Response of bark beetles and their natural enemies to fire and fire surrogate treatments in mixed-conifer forests in western Montana

Four treatments (control, burn-only, thin-only, and thin-and-burn) were evaluated for their effects on bark beetle-caused mortality in both the short-term (one to four years) and the long-term (seven years) in mixed-conifer forests in western Montana, USA. In addition to assessing bark beetle responses to these treatments, we also measured natural enemy landing rates and resin flow of ponderosa pine (Pinus ponderosa) the season fire treatments were implemented. All bark beetles were present at low population levels (non-outbreak) for the duration of the study. Post-treatment mortality of trees due to bark beetles was lowest in the thin-only and control units and highest in the units receiving burns. Three tree-killing bark beetle species responded positively to fire treatments: Douglas-fir beetle (Dendroctonus pseudotsugae), pine engraver (Ips pini), and western pine beetle (Dendroctonus brevicomis). Red turpentine beetle (Dendroctonus valens) responded positively to fire treatments, but never caused mortality. Three fire damage variables tested (height of crown scorch, percent circumference of the tree bole scorched, or degree of ground char) were significant factors in predicting beetle attack on trees. Douglas-fir beetle and pine engraver responded rapidly to increased availability of resources (fire-damaged trees); however, successful attacks dropped rapidly once these resources were depleted. Movement to green trees by pine engraver was not observed in plots receiving fire treatments, or in thinned plots where slash supported substantial reproduction by this beetle. The fourth tree-killing beetle present at the site, the mountain pine beetle, did not exhibit responses to any treatment. Natural enemies generally arrived at trees the same time as host bark beetles. However, the landing rates of only one, Medetera spp., was affected by treatment. This predator responded positively to thinning treatments. This insect was present in very high numbers indicating a regulatory effect on beetles, at least in the short-term, in thinned stands. Resin flow decreased from June to August. However, resin flow was significantly higher in trees in August than in June in fire treatments. Increased flow in burned trees later in the season did not affect beetle attack success. Overall, responses by beetles to treatments were short-term and limited to fire-damaged trees. Expansions into green trees did not occur. This lack of spread was likely due to a combination of high tree vigor in residual stands and low background populations of bark beetles.     

Perpetuating old ponderosa pine

We review current knowledge about the use of management treatments to reduce human-induced threats to old ponderosa pine (Pinus ponderosa) trees. We address the following questions: Are fire-induced damage and mortality greater in old than younger trees? Can management treatments ameliorate the detrimental effects of fire, competition-induced stress, and drought on old trees? Can management increase resistance of old trees to bark beetles? We offer the following recommendations for the use of thinning and burning treatments in old-growth ponderosa pine forests. Treatments should be focused on high-value stands where fire exclusion has increased fuels and competition and where detrimental effects of disturbance during harvesting can be minimized. Fuels should be reduced in the vicinity of old trees prior to prescribed burns to reduce fire intensity, as old trees are often more prone to dying after burning than younger trees. Raking the forest floor beneath old trees prior to burning may not only reduce damage from smoldering combustion under certain conditions but also increase fine-root mortality. Thinning of neighboring trees often increases water and carbon uptake of old trees within 1 year of treatment, and increases radial growth within several years to two decades after treatment. However, stimulation of growth of old trees by thinning can be negated by severe drought. Evidence from young trees suggests that management treatments that cause large increases in carbon allocation to radial xylem growth also increase carbon allocation to constitutive resin defenses against bark beetle attacks, but evidence for old trees is scarce. Prescribed, low-intensity burning may attract bark beetles and increase mortality of old trees from beetle attacks despite a stimulation of bole resin production.     

Pinus pinaster Ait. tree mortality following wildfire in Spain

Maritime pine (Pinus pinaster Ait.) is the tree species most affected by wildfire in the Iberian Peninsula. Prediction of the probability of fire-injured tree mortality is critical for management of burned areas, evaluation of the ecological and economic impact of wildfire and prescribed fire planning and application. Pine bark beetles (Scolytidae) frequently attack burned maritime pine stands and cause extensive post-fire mortality throughout the Iberian Peninsula. In the present study, maritime pine trees were monitored for three years following 14 wildfires in four ecotypes in Spain (11 fires in Galicia (Galician ecotype - NW Spain), one fire in Portillo (Meseta-Castellana ecotype - Central Spain), one fire in Rodenal (Rodenal ecotype - Central Spain), and one fire in Genalguacil (Sierra Bermeja ecotype - SW Spain)). Data on tree attributes, crown and bole injury, ground fire severity, Ips sp. presence and tree survival were obtained by examining 3085 trees. Logistic regression models for predicting the probability of delayed maritime pine mortality were developed by use of generalized estimated equations (GEE). An ample range of response to fire damage in mortality was evident among the four ecotypes and different models were fitted for each. The most important variables for predicting tree mortality were total crown volume damaged, presence of Ips sp. attack and cambium kill rating. The results highlight the extensive presence of Ips sp. in burned maritime pine forests and its importance in tree mortality process, the ample range of response of P. pinaster, in terms of post-fire mortality, as well as the need to develop site specific mortality models for the different ecotypes of this species following fire.     

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.     

Physiological responses of ponderosa pine in western Montana to thinning, prescribed fire and burning season

Low-elevation ponderosa pine (Pinus ponderosa Dougl. ex. Laws.) forests of the northern Rocky Mountains historically experienced frequent low-intensity fires that maintained open uneven-aged stands. A century of fire exclusion has contributed to denser ponderosa pine forests with greater competition for resources, higher tree stress and greater risk of insect attack and stand-destroying fire. Active management intended to restore a semblance of the more sustainable historic stand structure and composition includes selective thinning and prescribed fire. However, little is known about the relative effects of these management practices on the physiological performance of ponderosa pine. We measured soil water and nitrogen availability, physiological performance and wood radial increment of second growth ponderosa pine trees at the Lick Creek Experimental Site in the Bitterroot National Forest, Montana, 8 and 9 years after the application of four treatments: thinning only; thinning followed by prescribed fire in the spring; thinning followed by prescribed fire in the fall; and untreated controls. Volumetric soil water content and resin capsule ammonium did not differ among treatments. Resin capsule nitrate in the control treatment was similar to that in all other treatments, although burned treatments had lower nitrate relative to the thinned-only treatment. Trees of similar size and canopy condition in the three thinned treatments (with and without fire) displayed higher leaf-area-based photosynthetic rate, stomatal conductance and mid-morning leaf water potential in June and July, and higher wood radial increment relative to trees in control units. Specific leaf area, mass-based leaf nitrogen content and carbon isotope discrimination did not vary among treatments. Our results suggest that, despite minimal differences in soil resource availability, trees in managed units where basal area was reduced had improved gas exchange and growth compared with trees in unmanaged units. Prescribed fire (either in the spring or in the fall) in addition to thinning, had no measurable effect on the mid-term physiological performance and wood growth of second growth ponderosa pine.     

Prescribed burning of Pinus oocarpa in Honduras II. Effects on nutrient cycling

The effects of prescribed burning on nutrient cycling were studied in a stand of oocarpa pine (Pinus oocarpa Schiede) in central Honduras. Small paired runoff plots were subjected to a low-intensity prescribed burn in one of two seasons and nutrient losses in runoff water and sediment were monitored together with nutrient inputs in bulk precipitation.Burning increased the loss of nutrients and net losses of calcium, potassium and magnesium were recorded during the first $\text{16}\text{1}\text{2}$ months after burning. Increased rates of sediment loss rather than increased losses in surface runoff were responsible for the greater part of the increase in total nutrient losses from the burned plots. Greater quantities of nutrients were lost from the plots burned just prior to the dry season than from those burned after the start of the wet season because of slow recovery of the ground vegetation during the dry season and exposure to the intense rains of May and early June. Recovery from burning was rapid and runoff and sediment loss from the burned plots approached the levels of controls 2 years after burning. As nutrient losses are a reflection of total runoff and sediment losses, it is probable that no net nutrient losses would have been detected during the 2nd year after burning had sampling been continued. The net nutrient losses recorded were small and this is attributed to the low initial fuel loadings, low fire intensities and the rapid rate of recovery of the ground vegetation. The significance of other potential sources of losses and gains of nutrients is discussed and it is concluded that low-intensity prescribed burning for hazard reduction, with burning cycles ranging from three to seven or more years, will reduce the rate of nutrient accumulation on the site rather than deplete the nutrient capital.     

Effects of prescribed fire and season of burn on direct and indirect levels of tree mortality in Ponderosa and Jeffrey Pine Forests in California,USA

Many forests that historically experienced frequent low-intensity wildfires have undergone extensive alterations during the past century. Prescribed fire is now commonly used to restore these fire-adapted forest ecosystems. In this study, we examined the influence of prescribed burn season on levels of tree mortality attributed to prescribed fire effects (direct mortality) and bark beetles (Coleoptera: Curculionidae, Scolytinae) (indirect mortality) in ponderosa pine, Pinusponderosa Dougl. ex Laws., and Jeffrey pine, Pinusjeffreyi Grev. and Balf., forests in California, USA. A total of 816 trees (9.9% of all trees) died during this 3-yr study. Significantly higher levels of tree mortality (all sources) occurred following early and late season burns compared to the untreated control, but no significant difference was observed between burn treatments. The majority (461 trees) of tree deaths were attributed to direct mortality from prescribed burns and was strongly concentrated (391 trees) in the smallest diameter class (<20.2 cm diameter at breast height, dbh). For the largest trees (>50.7 cm dbh), significantly higher levels of tree mortality occurred on early season burns than the untreated control, most of which resulted from indirect mortality attributed to bark beetle attacks, specifically western pine beetle, Dendroctonus brevicomis LeConte, and mountain pine beetle, D. ponderosae Hopkins. Red turpentine beetle, D. valens LeConte, was the most common bark beetle species found colonizing trees, but tree mortality was not attributed to this species. A total of 355 trees (4.3% of all trees) were killed by bark beetles. Dendroctonus brevicomis (67 trees, 18.9%) and D. ponderosae (56 trees, 15.8%), were found colonizing P. ponderosa; and Jeffrey pine beetle, D. jeffreyi Hopkins, was found colonizing P. jeffreyi (seven trees, 2.0%). We also found pine engraver, Ips pini (Say) (137 trees, 38.6%), and, to a much lesser extent, Orthotomicus (=Ips) latidens (LeConte) (85 trees, 23.9%) and emarginate ips, I. emarginatus (LeConte) (3 trees, 0.8%) colonizing P. ponderosa and P. jeffreyi. Few meaningful differences in levels of indirect tree mortality attributed to bark beetle attack were observed between early and late season burns. The incidence of root and root collar pathogens (Leptographium and Sporothrix spp.), including species known to be vectored by bark beetles, was low (18% of trees sampled). The implications of these and other results to management of P. ponderosa and P. jeffreyi forests are discussed in detail.     

不同产脂量云南松树脂道解剖学比较研究

为确定高产脂云南松的早期选择指标,采用石蜡切片法对不同海拔、不同产脂量云南松的针叶、树干韧皮部和木质部的组成性树脂道特征进行解剖观察,结果表明:高产脂与低产脂云南松的针叶树脂道个数、树干木质部树脂道密度、韧皮部树脂道大小及单位长度树脂道数量存在极显著差异(P＜0.01),但不同海拔之间无显著差异;高、低海拔高产脂云南松针叶树脂道数量分别比低产脂的高38.89％、30.34％,树干木质部树脂道密度分别高58.06％、48.48％,韧皮部树脂道大小分别高32.20％、29.73％,韧皮部单位长度树脂道数量分别高21.95％、38.51％.说明针叶树脂道数量、树干木质部树脂道密度及韧皮部树脂道大小3项指标,也可作为云南松产脂力评价的部分指标.     

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.     

The burning characteristics of southeastern oaks: Discriminating fire facilitators from fire impeders

In southeastern pine–oak ecosystems, ecological restoration targets oaks for removal by chemical, mechanical, burning, or combinations of treatments. Managers often pursue oak removal indiscriminately despite the poorly understood historical structure, cover, and ecological function within these ecosystems. Restoration treatments often cite the impediment that oak litter represents to prescribed fire spread and effectiveness. We evaluated the burning characteristics of eight southeastern Quercus spp. by burning collected litter under controlled conditions in a combustion chamber. Replicated burns consisted of 15 g of litter on a 35 cm × 35 cm grid of xylene-soaked cotton strings. Burning characteristics measured included maximum flame height (cm), flaming duration (s), smoldering duration (s), residual ash, and mass loss rate (g s⁻¹). We compared all 8 oaks using ANCOVA, with litterbed depth as a covariate. The oaks differed for all burning characteristics measured (P < 0.001). Rank comparisons placed Quercus stellata and Quercus laevis as the species with greatest fire intensity, sustainability, and consumability, equivalent in many measures to longleaf pine and other fire resisters. Quercus virginiana and Quercus hemisphaerica burned with the least intensity, sustainability, and consumability, burning similarly to sand pine and other fire evaders. These results show that oaks common to southeastern United States ecosystems have litter properties, similar to pines, which vary in their ability to sustain fire. Understanding the pyric properties of oak species also suggests that managers prioritize removal of species that hinder prescribed fire effectiveness for restoration of southeastern USA pine–oak ecosystems.     

Determinants of yield in a non-timber forest product: Copaifera oleoresin in Amazonian extractive reserves

Developing sustainable extractive industries in otherwise intact tropical forest regions requires a sound understanding of the production potential of key resource populations. The oleoresin extracted from Copaifera trees is an economically important non-timber forest product harvested throughout the lowland Amazon basin. We studied oleoresin extraction from four species of Copaifera trees with known harvest histories within two contiguous extractive reserves in western Brazilian Amazonia. We conducted a large-scale experimental harvest of 179 previously unharvested Copaifera trees, in both seasonally flooded (várzea) and adjacent unflooded (terra firme) forests. The likelihood of trees yielding any oleoresin was principally determined by their species identity: C. multijuga was the only species to regularly yield oleoresin (70% of trees). Yield volumes varied both amongst species and forest types: C. multijuga (restricted to terra firme forest) had the highest mean yield of 505 ml, whilst C. guyanensis produced higher volumes of oleoresin in várzea (139 ml) than terra firme (15 ml) forest. Intraspecific differences were driven mainly by tree size. To assess extraction sustainability, we reharvested a sample of C. multijuga trees and compared the oleoresin production of 24 conspecific trees that had been initially harvested one year previously with that of 17 trees initially harvested three years previously. Reharvested trees produced just 35% of the oleoresin volume compared to that when originally drilled, but this response was not affected by the time interval between consecutive harvests. We demonstrate that, within a population of Copaifera, both morphological and environmental factors restrict total productivity; consideration of these factors should inform sustainable management practises. We additionally raise methodological considerations that may improve the comparability of studies.     

马尾松产脂力与生长性状的家系变异及优良家系早期选择

利用设置在福建南平国有来舟林业试验场马尾松高产脂半同胞家系测定林,研究其产脂力与生长、树冠性状在家系间的遗传变异以及它们之间的遗传相关性,并进行脂用马尾松优良家系及优良单株选择。结果表明,马尾松产脂力与生长、树冠性状皆存在显著的家系差异,相对于生长、树冠性状,产脂力变异较大,变异系数高达61.91%,具有丰富的选择基础。产脂力受中度遗传控制,家系遗传力和单株遗传力分别为0.42和0.31,表明对马尾松产脂力通过家系和单株选择可取得较好的改良效果。性状遗传相关分析结果显示,马尾松家系产脂力与胸径、树高和材积呈较高的正遗传相关,表明在遗传育种进程中可同时对生长性状和产脂力进行改良。此外,产脂力与冠幅、冠高、轮盘数、活枝数也呈较高的正遗传相关。综合生长、树冠性状的遗传力以及与产脂力相关程度,认为胸径是高产脂优树间接选择的最佳指标。以单株产脂量和单株材积生长作为综合选择指标,共选出20个优良家系和16株优良单株,选出的优良单株产脂力遗传增益在52.54% 154.40%,单株材积遗传增益在0.22% 31.85%。     

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.     

Burning and mowing as habitat management for capercaillie Tetrao urogallus: An experimental test

In Scots pine Pinus sylvestris forests, the important ecological effects of natural fires could be emulated using prescribed fire. Species that may benefit from fire effects include capercaillie Tetrao urogallus, a large forest grouse. A key component of forest habitats for capercaillie is the ericaceous shrub, bilberry Vaccinium myrtillus, which is eaten by capercaillie, and supports abundant arthropods, taken by young chicks. We carried out an experiment testing whether prescribed burning would be a valuable technique for capercaillie habitat management. The study took place at Abernethy Forest, the largest ancient native pinewood in Britain, and a key capercaillie site, holding c 8-20% of the British population. Prescribed fire in woodland is highly novel in Britain. We therefore also tested mowing, which might replicate some fire effects more cheaply and safely. Twenty-five experimental blocks were established within open pine stands with ground vegetation including bilberry, but dominated by heather Calluna vulgaris. Each block held three 700 m² plots, randomly assigned to control, mow and burn. Vegetation, arthropods and capercaillie dung were monitored over a 7-year period, including 1 year prior to treatment. Mean bilberry cover, initially around 12%, increased in mown and burnt areas, but there were also increases in controls, following unusual natural die-back of heather. By the sixth season after treatment, bilberry cover was significantly higher in burnt and mown areas than controls, averaging 27% (95% confidence intervals 24-30), compared to 20% (19-21) in controls. Biomass of spiders, an important dietary group for capercaillie chicks, as measured by pitfall trapping, was significantly higher in burnt and mown plots than controls, by about 56% (38-76). However, biomass of caterpillars, often considered a more important dietary group, did not show clear differences between treatments. An alternative analysis was used to ‘statistically remove’ natural heather die-back; this enhanced the treatment differences in bilberry cover and spider biomass. Capercaillie dung counts suggested that burnt, and especially mown areas, had more summer capercaillie usage than controls. Capercaillie conservation at sites similar to Abernethy is likely to benefit from either prescribed fire or mowing, because these techniques increase bilberry and spider abundance. This study illustrates the value of collaboration between researchers and land-managers, in developing and testing novel management techniques. We support the idea that ‘dominance reduction’, delivered through managed disturbance, offers a general principle to guide land-managers wishing to maintain biodiversity, particularly where key species, like capercaillie, are strongly associated with sub-dominant plant species like bilberry.     

Prescribed burning of Pinus oocarpa in Honduras I. Effects on surface runoff and sediment loss

The effects of low-intensity prescribed burning on surface runoff and sediment loss were studied in a stand of oocarpa pine (Pinus oocarpa Schiede) in central Honduras. The effects of burning in two seasons were compared on small paired plots on 10°, 25° and 40° slopes. Over a period of almost 2 years, mean percent runoff was 1.73% on the control plots and 5.03% on the burned plots. Mean sediment loss during the same period was 80 kg ha^?1 on the control plots and 1732 kg ha^?1 on the burned plots. The relationship between slope and surface runoff and sediment loss was negative; the effect of slope being masked by variation of other site factors. Recovery from burning was rapid and is attributed to the rapid rate of recovery of the ground vegetation of grasses and forbs which are adapted to frequent burning. Surface runoff and sediment loss on control plots were very low and the increases caused by burning are considered an acceptable alternative to the exposure of the overstory and site to the high risk of wildfires in accumulated fuels. Greater runoff and sediment loss were recorded on the plots burned in February than on those burned in June. As the period November to mid-February offers the greatest number of days with weather conditions suitable for low-intensity prescribed burning, it is concluded that burning for hazard reduction should be conducted as early as possible in this period, in November and December, to permit greater recovery of the ground vegetation before the heavy rains of May and early June.     

Effects of light/darkness, thermal shocks and inhibitory components on germination of Pinus canariensis, Pinus halepensis and Pinus pinea

Knowledge of the germination characteristics of Pinus species can help in the understanding, prediction and management of the regeneration of pine forests. In the Canary Islands, several exotic pines (Pinus halepensis L. and Pinus pinea L.) were planted with Pinus canariensis Chr. Sm. Ex DC, the only native pine species, and there is now an interest in controlling these exotic species to restore the original forest. The main objective of the present study is to determine the germination response of P. canariensis, P. halepensis and P. pinea to different light regimes (darkness and light/darkness), thermal shocks and the presence of inhibitory substances from the leaves and litter of P. canariensis. P. halepensis seeds showed the highest viability and germination rate. Darkness accelerated P. halepensis germination, while exudates accelerated P. canariensis germination. Only treatments of 200 °C for 5 min and 300 °C for 5 min significantly decreased the germination of all three pine species. In the absence of strong differences in germination among species after treatments, the key for fire management or prescribed burning in this case may be the sprouting ability of P. canariensis. A possible management strategy to control the two obligate seeder exotic species could be to use one intense prescribed fire followed by a low-intensity prescribed fire after seed bank germination in the field, so in this way, only P. canariensis could resprout after fire and it would eliminate only the exotic pines in a mixed stand.     

Can prescribed fire be used to maintain fuel treatment effectiveness over time in Black Hills ponderosa pine forests?

We determine the time frame after initial fuel treatment when prescribed fire will be likely to produce high enough mortality rates in ponderosa pine (Pinus ponderosa var. scopulorum Dougl. ex Laws.) regeneration to be successful in maintaining treatment effectiveness in the Black Hills of South Dakota. We measured pine regeneration in disturbed stands and young pine growth rates to estimate the susceptibility of pine regeneration to prescribed fire with time since initial treatment. We also determined surface fuel accumulation rates for stands after prescribed fire to help estimate likely fire behavior in maintenance prescribed fire. Given our estimates of regeneration density and tree size, and likely fire behavior, we then used small pine tree mortality—fire effect relations to estimate the effects of prescribed fire on developing understory pine at specific times since initial treatments.     

Roost tree selection by northern myotis (Myotis septentrionalis) maternity colonies following prescribed fire in a Central Appalachian Mountains hardwood forest

Following decades of fire suppression in eastern forests, prescribed fire as a tool to restore or enhance oak (Quercus spp.)-dominated communities is gaining widespread acceptance in the Appalachian Mountains and elsewhere. However, the interactions of fire with biotic components such as wildlife that might be impacted by prescribed fire are poorly documented. For tree-roosting bats, fire can enhance roosting habitat by creating snags and increasing solar radiation at existing roosts. In 2007 and 2008, we examined roost selection of forest-interior dwelling northern myotis (Myotis septentrionalis) maternity colonies in stands treated with prescribed fire (hereafter, fire) and in unburned (hereafter, control) stands on the Fernow Experimental Forest, West Virginia. Using radio telemetry, we tracked 36 female northern myotis to 69 roost trees; 25 in the fire treatment and 44 in the control treatment. Using logistic regression and an information-theoretic model selection approach, we determined that within the fire treatment, northern myotis maternity colonies were more likely to use cavity trees that were smaller in diameter, higher in crown class, and located in stands with lower basal area, gentler slopes, and higher percentage of fire-killed stems than random trees. Moreover, roosts often were surrounded by trees that were in the upper crown classes. In the control treatment, northern myotis were more likely to roost nearer the tops of larger diameter cavity trees in early stages of decay that were surrounded by decaying trees in the upper crown classes than random trees. Roost trees in the fire treatment were associated with larger overall canopy gaps than roost trees within the control treatment. Regardless of treatment, northern myotis maternity colonies roosted in black locust (Robinia pseudoacacia) in greater proportion than its availability. Ambient temperatures recorded at a subset of roost trees in fire and control treatments indicated that daily minimum temperatures were similar, but daily mean and maximum temperatures were higher in the fire treatments, possibly due to larger canopy gaps created by the senescence and decay of the surrounding fire-killed overstory trees. Northern myotis roost-switching frequency, distance between successive roosts, and duration of individual roost tree use were similar between the fire and control treatments, suggesting similar roost tree availability despite a significantly higher proportion of potential roost trees in the fire treatment. Northern myotis readily exploited alterations to forest structure created by the reintroduction of fire, which accelerated snag creation and enlarged existing or created new canopy gaps, but it remains to be determined if these conditions translate into increased recruitment and survivorship.     

High vs. low yielding oleoresin Pinus halepensis Mill. trees GC terpenoids profiling as diagnostic tool

? A discriminant study based on samples taken from high and low yielding oleoresin trees of two Greek populations, Chalkidiki and Euboia, was carried out. Oleoresin of Pinus halepensis Mill. was characterised by GC/MS analysis.

? The objectives of this study were: (i) to identify in detail the composition of the oleoresin of P. halepensis and in particular of high yielding trees (plus trees) (ii) to investigate a potential relationship between the oleoresin compounds and the oleoresin yield and (iii) to investigate any correlations among the compounds.

? About forty monoterpenes, sesquiterpenes and diterpenes were identified as main compounds representing 97.40% of the analyzed oleoresin. α-Pinene, methyl abietate, abietic acid, palustric acid, isopimaric acid and neoabietic acid were the major compounds. Efficient discrimination was achieved between the two populations and between the two groups of trees (high and low yielding). In both cases, the differentiation was due to the quantitative variability of certain compounds. High positive correlations were found among certain compounds.

? The results suggest that the oleoresin profile is a useful tool for the discrimination of trees according to their provenance or their oleoresin yield.

     

Restoring longleaf pine (Pinus palustris Mill.) in loblolly pine (Pinus taeda L.) stands: Effects of restoration treatments on natural loblolly pine regeneration

Historical land use and management practices in the southeastern United States have resulted in the dominance of loblolly pine (Pinus taeda L.) on many upland sites that historically were occupied by longleaf pine (Pinus palustris Mill.). There is currently much interest in restoring high quality longleaf pine habitats to such areas, but managers may also desire the retention of some existing canopy trees to meet current conservation objectives. However, fast-growing natural loblolly pine regeneration may threaten the success of artificially regenerated longleaf pine seedlings. We evaluated the establishment and growth of natural loblolly pine regeneration following different levels of timber harvest using single-tree selection (Control (uncut, residual basal area ∼16 m²/ha), MedBA (residual basal area of ∼9 m²/ha), LowBA (residual basal area of ∼6 m²/ha), and Clearcut (complete canopy removal)) and to different positions within canopy gaps (approximately 2800 m²) created by patch cutting at two ecologically distinct sites within the longleaf pine range: Fort Benning, GA in the Middle Coastal Plain and Camp Lejeune, NC in the Lower Coastal Plain. The density of loblolly pine seedlings was much higher at Camp Lejeune than at Fort Benning at the end of the first growing season after harvesting. Following two growing seasons, there were no significant effects of canopy density or gap position on the density of loblolly pine seedlings at either site, but loblolly pine seedlings were taller on treatments with greater canopy removal. Prescribed fires applied following the second growing season killed 70.6% of loblolly pine seedlings at Fort Benning and 64.3% of seedlings at Camp Lejeune. Loblolly pine seedlings were generally less than 2 m tall, and completeness of the prescribed burns appeared more important for determining seedling survival than seedling size. Silvicultural treatments that include canopy removal, such as patch cutting or clearcuts, will increase loblolly pine seedling growth and shorten the window of opportunity for control with prescribed fire. Therefore, application of prescribed fire every 2-3 years will be critical for control of loblolly pine regeneration during restoration of longleaf pine in existing loblolly pine stands.