Survival and growth of upland oak and co-occurring competitor seedlings following single and repeated prescribed fires

Studies within and outside the U.S. indicate recurring oak (Quercus spp.) regeneration problems. In deciduous forests of the eastern U.S., a prevailing explanation for this trend is fire suppression leading to high competitor abundance and low understory light. In response, prescribed fire is increasingly used as a management tool to remedy these conditions and encourage future oak establishment and growth. Within eastern Kentucky, we implemented single and repeated (3×) prescribed fires over a 6-yr period (2002–2007). Pre- and post-burn, we quantified canopy cover and oak seedling survival and growth compared to other woody seedlings deemed potential competitors, primarily red maple (Acer rubrum L.) and sassafras (Sassafras albidum (Nutt.) Nees.). Burning temporarily decreased canopy cover 3–10%, but cover rebounded the subsequent growing season. Repeated burning ultimately produced canopy cover about 6% lower than sites unburned and burned once, suggesting a cumulative effect on understory light. Red maple exhibited low survival (∼40%) following single and repeated burns, but growth remained similar to unburned seedlings. Burning had little impact on sassafras survival and led to total height and basal diameters 2× greater than unburned seedlings. A single burn had no impact on red oak (Erythrobalanus spp.) survival and increased height and basal diameters 25–30%, but this positive growth response was driven by seedlings on several plots which experienced high burn temperatures and consequently high overstory mortality. White oaks (Leucobalanus spp.), however, exhibited twice as high mortality compared to those unburned, with no change in growth parameters. Repeated burning negatively impacted survival and growth of both oak groups compared to unburned seedlings. With both burn regimes, oaks with smaller pre-burn basal diameters exhibited the lowest post-burn survival. Thus, despite the ability of prescribed burns to temporarily increase understory light and reduce red maple survival, neither single or repeated burns placed oaks in an improved competitive position. These findings result from a combination of highly variable yet interdependent factors including the (1) life history traits of oaks compared to their co-occurring competitors, (2) pre-burn stature of pre-existing oak seedlings, and (3) variability in fire temperature and effects on understory light.     

Response of antelope bitterbrush to repeated prescribed burning in Central Oregon ponderosa pine forests

Antelope bitterbrush is a dominant shrub in many interior ponderosa pine forests in the western United States. How it responds to prescribed fire is not well understood, yet is of considerable concern to wildlife and fire managers alike given its importance as a browse species and as a ladder fuel in these fire-prone forests. We quantified bitterbrush cover, density, and biomass in response to repeated burning in thinned ponderosa pine forests. Low- to moderate-intensity spring burning killed the majority of bitterbrush plants on replicate plots. Moderately rapid recovery of bitterbrush density and cover resulted from seedling recruitment plus limited basal sprouting. Repeated burning after 11 years impeded the recovery of the bitterbrush community. Post-fire seed germination following the repeated burns was 3–14-fold lower compared to the germination rate after the initial burns, while basal sprouting remained fairly minor. After 15 years, bitterbrush cover was 75–92% lower on repeated-burned compared to unburned plots. Only where localized tree mortality resulted in an open stand was bitterbrush recovery robust. By controlling bitterbrush abundance, repeated burning eliminated the potential for wildfire spread when simulated using a customized fire behavior model. The results suggest that repeated burning is a successful method to reduce the long-term fire risk imposed by bitterbrush as an understory ladder fuel in thinned pine stands. Balancing the need to limit fire risk yet provide adequate bitterbrush habitat for wildlife browse will likely require a mosaic pattern of burning at the landscape scale or a burning frequency well beyond 11 years to allow a bitterbrush seed crop to develop.     

Eight years of seasonal burning and herbicidal brush control influence sapling longleaf pine growth,understory vegetation,and the outcome of an ensuing wildfire

To study how fire or herbicide use influences longleaf pine (Pinus palustris Mill.) overstory and understory vegetation, five treatments were initiated in a 5–6-year-old longleaf pine stand: check, biennial arborescent plant control by directed herbicide application, and biennial burning in March, May, or July. The herbicide or prescribed fire treatments were applied in 1999, 2001, 2003, and 2005. All prescribed fires were intense and averaged 700 kJ/s/m of fire front across all 12 burns. Using pretreatment variables as covariates, longleaf pine survival and volume per hectare were significantly less on the three prescribed fire treatments than on checks. Least-square means in 2006 for survival were 70, 65, 64, 58, and 56% and volume per hectare was 129, 125, 65, 84, and 80 m³/ha on the check, herbicide, March-, May-, and July-burn treatments, respectively. A wildfire in March 2007 disproportionately killed pine trees on the study plots. In October 2007, pine volume per hectare was 85, 111, 68, 98, and 93 m³/ha and survival was 32, 41, 53, 57, and 55% on the check, herbicide, March-, May-, and July-burn treatments, respectively, after dropping trees that died through January 2009 from the database. Understory plant cover was also affected by treatment and the ensuing wildfire. In September 2006, herbaceous plant cover averaged 4% on the two unburned treatments and 42% on the three prescribed fire treatments. Seven months after the wildfire, herbaceous plant cover averaged 42% on the two previously unburned treatments and 50% on the three prescribed fire treatments. Before the wildfire, understory tree cover was significantly greater on checks (15%) than on the other four treatments (1.3%), but understory tree cover was similar across all five treatments 7 months after the wildfire averaging 1.1%. The greater apparent intensity of the wildfire on the previously unburned treatments most likely resulted from a greater accumulation of fuels on the check and herbicide plots that also collectively had a higher caloric content than fuels on the biennially prescribed burned plots. These results showed the destructive force of wildfire to overstory trees in unburned longleaf pine stands while also demonstrating the rejuvenating effects of wildfire within herbaceous plant communities. They caution for careful reintroduction of prescribed fire even if fire was excluded for less than a decade.     

Prescribed fire effects on bark beetle activity and tree mortality in southwestern ponderosa pine forests

Prescribed fire is an important tool in the management of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests, yet effects on bark beetle (Coleoptera: Curculionidae, Scolytinae) activity and tree mortality are poorly understood in the southwestern U.S. We compared bark beetle attacks and tree mortality between paired prescribed-burned and unburned stands at each of four sites in Arizona and New Mexico for three growing seasons after burning (2004–2006). Prescribed burns increased bark beetle attacks on ponderosa pine over the first three post-fire years from 1.5 to 13% of all trees, increased successful, lethal attacks on ponderosa pine from 0.4 to 7.6%, increased mortality of ponderosa pine from all causes from 0.6 to 8.4%, and increased mortality of all tree species with diameter at breast height >13 cm from 0.6 to 9.6%. On a per year basis, prescribed burns increased ponderosa pine mortality from 0.2% per year in unburned stands to 2.8% per year in burned stands. Mortality of ponderosa pine 3 years after burning was best described by a logistic regression model with total crown damage (crown scorch + crown consumption) and bark beetle attack rating (no, partial, or mass attack by bark beetles) as independent variables. Attacks by Dendroctonus spp. did not differ significantly over bole heights, whereas attacks by Ips spp. were greater on the upper bole compared with the lower bole. Three previously published logistic regression models of tree mortality, developed from fires in 1995–1996 in northern Arizona, were moderately successful in predicting broad patterns of tree mortality in our data. The influence of bark beetle attack rating on tree mortality was stronger for our data than for data from the 1995–1996 fires. Our results highlight canopy damage from fire as a strong and consistent predictor of post-fire mortality of ponderosa pine, and bark beetle attacks and bole char rating as less consistent predictors because of temporal variability in their relationship to mortality. The small increase in tree mortality and bark beetle attacks caused by prescribed burning should be acceptable to many forest managers and the public given the resulting reduction in surface fuel and risk of severe wildfire.     

A comparison of soil properties after contemporary wildfire and fire suppression

Forests that were subject to frequent wildfires, such as ponderosa pine/Douglas-fir forests, had fire-return intervals of approximately 6–24 years. However, fire suppression over the last century has increased the fire-return interval by a factor of 5 in these forests, possibly resulting in changes to the soil. The objective of this study was to determine if soils of recently burned areas (representative of the natural fire-return interval) have different properties relative to soils in areas without recent fire. To assess this, recent low-intensity, lightning-caused, spot wildfire areas were located within fire-suppressed stands of ponderosa pine/Douglas-fir of the central, eastern Cascade Mountains of Washington State. Soil horizon depths were measured, and samples collected by major genetic horizons. Samples were analyzed for pH, C, N, C/N ratio, cation exchange capacity (CEC), base saturation (%BS), hydrophobicity and extractable P. Results show very little difference in soil properties between sites burned by low-severity fires and those areas left unburned. Such minimal changes, from these low-severity fires, in soil properties from fire suppression suggest there has also been little change in soil processes.     

Thinning and chipping small-diameter ponderosa pine changes understory plant communities on the Colorado Front Range

Novel fire mitigation treatments that chip harvested biomass on site are increasingly prescribed to reduce the density of small-diameter trees, yet the ecological effects of these treatments are unknown. Our objective was to investigate the impacts of mechanical thinning and whole tree chipping on Pinus ponderosa (ponderosa pine) regeneration and understory plant communities to guide applications of these new fuel disposal methods. We sampled in three treatments: (1) unthinned forests (control), (2) thinned forests with harvested biomass removed (thin-only), and (3) thinned forests with harvested biomass chipped and broadcast on site (thin + chip). Plots were located in a ponderosa pine forest of Colorado and vegetation was sampled three to five growing seasons following treatment. Forest litter depth, augmented with chipped biomass, had a negative relationship with cover of understory plant species. In situ chipping often produces a mosaic of chipped patches tens of meters in size, creating a range of woodchip depths including areas lacking woodchip cover within thinned and chipped forest stands. Thin-only and thin + chip treatments had similar overall abundance and species richness of understory plants at the stand scale, but at smaller spatial scales, areas within thin + chip treatments that were free of woodchip cover had an increased abundance of understory vegetation compared to all other areas sampled. Relative cover of non-native plant species was significantly higher in the thin-only treatments compared to control and thin + chip areas. Thin + chip treated forests also had a significantly different understory plant community composition compared to control or thin-only treatments, including an increased richness of rhizomatous plant species. We suggest that thinning followed by either chipping or removing the harvested biomass could alter understory plant species composition in ponderosa pine forests of Colorado. When considering post-treatment responses, managers should be particularly aware of both the depth and the distribution of chipped biomass that is left in forested landscapes.     

Yellow pine regeneration as a function of fire severity and post-burn stand structure in the southern Appalachian Mountains

We used pre- and post-burn fire effects data from six prescribed burns to examine post-burn threshold effects of stand structure (understory density, overstory density, shrub cover, duff depth, and total fuel load) on the regeneration of yellow pine (Pinus subgenus Diploxylon) seedlings and cover of herbaceous vegetation in six prescribed-fire management units located within western Great Smoky Mountains National Park (GSMNP) in east Tennessee, USA. We also evaluated the utility of the Keetch-Byram Drought Index (KBDI) as a predictor of post-burn stand and fuel conditions by comparing post-burn stand variables for different ranges of KBDI (23-78; more wet, and 328-368; more dry). We found that yellow pine seedlings were effectively absent in post-burn forests until overstory density was reduced over 40%, understory density was reduced over 80%, and post-burn shrub cover was 10% or less. We also observed that a reduction in total fuels of 60% and a post-burn duff layer depth of less than four cm were required for successful regeneration of yellow pine. Total herbaceous species cover exhibited near identical responses with increased cover following an 80% reduction in understory density and a post-burn duff depth of less than 4 cm. We observed strong positive relationships between high KBDI values and burn severity, changes in forest structure, reductions in fuels, and post-burn yellow pine reproduction. We observed continuous recruitment of yellow pine seedlings 5 years after fire in high KBDI burns while low KBDI burns showed little change in yellow pine density through time. An intense outbreak of the southern pine beetle (SPB; Dendroctonus frontalis) occurred within 2 years of our high KBDI burns and reduced shading resulting from overstory mortality likely enhanced the survival of yellow pine seedlings. The results of this study provide targets for the application of prescribed fire to restore yellow pine in the southern Appalachians. Continued research and monitoring will help determine how prescribed fire can best be applied in combination with other disturbance agents such as SPB to perpetuate yellow pine forests.     

Prescribed fires as ecological surrogates for wildfires: A stream and riparian perspective

Forest managers use prescribed fire to reduce wildfire risk and to provide resource benefits, yet little information is available on whether prescribed fires can function as ecological surrogates for wildfire in fire-prone landscapes. Information on impacts and benefits of this management tool on stream and riparian ecosystems is particularly lacking. We used a beyond-BACI (Before, After, Control, Impact) design to investigate the effects of a prescribed fire on a stream ecosystem and compared these findings to similar data collected after wildfire. For 3 years after prescribed fire treatment, we found no detectable changes in periphyton, macroinvertebrates, amphibians, fish, and riparian and stream habitats compared to data collected over the same time period in four unburned reference streams. Based on changes in fuels, plant and litter cover, and tree scorching, this prescribed fire was typical of those being implemented in ponderosa pine forests throughout the western U.S. However, we found that the extent and severity of riparian vegetation burned was substantially lower after prescribed fire compared to nearby wildfires. The early-season prescribed fire did not mimic the riparian or in-stream ecological effects observed following a nearby wildfire, even in catchments with burn extents similar to the prescribed fire. Little information exists on the effects of long-term fire exclusion from riparian forests, but a “prescribed fire regime” of repeatedly burning upland forests while excluding fire in adjacent riparian forests may eliminate an important natural disturbance from riparian and stream habitats.     

Structure and composition changes following restoration treatments of longleaf pine forests on the Gulf Coastal Plain of Alabama

Longleaf pine (Pinus palustris Mill.) forests of the Gulf Coastal Plain historically burned every 2–4 years with low intensity fires, which maintained open stands with herbaceous dominated understories. During the early and mid 20th century however, reduced fire frequency allowed fuel to accumulate and hardwoods to increase in the midstory and overstory layers, while woody shrubs gained understory dominance. In 2001, a research study was installed in southern Alabama to develop management options that could be used to reduce fuel loads and restore the ecosystem. As part of a nationwide fire and fire surrogates study, treatments included a control (no fire or other disturbance), prescribed burning only, thinning of selected trees, thinning plus prescribed burning, and herbicide plus prescribed burning. After two cycles of prescribed burning, applied biennially during the growing season, there were positive changes in ecosystem composition. Although thinning treatments produced revenue, while reducing midstory hardwoods and encouraging growth of a grassy understory, burning was needed to discourage regrowth of the hardwood midstory and woody understory. Herbicide application followed by burning gave the quickest changes in understory composition, but repeated applications of fire eventually produced the same results at the end of this 8-year study. Burning was found to be a critical component of any restoration treatment for longleaf communities of this region with positive changes in overstory, midstory and understory layers after just three or four burns applied every 2 or 3 years.     

Woodland salamander response to two prescribed fires in the central Appalachians

Using coverboard arrays, we monitored woodland salamanders on the Fernow Experimental Forest in the central Appalachian Mountains, West Virginia, USA prior to and following two prescribed fires in mixed oak (Quercus spp.) forest stands. Treatments were burn plots on upper slopes or lower slopes fenced to prevent white-tailed deer (Odocoileus virginianus) herbivory or control plots that were unfenced and unburned. Most of the 7 species we observed were the mountain dusky salamander (Desmognathus ocropheaus), red-backed salamander (Plethodon cinereus) and slimy salamander (Plethodon glutinosis). Significant population responses were difficult to interpret with numerous treatment and year interactions. Results largely were equivocal. We found no change in woodland salamander assemblage prior to burning or afterwards. There were few differences in adult to juvenile ratios of salamanders among treatments. Still, a priori contrasts of mountain dusky salamanders and red-backed salamander counts corrected for detection probability were greater under coverboards in the 2 years monitored after both prescribed fires had occurred than before burning or in unburned controls. This suggests that these species responded to the reduced leaf litter on the forest floor by utilizing coverboards more. Similarly, the three predominate species of salamanders also were more numerous under coverboards in plots subjected to deer herbivory with less subsequent forest floor vegetation as compared to those burned plots that were fenced. Our observations would suggest that woodland salamanders somewhat are tolerant of two prescribed fires within close temporal proximity. However, because woodland salamanders can be significantly reduced following timber harvest, continued research is needed to fully understand impacts of fire as a pre-harvest management tool in central Appalachian forests.     

Prescribed burning and understory composition in a temperate deciduous forest,Ohio, USA

Since the advent of widespread suppression in the mid-20th century, fire has been relatively rare in deciduous forests of the eastern United States. However, widespread prescribed burning has recently been proposed as a management tool to favor oak (Quercus spp.) regeneration. To examine the potential effects of fire introduction on the understory community, we experimentally burned small plots and simulated aspects of fire at a forested site in southeastern Ohio. Treatments included two burn intensities, litter removal, increased soil pH, and a control. Treatments were arranged in a randomized block design in two landscape positions (dry upland and moist lowland) and two canopy conditions (gap, no gap). Post-fire vegetation was identified to species, and stems were counted 1, 3, and 14 months after burning. Community composition was more strongly affected by fire in upland plots than in lowlands, but was not affected by canopy openness. Both cool and hot burns reduced post-fire seedling emergence of Acer rubrum, a common overstory tree. Hot burns facilitated germination of Vitis spp., Rhus glabra, and Phytolacca americana, species common in disturbed habitats, and increased graminoid abundance. Cool burns and litter removal facilitated germination of Erechtites hieracifolia and Liriodendron tulipifera suggesting that litter removal is the mechanism by which fire favors colonization. These results suggest that fire applied frequently in the Central Hardwoods Region would cause compositional shifts to graminoids and disturbance-adapted forbs by increasing germination from the seed bank. Fire did not favor species with dormant underground buds, as studies in other ecosystems would suggest. Vegetational responses were noticeably weaker in the second year after burning, indicating that a single fire has only a short-term effect.     

The role of disturbance severity and canopy closure on standing crop of understory plant species in ponderosa pine stands in northern Arizona,USA

Concerns about the long-term sustainability of overstocked dry conifer forests in western North America have provided impetus for treatments designed to enhance their productivity and native biodiversity. Dense forests are increasingly prone to large stand-replacing fires; yet, thinning and burning treatments, especially combined with other disturbances such as drought and grazing, may enhance populations of colonizing species, including a number of non-native species. Our study quantifies plant standing crop of major herbaceous species across contrasting stand structural types representing a range in disturbance severity in northern Arizona. The least disturbed unmanaged ponderosa pine stands had no non-native species, while non-native grasses constituted 7–11% of the understory plant standing crop in thinned and burned stands. Severely disturbed wildfire stands had a higher proportion of colonizing native species as well as non-native species than other structural types, and areas protected from grazing produced greater standing crop of native forbs compared to grazed unmanaged stands. Standing crop of understory plants in low basal area thinned and burned plots was similar to levels on wildfire plots, but was comprised of fewer non-native graminoids and native colonizing plants. Our results also indicate that size of canopy openings had a stronger influence on standing crop in low basal area plots, whereas tree density more strongly constrained understory plant standing crop in dense stands. These results imply that treatments resulting in clumped tree distribution and basal areas <10 m² ha⁻¹ will be more successful in restoring native understory plant biomass in dense stands. Multiple types and severity of disturbances, such as thinning, burning, grazing, and drought over short periods of time can create greater abundance of colonizing species. Spreading thinning and burning treatments over time may reduce the potential for non-native species colonization compared to immediately burning thinned stands.     

Can pine forest restoration promote a diverse and abundant understory and simultaneously resist nonnative invasion?

An important goal of forest restoration is to increase native plant diversity and abundance. Thinning and burning treatments are a common method of reducing fire risk while simultaneously promoting understory production in ponderosa pine (Pinus ponderosa) forests. In this study we examine the magnitude and direction of understory plant community recovery after thinning and burning restoration treatments in a ponderosa pine forest. Our objective was to determine if the post-treatment community was a diverse, abundant, and persistent assemblage of native species or if ecological restoration treatments resulted in nonnative species invasion. This project was initiated at the Grand Canyon-Parashant National Monument, Arizona, USA in 1997. We established four replicated blocks that spanned a gradient of soil types. Each block contained a control and a treated unit. Treated units were thinned to emulate pre-1870 forest stand conditions and prescribed-burned to reintroduce fire to a system that has not burned since ∼1870. We measured plant cover using the point-line intercept method and recorded species richness and composition on 0.05 ha belt transects. We examined the magnitude of treatment responses using Cohen's d effect size analysis. Changes in community composition were analyzed using nonmetric multidimensional scaling (NMS). Native plant species cover and richness increased in the thinned and burned areas compared to the controls. By the last year of the study, annual species comprised nearly 60% of the understory cover in the treatment units. Cheatgrass (Bromus tectorum), a nonnative annual grass, spread into large areas of the treated units and became the dominant understory species on the study site. The ecological restoration treatments did promote a more diverse and abundant understory community in ponderosa pine forests. The disturbances generated by such treatments also promoted an invasion by an undesirable nonnative species. Our results demonstrate the need to minimize disturbances generated by restoration treatments and argue for the need to proactively facilitate the recovery of native species after treatment.     

A comparative analysis of spatial, temporal, and ecological characteristics of forest fires in seasonally dry tropical ecosystems in the Western Ghats, India

The Western Ghats in India is one of the 25 global hotspots of biodiversity, and it is the hotspot with the highest human density. This study considers variations in the regional fire regime that are related to vegetation type and past human disturbances in a landscape. Using a combination of remote sensing data and GIS techniques, burnt areas were delineated in three different vegetation types and various metrics of fire size were estimated. Belt transects were enumerated to assess the vegetation characteristics and fire effects in the landscape. Temporal trends suggest increasingly short fire-return intervals in the landscape. In the tropical dry deciduous forest, the mean fire-return interval is 6 years, in the tropical dry thorn forest mean fire-return interval is 10 years, and in the tropical moist deciduous forest mean fire-return interval is 20 years. Tropical dry deciduous forests burned more frequently and had the largest number of fires in any given year as well as the single largest fire (9900 ha). Seventy percent, 56%, and 30% of the tropical moist deciduous forests, tropical dry thorn forests, and tropical dry deciduous forests, respectively have not burned during the 7-year period of study. The model of fire-return interval as a function of distance from park boundary explained 63% of the spatial variation of fire-return interval in the landscape. Forest fires had significant impacts on species diversity and regeneration in the tropical dry deciduous forests. Species diversity declined by 50% and 60% in the moderate and high frequency classes, respectively compared to the low fire frequency class. Sapling density declined by ca. 30% in both moderate and high frequency classes compared to low frequency class. In tropical moist deciduous ecosystems, there were substantial declines in species diversity, tree density, seedling and sapling densities in burned forests compared to the unburned forests. In contrast forest fires in tropical dry thorn forests had a marginal positive effect on ecosystem diversity, structure, and regeneration.     

Toward reference conditions: wildfire effects on flora in an old-growth ponderosa pine forest

Remote ponderosa pine (Pinus ponderosa) forests on the North Rim of Grand Canyon National Park, Arizona, USA provide valuable examples of reference conditions due to their relatively uninterrupted fire regimes, limited grazing history, and protection from logging. Wildfire is an important disturbance agent in upland forests of the Interior West, yet repeated measurements taken before and after lightning-ignited fires are rare. In 1999, a low-severity Wildland Fire Use fire burned 156 ha on Fire Point, a peninsula dominated by old-growth ponderosa pines, which had not burned for at least 76 years. We measured understory plant community and forest floor characteristics in 1998 (1 year before the fire) and 2001 (2 years after the fire) at this site and at nearby reference sites that did not burn in 1999 but have had continuing fire regimes throughout the past century. After the wildfire, the plant community at Fire Point shifted toward higher compositional similarity with the reference sites. Analysis of functional group composition indicated that this change was due primarily to an increase in annual and biennial forbs. Gayophytum diffusum, Polygonum douglasii, Chenopodium spp., Solidago spp., Elymus elymoides, Calochortus nuttallii, Hesperostipa comata, and Lotus spp. were indicative of forests influenced by recent fires. Species richness, plant cover, plant layer density and plant diversity were significantly lower at Fire Point than at the reference sites, possibly due to long-term fire exclusion, but the fire did not increase the rate of change in these variables after 2 years. Few exotic species were present at any site. Forest floor depths at Fire Point were reduced to depths similar to the reference sites, primarily due to consumption of the duff layer. There was a significant inverse relationship between the ratio of duff:litter and species richness. Compared to fire-excluded forests, old-growth ponderosa pine forests influenced by low-intensity surface fires generally have greater plant species richness (especially annual forbs) and lighter fuel loads. This study supports the continued application of the Wildland Fire Use strategy in old-growth montane forests to maintain and improve forest health by altering understory species composition and reducing fuel loads.     

Tropical reptiles in pine forests: Assemblage responses to plantations and plantation management by burning

Worldwide, the land area devoted to timber plantations is expanding rapidly, especially in the tropics, where reptile diversity is high. The impacts of plantation forestry and its management on native species are poorly known, but are important, because plantation management goals often include protecting biodiversity. We examined the impact of pine (Pinus caribaea) plantations, and their management by fire, on the abundance and richness of reptiles, a significant proportion of the native biodiversity in tropical northern Australia, by (i) comparing abundance and diversity of reptiles among pine plantations (on land cleared specifically for plantation establishment), and two adjacent native forest types, eucalypt and Melaleuca woodlands, and (ii) comparing reptile abundance and richness in pine forest burnt one year prior to the study to remove understorey vegetation with pine forest burnt two years prior to the study. We also examined the influence of fire on reptile assemblages in native vegetation, by comparing eucalypt woodland burnt two years prior to the study and unburnt for eight years. To quantify mechanisms driving differences in reptile richness and abundance among forest types and management regimes, we measured forest structure, the temperatures used by reptiles (operative temperature) and solar radiation, at replicate sites in all forest types and management regimes. Compared to native forests, pine forests had taller trees, lower shrub cover in the understorey, more and deeper exotic litter (other than pine), and were cooler and shadier. Reptile assemblages in pine forests were as rich as those in native forests, but pine assemblages were composed mainly of species that typically use closed-canopy rainforest and prefer cooler, shadier habitats. Burning did not appear to influence the assemblage structure of reptiles in native forest, but burning under pine was associated with increased skink abundance and species richness. Burned pine was not warmer or sunnier than unburned pine, a common driver of reptile abundance, so the shift in lizard use after burning may have been driven by structural differences in understorey vegetation, especially amounts of non-native litter, which were reduced by burning. Thus, burning for management under pine increased the abundance and richness of lizard assemblages using pine. Pine plantations do not support the snake diversity common to sclerophyllous native forests, but pine may have the potential to complement rainforest lizard diversity if appropriately managed.     

Thinning and prescribed fire effects on dwarf mistletoe severity in an eastern Cascade Range dry forest,Washington

Forest thinning and prescribed fire practices are widely used, either separately or in combination, to address tree stocking, species composition, and wildland fire concerns in western US mixed conifer forests. We examined the effects of these fuel treatments alone and combined on dwarf mistletoe infection severity immediately after treatment and for the following 100 years. Thinning, burning, thin + burn, and control treatments were applied to 10 ha units; each treatment was replicated three times. Dwarf mistletoe was found in ponderosa pine and/or Douglas-fir in all units prior to treatment. Stand infection severity was low to moderate, and severely infected trees were the largest in the overstory. Thinning produced the greatest reductions in tree stocking and mistletoe severity. Burning reduced stocking somewhat less because spring burns were relatively cool with spotty fuel consumption and mortality. Burning effects on vegetation were enhanced when combined with thinning; thin + burn treatments also reduced mistletoe severity in all size classes. Stand growth simulations using the Forest Vegetation Simulator (FVS) showed a trend of reduced mistletoe spread and intensification over time for all active treatments. When thinned and unthinned treatments were compared, thinning reduced infected basal area and treatment effects were obvious, beginning in the second decade. The same was true with burned and unburned treatments. Treatment effects on infected tree density were similar to infected basal area; however, treatment effects diminished after 20 years, suggesting a re-treatment interval for dwarf mistletoe.     

The effect of shelterwood harvesting and site preparation on eastern red-backed salamanders in white pine stands

We studied the effects of the regeneration cut of the shelterwood system and four site preparation options on populations of eastern red-backed salamanders in 90–100-year-old white pine forests in central Ontario, Canada. We established the study in 1994 using a randomized complete block design with three replicates and five treatments: (1) no harvest, no site preparation; (2) harvest, no site preparation; (3) harvest, mechanical site preparation; (4) harvest, chemical site preparation; (5) harvest, mechanical and chemical site preparation. We applied harvest and site preparation treatments from fall 1995 to fall 1997. We collected pre-treatment data in spring and summer of 1995 and post-treatment data from 1998 to 2002. We monitored salamander abundance using a grid of 20 cover boards surveyed 10 times per year within each of the 15 treatment plots. We also quantified changes in overstory and understory cover, supply of downed woody debris, and disturbance to the forest floor. Our data suggest that shelterwood cutting and site preparation can have immediate negative effects on the abundance of red-backed salamander populations in pine forest. However, effects are relatively short lived (<5 years). Changes in abundance appeared to be related to overstory and understory cover, and forest floor disturbance.