Study On Hardwood Species Distribution Patterns And Influencing Factors Of Secondary Forests In Hilly Red Soil Region Of Hunan Province

The protection of natural forests and the precision improvement of forest quality are the major needs of the current national ecological security and the development direction and tasks of forestry in the new era.The low quality of secondary forest is a prominent problem of forest resources in China.How to improve the quality of secondary forests and the production of high-quality wood has become a scientific problem urgently needed to be solved in forestry.Hardwood species are the main target of cultivating high-quality wood in secondary forests.Studying its species composition,community structure,spatial pattern and its influencing factors can provide scientific basis for the strategy of combining vegetation restoration with hardwood resource reserve.In this paper,cataloguing and grasping the resources and characteristics of hardwood species in the region,taking the secondary forest in the red soil region of Hunan hills as the research object,using random sampling method,based on the data of 10 plots with an area of 1 hm2 typical in typical hilly red soil region,systematic research was carried out:(1)Population structure of hardwood resources in secondary forests;(2)Spatial distribution pattern and association of hardwood species;(3)Main extcernal factors determining hardwood species structure in secondary forests.The main results are as follows:(1)There are 43 hardwood species belonging to 9 families and 23 genera in the hilly red soil region of Hunan Province.Most species have the biological and ecological characteristics of wide adaptability,strong germination ability,medium and slow growth rate,hard and dense wood and beautiful color,Fagaceae,Ulmaceae,Rosaceae and Lauraceae are the most abundant families with 30 species,accounting for 69.77%.The deciduous species(25 species,58.14%)were more than evergreen species(18 species,41.86%),reflecting obvious floristic characteristics of subtropical plants.In terms of distribution and resource quantity,Lithocarpus glaber,Cyclobalanopsis glauca,Castanopsis sclerophylla,Cinnamomum camphora and Choerospondias axillari.s have the most advantages.The second are Dalbergia hupeana,Quercus fabri and Photinia davidsoniae,while Ormosia henryi and Pyrus calleryana are rare.(2)In secondary forests,the number of evergreen hardwood individuals(83.72%)was significantly higher than that of deciduous hardwood individuals(16.38%),was the main hardwood resource(DBH(>3 cm).Fagaceae plants account for 30.77%,41.18%and 77.29%of the genera,species and individual tree numbers of hardwood species,respectively.They are the main components of hardwood resources.Hardwood species and dominant hardwood species(relative abundance greater than 10%)in different stands shoxwed 4-11 species/hm2 and 1-5 species/hm2 composition patterns,345-1414 species/hm2 and 226-1270 species/hm2 density variation patterns,respectively.The dominant hardwood species in the community were Lithocarpus glaber,Cyclobalanopsis glauca,Castanopsis sclerophylla,C.carle.sii,Cinnamomum camphora,Choerospondias axillaris,Quercus fabrid,Dalbergia hupeana and Photinia bodinieri.The DBH structure of hardwood species in most secondary forests showed a skewed pattern with growth pattern,but the regeneration of young trees was insufficient.A few hardwood species in secondary forests showed "L-type" or inverted "J-type" structure.Different hardwood species showed distinct differences in DBH structure.Lithocarpus glaber,Cyclobalanopsis glauca,Quercus fabrid,Dalbergia hupeana and Photinia bodinieri were growth-type populations,among them,Lithocarpus glaber might have insufficient regeneration of young trees,while Cinnamomum camphora,Castanopsis scle,rophylla,C.carlesii,and Choerospondias axillaris showed declining populations.(3)Individuals and populations of hardwood species in secondary forests are clustered at all scales.In all growth stages,the abundant hardwoods are mainly aggregated or tend to be randomly distributed on a large scale,while the few hardwoods show random or not obvious aggregated distribution.The hardwood species are mainly spatially independent of each other.The characteristics of tree species,regeneration strategies and habitat heterogeneity may be the main reasons for the aggregation and distribution of hardwood species.(4)Topography,soil and disturbance history factors have great influence on the composition and structure of hardwood species,which can explain 46.88%of the variation.Their coefficient of variation is between 0.16 and 2.06.Pure topographic factors(interpretation rate 21.35%)explained more spatial variability of hardwood species than pure soil(15.25%)and pure disturbance history(4.73%).Slope direction and soil stone content are the most important topographic and soil factors.The deterministic processes related to niche differentiation and stochastic processes related to diffusion constraints together determine the distribution pattern of hardwood species resources in secondary forests.In a word,the species,quantity and spatial distribution of hardwood in secondary forests in hilly red soil region of Hunan Province are obviously uneven,and the structure is not very reasonable.In order to speed up the vegetation restoration of secondary forests and cultivate high-quality timber,human intervention is needed.