Pine Barrens Research Articles

The Biology of Corema conradii: Natural History, Reproduction, and Observations of a Post-fire Seedling Recruitment

Corema conradii (broom-crowberry, Ericaceae) is a rare dioecious shrub that reaches the southern extent of its range in New Jersey. A hot fire burned through one of the most extensive New Jersey populations of this state-endangered species during the summer of 2001, resulting in mortality of nearly all plants in the burned areas. Significant seedling recruitment occurred in the fall of 2002, followed by an even greater seedling emergence the following year. Fire is known to be an important stimulus for seed germination in this species, and fire events are an important component of the life cycle. We report data on seedling emergence as well as present ecological and biological observations of Corema conradii in the unusual coremal habitat of the New Jersey Pine Barrens, and suggest a life cycle model for this understudied species.

Ice storm impact and management implications for jack pine and pitch pine stands in New York, USA

In January 1998, an ice storm caused severe damage to the rare jack pine – pitch pine barrens in northeastern New York. We quantified tree damage and recovery in seven barrens stands and an adjacent red pine stand. Ice storm damage was variable among stands with 44% to 94% of trees exhibiting damage. Live tree basal area (BA) was reduced by 9% to 45% in six of the eight stands, and dead tree BA increased in all stands. In mixed jack pine – pitch pine stands, the percent of jack pines dead after the ice storm (71% to 91%) was much higher than red maple (0% to 7%) or pitch pine (17% to 25%).Mortality of pitch pine was very low due largely to its ability to produce epicormic growth. Red pine exhibited more severe damage than eastern white pine. Because pine regeneration remains absent or sparse in the barrens stands, deciduous trees and ericaceous shrubs may eventually replace pine species. Mortality due to ice damage may exacerbate this problem in the absence of some regenerating disturbance, such as fire or harvesting. Key words: ice storm damage, pine barrens, Pinus banksiana, jack pine, Pinus rigida, pitch pine, Pinus resinosa, red pine, Pinus strobus, eastern white pine, Acer rubrum, red maple

Plant Architecture and Leaf Damage in Bear Oak II: Insect Usage Patterns

Abstract Bear oak bushes (Quercus ilicifolia) have an inside-outside architecture where there is a set of leaves partially or completely concealed within the bush by an exterior set of leaves. We examine the impact of this architecture on microhabitat differences that are important to insect herbivores. Furthermore, we document the patterns of usage by plant-feeding insects on the inside and outside of the bush in different areas of the pine barrens of Long Island, NY. We show that there is more leaf-chewing damage and more galls of the Cynipid wasp, Amphibilops ilicifolia, on the outside of the plant. This inside-outside pattern for leaf-chewing damage is consistent across different sites, though the degree of difference between the inside and outside varies by location. We suggest that the observed herbivory pattern may be generated by differential larval performance on the inside vs. the outside leaves, differential ovipositional choice between the inside vs. the outside of the bush, or both.

The effect of mixing ground leaf litters to soil on the development of pitch pine ectomycorrhizal and soil arthropod communities in natural soil microcosm systems

The addition of leaf litter to soil influences both the nutrients and polyphenols of soil. It is likely that contrasting nutrient and polyphenolic composition of different plant litters may affect plant growth, mycorrhizal and soil arthropod communities. We report results from a microcosm experiment of effects of incorporation of three single leaf litter species and a mixture of all three on pitch pine seedling growth, their ectomycorrhizal community and soil arthropod community. The three litter species (pine, oak and huckleberry) represent co-dominant species within the New Jersey pine barrens ecosystem. We show that the leaf litters have different composition of nutrients and polyphenols, with rooting matrix containing pine litter having lower inorganic nitrogen content (1.6 μg g −1) than oak (19.9 μg g −1) and huckleberry (4.4 μg g −1), but oak litter having the highest extractable phosphorus (13.3 cf. 0–0.08 μg g −1) and total phenol content and lowest condensed tannin content. These differences were imparted to rooting matrix of homogenized humic (Oa) layer of pine barrens soil to which milled leaf litter was added and used in the microcosms. Pitch pine seedlings grew significantly better in un-amended rooting matrix (0.33±0.02 g) than any of the litter treatments (0.15±0.02–0.17±0.01 g) and tissue P concentrations tracked phosphate concentrations in the rooting matrix. Total P accumulation into plant tissue was higher in oak than control, attributable to a significantly higher ( P<0.05) accumulation in roots (3.3±0.19 mg g −1) compared to other species (1.1±0.04–2.3±0.08 mg g −1). No relationship was seen between tissue N concentration and soil N, but seedlings growing in huckleberry litter amended soil accumulated less N than control. The effect of leaf litters on the ectomycorrhizal community composition were determined by PCA (first two axes accounted for 81% of the variance) and stepwise multiple regression analysis. These analyses showed that huckleberry leaf litter had a significant impact on mycorrhizal community composition with morphotypes Cg and DB being more abundant in the presence of huckleberry litter (178±13 cf. 68±15–106±15 for Cg and 141±11 cf. 88±23–111±18 for DB) and its influence of elevating nitrate nitrogen, organic nitrogen, total phenols and protein precipitation content of the rooting matrix. Mycorrhizal morphotypes BS and SB were significantly more abundant in the community where these soil factors were low in the absence of leaf litter addition. Total ectomycorrhizal abundance was negatively related to hydrolysable tannin concentration in the rooting matrix ( r 2=0.132, P<0.05). There was no influence of leaf litter type on mite density (dominated by non-burrowing phthiracarids), but collembolan density (dominated by Folsomia spp) showed a greater than threefold reduction in population density in the presence of leaf litter ( F=6.47, P<0.05). Collembolan density was positively correlated with mycorrhizal morphotypes GS and SB ( P<0.05) and negatively related to morphotypes DB ( P<0.05) and soil extractable NH 4–N ( P<0.05), suggesting a possible selection of fungal species in their diet and a relationship between collembola and nitrification.

Variation in recruitment and early demography in Pinus rigida following crown fire in the pine barrens of Long Island, New York

1 Following severe, stand-replacing fires in 1995, we quantified emergence, growth and survival in Pinus rigida seedlings in eight stands in three areas of the pine barrens of Long Island, New York, USA, and examined factors contributing to spatial and temporal variation in recruitment. 2 We followed 6431 marked seedlings in the first cohort following fire, as well as additional cohorts in subsequent years, for 7 years to assess the effects of fire intensity, soil characteristics, intraspecific density, interspecific competition and facilitation on variation in early demography at three different scales. We found substantial variation in many of the demographic parameters measured between plots within stands (10–50 m apart), among stands within areas (600–1500 m apart), and among forest areas (5–30 km apart), as well as among years. 3 Almost all adult P. rigida in most of the stands studied were killed by the 1995 fires and population recovery therefore depended upon recruitment from seed. Initial recruitment appears to be largely determined by seed limitation, which was affected by fire intensity combined with serotiny and other factors. 4 Subsequent seedling survival and growth were determined largely by inherent differences among areas and sites in factors including cover of the shrub Quercus ilicifolia and soil texture and composition. 5 Initial seedling density, and subsequent survival and growth, varied among plots within sites, among sites within areas, and among areas. Early survival was negatively correlated with intraspecific seedling density, but was enhanced by neighbouring Q. ilicifolia, although these shrubs inhibited later seedling growth. Early demographic variation may determine many of the differences observed among mature populations in this landscape. 6 Variation in demographic parameters across space and time, and over a hierarchy of scales, may have critical consequences at the population, community and landscape levels. A comprehensive evaluation of the nature and extent of such demographic variation across different systems would have major implications for understanding vegetation patterns at the population, community and landscape levels.

Comparative skin permeability of neonatal and adult timber rattlesnakes ( Crotalus horridus)

Skin permeability and lipid content were determined using shed epidermis of neonatal and adult timber rattlesnakes ( Crotalus horridus) from the Coastal Plain Pine Barrens of New Jersey and from the Appalachian Mountains of northern Pennsylvania. Differences between populations due to habitat and within populations due to age were tested. Skin permeability was not found to differ according to locality ( P > 0.05), but rates were significantly different for age. Permeability of adult epidermis was greater than that of neonates ( P < 0.01). Lipid content did not differ by locality ( P > 0.05), but differed between ages, paralleling the results found for permeation rates. Neonate sheds had a greater amount of extractable lipids than adult sheds ( P < 0.01). Despite the lower skin permeability of neonates, our estimates indicate that the percentage of their total body water content lost per hour may still be 2.2 times that of adults. Resistance to cutaneous water loss may be advantageous to neonates given their relatively large surface area-to-volume ratio.

The Long Island Sound: a history of its people, places, and environment

Spanning the shores of Connecticut and Long Island, New York, the Long Island Sound is one of the most picturesque places in North America. From the discovery of the Sound in 1614, to the adventures of Captain Kidd, to the sinking of the Lexington in the sound in 1840, the Long Island Sound also holds a unique place in American history. The Long Island Sound traces the growth of fishing and shipbuilding villages along the sound to the development of major industrial ports, resort towns, and suburban communities along the sound. Marilyn Weigold discusses the subsequent overcrowding and pollution that resulted from this prosperity and expansion. Originally published in 1974 as The American Mediterranean and long out of print, The Long Island Sound has been updated by the author with a new preface and final chapter describing the Sound in the twenty-first century. In this new edition, Weigold particularly focuses on environmental concerns, and describes more current milestones, like the Long Island Pine Barrens Society, who fought and won in 1995 to set aside 100,000 acres as NY State's first forest preserve; the continuous construction of the Long Island Expressway, with its forty-one miles of HOV lanes; the attempt made by several of Connecticut's coastal cities to reinvigorate urban redevelopment; and the Long Island Sound Study's investigation of toxic substances--both natural and man-made--which continue to contaminate the waterway. Through over 40 stunning photographs and many fascinating stories, The Long Island Sound tells the history of a vastly populated, but underdiscussed, part of America.

Characterizing the properties of dissolved organic matter isolated by XAD and C-18 solid phase extraction and ultrafiltration

The properties of aquatic dissolved organic matter (DOM) isolated by solid phase extraction (SPE) C-18 cartridges, ultrafiltration, and XAD chromatography are compared. Samples taken from the Suwannee River, Georgia, USA and McDonalds Branch in the Pine Barrens, New Jersey, USA were chosen to represent waters where DOM originates from predominantly terrestrially-derived (allochthonous) precursors. Pony Lake, Antarctica represented an exclusively algal/microbially-derived (autochthonous) DOM. Fluorescence, UV absorption, 13C NMR spectroscopy, and high-pressure size exclusion chromatography (HPSEC) were employed to discern differences and similarities between the DOM isolated by these three methods. Only subtle differences between isolation methods were observed for the terrestrially derived DOM samples when assayed by light and fluorescence spectroscopy. Conversely, the Pony Lake DOM isolates exhibit greater variability when analyzed by these methods. 13C-NMR analyses showed structural differences between the methods for all samples. HPSEC analysis also revealed differences with the C-18 isolates exhibiting the highest molecular weights. Thus, it appears that each method isolates sufficiently different fractions of DOM that can only be delineated when a consortium of analytical methods are used to assay the samples. Nonetheless real differences between autochthonous and allochthonous derived DOM were observed with the algal-derived samples exhibiting high fluorescence ratios and lower aromaticity relative to the terrestrially derived materials. These results demonstrate that caution must be exercised when interpreting DOM reactivity data that rely upon the use of specific fractions.

Control of pitch pine seed germination and initial growth exerted by leaf litters and polyphenolic compounds

We investigated the influence of three concentrations of water extracts of three leaf litter species (pitch pine, huckleberry and white oak) and a mixture of all litters on the germination of pitch pine seeds and initial seedling growth in a microcosm experiment. All three plant species are important components of the pine barrens ecosystems in New Jersey, where it has been seen that pine seedling recruitment occurs only after stand replacing fire or in disturbed sites, where surface organic soil horizons and leaf litter have been removed. Leaf litter extracts did not influence seed germination, but significantly reduced seedling growth at high concentrations. There was little difference between the leaf litter species in growth suppression. As charcoal is a natural residue on the forest floor following fire, its influence on growth suppression was examined; it has been shown to immobilize polyphenols. Charcoal removed the inhibitory effect of leaf litter extracts and allowed the fertilizer effect of nutrients leached from the leaves to enhance seedling growth, particularly at the higher concentration of litter extract used. Responses to litter extracts were compared to four pure phenolic compounds, catchecol, p-coumaric acid, p-hydroxybenzoic acid and tannic acid. None of these compounds suppressed pine seedling growth, suggesting that these phenolics are not allelopathic to pine seedlings. The results are discussed in the context of fire as a driving factor in these oligotrophic and seasonally dry ecosystems and the interactions between nutrient supply and allelopathic chemistry of different leaf litters.

Impacts of atmospheric deposition on New Jersey pine barrens forest soils and communities of ectomycorrhizae

A gradient of increasing N deposition was identified in a southwestern to northeastern transect through the New Jersey pine barrens. The effect of this change in N deposition rate on soil chemistry and ectomycorrhizal morphotype community of pitch pine was studied by sampling from the field under mature pine trees, by planting bait seedlings into the field and in a greenhouse study where seedlings were given differential rates of N applications (0, 35, 140 kg ha −1 equivalent). The field transect showed a significant but small increase in N deposition from 0.35 to 0.72 kg N ha −1 (during the ca. 6 months of the study) equating to 7.84 ± 0.50 kg ha −1 year −1 at the northernmost site, 5.31 ± 0.70 at the middle and 3.66 ± 0.61 kg ha −1 year −1 N at the southwestern most site. Along this transect the ectomycorrhizal morphotype abundance and richness declined significantly under pitch pine. The decline in richness was significantly correlated with the N deposition rate. Bait pitch pine seedlings planted into one of the field sites and fertilized with increasing levels of N showed a reduction in ectomycorrhizal morphotype richness with increased N addition. In a greenhouse study, pine seedling biomass was inversely related to N addition. Nitrogen content of plants increased with increasing N supply, but P content of plants decreased, suggesting that P is a limiting nutrient in this ecosystem. Extractable N from the upper soil horizons increased in cores to which tree seedlings had been added as N addition increased. This indicates an approach to a critical loading of N for these oligotrophic soils, where N supply exceeds seedling N demand. In treeless cores N supply appears to exceed microbial immobilization potential even when no exogenous N is applied. As N supply to greenhouse seedlings increased, ectomycorrhizal morphotype richness declined. By combining data from the field and greenhouse studies, specific ectomycorrhizal morphotype groups were identified by their response to added N. Cortinarius- and Lactarius-like morphotypes were restricted to low levels of N availability. Suilloid- and Ascomycete-like morphotypes were more abundant as soil N availability increases, whereas Russula-like types showed an inverse relationship to N availability. We discuss the results from these oligotrophic sandy soils in comparison with European data derived from richer soils, where mycorrhizal fungal community responses appear to occur only at much higher levels of exogenous N. We attribute these differences to the evolved adaptations of pitch pine and their symbionts to growth in highly oligotrophic environments.

Changes in ectomycorrhizal communities and nutrient availability following prescribed burns in two upland pine–oak forests in the New Jersey pine barrens

Forests in the New Jersey pine barrens are frequently prescribed burned to reduce fuel loads and risk of wildfire. To acquire baseline data for effects of prescribed burns on ectomycorrhizal diversity and nutrient uptake, field studies were undertaken in two upland pine–oak forests in the New Jersey pine barrens subjected to different burn regimes. Ectomycorrhizal diversity was assessed by extraction of roots from soil cores and separation according to morphological characters. Nutrient availability to plant roots was measured using root bioassays. Relative to unburned plots, plots exposed to a fire at Greenwood, where burning was more frequent, had decreased total abundance of ectomycorrhizal tips, richness of ectomycorrhizal types, and Simpson's diversity in the L and F horizons, but increased Simpson's diversity in the deeper A horizon. At Lebanon, under a less frequent burn regime, richness was lower in whole cores and in the A horizon of burned versus unburned plots. Nitrogen, phosphorus, and potassium uptake by root bioassays indicated higher field availability of nutrients to roots in burned plots than roots in unburned plots, indicating a fertilization effect of the fire. Prescribed burning primarily impacted ectomycorrhizal community structure in the L and F horizons at these sites. Changes in function of ectomycorrhizae (nutrient uptake) in response to the burns was associated with decreased ectomycorrhizal diversity.

Climate-Growth Relationships for Native and Nonnative Pinaceae in Northern Michigan's Pine Barrens

Secondary growth responses of native and nonnative trees exposed to the same climatic conditions can elucidate sensitivities and thus adaptability to a particular region. A long-term mixed-species planting in the pine barrens of northern lower Michigan presented an opportunity to discriminate responses from species commonly planted in this region. Mean ring-width chronologies from living native Pinus resinosa Ait. and P. strobus L. and nonnative P. sylvestris L. and Picea abies (L.) Karst. at this plantation were generated, standardized, and analyzed by correlation analysis against mean monthly climatic variables. The native pine chronologies had the highest mean ring widths and signal-to-noise ratios (SNR), were highly correlated to each other, and exhibited positive responses to years with above-normal April temperatures but no significant relationships to variations in precipitation. The P. sylvestris chronology was highly correlated to the other two pine chronologies and responded similarly to April temperatures but exhibited negative correlations to January and April precipitation and positive correlations to September precipitation. The P. abies chronology had the highest mean sensitivity and was correlated with the P. strobus chronology but only responded positively to precipitation from the previous December. The low SNR (P. sylvestris, P. abies), high mean sensitivity (P. abies), and larger number of significant correlations to variations in monthly climatic variables (P. sylvestris) suggest that these nonnative species are more sensitive to this local climate. These results provide insights to the adaptability, establishment, and geographic distribution of the nonnative Pinaceae.

Integrating Landscape and Metapopulation Modeling Approaches: Viability of the Sharp‐Tailed Grouse in a Dynamic Landscape

Abstract: The lack of management experience at the landscape scale and the limited feasibility of experiments at this scale have increased the use of scenario modeling to analyze the effects of different management actions on focal species. However, current modeling approaches are poorly suited for the analysis of viability in dynamic landscapes. Demographic (e.g., metapopulation) models of species living in these landscapes do not incorporate the variability in spatial patterns of early successional habitats, and landscape models have not been linked to population viability models. We link a landscape model to a metapopulation model and demonstrate the use of this model by analyzing the effect of forest management options on the viability of the Sharp‐tailed Grouse ( Tympanuchus phasianellus) in the Pine Barrens region of northwestern Wisconsin (U.S.A.). This approach allows viability analysis based on landscape dynamics brought about by processes such as succession, disturbances, and silviculture. The landscape component of the model (LANDIS) predicts forest landscape dynamics in the form of a time series of raster maps. We combined these maps into a time series of patch structures, which formed the dynamic spatial structure of the metapopulation component (RAMAS). Our results showed that the viability of Sharp‐tailed Grouse was sensitive to landscape dynamics and demographic variables such as fecundity and mortality. Ignoring the landscape dynamics gave overly optimistic results, and results based only on landscape dynamics (ignoring demography) lead to a different ranking of the management options than the ranking based on the more realistic model incorporating both landscape and demographic dynamics. Thus, models of species in dynamic landscapes must consider habitat and population dynamics simultaneously.

A multi-scale analysis of species–environment relationships: rare moths in a pitch pine–scrub oak ( Pinus rigida–Quercus ilicifolia) community

Community level analyses of species–environment relationships can provide critical information for conservation planners. A comprehensive analysis of the factors that influence species distributions should include variables measured at multiple scales because species–environment relationships are known to vary with the scale of observation. The pitch pine–scrub oak ( Pinus rigida–Quercus ilicifolia) communities, or pine barrens, of the northeastern USA are severely threatened by development and fire suppression. They also provide critical habitat for many species of rare moths. We used partial canonical correspondence analysis to assess the relative effects of three levels of environmental variables (plot, patch, and landscape) on the distribution and abundance of 10 species of rare moths in a pine barrens community in southeastern Massachusetts, USA. We also used a set of spatial variables to quantify and partial out the effects of spatial autocorrelation of species composition among sampling locations. All three levels of environmental factors combined, independent of spatial factors, accounted for virtually half (48.4%) of the total variation in the moth community. Sequential partitioning of the variance explained by each level of environmental factors indicated that landscape level factors explained more than twice as much variance as plot and patch level factors. Another environmental model that included only landscape level variables explained 53% of the total variation in the moth community. Patch density and percentage of the landscape comprised of open and sparse canopy, scrub oak habitats were the most significant variables. These results suggest that the presence of scrub oak habitat within relatively large, heterogeneous landscape mosaics may be more important for the maintenance of many rare pine barrens associated moth populations than plot or patch level characteristics.

Forest Invasibility in Communities in Southeastern New York

While biological invasions have been the subject of considerable attention both historically and recently, the factors controlling the susceptibility of communities to plant invasions remain controversial. We surveyed 44 sites in southeastern New York State to examine the relationships between plant community characteristics, soil characteristics, and nonnative plant invasion. Soil nitrogen mineralization and nitrification rates were strongly related to the degree of site invasion (F= 30.2, P < 0.0001 and F= 11.8, P < 0.005, respectively), and leaf C : N ratios were negatively correlated with invasion (R2= 0.22, P < 0.0001). More surprisingly, there was a strong positive relationship between soil calcium levels and the degree of site invasion (partial r= 0.70, P < 0.01), and there were also positive relationships between invasion and soil magnesium and phosphorus. We found, in addition, a positive factor-ceiling relationship between native species diversity and invasive species diversity. This positive relationship between native and invasive diversity contradicts earlier hypotheses concerning the relationships between species diversity and invasion, but supports some recent findings. Cluster analysis distinguished two broad forest community types at our sites: pine barrens and mixed hardwood communities. Invaders were significantly more abundant in mixed hardwood than in pine barrens communities (Mann–Whitney U = 682.5, P < 0.0001). Even when evaluating the mixed hardwood communities alone, invasion remained significantly positively correlated with soil fertility (calcium, magnesium, and net nitrogen mineralization rates). Soil texture and pH were not useful predictors of the degree to which forests were invaded. Nitrogen and calcium are critical components of plant development, and species better able to take advantage of increased nutrient availability may out-perform others at sites with higher nutrient levels. These results have implications for areas such as the eastern United States, where anthropogenic changes in the availability of nitrogen and calcium are affecting many plant communities.

Influence of landscape composition on sharp-tailed grouse lek location and attendance in Wisconsin pine barrens

:Populations of sharp-tailed grouse (Tympanuchus phasianellus) in the upper Midwest are in danger of extirpation due to habitat loss caused by succession, tree planting, and control of wildfire. Sharp-tailed grouse in Wisconsin have persisted primarily on reserves maintained in early succession using prescribed burning and mechanical disturbance. However, during the late 1990s the highest and densest populations of sharp-tailed grouse in Wisconsin were found in a complex of clearcuts in southeastern Douglas County. We compared landcover composition and fragmentation at multiple scales within 2.4 km of 36 sharp-tailed grouse leks and 213 unused locations in a 1,350-km2 study area in the pine barrens of northwestern Wisconsin. Leks were located on managed reserves (n = 11) and habitats recently created by timber harvest (n = 23) and wildfire (n = 2). Leks were clustered in the landscape, with distance to nearest neighbour lek shorter for leks than unused points. Leks were characterized by higher proportions of grass and shrub cover classes, lower proportions of forest, fewer forest patches, and greater distances to forest edge relative to unused points. Proportions of grass and shrub cover classes, distance to nearest lek, and distance to forest edge were strong predictors of lek presence in a logistic regression model. Differences between leks and unused points varied with scale of sampling. Response of sharp-tailed grouse to indices of fragmentation varied among scales and metrics. Number of sharp-tailed grouse attending leks was positively associated with recently created habitat and proportion of grass cover in the landscape.

Variations in the composition and adsorption behavior of dissolved organic matter at a small, forested watershed

This study investigated the properties and sorption by goethite of bulk (unfractionated) dissolved organic matter (DOM) from surface and shallow groundwaters at McDonalds Branch, a small freshwater fen in the New Jersey Pine Barrens (USA). Water samples were collected in the spring and fall seasons from two surface-water sampling sites, an upstream potential recharge area and a downstream discharge area, as well as from a set of in-stream nested wells in the upstream potential recharge area. Changes in DOM concentration, molecular weight distribution, and molar absorptivity at 280 nm were measured. Surface and shallow (1.6 m below land surface) groundwater samples collected in spring 1997 in the potential recharge zone (actual recharge impeded by an extensive clay lens) were found to be very similar in terms of DOM concentrations and physicochemical properties and is believe to originate from a common source. Samples taken in fall 1997 yielded no surface water because of drought conditions, and the shallow groundwater DOM collected from the recharge well contained significantly less and chemically altered DOM. This change in chemical properties is believed to be caused in part by fractionation resulting from sorption to mineral phases. Batch isotherm experiments show that sorption by goethite of the DOM from both spring surface and shallow groundwaters in the potential recharge area were similar, whereas the fall groundwater possessed a much lower affinity for the sorbent. This study demonstrated that shallow groundwaters collected under different climatic and hydrologic conditions (spring, high flow versus fall, drought conditions) resulted in different physicochemical properties and adsorption affinities.

Reforesting the jack pine barrens: a long-term common garden experiment

Long-term common garden experiments provide the unique opportunity to assess the individual life-long and regeneration response of different tree species to their shared environment. The survival, growth, and regeneration of three locally native, 22 regionally native, and 16 nonnative (exotic to North America) tree species were measured in a common garden experiment established in 1888 on the jack pine barrens of northern lower Michigan. None of the stems from the 32 hardwood species survived. The conifers Pinus resinosa (35%), Picea abies (24%), and Pinus strobus (7%) had the highest survival of original stems; several stems of Juniperus virginiana, Picea glauca, Pinus rigida, and Thuja occidentalis also survived. Regeneration was dominated by Pinus strobus, P. resinosa, Picea abies, and Pinus sylvestris in the plantation and by P. strobus, unplanted P. banksiana, P. sylvestris, and unplanted Quercus spp. in the old field next to the plantation. Regeneration from Prunus serotina, Populus alba, Robinia pseudoacacia, Fraxinus americana, Acer rubrum, and A. platanoides was present in the plantation and/or adjacent old field. The survival, relatively low productivity (site indices of 28–29 for Picea spp. and 44–45 for Pinus resinosa and P. strobus), and regeneration of the species planted at this site indicate that P. resinosa is the best species for wood production while P. strobus would be best to provide long-term forest cover. The nonnative Pinus sylvestris and Picea abies performed as well as or better than species native to the jack pine barrens. Pinus sylvestris is successfully recruiting outside of the original plantation next to the native early successional species P. banksiana and P. strobus. Within the plantation, Picea abies had high survival and regenerated as much as the native dominant Pinus strobus. The naturalization of nonnative Pinus sylvestris and Picea abies in this plantation suggests that these species have the potential to become invasive in the jack pine barren ecosystem.

Spatial patterns of cone serotiny in Pinus banksiana in relation to fire disturbance

Fire disturbance effects on tree species distribution and landscape pattern have been widely studied. However, the effects of differences among fire regimes on the spatial pattern of genetic variability within a tree species have received less attention. The objectives of this study were to examine (a) whether the marked gradient in serotiny in Pinus banksiana along its southern range limit is related to differences in fire regimes and (b) at what scale serotiny varies most strongly in P. banksiana in the US Midwest. P. banksiana in the 450,000 ha Pine Barrens area in northwestern Wisconsin, USA showed a marked broad scale pattern in serotiny. The percentage of serotinous trees was highest in the northeast (mean 83%, S.D. 13.5) and lowest in the southwest (mean 9%, S.D. 3.7). Historic fire regimes were inferred from pre-European settlement (mid-1800s) vegetation data. Serotiny was highest in pine forests that exhibited stand-replacing fires, and lowest in savannas where more frequent but less intense ground fires occurred. The data presented in this study suggest possible spatial control of genetic variability within a tree species by an ecological process (disturbance) at the landscape-scale.

Soil Respiration at Dominant Patch Types within a Managed Northern Wisconsin Landscape

Soil respiration (SR), a substantial component of the forest carbon budget, has been studied extensively at the ecosystem, regional, continental, and global scales, but little progress has been made toward understanding SR over managed forest landscapes. Soil respiration is often influenced by soil temperature (Ts), soil moisture (Ms), and type of vegetation, and these factors vary widely among the patch types within a landscape. We measured SR, Ts, Ms, and litter depth (LD) during the 1999 and 2000 growing seasons within six dominant patch types (mature northern hardwoods, young northern hardwoods, clear-cuts, open-canopy Jack pine barrens, mature Jack pine, and mature red pine) on a managed forest landscape in northern Wisconsin, USA. We compared SR among and within the patch types and derived empirically based models that relate SR to Ts, Ms, and LD. Increased levels of soil moisture and higher temperatures in June–September 1999 may have accounted for the up to 37% overall higher SR than in this same period in 2000. In 2000, SR and Ts values were lower, and the sites may have been experiencing slight water limitations, but in general Ts was a much more accurate predictor of SR during this year. Empirical predictions of SR within each patch type derived from continuous Ts measurements were in close agreement with measured values of SR during 2000, but eight of 22 of the simulated values were significantly different (α = 0.05) from the rates measured in 1999. The young hardwoods consistently had the highest SR, whereas the pine barrens had the lowest. Results from our field studies and empirical models can help land managers assess landscape responses to potential disturbances and climatic changes.