Decomposition of coarse woody debris in an old-growth Indiana forest

Decay rates of Quercus sp., Carya sp., Fagusgrandifolia, and Acer sp. coarse woody debris in an old-growth southern Indiana forest were 0.018, 0.035, 0.019, and 0.045 per year, respectively, based on changes in density over a span of 25+ years. Their respective biomass values were 15, 2.3, 0.2, and 0.4 t*ha −1 . The greatest differences in decay rates of cellulose were between maple (high) and oak (low), and of lignin were between beech (high) and oak (low). Carbon to nitrogen ratios approached 100 and nitrogen to phosphorus ratios approached 20 in the older age-classes. On average, oak, hickory, beech, and maple logs contained 1.66, 1.10, 0.14, and 0.19 kg nitrogen and 0.056, 0.070, 0.005, and 0.016 kg phosphorus, respectively. Meentemeyer's model based on actual evapotranspiration predicted a decay rate of 0.80 per year, which is 27 times larger than the decay rates calculated on changes in density. Fragmentation loss rates for these four genera were estimated to be 0.288, 0.802, 1.171, and 0.338 per year, respectively. Decay rates based on diameter of coarse woody debris ranged from 0.0027 to 0.0337 per year. All these factors are important in understanding the process of decay of coarse woody debris in this forest. The roles of fragmentation in the decay of coarse woody debris and of fungitoxic extractives need more study.