Characteristics and Geomorphic Effect of Wood in New Zealand's Native Forest Streams

Abstract

We surveyed the amount and geomorphic role of wood in 18 pristine native forest streams (channel width: 3-6 m) throughout New Zealand, and quantified the characteristics associated with piece stability and geomorphic effect. Wood piece numbers (18-66 per 100 m) and volumes (85-470 m 3 ha -1) were similar to or greater than found in many streams throughout the world. Forest type and geographic location had no discernable influence on wood abundance at a particular site, possibly due to the confounding influences of local features (e.g., tree fall regime) and methodology ('snap-shot' survey of a dynamic system). Half the pieces that were geomorphically active had moved, suggesting that stable pieces did not necessarily dominate geomorphic activity. Tree ferns were an important contributor to wood abundance in many of the streams studied. IntroductionNumerous studies have characterized the amount (volume, density, or biomass) (HAR- MON et al., 1986;HERING et al., 2000) and role of wood in stream (TRISKA and CROMACK, 1980;BILBY and BISSON, 1998). Initially, much of this research was conducted in the Pacific Northwest of North America (LAMMEL, 1972;FROEHLICH, 1973; see GREGORY, 2003 for a review), but has since been conducted in other regions in the USA (e.g., New England, BILBY and LIKENS, 1980; Georgia, WALLACE and BENKE, 1984; Wyoming, YOUNG, 1994; Colorado, RICHMOND and FAUSCH, 1995), and throughout the world (e.g., New Zealand, MOSLEY, 1981; Australia, GIPPEL et al., 1996; France and the United Kingdom, PIEGAY and GURNELL, 1997; Central Europe, HERING et al., 2000). A conclusion common to many of these studies is that wood is an important component of forest stream ecosystems. Wood in streams can influence channel morphology, hydraulics and sedimentation patterns, which in turn influence nutrient dynamics and habitat for aquatic organisms (BISSON et al., 1987; see GREGORY et al., 2003a for a recent review).The abundance and functional importance of wood appears to vary by region, possibly due to characteristics of the riparian forest species (e.g., maximum tree height) and regional hydrology (GURNELL et al., 2002). For example, streams located in the redwood-dominated forests of northern California contain large volumes of wood (up to 4360 m 3 ha -1) that exert tremendous influence on channel morphology (KELLER and TALLY, 1979;KELLER et al., 1995). In contrast, streams in the coniferous forests of central Sierra Nevada, California (only 400 km southeast of the redwood study streams) have relatively low amounts of wood (up to 89 m 3 ha -1), which exerted only a minor influence on stream morphology (BERG et al., 1998).

Dynamics of wood recruitment in streams of the northeastern US

“…Recent studies have also linked increased wood volume to greater nutrient cycling in headwater streams (Steinhart et al, 2000;Valett et al, 2002;Bernhardt et al, 2003;Warren et al, 2007). Given the importance of wood to stream ecosystems, the volume, abundance, characteristics, and function of wood in streams is of interest to both researchers and managers (Bisson et al, 2003;Bernhardt et al, 2005), and a number of studies have documented standing stocks and wood loading rates for streams in many regions of the country and the world (Richmond and Fausch, 1995;Meleason et al, 2005;Chen et al, 2006;Young et al, 2006). Few studies have evaluated the dynamics of wood in northeastern US stream ecosystems, leaving those engaged in stream research and management with little guidance regarding historic conditions and future changes in loading and abundance of large wood.…”

Spatial distribution and influence of large woody debris in an old-growth forest river system, New Zealand

“…In New Zealand, reach-scale studies to date have examined LWD loadings and influence on stream channel morphology in a number of stream systems, focusing on smaller sized streams in both indigenous and exotic pine plantation forests (Mosley, 1981;Evans et al, 1993;Baillie et al, 1999;Baillie and Davies, 2002;Meleason et al, 2005), but distribution patterns of LWD and morphological influence have not been studied at the catchment level. The objectives of this study were to (a) describe and quantify the amount and spatial distribution of LWD in a large catchment of old-growth forest and (b) determine the influence of LWD on channel morphology and habitat complexity.…”

Large wood abundance, distribution and mobilization in a third order Coastal mountain range river system, southern Chile

“…Values of about 100-200 m 3 ha −1 are distinctive of unmanaged mature hardwood forests (Harmon et al, 1986;Hering et al, 2000;Gurnell, 2003), but much lower LW storage characterize second to third order channels in heavily managed mountain basins in the Italian Alps (30-70 m 3 ha −1 ; Comiti et al, 2006), UK Highland Waters (44-88 m 3 ha −1 ; Gurnell et al, 2002) and northern Spain (0.4-4.8 m 3 ha −1 ; Diez et al, 2001). Analyzing wood storage data from El Toro and Tres Arroyos (Andes, Chile) and Buena Esperanza (Patagonia, Argentina) catchments and from New Zealand second order streams under Nothofagus native forests (94-101 m 3 ha −1 ; Evans et al, 1993;Baillie and Davies, 2002) and 3-6 m wide channels in pristine basins (85-470 m 3 ha −1 ; Meleason et al, 2005), Comiti et al (2008) proposed a reference minimum wood storage of about 100-120 m 3 ha −1 for mountain streams flowing through pristine Nothofagus forests in Chile, Argentina and New Zealand (these forests have a common origin and are a relict of the ancient southern hemisphere forests; Salmon, 1980;Marticorena and Rodriguez, 1995). LW storage found in the Vuelta de la Zorra seems to confirm this proposal.…”