Signature Wood Modifications that Reveal Decomposer Community History

Abstract

Correlating plant litter decay rates with initial tissue traits (e.g. C, N contents) is

common practice, but in woody litter, predictive relationships are often weak. Variability

in predicting wood decomposition is partially due to territorial competition among fungal

decomposers that, in turn, have a range of nutritional strategies (rot types) and

consequences on residues. Given this biotic influence, researchers are increasingly

using culture-independent tools in an attempt to link variability more directly to

decomposer groups. Our goal was to complement these tools by using certain wood

modifications as 'signatures' that provide more functional information about

decomposer dominance than density loss. Specifically, we used dilute alkali solubility

(DAS; higher for brown rot) and lignin:density loss (L:D; higher for white rot) to infer rot

type (binary) and fungal nutritional mode (gradient), respectively. We first determined

strength of pattern among 29 fungi of known rot type by correlating DAS and L:D with

mass loss in birch and pine. Having shown robust relationships for both techniques

above a density loss threshold, we then demonstrated and resolved two issues

relevant to species consortia and field trials, 1) spatial patchiness creating gravimetric

bias (density bias), and 2) brown rot imprints prior or subsequent to white rot

replacement (legacy effects). Finally, we field-tested our methods in a New Zealand

Pinus radiata plantation in a paired-plot comparison. Overall, results validate these lowcost

techniques that measure the collective histories of decomposer dominance in

wood. The L:D measure also showed clear potential in classifying 'rot type' along a

spectrum rather than as a traditional binary type (brown versus white rot), as it places

the nutritional strategies of wood-degrading fungi on a scale (L:D=0-5, in this case).

These information-rich measures of consequence can provide insight into their

biological causes, strengthening the links between traits, structure, and function during

wood decomposition.