Stocks and Flows of Woody Debris in a Lowland Rainforest, Nanjenshan, Southern Taiwan
Date Issued
2012
Date
2012
Author(s)
Chen, Chia-Wen
Abstract
Recently the climate change has attracted attentions of many ecologists. Forest plays a significant role in carbon cycle, especially those forests in tropical areas. Tropical forests account for up to 40% carbon stock and 30–50% productivity in the terrestrial ecosystem. Most of previous studies for tropical forests carbon balance only focused on living tree biomass, and few paid attention to coarse woody debris (CWD). Coarse woody debris (CWD), which includes fallen and standing dead wood, and fallen branches, comprised about one third of aboveground biomass. However, in the past, it was usually neglected, which might lead to misunderstanding of forest carbon balance. Thus, conducting studies for the stock and dynamics of CWD can give us a comprehensive view on forest carbon cycle.
In tropical areas, the role of CWD has been evaluated in several studies recently; however, most of CWD researches mainly focused on Amazon basin. There are few studies for CWD in Asian rainforests. Thus, I selected a lowland rainforest in the Nanjenshan Reserve Area, which had the research potential of forest carbon balance, to conduct the studies of CWD.
The purposes of this study are to estimate the stock, the seasonal input pattern and the decomposition rate of CWD. The volume and decay levels of CWD were measured on transects (about 680 m in total length). Samples of CWD at each decay level were collected from the field to assess their volume and mass. Wood density of CWD at each decay level was then derived from the ratio of volume and mass. Finally, necromass was obtained from the product of the corresponding density in each CWD decay class and its volume. The seasonal input of CWD was estimated by resurveying the line transects every three months. Annual decomposition rate was acquired by comparing the differences of amount of CWD stocks.
The results showed that the stock in this plot was 10.48–12.68 Mg ha-1 (89.60–99.18% for fallen dead wood and 0.82–10.40% for standing dead wood). The k-value (decay rate constant) was 0.55–2.37 yr-1. The maximum input necromass occurred in October, which might be caused by typhoon disturbances. Furthermore, the amount of necromass of seasonal input ranged from 6.37 to 8.09 Mg ha-1 yr-1.Comparing with other tropical forests, the necromass input was similar but the decomposition rate was higher in Nanjenshan. Thus, the major cause of low CWD stock was attributed to a higher decomposition rate. Furthermore, most of dead wood in Nanjenshan with non-decay-resistant characteristics might promote faster decomposition process.
Subjects
Necromass
Coarse woody debris
Decomposition rate
Forest carbon cycle
Nanjenshan lowland rainforest
Type
thesis
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