Chin J Plan Ecolo ›› 2015, Vol. 39 ›› Issue (1): 14-22.

• Orginal Article •

### Changes in log quality at different decay stages in an alpine forest

CHANG Chen-Hui, WU Fu-Zhong, YANG Wan-Qin*(), TAN Bo, XIAO Sa, LI Jun, GOU Xiao-Lin

1. Key Laboratory of Ecological Forestry Engineering, Institute of Ecological Forestry, Sichuan Agricultural University, Chengdu 611130, China
• Received:2014-07-07 Accepted:2014-11-06 Online:2015-01-22 Published:2015-01-10
• Contact: Wan-Qin YANG E-mail:scyangwq@163.com
• About author:

# Co-first authors

Abstract: Aims

Log is an important pool of carbon (C) and nutrients in alpine forest ecosystems. Changes in log quality with decay could reveal the process of C and nutrient release during log decomposition. However, little information is available on this. Therefore, this study aims to understand the changes in log quality during log decaying.

Methods

Changes in C, nitrogen (N), phosphorus (P), lignin and cellulose concentrations were investigated in the heartwood, sapwood and bark of fir (Abies faxoniana) logs at five (I-V) decay stages in an alpine forest in western Sichuan, China. The stoichiometry of C:N:P and the ratios of lignin:N, lignin:P, cellulose:N, and cellulose:P were also calculated.

<i>Important findings </i>

C content in bark increased from the stage I to stage III of decay and then significantly decreased, but in the heartwood and sapwood it decreased from the stage I through stage V, especially at stages IV and V. N content increased from the stage I through stage V regardless of the log components. P content in sapwood also showed tended to increase from the stage I through stage V, but P content in heartwood and bark decreased following an increase tendency. In comparison with sapwood and heartwood, bark had the lowest C:N:P stoichiometry at the same decay stages. Percentage of the labile to total C (Fm) also inferred that bark was the most decomposable component. The higher C:N:P stoichiometry in sapwood was observed in logs of the stages I and II, but higher Fm in heartwood was detected from the stage III to stage V. Critical values of C:N in sapwood and bark and C:P in heartwood, sapwood and bark were negatively correlated with the initial N and P concentrations, respectively. Cellulose concentration decreased from the stage I to stage V regardless of log components, and among different components followed the order of heartwood > sapwood > bark at corresponding decay stages. In contrast, lignin concentration increased from the stage I to stage V regardless of log components, and among different components followed the order of bark > sapwood > heartwood at corresponding decay stages. Cellulose degraded faster than lignin regardless of log components, and the ratio of lignin:cellulose increased significantly at the advanced decay stages. Moreover, bark showed a relatively higher lignin:cellulose ratio compared with sapwood and heartwood. In addition, statistical analysis suggested that the degradation of lignin and cellulose in logs would be affected by N concentration. Bark decay was limited by N at early decay stages but by P at all decay stages, and the decay of heartwood and sapwood was limited by both N and P based on ecological stoichiometry theory.