| Choerospondias axillaries is a fine tree of speedy-growth and high-yield, which can use as ecolomic or timber forest because it has high medicine and edible value and favourable material quality. At present, Choerospondias axillaries is exerting important effect in withdrawing infield, vegetation and developing country ecolomy in west exploitation expect that has natural forest and man-made forest in south of china, so it's forground is very well. Tree root system can reflect exchange capability of substance and energy between soil and plant, moreover, can show some basic character about forest ecological system. Especially fine roots cycle quickly, fine roots'death is a major route that nutrition flow to soil, which may accelerate substance cycling and reform soil fertility etc. It is important value to afforestation and study on forest ecological system that we understand connection between forest root and some factors.Five different afforestations modes of Choerospondias axillaries were regarded as investigated object in research. Base on tree scale, root system was investigated by digging all roots, and characters of biomass, fine root, root range, root type, and root distribution etc were studied through a series of mathematical models. So it could provide theory for Cryptomeria fortunei plantation and study in the future and so on.The results of root biomass show that the same law exist in among five different type forests: coarse root>stake>middle root>fine root. Furthermore, the velocity of biomass of stake and coarse root growth will accelerate, so that rate of fine root will descend gradually. Rate of fine root of forest A and B are higher than that of C, D and E, which is the same as commonly law of root system biomass ditribution. On the whole, the rate of fine root is very small in root system, but fine root acts as a very important role in life activity of plant. Distribution of root biomass descends rapidly along with increasing of soil depth. For example, the most content of fine root is only 4.119% from 30 cm to 40 cm, which show that a majority of root biomass concentrates in frontal three layers. Anciently studies also indicate that density, surface area and biomass of fine root will descend with adding of soil depth, though tree root systems have distribution characters and possess correspond ecological niches themselves. Fractal theory interpret that essence chatacter and movement rule between part and integer backside natural phenomenon. Base on theory of conform biology, resembler exist in among many life-forms, so may forecast that foreground is fairly well if Fractal theory is applied for life sciences. Configuration of root system express a anomalistic geometric object. The geometric object exhibit self-similitude and Fractal character, which is a inherent law of root system frame, it will provide new measure and method for root character describing, So the fractal theory is applied to study on root system frame of Choerospondias axillaries.Dimensions of diameter ditribution were achieved through regression of Fractal models. Dimensions ditribute from 1.3148 to 2.0814, and correlation reaches the Significance level of 0.01. In addition, dimension will low if fine root (0~1 mm) rate of forest is low. Fractal dimension is a parameter that can reflect geometrical form, in general, dimension will increase with adding of fine root rate. Dimension of content reveals that fine root effect on plant growth. The results show that remarkable relationships exsit between dimension and tree hight, DBH through regression. What's more, relation reach markable degree between upground root system biomass and high, DBH.In all models of root extent and DBH, tree hight, the best model is Cr = aH D . Thebetter model always could be found in single factor models between root extent and DBH, tree hight. moreover, all coefficient exceeds 0.9.Fine root is major organism that tree absorb in moisture and nutrient. Percent of fine root (O-innn) accounts for from 0.177 to 1.123, percent of fine root (l~2n...
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