| Reasonable stand spatial structure determines the function of forest and forest tree growth of the overall situation,studies the stand structure of rocky desertification areas,using structured index evaluated the stability of forest forest management technology and rocky desertification and the correlation of the indicators,can provide theoretical basis for scientific management of rocky desertification area plantation.In this study,a fixed sample plot of 3.5hm2 artificial mixed forest in the National Long-term Scientific Research Base for comprehensive Control of Rocky desertification in Wuling Mountain in western Hunan was selected as the research object.The stony desertification grade in the stand was comprehensively investigated and evaluated.According to four different stony desertification degree grades and stand types,reset 16 pieces of 20m × 20m standard ground.Within the standard on trees(DBH≧4 cm)to conduct a full investigation and investigating the understory plant diversity of forest stand diameter distribution,the forest stand spatial structure,forest tree species diversity,plantation stability has carried on the comprehensive analysis,discusses the wuling mountain rocky desertification area of artificial mixed forests and forest stand spatial structure stability.The conclusions are as follows:(1)The plant composition showed that the stand had developed into a mixed forest with a high species diversity index through regeneration and succession for many years.In this study,56 species of 43 genera and 26 families were found in the tree layer of the experimental stand.The main tree species were Cinnamomum Camphora,Cunninghamia Lanceolata and Camptotheca acuminata.Among the understory plants,there were 54 species belonging to 31 genera and 20 families,and the main species were Camellia Japonica,Zanthoxylum armatum and Lonicera japonica.There are 68 species of 43 genera and 23 families in the herbaceous layer,of which Cyclosorus Interruptus dominates.Other main herbs are Lysimachia Christiniae,Cyperus rotundus,Achyranthes bidentata,etc.The diversity indices(richness and Shannon index)of shrub layer and herb layer were as follows:Ⅰ(Cinnamomum camphora-Magnolia)>Ⅱ(Cinnamomum camphora-Quercus citabilis)>Ⅳ(Castanum-Cunninghamia lanceolata)>Ⅲ(Cunninghamia lanceolata),indicating that the species diversity index of broadleaved mixed forest was higher than that of Chinese fir mixed forest.(2)The diameter class distribution structure of the mixed forest showed that the stands were consistent with the diameter structure characteristics of the typical different-age forest,and the most of the stands were middle-small class,indicating that the stand was in the early and middle period of regeneration succession.In each degree of rocky desertification,the number of trees in middle diameter order was the majority.With the increase or decrease of diameter order,the number of trees decreased,and the DBH distribution of the stand was single peak.The size distribution trend of mild and moderate rocky desertification is relatively gentle,and the number of large size trees is better than that of severe rocky desertification and very severe rocky desertification.Pinus armandii Franch.Is a large-diameter tree with an average DBH of 33.4 cm,while Sloanea Hemsleyana has an average DBH of 7.3 cm,indicating that most of them are young trees.On the whole,it accords with the diameter structure characteristics of typical different-aged forest.(3)There were differences in mixing degree among different habitats and different tree species.The degree of differentiation of broad-leaved species was higher than that of conifer species,and Liriodendron chinense had the highest degree of differentiation among broad-leaved species.The mixed degree of Yulania denudata and Cinnamomum camphora mixed forest was the best,and that of Aphananthe aspera mixed forest was the worst.The angular scale of the 16 standard plots was mainly distributed in clumps,and the openness was mainly concentrated in sufficient,insufficient and basically sufficient states.The growth space of Broussonetia papyrifera,Camphor camphora,and Magnolia-Camphora mixed forest was sufficient.There was some competitive pressure in the plots where the main tree species were chestnut imitation.(4)Analysis of stand spatial structure showed that there were significant correlations between the degree of rocky desertification,competition index and individual tree size.The spatial structure of the stand was significant,and the size ratio was significantly positively correlated with the competition index,openness,and average DBH with average tree height(P<0.05),indicating that the greater the individual size difference between trees,the less the competition pressure was,and the larger DBH and tree height were,the more space the trees had for growth.There were significant negative correlations(P<0.05)between angular scale and openness,openness and competition index,between rocky desertification degree and average DBH,and between rocky desertification degree and average tree height,which indicated that with the increase of rocky desertification degree,the growth of trees was more inhibited,resulting in tree dwarf and disadvantage.(5)The analysis of stand stability showed that the severity of rocky desertification affected the stand stability.In this paper,FSSI and FSSD were used to evaluate the stand stability of 16 standard plots.The results showed that the stability of the stand was relatively good in mild and moderate rocky desertification habitats,while the stability of the stand was relatively moderate in severe and very severe rocky desertification habitats.There was no better or worse stand in the 16 standard plots,but there was still a certain gap between them and the ideal stand spatial structure.The stand dominated by the mixture of Magnolia,Cinnamomum camphora and Cyclobalanopsis glauca had a relatively good spatial structure,while the stand dominated by the mixture of Cunninghamia lanceolata and chestnut had a relatively moderate spatial structure. |
PDF Full Text Request