Composition Of Riparian Forests Research Articles

Structure and composition of unmanaged riparian forests in the coastal mountains of Oregon, U.S.A.

Structure and composition of unmanaged riparian forests in the coastal mountains of Oregon, U.S.A.

Structure and composition of riparian forests with special reference to geomorphic site conditions along the Tokachi River, northern Japan

The structure and composition of riparian forests were examined along the Tokachi River, northern Japan. Both the hydrogeomorphic gradient and the temporal gradient were analyzed in attempt to explain the present pattern of riparian forests. The stability of floodplain surfaces was estimated on the basis of the elevation above the riverbed and the distance from the river channel. The characteristics of the substratum on which trees were established were also examined by excavation of buried sediment. The results indicated that soil moisture and organic content increased while the size of particles in the substratum decreased with increased elevation and distance from the river channel. Gradient analysis was employed to examine the distribution of dominant species, such as Alnus hirsuta, Toisusu urbaniana, Populus maximowiczii, Picea jezoensis and Abies sachalinensis. The relative dominance of each could be arrayed across the elevation gradient. Although the three broad-leaved pioneers dominated bars and floodplains near the river channel, their modes shifted from lower to higher elevation and amplitudes of distribution curves decreased in the following order: A. hirsuta, T. urbaniana, P. maximowiczii and conifers, which were located on the highest floodplains. Sites could be divided into three classes in terms of stability. There were fewer species at active sites, which favored the three pioneer species, but species richness and diversity increased with stand age. Semi-active and stable sites were more diverse with the establishment of conifers and other broad-leaved trees, which included upland species. However, species richness peaked and then decreased after trees reached 50 to 60 years of age. The growth of dwarf bamboo and the development of conifer-dominant stands impeded the establishment of other species, thereby reducing species richness and diversity in mature stands. Chronologically, floodplains could be differentiated into high- and low-frequency zones of flood disturbance, with pioneer species occupying the former, and late successional species found largely in the latter.

Linkages between riparian forest composition and shredder voltinism

Life history patterns and seasonal growth rates of eleven shredder species inhabiting an Appalachian mountain stream (Pennsylvania, U.S.A.) were determined and conceptually linked to the species composition of the riparian forest. Thirty-two woody plant species were represented in the riparian forest, with a near-equal compliment of foliage cover within each of the three leaf processing categories (slow, medium, fast). Relative cover of individual species was highly correlated with the proportions of standing stock biomass of individual species of stream leaf detritus. With two exceptions, each shredder species was univoltine; Tallaperla maria exhibited a semivoltine life cycle, while Pteronarcys proteus appeared to require four years to complete nymphal development. Paracapnia angulata, Taeniopteryx maura, Tallaperla maria, Lepidostoma (Nosopus) modestum group sp., Pycnopsyche gentilis, P. luculenta, and Brillia flavifrons exhibited either autumn and/or winter growth. In contrast, Amphinemura nigritta, A. wui, and L. (Mormomyia) sp. displayed either spring and/or summer growth. Overall, the study stream appears to be an appropriate system for analyzing the riparian-shredder link because (1) the riparian assemblage is diverse within a broad range of leaf-processing rates, and (2) the shredder guild is correspondingly diverse with a wide array of seasonal growth patterns.

In-stream large woody debris loading and riparian forest seral stage associations in the southern Appalachian Mountains

Large woody debris (LWD) is an important ecological component of mountain streams. However, the relation of LWD loading and riparian forest composition is poorly understood in the southern Appalachians. In this study, 500-m reaches of 11 riparian forest–stream systems representing a 300-year sere were inventoried and measured to obtain quantitative estimates and descriptions of in-stream LWD. Loading volumes ranged from 7.1 to 31.2 m3/100 m of stream, or between 3.6 and 13.2 kg/m2. LWD loadings were highly variable during midseral stages of plant community succession, primarily because of the wide range in loading of American chestnut (Castaneadentata (Marsh.) Borkh.). Loadings increased linearly in late-successional through old-growth systems over a 165-year interval. Eastern hemlock (Tsugacanadensis (L.) Carrière) and American chestnut were the most dominant carry-over LWD species in midsuccessional stream systems. Loading of eastern hemlock LWD increased from midsuccessional through old-growth stages as the species became dominant in the riparian forest. Without carry-over debris, LWD loadings would be extremely low in midsuccessional stream systems. American chestnut was a major component of LWD in midsuccessional stream systems, despite the fact that it has been unavailable for recruitment for decades.

Large woody debris, physical process, and riparian forest development in montane river networks of the Pacific Northwest

We present a conceptual biogeomorphic model of riparian forest development in montane river networks. The role of physical process in driving the structure, composition, and spatial distribution of riparian forests is examined. We classify the drainage network into disturbance process-based segments including: (1) debris-flow and avalanche channels, (2) fluvial and debris-flow channels, and (3) fluvial channels. Riparian forests are shown to be significant in the development of channel morphology through the stabilization of active floodplains and as sources of large woody debris (OLWD). LWD is operationally defined as wood > 0.1 m diameter and > 1 m length. LWD plays a key role in the development of montane riparian forests. LWD deposited in the active channel and floodplain provides sites for vegetation colonization, forest island growth and coalescence, and forest floodplain development. Riparian forest patterns parallel the distribution of hillslope and fluvial processes through the network. Riparian forest structure:, composition, and spatial distribution through the network are driven by the major disturbance processes including: (1) avalanches, (2) debris-flows, and (3) flooding. Riparian forest patterns also reflect the action of LWD in the organization and development of forested floodplains in gravel bedded montane river networks. The focus of our examples are montane river networks of the Pacific Northwest, USA.

Vegetative Structure and Composition of Southern Appalachian Riparian Forests

HEDMAN, CRAUG W. (Southlands Experiment Forest, International Paper, Bainbridge, GA 31717) AND DAvID H. VAN LEAR (Department of Forest Resources, Clemson University, Clemson, SC 29634-1003). Vegetative structure and composition of Southern Appalachian riparian forests. Bull. Torrey Bot. Club 122: 134-144. 1995.-Vegetative characteristics of twelve Southern Appalachian riparian forests were sampled as part of a larger study which examined functional attributes of riparian zones. Riparian forests were representative of the mixed mesophytic forest, eastern hemlock forest, and transitions between these types. Earlyand mid-successional stages were generally dominated by an overstory of pioneering shade-intolerant species and had an even-aged structure. The diameter distribution of these relatively young stands of mixed species was typically inverse J-shaped. Late-successional and old-growth stages were dominated by shade-tolerant or moderately tolerant overstory species and were uneven-aged. Diameter distribution in these older stands approximated a rotated sigmoid curve. Rhododendron (Rhododendron maximum L.) was the dominant understory species and controlled understory and midstory composition. Characterization of riparian forests in different stages of succession will help understanding of vegetative processes and forms the basis of subsequent ecological studies of riparian functional dynamics.

Relationships between bird assemblages, vegetation structure, and floristic composition of mosaic patches in riparian forests

The vegetation structure and the plant taxonomic composition of riparian forests, together with the birds, were mapped and analysed. The forest plots were 100 m wide and 1 600 to 2 000 m long, and were located near lake Grand Lieu, Brittany, France. The plots were not homogeneous, but a mosaic of different vegetation types. The patches of the same vegetation type were combined. We recognized 21 vegetation types, but we retained only 16 that were of sufficient size to neutralize species-area effects. Variables of vegetation structure as well as variables of plant taxonomic composition associated with plant succession showed the strongest correlations with the variables of bird community. Disturbances caused by forestry is correlated with reduced bird species richness in forest patches of all ages. Canonical correspondence analyses of the bird data constrained by the vegetation data allowed us to identify that variables that explain most of the variance in bird data are those related strongly to succession. Partial CCA revealed the relative influence of plant structure versus floristic variables as well as their combined influence on bird community structure (17, 17, 21 % respectively). When the same analysis is applied after removal of early-successional vegetation types, the importance of floristic variables increased.

Observed and modeled directional change in riparian forest composition at a cutbank edge

Lateral migrations of river meanders create transient, spatially transgressive edges where the advancing cutbank edge encroaches upon interior floodplain forest communities. This spatial movement of edge toward the forest interior should initiate directional changes in species composition within a forest plot as it is affected by a changing microclimate and hydrological regime. We found that cutbank edge and forest interior sites in an Iowa floodplain contained markedly different plant assemblages. Species commonly associated with later stages of succession dominated interior sites while cutbank edge sites favored secondary, successional species. Assuming that the cutbank edge sites once contained vegetation similar to that surveyed in the floodplain interior, the observed changes in community structure accompanying channel migration are suggestive of retrograde succession, or retrogression. To link cutbank erosional processes with retrogressional processes, we modified a computer simulation model already in use for floodplain environments. We incorporated the changing edge effects and compared model projections with the data collected from the field sites using detrended correspondence analysis. Without changes, the simulation projected a site compositionally similar to the sampled interior forest. When the changes were initiated, the simulated site progressively took on compositional characteristics similar to the riparian edge sites. Because we included only those forcing functions that would be initiated by cutbank erosion, the model supports the hypothesis that the spatially progressive edge effect results in a directional change in forest community composition analogous to retrogression. Our results demonstrate an interesting linkage between successional and fluvial-geomorphic processes and indicate that site dynamics may be controlled differently in landscapes where sites are progressively created and destroyed than where recurrent disturbances affect the same site.

Browse selection by beaver: effects on riparian forest composition

Beaver (Castorcanadensis) herbivory has both immediate and long-term effects on biomass, structure, and composition of riparian forests. Intense beaver foraging of trembling aspen (Populustremuloides Michx.) decreased tree density and basal area by as much as 43% within ~ 1-ha forage zones surrounding two beaver ponds in northern Minnesota. Maximum diameter of trees cut was 43.5 cm; average aspen stem diameter cut was 13.9 and 10.2 cm at the two ponds. Woody biomass harvested per beaver averaged 1.4 Mg•ha−1•year−1 over a 6-year foraging period. Most wood harvested was left on site or used in dam construction, rather than consumed. Selective foraging by beaver decreased the relative importance of preferred species (i.e., P. tremuloides) and increased the importance of avoided species (i.e., Alnusrugosa (Du Roi) Spreng., Piceaglauca (Moench) Voss), with long-term implications to forest succession and dynamics.

Stream-Grade Variation and Riparian-Forest Ecology Along Passage Creek, Virginia

U.S. Geological Survey, National Center, M.S. 461, Reston, VA 22092 Hupp, CLIFF R. (U.S. Geol. Surv., National Center, Mail Stop 461, Reston, Virginia 22092). Stream grade changes and riparian-forest ecology along Passage Creek, Virginia. Bull. Torrey Bot. Club 109: 488-499. 1982.-Passage Creek, in northwestern Virginia, flows on relatively nonresistant shales, then cuts through a gorge underlain by resistant sandstone. In the gorge, the stream gradient steepens, the size of bed material increases, a braided channel forms, and riparian-forest composition and growth form changes relative to areas outside the gorge. Effects of flooding are intensified within the gorge and revealed in the pattern and deformation of streamside vegetation. Increased stream gradient within the gorge provides for high stream power and coarse sediment deposition relative to the flood plain outside the gorge. A more diverse upland forest grows on the flood plain in the gorge. The riparian forest in the gorge may be an example of a nonequilibrium forest, resulting from periodic disturbance by destructive floods. Recognition of vegetation patterns resulting from such disturbances may be useful in detection of potential flooding.