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Atmospheric turbulent circulations in the vicinity of wildland fire fronts play an important role in the transfer of momentum into and out of combustion zones, which in turn can potentially affect the behavior and spread of wildland fires. The vertical turbulent transfer of momentum is accomplished via individual sweep, ejection, outward interaction, and inward interaction events, collectively known as sweep-ejection dynamics. This study examined the sweep-ejection dynamics that occurred before, during, and after the passage of a surface fire front during a prescribed fire experiment conducted in an open-canopied forest in the New Jersey Pine Barrens. High-frequency (10 Hz), tower-based, sonic anemometer measurements of horizontal and vertical wind velocity components in the vicinity of the fire front were used to assess the relative frequencies of occurrence of the different types of momentum-flux events, their contributions to the overall momentum fluxes, and their periodicity patterns. The observational results suggest that the presence of surface fire fronts in open-canopied forests can substantially change the sweep-ejection dynamics that typically occur when fires are not present. In particular, sweep events resulting in the downward transport of high horizontal momentum air from above were found to be more prominent during fire-front-passage periods.

This paper represents a study on the characterization of firebrand production which was carried out, using experimental fires conducted as prescribed fires in the New Jersey Pine Barrens, USA in March of 2013–2015. Several preliminary techniques were tested to characterize the firebrand production. Firebrands were collected from three plots for each year and analyzed for mass and size distribution. Thermal imagery was used to measure the velocity, size and number of firebrands in 2014 and 2015. The distribution of firebrands was evaluated in a monitored volume during the experiment. It was found that not less than 70% of collected particles were bark fragments and the rest were pine and shrub branches. The number of firebrands decreases with increasing the cross section area of firebrands. The mass of the particles varied from 5 to 50 mg, and the maximum number of the particles was observed for the mass range of 10–20 mg. About 80% of firebrands were particles with the cross section area of (5–20) × 10−5 m2. These results are consistent with the available observations of real fires [1] , [2] . Processing of infrared video showed that starting from a distance of 13 m from fire front, an increasing number of firebrands were observed in a controlled volume, increasing in number up to 180 per second. Relationships describing the time-variation of the number of particles that dropped on a 1.4 m2 surface and the number of particles that flew through a 1 m3 volume were obtained. Comparing the experimental and calculated data, we can conclude that these relationships allow us to describe the two numbers with an acceptable accuracy (adj. R2 0.74 and 0.86, respectively). In addition, the velocity of the particles, which depended on the wind velocity, was in the 0.1–10.5 m/s range, with an average value of 2.5 m/s.

Prescribed fires are conducted extensively in pine-dominated forests throughout the Eastern USA to reduce the risk of wildfires and maintain fire-adapted ecosystems. We asked how fire behavior and fuel consumption during prescribed fires are associated with turbulence and energy fluxes, which affect the dispersion of smoke and transport of firebrands, potentially impacting local communities and transportation corridors. We estimated fuel consumption and measured above-canopy turbulence and energy fluxes using eddy covariance during eight prescribed fires ranging in behavior from low-intensity backing fires to high-intensity head fires in pine-dominated forests of the New Jersey Pinelands, USA. Consumption was greatest for fine litter, intermediate for understory vegetation, and least for 1 + 10 hour wood, and was significantly correlated with pre-burn loading for all fuel types. Crown torching and canopy fuel consumption occurred only during high-intensity fires. Above-canopy air temperature, vertical wind velocity, and turbulent kinetic energy (TKE) in buoyant plumes above fires were enhanced up to 20.0, 3.9 and 4.1 times, respectively, compared to values measured simultaneously on control towers in unburned areas. When all prescribed fires were considered together, differences between above-canopy measurements in burn and control areas (&Delta, values) for maximum &Delta, air temperatures were significantly correlated with maximum &Delta, vertical wind velocities at all (10 Hz to 1 minute) integration times, and with &Delta, TKE. Maximum 10 minute averaged sensible heat fluxes measured above canopy were lower during low-intensity backing fires than for high-intensity head fires, averaging 1.8 MJ m&minus, 2 vs. 10.6 MJ m&minus, 2, respectively. Summed &Delta, sensible heat values averaged 70 &plusmn, 17%, and 112 &plusmn, 42% of convective heat flux estimated from fuel consumption for low-intensity and high-intensity fires, respectively. Surprisingly, there were only weak relationships between the consumption of surface and understory fuels and &Delta, air temperature, &Delta, wind velocities, or &Delta, TKE values in buoyant plumes. Overall, low-intensity fires were effective at reducing fuels on the forest floor, but less effective at consuming understory vegetation and ladder fuels, while high-intensity head fires resulted in greater consumption of ladder and canopy fuels but were also associated with large increases in turbulence and heat flux above the canopy. Our research quantifies some of the tradeoffs involved between fire behavior and turbulent transfer of smoke and firebrands during effective fuel reduction treatments and can assist wildland fire managers when planning and conducting prescribed fires.

Understanding processes underlying forest carbon dynamics is essential for accurately predicting the outcomes of non-stand-replacing disturbance in intermediate-age forests. We quantified net ecosystem production (NEP), aboveground net primary production (ANPP), and the dynamics of major carbon (C) pools before and during the decade following invasive insect defoliation and prescribed fires in oak- and pine-dominated stands in the New Jersey Pinelands National Reserve, USA. Gross ecosystem production (GEP) recovered during the year following defoliation at the oak stand, but tree mortality increased standing dead and coarse woody debris, and ecosystem respiration (Re) accounted for >97% of GEP. As a result, NEP averaged only 22% of pre-disturbance values during the decade following defoliation. At the pine stand, GEP also recovered to pre-disturbance values during the year following understory defoliation by gypsy moth and two prescribed fires, while Re was nearly unaffected. Overall, defoliation and tree mortality at the oak stand drove a decadal-scale reduction in NEP that was twofold greater in magnitude than C losses associated with prescribed fires at the pine stand. Our study documents the outcomes of different non-stand-replacing disturbances, and highlights the importance of detrital dynamics and increased Re in long-term measurements of forest C dynamics following disturbance in intermediate-age forests.

This study aims to develop a series of robust and efficient methodologies, which can be applied to understand and estimate firebrand generation and to evaluate firebrand showers close to a fire front. A field scale high intensity prescribed fire was conducted in the New Jersey Pine Barrens in March 2013. Vegetation was characterised with field and remotely sensed data, fire spread and intensity was characterised and meteorological conditions were monitored before and during the burn. Firebrands were collected from different locations in the forest and analysed for mass and size distribution. The majority were found to be bark slices (more than 70%) with substantial amounts of pine and shrub twigs. Shrub layer consumption was evaluated to supplement the firebrand generation study. Bark consumption was studied by measuring the circumference variation at several heights on each of three different pine trees. The variation was in the same order of magnitude as the bark thickness (1–5 mm). Testing and improving the protocol can facilitate the collection of compatible data in a wide range of ecosystems and fire environments, aiding in the development of solutions to prevent structural ignition at the Wildland Urban Interface.

Low-intensity wildland fires occurring beneath forest canopies can result in particularly adverse local air-quality conditions. Ambient and fire-induced turbulent circulations play a substantial role in the transport and dispersion of smoke during these fire events. Recent in situ measurements of fire–atmosphere interactions during low-intensity wildland fires have provided new insight into the structure of fire-induced turbulence regimes and how forest overstory vegetation can affect the horizontal and vertical dispersion of smoke. In this paper, we provide a summary of the key turbulence observations made during two low-intensity wildland fire events that occurred in the New Jersey Pine Barrens.

Prescribed burning is the major viable option that land managers have for reducing hazardous fuels and ensuring the regeneration of fire-dependent species in a cost-effective manner in Pine Barren ecosystems. Fuels management activities are directly linked to carbon (C) storage and rates of C sequestration by forests. To evaluate the effects of prescribed burning on forest C dynamics, we quantified consumption and accumulation of the forest floor and understory vegetation and measured net CO2 exchange in upland forest stands in the New Jersey Pinelands burned with prescribed fires. Prescribed fires released an average of 470 ± 137 g C m−2 from the litter layer and understory, equivalent to approximately 2–3 yr of sequestered C in undisturbed upland forests. Canopy and understory foliage averaged 85% of preburn periods, and CO2 uptake at near-full sunlight conditions averaged 79% of preburn levels during the following growing season. On an annual basis, stands lost C during the year of the burn, but releas...

Increased wildfires and temperatures due to climate change are expected to have profound effects on forest productivity and nitrogen (N) cycling. Forecasts about how wildfire and climate change will affect forests seldom consider N availability, which may limit forest response to climate change, particularly in fire-prone landscapes. The overall objective of this study was to examine how wildfire and climate change affect long-term mineral N availability in a fire-prone landscape. We employed a commonly used landscape simulation model (LANDIS-II) in the New Jersey Pine Barrens, a landscape characterized by frequent small fires and fire-resilient vegetation. We found that fire had little effect on mineral N, whereas climate change and fire together reduced mineral N by the end of the century. Though N initially limited forest productivity, mineral N was no longer limiting after 50 years. Our results suggest that mineral N is resilient to fire under our current climate but not under climate change. Also, predictions that do not consider N limitation may underestimate short-term but not long-term productivity responses to climate change. Together these results illustrate the importance of including N dynamics when simulating the effects of climate change on forest productivity, particularly in fire-prone regions such as the New Jersey Pine Barrens.

Smoke prediction products are one of the tools used by land management personnel for decision making regarding prescribed fires. This study documents the application to a prescribed fire of a smoke prediction system that employs ARPS-CANOPY, a modified version of the Advanced Regional Prediction System (ARPS) model containing a canopy submodel, as the meteorological driver. In this paper, the performance of ARPS-CANOPY in simulating meteorological fields in the vicinity of a low-intensity fire is assessed using flux-tower data collected prior to and during a low-intensity prescribed fire in the New Jersey Pine Barrens in March 2011. A three-dimensional high-resolution plant area density dataset is utilized to define the characteristics of the canopy, and the fire is represented in ARPS-CANOPY as a heat flux to the atmosphere. The standard ARPS model is compared with reanalysis and upper-air data to establish that the model can simulate the observed synoptic-mesoscale and planetary boundary layer features that are salient to this study. ARPS-CANOPY profiles of mean turbulent kinetic energy, wind speed/direction, and temperature exhibit patterns that appear in the flux-tower observations during both the preburn phase of the experiment and the period of time the flux tower experienced perturbed atmospheric conditions due to the impinging fire. Last, the character and source of turbulence in and around the fire line are examined. These results are encouraging for smoke prediction efforts since transport of smoke from low-intensity fires is highly sensitive to the near-surface meteorological conditions and, in particular, turbulent flows.

[1] Seasonal variation in photosynthetic capacity is an important part of the overall seasonal variability of temperate deciduous forests. However, it has only recently been introduced in a few terrestrial biosphere models, and many models still do not include it. The biases that result from this omission are not well understood. In this study, we use the Ecosystem Demography 2 model to simulate an oak-dominated stand in the New Jersey Pine Barrens. Two alternative model configurations are presented, one with seasonal variation of photosynthetic capacity (SPC-ON) and one without seasonal variation of photosynthetic capacity (SPC-OFF). Under typical climate conditions, the two configurations simulate values of monthly gross primary productivity (GPP) as different as 0.05 kg C m−2 month−1 in the early summer and 0.04 kg C m−2 month−1 in the fall. The differences between SPC-ON and SPC-OFF are amplified when there is temporal correlation between photosynthetic capacity and climate anomalies or disturbances. Warmer spring temperatures enhance GPP in SPC-ON more than in SPC-OFF, but warmer fall temperatures enhance GPP in SPC-OFF more than in SPC-ON. Defoliation by gypsy moth, a class of disturbance that typically happens in late spring in the New Jersey Pine Barrens, has a disproportionately negative impact on GPP in SPC-ON. It is concluded that including seasonal variation of photosynthetic capacity in models will improve simulations of monthly scale ecosystem functioning as well as of longer-term responses to climate change and disturbances.

Hydrologic variability during 2005-2011 was observed and analyzed at an upland oak/pine forest in the New Jersey Pinelands. The forest experienced defoliation by Gypsy moth (Lymantria dispar L.) in 2007, drought conditions in 2006 and a more severe drought in 2010. By using sap flux and eddy covariance measurements, stream discharge data from USGS, soil water changes, precipitation (P) and precipitation throughfall, a local water balance was derived.

a b s t r a c t We used eddy covariance and meteorological measurements to quantify energy exchange and evapotran- spiration (Et) in three representative upland forest stands in the New Jersey Pinelands that were either defoliated by gypsy moth (Lymantria dispar L.) or burned in prescribed fires during the study period. Latent (�E) and sensible heat (H) fluxes were linear functions of available energy, and seasonality had a major effect on the partitioning of available energy intoE and H at each stand. Both defoliation and prescribed fire reduced leaf area, altered the partitioning of available energy, and reducedE flux com- pared to undisturbed periods. Summer daily Et averaged 4.2 ± 1.5, 3.3 ± 1.2 and 3.9 ± 1.3 mm day−1 at the oak-, mixed, and pine-dominated stands during undisturbed periods, but only 2.4 ± 0.9 mm day −1 during defoliation at the oak stand in 2007, and 2.4 ± 0.9 and 3.2 ± 0.9 mm day−1 following spring fires at the mixed and pine-dominated stands, respectively. For all years measured, seasonal maximum leaf area index (LAI) explained 82% of the variability in daily Et during the summer at the oak stand, and 80% of the variability at the mixed and pine-dominated stands. Annual Et averaged 614, 493, and 683 mm yr −1 at the oak, mixed, and pine stands, respectively. When averaged across all stands and years, annual Et was 606 mm yr−1, ca. 53.6% of incident precipitation, and similar to long-term averages reported in

A major challenge in modeling the carbon dynamics of vegetation communities is the proper parameterization and calibration of eco-physiological variables that are critical determinants of the ecosystem process-based model behavior. In this study, we improved and calibrated a biochemical process-based WxBGC model by using in situ AmeriFlux eddy covariance tower observations. We simulated carbon dynamics of fire-dominated forests at tower sites and upscaled the tower site-based simulations to regional scale for the New Jersey Pinelands using LANDSAT-ETM land cover and DAYMET climate data. The Extended Fourier Amplitude Sensitivity Test approach was used to assess the higher-order sensitivity of model to critical eco-physiological parameters. The model predictions of CO2 net ecosystem exchange (NEE) and gross ecosystem production (GEP) were in agreement with the eddy covariance measurements at the three tower sites in 2005. However, the model showed poor fit in 2006, grossly overestimating NEE and the ratio of ecosystem respiration to GEP because the model did not reflect the carbon loss caused by severe defoliation related to an outbreak of gypsy moths in that year. The model simulations indicated that wildfire reduced annual NEE in pine/scrub oak forest, while prescribed burning in oak/pine and pine/oak stands led to temporary increase in NEE for a period 1-2 years post burning. The uncertainty and sensitivity of the model carbon simulations were mainly attributable to the 2nd- and higher-order interactions between carbon allocation parameters, specific leaf area and fire mortality intensity.

The New Jersey Pine Barrens (NJPB) is the largest forested area along the northeastern coast of the United States. The NJPB are dominated by pine (Pinus spp.) and oak (Quercus spp.) stands that are fragmented and subject to frequent disturbance and forest management. Over long time periods (>50 years), the balance between oak and pine dominance is determined by fire frequency. As a consequence, the ability of the NJPB to sequester carbon may be contingent upon management activities as well as patterns of historic land use. We simulated 100 years of carbon change using three scenarios: (1) contemporary management as reflected in the recent (1991‐2006) fire records, (2) an increase in the fire ignitions within the wildland urban interface areas of the NJPB reflecting increased prescribed fires, and (3) a longer response time to wildfires, reflecting a more liberal burning policy by the New Jersey Forest Fire Service. We used the LANDIS-II model coupled with CENTURY and the Dynamic Fire and Dynamic Biomass Fuels extensions to estimate forest carbon sequestration based on these three scenarios. Calibration and validation via comparison to monthly flux tower data indicated that the model reasonably captured the timing and magnitude of net ecosystem exchange in the absence of Gypsy moth defoliation (r 2 = 0.89). Under all scenarios, our simulations suggest that forests of the NJPB will continue to accumulate carbon over the next 100 years under current climatic conditions. Although aboveground net primary productivity, live carbon, and detrital carbon were roughly constant or increased only modestly, soil organic carbon continued to increase through time for all forest types except the highly xeric pine plains. Our simulated changes in management reflected only minor alterations to the fire regime and thus management may have only minor effects on total forest carbon budgets in the immediate future particularly when compared to recovery from historic disturbance patterns.

Disturbances 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. 1240gCm � 2 a � 1 ). Overall, net primary production (NPP) in 2007 was approximately 240gCm � 2 a � 1 (vs. 250gCm � 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. 57gCm � 2 a � 1 in 2006 and 2007, respectively). The overall impact of the defoliation spanned 21% of upland forests (320km 2 ) 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 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 � 204gCm � 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, 1103, and � 161gCm � 2 yr � 1 in 2006, and 1293, 1129, and � 17gCm � 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 oakdominated 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.

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.

We used a single-beam, first return profiling LIDAR (Light Detection and Ranging) measurements of canopy height, intensive biometric measurements in plots, and Forest Inventory and Analysis (FIA) data to quantify forest structure and ladder fuels (defined as vertical fuel continuity between the understory and canopy) in the New Jersey Pinelands. The LIDAR data were recorded at 400 Hz over three intensive areas of 1 km 2 where transects were spaced at 200 m, and along 64 transects spaced 1 km apart (total of ca. 2500 km 2 ). LIDAR and field measurements of canopy height were similar in the three intensive study areas, with the 80th percentile of LIDAR returns explaining the greatest amount of variability (79%). Correlations between LIDAR data and aboveground tree biomass measured in the field were highly significant when all three 1k m 2 areas were analyzed collectively, with the 80th percentile again explaining the greatest amount of variability (74%). However, when intensive areas were analyzed separately, correlations were poor for Oak/Pine and Pine/Scrub Oak stands. Similar results were obtained using FIA data; at the landscape scale, mean canopy height was positively correlated with aboveground tree biomass, but when forest types were analyzed separately, correlations were significant only for some wetland forests (Pitch Pine lowlands and mixed hardwoods; r 2 =0.74 and 0.59, respectively), and correlations were poor for upland forests (Oak/Pine, Pine/Oak and Pine/Scrub Oak, r 2 =0.33, 0.11 and 0.21, respectively). When LIDAR data were binned into 1-m height classes, more LIDAR pulses were recorded from the lowest height classes in stands with greater shrub biomass, and significant differences were detected between stands where recent prescribed fire treatments had been conducted and unburned areas. Our research indicates that single-beam LIDAR can be used for regional-scale (forest biomass) estimates, but that relationships between height and biomass can be poorer at finer scales within individual forest types. Binned data are useful for estimating the presence of ladder fuels (vertical continuity of leaves and branches) and horizontal fuel continuity below the canopy. © 2007 Published by Elsevier Inc.

Pine-oak ecosystems are globally distributed even though differences in anatomy and leaf habit between many co-occurring oaks and pines suggest different strategies for resource use, efficiency and stomatal behavior. The New Jersey Pinelands contain sandy soils with low water- and nutrient-holding capacity providing an opportunity to examine trade-offs in resource uptake and efficiency. Therefore, we compared resource use in terms of transpiration rates and leaf nitrogen content and resource-use efficiency including water-use efficiency (WUE) via gas exchange and leaf carbon isotopes and photosynthetic nitrogen-use efficiency (PNUE) between oaks (Quercus alba, Q. prinus, Q. velutina) and pines (Pinus rigida, P. echinata). We also determined environmental drivers (vapor pressure deficit (VPD), soil moisture, solar radiation) of canopy stomatal conductance (GS) estimated via sap flow and stomatal sensitivity to light and soil moisture. Net assimilation rates were similar between genera, but oak leaves used about 10% more water and pine foliage contained about 20% more N per unit leaf area. Therefore, oaks exhibited greater PNUE while pines had higher WUE based on gas exchange, although WUE from carbon isotopes was not significantly different. For the environmental drivers of GS, oaks had about 10% lower stomatal sensitivity to VPD normalized by reference stomatal conductance compared with pines. Pines exhibited a significant positive relationship between shallow soil moisture and GS, but only GS in Q. velutina was positively related to soil moisture. In contrast, stomatal sensitivity to VPD was significantly related to solar radiation in all oak species but only pines at one site. Therefore, oaks rely more heavily on groundwater resources but have lower WUE, while pines have larger leaf areas and nitrogen acquisition but lower PNUE demonstrating a trade-off between using water and nitrogen efficiently in a resource-limited ecosystem.

In this chapter, we document the development and current research efforts of the fire research program at the Silas Little Experimental Forest of the Northern Research Station, USDA Forest Service, in the Pinelands of southern New Jersey. The 450,000-ha (1.1 million-acre) Pinelands National Reserve contains some of the most challenging fuel types for wildland fire managers in the eastern USA. These highly flammable forests occur adjacent to extensive wildland–urban interface and major transportation corridors. We first briefly discuss the ecological setting of upland forests in the Pinelands, highlighting how fire, past industrialization, and other disturbances have shaped the composition and structure of these forests. We then document the establishment of the Experimental Forest and the fire research program. We focus on the career of Dr. Silas Little, a silviculturist with the Northeastern Forest Experiment Station, Upper Darby, PA. Beginning in the late 1930s, his research on prescribed burning practices and silviculture in the Pinelands resulted in cost-effective methods to reduce wildfire risk while promoting the regeneration of commercially important timber species. We discuss how many of the prescribed burning practices developed during these research efforts are now used operationally by the New Jersey Forest Fire Service (NJFFS) and federal wildland fire managers in the Pinelands. Finally, we highlight current and future research efforts at the Experimental Forest.

Disturbance regimes within temperate forests can significantly impact carbon cycling. Additionally, projected climate change in combination with multiple, interacting disturbance effects may disrupt the capacity of forests to act as carbon sinks at large spatial and temporal scales. We used a spatially explicit forest succession and disturbance model, LANDIS-II, to model the effects of climate change, gypsy moth (Lymantria dispar L.) defoliation, and wildfire on the C dynamics of the forests of the New Jersey Pine Barrens over the next century. Climate scenarios were simulated using current climate conditions (baseline), as well as a high emissions scenario (HadCM3 A2 emissions scenario). Our results suggest that long-term changes in C cycling will be driven more by climate change than by fire or gypsy moths over the next century. We also found that simulated disturbances will affect species composition more than tree growth or C sequestration rates at the landscape level. Projected changes in tree species biomass indicate a potential increase in oaks with climate change and gypsy moth defoliation over the course of the 100-year simulation, exacerbating current successional trends towards increased oak abundance. Our research suggests that defoliation under climate change may play a critical role in increasing the variability of tree growth rates and in determining landscape species composition over the next 100 years.

This study is to predict fire spread behavior and burned area across two fire-prone landscapes with contrasting vegetation (Oak-dominated ecosystem in WI vs. pine-dominated ecosystem in NJ), fuel-type composition, and land-use history regulated by the effects of weather, landscape structure and land management by combining simulations from three models (FARSITE, HARVEST, AND FRAGSTATS) under different scenarios. The results demonstrate:\1- substantial differences in fire-spread patterns between the two landscapes were observed when holding weather conditions constant and excluding roads, indicating that landscape fragmentation is a main controlling factor on fire spread at the landscape level; ➁ roads functioning as barriers could significantly reduce the burned area from fire spread; and ➂ Harvesting effects showed different trends, depending on landscape fuel type composition and weather conditions. At 4% harvesting intensity, both clustered and dispersed methods showed no significant impact (a=0.01) on reducing the mean burned area across the more fragmented WI landscape, but showed significant effects on fire spread in the less fragmented NJ landscape in summer when weather was hot and dry.

Evapotranspiration (ET) was monitored above a wetland forest canopy dominated by pitch-pine in the New Jersey Pinelands during November 10, 2004�February 20, 2007, using an eddy-covariance method. Twelve-month ET totals ranged from 786 to 821 millimeters (mm). Minimum and maximum ET rates occurred during December�February and in July, respectively. Relations between ET and several environmental variables (incoming solar radiation, air temperature, relative humidity, soil moisture, and net radiation) were explored. Net radiation (r = 0.72) and air temperature (r = 0.73) were the dominant explanatory variables for daily ET. Air temperature was the dominant control on evaporative fraction with relatively more radiant energy used for ET at higher temperatures. Soil moisture was shown to limit ET during extended dry periods. With volumetric soil moisture below a threshold of about 0.15, the evaporative fraction decreased until rain ended the dry period, and the evaporative fraction sharply recovered. A modified Hargreaves ET model, requiring only easily obtainable daily temperature data, was shown to be effective at simulating measured ET values and has the potential for estimating historical or real-time ET at the wetland site. The average annual ET measured at the wetland site during 2005�06 (801 mm/yr) is about 32 percent higher than previously reported ET for three nearby upland sites during 2005�09. Periodic disturbance by fire and insect defoliation at the upland sites reduced ET. When only undisturbed periods were considered, the wetland ET was 17 percent higher than the undisturbed upland ET. Interannual variability in wetlands ET may be lower than that of uplands ET because the upland stands are more susceptible to periodic drought conditions, disturbance by fire, and insect defoliation. Precipitation during the study period at the nearby Indian Mills weather station was slightly higher than the long-term (1902�2011) annual mean of 1,173 millimeters (mm), with 1,325 and 1,396 mm of precipitation in 2005 and 2006, respectively.

Many temperate and boreal forests are subject to insect epidemics. In the eastern US, over 41 million meters squared of tree basal area are thought to be at risk of gypsy moth defoliation. However, the decadal-to-century scale implications of defoliation events for ecosystem carbon dynamics are not well understood. In this study, the effects of defoliation intensity, periodicity and spatial pattern on the carbon cycle are investigated in a set of idealized model simulations. A mechanistic terrestrial biosphere model, ecosystem demography model 2, is driven with observations from a xeric oak‐pine forest located in the New Jersey Pine Barrens. Simulations indicate that net ecosystem productivity (equal to photosynthesis minus respiration) decreases linearly with increasing defoliation intensity. However, because of interactions between defoliation and drought effects, aboveground biomass exhibits a nonlinear decrease with increasing defoliation intensity. The ecosystem responds strongly with both reduced productivity and biomass loss when defoliation periodicity varies from 5 to 15 yr, but exhibits a relatively weak response when defoliation periodicity varies from 15 to 60 yr. Simulations of spatially heterogeneous defoliation resulted in markedly smaller carbon stocks than simulations with spatially homogeneous defoliation. These results show that gypsy moth defoliation has a large effect on oak‐pine forest biomass dynamics, functioning and its capacity to act as a carbon sink.

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.