Effects of Immersion in Water on Deterioration of Wood from Five Species of Trees Used for Habitat Enhancement Projects

Abstract

Logs of standard dimensions from five species of trees were submerged in a stream to evaluate changes in strength and decomposition over a period of 5 years. Changes in structural properties occurred only for wood near the outer surface of the logs. Nearly all bark was removed from the logs within 12 months. Diameter loss for the five species ranged from 10.6 mm (western hemlock Tsuga heterophylla) to 21.8 mm (bigleaf maple Acer macrophyllum) after 5 years. Decreases in the density of surface wood for the five species ranged from 23% (red alder Alnus rubra) to 31% (western hemlock). Modulus of rupture, modulus of elasticity, and wood density did not change for wood more than 12 mm from the log surface for any of the species. Bigleaf maple exhibited the highest resistance to rupture, and western redcedar Thuja plicata exhibited the lowest. Western redcedar was also the most easily flexed. Microbial activity on the surface of the logs was highest at the start of the experiment and decreased rapidly with time of immersion. The two hardwood species (bigleaf maple and red alder) generally had higher levels of microbial activity than the conifer species (Douglas fir Pseudotsuga menzesii, western hemlock, western redcedar) from 12 months through 60 months of immersion. Differences in the rate of decomposition between conifer and hardwood logs were much less than in terrestrial environments. Our results suggest that hardwood logs can be used in stream enhancement projects where the wood will be submerged.

Effects of Large Woody Debris Addition on Stream Habitat and Brook Trout Populations in Appalachian Streams

“…However, the abundance of large pieces (>5 m length and >50 cm diameter) was lower than that reported by Flebbe & Dolloff (1995) for old growth streams. Also, the riparian areas of Appalachian streams once had a greater abundance of coniferous species such as red spruce (Picea rubens) and eastern hemlock (Tsuga canadensis) which decompose more slowly than hardwood species (Bilby et al, 1999). The high retention of LWD in our study coupled with the greater size of LWD in old growth systems, and differences between present and past species composition, suggest accumulations of LWD were much greater in the past than what is typically seen today even in areas where secondary growth of the riparian vegetation has matured.…”

Dynamics of wood recruitment in streams of the northeastern US

“…In-stream wood experiences frequent drying and wetting that increases decay rates. As a rule, conifers generally decay more slowly than hardwoods in streams (Melillo et al, 1983;Bilby et al, 1999;Spanhoff and Meyer, 2004), but some hardwoods, such as oaks (Quercus spp. ), also decay slowly.…”

Post-harvest windthrow and recruitment of large woody debris in riparian buffers on Vancouver Island

“…Height above stream could be used to evaluate lag time to recruitment, although as our correlations indicate, log diameter and decay state are contributing factors. Since logs immersed in water decay more slowly (e.g., Bilby et al 1999), it makes sense that the path by which logs enter the stream channel and the decay condition of the logs when they enter the water will make a difference to long-term condition and residency of the logs in-stream. These differences in log condition should be considered in riparian prescriptions and LWD modeling.…”

“…Variations in decomposition rates are highly dependent on species, size, wood chemistry, and submersed vs. partially submersed condition (Scherer 2004). Wood that is constantly submersed has a much slower decay rate than those pieces that are repeatedly wetted and dried (Bilby et al 1999). …”