不同密度杉木林乔木层垂直空间及生态系统能量积累与分配

Energy accumulation and distribution among vertical space of tree layer and at the ecosystem level of Chinese fir forests with different stand densities

为了探究不同林分密度对杉木各个组分热值和群落能量现存量的影响,以福建省三明市福建农林大学莘口教学林场3种造林密度(1800、3000和4500株·hm-2)杉木林为对象,对杉木林生态系统各个组分热值进行测定,并结合生物量数据,研究不同造林密度杉木林生态系统各个组分热值和能量分配情况。结果表明:在垂直空间上,杉木林树干和树皮能量现存量随高度增加而减小;宿留枯枝和宿留枯叶热值随高度增加而增加,其能量现存量随高度增加表现先增后减趋势;其他组分热值和能量现存量则在不同高度上无明显一致变化规律。不同径级根上,根桩的热值和能量现存量最大,细根热值和能量现存量为最小。杉木林生态系统各个组分热值和能量现存量分配与造林密度关系密切,宿留枯枝、宿留枯叶、凋落物和树根热值随密度的增加而增大,林下植被、鲜枝和鲜叶表现为随密度的增加而减小,树干、树皮则随密度增大呈现先增后减的趋势。随着密度增加,其生态系统能量现存量呈增加趋势;3种造林密度均表现出树干能量现存量占比最大,其次是树根和树皮,其他组分能量现存量占比均低于10%。相关性分析表明:鲜叶、鲜枝、林下植被与林分密度呈显著负相关,其他各组分热值与林分密度无显著相关性。林下植被能量现存量与林分密度呈显著负相关,而宿留枯枝和凋落物与林分密度呈显著正相关,其余组分与林分密度无显著相关性。综合生态、经济和长远考虑,本试验中3000株·hm-2的密度更加有利于充分利用生物资源促进林分生长。

We explored the effects of different stand densities on calorific value in each component and the standing energy of community of Cunninghamia lanceolata under three stand densities(1800,3000 and 4500 plants·hm-2),in Xinkou Teaching Forest Farm of Fujian Agriculture and Forestry University,Sanming City,Fujian Province.The distribution of calorific value and energy in each component of ecosystem was quantified by measuring calorific value and biomass.The results showed that,on the vertical space,calorific value and the standing energy of each component of C.lanceolata changed with height,while the standing energy of the trunk and bark decreased with increasing height.The calorific value of the remaining dead branches and leaves increased with increasing height,while standing energy of the remaining dead leaves increased and then decreased with increasing height.The calorific value and standing energy of other components did not depend on height.As for the roots of different diameter-classes,the calorific value and standing energy of stump were the largest,while those of fine roots were the smallest.The distribution of calorific value in each component and the standing energy of ecosystem showed close correlation with stand densities.The calorific values of remaining dead branches,remaining dead leaves,litter and roots increased with increasing stand densities,while the opposite was true for understory vegetation,fresh branches and fresh leaves.The calorific value of trunk,bark,and remaining dead leaves first increased and then decreased with increasing stand densities.The standing energy of ecosystem exhibited an increasing tendency with increasing stand densities.As for the standing energy in different components of the ecosystem across different stand densities,trunk accounted for the largest proportion,followed by roots and barks,and the proportion of other components were all less than 10%.The calorific values of fresh leaves,branches,and understory were significantly negatively correlated with stand densities,while the calorific values of other components were not correlated with stand densities.The standing energy of understory vegetation was significantly negatively correlated with stand densities,the standing energy of remaining dead branches and litter was significantly positively correlated with stand densities,while the standing energy of other components was not correlated with stand densities.In conclusion,from the perspectives of ecology,economics and long-term development,a stand density of 3000 plants·hm-2 is the most suitable for full use of biological resources and the growth of C.lanceolata.