The Mass Loss and Humification of Stumps and Roots in Masson Pine Plantations Based on Log File Records

• Published in: PloS one 2016-08, Vol.11 (8), p.e0160913-e0160913
• Main Authors: Zhou, Jiao, Wu, Fuzhong, Yang, Wanqin, Tan, Bo, Xu, Zhenfeng, Zhang, Jian, Duan, Fei, Liu, Hui, Justine, Meta Francis
• Format: Article
• Language: English
• Subjects: Analysis; Bark; Biodiversity; Biology and Life Sciences; Biomass; Carbon; Carbon sequestration; Coarsening; Collaboration; Debris; Decay; Decay rate; Decomposition; Detritus; Ecology; Ecology and Environmental Sciences; Ecosystems; Engineering and Technology; Environmental aspects; Forest management; Forestry; Forests; Humic Substances; Humification; Humus; Nitrogen; Physical Sciences; Pine trees; Pinus; Pinus massoniana; Plant Roots - chemistry; Plant Roots - microbiology; Plantations; Roots; Roots (Botany); Soil - chemistry; Soil fertility; Studies; Systems analysis; Time Factors; Trees; Wood - chemistry; Wood - microbiology; Woody plants
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0160913

Stumps account for a large proportion of coarse woody debris in managed forests, but their decay dynamics are poorly understood. The loss of mass and the degree of humification of the above-ground woody debris, below-ground woody debris, bark and root system (R1, 10 mm ≥ diameter > 0 mm; R2, 25 mm ≥ diameter >10 mm; 100 mm ≥ R3 > 25 mm; R4 > 100 mm) of Masson pine (Pinus massoniana) stump systems were evaluated in southwestern China in a chronosequence of plantations cut 1-15 years prior to the study. The results indicated that above-ground woody debris decomposed more quickly than below-ground woody debris and bark, whereas the degree of humification followed the opposite trend. Compared with one-year stumps, the mass losses of 15-year stump systems were 60.4% for above-ground woody debris, 42.1% for below-ground woody debris, 47.3% for bark, 69.9% for R1, 47.3% for R2, 51.0% for R3, and 83.2% for R4. In contrast, below-ground woody debris showed a greater degree of humification compared with other components in the stump system. Among the root system, fine roots (R1, diameter ≤ 10 mm) had the largest k value (0.09), whereas the decay rate of coarser roots (R2, R3, R4; diameter > 10 mm) increased with increasing root diameter. However, coarse roots showed a larger degree of humification (0.2-0.6) than fine roots (0.3-0.4). These results suggest that below-ground woody debris and coarse roots may display a higher degree of humification, showing greater short-term contributions to overall humification when compared with the other components in the stump system.