Characterization of coarse woody debris across a 100 year chronosequence of upland oak-hickory forests

In most forest ecosystems, the total amount of coarse woody debris and its distribution into decay classes change over time from harvest to old growth stages. The relationship of decomposition classes to substrate quality is important to determine the contribution of woody debris to ecosystem nutrie nt cycling and forest development. The two objectives of this study were: ( 1) to determine if down dead wood (DDW) nutrient content varied with decomp osition class or forest stand age; (2) to determine if DDW decomposition cl asses were related to indicators of substrate quality. Volume, mass, and in dicators of substrate quality, such as N content and lignin:N ratio, were d etermined for woody debris from several decomposition classes in upland har dwood forest stands of different ages in southern Indiana, USA. Results sho wed a large decrease in volume and mass of DDW from recently harvested to m ature stands. The dominant decomposition class shifted from Class II to Cla sses m and IV with increasing stand age. No Class I woody debris was found within any of the study plots. Nutrient concentration (N, S, and P) and car bohydrate fractions (soluble, hemicellulose, cellulose, and lignin) all var ied significantly among certain decomposition classes, but N and P concentr ation and the C:N ratio were the best indicators of decomposition class. Pa tterns of P retention in decomposition classes suggested a strong potential for immobilization of this nutrient in woody debris. Based on substrate qu ality groupings, there were three distinguishable decomposition classes: Cl asses II and m, Class IV, and Class V. (C) 2001 Elsevier Science B.V. All r ights reserved.