New Harvard Forest Publication: Structural Comparisons of Old and Second Growth Hemlock Forests

Old-growth forests are valuable sources of ecological, conservation, and management information, yet these ecosystems have received little study in New England, due in large part to their regional scarcity. To increase our understanding of the structures and processes common in these rare forests, former REU (2000) and Ph.D. (2007) student Tony D'Amato along with HF ecologists David Orwig and David Foster studied the abundance of downed coarse woody debris (CWD) and snags and live-tree size-class distributions in 16 old-growth hemlock forests in western Massachusetts. Old-growth stands were compared with eight adjacent second growth hemlock forests to gain a better understanding of the structural differences between these two classes of forests resulting from contrasting histories. The variation in structural attributes among old growth stands, particularly the abundance of downed CWD, was closely related to disturbance history. In particular, old-growth stands experiencing moderate levels of canopy disturbance during the last century (1930s and 1980s) had greater accumulations of CWD, highlighting the importance of gap-scale disturbances in shaping the long-term development and structural characteristics of old-growth forests. These findings are important for the development of natural disturbance-based silvicultural systems that may be used to restore important forest characteristics lacking in New England second-growth stands by integrating structural legacies of disturbance (e.g., downed CWD) and resultant tree-size distribution patterns. This silvicultural approach would emulate the often episodic nature of CWD recruitment within old-growth forests.

D'Amato, A. W., D. A. Orwig and D. R. Foster. 2008. The Influence of Successional Processes and Disturbance on the Structure of Tsuga Canadensis Forest. Ecological Applications, 18(5), pp. 1182-1199.