Red Pine Stands Research Articles

Diplodia Shoot Blight Damage to Understory Red Pine Seedlings

The fungal pathogen Diplodia pinea has caused substantial damage to red pine (Pinus resinosa Ait.) seedlings in nurseries, but the impact of Diplodia shoot blight on naturally occurring seedlings has not been thoroughly investigated. In 2008, incidence and severity of Diplodia shoot blight symptoms on living red pine seedlings and shoot blight-associated mortality of seedlings were quantified in understories of mature plantations at four sites in Wisconsin. Blighted shoots were examined for characteristic fruiting structures of the pathogen and a species-specific polymerase chain reaction (PCR) assay confirmed D. pinea as present on these shoots. Mean seedling mortality ranged from 13 to 31% and shoot blight incidence on living seedlings was ≥ 94% at each site. Mean damage severity ratings on a scale from 0 to 3 ranged from 2.16 to 2.98, with evidence of previous blighting of leaders on ≥ 54% of seedlings. These results document Diplodia shoot blight damage to naturally occurring understory trees and the potential for this disease to impede efforts to naturally regenerate red pine stands.

Structure and development of old-growth, unmanaged second-growth, and extended rotation Pinus resinosa forests in Minnesota, USA

The structure and developmental dynamics of old-growth forests often serve as important baselines for restoration prescriptions aimed at promoting more complex structural conditions in managed forest landscapes. Nonetheless, long-term information on natural patterns of development is rare for many commercially important and ecologically widespread forest types. Moreover, the effectiveness of approaches recommended for restoring old-growth structural conditions to managed forests, such as the application of extended rotation forestry, has been little studied. This study uses several long-term datasets from old growth, extended rotation, and unmanaged second growth Pinus resinosa (red pine) forests in northern Minnesota, USA, to quantify the range of variation in structural conditions for this forest type and to evaluate the effectiveness of extended rotation forestry at promoting the development of late-successional structural conditions. Long-term tree population data from permanent plots for one of the old-growth stands and the extended rotation stands (87 and 61years, respectively) also allowed for an examination of the long-term structural dynamics of these systems.Old-growth forests were more structurally complex than unmanaged second-growth and extended rotation red pine stands, due in large part to the significantly higher volumes of coarse woody debris (70.7 vs. 11.5 and 4.7m3/ha, respectively) and higher snag basal area (6.9 vs. 2.9 and 0.5m2/ha, respectively). In addition, old-growth forests, although red pine-dominated, contained a greater abundance of other species, including Pinus strobus, Abies balsamea, and Picea glauca relative to the other stand types examined. These differences between stand types largely reflect historic gap-scale disturbances within the old-growth systems and their corresponding structural and compositional legacies. Nonetheless, extended rotation thinning treatments, by accelerating advancement to larger tree diameter classes, generated diameter distributions more closely approximating those found in old growth within a shorter time frame than depicted in long-term examinations of old-growth structural development. These results suggest that extended rotation treatments may accelerate the development of old-growth structural characteristics, provided that coarse woody debris and snags are deliberately retained and created on site. These and other developmental characteristics of old-growth systems can inform forest management when objectives include the restoration of structural conditions found in late-successional forests.

Carbon storage and soil CO2 efflux rates at varying degrees of damage from pine wilt disease in red pine stands

We evaluated the carbon (C) storage and soil CO2 efflux rates of red pine (Pinus densiflora S. et Z.) stands damaged by pine wilt disease (PWD) in Korea. Ten red pine plots at varying degrees of damage from PWD were established and grouped into five categories (very slightly, slightly, moderately, severely, and very severely damaged plots) based on differences in the tree density. The incidence of PWD was a major cause of C loss from forest ecosystems, but the magnitude of loss depended on the severity of disease damage. An exponential regression of the CO2 efflux rates against the corresponding soil temperature was highly significant (R2=0.82–0.95, P<0.01) for the varying degrees of damage from PWD. The rates of change in the CO2 efflux rates with temperature, as defined by the Q10 values, were generally lower in the slightly (2.94) versus the moderately (3.60) or severely (4.26) PWD-damaged stands. The cumulative soil CO2–C efflux rates for two years were significantly higher in the slightly (10.8MgCha−1yr−1) or moderately (10.9MgCha−1yr−1) versus the very severely (7.9MgCha−1yr−1) PWD-damaged stands. The results indicate that the C storage and soil CO2 efflux rates in red pine stands can be impacted by the incidence of PWD, with a significant C reduction in the severely damaged stands.

Short-term effects of fertilizer application on soil respiration in red pine stands

This study was conducted to evaluate the dynamics of soil respiration (total soil and heterotrophic respiration) following fertilizer application in red pine forests. Fertilizer (N:P:K = 113:150:37 kg/ha), which reflects current practices in Korean forest, was applied in April 2011, and total soil and heterotrophic respiration rates were monitored from April 2011 to March 2012. Monthly variation of total soil and heterotrophic respiration rates were similar between the fertilizer and control treatments, as soil temperature was the dominant factor controlling the both rates. Total soil respiration rates during the study period were not significantly different between the fertilizer (0.504 g CO2 m-2 h-1) and control (0.501 g CO2 m-2 h-1) treatments. However, the proportion of heterotrophic respiration was higher in the fertilizer (78% of total soil respiration rates) than in the control (62% of total soil respiration rates) treatments. These results suggest that current fertilizer practices in Korea forest soil do not substantially affect total soil respiration rates.

Crown fuel characteristics and carbon emission from Japanese red pine stands burned by crown fire in Mt. Palgong, South Korea

Carbon emissions from forest fires are considered an important factor of ecosystem carbon balance and global climate change. Carbon emissions from Japanese red pine stands (Pinus densiflora S. et Z.) burned by crown fire were estimated at Mt. Palgong in Daegu Metropolitan City, and crown fuel characteristics, including crown bulk density, crown base height, and fuel moisture content of Japanese red pine, were analyzed. Total biomass combusted was calculated by subtracting the biomass of burned stands from that of unburned stands exhibiting similar stand structures and site environments. Ten trees in the unburned area and five trees in the burned area were cut by using direct harvesting techniques to estimate crown layer biomass. All biomass sampled was oven-dried and weighed. The dry weight ratios of stems, branches, and needles were 70%, 21%, and 9%, respectively. The available fuel load susceptible to combustion during the crown fire spread was equivalent to 55% of the crown layer biomass. The crown bulk density was 0.24 kg/m3 on average. The estimated amount of CO2 was 23,454 kg CO2/ha for the crown layer. These results will be useful for calculating the amount of CO2 emitted from forest fires and for developing a forest carbon model in P. densiflora forests.

Effects of reforestation on near‐surface saturated hydraulic conductivity in a managed forest landscape, southern Ontario, Canada

ABSTRACTReforestation of previously deforested landscapes often increases soil organic matter content and porosity as the plantation forest ages, leading to increased soil saturated hydraulic conductivity (KH). However, the time required for a reforested soil's KH to recover to that of the original forest differs considerably between locations because of variations in forest, climatic and soil properties. We examined a chronosequence of sites on similar soils in a managed forest landscape in southern Ontario, Canada, ranging from open fields deforested in the late 19th century, through red pine (Pinus resinosa) stands of varying age, to 100+ year‐old mixed conifer–hardwoods. Soil texture, organic matter content, bulk density, KH, and overstory and understory forest characteristics were measured. For sites with similar soil textures, there was a general increase in KH in the following sequence: open fields → red pine plantations → mixed conifer–hardwood stands. There were no significant changes in near‐surface organic matter contents or soil bulk densities with forest age, and neither factor was related to temporal changes in KH. Temporal trends in KH were associated with increased understory density with forest age, suggesting that increases in KH were driven by understory root development and greater macroporosity. It may take ~25 years before reforestation begins to affect soil infiltration characteristics at the stand scale and at least 40 years following planting before the KH of soils under red pine plantations begins to equal that for undisturbed mixed conifer–hardwood stands. This recovery may be assisted by management activities such as thinning of red pine stands, which promotes understory development.Copyright © 2012 John Wiley &amp; Sons, Ltd.

Measurement and modeling of canopy water partitioning in a reforested landscape: The Ganaraska Forest, southern Ontario, Canada

Summary A major hydrologic consequence of reforestation is an increase in canopy interception ( I c ), with consequent effects on such processes as soil and groundwater recharge. This study examines the change in rainfall partitioning between throughfall ( TF ), stemflow ( SF ) and I c in red pine plantations of different ages and in mature mixed hardwood forest stands in the Ganaraska Forest on the crest of the Oak Ridges Moraine in southern Ontario. It also tests the ability of the Liu interception model to predict I c in these stands. Forest characteristics, TF , SF and I c were either measured or estimated during the 2009 and 2010 growing seasons for three red pine stands 36–41 years old (as of 2009), three red pine stands 57–62 years old, and three mixed hardwood stands 74–107 years old. Despite considerable variability in total I c in a given stand type in both years, there was a general increase in I c as a fraction of above-canopy precipitation ( P g ) from younger to older red pine stands and to mixed hardwood stands. This was accompanied by a decrease in SF depth as a fraction of P g from younger to older red pine stands, followed by an increase in SF / P g in mixed hardwoods. The Liu model provided good predictions of I c in 2009 for eight of nine stands with canopy storage capacities optimized using the 2009 data. Model performance was almost as good when tested against the 2010 data using the 2009 model parameters. Adjustment of the parameter representing the ratio of mean evaporation rate to mean rainfall rate to account for greater evaporative demand in 2010 led to a modest improvement in model performance. The increase in growing season I c / P g ratios as red pine plantations in the Ganaraska Forest mature and undergo a managed transition to mature mixed hardwoods may have important implications for soil water and groundwater recharge that require further study. The Liu model is a promising means of estimating I c in forest stands of differing age and type, which in turn will assist in understanding the hydrologic consequences of reforestation in this landscape.

Dispersal and edge behaviour of bark beetles and predators inhabiting red pine plantations

Quantifying dispersal in predator–prey systems can improve our understanding of how these species interact in space and time, as well as their relative distributions across complex landscapes. We measured the dispersal abilities of three forest insects associated with red pine decline: the eastern five spined pine engraver Ips grandicollis (Coleoptera: Curculionidae), its main predator Thanasimus dubius (Coleoptera: Cleridae) and the basal stem and root colonizer Dendroctonus valens (Coleoptera: Curculionidae). We also examined the edge behaviours of these species and the predator Platysoma spp (Coleoptera: Histeridae) between red pine stands (habitat) and clearings (nonhabitat). Thanasimus dubius dispersed 12 times farther than its prey I. grandicollis, with 50% of predators dispersing farther than 1.54 km. This profound difference in dispersal behaviour between prey and predator may contribute to the clumped distribution of I. grandicollis. Most T. dubius and D. valens were confined in the pine forest, thus showing strong edge behaviour. This differed from I. grandicollis and Platysoma spp., which were commonly found in open areas adjacent to red pine plantations. The bark beetle I. grandicollis and one of its main predators, T. dubius, exhibited different patterns of movement within a fragmented landscape. Despite a greater dispersal ability of T. dubius within forests, the spatial distribution of this predator may be restricted by fragmentation of its habitat, and provide an opportunity for partial escape of its prey. The present study contributes to our knowledge of top‐down forces within red pine stands undergoing decline. Differences of dispersal patterns and edge behaviour could contribute to the initiation of new pockets of decline, as well as the connectedness among existing ones.

Long-term Effect of Silvicultural Thinnings on Soil Carbon and Nitrogen Pools

The effects of long-term silvicultural thinning on soil C and N content are not well known. We evaluated the impact of periodic thinnings on soil C and N pools in a 134-yr-old red pine (Pinus resinosa Ait.) forest in Minnesota, and a 104 yr-old northern hardwood forest in Wisconsin. The red pine stands had five thinning regimes (13.8, 18.4, 22.7, 27.6, 32.1 m2 ha-1 residual basal area [BA]), which were cut five or seven times over 46 yr. The northern hardwood stands had three residual basal area treatments (13.8, 17.2, 20.6 m2 ha-1) that were thinned five times over 50 yr. Our results showed that the heaviest-thinned (13.8 m2 ha-1) and uncut control red pine stands had higher C and N contents in the mineral A horizon, as compared to the other four thinning treatments. Multiple thinning did not affect C and N pool size in the forest floor and surface mineral soil (30-cm depth) in either red pine or hardwood stands. Within stand BA variability was positively correlated to C and N pools in the forest floor of the lightly-thinned (32.1 m2 ha--1) red pine treatment, but was negatively correlated to C and N pools in the A horizon. Our study and the literature indicate that stem-only removal for wildfire risk reduction and bio-energy production would have little impact on total soil C and N pools. However, more information is needed on the effects of whole-tree thinning regimes on soil C and nutrient contents.

Carbon stocks across a chronosequence of thinned and unmanaged red pine (Pinus resinosa) stands

Forests function as a major global C sink, and forest management strategies that maximize C stocks offer one possible means of mitigating the impacts of increasing anthropogenic CO2 emissions. We studied the effects of thinning, a common management technique in many forest types, on age-related trends in C stocks using a chronosequence of thinned and unmanaged red pine (Pinus resinosa) stands ranging from 9 to 306 years old. Live tree C stocks increased with age to a maximum near the middle of the chronosequence in unmanaged stands, and increased across the entire chronosequence in thinned stands. C in live understory vegetation and C in the mineral soil each declined rapidly with age in young stands but changed relatively little in middle-aged to older stands regardless of management. Forest floor C stocks increased with age in unmanaged stands, but forest floor C decreased with age after the onset of thinning around age 40 in thinned stands. Deadwood C was highly variable, but decreased with age in thinned stands. Total ecosystem C increased with stand age until approaching an asymptote around age 150. The increase in total ecosystem C was paralleled by an age-related increase in total aboveground C, but relatively little change in total belowground C. Thinning had surprisingly little impact on total ecosystem C stocks, but it did modestly alter age-related trends in total ecosystem C allocation between aboveground and belowground pools. In addition to characterizing the subtle differences in C dynamics between thinned and unmanaged stands, these results suggest that C accrual in red pine stands continues well beyond the 60-100 year management rotations typical for this system. Management plans that incorporate longer rotations and thinning in some stands could play an important role in maximizing C stocks in red pine forests while meeting other objectives including timber extraction, biodiversity conservation, restoration, and fuel reduction goals.

Detection and Identification of Two New Native Hymenopteran Parasitoids Associated with the ExoticSirex noctilioin North America

Abstract. Rhyssa crevieri (Provancher), a primary parasitoid of Siricidae wasps, and the Holarctic poemeniine ichneumonid, Pseudorhyssa nigricornis (Ratzeburg), a cleptoparasitoid of Siricidae via its parasitoids (Ichneumonidae: Rhyssinae), were reared from two stands of Scots pine (Pinus sylvestris L.) and red pine (P. resinosa Ait.) infested with the exotic siricid Sirex noctilio F. near Tully (Onondaga Co.), New York, in 2010. Previously, P. nigricornis has been recorded from the primary siricid parasitoids Rhyssa persuasoria (in Europe and North America) and R. howdenorum Townes and Townes and R. lineolata (Kirby) (in North America). Peak emergence of P. nigricornis occurred in early May concurrently with R. persuasoria and R. crevieri. A second peak occurred in late May, which overlapped peak emergence of R. lineolata and Megarhyssa nortoni (Cresson). Although 14 individuals of two native siricids, Sirex nigricornis F. and S. edwardsii Brulle, emerged from sampled trees, the number of S. noctilio rec...

Can landscape-level ecological restoration influence fire risk? A spatially-explicit assessment of a northern temperate-southern boreal forest landscape

Management strategies to restore forest landscapes are often designed to concurrently reduce fire risk. However, the compatibility of these two objectives is not always clear, and uncoordinated management among landowners may have unintended consequences. We used a forest landscape simulation model to compare the effects of contemporary management and hypothetical restoration alternatives on fire risk in northern temperate and southern boreal forests of the Border Lakes Region in Minnesota, USA, and Ontario, Canada. Six main model scenarios simulated different combinations of timber harvest, fire exclusion, wildland fire use, and prescribed fire. Mean fire risk values were calculated as a function of high risk fuel type occurrence, fire events, and windthrow events over model time, and were compared among scenarios and among major management areas. Our model results indicate that a continuation of contemporary management, with limited wildland fire use, would increase fire risk over time and lead to greater continuity of high-risk fuel types in parks and wilderness areas. Compared to the contemporary management scenario, greater use of wildland fire in a historical natural disturbance scenario and three alternative restoration scenarios resulted in less spatially aggregated high-risk fuels over time and lower long-term fire risk in parks and wilderness. Outside of parks and wilderness, prescribed fire with logging was effective at reducing fire risk on portions of the landscape in two restoration scenarios, largely by maintaining deciduous tree dominance and fire-tolerant red and white pine stands, and timber harvest alone maintained patches of less fire-prone deciduous forests in some scenarios. However, forest restoration and fire risk objectives were not always compatible, especially when restoration of fire-prone forest conflicted with the goal of reducing risk of large, severe fires. Both fire risk reduction and forest restoration objectives will benefit from spatially coordinated, landscape-level planning among landowners.

Soil organic carbon sequestration as affected by afforestation: the Darab Kola forest (north of Iran) case study

Following the ratification of the Kyoto Protocol, afforestation of formerly arable lands and/or degraded areas has been acknowledged as a land-use change contributing to the mitigation of increasing atmospheric CO(2) concentration in the atmosphere. In the present work, we study the soil organic carbon sequestration (SOCS) in 21 year old stands of maple (Acer velutinum Bioss.), oak (Quercus castaneifolia C.A. Mey.), and red pine (Pinus brutia Ten.) in the Darab Kola region, north of Iran. Soil samples were collected at four different depths (0-10, 10-20, 20-30, and 30-40 cm), and characterized with respect to bulk density, water content, electrical conductivity, pH, texture, lime content, total organic C, total N, and earthworm density and biomass. Data showed that afforested stands significantly affected soil characteristics, also raising SOCS phenomena, with values of 163.3, 120.6, and 102.1 Mg C ha(-1) for red pine, oak and maple stands, respectively, vs. 83.0 Mg C ha(-1) for the control region. Even if the dynamics of organic matter (OM) in soil is very complex and affected by several pedo-climatic factors, a stepwise regression method indicates that SOCS values in the studied area could be predicted using the following parameters, i.e., sand, clay, lime, and total N contents, and C/N ratio. In particular, although the chemical and physical stabilization capacity of organic C by soil is believed to be mainly governed by clay content, regression analysis showed a positive correlation between SOCS and sand (R = 0.86(**)), whereas a negative correlation with clay (R = -0.77(**)) was observed, thus suggesting that most of this organic C occurs as particulate OM instead of mineral-associated OM. Although the proposed models do not take into account possible changes due to natural and anthropogenic processes, they represent a simple way that could be used to evaluate and/or monitor the potential of each forest plantation in immobilizing organic C in soil (thus reducing atmospheric C concentration), as well as to select more appropriate species during forestation plan management at least in the north of Iran.

Does soil organic matter variation affect the retention of 15NH4+ and 15NO3− in forest ecosystems?

Human activities have fundamentally changed global nitrogen (N) cycling, leading to elevated N deposition in most parts of the world. The fate of deposited N, whether being retained to sustain plant growth or causing ecosystem N saturation, is critical to the global carbon (C) cycling and local environment. In a short-term laboratory experiment, we used 15N-labeled NH4+ and NO3− to study the fate of N inputs in forest soils and what regulates N retention. Soils with a wide range of organic matter content and other attributes were collected from a 70-year-old plantation containing monotypic stands of Norway spruce (Picea abies), red pine (Pinus resinosa), sugar maple (Acer saccharum), and red oak (Quercus rubra), and separated into 0–5cm and 5–15cm layers. Nitrogen added to the soil was either immediately extracted (Time 0: T0) with K2SO4 solution, or incubated for 7 d (T7) and then extracted. Retention of 15N into the non-extractable soil pool at T0 was limited; but after the 7-d incubation, between 20 and 70% of the 15NH4+ was retained. Nitrification transformed on average 50% of the 15NH4+ into 15NO3− during the incubation while retention of 15NO3− at T7 remained low (7.40±1.08%). Retention of 15NH4+ into non-extractable soil at T7 was positively correlated to the percentage of soil organic matter (SOM) (r2=0.323, P<0.001), and was significantly higher (P<0.001) in the high-SOM 0–5cm layer than in the low-SOM 5–15cm layer. Conversion of 15NH4+ to 15NO3− during incubation significantly reduced the 15NH4+ retention (P<0.001). Our results suggest that the variations of SOM and other soil attributes play strong roles in the retention of newly deposited inorganic N and could affect forest ecosystem responses to chronic N deposition.

Model-Based Estimation of Forest Canopy Height in Red and Austrian Pine Stands Using Shuttle Radar Topography Mission and Ancillary Data: A Proof-of-Concept Study

In this paper, accurate tree stand height retrieval is demonstrated using C-band Shuttle Radar Topography Mission (SRTM) height and ancillary data. The tree height retrieval algorithm is based on modeling uniform tree stands with a single layer of randomly oriented vegetation particles. For such scattering media, the scattering phase center height, as measured by SRTM, is a function of tree height, incidence angle, and the extinction coefficient of the medium. The extinction coefficient for uniform tree stands is calculated as a function of tree height and density using allometric equations and a fractal tree model. The accuracy of the proposed algorithm is demonstrated using SRTM and TOPSAR data for 15 red pine and Austrian pine stands (TOPSAR is an airborne interferometric synthetic aperture radar). The algorithm yields root-mean-square (rms) errors of 2.5-3.6 m, which is a substantial improvement over the 6.8-8.3-m rms errors from the raw SRTM minus National Elevation Dataset Heights.

Interactions among forest composition, structure, fuel loadings and fire history: A case study of red pine-dominated forests of Seney National Wildlife Refuge, Upper Michigan

Red pine ( Pinus resinosa Ait.) has been a historically important species in the eastern United States and Canada. Prior to European settlement, fire played a major role in determining the composition and structure of red pine-dominated forests. However, fire suppression efforts have prevented natural regeneration of red pine and the development of structurally diverse red pine-dominated forests across its natural range. To better understand how past forest history affects the current state of red pine-dominated forests in Upper Michigan, we quantified the role of forest history on forest structure and fuel loadings on eighty 500 m 2 plots distributed across Seney National Wildlife Refuge (SNWR). The Seney Wilderness Area of SNWR has experienced few direct human effects, and has escaped the impact of fire suppression policies. Using principal components analysis, we quantified the variation in stand composition, structure, and diversity and related this variability to current fuel loadings, fire history, and harvesting history. The first principal component represented the structural and compositional variation across our dataset associated with the harvesting history of the 50 sampled stands. Stands with a history of cutting clearly differentiated themselves by high abundance of jack pine ( Pinus banksiana Lam.) and lower structural diversity of the overstory and of the understory vegetation. The second principal component revealed a negative correlation between red pine overstory abundance and compositional diversity of the stands, as determined by the Shannon Diversity Index. The third principal component differentiated complex, multi-cohort stands with old (250–300 years) trees in the overstory, which we believe resulted from repeated fires, from younger, less structurally complex stands. Stands which experienced repeated fires showed reduced amounts of fine woody debris and shallower duff depth. No relationship was found between descriptors of fire history and the amount of coarse woody debris (CWD) or litter. CWD increased in multi-cohort stands with high variations in tree diameter, whereas litter depth was higher in both jack pine-dominated, harvested stands and structurally diverse red pine stands and lower in the middle of this gradient. We suggest that fire has a role in restoration programs and sustainable management of red pine-dominated forest ecosystems of this region.

Structure and Dynamics of Korean Red Pine Stands Established as Riparian Vegetation at the Tsang Stream in Mt. Seorak National Park, Eastern Korea

The structure and dynamics of Korean red pine stands established in the riparian zone were studied in the Tsang stream in Mt. Seorak National Park, in east-central Korea. Pine stands were classified into four successional stages, the initial, establishing, competitive, and stabilizing stages, based on the age distribution of a dominant tree, Pinus densiflora, the vegetation stratification, and the microtopography of the riverine environment. The stages usually corresponded to disturbance frequencies, depending on the horizontal and vertical distances from the watercourse. Stands of the initial and establishing stages lacked tree or subtree layers, or both. As stands progressed through the developmental stages, soil particle size became finer and moisture retention capacity was improved. The stand ordination reflected the developmental stage, and the species ordination differentiated species specializing in relatively dry and wet habitats. The results of the analysis of vegetation dynamics provided ecological information which will be useful for understanding the developmental processes of vegetation established in riparian zones. Species diversity indices usually increased across developmental stages, following the typical pattern for successional processes. We discuss the importance and necessity of riparian vegetation in Korea, where most riparian forests have disappeared due to excessive human land use.

Risk from Sirococcus conigenus to understory red pine seedlings in northern Wisconsin

SummaryInterest in development of multicohort stands of red pine (Pinus resinosa) in the Great Lakes region of North America prompted an investigation of the potential impact of the shoot blight pathogen Sirococcus conigenus (syn. S. strobilinus) on understory red pine seedlings. In May 2002 and 2003 healthy, 1‐year‐old red pine seedlings were planted in the understory of a maturing red pine plantation in northern Wisconsin in an area with a history of presence of this pathogen. Occurrence of shoot blight symptoms was recorded periodically during the summer, and in each year seedlings were harvested in fall and examined for signs of shoot blight pathogens. By fall 2002 and 2003, respectively, shoot blight incidence was 89% and 98% and most seedlings were dying. Pycnidia with conidia of S. conigenus were present on almost all of the symptomatic seedlings. The conifer shoot blight and canker pathogen Diplodia pinea (syn. Sphaeropsis sapinea) was also detected, though less frequently. Pycnidia of S. conigenus tended to be found more frequently on symptomatic current year's shoots than symptomatic previous year's shoots; the opposite was true for pycnidia of D. pinea. Risk from S. conigenus to understory red pine seedlings should be considered in any plans for development of multicohort red pine stands in areas where the pathogen is present.

Geostatistical analysis of regional differences in stem taper form of Pinus densiflora in central Korea

AbstractThis study verified regional differences in the stem form of Pinus densiflora Sieb. et Zucc. (red pine) and identified the relationship between stem form and climatic factors in the central region of the Korean peninsula. Regional differences in stem form index at tree base (butt) and top stem section were found. Compared to the stem form in the eastern uplands, the stem form in the western lowlands could be characterized by a more conical butt section and more cylindrical middle and upper section. Through geostatistical analysis of kriging and spatial regression, several climatic factors proved to exert a meaningful influence on stem taper form. On the stem form at the butt section, the precipitation during the late growing season exerts statistically significant effects. High precipitation during the growing season in the western lowland and coastal region causes the stem form at the butt section to be more tapered. On the stem form at the middle and upper section, temperature and precipitation during the growing season, and wind during the late growing season have statistically meaningful influences. High temperature, precipitation, and wind during the growing season in the western lowland and coastal region jointly influence the stem form at the middle and upper sections which result in more cylindrical profiles. This study can be considered an initial investigation into the factors controlling stem form variability in the central region of the Korean peninsula. The results can be used to develop more accurate regional stem taper models needed for reasonable management of red pine stands in different regions.

Armillaria species on small woody plants, small woody debris, and root fragments in red pine stands

The incidence of Armillaria on small woody plants, small woody debris, and root fragments was estimated in red pine (Pinus resinosa Ait.) stands in northeastern Minnesota. Soil core samples 10 cm in diameter, and extending to a depth of either 16 or 25 cm, were collected from 13 stands belonging to three age-classes. Half of the youngest stands had been treated using herbicide. Mycelial fans or rhizomorphs of Armillaria were observed on 13% of the small woody plants and isolated from 8% of them. Including small woody debris and root fragments, 38% of 0–16 cm deep samples had Armillaria. Armillaria was observed on 3% and isolated from 1% of individual substrate units from 0 to 25 cm deep samples. Within a single stand, 0%–67% of the samples and 0%–9% of the individual units had evidence of Armillaria. All but one isolate were Armillaria ostoyae (Romagn.) Herink. Herbicide-treated and untreated red pine stands had similar Armillaria incidence, and there was a trend of incidence inversely related to stand age-class. Large numbers of small woody plants, woody debris, and root fragments were found in red pine stands; varying percentages of these substrates were contributing to the survival of Armillaria and could also be serving as sources of root disease inoculum.