基于年轮分析的不同恢复途径下森林乔木层生物量和蓄积量的动态变化

Dynamics of stand biomass and volume of the tree layer in forests with different restoration approaches based on tree-ring analysis

基于树木年轮学与标准地调查法,研究了川西亚高山林区3种恢复森林类型生物量、蓄积量及生产力动态变化特征,旨在尝试年轮学在森林生长过程反演中的运用,并探索不同恢复模式下森林生物量和蓄积量的动态变化。结果表明,不同恢复类型发育至20年以后,均进入生长加速期,平均胸径间差异逐渐显著,人工云杉(Picea asperata)林胸径增长最快,明显高于天然恢复的次生桦木(Betula spp.)林和次生针阔混交林。在恢复过程中,次生针阔混交林一直保持最高的林分平均地上生物量与林分蓄积量,其地上平均生物量一直显著高于人工云杉林(p<0.05),在20年以后显著高于次生桦木林(p<0.05)。与人工云杉林相比,次生桦木林在25年前具有相对较高的生物量,而在25年之后则低于人工云杉林。在0-20年桦木林林分蓄积量略高于云杉林,而20年以后,云杉林蓄积量则超过桦木林。不同恢复类型的生产力大小对比显示,30年之前,次生针阔混交林>次生桦木林>人工云杉林,30年之后,针阔混交林生产力仍然最高,而人工云杉林则超过次生桦木林。川西林区次生针阔混交林恢复模式在生物量和蓄积量积累方面均具有显著优势。

Aims Our objectives were to （a） explore potential applications of tree-ring analysis for evaluating biomass dynamics of different forest restoration approaches in Western Sichuan, （b） compare aboveground biomass and stem volume with differently restored forests, and （c） identify the appropriate management approaches for different management aims. Methods We intensively surveyed three replicated plots for each restoration approach and cored and measured all living trees with diameter at breast height （DBH） ≥ 5 cm using dendroecological methods. Dynamics of aboveground biomass and stem volume were calculated by means of allometric relationships and one-way tree volume models based on continuous variation of DBH. Important findings Forests in all three restoration approaches entered into an accelerated growth phase after 20 years, when significant differences in average DBH were observed among different forest types. Planted spruce （Picea asperata） forest （PSF） showed faster growth in mean DBH than secondary birch （Betula spp.） forest （SBF） and secondary coniferous and broad-leaved mixed forest （SMF）. In the process of recovery, SMF had the highest aboveground biomass and stand volume; its biomass was significant higher than that of PSF （p 〈 0.05） throughout and higher than SBF after 20 years. SBF had a higher aboveground biomass compared with that for PSF during 1-25 years and a lower value after 25 years. Before 20 years, the stand volume of SBF was higher than that of PSF, but PSF had higher volume after 20 years. Before 30 years, the aboveground net primary productivity for three forest types ranked SMF〉SBF〉PSF. After 30 years, the order changed to SMF〉PSF〉SBF. Results indicated that SMF had an advantage in both biomass and stand volume accumulation among the three restoration approaches.