Eileen M. Kirsch

Effects of a Selective Herbicide, Sethoxydim, on Reed Canarygrass

JUNE 2005 99 Reed canarygrass (Phalaris arundinacea) is a cool-season, perennial grass that threatens the diversity of native wetland vegetation, particularly in sedge meadows and wet prairies (Galatowitsch and others 1999). This widely distributed species forms dense monocultures capable of displacing native vegetation and altering restoration trajectories (Apfelbaum and Sams 1987, Galatowitsch and others 2000, Maurer and others 2003). Field managers and researchers have tested a variety of methods to control reed canarygrass, including flooding, manual removal, tarping, removal and replacement of topsoil, cultivating, mowing, reverse fertilization, controlled burns, and application of herbicides (Hodgson 1968, Comes and others 1981, Apfelbaum and Sams 1987, Gillespie and Murn 1992, Hutchison 1992, Lyford 1993, Preuninger and Umbanhowar 1994, Kilbride and Paveglio 1999, Paveglio and Kilbride 2000, Perry and Galatowitsch 2002). The relative success of each control method often depends on site factors, such as size of the native seed bank, local hydrology, frequency and severity of disturbance regimes, extent of invasion, and potential for subsequent reinvasion when control measures are discontinued. In general, efforts to eradicate reed canarygrass have had limited long-term success. Hutchison (1992) suggested that reed canarygrass control is problematic because of a lack of selective treatments. Moderate, short-term success in controlling reed canarygrass has been achieved with herbicides (Hodgson 1968, Comes and others 1981, Apfelbaum and Sams 1987, Hutchison 1992, Kilbride and Paveglio 1999, Paveglio and Kilbride 2000). Few herbicides have been thoroughly evaluated for this purpose, however. In addition, chemical control of reed canarygrass is often hindered by the use of nonselective (broad-spectrum) herbicides, such as glyphosate (Roundup) and imazapic (Plateau) (Lovett-Doust and Lovett-Doust 1995). Nonselective herbicide applications can result in weed resurgence (Strand 1993) because an aggressive species may expand in response to open space created by the removal of non-target species. Some managers apply broad-spectrum herbicides after native species have set seed to minimize risks to populations of non-target species (Paveglio and Kilbride 2000). However, this timing schedule varies among non-target species and may not match the optimum window for reed canarygrass control. Pizzo and Schroeder (2001) recommended treating reed canarygrass with a low concentration of glyphosate to avoid collateral damage to native species. But, Comes and others (1981) have previously demonstrated that lower levels of control are achieved when low concentrations of glyphosate are used. Thus, it would seem that finding selective herbicide treatments for reed canarygrass would be beneficial to control efforts, which is why we decided to test sethoxydim. Effects of a Selective Herbicide, Sethoxydim, on Reed Canarygrass

Control of Reed Canarygrass Promotes Wetland Herb and Tree Seedling Establishment in an Upper Mississippi River Floodplain Forest

Phalaris arundinacea (reed canarygrass) is recognized as a problematic invader of North American marshes, decreasing biodiversity and persisting in the face of control efforts. Less is known about its ecology or management in forested wetlands, providing an opportunity to apply information about factors critical to an invader’s control in one wetland type to another. In a potted plant experiment and in the field, we documented strong competitive effects of reed canarygrass on the establishment and early growth of tree seedlings. In the field, we demonstrated the effectiveness of a novel restoration strategy, combining site scarification with late fall applications of pre-emergent herbicides. Treatments delayed reed canarygrass emergence the following spring, creating a window of opportunity for the early growth of native plants in the absence of competition from the grass. They also allowed for follow-up herbicide treatments during the growing season. We documented greater establishment of wetland herbs and tree seedlings in treated areas. Data from small exclosures suggest, however, that deer browsing can limit tree seedling height growth in floodplain restorations. Slower tree growth will delay canopy closure, potentially allowing reed canarygrass re-invasion. Thus, it may be necessary to protect tree seedlings from herbivory to assure forest regeneration.

Breeding bird territory placement in riparian wet meadows in relation to invasive reed canary grass, Phalaris arundinacea.

Invasive plants are a growing concern worldwide for conservation of native habitats. In endangered wet meadow habitat in the Upper Midwestern United States, reed canary grass (Phalaris arundinacea) is a recognized problem and its prevalence is more widespread than the better-known invasive wetland plant purple loosestrife (Lythrum salicaria). Although resource managers are concerned about the effect of reed canary grass on birds, this is the first study to report how common wet meadow birds use habitat in relation to reed canary grass cover and dominance. We examined three response variables: territory placement, size of territories, and numbers of territories per plot in relation to cover of reed canary grass. Territory locations for Sedge Wren (Cistothorus platensis) and Song Sparrow (Melospiza melodid) were positively associated with reed canary grass cover, while those for Common Yellowthroat (Geothlypis trichas) were not. Only Swamp Sparrow (M. georgiana) territory locations were negatively associated with reed canary grass cover and dominance (which indicated a tendency to place territories where there was no reed canary grass or where many plant species occurred with reed canary grass). Swamp Sparrow territories were positively associated with vegetation height density and litter depth. Common Yellowthroat territories were positively associated with vegetation height density and shrub cover. Song Sparrow territories were negatively associated with litter depth. Reed canary grass cover within territories was not associated with territory size for any of these four bird species. Territory density per plot was not associated with average reed canary grass cover of plots for all four species. Sedge Wrens and Song Sparrows may not respond negatively to reed canary grass because this grass is native to wet meadows of North America, and in the study area it merely replaces other tall lush plants. Avoidance of reed canary grass by Swamp Sparrows may be mediated through their preference for wet areas where reed canary grass typically does not dominate.

Assessing Habitat Use by Breeding Great Blue Herons (Ardea herodias) on the Upper Mississippi River, USA

Abstract Approximately 7,610 to 3,175 pairs of Great Blue Herons (Ardea herodias) nested along 420 river km of the Upper Mississippi River (UMR) from 1993 to 2003. Numbers declined precipitously in the mid-1990s stabilizing somewhat in the early 2000s. The average number of nests in colonies was 349 (SD = 283). Annual colony turn over rate for the eleven year period was 0.15 and ranged from 0.06 to 0.29 each year. The number of years that a colony was active was positively correlated with the average number of nests present while the colony was active. Of the eight colonies active in 1993 that averaged more than 349 nests, four were abandoned by 2003. Only one colony grew to greater than 349 nests during the study period. Custer et al. (2004) suggested that herons on the UMR may be limited by forage resources or foraging habitat and social factors, as evidenced by the even spacing of colonies that reflects the maximum feeding range of herons on the river. To rule out nesting and foraging habitat limitation, landscape habitat features of terrestrial and aquatic areas were examined for colony areas and areas without colonies. Available fish monitoring data were used to examine potential interactions between herons and forage resources. Colony areas did not differ from areas without colonies in any habitat feature. Indices of potential heron forage fish increased from 1993 to 2002, although low indices of fish abundance in 1993 were likely influenced by flood conditions that year. Although fish availability to herons is related to flows and water levels, available data suggested that herons did not negatively impact their potential forage base. Numbers of herons were not correlated with indices of fish abundance from the preceding year on a pool-wide scale. Indices of fish abundance were higher within 5 km of colonies than farther than 5 km from colonies, and indices of fish abundance increased from June through August both near and far from colonies. Numbers of herons and locations and sizes of colonies varied annually, whereas landscape features typically vary little if at all from year to year. Indices of fish abundance also varied greatly by sample location and year. Disturbance, particularly by humans in this highly used river, should be examined in relation to limiting foraging opportunities and influencing behavior (colony and individual) and productivity in colonies.

Songbird use of Floodplain and Upland Forests Along the Upper Mississippi River Corridor During Spring Migration

Abstract. The Upper Mississippi River is thought to provide important stopover habitat for migrating landbirds because of its north-south orientation and floodplain forests. The river flows through the Driftless Area of southwestern Wisconsin and southeastern Minnesota where forests are plentiful, yet forests of the floodplain and Driftless Area uplands differ greatly in landscape setting, tree species composition, and topography. We compared landbird assemblages in these upland and floodplain forests over three springs, 2005–2007, using line-transect surveys at randomly selected areas in and within 16 km of the floodplain. We found more species of both transient and locally breeding migrants per survey in floodplain than in upland forest. Detections of transient neotropical migrants did not differ statistically by habitat. Detections of locally breeding neotropical and temperate-zone migrants and transient temperate-zone migrants were greater in floodplain than in upland forest. Between floodplain and upland forest, assemblages of locally breeding species, including neotropical and temperate-zone migrants (of which some individuals were in transit), differed substantially, but assemblages of transients (including both neotropical and temperate-zone migrants) did not differ as much. Only two species of transient migrants had clear affinities for floodplain forest, and none had an affinity for upland forest, whereas most locally breeding migrants had an affinity for either upland or floodplain forest. Within each spring, however, detections of transient neotropical migrants shifted from being greater in floodplain to greater in upland forests. This intraseasonal shift may be related to the phenology of certain tree species.

Vermillion/Cannon River Bottoms Important Bird Area Raw Breeding bird data

We sampled vegetation and breeding birds in Upper Mississippi River floodplain forest edge and interior areas to (1) measure Phalaris cover and (2) evaluate if the breeding bird assemblage responded to differences in Phalaris cover or other forest structure variables. Data are counts of birds collected during 3 surveys within 50m at each site using 10 minute point count methods. Vegetation was sampled using a releve technique at the bird count point within 10m of the point.

Differences in Breeding Bird Assemblages Related to Reed Canary Grass Cover and Forest Structure on the Upper Mississippi River

Abstract Floodplain forest of the Upper Mississippi River provides habitat for an abundant and diverse breeding bird community. However, reed canary grass Phalaris arundinacea invasion is a serious threat to the future condition of this forest. Reed canary grass is a well-known aggressive invader of wetland systems in the northern tier states of the conterminous United States. Aided by altered flow regimes and nutrient inputs from agriculture, reed canary grass has formed dense stands in canopy gaps and forest edges, retarding tree regeneration. We sampled vegetation and breeding birds in Upper Mississippi River floodplain forest edge and interior areas to 1) measure reed canary grass cover and 2) evaluate whether the breeding bird assemblage responded to differences in reed canary grass cover. Reed canary grass was found far into forest interiors, and its cover was similar between interior and edge sites. Bird assemblages differed between areas with more or less reed canary grass cover (>53% cover breakp...

Numbers and distribution of Double-crested Cormorants on the upper Mississippi river

-Historic records indicate that Double-crested Cormorants (Phalacrocorax auritus) were common breeders and abundant during migration on the Upper Mississippi River from St. Paul, Minnesota, to St. Louis, Missouri, during the 1940s and 1950s. Their numbers declined in the midto late-1950s, remained low through the 1970s, and began to increase somewhat in the late 1980s. Aerial surveys of migrating cormorants and ground surveys at cormorant colonies during 1991-1993, indicate that numbers have not returned to historic levels. Only 500-2,000 cormorants were seen during spring migration 1992-1993; and 5,000-7,000 during fall migration 1991-1992; whereas, tens of thousands were reported in the 1940s and 1950s. Four hundred ninety-six nests were counted at 4 colonies in 1992, and 545 nests were counted in 9 colonies in 1993; whereas, during the 1940s and 1950s, about 2,500 birds were reported nesting in 4 locations. Pools 6 and 13 have always attracted breeding and migrating cormorants, currently attract the largest numbers of cormorants during migration, and still support breeding colonies. Received 26 September 1996, accepted 1 9January 1997.