PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Implications for forest productivity of the fate of N released from foliar litter.

Piatek, Kate^*,1, ¹ West Virginia University, Morgantown, WV, USA

ABSTRACT- Forest harvesting and site preparation remove nutrients in woody biomass, green biomass, forest floor, and often topsoil, leading to concerns for a potential decline in forest productivity. Declines in productivity due to nutrient removals have been documented in some cases. More interestingly, increases in productivity after nutrient removals have been observed on N-limited sites. Such observations are inconsistent with the fact that organic matter is a substantial source of nutrients. To reconcile these conflicting reports, I propose that the C:N ratio of the organic materials remaining after harvest is conducive to net N mineralization benefiting the regrowing stands. Unfortunately, complete organic matter budgets are rarely known after forest harvesting. Woody residue loads remaining after harvest vary considerably due to both, harvest intensity and forest type, and may range from 24 tons/ha in the central Appalachian hardwoods to 83 tons/ha in a Douglas-fir forest in the Pacific Northwest. Forest floor and roots in the Pacific Northwest contribute additional 80 tons/ha of organic matter, with an estimated 21 tons/ha C and 476 kg/ha of N, for a C:N ratio of 44:1. Removal of a portion of this C pool would lower the overall C:N ratio stimulating N mineralization. However, the interaction of C and N pools across residue types has yet to be shown. Accurate assessments of organic matter and nutrients remaining on site are crucial to elucidating reasons for increases in forest productivity after organic matter removals.

Key words: productivity, N mineralization, Forest harvesting, nutrient removals