Necromass Creation in an Amazon Forest: Examination of Undisturbed and Logged Forest Sites
Palace, Complex Systems Research Center, Morse Hall, University of New Hampshire, Durham, NH 03824 USA, firstname.lastname@example.org
Keller, International Institute of Tropical Forestry, USDA Forest Service, Rio Piedras, PR 00928-5000 USA, email@example.com
Silva, EMBRAPA Amazônia Oriental, PO Box 48, 66095-100 Belém, Pará, Brazil, firstname.lastname@example.org
The forests of the Amazon region are undergoing vast changes in land use that result in alterations to terrestrial carbon storage and exchange with the atmosphere. Necromass accounts for up to 20% of carbon stored in tropical forests and yet it is infrequently measured. We examined the creation of fallen necromass over four and a half years using repeated surveys in forest areas that had been subjected to reduced impact logging and in undisturbed forest at the Tapajos National Forest, Belterra, Brazil., We also estimated fallen coarse woody debris and standing dead stocks at two times during our study. For both creation and stock estimates of fallen necromass, we identified the source of each piece of necromass as either trunk, branch, or unidentifiable. We grouped fallen necromass into three diameter size classes; large (>10 cm), medium (5-10 cm) and small (2-5 cm) for both creation and stock estimates. We found significant differences in the source proportion between the stock and creation estimates, as well as differences between undisturbed forests and forests that had been logged with reduced impact techniques. The annual flux into the necromass pool in undisturbed forest sites of 6.7 (0.8) Mg ha-1 y-1 was not significantly different from the flux in a RIL sites of 8.5 (1.3)Mg ha-1 y-1 . With the assumption of steady-state, we estimated decay rates for fallen necromass in undisturbed forests to be 0.10 y-1 for large, 0.30 y-1 for medium and 0.42 y-1 for small size classes.