Lisa Y. Yager

Gopher Tortoise Response to Habitat Management by Prescribed Burning

Abstract As quality of forested habitat declines from altered fire regimes, gopher tortoises (Gopherus polyphemus) often move into ruderal areas to the detriment of the animal and land manager. We evaluated effects of a dormant-and-growing-season prescribed fire on habitat and gopher tortoise use of degraded longleaf pine (Pinus palustris) forests surrounding military training areas. We burned 4 of 8 sites in winter 2001–2002 and again in April 2003. Changes in vegetation measured during 2001–2004 indicated that burn treatments did not increase herbaceous vegetation. Similarly, movement patterns, burrow usage, and home range of tortoises radiotracked from 2002–2004 did not differ between treatments. Woody cover initially was reduced in the forests postburn, and we found more new burrows in burned forest sites. Once shrub cover was reduced, tortoises started using forested habitat that had become overgrown. However, shrub reduction may be temporary, as woody stem densities increased postburn. Thus, the one-time use of fire to manage tortoise habitat may not rapidly restore the open canopy, sparse woody midstory, and abundant herbaceous vegetation that this species requires. Repeated prescribed fires or additional management techniques may be needed for complete restoration.

MID-TEXAS, USA COASTAL MARSH VEGETATION PATTERN AND DYNAMICS AS INFLUENCED BY ENVIRONMENTAL STRESS AND SNOW GOOSE HERBIVORY

Vegetation pattern and dynamics were characterized across a mid-Texas, USA coastal marsh ecotone subjected to snow goose herbivory, drought, and salt-water pulses. For eight years following snow goose feeding, species cover was evaluated in heavy and light goose-use patches at increasing distances from tidal influence. Just prior to and for two years after the feeding event, drought, and several salt-water pulses associated with tropical storms typified the hydrologic dynamics of the marsh. Herbivory history was more important than distance from tidal influence, salinity, or flooding in explaining spatial and temporal vegetation pattern for three years. Precipitation variation influenced vegetation dynamics in areas heavily used by geese. Recovery to pre-herbivory composition and abundance required six years without further snow goose feeding. Extremes of annual precipitation, salinities, and water levels impacted cover of Spartina patents dominated patches little unless feeding snow geese uprooted vegetation. Schoenoplectus americanus was more impacted by extremes of environmental dynamics than S. patens but even more impacted by synergistic effects of uprooting and environmental extremes. During this period, the ecotone could be characterized as patchy, with a gulfward waxing and waning of S. americanus.

Susceptibility of Longleaf Pine Forest Associations in South Mississippi to Invasion by Cogongrass [Imperata cylindrica (L.) Beauv.]

ABSTRACT: If fire affects spread of cogongrass (Imperata cylindrica), a non-native grass that displaces native plants, managers can determine best use of resources to restore and maintain the diverse herbaceous groundcovers of longleaf pine-bluestem (Pinus palustris - Andropogon spp. and Schizachyrium spp.) forests of the southeastern United States. In 2003 and 2004, we measured rates of vegetative encroachment of cogongrass into burned and unburned pine-bluestem and pine-shrub forests one and two years post-burning on Camp Shelby Training Site, Mississippi. Linear growth and tiller production were significantly greater in pine-bluestem forests compared to pine-shrub forests for both time periods. Cogongrass growth was not affected by burning in either forest type one-year post-burning, but was significantly greater in burned forests after two years of growth. Two-years post-burning, mean linear growth of cogongrass was 235 cm in burned pine-bluestem, 139 cm in unburned pine-bluestem, 177 cm in burned pine-shrub, and 92 cm in unburned pine- shrub. Tiller production/m2 for 2004 was greatest in pine-bluestem burned plots and least in pine-shrub unburned plots. Linear growth of cogongrass was significantly and positively correlated to percent cover of adjacent herbaceous vegetation but tiller numbers were significantly and negatively correlated to percent cover of adjacent shrubs. Efforts to restore pine-shrub forests to pine-bluestem forest conditions should implement control of cogongrass before and after use of Are. Vigilant control efforts are needed as restoration shifts conditions to those of pine-bluestem forests and increases susceptibility to cogongrass invasion.

Woody shrubs as a barrier to invasion by cogongrass (Imperata cylindrica).

Abstract Cogongrass invades forests through rhizomatous growth and wind-dispersed seeds. Increased density and abundance of woody vegetation along forest edges may strengthen biotic resistance to invasion by creating a vegetative barrier to dispersal, growth, or establishment of cogongrass. We evaluated differences in dispersal of cogongrass spikelets experimentally released from road edges into tallgrass-dominated and shrub-encroached longleaf pine forests (Pinus palustris). Average maximum dispersal distances were greater in the pine–tallgrass forest (17.3 m) compared to the pine–shrub forest association (9.4 m). Spikelets were more likely to be intercepted by vegetation in pine–shrub forests compared to pine–tallgrass forests. Results suggest that dense woody vegetation along forest edges will slow spread from wind-dispersed cogongrass seeds. Nomenclature: Bluestem grasses, Andropogon spp., Schizachyrium spp.; cogongrass, Imperata cylindrica (L.) Beauv.; longleaf pine, Pinus palustris Mill Interpretative Summary: It has been suggested that dense woody vegetation along forest edges may form a barrier to invasive species either through effects on microhabitat or effects on seed dispersal. This study evaluated use of dense woody vegetation along forest edges as a barrier to seed dispersal into forest interiors. In this study, more cogongrass spikelets dispersed farther into open longleaf pine forests with a tallgrass understory compared to longleaf pine forests with dense shrubby understories. Reduced wind speed and increased vegetative interception of spikelet in the shrub-encroached forests may have prevented greater dispersal into these forests. However, a few spikelets released into open or shrubby forests dispersed farther than could be measured. These results suggest that managers seeking to control cogongrass may benefit by maintaining dense woody edges along forests and prioritizing management techniques that prevent spread of or treat cogongrass growing near less densely wooded habitats. These results also suggest that although dense woody vegetation may slow spread of cogongrass into forest interiors, such vegetation is unlikely to completely prevent invasion. Therefore, managers will need to implement additional control techniques in order to protect these forested areas from invasion.

Military Training and Road Effects on Imperata cylindrica (L.) Beauv. (Cogongrass)

Abstract Type, level, and intensity of human activities may facilitate establishment and spread of invasive plant species. A better understanding of how human activities influence invasion can assist land managers in developing strategies for control and monitoring of invasive plants. Spread of the invasive species Imperata cylindrica (Cogongrass) has been attributed to human activities. During 2002–2004, on Camp Shelby Training Site, MS, we investigated relationships between military activity and establishment and growth of Cogongrass. In areas of soil disturbance from military equipment, vegetative linear growth rates of 7–10 m yr-1 were recorded on firing points. There was a positive relationship between military troop use and Cogongrass establishment on firing points for one of the 2 years of the study (P = 0.023). Thus, steps to minimize soil disturbance in and near Cogongrass may reduce spread. We examined frequency of Cogongrass infestation and vegetative growth rates for roadside areas along gravel roads subject to at least annual mowing and grading, and dirt tracks receiving infrequent maintenance. Cogongrass spread and establishment on roadsides did not differ for the two road types (P ≥ 0.116). These results may reflect activities already in place to reduce disturbance of Cogongrass patches.

Use of GIS to Prioritize Cogongrass (Imperata cylindrica) Control on Camp Shelby Joint Forces Training Center, Mississippi

Abstract Geographic information systems (GIS) analysis considering size and spatial distribution of infestations of invasive species on a landbase can assist with developing appropriate control strategies for that species. We used GIS to evaluate strategies that placed highest priority on: smallest patches of cogongrass, largest patches of cogongrass, and cogongrass patches on land considered high-value under military training and conservation priorities on Camp Shelby Joint Forces Training Center (CSJFTC), MS. Strategies were first evaluated using predicted increase in area of new growth prevented, if prioritized patches were treated with herbicide. Travel and other time needed to implement strategies were then assessed as they affected total area treated. Assuming equivalent areas treated, predicted total reduction in area was consistently highest for the strategy prioritizing smallest patches and lowest for the strategy prioritizing largest patches. However, travel and other time was sufficiently reduced for the strategy prioritizing patches on high-value land compared to the other strategies to suggest that this strategy would result in the greatest reduction in area infested with cogongrass. Analyses of spatial distribution and size of infestations can assist land managers with selecting the appropriate strategy for controlling invasive species. Nomenclature: Cogongrass, Imperata cylindrica (L.) Beauv.

Selected Non-native Plants of Rights-of-Ways (ROWs) in the Southeastern United States and Associated Impacts

Publisher Summary This chapter discusses the characteristics and management of three genera of beneficial non-native plants and four species of invasive non-native plants. Over thirty species of non-native, herbaceous and semi-woody plants may be present on road, pipeline, and utility rights-of-way (ROWs) in the southeastern United States. The ecological and economic impacts of these species vary depending on vegetation competition and colonization trends, wildlife food and cover value, and livestock forage value. Some plants, such as annual lespedezas and clovers, are non-native species that are naturalized in southeastern habitats. These plants have value for livestock and wildlife forage, soil stabilization, and soil-quality enhancement with limited negative impacts to natural communities. Some species, such as sericea lespedeza and tall fescue, were originally planted for soil stabilization, but these species have limited value for most species of wildlife and can limit native plant diversity. Of greatest concern are the highly invasive introduced plants, such as cogongrass and kudzu. Originally introduced through intentional planting in some areas, these species are now established in dense colonies on thousands of hectares of ROWs. After establishment, these species limit native biological diversity, degrade wildlife habitat quality, and reduce property values. Colonization studies indicate that cogongrass spread is enhanced by management that creates bare soil and transfers vegetative propagules to new sites. Because of the life strategies of many non-native invasive species, newly constructed and maintained ROWs can serve as corridors for dispersal of these species. Early detection and integrated pest management are important in the cost-effective control of invasive perennial plants.