| Pinus tabuliformis has the characteristics of strong adaptability.It is the main tree species for aerial seeding afforestation in northern China.As the largest aerial seeding forest area in North China,Pinus tabuliformis aerial seeding forest in Danfeng County has made great contributions to local soil and water conservation,climate regulation and water conservation,and greatly improved the local ecological environment.However,due to the single aerial seeding tree species and backward management,the phenomenon of weak growth,slow growth and uneven distribution of individual-tree began to appear in the aerial seeding forest of Pinus tabuliformis.Therefore,this study regard Pinus tabuliformis aerial seeding forest in Danfeng County as the research object,establishes 20 standard plots with 4site conditions for investigation,and studies the stand structure and biomass on arbors,shrubs and herbs,clarified the distribution law of DBH and tree height of Pinus tabuliformis aerial seeding forest in Danfeng County,and established the diameter-height model,Based on the spatial structure units of four adjacent trees,analysis the distribution characteristics of uniform angle index,crowding index,mingling index,dominance index,opening index and stand layer index.The relationship between stand structure and aboveground biomass on arbors,shrubs and herbs was explored by using grey correlation analysis,multiple regression analysis and principal component regression analysis.In order to provide a theoretical basis for the structural regulation and scientific management of Pinus tabuliformis aerial seeding forest in Danfeng County.The main conclusions are as follows:(1)Due to the existence of a large number of small-diameter trees species in Pinus tabuliformis aerial seeding forest in Danfeng County,the DBH of the stand generally presents an inverted "J" distribution,and the tree height is distributed in a double peak shape.The DBH and tree height of the dominant species of Pinus tabuliformis in Danfeng County are approximately normal distribution and normal distribution respectively.The structure of the stand diameter and tree height is unreasonable,there are many young trees under the forest and their growth is poor.It is suggested to strengthen management.Variation rule of stand diameter and tree height under different site conditions: due to density constraints,the diameter and tree height of sunny slope are greater than those of shady slope,and the diameter and tree height decrease with the increase of slope gradient;Logarithmic function model can better reflect the relationship between DBH and tree height of Pinus tabuliformis aerial seeding forest in Danfeng County.(2)The spatial structure characteristics of different site conditions(Sunny steep slope,Shady steep slope,Sunny sheer slope and Shady sheer slope)of Pinus tabuliformis aerial seeding forest in Danfeng County: in the horizontal direction,the distribution pattern of trees on sunny steep slope is cluster distribution,and the distribution pattern of trees on other site conditions are random distribution;the differentiation degree of trees is low,the trees on the sunny sheer slope are in the inferior growth state,and the trees other site conditions are in the moderate growth state;The average mingling index of stand is 0.470,the trees on the shady steep slope and the shady sheer slope were mixed intensively,and the trees on the sunny steep slope and the sunny sheer slope were mixed weakly and moderately respectively;the average stand crowding index is 0.947,and the canopy under different site conditions is very dense.In the vertical direction,the sunlight under the stand on the sunny steep slope is seriously insufficient,and the forest layer structure is simple.The stand on other site conditions are insufficient sunlight under the forest and the forest layer structure is relatively simple.In the future,forest management needs to focus on strengthening the tending measures on the sunny slope,so as to make the stand develop towards random distribution,dominant growth,high mixing and more complex forest layer structure.(3)The aboveground biomass of Pinus tabuliformis aerial seeding forest,arbors,shrubs and herbs in Danfeng County is low.The distribution status of different site conditions is as follows: the aboveground biomass of arbors is the sunny Steep slope > Shady steep slope >Sunny sheer slope > Shady sheer slope,the aboveground biomass of shrubs is the Shady steep slope > Sunny sheer slope > Shady sheer slope > Sunny steep slope,and the aboveground biomass of herbs is the Sunny sheer slope > Shady sheer slope > Shady steep slope > Sunny steep slope.(4)The methods of grey correlation analysis,multiple regression analysis and principal component regression analysis are highly consistent in the research results of stand structure and biomass on arbors,shrubs and herbs,The comprehensive analysis shows that tree height,DBH and stand layer index are stand structure factor that mainly affects the aboveground biomass of arbors;and DBH,opening index and stand layer index are stand structure factor that mainly affects the aboveground biomass of shrubs;dominance index and stand layer index are stand structure factor that mainly affects the aboveground biomass of herbs. |
