Jersey Pine Barrens Research Articles

Tree Regeneration in Oak-Pine Stands with and without Prescribed Fire in the New Jersey Pine Barrens: Management Implications

Abstract This is a case study comparing understory tree regeneration in two mixedwood stands types in the New Jersey Pine Barrens: oak‐pine treated with prescribed fire over the last half century (burned) and oak‐pine without a history of controlled burning (unburned). Understories of burned stands supported mainly desirable oak (Quercus spp.) and pine (Pinus spp.) regeneration (0.3 ft tall, <3 in. dbh), whereas the understories of unburned stands supported a greater abundance of undesirable, nonoak hardwoods (mainly sassafras [Sassafras albidum]) along with good numbers of oak regeneration and, unexpectedly, pine saplings (≥4.5 ft tall, <3 in. dbh). A regime of prescribed fire applied on an ∼6-year interval during the last half century appears to have reduced or excluded nonoak hardwoods, with the exception of hickory (Carya spp.). Maintaining oak‐pine mixtures on sites similar to the unburned stands used in this study may require silvicultural intervention.

Canopy stomatal conductance following drought, disturbance, and death in an upland oak/pine forest of the new jersey pine barrens, USA.

Stomatal conductance controls carbon and water fluxes in forest ecosystems. Therefore, its accurate characterization in land-surface flux models is necessary. Sap-flux scaled canopy conductance was used to evaluate the effect of drought, disturbance, and mortality of three oak species (Quercus prinus, Q. velutina, and Q. coccinea) in an upland oak/pine stand in the New Jersey Pine Barrens from 2005 to 2008. Canopy conductance (GC) was analyzed by performing boundary line analysis and selecting for the highest value under a given light condition. Regressing GC with the driving force vapor pressure deficit (VPD) resulted in reference canopy conductance at 1 kPa VPD (GCref). Predictably, drought in 2006 caused GCref to decline. Q. prinus GCref was least affected, followed by Q. coccinea, with Q. velutina having the highest reductions in GCref. A defoliation event in 2007 caused GCref to increase due to reduced leaf area and a possible increase in water availability. In Q. prinus, GCref quadrupled, while doubling in Q. velutina, and increasing by 50% in Q. coccinea. Tree mortality in 2008 led to higher GCref in the remaining Q. prinus but not in Q. velutina or Q. coccinea. Comparing light response curves of canopy conductance (GCref) and stomatal conductance (gS) derived from gas-exchange measurements showed marked differences in behavior. Canopy GCref failed to saturate under ambient light conditions whereas leaf-level gS saturated at 1,200 μmol m−2 s−1. The results presented here emphasize the differential responses of leaf and canopy-level conductance to saturating light conditions and the effects of various disturbances (drought, defoliation, and mortality) on the carbon and water balance of an oak-dominated forest.

Resolution of Respect: Professor Paul Schultz Martin 1928–2010

Resolution of Respect: Professor Paul Schultz Martin 1928–2010

Plant Communities of the Burden Hill Forest, Salem County, New Jersey

The plant community types on three tracts within the Burden Hill Forest, a distinctive outlier of the New Jersey Pine Barrens, are described and classified. While these tracts consist largely of a general pine barrens type, they display a number of significant differences from the main body of the Pine Barrens. These differences include additional forest plant community types previously undescribed for New Jersey, higher heterogeneity of community types and woody plant diversity, and the presence of several unusual or rare species including Castanea pumila (Allegheny Chinquapin).

A correlation between chytrid abundance and ecological integrity in New Jersey pine barrens waters

Zoosporic fungi (chytrid) abundance, as captured on pollen bait, was significantly higher in pristine sites than impacted sites in a survey of six water bodies of varying ecological integrity (as categorized by the NJ Pinelands Commission) in the New Jersey pine barrens (USA). Using a series of laboratory manipulations of water from a pristine and an impacted site, altered pH appeared to be the primary driver of zoosporic fungi abundance in the field. Increasing pH of the naturally acid water of the pine barrens, significantly reduced zoosporic fungal populations and a reduction of pH of impacted water ameliorated conditions and increased abundance. The addition of nitrogen or phosphorus to, or an increase in specific conductance of, pristine water reduced zoosporic fungal abundance, but a reduction in these parameters in impacted water did not induce restoration of zoosporic fungi. These results show zoosporic fungi have potential as bioindicators of pollution.

Impact of insect defoliation on forest carbon balance as assessed with a canopy assimilation model

AbstractDisturbances such as fire, hurricanes, and herbivory often result in the net release of CO2 from forests to the atmosphere, but the magnitude of carbon (C) loss is poorly quantified and difficult to predict. Here, we investigate the carbon balance of an oak/pine forest in the New Jersey Pine Barrens using the Canopy Conductance Constrained Carbon Assimilation (4C‐A) model. The 4C‐A model utilizes whole‐tree sap‐flux and leaf‐level photosynthetic gas exchange measurements at distinct canopy levels to estimate canopy assimilation. After model parameterization, sensitivity analyses, and evaluation against eddy flux measurements made in 2006, the model was used to predict C assimilation for an undisturbed year in 2005, and in 2007 when the stand was completely defoliated for 2–3 weeks during an infestation of gypsy moths (Lymantria dispar L.). Following defoliation, only 50% of the foliage reemerged in a second flush. In 2007, canopy net assimilation (AnC), as modeled with the 4C‐A, was reduced to approximately 75% of AnC in 2006 (940 vs. 1240 g C m−2 a−1). Overall, net primary production (NPP) in 2007 was approximately 240 g C m−2 a−1 (vs. 250 g C m−2 a−1 in 2006), with 60% of NPP allocated to foliage production, a short‐term carbon pool. Woody biomass accumulation, a long‐term carbon pool, was reduced by 20% compared with the previous year (72 vs. 57 g C m−2 a−1 in 2006 and 2007, respectively). The overall impact of the defoliation spanned 21% of upland forests (320 km2) in the New Jersey Pine Barrens, representing a significant amount of overall C not being taken up from the atmosphere by the forest, thus not accumulated in the biosphere.

Invasive insects impact forest carbon dynamics

AbstractInvasive insects can impact ecosystem functioning by altering carbon, nutrient, and hydrologic cycles. In this study, we used eddy covariance to measure net CO2 exchange with the atmosphere (NEE), and biometric measurements to characterize net ecosystem productivity (NEP) in oak‐ and pine‐dominated forests that were defoliated by Gypsy moth (Lymantria dispar L.) in the New Jersey Pine Barrens. Three years of data were used to compare C dynamics; 2005 with minimal defoliation, 2006 with partial defoliation of the canopy and understory in a mixed stand, and 2007 with complete defoliation of an oak‐dominated stand, and partial defoliation of the mixed and pine‐dominated stands. Previous to defoliation in 2005, annual net CO2 exchange (NEEyr) was estimated at −187, −137 and −204 g C m−2 yr−1 at the oak‐, mixed‐, and pine‐dominated stands, respectively. Annual NEP estimated from biometric measurements was 108%, 100%, and 98% of NEEyr in 2005 for the oak‐, mixed‐, and pine‐dominated stands, respectively. Gypsy moth defoliation strongly reduced fluxes in 2006 and 2007 compared with 2005; NEEyr was −122, +103, and −161 g C m−2 yr−1 in 2006, and +293, +129, and −17 g C m−2 yr−1 in 2007 at the oak‐, mixed‐, and pine‐dominated stands, respectively. At the landscape scale, Gypsy moths defoliated 20.2% of upland forests in 2007. We calculated that defoliation in these upland forests reduced NEEyr by 41%, with a 55% reduction in the heavily impacted oak‐dominated stands. ‘Transient’ disturbances such as insect defoliation, nonstand replacing wildfires, and prescribed burns are major factors controlling NEE across this landscape, and when integrated over time, may explain much of the patterning of aboveground biomass and forest floor mass in these upland forests.

Ectomycorrhizal responses to organic and inorganic nitrogen sources when associating with two host species

While it is established that increasing atmospheric inorganic nitrogen (N) deposition reduces ectomycorrhizal fungal biomass and shifts the relative abundances of fungal species, little is known about effects of organic N deposition. The effects of organic and inorganic N deposition on ectomycorrhizal fungi may differ because responses to inorganic N deposition may reflect C-limitation. To compare the effects of organic and inorganic N additions on ectomycorrhizal fungi, and to assess whether host species may influence the response of ectomycorrhizal fungi to N additions, we conducted an N addition experiment at a field site in the New Jersey pine barrens. Seedlings of two host species, Quercus velutina (black oak) and Pinus rigida (pitch pine), were planted at the base of randomly-selected mature pitch pine trees. Nitrogen was added as glutamic acid, ammonium, or nitrate at a rate equivalent to 227.5 kg ha −1 y −1 for eight weeks, to achieve a total application of 35 kg ha −1 during the 10-week study period. Organic and inorganic N additions differed in their effects on total ectomycorrhizal root tip abundance across hosts, and these effects differed for individual morphotypes between oak and pine seedlings. Mycorrhizal root tip abundance across hosts was 90 % higher on seedlings receiving organic N compared to seedlings in the control treatment, while abundances were similar among seedlings receiving the inorganic N treatments and seedlings in the control. On oak , 33–83 % of the most-common morphotypes exhibited increased root tip abundances in response to the three forms of N, relative to the control. On pine , 33–66 % of the most-common morphotypes exhibited decreased root tip abundance in response to inorganic N, while responses to organic N were mixed. Plant chemistry and regression analyses suggested that, on oak seedlings, mycorrhizal colonization increased in response to N limitation. In contrast, pine root and shoot N and C contents did not vary in response to any form of N added, and mycorrhizal root tip abundance was not associated with seedling N or C status, indicating that pine received sufficient N. These results suggest that in situ organic and inorganic N additions differentially affect ectomycorrhizal root tip abundance and that ectomycorrhizal fungal responses to N addition may be mediated by host tree species.

Decision support tools to improve the effectiveness of hazardous fuel reduction treatments in the New Jersey Pine Barrens

Our goal is to assist the New Jersey Forest Fire Service and federal wildland fire managers in the New Jersey Pine Barrens evaluate where and when to conduct hazardous fuel reduction treatments. We used remotely sensed LIDAR (Light Detection and Ranging System) data and field sampling to estimate fuel loads and consumption during prescribed fire treatments. This information was integrated with data on prescribed fire treatments conducted by the New Jersey Forest Fire Service over the last 15 years to produce and interpret maps of current fuel loads. Forest productivity measurements and models were then used to estimate rates of fuel accumulation through time. We could then calculate return intervals for desired fuel load conditions. Through formal workshops and frequent discussions with state and federal fire managers, our results enhance the ability of these agencies to make key decisions regarding the effectiveness and longevity of hazardous fuels treatments.

FT-IR study of the changes in carbohydrate chemistry of three New Jersey pine barrens leaf litters during simulated control burning

Low intensity control burns are a standard fuel reduction management tool used in pine barrens ecosystems. Periodic disturbances through fire can be an important influence on the cycling of nutrients within the ecosystem. Previous studies have shown that the inorganic chemistry of leaf litter residues differs with increasing temperature. Our study compared chemical changes in white oak ( Quercus alba), pitch pine ( Pinus rigida) and black huckleberry ( Gaylussacia baccata), characteristic of the New Jersey pine barrens, during thermal decomposition using FT-IR spectroscopy. Three replicates of senescent leaf material were ground and separately heated for 2 h at: 100, 200, 300, 400 and 550 °C. These temperatures are representative of the range seen in fuel reducing prescribed burns in the pine barrens. Unburned litter of each species was used as a control. An optimization process using varying amounts of KBr and oak litter was performed to develop favorable FT-IR spectral conditions for a sample to KBr ratio of 0.75%. Chemometric analysis of the FT-IR spectra using principal component analysis (PCA) was used to analyze the changes in carbohydrate chemistry of each litter plant species (leaf litter species) at each temperature. In general, it appears that there is clear separation of leaf litter species at the different combustion temperatures. Infrared spectroscopy illustrated that all three species shared wavenumbers characteristic of the primary components of leaves such as cellulose, lignin and hemicellulose. Results from the PCA indicated separation of litter species and species by combustion temperature. PC axis 1 corresponds to the effects of temperature on leaf litter species and PC axis 2 separates the leaf litter species. At the low temperatures (control-200 °C), oak, pine and huckleberry litter species separated from each other. Wavenumbers that contributed to the separation of species at low temperatures belonged to functional group stretching frequencies of outer surface waxes, basic sugars, fatty acids and aldehydes. It appears that oak had more IR bands specific to suberin content. Convergence of these species occurs at 300 °C. Complexity of chemical composition decreases at this particular temperature as is shown by the decrease in wavenumber richness when compared to litters at low and high temperatures. Oak, pine and huckleberry had similar IR spectra showing bands belonging to outer surface wax content, pectin, lignin and hemicellulose. With increasing temperatures (400–550 °C), differences between litter species increased slightly. Plant material was reduced to similar composition due to thermal decomposition, which consisted of inorganic materials such as carbonate, phosphate and sulfate ions and possible fused aromatics.

Simulation of forest change in the New Jersey Pine Barrens under current and pre-colonial conditions

Changes in land use patterns in and around forests, including rural development and road building, have occurred throughout the United States and are accelerating in many areas. As a result, there have been significant departures from ‘natural’ or pre-settlement disturbance regimes. Altered disturbance regimes can shift composition and dominance in tree species communities, potentially affecting ecosystem functioning. We examined the potential consequences of various forest management practices and forest fragmentation on tree community composition. Both forest management and fragmentation are changing as land use changes within the New Jersey Pine Barrens (NJPB). The NJPB has and is continuing to experience rapid rural development and urbanization that are altering the types, frequency, and intensity of forest management, and are increasing forest fragmentation. In the NJPB, the size and frequency of wildfires have declined and the use of prescribed fires is limited to a small portion of the landscape. In addition, the expansion of roads and decline in total forested area – two common measures of fragmentation – may impede the ability of tree species to colonize available habitat. To assess the consequences of fire management and fragmentation on fire regimes and forest communities, we simulated forest landscape change using LANDIS-II, a stochastic, spatially dynamic forest succession model that simulates the growth of tree species cohorts (defined by species and age), dispersal and colonization, and mortality. Simulated fires are sensitive to fuel loads and fuel load continuity. We constructed scenarios to mimic the pre-colonial contiguous landscape with an estimated pre-colonial fire regime; scenarios of the current day landscape with current and potential fire management; and scenarios designed to highlight the effects of fragmentation. Our simulations indicate that relative to the pre-colonial landscape and fire regime, the landscape is changing from a pine-dominated to an oak-dominated state. However, within areas where prescribed burning remains a viable management option, a doubling of the mean annual area that is managed with prescribed burns may substantially push the system back towards pre-colonial conditions, although oaks will continue to retain a higher than pre-colonial dominance. Our results also indicate that aside from a reduction in the potential fire sizes, fragmentation does not appear to substantially alter forest successional dynamics. In summary, our simulations estimate the departure from pre-colonial conditions and indicate the potential for a limited restoration of these conditions.

Activity Ranges and Habitat Use of Lampropeltis getula getula (Eastern Kingsnakes)

Abstract The habitat use and activity range of Lampropeltis getula getula (Eastern Kingsnake) in the New Jersey Pine Barrens were studied from 1996–1998. Five male and four non-gravid female Eastern Kingsnakes were routinely radiotracked during daylight hours during one or two active seasons. Habitat and climatic conditions at snake locations were characterized using 9 climatic and 14 structural habitat features. Multivariate statistical comparisons with randomly selected locations indicated that Eastern Kingsnakes use available habitat in a non-random fashion with respect to microhabitat features (Wilks' lambda = 0.511; df = 28, 1066; P < 0.01). Eastern Kingsnakes preferred sites with thick leaf litter and dense shrub-layer foliage. They used a broad range of macrohabitats that spanned both wetland and pine-dominated upland areas. Moist areas were used for hibernation. Snakes exhibited a largely fossorial lifestyle, spending a great proportion of their time concealed under the cover of soil and/or leaf l...

Temporal change in forest fragmentation at multiple scales

Previous studies of temporal changes in fragmentation have focused almost exclusively on patch and edge statistics, which might not detect changes in the spatial scale at which forest occurs in or dominates the landscape. We used temporal land-cover data for the Chesapeake Bay region and the state of New Jersey to compare patch-based and area–density scaling measures of fragmentation for detecting changes in the spatial scale of forest that may result from forest loss. For the patch-based analysis, we examined changes in the cumulative distribution of patch sizes. For area–density scaling, we used moving windows to examine changes in dominant forest. We defined dominant forest as a forest parcel (pixel) surrounded by a neighborhood in which forest occupied the majority of pixels. We used >50% and ≥60% as thresholds to define majority. Moving window sizes ranged from 2.25 to 5,314.41 hectares (ha). Patch size cumulative distributions changed very little over time, providing no indication that forest loss was changing the spatial scale of forest. Area–density scaling showed that dominant forest was sensitive to forest loss, and the sensitivity increased nonlinearly as the spatial scale increased. The ratio of dominant forest loss to forest loss increased nonlinearly from 1.4 to 1.8 at the smallest spatial scale to 8.3 to 11.5 at the largest spatial scale. The nonlinear relationship between dominant forest loss and forest loss in these regions suggests that continued forest loss will cause abrupt transitions in the scale at which forest dominates the landscape. In comparison to the Chesapeake Bay region, dominant forest loss in New Jersey was less sensitive to forest loss, which may be attributable the protected status of the New Jersey Pine Barrens.

Production and characterization of synthetic wood chars for use as surrogates for natural sorbents

Wood char is an important source of environmental black carbon that affects the fate of organic contaminants in soils and sediments and plays a role in carbon cycling. Currently, the research community has need for char standards for laboratory use that are representative of naturally occurring chars. This investigation presents a scientific approach to the production of synthetic chars that have properties of a natural char produced by forest fire. The natural char examined for this purpose was that of a pitch pine obtained from the New Jersey Pine Barrens; however, the developed characterization approach is more generally applicable toward understanding and producing surrogate synthetic materials for any natural wood char. Small blocks of pitch pine wood were pyrolyzed using ramp rates between 30 and 1000 °C/h and with maximum temperatures between 450 and 1000 °C. The chars were then characterized using helium-based solid density, electrical resistivity, H/C ratio, PAH analysis and surface area measurements. A comparison of these key parameters among the synthetic and natural chars clearly demonstrated that the natural char had experienced maximum temperatures of 500–600 °C. Additional studies based on re-heating suggest that the char had experienced very rapid heating rates (greater than 200 °C/h) during its formation.

Mineralization of forest litter nutrients by heat and combustion

Temperature dependant mineralization dynamics during fire of litter species characteristic of the New Jersey pine barrens was determined. Senescent leaf material of pitch pine ( Pinus rigida), white oak ( Quercus alba) and black huckleberry ( Gaylusssacia baccata) were collected at the time of abscission; sorted, ground and oven-dried at 70 °C. Replicate samples were then heated for 2 h at: 70, 100, 200, 300, 400, and 550 °C. Mass loss and total nitrogen and total phosphorus concentration of the heated material were determined. Additional samples of the residual material were extracted with deionized water, and the filtrate was assayed for the anions: NO 3 − , PO 4 − 3 , SO 4 − 2 ; and cations: NH 4 + , K +, Mg ++, and Ca ++. By heating leaf litter over a range of temperatures, to simulate the heterogeneous nature of forest litter burning, we identified patterns of nutrient mineralization characteristic of specific temperatures, some of which were common to all three litter species and others unique to individual species. In general, it appears that black huckleberry leaf litter was the most nutrient rich and the most labile. In huckleberry litter, there was a large reserve of soluble nitrogen, sulfur, phosphate, calcium and magnesium that became available upon heating to 200 °C. Pitch pine litter was the most nutrient poor, and the rates of nutrient mineralization were also generally the lowest of the three species studied. White oak litter nutrient concentration and rates of mineralization along the temperature gradient were intermediate. For all three litter species examined organic and inorganic nitrogen losses due to volatilization were >99% upon heating to 550 °C, and soluble magnesium concentrations declined significantly at temperatures of 300 °C, despite having a volatilization temperature greater than 1100 °C. Under the temperature range employed, heating of leaf litter resulted in little volatilization loss of phosphorus; however, the amount of soluble phosphate phosphorus was much lower in all three litter types at temperatures of 300 °C and above. With increasing temperatures, inorganic phosphate ions presumably became bound to cations in the ash, forming insoluble metal phosphates. The dramatic increase of the ratio of total phosphorus to soluble inorganic phosphate at higher temperatures, the loss of soluble magnesium above 300 °C, and the near complete loss of nitrogen at 550 °C suggests that after intense fires availability of these minerals may be dramatically reduced.

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.

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.

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.

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.