Woody debris (WD) is an important terrestrial carbon pool contributing an estimated of 10-20% globally, and can over 50% of the carbon in some forests. Disentangling specific factors effects on wood decomposition remains a challenge given the complexity and the interaction among factors affecting this ecological process.
However, one would better draw meaningful conclusions if one designs an experiment that controls for certain factors/variables but leaves others to vary for example establishing and incubating substrates with different innate functional traits. Moreover, one could make use of substrates that have grown in the same environment for example plants growing in botanical garden. The use of phylogenetic approaches in understanding the role of evolutionary history in determining biological processes is well established. However, there is paucity of studies investigating wood decomposition in a phylogenetic context.
At Xishuangbanna Tropical Botanical Garden we conducted a three year long experiment on the role of phylogeny in the decomposition of woody debris (WD). Using the garden's plant collections we sampled fresh wood logs (5 cm diameter) from 25 species 20 families selected across the phylogeny of higher plants. In each major clade, we selected species with both high and low wood density to maximize the range of wood traits represented at this scale. These wood logs were laid on the floor of a patch of secondary rain forest within the garden and we monitored mass loss periodically over three years. In addition to phylogeny, we collected data on wood density, initial bark and wood chemistry, and analyzed microbial biomass dynamics in the decomposing wood using both phospholipids fatty acids (PLFA) method.
While examining mass loss results after two years of incubation, we found Kleinhovia hospita has the lowest initial wood specific gravity (WGGo) and lost dry mass the fastest while Mesua Ferrea, a species that has the highest WSGo lost its dry mass the slowest. On the other hand, species in the Magnolids clade decomposed the fastest whereas species from the Malpighiales were the most slow to decompose. We are still analyzing the preliminary results with as well results from the microbial biomass dynamics.
We hope through the phylogenic approach to produce a predictive model that incorporates microbial biomass dynamics and tree species position in tree phylogeny can be used to calibrate WD decomposition globally based on knowledge of forest tree species composition.