| As an important component in forest ecosystems, the forest biomass which approximately composes 90% of the global land vegetation biomass is an important symbol of the carbon sequestration. It is also an important parameter of appraising the forest carbon revenue and expenditure. The magnitude of forest biomass is affected by the human activity and nature factors such as respiration, photosynthesis, harvests, death, and so on. Therefore, the change of forest biomass reflects the humanity activity, the forest succession, nature molestation (for example:forest fire, the plant disease and so on), air pollution and climatic change. All of these are important indices to measure the forest structure and the function change.This paper did an investigation about the forests biomass and the biomass allocation of the 4 different subtropical forests which with similar site conditions in hilly area of Dashanchong Forest Park in central Hunan province, China. They are Cunninghamla lanceolata plantation (CL), Pinus massoniana-Lithocarpus glaber mixed coniferous forest (PM), Choerospondias axillaris deciduous forest (CA) and Lithocarpus glaber-Cyclobalanopsis glauca evergreen broadleaved forest (LG). We set an 1 hm 2 sample plot in the 4 subtropical forests respectively. The DBH and height of the trees which are DBH>4 cm were measured by using quadrate sampling and field measurement methods. The biomass of the 4 subtropical forests and the organ biomass of the 4 subtropical forests was calculated by the allometric method. The further relative research were about stand biomass and organ allocation in the four forests, the relationship between biomass in crown (branches and leaves) and stem of the four forests and the relationship between aboveground biomass and belowground biomass in the four forests. At the last part, we did an analysis on the species diversity index of the four forests. The main results are as following:(1) The results showed that stand biomass was significant different among the four forests (p<0.01), with the highest value for PM (154.03 t·hm-2), the lowest for CL (72.74 t·hm-2), and the intermediate for LG (134.08 t·hm-2) and CA (106.89 t·hm-2). The order of per tree was ranked as CL(120.58 kg)>LG(78.05 kg)>CA(72.99 kg)>PM(62.21 kg).(2) To make the research results more clearly, the data of the 4 subtropical forests that got through standard sample-plot investigation was analysed by divided the 4 sample plots into 10m 10m small plots respectively. Calculated the mean value and standard deviation of the organs of the 4 subtropical forests at first. The results showed that there was significant different among the four forests in stand biomass and biomass allocation(p<0.01). The order of the organs biomass in the four forests was ranked as stem>root>branch>leaf. The stem biomass of CL, PM, CA and LG was accounted for 72.38%,63.38%,60.56% and 59.99% of the whole forest respectively. The root biomass was accounted for 16.57%,17.09%,18.43% and 18.41%. The branch biomass was accounted for 6.51%,15.35%,17.49% and 17.31%. The leaf biomass was accounted for 4.53%,4.18%,3.54% and 4.30%. The organs biomass allocation in the 4 subtropical forests had no significant differences. The order of the stem biomass, branch biomass, leaf biomass and root biomass of the 4 subtropical forests was was same as PM>LG>CA>CL.(3) Took the stem biomass of the 4 subtropical forests as the variables to fit the crown biomass, the result showed that the crown biomass increased at different rate as the stem biomass increased. There were significant linear positive correlations between the crown biomass and the stem biomass of the 4 subtropical forests. The regression equation of CL established by them was y=0.2765x-6.5202; The regression model of PM was y=0.3342x-2.5422; The regression equation of CA was y=0.3422x+0.3257; The regression equation of LG was y=0.3345x+2.071. The correlation of determination of the CL was 0.7539, the PM was 0.8183, the CA was 0.9894, the LG was 0.9406. It is obviously that there is a high linear correlation between the stem biomass and the crown biomass. The regression model constructed by the stem biomass can estimate the crown biomass (75%-98%) when only stem biomass is available.(4)The results showed that the aboveground biomass is much more higher than the belowground biomass. The aboveground biomass of CL, PM, CA and LG were 37.62 t·hm-2,127.70 t·hm-2,87.76 t·hm-2 and 100.74 t·hm-2, accounted for 83.43%, 82.91%,84.35% and 81.59% of the whole forest respectively. The belowground biomass of the 4 subtropical forest were 7.47 t·hm-2,26.33 t·hm-2,19.82 t·hm-2 and 22.72 t·hm-2, accounted for 16.57%,17.09%,18.42% and 18.43% of the whole forest respectively. Took the aboveground biomass of the 4 subtropical forests as the variables to fit the belowground biomass, the scatter diagram drew by the aboveground and belowground biomass of the 4 subtropical forests showed clearly that the linear correlation between them were high. The regression model of CL was y=0.2711x-1.1579, (r2=0.97). The regression model of PM was y=0.2232x-2.1752, (r2=0.9392). The regression model of CA was y=0.2125x+1.1714, (r2=0.9933). The regression model of LG was y=0.2148x+1.177, (r2=0.9858). They showed that the regression model constructed by the aboveground biomass can estimated the belowground biomass 97%-99% when the aboveground biomass available.(5) Choose the top five dominant species that stems with diameter at breast height (DBH) greater than or equal to 4 cm in the 1 hectare plot of the three subtropical forests depend the formula that Important value(IV)=Relative frequency+Relative BA+Relative density. After the relative analyses between the dominant species biomass and forest biomass, the results shows that the significance of CA on the forest biomass>PM>LG. The result of regression analysis between the domiant species of PM, CA, LG and their stem number, Basal area(BA) and IV shows that the BA had the biggest significance on the dominant species, the IV take the second place, the stem number show the smallest significance on the dominant species biomass. |
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