腐烂等级和径级对天宝岩长苞铁杉林木质残体理化性质的影响

Effects of decay grades and diameter classes on physicochemical properties of woody debris in Tsuga longibracteata forest in Tianbaoyan National Nature Reserve

木质残体是森林生态系统的重要组成部分,其理化性质影响木质残体的分解。本研究以集中分布于天宝岩国家级自然保护区的长苞铁杉(Tsuga longibracteata)林木质残体为对象,将4个不同类型林分的木质残体划分为5个腐烂等级和4个径级,研究林分类型、腐烂等级、径级及其交互作用对木质残体理化性质的影响。结果表明:从物理性质来看,长苞铁杉林木质残体的木材密度随腐烂等级的增加而下降,含水率却呈上升趋势;径级仅对长苞铁杉纯林木质残体的含水率具有显著影响;腐烂等级和径级的交互作用对各林分木质残体的物理性质均无显著影响;从化学性质来看,腐烂等级对木质残体C含量无显著影响,但对3个混交林木质残体的N含量、C/N具有显著影响;径级仅对长苞铁杉纯林木质残体的P含量以及长苞铁杉+猴头杜鹃(Rhododendron simiarum)混交林的P含量、C/N具有显著影响;交互作用对长苞铁杉林木质残体的化学成分普遍无显著影响;木材密度与长苞铁杉+猴头杜鹃混交林木质残体的C、P含量和长苞铁杉+毛竹(Phyllostachys edulis)混交林木质残体的C、N、P、C/N呈显著相关;含水率与长苞铁杉纯林的N、P、C/N和长苞铁杉+毛竹混交林木质残体的P、C/N呈显著相关。由此可见,木质残体的物理性质是影响养分含量变化的重要因素。

Woody debris is a key component of forest ecosystem, and the physicochemical properties are important for its decomposition. In this study, we examined the effects of stand type, decay grade, diameter class, and their interaction on the physicochemical properties of woody debris of Tsuga longibracteata in four different stands in Tianbaoyan National Nature Reserve. Woody debris was classified into five decay grades and four diameter classes. The results showed that wood density of woody debris in T. longibracteata forests decreased with the increased decay grade, but moisture content increased. The diameter class had a significant effect on moisture content of woody debris only in the T. longibracteata pure forest. The interaction of decay grade and diameter class had no significant effect on the physical properties of woody debris in each stand. In terms of chemical properties, decay grade did not affect C content of woody debris, but significantly affected N content and C/N ratio of woody debris in three mixed forests. The diameter class had significant effects on P content of woody debris in the T. longibracteata pure forest and P content and C/N in the T. longibracteata+Rhododendron simiarum mixed forest. The interaction had no significant effect on the chemical composition of the woody debris across all stand types. Wood density was closely correlated with C and P contents of woody debris in the T. longibracteata+R. simiarum mixed forest, as well as C, N, P contents and C/N in the T. longibracteata+Phyllostachys edulis mixed forest. Moisture content had significant correlation with N, P, C/N of woody debris in the T. longibracteata pure forest and P, C/N in the T. longibracteata+P. edulis mixed forest. In conclusion, the physical properties of woody debris are important factors affecting nutrient content.