Riparian areas that can be used as reference sites on which to base goals of vegetation restoration have not been documented in the Oregon Coast Range. I examined the composition and distribution of unmanaged riparian overstories in the central Oregon Coast Range along nine streams which have experienced minimal disturbance from Native Americans and no detectable disturbance since Euro- American settlement. I systematically located transects along nine streams, alternating sides of the streams. Each transect ran perpendicular to the stream and was subjectively divided into different vegetative and/or topographic units called landscape units (LU's). Rectangular plots were placed in each LU for characterization. LU l's were units that were closest to the stream, and LU2's were farther from the stream. Red alder was the most frequently found tree species on both terraces and slopes, and on all LU1 's. On LU2 terraces, alder was also the most frequently found species, but on LU2 slopes, Douglas-fir had the highest frequency. Red alder, Sitka spruce, and bigleaf maple were most commonly found occupying terrace sites, although bigleaf maple might be best adapted to conditions on terraces towards the base of slopes. Conversely, western hemlock and Douglas-fir were most commonly found occupying slope sites. Western redcedar was infrequently found, likely due to seed source limitations. Age distributions and tree frequencies indicate that near-stream communities (LUI 's) and terraces experience both intense and minor disturbances, and they experience both types of disturbances more frequently than communities farther from the stream (LU2's) or on slopes. According to fire records and reconnaissance, all streams appear to have been burned about 145 years ago. When equating a shade-intolerant tree age that was younger than this last catastrophic fire date with a disturbance, calculations of disturbance frequency using four different approaches indicate that between 2.6 and 4.5 disturbances per km per century large enough to regenerate trees occurred since the last stand-resetting fire along the nine creeks sampled. Fifty-two percent of near-stream communities (LU1's) and 23% of communities farther from the stream (LU2's) contained no trees. This could be due to small plot size and/or high shrub competition. The No Tree overstory type was most similar in topographic conditions to the Pure Hardwood overstory type, suggesting that red alder and/or bigleaf maple might have previously occupied the No Tree sites and have since died leaving no or little evidence. It appears that a large-scale, intense disturbance such as fire is needed to allow the recruitment of trees into the shrub-dominated, No Tree areas, especially shade-intolerant trees such as Douglas-fir. Any single definition of natural riparian vegetation is nearly impossible to construct, mainly because most ecosystems are composed of vegetation mosaics that are always changing in time and space. This change is associated with environmental variability, disturbance, and inter- and intra-specific competition. Also, differences in exogenous environmental conditions between pre-settlement times (circa 1850) and today, suggest that historic vegetation, ecological conditions, and resulting successional pathways might not mirror the vegetation, ecological conditions, and successional pathways of currently unmanaged riparian areas. Instead, results from this study, revealing the existence of mixtures of hardwoods, conifers, and no-tree areas over lengths of a stream, should be perceived as just one of many possibilities for a riparian overstory reference model.

This publication is aimed at watershed councils, government agencies, and specialists (foresters, wildlife and fisheries biologists) interested in riparian area silviculture or watershed restoration. It contains information on the ecology of riparian forests and a checklist of recommended practices and common mistakes made in restoring conifers to hardwood-dominated riparian forests. Our recommendations are based on 1) an evaluation of 34 riparian restoration projects spanning the Coast Range of Oregon, 2) three case studies of riparian restoration projects, and 3) ongoing research projects aimed at learning how to establish or release conifers in riparian forests. We found that project managers were choosing appropriate conifer species and stock types for planting, but the survival and growth of conifers in the understory were poor. Managers were underestimating the competitive power of shrub and hardwood communities. In some cases, conflicting objectives and lack of priority setting led to the failure of expensive projects. We hope this publication will assist managers in efforts to restore healthy riparian forests and dwindling fish stocks.

Riparian forests in the central Oregon Coast Range vary along a coniferous-deciduous compositional continuum. Variations in structure and composition affect water quality, fish and wildlife, biodiversity, timber, and aesthetics. A retrospective approach was taken in this study in order to understand and compare the structure, pattern, and history of an unmanaged, mature, deciduous-dominated riparian forest and an unmanaged, mature, coniferous-dominated riparian forest in the central Oregon Coast Range. Information on forest structure and pattern was acquired by mapping locations of all trees and snags (DBH 5cm) within a 2.0 ha and a 2.25 ha reference stand. The history of each stand was reconstructed through analyses of stand structure and composition, tree ages, spatial patterns of trees and snags, as well as detailed field observations. The structure and composition of the two forests is very different. Non-random patterns of trees and snags were observed at multiple scales. Although it is not possible to infer directly the process(es) responsible for observed patterns, point-pattern analysis is a useful tool to detect and describe intra- and interspecific patterns. Neither forest resulted from a single, stand-replacing fire. Instead, both sites were at least partially burned about 145 years ago, possibly in the same fire(s) which spread across an estimated 500,000 acres between the Siuslaw and Siletz Rivers in the mid-1800's (Morris 1934). There is good evidence to suggest that a second fire occurred at the coniferous-dominated site. One or two other fires may have occurred at the deciduous-dominated site. Evidence of wind, herbivory, flooding, pathogens, mass movement events, and non-stand replacing fire was observed at one or both of the sites. Seed source availability as affected by disturbance history may have played a role in forest development at both sites. The seed source availability of red alder relative to Douglas-fir may have increased with successive disturbance events at the deciduous-dominated, riparian forest. A local source of western hemlock seed may have been a key factor in the development of the coniferous-dominated, riparian forest.

Riparian zone vegetation can influence terrestrial and aquatic food webs through variations in the amounts, timing, and nutritional content of leaf and other litter inputs. Differences in vegetation composition and density, as well as riparian topography, may modulate the strength and quality of these inputs. Changes in inputs to small order streams affect the processes and condition of adjacent and downstream reaches based on the amount of particulate organic matter that is intercepted, retained, or exported. The central Oregon Coast Range provides an ideal opportunity to study how deciduous dominated and coniferous dominated riparian forests influence small streams within a matrix of managed riparian forests. In coastal Oregon riparian forests, we investigated lateral and vertical litter inputs to sixteen streams throughout a year and assessed how these inputs were influenced by density of deciduous dominated (mainly red alder (Alnus rubra)) or coniferous dominated (mainly Douglas-fir (Pseudotsuga menziesii)) overstory, understory, and lateral slope. Deciduous site vertical litter inputs (504 g m-2 yr-1 (95% CI: 447-562)) were estimated to exceed those from coniferous sites (394 g m-2 yr-1 (336-452)) by 110 g m-2 (29-192) over the full year. Annual lateral inputs (per meter of stream bank on one side) at deciduous sites (109 g m-1 yr-1 (76-143)) were estimated to be 47 g m-1 (1-95) more than coniferous sites (63 g m-1 yr-1 (29-97)). Annual inputs at coniferous sites were dominated by deciduous leaves, coniferous needles, and twig litter types. Deciduous leaves, deciduous-other, and small unidentifiable litter types dominated the annual inputs at deciduous sites. When evaluated temporally, November was the most pivotal month differentiating coniferous and deciduous site litter inputs. At deciduous sites, lateral litter movement increased with slope, but we did not see the same relationship for coniferous sites except in spring/summer months. Lateral inputs were quantitatively greatest in autumn months for both overstories, but were proportionately greater in winter. Regardless of slope, there was no indication that understory plants were obstructing annual lateral litter inputs or that annual lateral litter inputs were moving more than 5 m down slope. The percent nitrogen of annual total vertical litter was estimated to be 1.9% N (1.5-2.4) at deciduous sites and 1.2% N (0.8-1.7) at coniferous sites. Average % nitrogen of individual litter types were either greater in deciduous sites or not different among overstories, indicating that one can generally expect coniferous sites to have lower % N litter inputs overall. The annual nitrogen flux entering each meter-length (from above and both sides) of standard 4 m-wide streams at a deciduous sites (42 g N m-1 of stream) was twice that of coniferous sites (21 g N m-1 of stream). Annual total litter carbon flux into each meter-length of 4 m-wide streams was estimated to be 1154 g C m-1 of stream at deciduous sites and 880 g C m-1 of stream at coniferous sites. On average, autumn months (October-December) accounted for 46-59% of annual vertical C flux and 56-70% of annual vertical N flux at coniferous and deciduous sites. Our results suggest that red alder dominated riparian zones of the central Oregon Coast Range have significantly different quantity, timing, and quality of leaf litter inputs to streams than conifer dominated forests. Varied topography adjacent to streams with red alder dominated overstory has greater impact on the quantity, quality, and timing of total inputs than at coniferous sites. The cumulative effects from many small red alder dominated streams exporting to downstream reaches include more pronounced seasonality of litter delivery, with greater carbon and nitrogen loading annually, than expected from conifer dominated streams. Differences in overstory and topography in Oregon Coast Range riparian forests directly impact the delivery of nutrients and can affect the structure and composition of food webs in these ecosystems.