Pond Pine Research Articles

Millennial-Scale Carbon Storage in Natural Pine Forests of the North Carolina Lower Coastal Plain: Effects of Artificial Drainage in a Time of Rapid Sea Level Rise

Coastal forested wetlands provide important ecosystem services along the southeastern region of the United States, but are threatened by anthropogenic and natural disturbances. Here, we examined the species composition, mortality, aboveground biomass, and carbon content of vegetation and soils in natural pine forests of the lower coastal plain in eastern North Carolina, USA. We compared a forest clearly in decline (termed “ghost forest”) adjacent to a roadside canal that had been installed as drainage for a road next to an adjacent forest subject to “natural” hydrology, unaltered by human modification (termed “healthy forest”). We also assessed how soil organic carbon (SOC) accumulation changed over time using 14C radiocarbon dating of wood sampled at different depths within the peat profile. Our results showed that the ghost forest had a higher tree density at 687 trees ha−1, and was dominated by swamp bays (Persea palustric), compared to the healthy forest, which had 265 trees ha−1 dominated by pond pine (Pinus serotina Michx). Overstory tree mortality of the ghost forest was nearly ten times greater than the healthy forest (p < 0.05), which actually contributed to higher total aboveground biomass (55.9 ± 12.6 Mg C ha−1 vs. 27.9 ± 8.7 Mg ha−1 in healthy forest), as the dead standing tree biomass (snags) added to that of an encroaching woody shrub layer during ecosystem transition. Therefore, the total aboveground C content of the ghost forest, 33.98 ± 14.8 Mg C ha−1, was higher than the healthy forest, 24.7 ± 5.2 Mg C ha−1 (p < 0.05). The total SOC stock down to a 2.3 m depth in the ghost forest was 824.1 ± 46.2 Mg C ha−1, while that of the healthy forest was 749.0 ± 170.5 Mg C ha−1 (p > 0.05). Carbon dating of organic sediments indicated that, as the sample age approaches modern times (surface layer year 2015), the organic soil accumulation rate (1.11 to 1.13 mm year−1) is unable to keep pace with the estimated rate of recent sea level rise (2.1 to 2.4 mm year−1), suggesting a causative relationship with the ecosystem transition occurring at the site. Increasing hydrologic stress over recent decades appears to have been a major driver of ecosystem transition, that is, ghost forest formation and woody shrub encroachment, as indicated by the far higher overstory tree mortality adjacent to the drainage ditch, which allows the inland propagation of hydrologic/salinity forcing due to SLR and extreme storms. Our study documents C accumulation in a coastal wetland over the past two millennia, which is now threatened due to the recent increase in the rate of SLR exceeding the natural peat accumulation rate, causing an ecosystem transition with unknown consequences for the stored C; however, much of it will eventually be returned to the atmosphere. More studies are needed to determine the causes and consequences of coastal ecosystem transition to inform the modeling of future coastal wetland responses to environmental change and the estimation of regional terrestrial C stocks and flux.

Aggregations of Polistes Wasps Over-Wintering in Artificial Red-Cockaded Woodpecker Cavities

We document blockage of artificial Dryobates borealis (Red-cockaded Woodpecker) cavities by family Sphecidae (mud daubers) and large mixed-species aggregations of wintering Polistes (paper wasps) in cavity inserts at Great Dismal Swamp NWR in southeast Virginia. The large aggregations that we encountered are the only known cases of more than 2 paper wasp species cohabitating. Activity of Red-cockaded Woodpeckers within a cluster lessened the likelihood that paper wasps will aggregate in cavities, but not the likelihood that mud daubers will nest in cavities. The moist and saturated soils that predominate our field site may explain why these insects are more abundant compared to drier, upland habitats. Additionally, removal of hardwood trees may increase the breeding season habitat quality for paper wasps that hunt and nest in areas that are more open, while simultaneously limiting potential winter hibernacula habitat, typically found in mature hardwood tree cavities for Red-cockaded Woodpeckers. Common cavity management and translocation techniques may need to be altered to mitigate greater paper wasp and mud dauber activity at Red-cockaded Woodpecker cavity inserts in Pinus serotina (Pond Pine) pocosin habitat. We suggest using graduated rubber stoppers rather than screens that fail to exclude insect taxa or conducting translocations prior to the formation of winter aggregations of paper wasps.

Monitoring soil carbon flux with in-situ measurements and satellite observations in a forested region

Carbon dioxide (CO2) flux plays a key role in the energy balance of ecosystems and effective monitor CO2 flux from soil at both large scale and high temporal resolution remains a critical scientific problem of soil science. To address this scientific problem, this study tested a novel model to estimate CO2 flux from soil with highly dense vegetation cover. In contrast to previous approaches, the developed model monitored daily CO2 flux at both high spatial and temporal resolutions. This model is applicable for different forest types by fusing the daily TERRA Moderate Resolution Imaging Spectroradiometer (MODIS), Land Remote Sensing Satellite (Landsat) measurements, and monthly in-situ CO2 flux measurements collected by non-permanent chambers in the Great Dismal Swamp (GDS), the U.S. Then, daily vegetation index and surface soil temperature were estimated at high spatial resolution, and the CO2 flux was retrieved through a semi-empirical model. Two-year ground observations in the GDS were used to train and validate the model. Over the GDS area, the validation results of the retrieved CO2 flux had a coefficient of determination (R2) of 0.47, and a root mean square error (RMSE) of 1.25e + 05 μg CO2/m2/h. Further analysis showed that the performance of the proposed method varied slightly with forest types. The difference between R2 was less than 0.07 and the difference between RMSE was less than 0.08e + 05 μg CO2/m2/h. The GDS has three main forest types: maple gum (Acer rubrum and Nyssa sylvatica), Atlantic white cedar (Chamaecyparis thyoides), and pine pocosin (Pinus serotina). For the maple-gum, the R2 was 0.51, and the RMSE was 1.14e + 05 μg CO2/m2/h. For Atlantic white cedar, the R2 was 0.62, and the RMSE was 1.15e + 05 μg CO2/m2/h. For pine pocosin, the R2 was 0.44, and the RMSE was 1.07e + 05 μg CO2/m2/h. The proposed method enables estimation of CO2 flux within forested areas, and forest type affects the monitoring results.

Restoration of Fire-Climax Species within a Rare Longleaf Pine Forest in the Piedmont of North Carolina

ABSTRACT: The US Fish and Wildlife Service has engaged conservation partners to assist in assessing current conditions and needs to retain and restore one of the South's rarest pine ecosystems. The “wet-piedmont longleaf pine forest” is characterized by the presence of longleaf, loblolly, and pond pines in association with facultative-wetland species. This longleaf forest type is assigned the rarest ranking by NatureServe and the North Carolina Natural Heritage Program (G1S1). A remnant of that ecosystem type exists on the Pee Dee National Wildlife Refuge in Wadesboro, North Carolina, where overstory species include longleaf and pond pine in association with the commonly represented loblolly pine. In addition, shortleaf pine and a variety of hardwood species are present. Initial restoration actions have focused on (1) reducing the understory presence of sweetgum; (2) introducing variable density retention of loblolly pine within a mixture of longleaf, pond, and shortleaf pines; and (3) application of pres...

Patterns of vegetation composition and diversity in pine-dominated ecosystems of the Outer Coastal Plain of North Carolina: Implications for ecosystem restoration

Terrestrial ecosystems of the Atlantic coastal plain have experienced considerable change over the past two centuries, largely due to agricultural activities and fire suppression and exclusion. Many areas that were once dominated by open longleaf pine (Pinus palustris) woodlands now support closed canopy stands of loblolly pine (Pinus taeda) with a dense midstory of broadleaved shrubs and trees. In recent years, efforts to restore the herbaceous plant communities typically found in fire-maintained longleaf pine woodlands have focused on the use of midstory thinning to produce savanna-like conditions and to facilitate the restoration of historical fire regimes through prescribed burning. Previous efforts to restore longleaf pine stands have focused on the potential of fire-suppressed longleaf pine woodlands, which have been met with some success. However, it is unclear what the potential is for loblolly pine stands to act as a ’surrogate’ environment for the restoration of the often species-rich herbaceous layer of longleaf pine woodlands. To assess the effectiveness of longleaf pine restoration treatments in existing loblolly pine stands, we analyzed the drivers of plant community composition in loblolly pine stands with mechanical midstory removal treatments, untreated loblolly pine stands, longleaf pine stands, and pond pine dominated high-pocosin systems. We sampled 75 plots, from which more than 200 individual plant taxa were identified, with species richness (number of species per 0.1ha) ranging from 9 in pond pine pocosins to 118 in longleaf pine woodlands. Plant species richness and composition varied in response to soil properties, with the first NMS ordination axis correlated with soil properties related to soil moisture and organic matter content (SOM), and the second NMS ordination axis correlated to the concentration of certain soil nutrients (P, Ca), the variability of which may be due, in part, to historic fertilizer applications. While stand types were largely distinct from each other in their vegetation composition, there was nevertheless some compositional overlap among some longleaf and loblolly pine stands. Areas of compositional overlap appear to have somewhat similar soil properties, whereby the soils found in overlapping loblolly pine stands were closer to those found in longleaf pine stands (i.e. low SOM content). Thus, an assessment of the soil properties of loblolly pine stands may allow for an identification of candidate sites for which longleaf pine restoration treatments may be most effective.

Historical and current landscape‐scale ponderosa pine and mixed conifer forest structure in the Southern Sierra Nevada

Many managers today are tasked with restoring forests to mitigate the potential for uncharacteristically severe fire. One challenge to this mandate is the lack of large‐scale reference information on forest structure prior to impacts from Euro‐American settlement. We used a robust 1911 historical dataset that covers a large geographic extent (>10,000 ha) and has unbiased sampling locations to compare past and current forest conditions for ponderosa pine and mixed conifer forests in the southern Sierra Nevada. The 1911 dataset contained records from 18,052 trees in 378 sampled transects, totaling just over 300 ha in transect area. Forest structure was highly variable in 1911 and shrubs were found in 54% of transects. Total tree basal area ranged from 1 to 60 m2 ha−1 and tree density from 2 to 170 ha−1 (based on trees >30 cm dbh). K‐means cluster analysis divided transects into four groups: mixed conifer‐high basal area (MC High BA), mixed conifer‐average basal area (MC Ave BA), mixed conifer‐average basal area‐high shrubs (MC Ave BA Shrubs), and ponderosa pine (Pond Pine). The percentage of this 1911 landscape that experienced high severity fire was low and varied from 1–3% in mixed conifer forests and 4–6% in ponderosa pine forests. Comparing forest inventory data from 1911 to the present indicates that current forests have changed drastically, particularly in tree density, canopy cover, the density of large trees, dominance of white fir in mixed conifer forests, and the similarity of tree basal area in contemporary ponderosa pine and mixed conifer forests. Average forest canopy cover increased from 25–49% in mixed conifer forests, and from 12–49% in ponderosa pine forests from 1911 to the present; canopy cover in current forest types is similar but in 1911 mixed conifer forests had twice the canopy cover as ponderosa pine forests. Current forest restoration goals in the southern Sierra Nevada are often skewed toward the higher range of these historical values, which will limit the effectiveness of these treatments if the objective is to produce resilient forest ecosystems into the future.

Annual growth in longleaf (Pinus palustris) and pond pine (P. serotina) in the Sandhills of North Carolina is driven by interactions between fire and climate

Understory fires are important for the maintenance of pine savanna ecosystems of the southeastern U.S., which contain high biodiversity and numerous federally endangered species. Prescribed burns are administered to maintain the open structure of pine savannas, conserve biodiversity, and to reduce wildfire hazard. However, relatively little research has examined which factors control the effects of prescribed burns on mature trees, and how responses might be altered by changing climate. The impact of prescribed burning on growth responses is likely to vary by tree species and by environmental conditions. To test the importance of these factors, tree cores were taken from mature Pinus palustris and Pinus serotina individuals at multiple locations across Fort Bragg, NC, a military preserve with detailed records on prescribed burn history dating back to 1991. Individual trees were sampled along the hydrologic gradient from xeric uplands to streamside wetlands. Annual growth was modeled as a function of species identity, hydrologic position, fire history, and climate conditions. We determined that prescribed burning produced a moderate decline in annual growth indicating that stress from prescribed burns outweighs benefits from increased water and nutrient availability. We found that the negative effects from prescribed burning were diminished or reversed during warmer years, and that the model predicts potential increases in growth during burn years under anticipated climate change scenarios. Surprisingly, there were no significant differences in growth rate by species or hydrologic position. Together these findings suggest that while prescribed burns may have minor, short-term impacts on tree growth under most current conditions, these effects are small enough that they are unlikely to outweigh the many benefits of this management technique for other aspects of ecosystem structure.

Evaluating responses of four wetland plant species to different hydroperiods.

Previous work has estimated the hydroperiod requirements (saturation duration and frequency) of wetland plant communities by modeling their hydrologic regimes in natural (never drained) wetlands for a 40-yr period. This study tested the modeled predictions in a controlled greenhouse study using tree species representing three of the plant communities plus an additional species from another community. Bald cypress ( L. Rich.), sweet bay ( L.), pond pine ( Michx.), and swamp chestnut oak ( Nutt.) were grown under three hydroperiods (continuously ponded for 100 d, intermittently ponded for 14 d, and unsaturated) in loamy sand and sapric (organic) materials. Bald cypress (representing a Nonriverine Swamp Forest community) adapted well to 100 d of ponding by producing lateral roots near the soil surface and aerenchyma tissue in roots and stem. Sweet bay (Bay Forest community) also adapted well to 100 d of ponding by producing adventitious roots on the submerged portion of the stem. Pond pine (Pond Pine Woodland) and swamp chestnut oak (Nonriverine Wet Hardwood Forest) were intolerant of 100 d of ponded conditions. Seventy-five percent of the pond pine seedlings and 87% of the swamp chestnut oak seedlings died in the continuously ponded treatment level, whereas 100% of the bald cypress and 88% of the sweet bay seedlings survived. Results from this study suggest that modeled long-term hydroperiods of natural wetland plant communities can be used for restoration of these communities.

Changing eastern broadleaf, southern mixed, and northern mixed forest ecosystems of the eastern United States

Recognition of changes in forests provides greater perspective about current trajectories of forests. I compared the newest USDA Forest Service Forest Inventory and Analysis (FIA) surveys to the oldest available surveys in the eastern United States to detect increasing and decreasing species and groups over large spatial extents. Species appeared to be increasing at the expense of decreasing species within each of the major forest ecosystems of the eastern United States. In eastern broadleaf forests, oaks and Virginia pine are decreasing and maples and eastern redcedar are increasing. In southern mixed forests, planted loblolly and slash pine are replacing shortleaf and longleaf pines, and longleaf pine wetland associates of swamp tupelo, pond cypress, and pond pine. In northern mixed forests of the Great Lake states, quaking aspen and paper birch are decreasing whereas red pine, later successional black spruce and northern white-cedar, and maples of eastern broadleaf forests are increasing. Indeed, red maple now is more frequent than aspen in northern mixed forests. The historical legacy of fire continues to affect forest composition. Without fire, fire-tolerant oaks and pines (that are not planted) still are decreasing, whereas fire-sensitive tree species are increasing. Forestry practices benefit planted pines but are not as effective at supporting quaking aspen against competition from red maple and species of the eastern broadleaf forest as in the past.

Linking Plant Ecology and Long-Term Hydrology to Improve Wetland Restoration Success

Although millions of dollars are spent restoring wetlands, failures are common, in part because the planted vegetation cannot survive in the restored hydrology. Wetland restoration would be more successful if the hydrologic requirements of wetland plant communities were known so that the most appropriate plants could be selected for the range of projected hydrology at the site. Here we describe how hydrologic models can be used to characterize the long-term hydrology of wetland plant communities, and we show how these results can be used to define wetland design criteria. In our study, we quantified differences in long-term (40-year) hydrologic characteristics of the pond pine woodland (PPW), nonriverine swamp forest (NRSF), high pocosin (HP), and bay forest (BF) plant communities native to the North Carolina Coastal Plain. We found that the median water level was 8 cm below the land surface in PPW and 9, 2, and 8 cm above the land surface for NRSF, HP, and BF, respectively. When the land surface was inundated, the median duration of inundation was 91 d year-1 for PPW and 317, 243, and 307 d year-1 for NRSF, HP, and BF, respectively. Our models suggested that the PPW received an average of 15% of its water input from groundwater inflow, whereas the other communities we modeled did not appear to receive groundwater inflow. Using these results and soil organic layer thickness, we developed and propose design criteria linking soil, vegetation, and hydrology parameters that should contribute to improved restoration success.

Plant-Soil-Hydrology Relationships in Three Carolina Bays in Bladen County, North Carolina

Abstract This study provides quantitative ecological targets for restoring degraded peat-based Carolina Bays in the Carolina Flatwoods Ecoregion. Cluster analysis of vegetation data from three Carolina Bay reference sites in Bladen County, North Carolina, indicated four plant communities present: pond pine (Pinus serotina) woodland, non-riverine swamp forest dominated by swamp gum (Nyssa biflora), high pocosin dominated by evergreen shrubs with scattered pond pine, and bay forest dominated by loblolly bay (Gordonia lasianthus). We classified bay soils according to surface organic layer thickness (OLT) into mineral, histic, shallow organic, and deep organic types. We monitored the water table of each soil type in one bay throughout one growing season. The soil types with corresponding water table regimes were: mineral (9.4 cm mean OLT with a rooting zone water table [RZWT] 39% of the monitoring period), histic (27.5 cm OLT and 76% RZWT), shallow organic (63.9 cm OLT and 84% RZWT), and deep organic (102.5 c...

Measuring species diversity to determine land-use effects on reptile and amphibian assemblages

AbstractPopulations of herpetofauna are declining globally primarily due to land-use practices (e.g., silviculture or conversion to agriculture) and declines require monitoring of all herpetofauna communities. Therefore, forest management plans for Bull Neck Swamp, a pocosin wetland in North Carolina, USA, initiated an inventory of the herpetofauna community. Our objectives were to: (1) derive diversity measures for four designated habitat preserves (i.e., Atlantic whitecedar [Chamaecyparis thyoides], Pond pine [Pinus serotina], Non-riverine Swamp, and Shoreline/Islands) and a Forest manageable area, (2) determine if there were benefits to habitat preserves for the herpetofauna community, and (3) provide recommendations for future monitoring. We employed 11 different sampling techniques across the four habitat preserves and Forest manageable area. Species richness estimates and similarity indices were derived using EstimateS 8.0. For post hoc comparisons, we derived species distributions with the Nestedness Temperature Calculator Program. Observed species richness ranged from 7 to 32 species (S = 13 to 44) and abundances ranged from 99 to 873 individuals. Similarity indices suggested species compositions were similar among habitats. Further, nestedness temperature (T = 12.6°C) indicated an even species distribution among assemblages. Comparable similarity indices among habitats, an even species distribution, and habitat continuity suggested management practices would have little impact on the herpetofauna community. Nevertheless, future management practices should be carefully considered and planned to mitigate effects to individual species. We recommend studies employ species richness, relative abundance, species composition, and distribution as conservation tools when inventorying or monitoring herpetofauna communities.

Seed bank response to wet heat and the vegetation structure of a Virginia pocosin1

Pocosins are shrub wetlands of the southeastern coastal plain maintained by fire. Increased herbaceous plant diversity has been reported after wildfire. To test the effect of radiant heating on the seed bank of pocosin-upland ecotones, wet heat treatments were applied to Sphagnum substrate from a Virginia small depression pocosin. The seedling emergence method was used to quantify wetland seedling abundance and richness. Extant vegetation was measured at each seed bank sampling area and the seed bank and vegetation were compared with Sorenson similarity values. No significant seedling abundance, richness, or evenness effects were detected among wet heat and control groups. However, the high wet heat treatment (75 °C) significantly reduced the density of Sphagnum cuspidatum capitula more than 80% relative to the control. Mean seed bank density was 6,209 seedlings/m2 (richness = 11) and was dominated by Scirpus cyperinus (97.8%), contained many early successional species. The seed bank did not closely resemble the extant vegetation. Pocosin canopy was sparse and dominated by Pinus serotina. The shrub-sapling stratum indicated co-dominance of Acer rubrum and ericaceous species, potentially indicating a shift from a shrub bog to a wet pine-hardwood community.

Factors affecting sustained smouldering in organic soils from pocosin and pond pine woodland wetlands

The smouldering combustion of peat and muck soil plays an important role in the creation and maintenance of wetland communities. This experimental study was conducted to improve our understanding of how moisture and mineral content constrain smouldering in organic soil. Laboratory burning was conducted with root mat and muck soil samples from pocosin and pond pine woodland wetlands common on the North Carolina coastal plain. The results of laboratory and prescribed burning were compared. Laboratory results showed that moisture and mineral content influenced sustained smouldering in root mat soils. Predictions based on logistic regression analysis show that root mat soils with an average mineral content of 4.5% had an estimated 50% probability of sustained smouldering at a moisture content of 93%, whereas at moisture contents above 145% the estimated probability was less than 10%. The odds that root mat soil will sustain smouldering decrease by 19.3% for each 5% increase in moisture content. Root mat soils with an average mineral content of 5.5% and a moisture content of 93% had an estimated 61% probability of sustained smouldering. The odds that root mat soil will sustain smouldering combustion increased by 155.9% with each 1% increase in mineral content. Root mat and muck soils differ in physical and chemical characteristics expected to influence smouldering behaviour. The formation of muck soil has led to increases in density, smaller soil particle size, changes in water holding characteristics and increases in waxes, resins and bituminous compounds. Muck soil smouldered at higher moisture contents than root mat soil. Muck soil at a moisture content of 201% had an estimated 50% probability of sustained smouldering, whereas at moisture contents above 260% the estimated probability was less than 10%. The odds that muck soil will sustain smouldering combustion decrease by 17.2% with each 5% increase in moisture content. Ground fire in the prescribed burns stopped its vertical spread in organic soils at moisture contents consistent with logistic regression predictions developed from our laboratory results.

Flora and Soils of Wells Savannah, an Example of a Unique Savanna Type

Wells Savannah is a unique wet pine savanna located in the Lower Coastal Plain of North Carolina. It consists of two utility rights-of-way and a fire-suppressed pond pine (Pinus serotina) woodland. The objectives of this study of Wells Savannah were to characterize its soils, inventory its vascular flora, and compare its soils and flora with those of reference sites. Soil drainage, texture, and redoximorphic features were described at all locations. Wetland indices were calculated to represent the degree to which the plant communities were adapted to wet substrates. We identified 209 species in 107 genera and 48 families at Wells Savannah. Eight community associations were recognized. Wetland indices for Wells Savannah were significantly lower than those for the reference savannas. The unique combination of fine textured, very wet soil and plant species composition present at Wells Savannah has not been identified in previous studies of savannas in the region.

Paleoecology of Mid-Wisconsinan Peat Clasts from Skidaway Island, Georgia

Twelve peat clasts were recovered from a paleochannel deposit on Skidaway Island, Chatham County, Georgia. An AMS radiocarbon date from a plant stem in one of these clasts indicates original peat deposition 36,830 ± 340 14C years B.P., and the stratigraphic position of the clasts supports this age assignment. Fossil Pinus needles, pollen, and testate amoebae provide a snapshot of the environment and biota at a time when most other sites in coastal Georgia were not accumulating sediment. Pollen from the peat clasts is dominated by Pinus and other genera common on the coastal plain today (e.g., Quercus , Carya ). Morphological and anatomical analyses of the fossil Pinus needles indicate they are either Pinus taeda or Pinus serotina , which both currently inhabit the Coastal Plain of Georgia. Seven testate amoeba taxa, all characteristic of relatively dry peatland conditions, were encountered in the clasts. Testate amoeba assemblages are dominated by Hyalosphenia subflava , a taxon that is not typically dominant in modern assemblages. More investigations describing the occurrence and distribution of Quaternary testate amoebae, as well as modern ecology and biogeography of testate amoebae, are necessary before the significance of these assemblages can be assessed fully. Deposition of the peat clasts occurred at a time when pollen evidence from Florida indicates warm and wet climatic conditions, and the paleoecology of the peat clasts indicates that a relatively warm climate also existed in coastal Georgia.

Plant Population Dynamics in Response to Fire in Longleaf Pine-Turkey Oak Barrens and Adjacent Wetter Communities in Southeast Virginia

PLOCHER, A. E. (Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529). Plant population dynamics in response to fire in longleaf pine-turkey oak barrens and adjacent wetter communities in southeast Virginia. J. Torrey Bot. Soc. 126:213-225. 1999.-Permanent plots in the Zuni Pine Barrens (Isle of Wight County, Virginia) were sampled for four years to quantify population dynamics and dominance shifts in response to fire and to compare these effects among different moisture regimes. Fire caused an average 38% aboveground mortality in the overstory, 84% in the sapling/large shrub layer and nearly 100% in the understory, followed by a 3 to 11 fold increase in understory density. Regeneration in this study was predominantly by vegetative means, shrub species accounted for 90% of the postfire density and 80% of the increase in density. In the xeric barrens, Pinus palustris gained dominance of the overstory and sapling layer at the expense of Quercus laevis. In the subxeric barrens Pinus serotina remained dominant throughout the study. The same overstory species (P. serotinaiP. taeda, Acer rubrumiP. serotina) remained dominant throughout the study in wetter forests, but sapling layer pines were eliminated from the sample in the majority of these stands. In both barrens sites, the same species dominated the understory before and after the fire, and these species increased in number significantly more than others. Increases occurred only in the first year after fire. In wetter areas, most prefire dominant understory species were no longer important components of the communities after the fire, and several of these species decreased in number. Most postfire understory dominants were previously inconspicuous or absent from the wetter communities and these species increased significantly more than others. Increases in density in wetter areas occurred in both the first and second year after fire. These areas also had greater increases in species richness. Following fire, the Zuni Pine Barrens overstory was similar to those of southeastern pine barrens, while the understory closely resembled those of New Jersey pine barrens.

Phosphorus compartmentation in Pinus serotina Michx. (pond pine); observations from in vivo nuclear magnetic resonance spectroscopy

31P nuclear magnetic resonance (NMR) spectroscopy was used to estimate the amount of inorganic phosphate (Pi) present in the cytoplasm and vacuole of root tips and subapical root segments of pond pine (Pinus serotina Michx.). In root tips of seedlings grown with 100 mmol m–3P (HP) the cytoplasmic Pi content, on a root volume basis, was ≈ 1·5 μmol cm–3 and the vacuolar Pi content, on a root volume basis, was ≈ 3·4 μmol cm–3. In root tips from Pi starved seedlings the cytoplasmic Pi content, on a root volume basis, was ≈ 0·75 μmol cm–3; vacuolar Pi was too low to be reliably estimated. Similar results were obtained with subapical root segments; the Pi concentration in the cytoplasm was maintained at around 2 mol m–3 while that in the vacuole varied with Pi supply. This work demonstrates for the first time that quantitative measurements of the subcellular compartmentation of Pi can be made in young tissues of a woody species. The results indicate that cytoplasmic Pi levels are maintained across a range of external Pi supplies probably by withdrawing Pi stored in the vacuole.

Characterization of phosphorus uptake in slow- and fast-growing southern pine seedlings grown in solution culture

The effects of low-P growth conditions on growth and net P acquisition were examined in two species of pine that are indigenous to P-deficient soils of the Atlantic Coastal Plain: pond pine (Pinus serotina Michx.), a moderately-fast growing pine, and a slow-growing seed source of loblolly pine P. taeda L.) from Texas. Short-term 32P uptake experiments were conducted using intact nonmycorrhizal seedlings that had been grown for 7 weeks in continuously-flowing solution culture at 5 or 100 µM P. Growth and P uptake of pond pine were more responsive to a higher P supply than the slow-growing loblolly pine. Pond pine seedlings in the 100 µM P treatment were twice the size of those grown in 5 µM P and accumulated almost five times as much seedling P. In contrast, seedling biomass of loblolly pine increased by only 8% under high-P growth conditions, and seedlings accumulated twice as much P, reflecting the higher P concentrations in shoot and root tissues. Although rates of unidirectional influx of 32P were 22 and 61% higher under low-P growth conditions in pond and loblolly pine, respectively, net uptake rates in seedlings from the 5 µM P treatment were over three times those of seedlings grown in 100 µM P. These results suggest that unidirectional efflux out of the root was controlling net uptake of P as much, if not more, than unidirectional influx. Efflux of32 P out of root tissue, particularly older tissue, decreased in seedlings grown under low-P conditions, possibly due to a reduction in the size of the phosphorus pool available for efflux, i.e. the soluble Pi pool. Over 75% of the total root P in both loblolly and pond pine seedlings grown in 100 µM P treatment was present as organic P, suggesting that organic P, particularly phytate, may represent important storage pools in roots of woody species. Within each species, higher rates of influx and net uptake in seedlings from the low-P treatment were associated with lower P concentrations in shoot and root tissue, and shoot FW:root FW ratios. Efflux may represent a short-term means of regulating net P uptake, while the “demand” for P created by growth and storage may represent a long-term regulation.

Responses of Wetland Tree Species to Hydrology and Soils

AbstractWe conducted a study of the flood tolerance of nine wetland tree species on seven soil types. Seedlings were subjected to 11 months of continuous shallow inundation or moist soil conditions on three mineral soils, two organic soils, a manufactured soil designed to mimic the practice of layering muck over mineral soil, and a stockpiled topsoil. Taxodium ascendens, T. distichum, Acer rubrum, and Pinus serotina suffered no mortality; Fraxinus carolininna (1%), Liquidambar styraciflua (8%), P. elliottii (8%), and Gordonia lasianthus (24%) suffered low to moderate mortality; and Persea palustris (46%) suffered significant mortality. In general, greatest net height and total biomass were achieved on moist organic soils, and least net height and total biomass were achieved on stockpiled topsoil and inundated soils. Responses to hydrological conditions were less pronounced for Taxodium spp. If the results of this experiment are transferable to the field, then Acer rubrum, Fraxinus caroliniana, Pinus serotina, Taxodium ascendens, and Taxodium distichum seedlings can reasonably be expected to survive at least one year under a broad range of hydrological and edaphic conditions. With the exception of Taxodium spp., first‐year growth for the species of this study can be facilitated by maintaining moist but not inundated conditions. These findings suggest that transfer of organic soils will benefit restoration and creation efforts, and that layering organic soil over mineral soil is more effective than using mineral soils or stockpiled topsoil.