Search

Effective management of bark beetle infestations requires prompt detection of attacked trees. Early attack is also called green attack, since tree foliage does not yet show any visible signs of tree decline. In several bark beetle systems, including mountain pine beetle and European spruce bark beetle, unpiloted aerial vehicle (UAV)-based remote sensing has successfully detected early attack. We explore the utility of remote sensing for early attack detection of southern pine beetle (SPB; Dendroctonus frontalis Zimm.), paired with detailed ground surveys to link tree decline symptoms with SPB life stages within the tree. In three of the northernmost SPB outbreaks in 2022 (Long Island, New York), we conducted ground surveys every two weeks throughout the growing season and collected UAV-based multispectral imagery in July 2022. Ground data revealed that SPB-attacked pitch pines (Pinus rigida Mill.) generally maintained green foliage until SPB pupation occurred within the bole. This tree decline behavior illustrates the need for early attack detection tools, like multispectral imagery, in the beetle's northern range. Balanced random forest classification achieved, on average, 78.8% overall accuracy and identified our class of interest, SPB early attack, with 68.3% producer's accuracy and 72.1% user's accuracy. After removing the deciduous trees and just mapping the pine, the overall accuracy, on average, was 76.9% while the producer's accuracy and the user's accuracy both increased for the SPB early attack class. Our results demonstrate the utility of multispectral remote sensing in assessing SPB outbreaks, and we discuss possible improvements to our protocol. This is the first remote sensing study of SPB early attack in almost 60 years, and the first using a UAV in the SPB literature. [ABSTRACT FROM AUTHOR]

For the purposes of chemotaxonomic distinction of four pine species Pinus nigra, Pinus ponderosa, Pinus rigida and Pinus sylvestris growing in the suburban landscape of the central part of the Czech Republic, resin extracts from tree trunks, needles and female cones were analysed using gas chromatography-mass spectroscopy. Monoterpenes were shown to be the main terpene fraction of the resins of all studied pine species. On average, they made up 80% of the total terpene content. A characteristic monoterpene for distinguishing pine species was β-pinene, with high levels in P. ponderosa, moderate levels in P. rigida and low levels in P. sylvestris and P. nigra. P. sylvestris contained only trace amount of Δ-3-carene (0.6%) in resins from needles and thus belongs to the α-pinene chemotypic variation. Slight seasonal variability in terpene production was found for resins from needles of P. nigra and P. sylvestris. When comparing European populations according to the monoterpene composition of resins from needles, it can be stated that the α-pinene content increased in the order P. ponderosa < P. rigida < P. nigra < P. sylvestris while the β-pinene content changed in the opposite direction. This statement confirms the terpene biosynthesis uniformity of European pines. [ABSTRACT FROM AUTHOR]

Climate change is facilitating a novel range expansion of southern pine beetle (SPB) into globally rare north‐eastern pitch pine barrens.By assessing stand conditions present in SPB‐infested and uninfested pitch pine stands on Long Island, NY, USA, we developed a regionally‐calibrated hazard rating model that predicts stand‐level SPB susceptibility.The model indicates that a stand's SPB susceptibility increases with (1) increasing pitch pine basal area, (2) increasing instances of previous year SPB spots nearby, and (3) sandy soil texture.The model informs adaptation strategies to a novel pest dynamic by supporting the identification and prioritization of high hazard stands for prevention management.An alignment between treatments effective in reducing SPB vulnerability and conserving pine barrens communities indicates that pine barrens can be managed both to improve resilience to future threats and preserve historic ecological conditions. [ABSTRACT FROM AUTHOR]

Fire is a strong ecological and evolutionary driver of plant species and terrestrial ecosystem dynamics. Numerous studies have shown that plant species vary widely in their flammability and associated traits that coincide with clear strategies of persistence in fire‐prone ecosystems. Yet, intraspecific variation and phenotypic plasticity in plant flammability has received substantially less attention. Some evidence has demonstrated high plasticity in flammability among populations in species adapted to low‐frequency, high severity fire regimes which suggests the capacity of local adaptation; however, intraspecific variability of species in high‐frequency, low severity fire regimes has not been conducted. Given that frequent fire‐adaptive species tend to produce fast‐flammable litter that is associated with survival following fire, we hypothesized that these species would have highly conserved leaf traits with low variation in litter flammability.We used an existing common garden study to test our hypothesis in Pinus rigida (pitch pine) with source populations that span most of its distribution in eastern North America. We examined both phenotypic and genotypic variation as well as phenotypic plasticity (relative distance plasticity index) in P. rigida leaf traits and litter flammability among populations grown in situ (population) and the same populations grown in a common garden or provenance study (provenance).Phenotypic and genotypic variation in fuel traits and litter flammability differed among source locations. Phenotypic plasticity in litter flammability among source locations were associated with fuel trait plasticity and biogeographic factors. Populations located in warmer and drier climates with presumably more frequent historical fire regimes were associated with greater plasticity in physical litter traits and their resulting flammability.Synthesis. Our study demonstrates the utility of common garden experiments to examine intraspecific variation and phenotypic plasticity in litter flammability. Our results indicate that litter flammability in Pinus rigida has the capacity for local adaptation. We hypothesize that intraspecific variation in plant flammability provides ecologically and evolutionary relevant information and that other frequent fire‐adaptive species will similarly demonstrate local adaptation in plant flammability. [ABSTRACT FROM AUTHOR]

Fire-dependent yellow pine (Pinus) forests are included within the temperate deciduous forest of eastern North America. These forests, which occupy dry slopes and typically contain xerophytic oaks (Quercus), have receded under fire suppression. Understanding historical fire regimes is essential for interpreting and managing these stands. To characterize fire history and vegetation dynamics, we conducted a dendroecological study of fire-scarred trees and age structure in pine stands at four sites in the Appalachian Mountains. Fire interval estimates suggest that before fire suppression began in the early to middle 1900s, fires occurred at approximately three- to eleven-year intervals. Short intervals were probably maintained in part by large-extent fires that spread from sparse ignition points. Fire frequency showed no long-term temporal trend (e.g., no wave of fire) from the middle 1700s through early 1900s despite land–use intensification, including industrial logging and associated wildfires during the late nineteenth and early twentieth centuries. Fire occurrence was associated with drought at two sites. Age–structure analyses evoke pyrogenic pine–oak communities that predated industrial disturbances and persisted under a regime of frequent, mixed-severity fires that was likely maintained through a positive feedback with the flammable vegetation. Competing species were established under more recent fire suppression, however, and are poised to replace the pines. [ABSTRACT FROM AUTHOR]

In this study, extractives from Pinus rigida heartwood (PRW), Eucalyptus camaldulensis var. obtusa aerial parts (ECL), and Eucalyptus flower buds (ECF) were used as additives in paper sheets produced from the pulp of linen fibers, and their effects on the mechanical and antifungal properties of the paper sheets were studied. The highest tensile and tear indices were 31.5 Nm/g, and 17.3 mNm2/g as pulp treated with PRW (4%), and ECL (1%), respectively. All the pulp additives yielded lower burst index values compared to the control (2.24 KPa.m2/g); the nearest value was 2.23 KPa.m2/g (ECL 4% pulp additive). The brightness percentages (ISO%) ranged from 65.7% to 70.2%, which were lower than the control treatment (70.3%). The paper sheets produced from pulp treated with 2% or 4% PRW, and with 4% ECL suppressed Aspergillus niger growth on the paper disc; pulp treated with 2% or 4% PRW, 4% ECL, and with 2% or 4% ECF completely suppressed A. terreus growth. However, all pulp extract additives did not inhibit the growth of Fusarium culmorum. [ABSTRACT FROM AUTHOR]

Wood samples of Pinus rigida , Juglans nigra , and Fagus sylvatica were superficially inoculated with three mold fungi ( Penicillium selerotigenum , Paecilomyces variotii , and Aspergillus niger ). The changes in wood surfaces and the elemental composition were observed by scan electron microscope (SEM) and the electron dispersive X-ray spectroscopy (EDX), respectively. Wood elemental composition was an indication of the growth of mold fungi, in which P. selerotigenum , and A. niger have consumed high amount of carbon (C) of F. sylvatica wood compared to control treatment. Also, P. selerotigenum consumed high amount of C of J. nigra wood compared to the control. While, the three mold fungi showed little changes in C content in P. rigida wood. The nitrogen element in the studied woods was completely consumed by the three mold fungi. Cl element increased in the three woods as inoculated by the three fungi compared to untreated woods. Other elements such as S, Si, Ca, Zn, Cu, and Fe varied in their content in accordance to the interaction among wood species and fungi. The growth of the three mold fungi showed distribution and structures of spores and hyphae covering deteriorated wood surfaces. The study suggests that the three mold fungi metabolize the carbon-rich constituents of the investigated wood species in a proportional manner and produce large fruiting structures that release vast numbers of spores in nature. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Variation in a species is a blend of adaptive, random, and migratory responses. Pitch pine (Pinus rigida), a highly variable eastern conifer, has occupied multiple glacial refugia, whose harsh conditions favored adaptations enhancing subsequent dispersal and recolonization of newly deglaciated sites. We assessed phenotypic diversity in long-term growth trials to elucidate both the adaptations and likely refugia. METHODS : Pitch pine progeny from 31 areas were grown in common gardens in six locations, from eastern Massachusetts to Korea. KEY RESULTS: Survival increased with source latitude, but seedlings from southern latitudes were tallest in the first (postplanting) year, but that advantage dissipated in later years. Progeny from northern latitudes were precocious, highly fecund, had smaller seeds, and more seeds per cone. Seed mass decreased with latitude in both parents and progeny. Serotinous cones were notably common in the New Jersey Pine Plains and Acadia National Park. Various disease agents and frost burn exhibited latitudinal trends that were nonlinear, with a break in the regression slope at about 40°N latitude. Cluster analysis identified both northern and southern groups, largely split between unglaciated and deglaciated terrain, but with Acadia and the Pine Plains as unique outliers. Within the southern group, provenances were organized into contiguous subgroups, but geographic structure was less evident in the northern group. CONCLUSIONS: The present range of pitch pine was colonized by migrants from at least three different refugia, including at least one on the exposed continental shelf during the Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

The Panther Knob Preserve is important in the Central Appalachians because it is the region's largest high-elevation pitch pine ( Pinus rigida) community, containing numerous rare and threatened plants and animals. Plant community structure and evidence of fire in 2008 were quantified to (a) document successional changes since 1985, and (b) test the hypothesis of pitch pine regeneration failure without recent fire. Diameter at breast height (dbh) of trees and percent cover of plants within 19 plots, each 20 × 20 m, were measured. Increment borings were used to estimate stand age, and evidence of fire, such as bark charring and soil charcoal, was recorded. Mineral soil from the top 10 cm was collected to evaluate the connection between soil characteristics and plant composition. Cluster analysis of percent cover values identified four plant community types. Diameter distributions, age structure, and the presence of only seven seedlings indicated little recent pine regeneration on the plateau. Comparisons with Fleming's (1985) observations showed that pines are taller but declined in percent cover, that ericaceous shrubs are denser, and that the threatened variable sedge, Carex polymorpha, has declined. Charred woody debris, fire scars, or soil charcoal occurred at 16 of 19 sites. Plant community structure, represented by nonmetric multidimensional scaling (NMS) ordination axes, was not correlated directly with the presence of fire evidence or soil mineral nutrients (principal components analysis [PCA] axes). A new conceptual model of pine dynamics on Panther Knob is introduced. Successional pathways with and without fire are discussed in the context of management. [ABSTRACT FROM AUTHOR]

In this study, coniferous (pitch pine,Pinus rigida) and broad-leaved (Oriental oak,Quercus variabilis) trees were gasified in a bubbling fluidized bed reactor, and the effects of reaction temperature and catalyst species on product yields and selectivities were systematically investigated. Upon increasing the gasification temperature from 800 to 900°C, the gas yield ofP. rigidamaintained similar values at 75.15–78.41%, while the gas yield ofQ. variabilisdecreased from 71.05 to 58.15% and the char and oil yields increased. The composition of gaseous products was affected according to catalyst species. When dolomite-based catalysts were used for fog biomass gasification, the hydrogen fraction increased substantially, while the carbon monoxide fraction decreased. [ABSTRACT FROM PUBLISHER]

Abstract: The essential oils of the leaves of three Pinus species (Pinus densiflora, P. thunbergii, P. rigida) were analyzed by gas chromatography/mass spectrometry (GC/MS). Analysis of the oils from P. densiflora, P. thunbergii and P. rigida revealed the presence of α-humulene (18.09%, 19.59%, 14.08%), caryophyllene (7.69%, 5.32%, 10.20%), β-pinene (4.95%, 4.45%, 7.39%), β-cadinene (3.28%, 1.30%, 3.71%), cinnamic acid (2.62%, 1.24%, 2.87%), α-terpinolene (2.10%, 0.51%, 0.3%), spathulenol (2.04%, 0.34%, 2.78%), α-cadinol (1.85%, 0.97%, 2.60%), caryophyllene oxide (1.82%, 0.23%, 0.13%) and α-pinene (1.79%, 0.68%, 0.13%) as major constituents. Essential oil from P. thunbergii showed stronger inhibitory activity against Bacillus subtilis, Bacillus natto, Staphylococcus aureus, Escherichia coli, Salmonella typhosa and Pseudomonas aeruginosa than the other two Pinus species, and essential oils of the three Pinus species showed strong antimicrobial activity against Salmonella enteritidis and P. aeruginosa. The essential oils from the three Pinus species also showed higher antimicrobial activity against Gram-negative bacteria than Gram-positive bacteria. Saccharomyces cerevisiae (yeast) was not inhibited by any essential oil. [Copyright &y& Elsevier]

Premise of the study: Fire in the New Jersey Pine Plains has selectively maintained a dwarf growth form of pitch pine (Pinus rigida), which is distinct from the surrounding tall forest of the Pine Barrens and has several other inherited adaptations that enable it to survive in an environment dominated by fire. Methods: Pitch pine progeny from two Pine Plains sites, the West and East Pine Plains, were grown in common garden environments with progeny from two Pine Barrens stands. Batsto and Great Egg Harbor River. The tests were replicated in five locations: in New Jersey, Connecticut, two sites in Massachusetts, and Korea. One of the tests was monitored for up to 36 yr. Key results: Progeny of Pine Plains origin were, in general, shorter, more crooked, precocious, bore more cones, had a higher frequency of serotinous cones, and had a higher frequency of stem cones than did Pine Barrens progeny, wherever they were grown. Conclusions: The Pine Plains is an ecotype that has evolved in response to disturbance. The several characters that distinguish it from the surrounding tall forest of the Pine Barrens are inherited. The dwarf stature and crooked form not only enable the ecotype to persist in an environment of frequent fires but also increase its flammability. [ABSTRACT FROM AUTHOR]

This study compared the antimicrobial activity and total phenolic content of three Pinus plants (Pinus densiflora, P. thunbergii, P. rigida) for the first time. The antimicrobial activity of the water fraction of methanol extract of fresh leaves was stronger than that of fallen leaves at any concentrations. The water fraction of crude methanol extract from fresh leaves of P. thunbergii showed a higher growth inhibitory activity against gram-positive and gram-negative bacteria than that of P. densiflora and P. rigida. The results from the disc diffusion method followed by measurements of minimal inhibition concentration (MIC) indicate that Bacillus subtilis was the most sensitive microorganism with the lowest MIC value. The highest total phenolic content was found in fresh leaves of P. rigida and P. thunbergii. The assay showed that the fresh leaves of the three Pinus plants contained higher total phenolic content than fallen leaves of the three plants. The antimicrobial activity was related with the total phenolic content. [ABSTRACT FROM AUTHOR]

We investigated the influence of historic fire on the development of pitch pine communities above 650 meters in northeastern West Virginia. We hypothesized that the fire frequency is correlated with species composition of existing pitch pine stands. Plant species composition was investigated in 31 study sites using 400 m² plots. Trees were cored and the presence of charred trees, soil charcoal, and other signs were used to create a fire evidence index (FEI). We measured annual ring widths, graphed radial growth patterns, and identified possible disturbance dates for each site when radial growth increased concurrently in least 2 trees per site within 5 years. We statistically analyzed plant community characteristics against evidence of disturbance using ANOVA and Pearson correlations. There was a significant relationship between FEI and tree community type (using relative density and relative basal area of trees > 7 cm in diameter) as well as plant community type (based on cluster analysis of percent cover of all species). We found a significant relationship between FEI and landform type (cliff, slope, plateau, bog). Possible disturbance dates were not significantly related to plant community or to the fire evidence index in this preliminary dataset. Although fire has played a role in shaping community composition, there are other environmental and anthropogenic factors influencing succession. Analysis of fire scars will be needed to pinpoint dates, locations, intensity, and frequency of fire to develop a greater understanding of the degree to which fire has influenced pine community development relative to other factors. [ABSTRACT FROM AUTHOR]

The successional diversity of basidiomycetous fungi was studied on Korean pine ( Pinus koraiensis) and pitch pine ( Pinus rigida) logs that were left exposed on the forest floor based on fungal surveys conducted after 18, 42, and 54 months of exposure. A total of 131 basidiomycetous isolates were recovered from the logs and grouped by their cultural morphology. Fungal identification was achieved by a BLAST search of partial nuclear large subunit ribosomal DNA sequences in GenBank. The results of the 18 month survey revealed that the isolation frequency and fungal diversity were higher for pitch pine than Korean pine. The dominant species found on Korean and pitch pine logs during the first survey were Hypochnicium karstenii and Phlebiopsis gigantea, respectively. In the 42 and 54 month surveys, the primary species were replaced by Hypochnicium eichleri, Phanerochaete velutina, Phlebia radiata, Rhizochaete sp., and Trametes versicolor. These results showed that decay fungi have host preference for woody materials that vary according to the species of tree being colonized. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this greenhouse experiment was to examine the short-term effects of competition between pine seedlings and the soil microbial biomass in sandy oligotrophic pine barrens upland forest soils subjected to varying levels of prescribed fire severity. Pine seedling growth performance, microbial biomass nitrogen, extractable soil nutrients and leaching loss from the soil were determined, throughout a single growing season following fire treatment. Replicate soil cores exposed to three levels of fire severity were maintained in a greenhouse with or without a pine seedling. Throughout the following growing season replicate cores from each treatment were harvested and analyzed monthly. The data allowed testing for two main effects: soil fire treatment and tree presence/absence. In no instance was a significant fire treatment X tree presence/absence interaction found. Our results indicate that biological activity strongly influences soil conditions. Reduced microbial activity resulted from the interaction of soil microbial biomass and an individual pine seedling. Increased plant growth performance correlates with reduced soil mineral nitrogen concentration and decreased pH. At the levels of fire severity utilized in this experiment immobilization due to biological uptake and abiotic soil fixation prevented significant leaching losses above that of unburned control samples. In the oligotrophic, pine barrens soils, nitrogen and phosphorus mineralized by fire are largely conserved by biological processes. These results also suggest that plant growth is subject to limitation by phosphorus availability in these soils. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

The influences of thinning (50% of standing density) and liming (Ca+Mg, 2 Mg ha−1) on soil chemical properties were investigated for 2 years (2001, 2002) in 40-year-old pitch pine ( Pinus rigida Mill.) and 44-year-old Japanese larch ( Larix leptolepis Gord.) plantations established on similar soils. In general, soil properties varied significantly among plantations and treatments. For both plantations, thinning significantly increased soil organic C (SOC) concentrations whereas there were no significant changes in soil pH and Ca and Mg concentrations. In addition, thinning increased total soil N and Na concentrations for the pitch pine plantation and available P concentration for the Japanese larch plantation in the second year after the treatment. Liming did not affect soil chemical characteristics for the pitch pine plantation except for Na concentration. However, for the Japanese larch plantation, liming significantly increased soil pH and K, Ca and Mg concentrations and decreased SOC and total soil N concentrations. For both plantations, soil Al concentration did not change after thinning and liming and decreased exponentially with increased pH values. The increases in SOC and total soil N concentrations after thinning were possibly due to increases in decomposition of organic matter and root death. Although differences were not statistically significant, soil available P concentration tended to increase at early stages of liming for both plantations. These results suggested that thinning and liming seemed to regulate soil chemical properties for pitch pine and Japanese larch plantations established on similar soils. [ABSTRACT FROM AUTHOR]

Abstract: 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 2h 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: , , ; and cations: , 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. [Copyright &y& Elsevier]

Invasion by pitch pine (Pinus rigida Mill.) on coastal plain pond shores may have direct impacts on the herbaceous community, or may merely indicate changes in hydroperiod, which are the actual cause of community change. We compared abiotic conditions and community composition of sites that had been invaded by P. rigida and those that had not on two Cape Cod ponds. Soil under living pines had lower pH and water content, reduced net nitrification, and increased rates of ammonification. Dense stands of pine saplings reduced PAR penetrance by 94% and excluded virtually all herbaceous species. To determine if pines alone can change community composition, we imposed artificial shade and added pine needle litter to experimental plots. In the course of one growing season, both litter and shade significantly reduced the frequency of herbs in the herbaceous zone of the pond shore. Litter had the greater effect (significant for six of seven taxa), while shade reduced the frequencies of three taxa significantly. [Copyright &y& Elsevier]

Young pitch pine seedlings are frequently subjected to prescribed burns in the New Jersey pine barrens as part of the management to eliminate fuel load in these forests, thereby reducing the risk of wildfire. The burns are relatively cool and release nutrients without killing the vegetation. Not all nutrients mineralized are immediately available to the plants, however. To determine factors that may contribute to nutrient release and to link this to availability of nutrients to plants following a fire in the pine barrens, a greenhouse study was conducted. The experimental design was a 3×2×2×3 factorial with three types of litter, high and low watering regime, burned and unburned litter, and three sample dates. Nitrogen, phosphorus, and potassium (through a rubidium analog) uptake rates were measured using natural isotope or radioisotope root bioassays. Though in the short time the experiment ran, neither an overall burned litter nor a litter quality effect was seen, high watering made P less available and K more available. N and K were the most available immediately following application of treatments, whereas P was not available until after 6 weeks following treatment application. Net mineralization of nitrogen, phosphorus, and potassium occurred in burned litter, whereas net immobilization of N and P occurred in highly watered, unburned litter. Since watering and timing were most influential in making nutrients available to seedlings following application of treatments in this greenhouse study, these factors may also be important in making nutrients available to mature trees in the New Jersey pine barrens. [Copyright &y& Elsevier]