Quantifying arthropod contributions to wood decay

Authors


Correspondence author. E-mail: mulyshen@fs.fed.us

Summary

  1. Wood decomposition is driven primarily by microbial activity but proceeds at greatly varying rates depending on regional or local differences in physical conditions and other determinants. Although many arthropod taxa (e.g. termites, wood-boring beetles) are known to consume or excavate dead wood, their contributions to the decay process remain largely unmeasured.
  2. Quantifying arthropod contributions to wood decay is fraught with challenges, but no guidelines are available to assist researchers in designing and carrying out studies of this kind. We therefore sought to provide a critical review of previous studies on this important topic and discuss methodological considerations that may benefit future researchers.
  3. The biggest challenge inherent to such research involves excluding arthropods from dead wood (i.e. the reference treatment) without otherwise affecting the decay process. Because mesh bags are likely to alter physical conditions relative to unenclosed substrates and insecticides are likely to inhibit microbial growth, additional experimentation is needed to isolate the arthropod effect. Alternatively, partial exclusion or temporary exposure methods may produce less confounded results.
  4. In determining the initial volume of a wood sample (e.g. to estimate the initial mass using specific gravity data), there is a trade-off between the accuracy of this measurement and the realism of the study. A method involving image analysis is described for obtaining accurate initial volume estimates for naturally occurring woody substrates. When measuring changes in specific gravity during the decay process, initial sample volumes must be used in these calculations as opposed to the water displacement technique which fails to measure wood removed by arthropod activity.
  5. Termites carry large amounts of soil into dead wood, and this behaviour complicates efforts to measure their contributions to wood decay. A novel method for isolating termite soil by burning the wood is described, and some preliminary results are presented.
  6. These and other recommendations described herein should aid efforts to quantify the contributions of arthropods to wood decay. Such research is of great interest given the broad importance of dead wood to forest ecosystems–including its role in carbon storage–and the diversity and conservation concern of the species involved.

Ancillary