SP 10: Coarse woody detritus decomposition

Coarse woody detritus decomposition

Principal investigator(s):

Co-Principal investigator(s):

Phd candidate(s):

Contact adress:

University of Leipzig, Institute of Biology I, Department for Systematic  Botany and Functional Biodiversity, Johannisallee 21-23, 04103 Leipzig, Germany

Summary

Dead wood comprises an important part of forest ecosystems. A large amount of organic matter is represented by coarse woody debris, storing up to 22 % of the forest carbon. But so far, its dynamics have largely been neglected in ecological studies of subtropical forests.

The roles which dead trees play in forest ecosystems are numerous. They support a rich food web comprising bacteria, fungi, and both invertebrate and vertebrate animals. Fallen snags can reduce erosion by providing a physical barrier to soil movement. And during decomposition mineral nutrients are being released which are essential for subsequent plant growth in the forest.

Most of what we know about dead wood dynamics – including the underlying mechanisms for input and decomposition rates – originates from studies conducted in temperate and boreal forests. In the moist and warm climate of subtropical forests however the hierarchy of factors controlling decomposition processes might differ from temperate and boreal forests. For example termites play a leading role in subtropical decay processes, and the climate promotes fungal and microbial activity.

Additionally to studying dead wood dynamics in the subtropics the BEF China Project sets the ideal platform for studying the relationship between tree species richness and dead wood dynamics. So far, nothing is known about this potential relationship. We will estimate direct and indirect effects of stand diversity on wood decay and tree death.

In our subproject we combine observational and experimental approaches in the comparative study plots (CSPs - situated in a secondary forest stand of different tree diversity and stand age) as well as in the two experimental sites (planted forest plots of different tree diversity). (1) We follow the fate of abundant dead wood which originated from an ice storm in winter 2009. During subsequent resurveys we evaluate the ongoing decay of the wood and its movement in the plot, and assess newly fallen wood to evaluate dead wood input rates. (2) To evaluate the effects of tree diversity, stand structure and abiotic factors we deposited wood of standardized size in the CSPs and the experimental plots. (3) We account for the impact of different decomposer groups by using a litterbag approach with different mesh sizes; additionally we study the effect of soil contact for decomposition. (4) Finally, we investigate the effect of wood traits on decomposition rates by using wood of 22 different tree species. (5) After retaining the wood for measuring mass loss and chemical perturbation, we collect the invertebrates associated with each sample to get a better picture of plot and species specific decomposers.

Objectives

The overarching goals of this subproject are threefold:

• (1) To close the gap in the ecosystem carbon budget of subtropical forests by providing estimates of CWD input and decomposition rates.
• (2) To explore the direct and indirect role of tree species diversity on coarse woody debris dynamics in near-natural and experimental subtropical forests of China.
• (3) To quantify the sensitivity of CWD decomposition to topographic variation in the experimental sites.