Carex Meadow Research Articles

Effects of Environmental Manipulations on Triglochin Palustris: Implications for the Role of Goose Herbivory in Controlling its Distribution

1 Arrowgrass (Triglochin palustris) is a preferred forage species of geese in the YukonKuskokwim Delta (south-western Alaska) where it is found primarily on slough levees in coastal areas. Geese may affect nutrient availability, interspecific light competition, and salinity. These variables were manipulated in order to identify interactive effects of interspecific competition and abiotic factors on arrowgrass size, biomass allocation and distribution, which are likely to be significant in relation to the effects of herbivory on arrowgrass abundance and distribution. 2 Arrowgrass individuals were transplanted from two slough levee communities to the same two communities and to the adjacent slough margin and wet Carex meadow communities. Geese were excluded and nutrient availability, light competition and salinity levels were manipulated. 3 When light levels were not manipulated, fertilization had a negative effect on plant biomass and allocation to bulbs. Under decreased competition for light, plant biomass of fertilized plants was not significantly different from that of control plants. Fertilization appears to have a negative effect on arrowgrass as a result of increased competition for light. 4 Plants in the slough margin habitat were smallest, had the lowest allocation to leaves and stolons, and the lowest N concentrations and total N mass. Results from the fertilization treatment suggest plants in this community are limited primarily by physical factors. 5 Plants in the Carex wet meadow had higher allocation to leaves than in other communities under unfertilized conditions, but decreased allocation to leaves under fertilization. Plants in this community appear lightand nutrient-limited under unfertilized conditions, and primarily light-limited under fertilization. 6 Our results suggest that the presence of geese may control arrowgrass distribution because (a) faeces deposition has a negative effect on arrowgrass, (b) this negative effect is ameliorated by consumption of neighbours, and (c) the combination of high light competition and highly selective foraging for arrowgrass limit expansion of arrowgrass into the Carex meadow community. These explanations can now be tested.

Nitrogen Mineralization and Microbial Biomass Nitrogen Dynamics in Three Alpine Tundra Communities

AbstractThe alpine tundra of the Colorado Front Range supports a variety of plant communities whose distribution corresponds to their topographic position. Our objectives were to: (i) determine patterns in net N mineralization and microbial N pools among three communities, Kobresia, Acomastylis, and Carex meadows, that span a topographic gradient, and (ii) relate any patterns to soil microclimate differences among these communities. Average yearly net N mineralization rates, measured with an in situ core incubation technique, were 1.2 g N m−2 in 1991 and 1.0 g N m−2 in 1992. No differences were detected in yearly N mineralization rates among the three communities; however, net nitrification and other soil properties were found to differ among communities. Net N mineralization rates and microbial N showed strong temporal variation, and this variation was related to different variables for each community. Seasonal variation in N mineralization was related to soil water and microbial N in Kobresia meadows, to soil temperature and microbial N in Acomastylis meadows, and to soil water and temperature in Carex meadows. Seasonal changes in microbial N were related to soil water in Kobresia and Acomastylis meadows. Large fluctuations in microbial N indicate that periodic losses from the microbial pool may be important to N availability in this alpine tundra site.

The patterning of plant communities and edaphic factors along a high arctic coastline: implications for succession

Isostatic rebound and the periodic development of ice-push beach ridges have created topography suitable for development of biologically rich polar oases along the northeast coast of Devon Island, Canada. Distinct patterning of both plant communities and edaphic factors from coastal shoreline areas inland indicate primary succession with a directional species replacement At Rocky Point (emergent < 2000 BP) biological development along the shore is initiated by marine algae that are invaded by cyanobacteria. These organic mats are colonized by Puccinellia on the shoreline of these brackish lagoons. Where the topography grades upslope, via concave areas, the toposequence from Puccinellia proceeds through Dupontia → Carex → Salix hummocks → cushion plant–lichen communities. In drier, convex areas Puccinellia proceeds through rosette-herb hummocks → cushion plant–lichen communities as a toposequence. Reduced levels of salinity and of nitrogen fixation upslope (from the shore) along with increased depth of organic soils and ability of soils to hold more soil water appear important in the conversion of Puccinellia- to Dupontia- to Carex-dominated meadows. This is the major chronosequence at Rocky Point and it is these Carex meadows that occupy most of the wetlands of Truelove Lowland. The Salix hummocks and cushion plant–lichen communities of all drier habitats resemble communities of similar species composition on the beach ridges of the lowland. Key words: arctic Canada, succession, plant communities, soil factors, polar oasis.

Dinitrogen Fixation in the Wet Meadows and Emergent Zones of Two Nebraska Sandhills Lakes

-Dinitrogen fixation (acetylene reduction) activity was determined along a moisture gradient transect of a neutral-slightly alkaline lake (Island Lake) and an alkaline lake (Goose Lake) in western Nebraska during the summers of 1981 and 1982. Vegetation graded from Carex meadow to Typha to Scirpus emergent zones along each of the 50-m transects. Abundant growth of cyanobacteria occurred on exposed soil surfaces and epiphytically below the water line in the emergent zones. The Carex meadow exhibited relatively low and variable rates of acetylene reduction, whereas the Typha and Scirpus zones had consistently high rates of activity. Estimated mean nitrogen influx rates (kg ha-' yr-1) for the 1981 and 1982 seasons were consistently higher at Goose Lake (Carex, 0.5; Typha, 10.143.8; Scirpus 8.5-13.5) compared to Island Lake (Carex, 0.1; Typha, 0.9-10.6; Scirpus, 2.95.7). The higher rates of activity at the Goose Lake site are most likely due to the alkaline pH which is considered to favor cyanobacteria. The expansive wet meadow-emergent zones bordering the typically shallow Sandhills lakes support microbial populations which contribute large amounts of biologically fixed nitrogen to these aquatic ecosystems.

PHYSIOLOGICAL ECOLOGY OF NITROGEN FIXING BLUE‐GREEN ALGAL CRUSTS IN THE UPPER‐SUBALPINE LIFE ZONE1

ABSTRACTBlue‐green algal (cyanobacterial) crusts composed of nitrogen fixing Nostoc commune Voucher ex Born. et Flah. and Tolypothrix conglutinata var. colorata Ghose were studied in the upper‐subalpine life zone, Mission Mountain Wilderness, Montana. Rates of ethylene production were highest in the submerged shoreline crusts, lower for exposed crusts pioneering rocky shorelines and lowest in the Carex meadow. Nitrogenase activity (acetylene reduction technique) was constant between 200–285% crust moisture content (wet/dry weight) and then rapidly declined to 0 between 200–140%. Optimal temperatures for ethylene production by illuminated cells was between 20–30° C for T. conglutinata, 20° C for N. commune and about 25° C in darkness for both species. Nitrogenase activity by T. conglutinata in culture was unaffected by repeated freeze‐thaw treatments whereas N. commune was severely inhibited. In contrast, N2‐ase activity of these two species in an intact crust was unaffected by repeated freeze‐thaw treatments. Application of nitrogen‐free growth medium to intact crusts increased nitrogenase activity by 3.7 times implying that these were mineral deficient under field conditions. Photosynthesis was light saturated at 125 μmol‐m−2.s−1 whereas nitrogenase activity was light independent for cells with carbohydrate reserves. When carbohydrate reserves were reduced by 8 h incubation in darkness, between 1–3 h of illumination were required to restore nitrogenase activity to 80% of the maximum rate. Biochemical pathway inhibitor studies employing DCMU, MFA, and CCCP showed that oxidative metabolism was the source of reductant for acetylene reduction. Tetrazolium precipitation in heterocysts paralleled acetylene reduction activity in the inhibitor treated cells.

Multiple successional pathways on recently disturbed jack pine sites in Michigan

Jack pine communities in northern lower Michigan recently disturbed by clearcutting, deliberate burning, or wildfire were studied over three growing seasons, and were compared to undisturbed jack pine stands. Newly disturbed sites generally had more vascular plant species than mature forests. Many of these species did not persist, especially on burned sites, and species richness declined sharply the second year after fire. In several cases annual and biennial species dominated first-year burns but were unimportant thereafter. Several pathways of early successional development were evident on the disturbed sites, which was facilitated by jack pine regeneration failure on all but one of the disturbed sites. Unburned clearcuts rapidly developed into Carex meadows, with few other species of any importance. This pathway was also followed on some deliberately-burned and wildfire sites. Other burned areas developed a stratified canopy of shrubs and early successional hardwoods, and were rich in species and high in cover. Stand replacement by jack pine occurred on one mature jack pine site burned by wildfire. Jack pine regeneration failure has been attributed to numerous factors involving: seed loss due to fire and predation, and low germination and seedling survival due to inadequate seedbed, drought, competition, pathogens, grazing and high surface temperatures. Index of similarity comparisons showed that different sites of the same post-disturbance age were significantly ( P < 0.01) less similar in species composition than a single site sampled in 2 or 3 consecutive years. Post-disturbance age was not a particularly strong indicator of species composition on these sites, because each site had a different assemblage of species (30–40% dissimilarity among sites of the same disturbance class and post-disturbance age). Therefore, the individualistic nature of each site, rather than age following disturbance, is the dominant aspect in understanding successional relationships in these communities.

Seasonal dynamics of nutrients in a Carex meadow

Nutrient accumulation in aboveground biomass and mobilization of nutrients in litter were studied on a Carex meadow in southern Quebec, Canada. Seasonal changes were characterized by short periods of rapid element uptake and release. By late May the total element levels were 80% of maximum. Accumulation of N, P, and K was rapid relative to early increments in biomass. Ca, Mg, and micronutrients were taken up from the soil solution across the season and levels paralleled changes in biomass. In early summer elements were released from litter more rapidly than litter dry weight declined. Mobility of elements decreased in the order K &gt; Mg &gt; P &gt; N &gt; Ca. Overwinter, 83% of K was released, whereas Ca concentration in litter increased overwinter and through the following summer. Immobilization of Fe in litter was pronounced. Overall, &gt; 90% of the element mass in green late-summer shoots was retained in litter overwinter.

Productivity relations in a Carex-dominated ecosystem.

Seasonal and total primary productivity was measured for a Carex meadow in southern Quebec, Canada. Forty-five one-meter2 plots were sampled for dry weight biomass, species composition, structure (species density, diversity, height) and soil parameters including macronutrient concentrations (Ca, K, Mg, Na, N, P), pH, organic matter, and water depth. Shoot net productivity and litter decomposition rates were computed for 20-day intervals May-September, inclusive. Relationships between all parameters were examined by principal components analysis.Dominant species included Carex lacustris, C. aquatilis, Calamagrostis canadensis, and Typha angustifolia. For a 130-day growth period, mean shoot net productivity was 6.3 g·m-2· da-1 and terminal standing crop 807 g·m-2. Terminal standing crop was very close to above ground biomass predicted by the Gorham equation based on thermal relations for Carex ecosystems and to total accumulated litter mass (779 g·m-2). Seasonal production showed a strong bimodal pattern with peak productivities in mid-June (15.3 g·m-2·da-1) and mid-July (4.3 g·m-2·da-1). Decomposition of the previous year's litter was 81% complete by late September.Soil fertility, fire incidence, and topographic position were the three most important gradients resolved by principal components analysis. The first component distinguished sediment-rich Typha angustifolia communities near open water from oligotrophic stands of Carex spp. on central areas of the meadow. Production levels correlated closely with extractable soil calcium (r=0.40**) and phosphorus levels (r=0.39**). Species diversity and stem density related inversely to productivity on this component. Fire incidence (component II) had a marked effect on species diversity due to surface scarification and removal of litter mass. Component III was a topographic gradient separating composition, and community structure.Magnesium and sodium levels decreased from upland to open water. Soil phosphorus increased markedly at water's edge related to mineral input by sedimentation. Pattern of N, P, K, and Ca coincided closely with total shoot production and litter mass levels suggesting closed biotic cycles of these elements.A model accounting for species diversity levels in Carex meadow was formulated based on the assumption that high productivity results in competitive species elimination.

Carbon Dioxide Concentration Gradients above the Soil Surface at High Elevations

Carbon dioxide profiles were measured in four high- elevation habitats in the White Mountains of California. The CO2 content was found to change little between day and night and at differ- ent levels above the ground within an alpine fell field and carex dry meadow (3,870 m elevation). By contrast, relatively large concentra- tion changes were found with time and height above the ground at the edge of a subalpine forest and a subalpine carex meadow (3,094 m). The possibility of short-term recycling of the abundant carbon dioxide of soil origin by the low growing meadow vegetation is proposed. tration near ground level in a forest may be more than twice the normal atmospheric content. He concluded that this increased supply of CO2 is an important consideration for the survival of the shade flora. Fuller (1948) measured carbon dioxide concentration gra- dients in forests and grasslands and found concentrations of 730 to 1,810 ppm CO2 immediately above the ground surface. He also concluded that the high levels of CO2 were significant to the produc- tivity of forest plants. Sparling and Alt (1966) found stratification of carbon dioxide concentrations above a forest floor but only when wind flow was relatively low. Even slight breezes disrupted the con- centration gradients and they concluded that it is doubtful if forest floor plants are exposed to CO2 concentrations significantly greater than the normal atmospheric concentrations. Root biomass is proportionately high in alpine ecosystems. During the long, approximately nine-month dormant season, low temperatures reduce respiratory activity to low levels. During the summer growing season root respiration at night, when quite low temperatures prevail,

Sphagnum Species of the Thelon River and Kaminuriak Lake Regions, Northwest Territories

Seventeen species of Sphagnum are reported from an interior region of the Northwest Territories. Sphagnum perfoliatum is new to North America and others are very rare and of phytogeographic significance. The following list of Sphagna completes the report on cryptogams collected by Scotter in the Thelon River and Kaminuriak Lake regions from June 26 to July 2, 1964. Previous publications listed hepaticae and mosses (Scotter, 1966) and lichens (Scotter & Thomson, 1966). Scattered spruce trees (Picea glauca and P. mariana) are present along the periphery of the Thelon River sites; the other sites were in tundra communities. The terrain is flat to gently rolling and is covered with glacial drift. Most of the collections were made in tussock muskeg communities, low Carex meadow communities, or along the edge of ponds. The dominant vascular species included Betula glandulosa, Ledum decumbens, Salix spp., Carex spp., and Eriophorum spp. The elevation varied from 50 feet to less than 400 feet. The collection sites were near the following locations: Aberdeen Lake (1) 64038'N, 99044'W Aberdeen Lake (2) 6440'N, 99051'W Beverly Lake 64033'N, 100027'W Kaminuriak Lake 62.57'N, 95027'W Thelon River (1) 62036'N, 104050'W Thelon River (2) 64010'N, 102.34'W Voucher specimens are deposited in the herbaria of the University of Copenhagen (c) and the Canadian Wildlife Service, Edmonton (cws). The numbers are Scotter's. The nomenclature is in accordance with Isoviita (1966). The collections were made during field investigations of caribou range carried out under the auspices of the Canadian Wildlife Service.

STUDIES OF WATERFOWL IN BRITISH COLUMBIA: BALDPATE

A relatively large population of Mareca americana winters on the Coastal Plain, almost exclusively along the coast line when meadow flood ponds and sloughs farther inland are sealed by frost. A winter population in the interior is small in numbers and irregular in occurrence. Nesting grounds are in the interior only, from the Okanagan Valley and Kamloops–Nicola region, where the species is scarce, to as far north at least as the Haines Road in the northwest section of the Province. The most productive nesting grounds are in the Cariboo Parklands and the Lakes District near Vanderhoof. The main spring migration of transients through the central interior takes place during the last two weeks of April and by early May a breeding population is established on the many sloughs and ponds of the nesting range. Dry Carex meadows bordering certain water areas is the preferred nesting habitat. It is usual for the full clutch of eggs to be laid not later than June 15. In the Cariboo Parklands the average number of young in 10 June broods was 7.0, the average of 75 July broods was 6.2, and the average of 14 August broods was 5.2. In the Lakes District near Vanderhoof the average number of young in 37 broods during July and August was 7.0. Females with broods habitually frequent the open water of marsh ponds, lake bays, and marsh-edged rivers. Here, if approached by man, they vigorously defend their young by ruses to attract attention from them. Short, successive flights in front of a moving canoe, and splashing across the water in a direction leading away from the young are examples of behavior at this time. Postbreeding males associated in flocks on open water often accompany rafts of postbreeding coots and diving ducks. Aquatic insects is the chief item in the diet of downy young. Adults feed principally on the foliage of aquatic plants, grasses, algae, and seeds of aquatic plants, in that order. Insects are eaten in relatively small amounts. The baldpate may, under certain conditions and in certain localities, destroy cultivated forage plants. It is an important game duck and, because of its almost exclusive vegetable diet, highly palatable. Revenue derived from the hunting of baldpate, and the economic value of its flesh for human food, more than compensate for any economic loss resulting from crop destruction.