| The Larix principis-rupprechii plantation distributes in Saihanba Mechanical forest farm widely, plays an important role in water conservation, sand fixation, formation and maintenance of ecosystem. While, because of lack of reasonable management measure, the plantation has caused some problems, and the biodiversity decline is one of outstanding problems. For instance, the not timely tending thinning when the stand density grows higher, results in the shrubs growing poor, the herbage growing sparsely and slenderly, even death. In addition, the forest age-class and the stand condition(especially the soil physicochemical property) affect the biodiversity greatly. This paper researched on 18 plots with different age-class of Larix principis-rupprechii plantation, by means of investigated the biodiversity in different situation of stand density, age-class and soil physicochemical property, tried to find the regulation, the reasonable tending density and soil physicochemical property, promoted the biodiversity. The theoretical result could be reference for the management measure for the local forest workers. The primary result are as follows:(1)The survey area by understory there were 51 species of vascular plant belonging to 43 genera of 20 subjects. Among them, the largest proportion of seed plants, 49 species belonging to 41 genera in 18 subjects. While ferns only 2 families, 2 genera, 2 species, the proportion of less. At the same time, in seed plants, dicotyledons belonging to 43 species, belonging to 16 families, 36 genera. Monocotyledonous plants belonging to 2 families, 5 genera, 6 species, a smaller proportionl.(2) Shannon-Wiener species diversity index and species richness index H significant positive correlation exists between S(P < 0.05), there is no simple relationship with other species diversity index. Has a very significantly positive correlation between Simpson diversity index and species diversity index of D Shannon-Wiener H(P < 0.05). In addition, there was no significant correlation between H and Jsw, there is significant correlation between it and Jsi(P < 0.01). In other Jsw diversity index, Simpson diversity index and species evenness index based on Pielou Jsi were positively correlated(P < 0.01). Compared with Jsi, a positive correlation between Jsw and D was not significant(P < 0.05), while the correlation between species diversity index and the other is fuzzy. Between D and Js both were positively correlated(P < 0.01).(3) In all the effects of plant species diversity factors, reflect the stand density effect is particularly prominent, and the correlation between it and the species diversity and species richness significantly(P < 0.05), while the effect of evenness of species is not too obvious.(4)The growth of larch plantation from young forest to the mature forest, understory plants mainly Compositae and Rosaceae, Ranunculaceae plants, 20 families, 43 genera and 51 species involved. The main forest herb, Carex Geranium madder, etc.. The number of species of plantation forest gradually increased with the age increased the number; when the forest to mature forest stage, the number of species of larch plantation reached the maximum. The index of the herb layer species richness, diversity and evenness index was the largest in the young forest, the smallest in the middle age forest.(5)Analysis of the correlation between species diversity, physicochemical properties of soil and the study found that: the species richness of different ages of Larix principis rupprechtii plantation and shrub layer diversity index increases with the increase of water content, total nitrogen values; decreases with increasing the bulk density, p H value. There is a negative correlation between the herb layer species diversity index and total nitrogen, available phosphorus, available potassium, there is a significant positive correlation with p H value. |
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