Carex Nebrascensis Research Articles

Effect of overwinter hydration, seed storage time, temperature, and photoperiod on germination of some Carex, Juncus, and Alopecurus species

Factors affecting seed germination of select wetland and aquatic plants were investigated in two experiments. In the first, seeds of four Juncus species, Alopecurus aequalis, and Carex nebrascensis were stored overwinter at 3–4°C either dry or wet. In spring, these groups were further divided into four constant temperature treatments (15, 20, 25, or 30°C) and 3 fluctuating temperature treatments (low, moderate, high). In the second experiment, the duration of cold-wet storage, photoperiod, and temperature were further evaluated. In the first experiment, cold-wet seed storage led to higher and faster germination for all but C. nebrascensis; Fluctuating temperatures produced the highest germination of A. aequalis, C. nebrascensis, Juncus tenuis, and J. ensifolius. In Experiment 2, seed storage time effects varied with species. Photoperiod effects (12v. 14h light) were generally insignificant. Diel temperature fluctuations of 15–27°C produced higher seed germination than 32–38°C for all four Juncus species. The highest germination percentages of J. balticus (64–69%) and J. ensifolius (61–73%) occurred after at least 2 months of cold-wet storage and incubation at 15–27°C, whereas J. tenuis and J. torreyi had 51–58% germination both at the start of the study and after a year of wet vernalization. The conditions for germination of the species studied still needs further optimization, but the effects of temperature, temperature fluctuation, overwinter storage conditions, as well as the days to germinate at a given temperature, have been at least partly elucidated for the species studied. The data can now be used for initiating seed pretreatment for habitat projects.

Hydroseeding improves field establishment of Nebraska sedge regardless of seed treatment

Practical and effective direct-seeding methods for establishment of restored and constructed wetlands are desirable to reduce cost and labor. Current practices used to establish wetlands in the Western US typically involve the use of greenhouse-propagated plant materials or field-collected transplants. These methods are expensive and labor intensive. Sowing germinants into a muddy seedbed, a technique commonly used in rice production, shows potential as a method for field establishment of wetland sedge species. We compared establishment densities of Nebraska sedge ( Carex nebrascensis Dewey [Cyperaceae]) using 2 seed treatments (32-d stratification at 3 °C [37 °F]) and germinants produced with a 13-d aerated warm water (35 °C [95 °F]) bath and 2 seed delivery methods (hydroseeding and broadcasting). The comparisons were conducted in 2 ponds; one prepared using traditional agronomic practices and the other prepared to create a muddy seedbed similar to that used in rice production. We found a 2X to 3X increase in seedling establishment from hydroseeding compared with broadcasting regardless of seed treatment; however, seedling densities dramatically decreased later in the season, presumably as a result of inundation that drowned the plants. This problem highlights the need for close control of water levels when establishing wetland sedges. This level of precision may be difficult to achieve under typical field conditions.

Soaking Nebraska sedge seeds in warm, aerated water improves germination

Nebraska sedge ( Carex nebrascensis Dewey [Cyperaceae]) is a broadly distributed and locally abundant sedge in western North America. The species is commonly used in wetland and riparian restoration and enhancement plantings. Germination is typically achieved by subjecting the achenes with their perigynia removed (hereafter simply referred to as seeds) to 30-d stratification at 3 °C (37 °F); however, personal observations indicate that Nebraska sedge can be germinated using soaking water treatments without a stratification treatment. Staff at the USDA Natural Resources Conservation Service, Aberdeen Plant Materials Center subjected seeds of Nebraska sedge to a number of soaking treatments and compared average germination and germination rates with those obtained using traditional methods. We found that seeds soaked in warm (24–35 °C [75–95 °F]), aerated water germinated significantly faster (3 to 6 times) than all other treatments. We also determined that, in most cases, soaking Nebraska sedge seeds in warm water significantly increased germination percentages compared with seeds germinated using the traditional 30-d stratification treatment (87% compared with 47%, respectively).

Biomass Production and Net Ecosystem Exchange Following Defoliation in a Wet Sedge Community

Riparian ecosystems provide many ecosystem services, including serving as an important forage resource for livestock grazing operations. We evaluated defoliation impacts on above- and belowground production, and net ecosystem exchange of CO2 (NEE), in a wet sedge (Carex nebrascensis Dewey)-dominated plant community. In June or July of 2004–2005, experimental plots were clipped to 10 cm stubble height and paired control plots left unclipped. All plots were clipped to 2.5 cm in mid-September, and end-of-season and season-long aboveground production calculated. Root ingrowth cores were used to estimate annual root production and root length density (RLD). A portable gas exchange system and plexiglass chamber were used to measure NEE in 2005. An elevated water table in 2005 vs. 2004 was associated with higher (P &spilt; 0.001) season-long aboveground production (about double), but lower (P ≤ 0.05) belowground production (about half). Total productivity did not differ between years, but below-:aboveground ratios were 3× higher in 2004 vs. 2005. RLD was not different between years (P &spigt; 0.05). Clipping reduced (P ≤ 0.05) end-of-season aboveground standing crop by 33% to 73% depending on clipping month and year. Effects of clipping month on season-long aboveground production were inconsistent between years; June clipping decreased (P ≤ 0.05) production (-10%) in 2005 and July clipping decreased (P ≤ 0.05) production (-25%) in 2004. NEE for June-clipped plots recovered within 1 mo of clipping, whereas NEE for plots clipped in July remained below unclipped levels at the end of the growing season. Water table levels strongly influenced below-:aboveground ratios, although total production was relatively stable between years. Year effects overwhelmed clipping effects on season-long aboveground production. Defoliation after mid-summer did not allow recovery of photosynthetic capacity by the end of the growing season, suggesting the potential for long-term impact with regular late-season defoliation. Los ecosistemas rivereños proveen muchos servicios, incluyendo ser una fuente importante de forraje para operaciones de pastoreo. Evaluamos los impactos de la defoliación en la producción aérea y subterránea, y el intercambio neto de CO2 (NEE), en una comunidad de humedales dominada por juncos (Carex nebrascensis Dewey). En junio o julio de 2004–2005, las parcelas experimentales fueron cortadas 10 cm por encima del suelo y parcelas control en pares se dejaron sin cortar. Todas las parcelas fueron cortadas a 2.5 cm a mediados de septiembre, y al final de la temporada y la producción aérea de toda la temporada la fue calculada. Los núcleos de crecimiento interno de la raíz se usaron para estimar la producción anual de raíz y la densidad de la longitud radicular (RDL). Un sistema portable de intercambio de gases y una cámara plexiglass se utilizaron para medir NEE en 2005. Un alto nivel de agua en 2005 vs. 2004 asociado con una alta (P &spilt; 0.001) producción aérea de toda la temporada (cerca del doble), pero menor (P ≤ 0.05) que la producción subterránea (cerca de la mitad). La productividad total no fue diferente entre años, pero la tasa subterránea:aérea fue 3× superior en 2004 vs. 2005. RDL no fue diferente entre años (P &spigt; 0.05). El corte redujo (P ≤ 0.05) la producción aérea al final de la temporada de 33% a 73% dependiendo del año y el mes de corte. Los efectos de corte en cada mes sobre producción aérea fueron inconsistentes entre años, los cortes durante junio redujeron (P ≤ 0.05) la producción (-10%) en 2005 y los cortes durante julio redujeron (P ≤ 0.05) la producción (-25%) en 2004. NEE en las parcelas cortadas en Junio se recuperaron dentro del mes después del corte. Además NEE para las parcelas cortadas en julio permanecieron por debajo de los niveles de las no-cortadas al final de la etapa de crecimiento. Los niveles de la tabla de agua influenciaron fuertemente la tasa subterránea:aérea, aunque la producción total fue relativamente estable entre años. Los efectos de los cortes anuales afectaron la producción anual aérea durante toda la temporada. La defoliación después de la mitad del verano no permitió la recuperación de la capacidad fotosintética al final de la época de crecimiento, sugiriendo el potencial impacto a largo plazo con defoliaciones regulares al final de la temporada.

Plant community distribution along water table and grazing gradients in montane meadows of the Sierra Nevada Range (California, USA)

This study aimed to identify dominant plant communities across five wet and mesic meadows in the Sierra Nevada Range (California, USA) and examine the impacts of environmental and grazing gradients on plant community distribution and diversity. Species composition and environmental conditions were recorded in 100 plots over two years. Classification and ordination analyses were used to classify plant communities and identify relationships between community types and both environmental and grazing gradients. We identified the following six plant community types: Carex jonesii, Carex leporinella, Carex nebrascensis, Carex utriculata, Eleocharis pauciflora, and Veratrum californicum. We found strong connections between plant communities and water table variables, with low water table (r 2 = 0.56) and mean water table (r 2 = 0.30) significantly correlated with Axis 1 while high water table (r 2 = 0.29) and elevation were correlated with Axis 3 (r 2 = 0.49). We found significant differences among community types for all three water table variables and for elevation. We found no correlation between grazing and community type classification, but there was a significant difference in grazing levels among community types. The plant communities and relationships to water table found in this work may aid managers in understanding present conditions and identifying future changes in meadow ecosystems.

Defoliation Effects on Herbage Production and Root Growth of Wet Meadow Forage Species

Abstract Root growth is important to the competitive ability of plants, and understanding how herbage defoliation affects root growth has implications for development of management strategies. Objectives were to determine the effects of defoliation intensity and frequency on root characteristics and herbage production of slender wheatgrass ( Elymus trachycaulus [Link.] Shinners), Nebraska sedge ( Carex nebrascensis C. Dewey), and “Steadfast” birdsfoot trefoil ( Lotus corniculatus L.). Plants of each species were transplanted into containers that had been placed in the ground at wet meadow field sites the prior year. There were eight replications of a control and five defoliation treatments, which were combinations of different frequencies (two or five times) and intensities (light or heavy) and haying. Treatments were applied for a single growing season, and aboveground biomass was collected. Containers were extracted in October, and plant crowns, rhizomes, and roots were separated from the soil. Defoliation treatment did not affect total root weight, length, and surface area of Nebraska sedge or birdsfoot trefoil ( P >0.10). Slender wheatgrass total root weight was less when defoliated five times (4.46 g·container −1 ) than when defoliated twice (6.62 g·container −1 ) during the growing season. More frequent defoliation of slender wheatgrass also reduced length (20%) and surface area (21%) compared to less frequent defoliation. However, defoliation frequency did not affect aboveground biomass. Defoliation intensity did not affect aboveground production or root characteristics of the three species. Abundant soil moisture in meadows likely buffers negative effects of defoliation. For all species, two defoliation events (e.g., haying followed by grazing) does not appear to negatively affect root growth and herbage production.

Sedge Transplant Survival in a Reconstructed Channel: Influences of Planting Location, Erosion, and Invasive Species

Sedge transplanting success in recently constructed channels is essential because the lack of vegetation makes the channel highly susceptible to erosion and non‐native plant invasion. In this study, greenhouse grown plugs of Carex nebrascensis Dewey (Nebraska sedge) and C. utriculata Boott (beaked sedge) were transplanted onto two different channel geomorphic surfaces, depositional and erosional, for two different experiments. The first experiment tested the effects of planting location on sedge survival and growth and the second tested the effects of Cirsium arvense presence on transplant survival and growth. Survival during the first growing season was the same for both species; however, shoot numbers were greater for C. nebrascensis (98 shoots/m2) compared to C. utriculata (84 shoots/m2) at the end of the first growing season. Greater shoot numbers also occurred on depositional planting locations (117 and 165 shoots/m2) compared to erosional planting locations (65 and 59 shoots/m2) at the end of the first and second growing seasons, respectively. The presence of Ci. arvense was observed to reduce sedge shoot numbers regardless of sedge species during the first growing season but no significant difference was observed by the end of the second growing season. These results suggested that control of Ci. arvense did not increase sedge vegetative growth within two growing seasons. Results suggest that revegetation success was greatest on depositional geomorphic surfaces and that both species are appropriate for transplanting; however, C. nebrascensis outperformed C. utriculata at sites with water tables that averaged deeper than 30 cm over the growing season.

Seasonal effects of 19 plant species on COD removal in subsurface treatment wetland microcosms

Plants have many well-documented influences in treatment wetlands, but differences in individual species’ effects on year-round and seasonal performance are poorly understood. In this study, we evaluated plant effects on seasonal patterns of organic carbon removal (measured as COD) and sulfate concentration (used as an indicator of rootzone oxidation) in replicated, batch-loaded, greenhouse microcosms simulating subsurface treatment wetlands. Microcosms were planted with monocultures of 19 plant species or left unplanted as controls, dosed every 20 days with synthetic secondary wastewater, and operated over 20 months at temperatures from 4 to 24 °C. Study-long COD removal averaged 70% for controls and 70–97% for individual species. Most species enhanced COD removal significantly and the benefits of plants were greatest at 4–8 °C because COD removal decreased at low temperatures in controls but displayed limited seasonal variation in planted microcosms. Removal was significantly better at 24 °C than 4 °C with two species ( Panicum virgatum and Leymus cinereus), significantly poorer with two species ( Carex utriculata and Phalaris arundinacea), and did not differ with 15 species. Only one species showed a significant positive correlation between temperature and COD removal ( Iris missouriensis, r = 0.67), while two species showed significant negative correlations (better when colder: Carex nebrascensis, r = −0.67; C. utriculata, r = −0.93). High COD removal throughout the study was strongly associated with high SO 4 concentrations at low temperatures, suggesting that plant performance is related to rootzone oxidation and species’ abilities to promote aerobic over anaerobic microbial processes, particularly in winter. Results indicate that improved year-round and cold-season COD removal is common across diverse wetland plant species and novel species can be as good or better than those typically used. Better performing species were largely in the sedge and rush families ( Cyperaceae and Juncaceae), while poorer performing species were largely in the grass family ( Poaceae).

Vegetation and water-table relationships in a hydrologically restored riparian meadow

We examined the relationship between water-table elevations and plant community distributions in a hydrologically restored riparian meadow. The meadow, adjacent to Bear Creek in northeastern California, experienced hydrologic modification due to “pond and plug” stream restoration. Plant species composition and cover were sampled within 128 plots, and a hydrologic model was used to simulate a three-year time series of water-table for each plot. TWINSPAN was used to classify the vegetation into four community types:Eleocharis macrostachya / Eleocharis acicularis, Downingia bacigalupii / Psilocarphus brevissimus, Carex nebrascensis / Juncus balticus, andPoa pratensis / Bromus japonicus. Nonmetric multidimensional scaling was utilized to investigate the relationships between community types and hydrologic variables. Community types were distributed along the hydrologic gradient at reasonably similar positions to those found in previous studies; howeverCarex nebrascensis, a species frequently used as an indicator of shallow water tables, occurred at greater water-table depths than reported in other studies. The range of water-table depths in this meadow was greater than previously observed, presumably due to the higher temporal resolution of water-table measurements, in addition to the intermittent nature of stream flow in Bear Creek. This study provides an increased understanding of the ecology of meadow communities, and can be utilized for improved design and objective setting in future restoration projects.

Development of vegetation in a constructed wetland receiving irrigation return flows

The Fairview Constructed Wetland, a complex of replicated wet meadow (primary filter) and shallow marsh (shallow wetland) cells, was built in southeast Idaho in 1999 and planted with seven native plant species. The development of aboveground biomass and root mass and the accumulation of litter for each cell and for each species are described here. Establishment patterns varied among species and wetlands. Juncus balticus and Carex nebrascensis contributed disproportionately to the biomass in the primary filter cells. In these wetlands, aboveground biomass increased from an overall average of 443 in 2000 to 560 g/m 2 in 2003, while root mass increased from 387 to 1108 g/m 2. Litter mass increased from 230 in 2001 to 829 g/m 2 in 2003. In the shallow wetlands, average aboveground biomass increased from 82 in 2000 to 391 g/m 2 in 2003, while root mass increased from 108 to 574 g/m 2 over this same period. From 2001 to 2003, litter mass increased from 68 to 214 g/m 2. All measures of biomass and litter in the shallow wetlands were less than the corresponding values in the primary filter cells over the same time period. Still, biomass measures differed among shallow wetlands and some of this variation was explained by the differences in each wetland's hydrograph.

Vegetative Nutrient Pools in a Constructed Wetland in Southeastern Idaho

ABSTRACT We examined the vegetative pools of carbon (C), nitrogen (N), and phosphorus (P) in constructed wetlands receiving irrigation return flows in southeastern Idaho. Seven native wetland plant species were introduced into the wetlands in 1999. Carex nebrascensis, Eleocharis palustris, Juncus balticus, and Scheonoplectus maritimus were planted in replicate wetland meadows (primary filters), and Scheonoplectus acutus, Scheonoplectus pungens, and Typha latifolia were planted in replicate experimental marshes (shallow wetlands). The elemental percentages of C, N, and P for aboveground biomass and litter varied among species, and the pattern of temporal change for each element in plant tissues was unique. At the end of the 2003 growing season, J. balitcus had more C and S. maritimus had less N and P than other species in the primary filter cells. No differences were detected in shoot N and P content among shallow wetland species, but litter from shallow wetlands had greater percentages of N and P than did standing biomass. C. nebrascensis aboveground biomass represented the largest pool of N and P (7.65 g/m2 and 0.45 g/m2). Litter nutrient pools contributed considerably to the total aboveground nutrient pool, and this was especially true for J. balticus patches where the pool for litter N (17.2 g/m2) was four times larger than the pool for biomass N (4.3 g/m2). This work suggests that larger nutrient pools were associated with areas of higher production rather than areas containing species with higher concentrations of nutrients.

Comparison of methods for seeding Nebraska sedge (Carex nebrascensis) and Baltic rush (Juncus balticus)

Four methods of seeding Nebraska sedge (Carex nebrascensis Dewey [Cyperaceae]) and Baltic rush (Juncus balticus Willd. [Juncaceae]) were compared in a controlled greenhouse environment. Methods evaluated were: 1) tackifier; 2) Submerseed™ pellets; 3) surface pressed; and 4) drilled. Greenhouse trays were flooded following seeding, and seeds were allowed to germinate in saturated soil conditions. Treatments were then evaluated for percentage of seeds that germinated within the row in which they were sown, and for number of seedlings per section of row. Results show Submerseed pellets have a high capacity for holding seeds in place and provide good germination.

Environmental effects on germination of Carex utriculata and Carex nebrascensis relative to riparian restoration

Seasonal riparian seedbed temperatures were measured and germination of Carex utriculata and C. nebrascensis seeds was tested in relation to chilling, perigynia removal, incubation temperature, and light to help guide propagation and direct seeding of these species for riparian restoration. Diurnal temperatures of riparian seedbeds at two sites in Strawberry Valley, Utah, USA ranged from 3.1 to 11.2° C in May to 9.5 to 24.1° C in August when water was generally available for seed germination. Pre-incubation treatments of chilling at 5° C for 7 to 150 days and perigynia removal increased germination of 2-year-old seeds of these species but were not necessary for high germination percentages (>89%) when seeds were incubated in light under a summer temperature regime (10 to 24° C). Seeds aged 0.5 and 1.5 years had lower germination percentages than 2-year-old seed but also had adequate germination percentages (>20%) for greenhouse propagation without pre-treatments when incubated in light at the summer temperature regime. After 5.5 years of storage at room temperatures, germination of C. utriculata was negligible, but that of C. nebrascensis was >35%. Seeds of both species that were overwintered in seed bags in riparian microsites had high germination percentages (>80%) when retrieved the following summer and incubated at a summer temperature regime in light. Althoug direct seeding in fall would allow natural chilling and potentially high germination percentages the following spring or summer, the risk of seed loss or excessive burial is great during high spring stream flows. A better strategy is to surface-seed wet seedbeds in early summer after peak flows have receded and temperature and light conditions are conducive to high germination percentages.

Transplanting Sedges (Carex spp.) in Southwestern Riparian Meadows

Abstract The success of revegetation efforts in southwestern U.S. riparian meadows has been limited because natural recolonization is often poor and little is known about establishment of transplanted native meadow species such as sedges. To evaluate their potential use in riparian restoration, the survival and growth of transplanted wildlings of three sedge species, Carex lanuginosa (woolly sedge), C. nebrascensis (Nebraska sedge), and C. rostrata (beaked sedge), were assessed. Transplanting occurred during two seasons (summer and fall) using two transplant sizes (295 and 680 cm3) at seven montane meadow sites in Arizona. Survival was similar among species, but shoot numbers were greater for C. lanuginosa (12.7 shoots/wildling) compared with C. nebrascensis (5.5 shoots/wildling) and C. rostrata (7.9 shoots/wildling). Survival was significantly greater for the summer transplant season (55.1%) versus fall (24.1%). Survival and growth were greater for the larger transplant size (46.1% large vs. 33.0% small; 8.1 shoots/wildling large vs. 6.4 small). Wildling survival was related to depth to groundwater for each species. Survival was highest for C. lanuginosa (78.6%), C. nebrascensis (88.2%), and C. rostrata (64.3%) where the groundwater depth was −48 to −60, −28 to −47, and −8 to −27 cm, respectively. These results suggest that restoration will be most successful if transplanting occurs in summer, using large wildling transplants when under stressful conditions such as waterlogged or dry soils, and when species are planted at appropriate groundwater depths.

Physiological and Growth Responses of Riparian Sedge Transplants to Groundwater Depth

Understanding of the influence of groundwater depth on the physiology and growth of transplanted sedges is needed to improve revegetation efforts in degraded riparian meadows. In a greenhouse experiment, we exposed transplants of Carex lanuginosa, Carex nebrascensis, and Carex rostrata to three simulated groundwater depths (4, 19, and 35 cm). Groundwater depth was manipulated over two phases: (1) water depths were held constant for 16 wk and (2) water depths were then increased over the next 6 wk. Leaf gas exchange, water relations, and shoot growth were measured periodically during each phase, and aboveground and belowground biomass were measured at the end of each phase. All species adjusted rooting depth to groundwater depth in response to the constant groundwater treatments, and groundwater depth had no effect on net photosynthetic rate and stomatal conductance. Net photosynthetic rate and stomatal conductance of all species initially increased when groundwater levels dropped but decreased rapidly after 4 wk of lowering groundwater. This response indicates that anaerobic conditions hindered leaf gas exchange under shallow but constant groundwater depths and also indicates that transplants may be less tolerant of shallow groundwater than naturally established sedges because of their smaller root systems. Compared with the other species, net photosynthetic rate and stomatal conductance of C. rostrata were more sensitive to declines in leaf water potential, and this species allocated proportionately more root growth to saturated soil zones. Carex rostrata’s growth and physiological characteristics indicate that its transplants have lower tolerance to dry soil and water stress than C. lanuginosa and C. nebrascensis.

Restoration of riparian meadows degraded by livestock grazing: above- and belowground responses

Riparian meadows in the western US are highly productive areas withinthe riparian corridor that have been extensively utilized for livestock grazingand that are often degraded. This study aimed to increase our understanding ofboth the functional responses and restoration potential of mesic meadow systemsin central Nevada, USA. Nitrogen addition and clipping treatments were used toexamine grazing effects, while aeration and revegetation were included toevaluate potential restoration treatments. Belowground response was determinedby examining gravimetric soil water content and rooting depth and activity.Aboveground response was determined for two key mesic meadow species,Carex nebrascensis and Poa pratensis,by quantifying gas exchange and water relations. Large yearly and seasonaldifferences among water tables largely determined the rooting activity anddepthin these mesic meadows and influenced treatment responses. Little rootingactivity occurred within or at the surface of the water table and rooting depthincreased as water table level lowered during the growing season. In general,nitrogen addition decreased rooting activity and depth relative to controls. Itresulted in less negative water potentials and photosynthetic rates that werehigher early in the growing season, but lower later in the growing season. Theeffects of nitrogen addition could be attributed to accelerated phenology andearlier senescence. Clipping resulted in less negative plant water potentialsinCarex and Poa, andPoa had higher photosynthetic rates immediately afterclipping but only for certain dates and comparisons. Aeration increased rootingactivity and depth where there was no confounding effect of water table. Also,predawn and midday water potentials were generally less negative forCarex and Poa in aerated plots.Establishment on the revegetation plots was dominated by annual and early seralspecies and, consequently, these plots exhibited reduced rooting depth andactivity early in the growing season and high root turnover. Results indicatethat water table depth and its effects on soil water are dominant factors indetermining the functional processes and recovery potentials of these riparianmeadows. Clipping had minimal effects on above- and belowground responses,perhaps because clipping was performed late in the growing season after plantshad begun to senescence. Nitrogen addition decreased rooting activity andaltered phenology, indicating deleterious effects. Aeration was effective atovercoming some of the negative affects of overgrazing and may be an effectiverestoration treatment. However, revegetation may have limited potential due toestablishment constraints of the dominant species.

Effects of water table, clipping, and species interactions on Carex nebrascensis and Poa pratensis in riparian meadows

In this study, we hypothesized that the primary variable determining species responses and interactions within wet/mesic riparian meadows in central Nevada, USA was the water table but that the direct and indirect effects of livestock grazing modified both species responses and interactions. We tested this hypothesis for two widespread riparian species, Carex nebrascensis and Poa pratensis ssp. pratensis, that co-occur but have maximum expression at different water tables. Carex nebrascensis has widely spread tillers typical of ‘guerilla’ plant architecture, while P. pratensis has closely spaced and compact tillers typical of ‘phalanx’ plant architecture. Individuals of both species were grown at mid-and low water tables with or without neighbors and were either clipped or not clipped at the end of the first growing season. For the study site with the most complete record, mean water-table depth during the growing season (May through August) on the mid sites was −32 cm in year 1 and −7cm in year 2. Water-table depth on the low sites was −69 cm in year 1 and −31 cm in year 2. Plant survival, tillering, biomass, and seed production over a 2-yr period were used to quantify the species responses. Water table had no effect on tillering or biomass of C. nebrascensis, indicating that it is adapted for growth and persistence over the range of water tables examined. In contrast, growth and tillering of P. pratensis was severely restricted at more shallow water tables. Poa pratensis had about 50% fewer tillers and lower biomass (9.0 vs 46.5 g) for neighbor-removed plots on mid- than low-water-table sites at one of the study meadows. Further, tiller numbers of P. pratensis increased over time on the low-water-table plots, but decreased on the mid-water-table plots. Clipping had no effect on the survival, tillering, or growth of either species. The clipping treatment may not have removed sufficient leaf mass or may have been applied too near the end of the growing season to elicit a response. Neighborhood removal resulted in a 3- to 10-fold increase in tillering and higher plant mass (1.3 vs. 9.5 g) for C. nebrascensis. Poa pratensis showed an even greater response to neighbor removal. Tillering was 6-to 100-fold greater and mass was 15 to 50 times greater on neighbor removed than neighbor-intact plots. Comparisons between single species and mixed species plots indicated that there was an interaction between the species that limited tiller production in C. nebrascensis. These results indicate that P. pratensis, the ‘phalanx’ species, is capable of more rapidly responding to disturbances that remove neighbors and increase available space than C. nebrascensis, the ‘guerilla’ species. Contrary to previous studies, the interactions between the two species do not seem to be related to plant architecture and can be best attributed to generally greater growth rates and increased competitive ability for P. pratensis at lower water tables. Grazing may further alter the relative competitive ability of the two species in favor of P. pratensis.

Restoring Degraded Riparian Meadows: Biomass and Species Responses

Riparian meadows in central Nevada are highly productive and have been extensively utilized for livestock grazing. Consequently, many have been severely degraded resulting in changes in species composition and decreases in productivity. During a 3 year study, we examined the responses of mesic meadow systems to yearly nitrogen addition (100 kg ha(-1)) and clipping (8-10 cm stubble height) to increase our understanding of grazing effects. We also examined the effects of a one-time, fall aeration (10 cm deep by 2 cm wide holes spaced 20 cm apart) and revegetation (removal of existing vegetation and reseeding) to evaluate the restoration potential of these sites. Changes in total biomass, species aerial cover and frequency, and surface basal cover were used to evaluate treatment responses. Clipping had no effect on total biomass, possibly because it was conducted late in the growing season. In contrast, nitrogen addition plus clipping increased biomass in all 3 years when treatments were compared across sites and for 1 out of 3 years when treatments were compared across a single site. Aeration had no effect on above ground biomass, but has been shown to increase rooting activity in these same meadows. Due to a dry, hot spring, early seral and weedy species had higher establishment than the seeded natives in the revegetation plots, and biomass was low the first year after treatment. Individual species varied in their treatment responses. The cover of low-growing forb species (western aster (Aster occidentalis [Nutt.] Torrey and A. Gray), long-stalk starwort (Stellania Longipes Goldie), and common dandelion (Taraxacum officinale Wigg.) declined through time for all treatments, presumably due to increased grass cover and shading following release from grazing and above average precipitation and water table levels in 1998. Examination of the key graminoids showed that Kentucky bluegrass (Poa pratensis ssp. pratensis L.), an increaser species, did not increase in response to release from grazing, but increased in response to clipping and nitrogen addition. Nebraska sedge (Carex nebrascensis Dewey), a desirable native, increased in response to both release from grazing and nitrogen addition. The results were influenced by high spatial and temporal variability in water table elevations within these systems. DOI:10.2458/azu_jrm_v54i3_martin

Perigynium Removal and Cold, Moist Stratification Improve Germination of Carex nebrascensis (Nebraska Sedge)

p ublic and legislative emphasis on wetland riparian restoration using native plants has increased the need for information on the establishment of many wetland and riparian plant species, including sedges (Carex spp. A.L. Juss [Cyperaceae]). Nebraska sedge (Carex nebrascensis Dewey) is a dominant emergent species in many Intermountain West and Great Basin wetland and riparian areas. Nebraska sedge has A wet meadow

Restoring degraded riparian meadows: Biomass and species responses

Riparian meadows in central Nevada are highly productive and have been extensively utilized for livestock grazing. Consequently, many have been severely degraded resulting in changes in species composition and decreases in productivity. During a 3 year study, we examined the responses of mesic meadow systems to yearly nitrogen addition (100 kg ha(-1)) and clipping (8-10 cm stubble height) to increase our understanding of grazing effects. We also examined the effects of a one-time, fall aeration (10 cm deep by 2 cm wide holes spaced 20 cm apart) and revegetation (removal of existing vegetation and reseeding) to evaluate the restoration potential of these sites. Changes in total biomass, species aerial cover and frequency, and surface basal cover were used to evaluate treatment responses. Clipping had no effect on total biomass, possibly because it was conducted late in the growing season. In contrast, nitrogen addition plus clipping increased biomass in all 3 years when treatments were compared across sites and for 1 out of 3 years when treatments were compared across a single site. Aeration had no effect on above ground biomass, but has been shown to increase rooting activity in these same meadows. Due to a dry, hot spring, early seral and weedy species had higher establishment than the seeded natives in the revegetation plots, and biomass was low the first year after treatment. Individual species varied in their treatment responses. The cover of low-growing forb species (western aster (Aster occidentalis [Nutt.] Torrey and A. Gray), long-stalk starwort (Stellania Longipes Goldie), and common dandelion (Taraxacum officinale Wigg.) declined through time for all treatments, presumably due to increased grass cover and shading following release from grazing and above average precipitation and water table levels in 1998. Examination of the key graminoids showed that Kentucky bluegrass (Poa pratensis ssp. pratensis L.), an increaser species, did not increase in response to release from grazing, but increased in response to clipping and nitrogen addition. Nebraska sedge (Carex nebrascensis Dewey), a desirable native, increased in response to both release from grazing and nitrogen addition. The results were influenced by high spatial and temporal variability in water table elevations within these systems.