Decomposition and Mass of Woody Detritus in the Dry Tropical Forests of the Northeastern Yucatan Peninsula, Mexico

Abstract

The decomposition rates and mass of fine (< 10-cm-diameter) and coarse (> 10-cm-diameter) woody detritus were measured in the dry tropical forests of the northeastern Yucatan Peninsula. The smallest mass of woody detritus was found in undisturbed stands: fine fractions averaged 4.7 Mg ha-' and coarse fractions ranged between 13 and 38 Mg ha-I. The largest mass of fine woody detritus (32.2 Mg h a 1 ) was found in a hurricane-disturbed forest; whereas, the largest mass of coarse woody detritus (99.5 Mg ha-') was found in stands disturbed by catastrophic fires. A decomposition time-series study installed in 1989 indicated that decomposition rates varied greatly among species and diameters of branch segments. Over a 4-year period, the decomposition rate constant for fine woody detritus ranged from 0.15 1 to 1.019 y e a r L and that for coarse woody detritus ranged from 0.008 to 0.615 year1. The halflife of woody detritus increased 33-fold (among pieces ranging from 1 to 30 cm in diameter) for the most decayresistant species (Manilhara zapota) but was relatively constant for the least decay-resistant species (Bursera simaruba). The wide range in decomposition rates observed in these forests indicates that the poor substrate quality of some species may override climatic (e.g., warm temperatures) and biotic (e.g., termites) factors favorable to rapid decomposition, leading to a substantial accumulation of woody detritus.

Biomass Dynamics in Amazonian Forest Fragments

“…Finally, it is noteworthy that our average turnover estimate in forest interiors (0.12 Ϯ 0.04 yr Ϫ1 ) is not greatly dissimilar from that derived for the same plots by Chambers et al (2000), based on direct observations of decomposition in 155 randomly selected dead trees (0.17 yr Ϫ1 ). Thus, while experimental decomposition studies (e.g., Harmon et al 1995) in forest fragments are needed to verify our findings, we have some confidence that necromass turnover actually increased near forest edges.…”

A Review of Above Ground Necromass in Tropical Forests

“…In order to quantify necromass from volume estimates, measurements of the densities of necromass pieces are required. More highly decayed logs theoretically should have less mass (Harmon et al 1995). A common approach to quantification of mass is the stratification of necromass into decay classes and the application of decay-class-wide densities to the volume quantified by decay class.…”

“…This methods has been adopted by other studies , Baker et al 2007, Chao et al 2008 Decay classes are usually described in two or more categories (Harmon et al 1986, Chambers et al 2000. These decay classes range from newly fallen necromass to highly decayed material that can be broken apart by hand (Harmon et al, 1995;Keller et al, 2004b) (Image 5). For a good description of a five decay class description, please refer to Keller et al (2004).…”

Avaliação da quantidade de resíduos lenhosos em floresta não explorada e explorada com técnicas de redução de impactos, utilizando amostragem por linha interceptadora, no Médio Mojú, Amazônia Oriental, Brasil

“…As peças de RL registradas foram classificadas no ato da coleta de dados, de acordo com o respectivo estado de decomposição, representadas pelas classes citadas por Harmon et al (1995). Estas classes de decomposição variaram, do material lenhoso morto mais recentemente (classe 1) ao mais apodrecido (classe 5), de acordo com os seguintes critérios: -Classe 1: material lenhoso constituído por madeira sólida, com folhas e/ou galhos finos unidos à peça principal, sem degradação perceptível; -Classe 2: material lenhoso sólido com casca intacta, porém sem folhas ou galhos finos; -Classe 3: material lenhoso semelhante ao da Classe 2, exceto pela casca apodrecida; -Classe 4: material lenhoso um tanto apodrecido que pode ser quebrado quando chutado (pontapés); -Classe 5: material lenhoso apodrecido, friável, e que pode ser quebrado com as mãos nuas.…”