Ab. Hairston-strang et Pw. Adams, Potential large woody debris sources in riparian buffers after harvesting in Oregon, USA, FOREST ECOL, 112(1-2), 1998, pp. 67-77
Twenty-one riparian buffers on private lands in Oregon were measured after
harvest using the 1994 revised Oregon Forest Practices Rules to determine t
heir ability to contribute large woody debris (LWD) to streams for fish hab
itat. On average, 51% of the trees retained in riparian buffers after harve
st currently would be capable of adding debris at least 20 cm diameter and
1.5 m length to the channel. Assuming 30% of trees are windthrown over 10 y
ears and that trees fall in random directions, the riparian buffers would b
e expected to add an average of 0.6 trees per 100 m (1.9 trees per 1000 ft)
of stream as LWD over 10 years. Analysis showed significantly greater LWD
inputs (p<0.05) when the likelihood of more frequent windthrow on riparian
terraces and of trees tending to fall downhill on steep slopes are consider
ed. On the sites investigated and with the information available, consideri
ng tree lean did not significantly increase expected LWD delivery. More dat
a on windthrow rates and direction are needed to confirm the analyses. Depe
nding on longevity, the expected frequency of LWD pieces could remain withi
n ranges observed in undisturbed stands. (C) 1998 Published by Elsevier Sci
ence B.V. All rights reserved.