Coarse woody debris and its relationship with forest floor structure and functions

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Deadwood is a key structural attribute of natural forest ecosystems. From tree senescence to its incorporation into the forest floor, deadwood is central to many complex processes underlying biological diversity, soil productivity and global biogeochemical cycles. The contribution of deadwood to forest ecosystem diversity, as well as the relationships among forest practices, decreases in deadwood quantity and quality and the loss of diversity, are well recognized in central and northern Europe. Yet our understanding of deadwood contribution to other ecosystem and soil functions such as nutrient and carbon cycles is still fragmentary. My working hypothesis is that throughout decay, dead wood undergoes chemical and physical transformations that increase the chemical stability of its components. Deadwood lying on or buried within the forest floor contributes to the biochemical and structural heterogeneity as well as the community structure and functions of forest soils. The nature and magnitude of this contribution is linked to tree species and wood decay stage. I propose to substantiate this general hypothesis by means of studies conducted in permanent plots of monitored stands (1) using chronosequences of dead boles, (2) laboratory  incubations of wood samples of known age or given decay classes and (3) manipulative experiments where the amount of dead wood on the forest floor will be controlled. I intend to compare the evolution of decaying boles of two post-fire pioneer species, jack pine (Pinus banksiana Lamb.) and aspen (Populus tremuloides Michx.) with respect to their biochemical characteristics as well as microbial functional diversity and nitrogen dynamics.