Woody Debris as a Source of Fine Particulate Organic Matter in Coniferous Forest Stream Ecosystems

Abstract

The potential contribution of woody debris to fine particulate organic matter pools (0.45 μm ≤ FROM < 1 mm) was investigated in a coniferous forest stream ecosystem in western Oregon. The amount of wetted surface area of both large (>10 cm) and fine woody debris (1–10 cm) was 0.018 and 0.069 m2∙m−2 stream bed, respectively, during summer base flow. These values increase to 0.062 and 0.195 m2∙m−2 stream bed during winter flows. Studies of vertical distribution indicated that most fine wood is concentrated within 0.3 m of the stream bottom, while large wood is more evenly distributed up to 0.7 m. Lignin concentrations of large wood, soil, and FROM were very similar. Examination of FPOM samples with scanning electron microscopy revealed an abundance of wood-derived particles. Erosion rates of wood surfaces ranged between 0.5 and 11 mm∙yr−1 depending on decay state of the log. Using conservative estimates of processing rates, woody debris could be a source for approximately 90 g∙m−2∙yr−1 of FPOM, but with slightly a less conservative estimate, wood processing could easily generate several times the FPOM that is contributed by leaf and needle litter.

Coarse woody debris in temperate littoral zones: implications for biodiversity, food webs and lake management

“…Large pieces of wood introduced to aquatic systems are disintegrated by water movements leading to their breakage and erosion of the external surface (Harmon et al, 1986) which exposes the fresh wood substrate beneath to microbial degradation (Ward & Aumen, 1986). The initial breakdown of CWD in streams that weakens bark and wood tissue was evaluated at more than 3 years (Braccia & Batzer, 2008), while erosion rates of wood surfaces were estimated at 0.5-11 mm year -1 (Ward & Aumen, 1986). The physical fragmentation of CWD presumably progresses faster in flowing waters than in lakes where water dynamics are less intense.…”

“…Apart from physical degradation, CWD is subjected to microbial activity which systematically softens the wood, diminishes its volume (Harmon et al, 1986;Collier & Smith, 2003) and leads to increased production of fine organic matter (Ward & Aumen, 1986). Our knowledge on the contribution of microbes to this process in lakes is also scarce.…”

“…Thus, some CWD pieces can even persist in lakes for more than 1500 years and up to five millennia (Gennaretti et al, 2014). The increase in water temperature also enhances microbial metabolism, but on the other hand it can contribute to the reduction of oxygen saturation in water, which slows down the decay process (Ward & Aumen, 1986;.…”

Effects of Clear-cut Logging on Wood Breakdown in Appalachian Mountain Streams

“…Decomposing woody debris also appears to be an important site of nitrogen fixation and immobilization (e.g., Buckley and Triska, 1978;Aumen et al, 1983Aumen et al, , 1985aAumen et al, , 1985bBaker et al, 1983;Melillo et al, 1983) and, in addition woody debris creates habitat for aquatic organisms (Anderson and Sedell, 1979;Molles, 1982). Finally, fine particles eroded from the surface of decomposing wood may contribute significantly to the fine organic matter pool and provide a food source for downstream communities (Naiman and Sedell, 1979;Ward and Aumen, 1986).…”

Wood in different stream types: Epixylic biofilm and wood-inhabiting invertebrates in a lowlandversusan upland stream

“…Woody debris, moreover, is a source of fine organic matter and thus enriches the microbial and macrobial food webs of streams equally (Ward and Aumen, 1986). Abundance (Collier and Halliday, 2000;Johnson and Kennedy, 2003) and secondary production (Benke et al, 1984) of aquatic invertebrates inhabiting woody debris can be significantly higher than those colonizing sand *Corresponding author: bernd.spaenhoff@web.de and mud habitats.…”