Greentree Reservoir Research Articles

Forest composition and red oak (Quercus sp.) response to elevation gradients across greentree reservoirs

Elevation gradients within forested wetlands have long been recognized for their role in defining species composition through factors such as hydrology and soil characteristics. Greentree reservoirs (GTRs) are levee-impounded tracts of bottomland hardwood forest flooded throughout the winter months to provide habitat for overwintering waterfowl. Artificial flooding of GTRs alters the forest composition due to flood frequency, depth, and duration in combination with slight changes in topography. To evaluate the effect of elevation gradients, soil properties, and management techniques in the overstory species composition and red oak (Quercus spp.) species abundance, we inventoried 662 plots across 12 independent GTRs in eastern Arkansas. In the lower elevations ranging from 50.98 to 54.99 ​m above sea level, the importance value index (IVI) was highest for nuttall oak (Quercus texana) and overcup oak (Quercus lyrata), whereas IVI shifted to cherrybark oak (Quercus pagoda) in the higher elevations ranging from 54.99 to 58.00 ​m. Alpha diversity did not differ by elevation gradient, soil property, or management technique within GTRs. Beta diversity, using non-metric multi-dimensional scaling (NMDS) analysis, indicated site-specific variability significantly correlated with the environmental predictors, including elevation (R2 = ​0.57), easting (R2 = ​0.47), soil texture (R2 = ​0.21), and pH (R2 = ​0.12). Red oak species-specific mixed-effects modeling of abundance response using Poisson distribution suggested an inverse correlation of nuttall oak and a direct correlation of cherrybark oak abundance with elevation. However, willow oak (Quercus phellos) abundance was not significantly affected by elevation but was by silt loam soil texture and restoration management techniques. These findings will aid management efforts to reduce the dominance of less desirable species that are prominent under specific environmental conditions and promote the dominance of more desirable species. Ultimately GTR sustainability is increasingly important amid the unpredictable impacts of climate change on the preferred red oak species that are economically, ecologically, and environmentally valuable to the sustaining economy of the local community and managing habitats for wildlife.

The Influence of Dormancy Break Requirements on Germination and Viability Responses to Winter Submergence in Acorns of Three Bottomland Red Oak (Sect. Lobatae) Species

Abstract The objective of this study was to examine the relation of dormancy break requirements to winter submergence effects on germination and viability in cherrybark, willow, and Nuttall oak acorns. Acorns were submerged in a greentree reservoir and received 0, 21, 42, 63, or 84 days of winter submergence, followed by 8 weeks of incubation in four temperature regimes (15/6°, 20/10°, 25/15°, and 30/20° C). Winter submergence substituted for cold stratification requirements of cherrybark oak acorns, and dormancy break was achieved with 63 days of submergence. Although winter submergence exerted a positive effect on germination in Nuttall and willow oak acorns, dormancy break was not achieved in acorns of either species. Germination percentages were highest in the 30/20° C incubation temperature—cherrybark oak acorns (75–83 percent), followed by Nuttall oak (33–55 percent) and willow oak (14–52 percent). Among treatment combinations, all willow oak nongerminants were viable. Viability loss in cherrybark and Nuttall oak acorns was greatest in the 63- and 84-day treatments. The dynamics of acorn germination in response to winter hydrologic regime is influenced by submergence duration that may, or may not, satisfy dormancy break requirements in acorns of these red oak species.

Aquatic Invertebrate Abundance and Biomass in Arkansas, Mississippi, and Missouri Bottomland Hardwood Forests During Winter

AbstractThe Mississippi Alluvial Valley once had extensive bottomland hardwood forests, but less than 25% of the original area remains. Impounded bottomland hardwood forests, or greentree reservoirs, and naturally flooded forests are important sources of invertebrate or other prey for waterfowl, but no previous studies of invertebrate abundance and biomass have been at the scale of the Mississippi Alluvial Valley. Additionally, the Lower Mississippi Valley Joint Venture of the North American Waterfowl Management Plan requires precise, contemporary estimates of invertebrate biomass in hardwood bottomlands to determine potential foraging carrying capacity of these habitats for wintering ducks. We used sweep nets to collect aquatic invertebrates from four physiographically disjunct hardwood bottomlands in the Mississippi Alluvial Valley and Mississippi's Interior Flatwoods region during winters 2008–2010. Invertebrate abundance varied inversely with water depth in both early and late winter, with greatest abundances in depths ranging from 10 to 20 cm. The estimate of invertebrate biomass in naturally flooded forests of the Mississippi Alluvial Valley for both years combined was 18.39 kg(dry)/ha (coefficient of variation [CV] = 15%). When we combined data across regions, sites, greentree reservoirs and naturally flooded forests, and years, the estimate of mean invertebrate biomass decreased to 6.6 kg/ha but precision increased to CV = 9%. We recommend the Lower Mississippi Valley Joint Venture adopt 18.39 kg(dry)/ha as a revised estimate for invertebrate biomass for naturally flooded forests, because this estimate is reasonably precise and less than 2% of remaining hardwood bottomland is impounded greentree reservoirs in the Mississippi Alluvial Valley. Additionally, we recommend managing to invoke dynamic flooding regimes in greentree reservoirs to mimic natural flood events and provide maximal coverage of depths less than 30 cm to facilitate foraging ducks' access to nektonic and benthic invertebrates, acorns, and other natural seeds.

Tree Growth and Mortality During 20 Years of Managing a Green-Tree Reservoir in Arkansas, USA

Green-Tree Reservoirs (GTR) are bottomland hardwood forests that are flooded during late fall and winter to provide waterfowl habitat. Early reports suggested that increased moisture improved tree growth and mast production; however, recent reports showed reduced vigor and growth. This study examines the effects of 20 years of GTR management practices in the Felsenthal National Wildlife Refuge, Crossett, Arkansas. Tree species composition, size characteristics, and vigor classes were measured in 1990, 1995, 2001, and 2006. The overall annual tree mortality rate was 2.6%, with high elevations at 1.7% and low elevations at 3.1%. Annual mortality rates exceeded 3% for willow oak (Quercus phellos) and water hickory (Carya aquatica), while rates for Nuttall oak (Q. texana), overcup oak (Q. lyrata), and sweetgum (Liquidambar styraciflua) were lower at 2.8, 2.4, and 1.5%, respectively. Tree health (vigor) has degraded substantially for over 60% of trees initially rated in good or fair condition. Statistical probit models were generated to predict short-term (5 years) and long-term (15 years) vigor degradation. Low numbers of saplings and little advanced regeneration indicated lack of tree replacement, suggesting that inundation strategies of the GTR management may have long-term impacts on forest structure and composition in the southeastern United States.

Tree Growth and Mortality During 20 Years of Managing a Green-Tree Reservoir in Arkansas, USA

Tree Growth and Mortality During 20 Years of Managing a Green-Tree Reservoir in Arkansas, USA

Plant community establishment following drawdown of a reservoir in southern Arkansas, USA

Wetland area, function and wildlife habitat value are extensively altered by the construction of freshwater reservoirs. We studied the effects of a temporary drawdown on shoreline vegetation communities of Felsenthal Navigation Pool (“the pool”), an impoundment at Felsenthal National Wildlife Refuge in southern Arkansas that is managed as a greentree reservoir. The pool was permanently flooded from 1985 until the summer of 1995 when the water level was dropped 0.3 m for about 16 weeks, exposing about 1,591 ha of soil. To document plant succession on the sediments exposed, we recorded plant species composition and cover at 14 transects along the pool margin prior to the drawdown, during the drawdown, and in the following summer. A soil disturbance treatment was applied near five transects following the drawdown, and soil was collected at each transect for seed bank and soil analyses. Plants colonized the drawdown zone quickly and high vegetation cover was present at some transects 4 weeks after the drawdown was initiated. Plants included species that are high quality food sources for waterfowl, including Cyperus erythrorhizos and Leptochloa fascicularis var. fascicularis. Vegetation response, measured by species richness, total cover, and cover of Cyperus species, was often greater at low compared to high elevations in the drawdown zone; this effect was probably intensified by low summer rainfall. Response on the disturbed transects was lower than that on the undisturbed transects. This effect was attributed to two factors: (1) removal of the existing seed bank by the disturbance applied and (2) reduced incorporation of seeds recruited during the drawdown because of unusually low rainfall. Seed bank studies demonstrated that several species persisted despite 10 years of continual flooding, and that seed bank species richness increased during the drawdown. Although conclusions are limited by the 1-year time frame of the study, it is unlikely that permanent change to plant community structure in the drawdown zone resulted from the lowered water level.

Influence of Long-term Greentree Reservoir Impoundment on Stand Structure, Species Composition, and Hydrophytic Indicators1

Greentree reservoir management was initiated during a period when riparian forests of the Mississippi Alluvial Valley were disappearing rapidly. Greentree reservoirs (GTRs) were intended to provide a refuge for overwintering migratory waterfowl within a landscape of decreasing habitat availability. However, GTRs frequently are flooded as much as 2.5 months longer than unimpounded bottomland forests (UBF), and previous work has shown that such unnatural hydroperiods can have substantial negative effects on such ecosystem attributes as tree assemblage composition and invertebrate production. We conducted the present study to quantify (1) frequency of canopy gaps and (2) tree species composition in GTRs, as compared with UBFs. In general, GTRs were quite similar to UBF stands, in terms of canopy density, proportion of trees in the canopy versus mid-story, degree of stress exhibited by individual trees, gap frequency, and species diversity. However, multivariate comparisons of GTRs versus unimpounded areas indicated differences in species composition. Indicator Species Analyses and examination of the dominant species showed clear differences between GTRs and UBFs, with GTR tree species being, on average, better adapted to flooded conditions, based on wetland indicator status. Greentree reservoir canopies generally were dominated by a Taxodium distichum – Acer rubrum – Quercus lyrata mix, whereas unimpounded forest canopies were characterized as Liquidambar styraciflua – mixed Quercus stands. The midstories of the groups were more similar to one another, with dominance by Acer– Carpinus caroliniana – Planera aquatica in GTRs and Liquidambar – Carpinus – Acer in unimpounded stands. The GTRs included in this study had been managed for 40 to 48 years, providing a long history of flooding which served to select for highly adapted species assemblages.

DIET OF MALLARDS WINTERING IN GREENTREE RESERVOIRS IN SOUTHEASTERN ARKANSAS

Loss of wetlands to agriculture and development negatively impacts waterfowl. Greentree reservoirs are forested tracts that are purposefully flooded to increase hunting opportunities for sportsman and to provide shelter for waterfowl such as Mallards (Anas platyrhynchos). These human-made wetlands can also make natural foods such as acorns and invertebrates available to Mallards. Food habits analysis conducted in 1959 indicated acorns composed 24% of the volume of diets of Mallards collected from a variety of habitats including agricultural fields, naturally flooded bottomland forests, and greentree reservoirs in Arkansas. However, changes that may have occurred in food use by Mallards in bottomland hardwood habitats in Arkansas since last examined are unclear. We examined foods used by Mallards in greentree reservoirs from November 1990 to February 1991 in southeastern Arkansas. Seventeen species of plants and 21 families/orders of animals occurred in the diet of Mallards. Mallards consumed 65% plant matter, primarily seeds of narrowleaf foresteria (Foresteria angustifolia), Nuttall oak (Quercus nuttallii), Pennsylvania smartweed (Polygonum pensylvanicum), and rice (Oryza sativa). Invertebrate taxa, constituting 6% or more of the sample by both volume and mass, included the orders Coleoptera, Diptera, and Isopoda. Diets of Mallards present in greentree reservoirs in our study indicate Mallards still use natural foods, though agricultural seeds were in close proximity to natural foods.

Long-term effects of a lock and dam and greentree reservoir management on a bottomland hardwood forest

We investigated the long-term effects of a lock and dam and greentree reservoir management on a riparian bottomland hardwood forest in southern Arkansas, USA, by monitoring stress, mortality, and regeneration of bottomland hardwood trees in 53 permanent sampling plots from 1987–1995. The lock and dam and greentree reservoir management have altered the timing, depth, and duration of flooding within the wetland forest. Evaluation of daily river stage data indicates that November overbank flooding (i.e. 0.3 m above normal pool) of 1 week duration occurred only 10 times from 1950 to 1995 and four of these occurrences were the result of artificial flooding of the greentree reservoir. Results of the vegetation study indicate that the five most common dominant and co-dominant species were overcup oak, water hickory, Nuttall oak, willow oak, and sweetgum. Mortality of willow oak exceeded that of all other species except Nuttall oak. Nuttall oak, willow oak, and water hickory had much higher percentages of dead trees concentrated within the dominant and co-dominant crown classes. Probit analysis indicated that differences in stress and mortality were due to a combination of flooding and stand competition. Overcup oak appears to exhibit very little stress regardless of crown class and elevation and, with few exceptions, had a significantly greater probability of occurring within lower stress classes than any other species. Only 22 new stems were recruited into the 5 cm diameter-at-breast height size class between 1990–1995 and of these, three were Nuttall oak, three were water hickory, and one was sweetgum. No recruitment into the 5 cm diameter-at-breast height size class occurred for overcup oak or willow oak. The results of the study suggest that the forest is progressing to a more water-tolerant community dominated by overcup oak. A conservative flooding strategy would minimize tree stress and maintain quality wildlife habitat within the forested wetland.

Effects of flooding on the forest community in a greentree reservoir 18 years after flood cessation

Greentree reservoir (GTR) management is a common waterfowl habitat management technique used in both the northeastern and southeastern United States. However, this management technique is controversial because greentree reservoir management can cause changes in forest composition and structure. We studied the effects of GTR management at the Montezuma National Wildlife Refuge in central New York by comparing vegetation in permanent plots in two GTRs and a natural forest wetland over 30-year period (preflood and 2 years and 18 years after flood cessation). We detected long-term effects of GTR management on vegetation composition and structure. Red maple and green ash remained the dominant overstory species, but density of green ash saplings was higher (P=0.026) in a natural forested wetland (300 trees/ha) compared to the two GTRs (30–90 trees/ha). Age determinations of several green ash saplings suggest these changes were likely caused by reduced regeneration in the GTRs. Mortality of green ash seedlings in 1996 was greatest in a GTR flooded for 1 year (60%) versus an unflooded GTR (12%) and a natural forested wetland (27%). Overall, shrub density was similar 18 years post-flooding and preflooding, but several species had lower densities (P=0.001–0.031) than a natural forested wetland. Shannon-Weiner diversity index (1.8–2.0) and richness (29–31) of herbaceous species were similar among all sites 18 years after flood cessation. However, two species of fern remained at lower densities (P=0.0001–0.026), while three herbaceous species remained at higher densities (P=0.0001–0.015) 18 years after flood cessation as compared to preflood densities and densities in a natural forested wetland. It is unknown after which year of flooding these changes occurred, but 12 years of GTR management did cause long-term effects on the forest community.

Plant succession and greentree reservoir management: implications for management and restoration of bottomland hardwood wetlands

Bottomland hardwood forests are distributed along rivers and streams throughout the central and eastern United States, with the greatest concentration in the Southeast. Past and projected losses of bottomland hardwoods and degradation of remaining stands suggest that habitat management and/or restoration strategies that target multiple species and multiple uses will be necessary to maintain, enhance, and restore flora and fauna within bottomland hardwood wetlands. A greentree reservoir is a current management strategy that entails manipulating water regimes to provide habitat for wintering waterfowl. We conducted a literature review and synthesis to determine the potential impacts of greentree reservoir management on plant succession within bottomland hardwood wetlands. Greentree reservoirs can impact vegetation establishment through several processes. Despite shortcomings of greentree reservoirs, designs similar to them could be very beneficial in restoring bottomland hardwood plant and animal communities from degraded forests provided water-level control and maintenance are substantially improved. Emulation of natural hydrologic regimes, including natural variability, could produce diverse bottomland hardwood plant communities and provide habitat for a variety of wildlife species.

Wetlands Mitigation: Partnership Between an Electric Power Company and a Federal Wildlife Refuge

/ Nine hectares (23 acres) of a degraded section of Patuxent Research Refuge in Laurel, Maryland, USA, were converted to wetland habitat by the Baltimore Gas and Electric Company in 1994. The wetlands were created as mitigation for 5.7 ha (14 acres) of wetlands that were impacted as part of the construction of an 8.5-km (5.3-mile) 500-kV overhead transmission line on the refuge. The area consists of a created forested wetland of 5.5 ha (13.5 acres), a seasonally inundated green-tree reservoir of 7.6 ha (6.5 acres), and an impounded pond wetland of 1.2 ha (3 acres). Construction included the planting of 6131 trees, 4276 shrubs, and 15,102 emergent plants. Part of the site has been studied intensively since completion and survival of trees and shrubs after two years was 88%. Measurements of these transplants have shown growth greater than on other created sites in Maryland. Grasses and other herbaceous vegetation were dominant plants in the meter-square plots in the first two years of sampling of the created forested wetland. Wildlife surveys for birds, mammals, amphibians, and reptiles have revealed diverse communities. Although these communities represent species consistent with open habitat, more typical forest species should colonize the area as it undergoes succession into a more mature forested wetland. The creation, management, and research of this mitigation site represents an excellent example of a partnership between a private electric power company and a federal wildlife refuge. This partnership has increased local biodiversity and improved regional water quality of the Patuxent River and the Chesapeake Bay.KEY WORDS: Wetlands; Mitigation; Wildlife; Partnership; Biodiversity

A simulation model of the impacts of green-tree reservoir management on bottomland hardwood seedling growth and survival

Green-tree reservoirs are stands of bottomland hardwoods that are impounded with levees, equipped with water control structures, and flooded during the fall and winter to provide mast and invertebrates for waterfowl. We developed a model to evaluate the potential impacts of green-tree reservoir management on seedling growth and survival of three bottomland hardwood species (overcup oak, water elm, and willow oak). The model is a compartment model based on difference equations with a time step of 6 months and operates on a microcomputer. Each species is represented by two series of 10 state variables representing the number and height of seedlings, respectively, in age-classes from 1 to 10 yr. Seedling growth is a function of the length of flooding during the growing season and light availability; seedling survival is a function of these 2 parameters as well as the depth of flooding during the dormant-season. The model ordinates the relative growth rates of the three species accurately based upon flood tolerances described in the literature. Simulations indicate that changes in the length of flooding during the growing season, flood depth during the dormant season, and light availability influence both the composition and abundance of regeneration of bottomland hardwood species. Regeneration of all species was reduced as either the length of flooding during the growing season, light availability, or dormant season flood depth approached an extreme for that species, regardless of the values of the other environmental gradients. Our model, with slight modifications, could be incorporated into existing bottomland hardwood simulation models that do not specifically represent seedling growth and survival.

Effects of flooding regimes on two impounded bottomland hardwood stands

The relationships between flooding regimes, stand structure, regeneration, and tree stress and mortality were evaluated within two overcup oak (Quercus lyrata) — willow oak (Quercus phellos) greentree reservoirs, one impoundment with levees and one without levees. Record rainfall resulted in extensive growing-season flooding in both impoundments; however, the levee system and the topographic relief of the impoundment with levees impeded drainage of surface water and prolonged growing-season flooding. Limited regeneration of all species except overcup oak was observed in both impoundments. In the impoundment with levees, the total number of overcup oak seedlings at peak establishment and overcup oak seedling mortality were related to flooding regimes. In the impoundment without levees, establishment densities were not related to any of the measured environmental variables. Stress and mortality were significantly higher in trees in larger diameter classes, and stress generally increased with flooding. these results suggest that the decision to create GTRs within a stand of naturally flooded bottomland hardwoods should be thoroughly and cautiously reviewed.

Wood Duck and Mallard Winter Microhabitats in Mississippi Hardwood Bottomlands

Wood ducks (Aix sponsa) and mallards (Arras platyrhyrrchos) use southern hardwood bottomlands and greentree reservoirs extensively during winter, but possible differential microhabitat use by these species in forested wetlands has not been investigated. Consequently, we quantified aspects of forest structure, relative availability of potential foods (e.g,, acorns and invertebrates), and water depth at microhabitats of wood ducks and mallards in S greentree reservoirs in Mississippi during winters 1988-90 to test the null hypothesis that species'microhabitats did not differ. Species' microhabitats differed (P≤ 0.03) in 1 or both winters. Compared with wood ducks, mallards used microhabitats with greater «openness» (i.e., less canopy closure, tree density, and understory cover), lower tree species diversity, and shallower water

Water relationships among wetland habitat types in the Mingo Swamp, Missouri

The hydrologic relationships of 15 lowland hardwood wetland habitat types in the Mingo Swamp of southeastern Missouri were analyzed using principal component analysis (PCA) and clustering multivariate techniques. Both the PCA and cluster analyses defined significant differences among wetland types. In all PCAs, the percentage of total water coverage, percentage of water 30 cm deep had the highest loading in factor I and were most useful in separating wetland types. Typically, open water habitats were classified at one extreme in the analyses and pin oak/hickory habitats at the opposite extreme. Dead tree, open marsh, ditch, and river habitats were usually closely grouped; however, all green-tree reservoir habitats were hydrologically shifted toward deeper, more permanently flooded conditions, especially in fall and early winter.

Plant and water-level dynamics in an east texas shrub/hardwood bottomland wetland

Plant distribution and layering were analyzed from four line transects across aninehectare shrub swamp and adjacent hardwood bottomlands, and water fluctuations and hydroperiod were assessed via six wells and staff gauges. Vegetational transition from deep to shallow water was buttonbushCephalanthus occidentalis, water elmPlanera aquatica, overcup oakQuercus lyrata, water oakQ. nigra, willow oakQ. phellos, and several other hardwoods intermixed at less frequently flooded elevations. A past die-off of overcup oak and other vegetational changes suggest that a single event or a series flooding events occurred during the growing season. Vegetative change included rapid establishment of herbaceous vegetation in shallow, open are as after overstory die-off, followed by gradual invasion of water elm. Further opening in adjacent bottomland woods is resulting from windfall of shallow-rooted oaks. Impoundments for green-tree reservoirs or other water-level modifications should be based upon an understanding of local plant succession since slight changes in water regime may modify plant species or cover-water patterns and seriously impact the wetland community. Where possible, natural water regimes should be preserved; where this is impossible due to watershed modifications, such regimes should be documented and duplicated by use of the most simple possible management system to avoid endangering natural plant communities.

Breeding Bird Response to Greentree Reservoir Management

L'amenagement de ces bassins temporaires destines a attirer le gibier d'eau migrateur et a lui fournir un habitat provoque une reduction du couvert vegetal situe sous la couronne des arbres, diminuant ainsi l'approvisionnement et les opportunites de nidification des oiseaux qui utilisent le sol ou les niveaux inferieurs de la foret

Feeding Habits of Ducks in a Green-Tree Reservoir in Eastern Texas

Feeding Habits of Ducks in a Green-Tree Reservoir in Eastern Texas

Autumn Movements and Habitat Use by Wood Ducks in Southern Illinois

Movements of 961 banded wood ducks (Aix sponsa), including 10 radio-instrumented birds, were observed during the autumn of 1973 in southern Illinois. Some birds moved up to 10 km each day, but most stayed within 2.2 km of the roost. Movements usually occurred during morning and evening hours. Autumn areas of activity for wood ducks ranged from 23.9 to 186.2 ha (i = 90.6 ha). Wood ducks had a significant day and nighttime preference for buttonbush (Cephalanthus occidentalis) swamp over flooded timber and open water. In managing wood ducks, habitat types which are available should be emphasized more than area size and, when possible, management areas should be located to include traditional roosting sites. J. WILDL. MANAGE. 43(1):102-108 Band-recoveries have delineated migratory movements of wood ducks (Beshears 1967, Brown 1972) and work has been done on home range and habitat use during the breeding season (Gilmer 1971). Summer movements and habitat use by females with broods also have been investigated (Hardister et al. 1963, Webster and McGilvrey 1966, McGilvrey 1969, Ball 1971). However, much is not known about activity and habitat utilized by this species. The objective of this study was to identify the habitat requirements and movements of wood ducks during autumn so that managers might have a basis for more intensive yearround management. We thank Karen Crites, R. Hileman, F. Roetker, and V. Hammer for their assistance in the field. We thank M. Sweet for supplying information on band recoveries from Oakwood Bottoms Greentree Reservoir. W. D. Klimstra, Cooperative Wildlife Research Laboratory, Southern Illinois University, provided radiotelemetry receiving equipment. We thank J. Newcomb, District Ranger, U.S. Forest Service, for allowing access to U.S. Forest Service lands. The Max McGraw Wildlife Foundation and the Illinois Department of Conservation financed part of this study. MATERIALS AND METHODS