species was significantly positive correlation.The positive were more than negative correlation,for many kinds of connection of species pairs were neutral and independence.It suggested that the community had certain stability.At the same time,the test results showed that the ratio of positive and negative correlation was less than 1,the community was in the early succession stage.P.massoniana and Cunninghamia lanceolata had obvious advantages and less generation in community.We used two-way indicator species analysising method to classify 131 sample plots and 30 dominant species.The 30 dominant species preliminary can be classified into 5 vegetation types,12 species types.The 131 sample plots were divided into 21 groups.(5)According the connotation of silvicultural regime,seven silvicultural plantation systems for different forest types and four technology elements which must be designed,the Pinus massoniana silvicultrural regimes was proposed.Based on the above analysis results,we designed two silvicultural regime cases for Pinus massoniana forest types in this area: clear cutting silvicultural regime in mixed broadleaf-conifer relative even-age forest and target-tree selective cutting silvicultural regime for guiding to hard of uneven-age broadleaf forest.According to the different growth characteristics of Pinus massoniana and Quercus griffithii,we designed clear cutting silvicultural regime,compared with the traditional clear cutting operation,could effectively improve the stand quality and obtain high quality forest products.Using different growth regularity of tree species and characteristics of forest succession,we designed operation of guiding conifer-broadleavede relative even-age forest to uneven-age broadleaf forest,could continuously provide economic wood products and cultivate the next generation of target tree species.It was a long-term lasting forest management to maintain the stability of forest stand and regeneration capabilities.It was a worthy implementation scheme for forest management unit.The design ideas and examples of silvicutural regime in this paper,could be extended to most region in our country which was artificial coniferous forest management,and provide application case and the technical reference for multi-function forest management in China. |
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