PARENT SESSION
Contributed Oral Session 127: Forest Structure and Communities
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 513 A, Level 5, Palais des congrès de Montréal

Measurement and modeling of vertical structure and complexity of Structural Complexity Enhancement treatments in northern hardwood forests.

Williams, Laurel^*,, Keeton, William, Canham, Charles, Zenner, Eric,

ABSTRACT- Vertical structure, the three-dimensional allocation of above-ground forest biomass, influences many aspects of ecosystem function. Late-successional and old-growth (LSOG) forests often exhibit significant vertical structural complexity. In the northeastern USA, LSOG forests are under-represented in terms of the historical range of variability. Interest in managing northern hardwoods forests for old-growth characteristics and related ecosystem services continues, but methods for accurately quantifying vertical structure are currently inadequate, and new treatments designed to enhance LSOG characteristics have rarely been field-tested. The Vermont Forest Ecosystem Management Demonstration Project (FEMDP) is testing a treatment called Structural Complexity Enhancement (SCE), as well as single- and group-tree selection treatments modified to enhance post-harvest structural retention. Among other innovative techniques, SCE uses an unconventional marking guide based on a rotated sigmoid target diameter distribution and target basal area (BA; 34 m²/ha) and dbh (90 cm) indicative of old-growth structure. SCE's structural objectives include increased complexity and re-allocation of BA to larger diameter classes. We collected detailed post-treatment data on vertical structure within the Mt. Mansfield State Forest in Vermont. Each treatment is replicated in 2 2-ha units that each contain 5 0.1-ha plots. We stem-mapped trees >5 cm dbh within plots and recorded tree diameter, maximum and minimum crown radii, radius weighting, and canopy height and depth. We used SORTIE, a mechanistic, individual-based, and spatially explicit successional model, to project stand development 500 years ahead. Vertical structure is compared between treatments and against controls and no-impact scenarios using the Structural Complexity Index (SCI), which describes the roughness of a forest's canopy. Our study helps inform the development of silvicultural practices designed to promote vertical structural complexity characteristic of LSOG forests.

Key words: vertical structure, complexity, SORTIE, SCI