摘要:倒木分解是森林生态系统中重要的养分循环过程，倒木中的难分解物质对土壤有机质积累具有积极作用。但关于森林林窗和附生植物对倒木难分解物质含量的影响还不清晰。为了理解林窗更新及附生植物生长对倒木总酚和缩合单宁含量的影响，2013年8月在川西高山原始森林进行样地布置，在进行3年附生植物去除处理后，2016年8月在不同林窗位置（林窗、林缘和林下）下两种处理（附生植物去除和保留）不同腐解等级（I-V）进行岷江冷杉（Abies faxoniana）倒木不同结构（心材、边材和树皮）样品采集，分析其总酚和缩合单宁含量。结果表明：树皮总酚和缩合单宁含量显著高于心材和边材，树皮总酚和缩合单宁含量随腐解等级变化差异不显著；森林林窗对Ⅲ-V腐解等级心材和边材总酚含量具有显著影响，但对心材和边材缩合单宁影响差异不显著，林窗对倒木树皮总酚和缩合单宁含量影响差异极显著且两者含量特征均表现为林窗 > 林缘 > 林下；附生植物去除处理降低了心材缩合单宁和边材总酚含量，增加了倒木边材缩合单宁含量。附生植物去除处理对树皮影响和林窗位置存在交互作用，林缘和林下的倒木附生植物去除显著降低了树皮总酚和缩合单宁含量。此外，不同林窗位置的温度差异是导致树皮总酚和缩合单宁含量变化的主要原因，附生植物去除对倒木pH的影响也可能是影响倒木总酚和缩合单宁含量的原因之一。由此可见，高山森林林窗更新及附生植物生长会显著影响倒木难分解物质含量变化特征，为进一步了解倒木分解过程在养分循环及对环境的响应提供了新的角度。



Abstract:Fallen log decomposition is an important process of carbon and nutrient cycling in most of forest ecosystems. The previous studies have found that the recalcitrant the components in fallen log positively promoted the soil organic matter accumulation. However, the effects of forest gap positions and epiphytes removal on the concentrations of resistant material in fallen log remain unclear. Thus, we conducted a field experiment to explore how the gap regeneration and epiphytes removal influence the total phenols and condensed tannins during the dead wood degradation in an alpine Minjiang fir (Aibes faxoniana) forest in western Sichuan from August 2013 to August 2016. We sampled from two treatments (removal and retention of epiphytes) with different fallen log structures (heartwood, sapwood and bark) of five decay classes (I-V) in three gap positions (gap center, gap edge and closed canopy). The total phenols and condensed tannins concentrations were measured. The results showed that the concentrations of total phenols and condensed tannins in bark were significantly higher than those of heartwood and sapwood. The concentrations of total phenols and condensed tannins in decaying bark varied slightly with different decay classes. Gap positions gave strong effects on the concentrations of total phenols in Ⅲ-V decay classes of heartwood and sapwood, that is to say, the concentrations of total phenols in Ⅲ-V decay classes of heartwood and sapwood varied greatly with gap position. However, no significant difference of condensed tannins in heartwood and sapwood was observed among gap positions. The gap positions exerted extremely significant effects on the concentrations of total phenols and condensed tannins in decaying bark, and the values in the order of concentrations were, gap center > gap edge > closed canopy. The epiphytes removal lowered the concentration of condensed tannins in decaying heartwood and the concentration of total phenols in decaying sapwood, but increased the concentration of condensed tannins in decaying sapwood. The interaction of epiphytes and gap positions significantly affected the concentrations of total phenols and condensed tannins in decaying bark. In gap edge and closed canopy, epiphyte removal significantly lowered the concentrations of total phenols and condensed tannins in decaying bark. Additionally, the changes in temperature resulted from gap position was a major driver of the concentrations of total phenol and condensed tannins in decaying bark. Moreover, the change of log pH resulted from epiphytes removal might also be one of the reasons of the differences of concentrations of total phenols and condensed tannins in fallen log. Together, gap regeneration and epiphytes can regulate the concentrations of recalcitrant components in decaying fallen log in the alpine forest. The results provided with new insights for us to understand the roles of forest gap and epiphyte in carbon and nutrient cycling in fallen log decomposition.





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