Longleaf Pine Communities Research Articles

The Lack of Favorable Responses of an Endangered Pitcher Plant to Habitat Restoration

Abstract Restoring habitat structure that existed before active and inadvertent fire suppression is thought to be critical to maintaining populations of some rare plants in fire‐suppressed habitats. Nevertheless, the impacts of habitat restoration on most endangered plants are poorly understood. Current theory predicts and empirical studies have shown that the reduction of shade or competition (frequently a goal of many habitat restoration projects in degraded fire‐dependent ecosystems) benefits plants adapted to nutrient‐poor soils by increasing the benefit‐to‐cost ratio of adaptations for enhanced nutrient capture. Here, I examined how experimental reduction of neighboring plants in a wet longleaf pine community dominated in the ground cover by shrubs and stump sprouts influenced the growth, the reproduction, the carnivorous effort, and the benefits of carnivory in a U.S. federally endangered species, Sarracenia rubra ssp. alabamensis. Two years of data showed no significant effects of neighbor reduction or prey exclusion on any of several indicators of plant performance, nor was there any evidence of a hypothesized morphological trade‐off between shade avoidance and prey capture. These results were unexpected. Inadequate replication and atypical precipitation patterns were ruled out as possible explanations. The population studied here (unlike that of a different, but morphologically similar, species growing in a fire‐maintained pine grass–sedge savanna) did not exhibit the ability to respond to variation in competition from neighboring plants.

Seed Bank Viability in Disturbed Longleaf Pine Sites

Abstract Some of the most species‐rich areas and highest concentrations of threatened and endangered species in the southeastern United States are found in wet savanna and flatwood longleaf pine (Pinus palustris Mill.) communities. Where intensive forestry practices have eliminated much of the natural understory of the longleaf ecosystem, the potential for reestablishment through a seed bank may present a valuable restoration opportunity. Longleaf pine sites converted to loblolly pine plantations and non‐disturbed longleaf sites on the Coastal Plain of North Carolina were examined for seed bank presence and diversity. Conducting vegetation surveys and examining the seed bank using the seedling emergence technique allowed for verification of the seed bank presence, as well as evaluation of the quality of the seed bank on disturbed longleaf pine sites. Forty‐three species and over 1,000 individuals germinated, and the seed banks of both the disturbed and non‐disturbed stand types contained species not noted in the vegetation survey. Although many of these species were considered weedy and typical of disturbance, numerous taxa were indicative of stable longleaf pine communities. This study confirms both the presence and quality of seed banks in highly disturbed former longleaf pine sites, suggesting that the seed bank may be an important tool in restoration efforts.

Nitrogen and Carbon Cycling in a Model Longleaf Pine Community as Affected by Elevated Atmospheric CO2

Increasing global atmospheric CO2 concentration has led to concerns regarding its potential effects on terrestrial ecosystem and the long-term storage of C and N in soil. This study examined responses to elevated CO2 in a typical regenerating longleaf pine-wiregrass community. The model community consisted of five plant species: (1) an evergreen conifer (Pinus palustris), (2) a bunch grass (Aristida stricta), (3) a broadleaf tree (Quercus margaretta), (4) a perennial herbaceous legume (Crotalaria rotundifolia), and (5) a herbaceous perennial (Asclepias tuberosa) grown at two CO2 concentrations (ambient and twice ambient). The CO2-enriched plots had greater aboveground biomass than ambient plots, mainly due to increased pine biomass. After 3 years, samples of the soil (Blanton loamy sand: loamy, siliceous, semiactive, thermic Grossarenic Paleudult) were collected from 0- to 5-, 5- to 10-, and 10- to 20-cm depth increments. Microbial respiration, potential C and N mineralization, and C turnover were measured during a 120-day incubation of the soil samples. Elevated CO2 decreased soil C respiration and C turnover, but increased N mineralization. Results indicate that soil C sequestration is likely for soils in this longleaf pine ecosystem.

Effects of Prescribed Burning on Amphibian Diversity in a Southeastern U.S. National Forest

Abstract: Fire alters the abundance and diversity of many species, but its effects on amphibians are poorly known. We tested whether prescribed burning affected amphibian abundance and diversity within the Francis Marion National Forest, South Carolina, by monitoring assemblages at 15 temporary ponds with five different burn histories: 0, 1, 3, 5, and 12 years after burns. We also monitored terrestrial and aquatic environmental variables likely to influence amphibian diversity, such as leaf‐litter depth, pond water chemistry, and distance to neighboring ponds. Fire had significant negative effects. Immediate effects ( burning during the study ) explained 12.8% and 10.8% of the variation in anuran and amphibian abundance, respectively, whereas short‐term effects explained 31.8% and 24.6% of variation in amphibian species richness and evenness, respectively. Species richness increased and evenness decreased with time since burn, primarily because salamanders were rarely encountered at sites burned within 2 years. These sites had the shallowest leaf litter and highest soil temperature variances. Environmental factors unrelated to burning also significantly influenced amphibian diversity. Water chemistry explained 31.1% of variation in species richness, 32.2% of evenness, and>25% of anuran, salamander, and total amphibian abundances. Salamanders were most sensitive to water chemistry factors, particularly pH. Our results suggest that decreasing the frequency of prescribed burns from the current 2–3 years to 3–7 years will better maintain diverse amphibian and plant assemblages. Substituting growing‐season burns for the current practice of winter and spring burns would avoid repeatedly interrupting amphibian breeding and would maintain the desired longleaf pine community.

INFLUENCE OF SEASON AND FREQUENCY OF FIRE ON HENSLOW'S SPARROWS (AMMODRAMUS HENSLOWII) WINTERING ON GULF COAST PITCHER PLANT BOGS

Abstract Henslow's Sparrow (Ammodramus henslowii) is a grassland bird that has suffered drastic population declines for over 30 years. Declining populations can be largely attributed to loss of breeding habitat, but loss of wintering habitat associated with longleaf pine (Pinus palustris) communities, especially pitcher plant (Sarracenia spp.) bogs, along the Gulf Coast also may be a contributing factor. Fire is critical for restoration and conservation of remaining longleaf pine communities, but the influence of fire on wintering Henslow's Sparrows has not been evaluated. We examined the influence of season and frequency (time since burning) of fire on use of pitcher plant bogs by Henslow's Sparrows wintering in the Conecuh National Forest, Alabama, and Blackwater River State Forest, Florida, during winters of 1999–2000 and 2000–2001. Density of Henslow's Sparrows was greatest on bogs the first winter after burning. Although significant effects for season of burning were not found, bogs burned during win...

Influence of Season and Frequency of Fire on Henslow's Sparrows (Ammodramus Henslowii) Wintering on Gulf Coast Pitcher Plant Bogs

Abstract Henslow's Sparrow (Ammodramus henslowii) is a grassland bird that has suffered drastic population declines for over 30 years. Declining populations can be largely attributed to loss of breeding habitat, but loss of wintering habitat associated with longleaf pine (Pinus palustris) communities, especially pitcher plant (Sarracenia spp.) bogs, along the Gulf Coast also may be a contributing factor. Fire is critical for restoration and conservation of remaining longleaf pine communities, but the influence of fire on wintering Henslow's Sparrows has not been evaluated. We examined the influence of season and frequency (time since burning) of fire on use of pitcher plant bogs by Henslow's Sparrows wintering in the Conecuh National Forest, Alabama, and Blackwater River State Forest, Florida, during winters of 1999–2000 and 2000–2001. Density of Henslow's Sparrows was greatest on bogs the first winter after burning. Although significant effects for season of burning were not found, bogs burned during winter typically hosted Henslow's Sparrows for only one winter, whereas bogs burned during the growing season hosted sparrows for at least three winters. Growing-season fires may be more beneficial than dormant-season fires and will prevent forced abandonment of bogs burned during winter. Frequency of seed stalks of grasses and density of forbs were the most influential vegetation parameters affecting occurrence of Henslow's Sparrows at pitcher plant bogs. Henslow's Sparrows were found on bogs as small as 0.06 ha, but were found on bogs >0.25 ha more frequently than on smaller bogs. We conclude that burning pitcher plant bogs on an annual or biennial basis during the growing season will maximize the benefits to both wintering Henslow's Sparrows and the host of other organisms associated with those unique communities.

Elevated atmospheric CO2 affects structure of a model regenerating longleaf pine community

AbstractDifferences in plant morphology, physiology, life form, and symbiotic relationships can generate differences in species responses to CO2‐enrichment, which can alter competitive interactions, thus affecting community structure and function. Here, we present data from a two‐year study, examining the species and community responses to elevated [CO2] of a model regenerating longleaf pine community. The model community was constructed from an assemblage of early successional forest species representing major functional guilds within a typical longleaf pine–wiregrass community: (1) a C3 evergreen conifer (Pinus palustris); (2) a C4 bunch grass (Aristida stricta); (3) a C3 broadleaf tree (Quercus margaretta); (4) a C3 perennial herbaceous legume (Crotalaria rotundifolia); and (5) a C3 herbaceous perennial (Asclepias tuberosa). After 2 years, CO2‐enriched plots had 109% greater above‐ground biomass than ambient plots, mainly due to a 117% increase in pine biomass. Community structure was altered by CO2 enrichment; Crotalaria and Asclepias had higher mortality and less biomass in high‐CO2 plots, suggesting that not all species will perform well as global [CO2] rises. Our data suggest that longleaf pine communities as a whole will perform well in a future higher CO2 world, but some species may fall prey to altered competitive interactions for light and soil moisture.

Scaling species dynamics in Pinus palustris communities: Effects of pine straw raking

Abstract In the southeastern USA, harvest of pine straw sometimes involves mechanical raking of natural Pinus palustris (longleaf pine) communities. Little is known about the effects of raking nor how these effects may vary in time and space. In a two yr experiment, we examined the effects of mechanized raking on Pinus palustris dominated communities (scrub oak, dry savanna, and mesic savanna) by monitoring vegetation at seven spatial scales (0.01-100 m2). We measured floristic similarity and the proportion of species initially present that were gained (i.e. new species) or lost during four sampling periods. Relationships between spatial scale and these community attributes were analyzed using a repeated measures approach and functional response curves. Spatial scale clearly affected observed rates of species loss and floristic similarity; losses declined and floristic similarity increased as scale increased. We relate these patterns to expanding population sizes with scale and our inability to detect spe...

Short-term effects of pine straw raking on plant species richness and composition of longleaf pine communities

Pine straw is commonly used as landscaping material throughout the southeastern USA, but little is known regarding the effects of raking and removal of straw in natural longleaf pine ( Pinus palustris) communities. In a 2–year experiment, we tested the effects of community type (scrub oak, dry savanna, and mesic savanna) and number of mechanized rakings (0–4 times over a 2-year period) on species richness and floristic composition of vascular plants at spatial scales of 1 and 100 m 2. Multiple rakings caused richness to decline in the scrub oak community (1 m 2) and to increase in the more heavily-vegetated mesic savanna (1 and 100 m 2). Changes in richness were not proportional to the number of rakings, perhaps because (1) vegetation injury was minimal, (2) regrowth was possible owing to a largely perennial flora, and (3) the first litter removal removed the greatest amount of vegetation. In the mesic savanna, the only significant decline in richness, relative to initial values, occurred immediately after the first raking. Some seasonal variations were observed in species richness and in the quantity of vegetation removed by raking. Although raking may selectively injure shrubs and wiregrass, raking did not allow the introduction of non-native plants and generally had little effect on floristic composition.