| Chinese fir is a special fast-growing timber species in South China,which plays an important role in plantation production.As one of the variation types of Chinese fir,the red-heart Chinese fir has good material quality,high rate of heartwood,and high commercial value.Therefore,more and more attention has been paid to the development and protection of red-heart Chinese fir.In this study,9,15,26 and 34-year-old red-heart Chinese fir plantations in Chenshan forest farm of Anfu county,Jiangxi province were taken as the research object,sample plot survey biomass and plant tissue calorific value were combined to investigate the calorific value dynamic changes of tree layer,undergrowth vegetation,litter.The dynamic changes of calorific value,energy storage,accumulation and distribution of plant tissues in tree layer,understory vegetation layer and litter layer of red-heart Chinese fir plantation at different stand ages were studied.The following conclusions were drawn:(1)Accumulation and distribution of biomass:? Biomass of per red-heart Chinese fir increased with the increase of stand age,and the proportion of stem wood was the highest(40.02%-60.25%).The biomass of root could be listed as:stump>coarse>medium>fine.? The biomass of tree layer at four stand age were:stem wood>root>bark>branch>leaves,the biomass of sapwood was always greater than that of heartwood.The biomass of the undergrowth vegetations at different stand ages were 4.39,4.41,4.43 and 2.92 t/hm2,respectively.The biomass of shrub layer was higher than that of herb layer,both of which declined with the growth of forest age.The biomass of aboveground part of the shrub layer was higher than that of the underground part.In the herb layer,in the 26 and 34-year,the biomass was higher of aboveground part than the above-ground part.The biomass of litter layer increased with the stand age,and the order of litters was:undecomposed>semi-decomposed>decomposed.?The total biomass of stand at four stand age was 61.69,123.41,167.3 8 and 197.22 t/hm2,respectively.(2)Dynamic change of calorific value:?The calorific value of each organ of the red-heart Chinese fir increased with the growth of the stand age,and the ash-free calorific value of each organ was in the order of leaf>stem wood>root>branch>bark;There were differences in the ash-free calorific value among organs of the same stand age,but the difference between stem wood and other organs was not significant(P>0.05).The heartwood of the stem wood was higher than sapwood,and the ash-free calorific value at the vertical order of the stem wood was the upper>the middle>the lower.The ash-free calorific values of leaves or branch in different stand age was different,but not significant(P>0.05).?The ash-free calorific value of each organ in the tree layer was greater than that of each component in undergrowth vegetation.The ash-free calorific value of the shrub layer was higher than that of the herb layer;the ash-free calorific value of the aboveground part of the living ground layer was greater than that of the underground part.The ash-free calorific value in undergrowth vegetation layer decreased with the increase of stand age.The order of ash-free calorific values of litters layer was:decomposed>semi-decomposed>undecomposed.The ash-free calorific value of litters increased with the increase of stand age.? The calorific value was influenced by the stand age,the organ,the tree trunk with different longitudinal height and different radial position,and stand age was the main influencing factor.The dynamic change of ash-free caloric value of red Chinese fir with stand age was related to the increase of organ lignification degree with the increase of stand age,as well as different years of rainfall,temperature,environmental factors;in this study,the relationship between ash content and calorific value was not close,which was not the main reason affecting calorific value.(3)Accumulation and distribution of energy:? The energy of per red-heart Chinese fir increased with the growth of stand age,and the order of root energy was 10.30,22.67,30.18 and 36.31 x 108 kJ/hm2in different stand age,respectively.? The energy of tree layer was stem wood>root>bark>branch>leaves,sapwood was higher than heartwood.? The total amount of energy in undergrowth vegetation was 0.83,0.83,0.82 and 0.45 x 108 kJ/hm2 in different stand age,respectively.The energy in the shrub layer was higher than that in the herb layer,and the aboveground part of the shrub layer was significantly higher than that in the underground part.However,except for the 9-year-old stand age,the energy of the herb of the underground part were higher than the above-ground part.?The energy of litters layer of red-heart Chinese fir was higher than that of other litters layer,all of which show undecomposed>semi-decomposed>decomposed,and the energy of litters layer increased with the increase of stand age.The energy level of different levels of stands was related to the light resources.The results of this study provided basic data for the study of energy flow in the plantation ecosystem of red-heart Chinese fir,thus providing theoretical support for the forest cultivation and sustainable management of redwood trees,as well as theoretical guidance for the development and utilization of the plantation forests of redwood trees,giving full play to their ecological and economic benefits. |
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