Termites amplify the effects of wood traits on decomposition rates among multiple bamboo and dicot woody species

Guofang, Ming Dong* et al. 2015.

枯死木分解是陆地生态系统碳循环的关键过程,控制对气候其反馈调节的碳储量。在热带亚热带森林中,白蚁是枯死木的主要分解者,然而白蚁与微生物和枯死木功能性状在枯死木分解的认识相对不足。此外,目前研究主要偏向双叶子枯死木的分解,木本单子叶植物尤其是竹类也对热带亚热带地区碳循环有重要贡献。 本研究采用“同质园实验”利用66个被子植物(31个竹类、8个竹类禾草、18个核心真双子叶植物、9个木兰类)茎杆枯死木,第一次将枯死木性状和白蚁对其分解速率的影响予以分开。验证如下假说:1)竹类(单子叶)植物分解速率慢于木兰类植物或核心真双子叶植物,2)微生物和白蚁驱动的分解速率均与初始密度和干物质含量负相关。结果表明:竹类枯死木分解速率一般慢于双子叶植物,在相同的密度或直径下竹类分解速率略小于双子叶植物。随着密度和干物质含量增加,竹类和双子叶植物枯死木分解速率降低。白蚁对枯死木分解中的贡献巨大,能解释53.4%的分解速率变异,白蚁更喜食低密度的枯死木。白蚁加强了枯死木性状及微生物驱动的枯死木分解速率的关系。这些结果表明,之前未知的枯死木质量、直径、白蚁和分解者微生物之间的这些关系将有助于我们认识热带亚热带枯死木分解的驱动机制以及它对全球碳循环的贡献。

1. Wood decomposition is a key process in the terrestrial carbon cycle, controlling carbon storage with feedback to climate. In (sub-)tropical forest, termites are major players in wood decomposition, but their role relative to that of microbial decomposers and wood traits of different tree species is poorly understood. The current literature also has strong bias towards dicot tree decomposition, while abundant woody monocots, particularly bamboos, also contribute greatly to (sub-)tropical carbon cycling.
2. Here, we present the first experiment to disentangle effects of dead wood traits and termite activity on decomposition of 66 angiosperm species of wide-ranging phylogenic position: 31 bamboos, eight non-bamboo Poaceae, 18 eudicots, and nine magnoliids. We incubated dead stems of up to 4 size classes per species in a ‘common-garden’ in tropical S China. We tested the hypotheses that (1) dead wood of bamboo (monocots) is less decomposable than dead wood of eudicots or magnoliids; (2) both microbial and termite-driven decomposition show negative relationships with initial wood density and with dry matter content.
3. Bamboo wood generally decomposed more slowly than dicot wood but only slightly slower at given wood density or diameter. Wood decomposition in both bamboo and dicot clades decreased with wood density or dry matter content. Termites contributed greatly to this pattern, explaining 53.4% of the variance in wood decomposition and preferentially attacking dead wood of lower initial density, which corresponded with thicker outer culm walls in the case of bamboo species. Thus termites strongly strengthen the relationship between species’ wood traits and litter decomposition as driven by microbial activity.
4. Synthesis. These previously unknown relationships among dead wood quality, diameter, termites and decomposing microbes of both woody monocots and dicots will advance our understanding of the driving mechanisms of (sub-)tropical wood decomposition and its contribution to the global carbon cycle.