| Phyllostachys edulis (Moso bamboo) is an important single axile dispersal type shoot-using species in south China. P. edulis produces high economic, social and ecological benefits with a short growth cycle and wide distribution. P. edulis in Chongyang County where is the center distribution region of P. edulis in Hubei province had been taken as research object. Statistical methods had been used to determine main factors which affected its growth, and main factors site type had been divided. Based on site type classification, the growth characteristics of P. edulis and the growth process of bamboo shoot-young bamboo was investigated and analyzed with plots in the same site type. With 4 density stands, i.e, 1300±100 stems·hm-2(D1),1900·100 stems·hm-2(D2),2500±100 stems·hm-2(D3) and 3100±100 stems·hm-2(D4), a study on the stand density effection had been carried out, and the suitable density for timber production had been determined beign high economic and ecological benefits. And some suggestion had been provided for local bamboo production and management as well. Through this research, main conclusions had been obtained as follows.With 42 plots of P. edulis forest in Chongyang, a research had been carried out into the effection of site factors on tree growth. Diameter at breast height (Y) of each plot had been taken as the dependent variable, slope direction (x,), slope position (x2), slope gradient(x3), thickness of soil humus layer (x4), soil layer thickness (x5), and parent rock types (x6) as the independent variables. Both the partial correlation analysis and stepwise regression analysis had been done. The result indicated that the dominant factor which affected the growth of P. edulis diameter at breast height were soil thickness (x5), parent rock types (x6) and slope position (x2), and the regression equation was:Y=6.332+0.358 x2+0.060 x5-0.662x6, R2=0.888.With factor analysis, the 6 site factors could been divided into 2 principal components. The first one reflected the information of edaphic factor, while the second one mainly reflected the information of terrain factor. With 42 plots site type can be divided 4 groups by means of principal component cluster analysis.The shoot stage of P. edulis in Chongyang was from late March to late April in general, such as in the year of 2014 which shoot stage was from March 25 to April 28th, lasting about 35 days. The shooting rate and the degenerated shoot rate presented as a normal distribution to shooting time, which showed the rule of "less～much～less".The height growth stage of P. edulis lasted about 45 days, which growth process fitting the Logistic model, y=1797.249/(I+118.618× 0.836x),R2=0.986.Its height growth also showed day and night rhythm, and the increment at night was about 7.6% higher than that during the day. Its ground diameter growth showed the rule of " fast～slow～fast " with a growth cycle of 25 days, about 20 days shorter than its height growth; The P. edulis growth process of shoot-young can be divided into 4 stages by using the method of Fisher:the early growth stage (1-15 days), the accelerating growth stage (16-25 days), the fast growth stage (26-33 days), the late growth stage (34-45 days).Forest density had a significant effection on bamboo shoot rate and stem rate, presenting a trend of increasing at first and then decreasing, but had no effection on the shoot degenerated rate.There was a significant difference for leaf area index among different density of stands, which increased with the increase of stand density with a range of change 3.18 to 7.1. The diameter at breast height was between 10.75 cm to 11.75 cm, and the difference had reached to extremely significant level, and the average height was between 12.96 m and 13.33 m, and the difference was not significant. Both diameter distribution and height distribution of 4 kinds density of P. edulis stand were all normal distribution.There were regressions between P. edulis growth factors, i.e, diameter at breast to height:H=2.456DBH0.686, ground diameter to diameter at breast height:DBH= 0.799D0+0.792, and ground diameter to height:H= 2.413D0.065.The biomass above ground of P. edulis was 15259.19-24951.74g, and changed with age, the order was Ⅱ degrees> Ⅲ degrees>Ⅳ degrees> I degrees. Biomass above ground and litter reserves of different density of stands were increased with stand density increasing, which differences reached a significant level.The amount of water conservation for different density of P. edulis forest was range of 584.15-626.58 t·hm-2, and the largest was D1 (626.58 t·hm-2), the second was D3(618.88t·hm-2), and the minimum was D4 (584.15 t·hm-2). The storage capacity of soil layer accounted for highest proportion (96.41%～97.91%), showing a order of forest density: D4 (563.21/t·hm-2)<D2 (583.00t·hm-2)<D3(599.27·hm-2)<D1(613.47t·hm-2).The canopy interception of P. edulis forest increased with stand density increasing, i.e, 4.97 (D1),6.75 (D2),7.81 (D3) and 8.84 (D4), respectively, which accounted for a smaller proportion of the total water conservation of forest, about 0.79%～1.51%. Litter water holding capacity increased with stand density increasing as well, which was 8.14 (D1),9.81 (D2),11.80 (D3) and 12.11 (D4), and also accounted for a smaller proportion of the total water conservation of forest, about 1.30%～2.07%.The water holding quantity of litter was increased with immersion time increasing, but the water absorption rate decreased with immersion time increasingUsing entropy method combined with bamboo indice, Chongyang of different density of P. edulis forest was divided into productivity and ecological function by means of comprehensive evaluation, the order was D4 (0.44)<D2 (0.47)<D1(0.49)< D3 (0.52). D3, i.e,2500 stems·hm2 was a suitable density of stand for good site type in Chongyang, which would bring us good economic and ecological benefits. |
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