Carex Lyngbyei Research Articles

Topographic conditions as governing factors of mire vegetation types analyzed from drone‐based terrain model

AbstractQuestionsPrevious studies have shown that mire vegetation responds to fine‐scale differences in topography; however, very few studies have examined the relationship between multiple topographic conditions and vegetation distribution patterns by using topographic information with a resolution finer than microtopographic patches of sub‐meter scale in mires. Is it possible to predict vegetation distribution patterns in a mire using topographic information derived from drone imagery? How do topographic conditions affect the emergence of vegetation types?Location3 km2 of sloping mire in eastern Hokkaido, northern Japan.MethodsDigital surface models (DSMs) and orthomosaics were created using an affordable drone (Phantom3 advanced) and photogrammetry. We calculated 23 variables reflecting topographic conditions from DSMs. The locations of four vegetation types (Moliniopsis japonica–Eriophorum vaginatum, ME; Moliniopsis japonica–Carex lasiocarpa, MC; Sphagnum fuscum–Ledum palustre, SL; and Carex lyngbyei–Thelypteris palustris, CT) were recorded by field survey and orthomosaics. Random forest models that predicted vegetation types from topographic variables were created and we evaluated the prediction accuracy, importance of variables and effect of variables on the occurrence probability of the vegetation types.ResultsAll predictive indicators (recall, precision, overall accuracy, kappa) were very high (>0.9). Important variables for modeling were altitude, relative height to the surroundings, slopes at a scale of several 10 m, soil wetness index and terrain ruggedness. Each vegetation type appeared under different topographic conditions; altitude was a key factor in ME and MC, and slope in CT. SL showed patchy distribution predictions on hummocks.ConclusionsVegetation distribution in the mire was strongly related to topographic information based on the DSMs. Analysis of the variable effects indicates that the emergence of the vegetation types was explained by a combination of multiple topographic conditions. This approach has the outstanding advantages of obtaining many survey points quickly and retrieving topographic conditions difficult to measure using on‐ground field surveys.

Ecohydrology of wetland plant communities along an estuarine to tidal river gradient

AbstractAbiotic filters that interact with wetland plant communities along tidal–fluvial gradients are highly dynamic, and understanding their quantitative thresholds and relationships to interspecific competition is important during an era of sea‐level rise and watershed hydrologic change. Yet, landscape‐scale studies of major coastal rivers from the river mouth to the head of tide, such as this study, remain rare. Here, we develop a new predictive framework for estuarine–tidal river research and management using a river‐specific low‐water datum and the wetland inundation indicator SEVg, the growing‐season sum exceedance value of hourly surface‐water depth. The distribution and variability of the wetland species pool (n = 203) on the 234 river kilometer (rkm) lower Columbia River and estuary floodplain are described for the first time. 4,940 quadrats at 50 marshes were surveyed (2005–2016). Throughout the estuarine–tidal river system, SEVg was well suited to describe the wetland inundation regime and its variability based on the combination of longitudinal river position and elevation. SEVg increased significantly landward. Two primary wetland inundation regimes were identified: the seaward‐tidal, usually greatest during the winter months, and landward‐fluvial, greatest during the growing season. Nearest the ocean, salinity is the abiotic factor limiting species richness and non‐native species. Farther upriver, the daily, seasonal, and interannual variability of the wetting and drying cycle encourage disturbance‐tolerant species and non‐natives and limit the number of hydrophytes and total vegetative cover. Hence, the average between‐year similarity of site‐scale areal cover significantly decreased landward. Hierarchical cluster analysis indicated five vegetative groups and five ecohydrologic zones between rkm 0 and 234 were discriminated with 76 significant species–zone associations. All zones had unique indicator species. Species with high indicator values were Carex lyngbyei throughout the estuarine zones, and Eleocharis palustris, Sagittaria latifolia, and the invasive non‐native Phalaris arundinacea in the upper estuarine and lower, middle, and upper tidal river zones (IV > 0.90). Competition from C. lyngbyei nearest the ocean and P. arundinacea in the tidal river was associated with reduced species richness when total cover was >65%. This framework of filters informs the design and prediction of future wetland plant communities on coastal river floodplains.

Testing the interactive effects of flooding and salinity on tidal marsh plant productivity

Tidal wetlands support plant communities that facilitate carbon storage, accrete soil, and provide habitat for terrestrial and aquatic species. Climate change is likely to alter estuaries through sea-level rise and changing precipitation patterns, although the ecological responses are uncertain. We were interested in plant responses to physiological stress induced by elevated water salinity and flooding conditions, which may be more prevalent under climate change. . We used a greenhouse experiment and factorial flooding (1, 12, 24, and 48 % time) and salinity (0, 5, 15, 30 PSU) treatments to evaluate the productivity responses of three emergent herbaceous species (Carex lyngbyei, Triglochin maritima, and Argentina pacifica) common to tidal marshes of the Pacific Northwest, USA. We measured weekly changes in plant height and final above and belowground biomass for all species after 10 weeks. Increased salinity reduced final above and belowground biomass significantly in all three species, with A. pacifica responding the most, followed by C. lyngbyei and T. maritima. Increased flooding also reduced total biomass in A. pacifica and T. maritima. There was a significant response in C. lyngbyei aboveground biomass and A. pacifica height to the flooding-salinity interaction. These results indicate emergent plant community composition may change in response to novel climate conditions in estuaries, driven by distinct physiological tolerances to salinity and flooding, and highlight the importance of considering multiple climate drivers when projecting ecosystem change. This may be especially true for estuaries that currently have prolonged freshwater phases like those in the Pacific Northwest.

Relationships between Salt Marsh Vegetation and Surface Elevation in Coos Bay Estuary, Oregon

Salt marsh habitats support a diverse array of estuarine species but are vulnerable to increased inundation resulting from sea-level rise. In order to characterize relationships between vegetation and elevation and inform assessments of risk to salt marsh communities from projected sea-level rise, we collected vegetation and elevation data at 42 salt marsh sites in Coos Bay Estuary, Oregon. For 1-m2 plots along transects from the bayside edge to the upland, we recorded height and percent cover of all plant species present. We determined plot location and elevation at 1-m intervals with a Trimble Pathfinder Pro XRS differential GPS and TOPCON GTS223 Total Station for comparison with existing LiDAR. Cluster analysis distinguished six vegetation groups. Two low marsh groups (average elevation 1.74 and 1.91 m) were characterized by swampfire (Sarcocornia perennis) with an average height of 31 cm, and saltgrass (Distichlis spicata) with an average height of 22 cm. Plots in the high marsh groups had average elevations ranging from 2.21 to 2.57 m and were characterized by tufted hairgrass (Deschampsia cespitosa) and Oregon gumweed (Grindelia stricta var. stricta), with an average height of 50 cm and 43 cm, respectively. Mid-marsh groups (average elevations of 2.01 and 1.99 m) were dominated by Lyngbye's sedge (Carex lyngbyei) with an average height of 64 cm. The data collected along these transects allowed us to assess LiDAR elevation accuracy, identify sites where LiDAR data require correction, and provide species-specific height data for correction of LiDAR in areas of dense vegetation.

Potential effects of sea-level rise on plant productivity: species-specific responses in northeast Pacific tidal marshes

Coastal wetland plants are adapted to varying degrees of inundation. However, functional relationships between inundation and productivity are poorly characterized for most species. Determining species-specific tolerances to inundation is necessary to evaluate sea-level rise (SLR) effects on future marsh plant community composition, quantify organic matter inputs to marsh accretion, and inform predictive modeling of tidal wetland persistence. In 2 macrotidal estuaries in the northeast Pacific we grew 5 common species in experimental mesocosms across a gradient of tidal elevations to assess effects on growth. We also tested whether species abundance distributions along elevation gradients in adjacent marshes matched productivity profiles in the mesocosms. We found parabolic relationships between inundation and total plant biomass and shoot counts in Spartina foliosa and Bolboschoenus maritimus in California, USA, and in Carex lyngbyei in Oregon, USA, with maximum total plant biomass occurring at 38, 28, and 15% time submerged, respectively. However, biomass of Salicornia pacifica and Juncus balticus declined monotonically with increasing inundation. Inundation effects on the ratio of belowground to aboveground biomass varied inconsistently among species. In comparisons of field distributions with mesocosm results, B. maritimus, C. lyngbyei and J. balticus were abundant in marshes at or above elevations corresponding with their maximum productivity; however, S. foliosa and S. pacifica were frequently abundant at lower elevations corresponding with sub-optimal productivity. Our findings show species-level differences in how marsh plant growth may respond to future SLR and highlight the sensitivity of high marsh species such as S. pacifica and J. balticus to increases in flooding.

Applying and testing a predictive vegetation model to management of the invasive cattail, Typha angustifolia L., in an oligohaline tidal marsh reveals priority effects caused by non-stationarity

Effective tidal marsh restoration requires predictive models that can serve as planning and design tools to answer basic questions such as which, if any, plant species will colonize a proposed restoration site. To develop such a tool, a predictive model of oligohaline tidal marsh vegetation was developed from reference marshes in the Skagit River Delta (Washington, USA) and applied to a 1.1-ha restoration treatment site. Probability curves for the elevational distributions of common marsh species were generated from RTK-GPS point samples of reference tidal marshes. The probability curves were applied to a LIDAR-derived digital elevation model to generate maps predicting the occurrence probability of each species within treatment and control sites. The treatment and control sites, located within a recently restored area that had been diked but never completely drained, were covered by a mono-culture of non-native Typha angustifolia L. (narrow-leaf cattail) growing 40–60 cm lower in elevation than in the reference marsh. The T. angustifolia was mowed repeatedly in the treatment site to allow colonization by predicted native marsh species. Four years after mowing, T. angustifolia was replaced on 60 % of the treatment site by native sedges (Carex lyngbyei, Eleocharis palustris), consistent with the predictive vegetation model; the control site remained covered by T. angustifolia. The mowing experiment confirmed that pre-emptive competition from T. angustifolia was preventing vegetation recovery in the restoration site following dike removal, and implied that some vegetation species may be refractory to environmental change, such as dike removal or sea-level rise, because of differences in recruitment and adult niches.

Environmental Determinants of Emergent Macrophyte Vegetation in Pacific Northwest Estuarine Tidal Wetlands

We investigated whether within wetland environmental conditions or surrounding land cover measured at multiple scales were more influential in structuring regional vegetation patterns in estuarine tidal wetlands in the Pacific Northwest, USA. Surrounding land cover was characterized at the 100, 250, and 1,000 m, and watershed buffer scales. Vegetation communities were characterized by high species richness, lack of monotypic zonation, and paucity of invasive species. The number of species per site ranged between 4 and 20 (mean ± standard deviation = 10.2 ± 3.1). Sites supported a high richness (mean richness of native species 8.7 ± 2.8) and abundance of native macrophytes (mean relative abundance 85 % ± 19 %). Vegetation assemblages were dominated by a mix of grasses, sedges, and herbs with Sarcocornia pacifica and Distichlis spicata being common at sites in the oceanic zone of the estuary and Carex lyngbyei and Agrostis stolonifera being common at the fresher sites throughout the study area. The vegetation community was most strongly correlated with salinity and land cover within close proximity to the study site and less so with land cover variables at the watershed scale. Total species richness and richness of native species were negatively correlated with the amount of wetland in the buffer at all scales, while abundance of invasive species was significantly correlated to within wetland factors, including salinity and dissolved phosphorus concentrations. Landscape factors related to anthropogenic disturbances were only important at the 100-m buffer scale, with anthropogenic disturbances further from the wetland not being influential in shaping the vegetation assemblage. Our research suggests that the traditional paradigms of tidal wetland vegetation structure and environmental determinants developed in east coast US tidal wetlands might not hold true for Pacific Northwest wetlands due to their unique chemical and physical factors, necessitating further detailed study of these systems.

Ecophysiological mechanisms characterising fen and bog species: focus on variations in nitrogen uptake traits under different soil–water pH

Although the productivity and nitrogen (N)-use traits of mire plants differ dramatically between fens and bogs, soil N richness does not necessarily differ, whereas the soil-water pH is distinctly lower in bogs than in fens. The ecophysiological mechanisms underlying these relations are unclear. To assess the relative availability of N forms in relation to soil-water pH, we focused on the net N uptake rate per unit root weight (NNUR), glutamine synthetase activity and nitrate reductase activity, and performed reciprocal transplant experiments with the seedlings of fen (Carex lyngbyei) and bog (C. middendorffii) sedge species in intact habitat sites. The soil-water pH was clearly lower at the bog site, but the NH(4) (+), NO(3) (-) or dissolved organic-N concentrations did not differ between the fen and bog sites. The activity of both enzymes for inorganic-N assimilation did not differ among the sites and species. However, the fen species grown at bog sites showed a drastic decrease in the NNUR, suggesting a suppression of organic-N uptake. The bog species showed no NNUR difference between the sites. These results indicate that inorganic-N availability does not differ between the two habitats, but organic-N availability is lowered in a low-pH bog, particularly in the case of fen species. Therefore, the relative availability of N forms shows species-specific variations that depend on the differences in the soil-water pH of root zone, even at similar N richness, which would play a key role in plant distribution strategies in relation to the fen-bog gradient.

VEGETATION RESPONSE AND SEDIMENT POLYCYCLIC AROMATIC HYDROCARBON ATTENUATION IN A CAREXMARSH IN HOWE SOUND, BRITISH COLUMBIA, CANADA FOLLOWING A SPILL OF BUNKER C Fuel Oil

ABSTRACT A spill of Bunker C fuel oil in Howe Sound, British Columbia, Canada in August 2006 affected approximately 10.5 acres (4.2 hectares) of marsh habitat unique to the Pacific Northwest. A cleanup approach to reduce impacts from response actions was balanced with a desire to remove all residual oil. Cleanup techniques that were used include flushing, cutting, raking, passive sorbent collection, natural recovery, and manual excavation (sediment removal). Evaluation of the habitat response relative to oiling conditions and treatments was undertaken by examining vegetation indices in treatment and control areas and temporal changes in sediment concentrations of poly cyclic aromatic hydrocarbons (PAHs). One year post-spill results suggest that the amount or degree of oiling on the dominant vegetation, Carex lyngbyei and ?leocharis palustris, had little or no apparent effect, or was insignificant in comparison to the impact of the treatment. Vegetation cutting alone had no positive or negative effect on vegetation recovery indices. Treatments which were aggressive in physically disturbing the sediments and root systems of the marsh (heavy trampling, heavy scraping, excavation and/or excessive trampling) retarded vegetation recovery in oiled and unoiled habitats and prolonged oil persistence in comparison to non aggressive treatment, vegetation cutting alone or natural recovery. Mechanical damage was the best predictor of ?AH persistence.

Relative utility of foraminifera, diatoms and macrophytes as high resolution indicators of paleo-sea level in coastal British Columbia, Canada

A multiproxy analysis was carried out on diatom, foraminiferal and macrophyte assemblages across the saltmarsh at Zeballos, Vancouver Island, British Columbia. To determine which group, or combination of groups provided the most accurate elevational zonations, 36 stepwise multiple linear regressions (SMLR) were carried out using a variety of data transformations on an elevational training set. Adjusted R 2 values yielded statistically significant results in all analyses as follows: foraminifera (0.658–0.870); diatoms (0.888–0.974); macrophytes (0.671–0.844); foraminifera/diatoms (0.941–0.981); foraminifera/diatoms/macrophytes (0.958–0.993). The most realistic SMLR results were obtained when data transformations comprised of (ln) normalized fractional abundance data was carried out on species present in statistically significant numbers (NrfaEQ). Of the individual proxies assessed, diatoms yielded the most significant adjusted R 2 results, with the low marsh diatom Achnanthes hauckiana being one of the most important predictor variables (pv's). Amongst the foraminifera, the low marsh species Miliammina fusca and high marsh Balticammina pseudomacrescens were determined to be the most significant pv's. For macrophytes, the low marsh species Carex lyngbyei, the high marsh species Juncus balticus, Shannon–Wiener Diversity Index (SDI) and absence of plant cover on the tidal flat were the most important pv's. As SMLR analysis of all individual groups and combinations of groups yielded statistically significant results, the choice of proxies, or combinations of proxies that are suitable for paleo-sea level research is at the discretion of the researcher.

Effects of scale‐dependent factors on herbaceous vegetation patterns in a wetland, northern Japan

Herbaceous vegetation was examined in an Otanoshike wetland in northern Japan to clarify the relationships between vegetation patterns and environmental factors with different scales. Alders (Alnus japonica) have recently invaded and might modify the herbaceous vegetation. In total, 150 50 × 50 cm plots were established on the transitional areas between alder thickets and grassy marshland. Cover was measured for the vascular plant taxa, and canopy area, number of stumps, number of mounds, water depth, elevation difference, litter thickness, soil organic matter, and soil pH were measured in each plot. TWINSPAN cluster analysis classified four vegetation groups: (i), grasslands represented by Phragmites australis, Trientalis europaea, Lythrum salicaria, and Hosta rectifolia; (ii), Calamagrostis langsdorfii, and Polygonum thunbergii grasslands with Spiraea salicifolia; (iii), reed swamp dominated by Phragmites australis, and (iv), marshland dominated by Carex lyngbyei. Canonical correspondence analysis indicated that water depth primarily divided vegetation groups 1–2 and 3–4. Alder established in drier sites mostly by re‐sprouting, and the canopy affected light and soil conditions on the ground surface. The second axis of canonical correspondence analysis was related to the canopy area and soil pH, and explained the vegetation differentiation between groups 1 and 2, and groups 3 and 4. In conclusion therefore, scale‐dependent or hierarchical variables affected the vegetation patterns in different ways, that is, the herbaceous vegetation was first differentiated by water depth that was corresponding to alder establishment on a large scale, and subsequent light and soil conditions were second determinants on a small scale.

A modern analogue for plant colonization of palaeotsunami sands in Cascadia, British Columbia, Canada

The sediment stratigraphy of a modern analogue for pioneer-plant colonization of palaeotsunami sands near Tofino, British Columbia, Canada, shows that a sand outcrop is continuous with a buried sand stratum deposited by tsunamis of the ad 1700 Cascadia earthquake. Plants growing on the sand outcrop form a low-marsh community that includes Triglochin maritimum, Salicornia virginica, Spergularia canadensis, Puccinellia pumila and Plantago maritima. In contrast, low marshes on muddy substrates include only Carex lyngbyei. Although Carex lyngbyei colonizes low marsh on mud, it is restricted to middle marsh or higher elevation communities on sand. With two-way indicator species analysis (TWINSPAN) and detrended corre spondence analysis (DCA), plant cover-abundance clearly distinguishes sandy from muddy low marsh, a finding that suggests that particle size influences plant colonization. TWINSPAN and DCA show that pollen spectra of the sandy marsh surface resemble fossil pollen of sediments that immediately overlie buried sand deposits. Grain size of intertidal deposits influences primary plant succession, and species on sand respond to relative sea-level change just as those on mud. Pollen assemblages in surface sediments reflect plants growing nearby, and taphonomic distortion of the pollen spectrum is minimal at this locality. These observations suggest that past co-seismic subsidence can be estimated by use of pollen assemblages as proxy indicators of elevation relative to sea level.

Reduced soil contributes to the anomalous occupation of dwarf communities in N‐richer habitats in a cool‐temperate mire

Spatial patterns of the oxidation–reduction potential (Eh) of soil, water level and chemistry were examined in the fen area of the Tohfutsu mire, northern Japan, where horse pasturage has been carried out throughout the growing season every year. The fen vegetation consisted mosaically of communities mono‐ or codominated by Eleocharis kamtschatica, Iris setosa and Carex lyngbyei. The highest concentration of total dissolved nitrogen of soil water was observed in the dwarf community dominated by E. kamtschatica with smaller biomass, whereas the nutrient level was lower in the community monodominated by C. lyngbyei with larger biomass. Principal component analysis denoted well that Eh, N, K, and pH contributed to the differentiation of these communities significantly. During the growing season that was investigated, the highest nitrogen concentration was observed in midsummer, when plants are expected to absorb nutrients intensely, indicating that the supply of dissolved nitrogen far exceeded the nutrient uptake of plants. Multiple habitats with reduced soil were formed by submergence and by an excess of nitrogen due to pasturage, and the soil reduction indirectly inhibited the incursion of species with large biomass at such sites. It was demonstrated that soil Eh contributed to the anomalous pattern of vegetation where the supply of available nitrogen exceeds the uptake by plants.

Vegetation, hydrology, and development of a coastal mire in Hokkaido, Japan, affected by flooding and tephra deposition

Mires in coastal lowlands in Hokkaido, northern Japan, have repeatedly been affected by flooding events and tephra (aerially transported volcanic ejecta) deposition during their development. Vegetation, hydrology, and stratigraphy of Kiritappu Mire in eastern Hokkaido were investigated along two transects and are discussed in relation to disturbance by mineral deposition. The vegetation pattern showed little relation to past geologic events. Five plant communities, two of which (A and C) could be further divided into subgroups, were distinguished (A, Alnus japonica - Spiraea salicifolia community; B, Sasa chartacea community; C, Myrica gale var. tomentosa - Sphagnum fuscum community; D, Carex lyngbyei community; E, Carex subspathacea - Aster tripolium community). Water levels, pH, electric conductivity, and ionic composition of groundwater and surface water were measured in communities A-C. Mean water levels were similar in communities A and C; in community B, it was lower. The pH was higher in community A than in communities B and C. Ion concentrations were influenced by sea water at some sites. Plant macrofossils and ash contents of 31 cores were analysed. Sedge roots were the dominant peat component, often mixed with remains of Phragmites australis, Sphagnum spp., and Polytrichum juniperinum var. strictum. Ash contents were high, and up to nine different mineral layers consisting of tephra, sand, silt, and clay were detected. In some cases, mineral deposition induced changes in the macrofossil composition of the peat. However, in a greater number of cases, no changes in the macrofossil composition were found at the mineral layers, and most shifts were not related to mineral deposition.Key words: mire, vegetation, hydrology, disturbance, flooding, tephra.

Created and Restored Marshes in the Lower Fraser River, British Columbia: Summary of their Functioning as Fish Habitat

Abstract Ecological comparisons of transplanted, natural (reference) and disrupted (unvegetated) marsh sites on the Fraser River estuary, British Columbia, were conducted between 1991 and 1994. The study examined vegetative biomass and cover, invertebrate abundance, fish abundance, fish residency, fish food, and submergence time for the three habitats. Standing crop biomass at three transplant sites was within the range of values for reference sites, but was much lower at an unstable site where sediment slumping had occurred. The percent cover of Lyngbyei's sedge (Carex lyngbyei) in eight transplant sites was 0.05) was observed among marsh sites when chum salmon (Oncorhynchus keta) and chinook salmon (O. tschawytscha) fry abundance were compared. However, chinook and sockeye smolt catches were significantly different (p>0.05) was observed among marsh sites when chum salmon (Oncorhynchus keta) and chinook salmon (O. tschawytscha) fry abundance were compared. However, chinook and sockeye smolt catches were significantly different (p<0.05) among marsh sites and were usually higher at disrupted sites. In nine sites in the North Arm and Deas Slough area chum fry residency was examined. At one transplant site (DEI) marked chum fry were caught up to 48 h after release. No fry were caught 1 h after release at a transplant site (Dll) and a disrupted site (DE4). At the remaining sites, fry were caught up to 1 and 3 h after release. At all sites, over 80% of the total number of food organisms examined in chum fry stomachs were harpacticoid copepods. Mean submergence time for reference marshes ranged from 33.2 to 50.7%, but for transplanted sites the value ranged from 26.4 to 60.1%. Our study shows that numerous factors need to be examined in determining if restored marshes will function as natural habitats. The development of a standardized set of reference criteria would assist in evaluating whether or not transplanted marshes are functioning as designed.

Decomposition Rates of Purple Loosestrife (Lythrum salicaria) and Lyngbyei's Sedge (Carex lyngbyei) in the Fraser River Estuary

Using litter bag experiments in the Fraser River estuary in British Columbia, we tested for differences in the relative decomposition rates between leaves of purple loosestrife (Lythrum salicaria), an introduced exotic and a native sedge (Carex lyngbyei). The difference in the mean decay rate coefficient for the two species was significantly defferent (p<0.01) and the coefficient for purple loosestrife (0.0110 d−1) was nearly four times higher than for Lyngbyei's sedge (0.0028 d−1). This is the first estimate of the decay rate coefficient for purple loosestrife from an estuary. The rapid decay rate of loosestrife leaves suggests that they supply detritus to the ecosystem in autumn whereas the much slower decay rate of sedge implies that it supplies detritus throughout the winter and early spring. Consumer organisms important in juvenile salmon food webs appear to be adapted to take advantage of the detritus provided in these seasons. The findings have implications for habitat management because purple loosestrife has recently invaded estuaries of the northeast Pacific and may be outcompeting native sedges important in detrital-based food webs.

Intertidal habitats used by juvenile chinook salmon ( Oncorhynchus tshawytscha) rearing in the North Arm of the Fraser River estuary

Results from surveys of juvenile chinook ( Oncorhynchus tshawytscha) and their invertebrate food items in the North Arm of the Fraser River estuary are presented and related to habitat zones on narrow beaches. Fish catches were highest on unvegetated habitat in the low tide area. The weight of food items in stomachs was highest from fish in the mid intertidal area. The distribution and abundance of ten common prey used by chinook were also examined. Emergent vegetation (sedges ( Carex lyngbyei), rushes ( Scirpus spp., Typha spp.)) and riparian shrubs and trees in the middle and upper intertidal zones, respectively, were identified as vital components providing detritus and habitat for the chinook food organisms. Water volume over the unvegetated sand and mud flats in the low intertidal zone needs to carefully managed in this part of the estuary where extensive dyking and filling has been conducted in the past. For the purposes of managing fish habitat to achieve a goal of no net loss of habitat in the Fraser estuary, biologists are assigning highest values to the sedges and rushes. Our data support this as an interim measure, but further research is needed to investigate the importance of riparian vegetation as its significance may be underestimated.

Strategies for restoring and developing fish habitats in the Strait of Georgia—Puget Sound Inland Sea, northeast Pacific Ocean

Rehabilitation and development of fish habitats are potential techniques for achieving sustainable development in coastal seas. Recent projects in the Strait of Georgia and Puget Sound to examine this possibility have conducted trials or experiments with sedge marshes ( Carex lyngbyei) (26 sites) and eelgrass beds ( Zostera marina) (14 sites). Some studies have been appropriate for examining the potential compensation of wetland losses from industrial developments, but many were experimental and small scale. Larger scale projects and longer term monitoring are needed to confirm that the policy goals of no net loss or net gain in fish habitat can be met using these techniques.

Plant zonation in a brackish tidal marsh: descriptive verification of resource-based competition and community structure

This study examined the hypothesis that the zonal patterns of dominant species in brackish tidal marshes may be explained by resource competition for soil nitrogen and light. This hypothesis was tested by analyzing abiotic and biotic field data collected from a brackish tidal marsh located at Brunswick Point, British Columbia. Biotic data revealed that this tidal marsh is dominated by two species that occupy distinct separate zones correlated to marsh elevation. In particular, sites whose elevation was from −0.80 to 0.20 m (geodetic datum) were dominated by Scirpus americanus, while sites with an elevation 0.20 m were dominated by Carex lyngbyei. Analysis of the relationships between measured variables indicated that total species biomass, species height, and total soil nitrogen were all positively correlated to sample site elevation. Further, the availability of light at the soil surface was found to be negatively correlated to plant biomass and site elevation. These results may suggest that S. americanus is dominant in the low marsh because it is a better competitor for soil nitrogen. Carex lyngbyei may be competitively dominant in the high marsh because its greater biomass and height make it a superior competitor for light. Key words: competition, light, nitrogen, tidal marshes, zonation.

Woody plant succession on earthquake-uplifted coastal wetlands of the Copper River Delta, Alaska

The delta formed by the Copper River stretches for more than 75 km along the south central coastline of the Gulf of Alaska. It is the terminus of the outwash deposits from a large part of the most heavily glaciated region of North America, and all major rivers that flow into the delta carry extremely high levels of suspended sediments. Coastal wetlands extend inland for as much as 20 km. In 1964, an earthquake of Richter magnitude 8.4 to 8.6 raised the entire delta from 1.8 to 3.4 m above the previous mean sea level. Subtidal areas became intertidal, and intertidal areas supertidal. Marshland advanced seaward as much as 1.5 km in the intertidal zone. Vegetation on many, but not all, newly supertidal levees began to change from herbland to shrubland. A change in frequency and duration of tidal inundation and water salinity has been thought to be the most obvious cause of this succession, but explanation is lacking. Freshwater dominates the estuarine circulation due to a bar-built estuary and the extremely high input of freshwater from glacier runoff and precipitation. Tides merely raise freshwater onto the wetlands. Halophytes are rare even at the seaward edge of vegetation. The characteristic species of the present intertidal marshes, Lyngbye sedge ( Carex lyngbyei), also is characteristic in inland freshwater marshes. Initial post-earthquake invasion of woody plants was confined to natural levees. More recently, shrubs have begun to move seaward into new inter-tidal marshland. Only three shrub species, sweetgale ( Myrica gale var. tomentosa). Barclay willow ( Salix barclayi), and Sitka alder ( Alnus viridis ssp. sinuata) are important in woody plant succession. Barclay willow was abundant before the uplift. Increased distribution and abundance of willow was the earliest indication of post-earthquake succession. Sweetgale is now the most aggressive species. It was present on tidally flooded levees before the uplift and has become a ubiquitous understory shrub in all willow stands and an invader on newly formed intertidal marshes. Sitka alder grows on supertidal levees where the substrate is wet, but aerated. Black cottonwood ( Populus balsamifera ssp. trichocarpa) and Sitka spruce ( Picea sitchensis) trees are present in many alder stands. Many Sitka alder stands have become black-cottonwood/Sitka-alder woodland. Sitka spruce forest may eventually develop on some supertidal levees. Shrubland, woodland and forest vegetation analogous to that developing on supertidal levees is present on older wetland habitats further inland. It is likely the same plant successions would have occurred without an uplift. The uplift appears to have altered locations and rates, but not the nature, of wetland plant succession on the Copper River Delta.