Mesophication of upland oak forests: Implications of species-specific differences in leaf litter decomposition rates and fuelbed composition

Without periodic fire, historically open-canopied, oak-dominated upland woodlands of the central and eastern United States are shifting to closed-canopied forests with increased abundance shade-tolerant typically fire-sensitive species. Once established, these encroaching species (i.e., mesophytes) hypothesized initiate a positive feedback termed mesophication where mesophytes perpetuate conditions that foster their own proliferation at expense oaks (Quercus spp.). One potential mechanism is reduced fuel loads through faster decomposition rates mesophyte leaf litter, as litter primary in closed canopy forests. To better understand how different tree impact loads, we compared initial chemistry one-year (2016–2017) four non-oak exhibiting region and/or relatively high sapling/midstory relative overstory on our sites (red maple [Acer rubrum], sugar [A. saccharum], American beech [Fagus grandifolia], hickory [Carya spp.]) three oak (black [Q. velutina], chestnut montana], white alba]) an forest north-central Kentucky. We also evaluated fuelbed mass, composition, bulk density beneath (20–60 cm DBH) individuals each following fall December 2016. Except for (66% mass remaining), found especially red maple, decomposed fastest (45 48% slowest (54–64% remaining). Further, although total were similar species, composition differed. Under crowns, proportion from non-oaks was 22–35%, while under only 10–12%. This suggests individual trees impacting crowns despite continued dominance stand scale. Considering differences between both inputs based allometric equations rates, modeled composed entirely or Carya spp. ?20% lower than after one year decomposition. While limited examined this study, findings confirm non-oaks, excluding beech, decomposes more rapidly alter suggesting will become less-flammable increasing mesophytic dominance.