长苞铁杉林倒木不同结构组分难降解物含量的分解程度差异

Differences in the Decomposition Degree of the Content of Refractory Substances in Different Structural Components of Fallen Wood in Tsuga longibracteata Forest

[目的]探究倒木不同结构组分难降解物含量的分解程度差异,为长苞铁杉林科学经营提供理论依据。[方法]以福建省天宝岩国家级自然保护区中的长苞铁杉林倒木为对象,采用空间代替时间法,在4种林分类型(长苞铁杉纯林、长苞铁杉+阔叶树混交林、长苞铁杉+猴头杜鹃混交林、长苞铁杉+毛竹混交林)中,探究倒木不同结构组分(树皮、边材、心材)的难降解物含量在分解过程中的变化趋势。[结果]显示:(1)在倒木分解过程中,纤维素、总酚和缩合单宁含量降低,木质素含量升高;倒木缩合单宁含量除了在长苞铁杉+阔叶树混交林中随腐烂等级增加呈先升后降趋势外,在其它3种林分类型中均呈现逐渐下降趋势;(2)从第Ⅰ腐烂等级到第Ⅴ腐烂等级,长苞铁杉倒木的难降解物质含量变化均为显著,其中树皮、边材和心材的纤维素含量分别下降100.08 g·kg^(-1)(20.6%)、73.79 g·kg^(-1)(15.0%)和89.87 g·kg^(-1)(17.5%);木质素含量分别升高42.53 g·kg^(-1)(37.7%)、36.71 g·kg^(-1)(37.9%)和22.25 g·kg^(-1)(22.0%);缩合单宁含量分别下降34.45 g·kg^(-1)(47.4%)、11.02 g·kg^(-1)(23.5%)和16.83 g·kg^(-1)(44.0%);总酚含量分别下降4.87 g·kg^(-1)(57.6%)、1.78 g·kg^(-1)(32.0%)和2.06 g·kg^(-1)(41.7%)。[结论]长苞铁杉林倒木分解中难降解物含量除了与其自身C、N、P含量有关外,还受到林分类型及其结构组分与林分类型交互作用的综合影响。研究结果为指导长苞铁杉林分经营提供了理论依据。

[Objective]This study aimed to investigate the variation in the decomposition degree of refractory substances in different structural components of fallen wood and provide a theoretical basis for the scientific management of Tsuga longibracteata forests.[Method]Based on the fallen wood from Tsuga longibracteata forests within the Tianbaoyan National Nature Reserve of Fujian Province,the space-for-time substitution method was employed to examine changes in the content of refractory substances within different structural components(bark,sapwood,and heartwood)of fallen wood across four forest types(T.longibracteata pure forest,T.longibracteata+broad-leaved mixed forest,T.longibracteata+R.simiarum mixed forest,T.longibracteata+P.pubescens mixed forest)during the decomposition process.TChanges in the content of refractory substances within different structural components(bark,sapwood,and heartwood)of fallen wood were investigated throughout the decomposition process.[Results]Results showed that:(1)During the decomposition process of fallen logs,the contents of cellulose,total phenols,and condensed tannins decreased,while the content of lignin increased.The condensed tannin content of fallen wood exhibited a gradual downward trend in the other three forest types except for the T.longibracteata+broad-leaved mixed forest,which showed an initial increase followed by a decrease with the increase of decay level.(2)There was a significant change in the content of recalcitrant substances in the fallen wood of Tsuga longibracteata.with a decrease of 100.08 g·kg^(-1)(20.6%),73.79 g·kg^(-1)(15.0%)and 89.87 g·kg^(-1)(17.5%)in the cellulose content of bark,sapwood and heartwood,respectively.The lignin content increased by 42.53 g·kg^(-1)(37.7%),36.71 g·kg^(-1)(37.9%)and 22.25 g·kg^(-1)(22.0%),respectively.The condensed tannin content decreased by 34.45 g·kg^(-1)(47.4%),11.02 g·kg^(-1)(23.5%)and 16.83 g·kg^(-1)(44.0%),respectively.The total phenolic content decreased by 4.87 g·kg^(-1)(57.6%),1.78 g·kg^(-1)(32.0%)and 2.06 g·kg^(-1)(41.7%),respectively.[Conclusion]In addition to its own C,N,P content,the content of refractory substances in the decomposition of fallen wood of T.longibracteata forest is also affected by the interaction of stand type and its structural components with stand type.The results provide a theoretical basis for guiding the management of Tsuga longibracteata forest.