| Forest structure index is a comprehensive evaluation of the stability of the stand, play an important role in the protection and management of natural forests; stand structure impact on understory vegetation diversity is a key factor in maintaining the stability of forest eco-sy stems. Pinus yunnanensis var. tenuifolia is a species endemic to China, Pinus yunnanensis var. tenuifolia Natural limiting environmental factors, their range is narrow, and because of damage to the ecology and not appropriate management measures, resulting in natural forests of Pinus yunnanensis var. tenuifolia grouped into simple, stand stability decreases, poor forest quality, eco-efficiency decline. How reasonable human disturbance, forest structure adjustment, improve forest quality and forest productivity, production capabilities and eco-efficiency, coordinated and sustainable development, Pinus yunnanensis var. tenuifolia is an urgent need to solve business problems. In this study, Yachang national nature reserves Pinus yunnanensis var. tenuifolia natural forest for the study, based on a TaZha method, choose without artificial interference, similar site conditions stand, set of large 100m × 100m Likewise, set 25 20m × 20m demo in large plots. All live tree in the survey plots (DBH>5cm), Species saplings, seedlings, tree height (height), DBH (diameter), crown, with total station positioning three-dimensional coordinates of each plant (x, y, z); survey herbaceous layer using the diagonal method set 125 1m × 1m quadrats and investigate all kinds of name was, number of trees, cover, abundance, average height, frequency, etc., were non-spatial stand structure, spatial structure and diversity of understory vegetation, main contents and conclusions are as follows:1. Stand Structure. Stand Structure analysis included studies non-spatial and spatial structures, non-spatial structure research stumpage diameter and tree height, spatial structure analysis of the whole plot in live trees, small trees (DBH <20cm), big trees (DBH> 20cm) Angle index, Dominance, Minglings. mono-distribution and bivariate distribution. The results show:(1) Skewness coefficient diameter structure, kurtosis are positive. Diameter distribution curve left side, small-diameter trees in more bands, more concentrated; the average diameter of Pinns yunnanensis var. tenuifolia is dominated by the large diameter class bias, lack of forest seedling regeneration, normal distribution, Weibull distribution function fitting effect is significant.6 large main associated tree species Quercus variabilis、Cyclobalanopsis delavayi* Keteleeria davidiana、Eurya distichophylla、Lyonia ovalifolia、Betula alnoides diameter distribution with a logarithmic normal distribution and Weibull distribution function fit most significant effect in favor of species update, trail order saplings, seedlings more.(2) Tree height distribution curve left side, tend saplings, distribution is discrete; Pinus yunnanensis var. tenuifolia tree height also dominant tree height distribution curve fitting of three distribution function was significant. Pinus yunnanensis var. tenuifolia high profile biased high trees, saplings distributed less; six main associated tree species saplings distributed more.(3) Full plot stumpage Angle index, Dominance, Minglings. mono-distribution and bivariate distribution showed:Pinus yunnanensis var. tenuifolia natural forest most living trees in mixed and random distribution; different pros and cons situation of stumpage associated with most other species; stumpage four weeks randomly distributed generally have other species; most of the merits of the different situation of live trees in a random distribution. Overall in random distribution,the state of moderation, moderate mixed, the spatial structure of the natural forests in a stable state, conducive to the development community.(4) The small trees (DBH<20cm) Angle index, Dominance, Minglings. mono-distribution and bivariate distribution showed:Likewise, all of the trees in the overall random distribution, moderation status, moderate mixed, indicating that the natural forest stands of trees in a steady state, the number of trees in an absolutely dominant position, in favor of natural forests updates.(5) The big trees (DBH>20cm) Angle index, Dominance, Minglings. mono-distribution and bivariate distribution showed:All the big trees in the overall random distribution, an absolutely dominant position, highly mixed state, indicating that the growth of trees in an absolutely dominant position. The main big trees of Pinus yunnanensis var. tenuifolia. Pinus yunnanensis var. tenuifolia Natural Forest Community structural stability.2. Understory vegetation diversity analysis. Overall understory plant species, Important values, Species richness (S), Simpson diversity index (D), Shannon-Wiener diversity index (H), based on Simpson index evenness index (JD), based Shannon-Wiener index of evenness index (JH) calculated results show that:(1) Pinus yunnanensis var. tenuifolia Natural Forest vertical structure significantly, the number of plant species exhibit:shrub layer> tree layer> herb layer. Arbor layer and shrub layer, a total of 22 plant species belonging to 16 families and 20 genera. Herb layer 5 species belonging to 4 families,5 genera. Tree layer mainly Pinaceae and Fagaceae species as the dominant species; shrub layer mainly Fagaceae, Ericaceae species as the dominant species; herb layer Gramineae, Gleicheniaceae species were the dominant species.(2) Pinus yunnanensis var. tenuifolia Natural Forest vegetation before each shrub layer species important value rankings followed by 3 Lyonia ovalifolia, Quercus variabilis, Cyclobalanopsis delavayi. The herb layer species importance value of each layer the top three followed Dicranopteris dichotoma, Pogonatherum crinitum, Miscanthus floridulus. Pinus yunnanensis var. tenuifolia Natural Forest plot for each species diversity index the shrub layer was higher than herb layer.(3) Different slope positions of diversity indices, with the rising slope position, the shrub layer species richness index showed a decreasing state. Herb layer first decreasing and then increments status. Simpson diversity index of shrub layer in different slope positions the first decreasing and then trend of recovery, no law herbaceous layer. Shrub layer Shannon-Wiener diversity index the first decreasing and then trend of recovery, herb layer no law. Shrub, herb-based index of Simpson evenness index with no significant change in slope position of the law. Evenness index based on Shannon-Wiener index no obvious regularity. |
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