Dominant Pine Research Articles

Effects of climate change on biomass carbon sequestration in old-growth forest ecosystems on Changbai Mountain in Northeast China

Old-growth forest ecosystems are large carbon pools, and recent research has found that old-growth forests generally serve as global carbon sinks. However, the impact of climate change on the capacity for carbon sequestration in old-growth forest ecosystems is uncertain. Combining data from 30-year monitoring of permanent plots with that measuring variations in radial growth of dominant trees in an old-growth forest on Changbai Mountain in Northeast China, this study investigated the net biomass carbon sequestration and the effects of climate warming on carbon sequestration for dominant living trees in this forest ecosystem. The results showed that in 2010 biomass carbon density for living trees was 201.22tha−1 in Korean pine and broad-leaved mixed forest (KBF), 106.46tha−1 in spruce-fir forest (SFF), and 89.49tha−1 in Erman’s birch forest (EBF). During the past 30years the net biomass carbon density has increased in KBF and EBF, with annual net increases of 1.79tha−1 and 1.22tha−1, respectively; while net carbon density has decreased in SFF, with an annual net decrease of 0.55tha−1. Despite the increase of carbon density in KBF, climate warming has contributed to a decrease of 0.96tha−1 in biomass carbon sequestration for the period of 1981–2010, an amount equivalent to 1.8% of total stand biomass carbon increase. The increase in net carbon density in KBF was primarily age- or size-related, since that forest is still maturing. The decreased density in SFF may be caused by climate-induced radial growth decline and mortality of dominant trees in these stands. For the period of 1981–2010, climate-induced decrease of carbon sequestration in SFF was 7.30ha−1. Wind-related tree mortality in SFF may have led to the stand carbon sequestration decrease of 75.09tha−1, about 10.3 times that induced by climate warming. In EBF, climate warming has led to a small increase in stand carbon sequestration, and the increase in net carbon density was also primarily age- or size-related, reflecting the fact that this forest is also still maturing. Our study also suggests that the dominance of Korean pine in KBF will decrease and that of Manchurian ash will increase under continuing climate warming, which is in agreement with the results from previous forest models.

Silvicultural treatments for converting loblolly pine to longleaf pine dominance: Effects on resource availability and their relationships with planted longleaf pine seedlings

Throughout the southeastern United States, land managers are currently interested in converting loblolly pine (Pinus taeda L.) plantations to species rich longleaf pine (Pinus palustris Mill.) ecosystems. In a 3-year study on moderately well- to well-drained soils of the Lower Coastal Plain in North Carolina, we examined the effects of four canopy and three cultural treatments on plant resources and quantified relationships between plant resources and longleaf pine seedling survival and growth. Canopy treatments consisted of four levels of timber harvest applied to loblolly pine stands: Control (uncut, mean basal area of 16.2m2/ha), MedBA (single-tree selection to a mean residual basal area of 9.0m2/ha), LowBA (single-tree selection to a mean residual basal area of 6.4m2/ha), and Clearcut (complete canopy removal). Within each canopy treatment, we applied three cultural treatments designed to benefit the early growth of planted seedlings: no treatment (NT), herbicide (H), and herbicide plus fertilization (H+F). Gap light index (GLI) significantly differed among canopy treatments and nonlinearly increased with decreasing basal area. The H treatment resulted in higher temperatures at 10cm in the soil. Canopy thinning increased foliar calcium (Ca) concentration. The annual root collar diameter (RCD) increment of planted longleaf pine seedlings was positively correlated with GLI, and foliar phosphorus (P) and Ca concentrations but was negatively correlated with soil moisture. Our results confirm that light is an important factor controlling the growth of longleaf pine seedlings.

Silvicultural treatments for converting loblolly pine to longleaf pine dominance: Effects on planted longleaf pine seedlings

A field study was installed to test silvicultural treatments for establishing longleaf pine (Pinus palustris Mill.) in loblolly pine (P. taeda L.) stands. Harvesting was used to create seven canopy treatments, four with uniformly distributed canopies at different residual basal areas [Control (16.2m2/ha), MedBA (9.0m2/ha), LowBA (6.4m2/ha), and Clearcut (0m2/ha)] and three circular gaps defined by area [LG (∼5281m2), MG (∼3217m2), and SG (∼1576m2)]. Within each canopy treatment, we applied three cultural treatments designed to benefit planted seedling early growth: no treatment (NT), herbicide (H), and herbicide plus fertilization (H+F). Three growing seasons after planting, seedling survival significantly differed among canopy treatments; compared to Controls, Clearcut plots had higher survival (80.6%). H and H+F treatments did not affect seedling survival in the first two years after application. Canopy removal generally increased seedling root collar diameter (RCD) but interacted with cultural treatments. NT within Controls had the smallest RCD, and H+F within Clearcuts had the largest RCD. Canopy treatments significantly affected the percentage of seedlings in height growth (i.e., terminal bud >15cm high); Control plots had a significantly lower percentage of seedlings in height growth than other canopy treatments. H and H+F treatments also significantly increased the percentage of seedlings in height growth when compared to NT. Our results indicate that canopy removal improves early establishment of longleaf pine seedlings and that herbicides may additionally be used to increase early longleaf pine seedling growth. Our results are similar to those reported in previous studies conducted in mature longleaf pine stands.

Alternative sampling methods to estimate structure

Aleppo pine had a large forest cover in North Africa and along the Mediterranean basin which management is not fully developed and new forest tools are required. In this research, the forest structure, epidometric characteristics and allometric relationships were studied in 79 plots covering four bioclimatic zones from natural even aged forests of Aleppo pine located between eastern Algeria to the western coastal part of Tunisia. To characterize the forest structure three sampling methods were carried out: classical inventories (recording all pine trees), and two simplified approach using one average size or five dominant pine tree per plot. Annual growth increment and cone production were only calculated for the average size tree. Furthermore, the analysis of variance showed non-significant differences recorded between bioclimatic zones in trunk or crown diameter using the two simplified approach. Moreover, a significant decrease from wetter to drier areas in total height, crown height, cone seed production was observed only for average size tree method. However, the analysis of covariance showed significant differences between both approaches in total height, trunk diameter and crown coverage which were largely influenced by the pine tree density. In future investigations, we confirmed previous research that the dominant tree is a good sampling method to examine the site fertility, whereas the average size tree constitutes a valuable approach to study the population growth and reproduction.

Alternative sampling methods to estimate structure

Aleppo pine had a large forest cover in North Africa and along the Mediterranean basin which management is not fully developed and new forest tools are required. In this research, the forest structure, epidometric characteristics and allometric relationships were studied in 79 plots covering four bioclimatic zones from natural even aged forests of Aleppo pine located between eastern Algeria to the western coastal part of Tunisia. To characterize the forest structure three sampling methods were carried out: classical inventories (recording all pine trees), and two simplified approach using one average size or five dominant pine tree per plot. Annual growth increment and cone production were only calculated for the average size tree. Furthermore, the analysis of variance showed non-significant differences recorded between bioclimatic zones in trunk or crown diameter using the two simplified approach. Moreover, a significant decrease from wetter to drier areas in total height, crown height, cone seed production was observed only for average size tree method. However, the analysis of covariance showed significant differences between both approaches in total height, trunk diameter and crown coverage which were largely influenced by the pine tree density. In future investigations, we confirmed previous research that the dominant tree is a good sampling method to examine the site fertility, whereas the average size tree constitutes a valuable approach to study the population growth and reproduction.

Growth Sensitivity to Drought of Co-OccurringPinusspp. along an Elevation Gradient in Northern Mexico

Climate change is predicted to increase the frequency of severe drought, yet little information exists on the impacts of drought on dominant trees of Mexican pine forests, which are among the most biologically diverse forests in the world. We conducted the first comparison of growth sensitivity to drought of two co-occurring Pinus species in Mexico to understand whether growth of dominant pines of the Sierra Madre Occidental in northern Mexico is sensitive to drought and temperature variation and to understand how sensitivity differs between tree species and elevations. We sampled and analyzed tree-ring data across a 400-m elevation gradient for the years 1945–2004 for co-occurring Pinus engelmannii and Pinus lumholtzii at Basaseachi National Park, Chihuahua, Mexico. We hypothesized that growth sensitivity to drought would be highest at low elevations, annual basal area increment (BAI) would be lowest at low elevations, and winter precipitation would covary positively with BAI at all elevations. Growth sensitivity to drought, as measured by a wet-dry ring-width index ratio (W:D), was significantly higher for both species at low elevations (W:D range 2.2–2.8) than at intermediate and high elevations (WD range 1.5–1.9). Pinus engelmannii had significantly higher W:D (2.2) than P. lumholtzii (1.8). Annual BAI did not differ between elevations or species. Annual ring—width index was positively and significantly associated with winter (December–April) precipitation. This association was stronger at low elevations than at high elevations. Other seasons of precipitation and other climatic variables were not significantly associated with annual growth. Our results suggest that the increasing frequency and severity of drought predicted for this region in the coming decades will reduce growth of P. engelmannii and P. lumholtzii, with greater impacts on low-elevation populations and on P. engelmannii.

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 m 2/ha), MedBA (residual basal area of ∼9 m 2/ha), LowBA (residual basal area of ∼6 m 2/ha), and Clearcut (complete canopy removal)) and to different positions within canopy gaps (approximately 2800 m 2) 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.

Carbon Sequestration in the New Jersey Pine Barrens Under Different Scenarios of Fire Management

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

The effects of species mixture on the growth and yield of mid-rotation mixed stands of Scots pine and silver birch

The effect of tree species mixture on stand volume yield and on tree-species-specific diameter and height growth rates were analysed in managed mixed stands of Scots pine ( Pinus sylvestris L.) and silver birch ( Betula pendula Ehrn.). Data were obtained from 14 repeatedly measured stands located in Southern Finland on mineral soil sites with varying admixture of Scots pine and silver birch. Statistical analysis was carried out for studying the effect of species mixture on the development of stand characteristics. For the analysis, the plots were categorised into three groups (plot types) according to the species dominance. In order to analyse species-specific growth rates, individual-tree mixed linear growth models for tree diameter and height growth were developed for both tree species. The results clearly show that the yield of the managed mid-rotation, mixed stands was greater for stands dominated by Scots pine than for stands dominated by birch, and the stand volume increment decreased with an increasing proportion of silver birch. Analysis of diameter and height growth by tree species revealed that the main reason for this pattern is the negative impact of birch competition on the growth of pine trees. The increase in diameter of pine was clearly hampered if the proportion of birch was high. An abundance of birch also slightly decreased the growth in height of Scots pine, although the effect was less than on diameter growth. Species mixture did not affect the diameter growth of birch but did have a significant effect on height development. Height growth of birch was considerably greater in pine-dominated stands than in birch-dominated stands. In pine-dominated mixed stands, the height growth of birch was quite close to that of dominant pine trees, and birches can endure in competition with pines for light. The results apply for even-aged and single-storey managed stands, where stocking density and structure are controlled with pre-commercial and commercial thinnings. The results are not applicable to unmanaged mixed stands undergoing self-thinning. This study provides new information on mixed stands from a silvicultural perspective, which can be applied in decisions involving the management of mixed stands.

Mid-Holocene vegetation and climatic history of the Iberian Peninsula

The aim of this research is to study the climate and vegetation history in the western Mediterranean, in the Iberian Peninsula, during the middle Holocene through pollen analysis. The origin of the deposits varied from the most xeric to more mesic Mediterranean environments. The timing, extent, and progress of the establishment of the Mediterranean climate have a degree of variability depending on the biogeographical region. Analyses of several pollen sequences reveal climatic transformations in the flora and vegetation between 7000 and 4000 cal. yr BP. Pollen concentrations have been used in some sequences to evaluate the order of magnitude in biomass changes through time. Three main spatial and taxonomic responses could be assumed: (1) in littoral regions, deciduous broadleaf trees were frequently dominant and then replaced by sclerophyllous and evergreen forests; (2) in continental regions and sub-Mediterranean mountains, the dominance of pine throughout the whole Holocene signals a change of less magnitude; and (3) in southeastern semiarid Mediterranean regions, the main changes are reflected by alternation between steppe and shrub communities. The emplacement of the Mediterranean climate is reflected in an aridification process. A temporal first approach of Holocene climatic changes is proposed: a humid phase (12 000—7000 cal. yr BP), a transition phase (7000—5500 cal. yr BP) and an aridification phase (5500 cal. yr BP—Present). According to archaeological data, natural changes in the forests favoured the environments suitable for human settlements, farming and sheepherding.

EcM fungal community structure, but not diversity, altered in a Pb-contaminated shooting range in a boreal coniferous forest site in Southern Finland

Boreal forests contain diverse fungal communities that form essential ectomycorrhizal symbioses with trees. To determine the effects of lead (Pb) contamination on ectomycorrhizal fungal communities associated with the dominant pine (Pinus sylvestris L.), we surveyed sporocarps for 3 years, analyzed morphotyped ectomycorrhizal root tips by direct sequencing, and 454-sequenced fungal communities that grew into in-growth bags during a 2-year incubation at a shooting range where sectors vary in the Pb load. We recorded a total of 32 ectomycorrhizal fungi that formed conspicuous sporocarps, 27 ectomycorrhizal fungal phylotypes from 294 root tips, and 116 ectomycorrhizal fungal operation taxonomic unit (OTUs) from a total of 8194 internal transcribed spacer-2 454 sequences. Our ordination analyses by nonparametric multidimensional scaling (NMS) indicated that the Pb enrichment induced a shift in the ectomycorrhizal community composition. This was visible as indicative trends in the sporocarp and root tip data sets, but was explicitly clear in the communities observed in the in-growth bags. The compositional shift in the ectomycorrhizal community was mainly attributable to an increase in the frequencies of OTUs assigned to genus Thelephora and to a decrease in the OTUs assigned to Pseudotomentella, Suillus, and Tylospora in Pb-contaminated areas when compared with the control. While the compositional shifts are clear, their functional consequences for the dominant trees or soil ecosystem function remain undetermined.

Natural regeneration of jack pine on clay soils following harvesting and site preparation: Seventh-year results

This study examines the operational feasibility of six treatments to regenerate jack pine (Pinus banksiana Lamb.) naturally without fire following harvesting on clay soils in the southeastern boreal forest of Quebec. The experiment is a randomized complete block design. Techniques used were a final cutting in 1993 with manual on-site delimbing or roadside delimbing combined with three methods of soil scarification (WadellTM, La TaupeTM and a control) performed in the Spring of 1994 compared to an adjacent jack pine plantation established in 1994 after Wadell scarification. Seven growing seasons later, the present article compares stand composition, competing vegetation, regeneration and growth of jack pine between the different treatments as well as an adjacent plantation. Natural regeneration produced mixed stands with an adequate 52% average jack pine stocking. Roadside and on-site delimbing produced similar jack pine stocking on average. However, the plantation showed 83% stocking and better performance than natural regeneration in terms of height (2.48 m vs. 1.7 m for natural regeneration), diameter (41 mm vs. 22 mm for natural regeneration) and jack pine dominance. Therefore, if natural regeneration is desired, roadside delimbing is to be recommended since it provides sufficient seed and does avoid early jack pine growth reductions caused by slash. On clay soils, scarification seems to have been optional. Nevertheless, it slightly increased seedling growth and in this way, the treatment combining road-side delimbing and an extensive scarification can be an effective jack pine natural regeneration treatment.Key words: Pinus banksiana Lamb., natural regeneration, stocking coefficient, delimbing, scarification, boreal mixed wood, seedlings

Effects of climate, tree age, dominance and growth on δ15N in young pinewoods

Needles, annual rings from basal stem discs and bark of three dominant and three suppressed Pinus pinaster from a 12-year-old pine stand (naturally regenerated after a wildfire) were analysed to study the effects of climate, tree age, dominance, and growth on tree δ15N. Foliar-N concentration in dominant pines (0.780–1.474% N) suggested that soil N availability was sufficient, a circumstance that allowed isotopic discrimination by plants and (greater) differences in δ15N among trees. The δ15N decreases in the order wood (−0.20 to +6.12‰), bark (−1.84 to +1.85‰) and needles (−2.13 to +0.77‰). In all trees, before dominance establishment (years 1–8), the N stored in each ring displayed a decreasing δ15N tendency as the tree grows, which is mainly due to a more “closed” N cycle or an increasing importance of N sources with lower δ15N. After dominance establishment (years 9–12), wood δ15N values were higher in suppressed than in dominant trees (2.62 and 1.46‰, respectively; P < 0.01) while the reverse was true for needles and bark; simultaneously, the absolute amount of N stored by suppressed pines in successive rings decreased, suggesting a lower soil N assimilation. These results could be explained by lignification acting as major N source for needles in suppressed pines because products released and reallocated during lignification are 15N-depleted compared with the source. According to principal component analysis, wood δ15N appears associated with wood N concentration and precipitation during the growing season, but clearly opposed to age, basal area increment and mean temperature in spring and summer.

Evidence of white pine ( Pinus subgenus Strobus) dominance from the Pliocene Northeastern Gulf of Mexico Coastal Plain

Plant fossils from the Citronelle Formation provide a rare window into the Pliocene flora and climate of the northeastern Gulf of Mexico Coastal Plain. Many of the taxa recovered to date inhabit the region today. However, analysis of Pinus pollen grains and fascicles indicates that the dominant pines were members of Pinus subgenus Strobus (i.e., “white pines”). The fascicles have a small, bulbous base lacking a sheath, and bear four or five long, slender needles. These features are typical of white pines. Although macrofossils are rare, 77 to 100% of the dispersed Pinus pollen grains from five localities have sacci continuous with the corpus and verrucae on the cappula, which are characteristics of white pines. This is remarkable, as the northeastern Gulf of Mexico Coastal Plain today is devoid of white pines, and is instead considered a center of diversity for Pinus subgenus Pinus section Pinus subsection Australes. Today, Pinus strobus is the only white pine in the eastern North America and its southernmost distribution only extends into the mountains of Georgia, about 600 km north of the fossil sites. The historical biogeographic relationships of P. strobus to other North American forms are unclear. For example, its close relative, Pinus chiapensis, is present in northeastern Mexico and Central America. The current disjunction between P. strobus and P. chiapensis is 2400 km and includes an arid barrier to dispersal. P. chiapensis is also associated with several other species showing a similar biogeographic pattern. The fossils described here indicate that white pines were more widespread in North America in the recent geological past than previously thought, and imply possible connections between disjunct species that would not be suspected if only current species' ranges and ecological tolerances were considered.

Modelling total volume of dominant pine trees in reforestations via multivariate analysis and artificial neural network models

The paper describes an artificial neural network (ANN) modelling approach for estimating the inside-bark and outside-bark total volume of dominant pine trees (Pinus brutia) in reforestations. Difficulties in modelling total volume are the great number of tree measurements that have to be used and the complex behaviour of the tree-bole growth and its dimensions. A basic novelty in this modelling approach is the reduction and selection of the minimal set of tree measurements by using multivariate analysis, introducing this set to ANN-based models in a way that they should be able to handle such reduced measurements. Furthermore, ANN model training was accomplished using the cascade-correlation algorithm in which the Kalman's learning algorithm is embedded. The selected ANN models provided unbiased predictions and systematically better accuracy compared with conventional regression models. The results demonstrate the superiority of the ANN models, due to their ability to overcome the problems in forest data, such as non-linear relationships, non-Gaussian distributions, multicollinearity, outliers and noise in the data. The ANN-based approach introduced in this study is sufficiently general and should be considered seriously for estimating the inside-bark and the outside-bark total tree volume.

An object-oriented approach to assessing changes in tree cover in the Colorado Front Range 1938–1999

In the wake of numerous catastrophic wildfires, forest management policies have been implemented in recent years in the United States with the goals of reducing fire risk, including the National Fire Plan and the Healthy Forest Restoration Act. A key premise underlying these policies is that fire suppression has resulted in denser forests than were present historically that now have higher fire risk. To evaluate this premise for the northern Front Range, Colorado, we used object-oriented image analysis to compare change in tree cover delineated from historical and modern imagery. Historical photographs from 1938 and 1940 were scanned, orthorectified, and overlaid on Digital Orthoimagry Quarter Quadrangles (DOQQs) from 1999. Using an object-oriented image analysis technique, the photos were then finely segmented and classified into two classes: tree and non-tree. Trees are heterogeneous in appearance in black and white aerial photography, so we employed separate membership functions to identify four visually distinct types: ‘interior forest’, ‘isolated trees’, ‘dark forest’, and ‘edge forest’. Our classification strategy employed spatial relationships between objects in addition to spectral information, so that our classification is fairly robust to variations in illumination. Based on the classification of fine objects, we then calculated the percent tree cover within a larger set of objects for the two time periods. We estimate that average tree density across the study area increased minimally (4%) during the 60-year period, with considerable spatial variation across the landscape. The results of the analysis illustrate that, consistent with independent tree-ring evidence, the highest increase in tree density is in areas characterized by low initial density, south-facing slopes, low elevations, and ponderosa pine dominance. In contrast, the highest elevation areas dominated by mixed conifer and lodgepole pine forests revealed no significant change in tree cover. Furthermore, there is no significant difference between objects dominated by low, medium, and high departure from historical conditions, as classified in the Landfire Fire Regime Condition Class (FRCC) data product. The results of the study can help managers prioritize forest treatments aimed at restoring pre-suppression forest structure.

Evidence for a Waalian thermomer pollen record from the research borehole Heidelberg UniNord, Upper Rhine Graben, Baden-Württemberg

Abstract. A pollen record from the borehole Heidelberg UniNord, in the northern Upper Rhine Graben shows evidence for one of the rare Waalian thermomers. The record may not comprise the complete thermomer it certainly reflects a sort of succession, initiated by sequences with high values of pine and spruce, followed by a dominance of pine, hemlock-spruce and spruce and finished by a dominance of hemlockspruce, oak and hornbeam becomes visible. Pollen percentage values for Tsuga reach 20 % indicating that this taxon is an important forest element. There is a continuous presence of Carya, Pterocarya, Eucommia, Celtis and Ostrya-type. Neighbouring pollen records reveal similar patterns. The pollen diagram is closely related with the Waalian profiles Leerdam and Eindhoven from the Netherlands.

Site-related influences on cone-borne inoculum and asymptomatic persistence of Diplodia shoot blight fungi on or in mature red pines

The shoot blight and canker pathogens Diplodia pinea and D. scrobiculata sporulate abundantly on cones of many pine hosts. Variation in incidence and abundance of potential inoculum from cones and frequency of asymptomatic persistence on or in shoots was examined for mature red pines in sites differing in dominant presettlement vegetation and soil type in Bayfield and Douglas counties in northern Wisconsin. Collections were made in each county from 6 plantations, 3 each in areas historically vegetated with jack pine and soils mapped as sands and three in areas historically vegetated with red pine with soils mapped as loamy sands. At each site, 5 cones were collected from each of 5 red pines and 10 shoots were collected from up to 5 red pines. Conidia from cones were quantified with a water wash and filtration technique. Diplodia species were cultured from surface-disinfested asymptomatic shoots. A species-specific PCR assay was used to identify the Diplodia species from cones and shoots. Although cones and asymptomatic shoots from each county yielded D. pinea and D. scrobiculata, D. pinea was detected more frequently. More conidia were obtained from cones from Douglas Co., where there is a history of severe shoot blight damage, than cones from Bayfield Co. In Douglas Co., more conidia were obtained from cones from plantations in areas of more sandy soil and presettlement jack pine dominance than cones from plantations in areas of less sandy soil and presettlement red pine dominance. The numbers of conidia and frequencies of cultural detection of Diplodia species from asymptomatic shoots at a site were positively correlated. These results provide evidence for site-related influences on abundance of pathogen inoculum and asymptomatic persistence on or in red pine crowns that may contribute to differences in frequency and severity of damage from Diplodia shoot blight.

Characterizing structural conditions in mature managed red pine: Spatial dependency of metrics and adequacy of plot size

Restoration of the range of forest types and stages that once composed the landscape mosaic of the Upper Great Lakes region of North America will involve manipulating managed red pine stands to recreate now rare structural conditions. Because many of the attributes used to characterize structural condition depend upon spatial arrangement, sampling schemes to assess condition must match sampling extent to attribute variability. To evaluate the metrics and scales appropriate for characterizing structural complexity in managed red pine, we applied metrics that incorporated one-, two-, and three-dimensional structural attributes to eight 1.0 ha mature stem-mapped stands. Most metrics were also calculated within simulated moving windows of 0.05–1.0 ha in sampling extent (“plot size”) within each stand. Two standards were used to evaluate the adequacy of plot sizes for these metrics: (1) estimates were precise, varying less than 10% among moving windows for a given scale, and (2) estimates were accurate to within 10% of the 1.0 ha value at both the 5th and 95th percentiles of the moving window distributions. Necessary sample sizes to achieve precise and accurate estimates were also calculated for each scale. Stands were relatively homogeneous in metrics commonly used in traditional timber management (basal area, mean diameter, total density), which were precisely and accurately estimated in 0.50 ha or larger plots. Metrics capturing attributes associated with old stands (number of large trees, number of snags) were more variable and required larger plots sizes (0.75–1.0 ha). A single 0.50 ha plot would be adequate to estimate mean tree size, the variation in tree size, basal area, and the density of all trees, but the minimum plot size for characterizing structural attributes commonly associated with old-growth appears to be 0.75–1.0 ha in managed red pine. The two-dimensional spatial arrangement (Ripley’s K) and the structural complexity index (SCI) were satisfactorily estimated in plots of 0.50 ha in extent. These early transition phase stands were characterized by smaller trees, greater red pine dominance, density-dependent dispersion, and lower SCI than old-growth. This suggests that relatively large plot sizes may be necessary to evaluate structural condition of stands with increasingly “old-growth” structural conditions.

Forest composition following overstory mortality from southern pine beetle and associated treatmentsExperiment Station Project 06-08-109 of the Kentucky Agricultural Experiment Station, Lexington, Kentucky.

Bark beetle caused mortality continues to play a critical role in determining the composition and structure of forests in North America, and revegetation dynamics following these disturbances are poorly understood. We assessed forest composition following southern pine beetle, Dendroctonus frontalis Zimmermann, mortality and associated cut and leave suppression, and compared them with undisturbed loblolly pine, Pinus taeda L., stands in Texas. Abundant hardwood regeneration dominated the understory, with little loblolly pine regeneration following either mortality event. Disturbances eliminated loblolly pine dominance in these even-aged stands, thus stratifying forest structure and apparently increasing stem density (stems·ha–1), richness (species·ha–1), and diversity (ha) in the lower strata. Aspect and elevation, presumably through influences on site moisture, were the primary gradients associated with vegetation variation in the canonical correspondence analyses for new regeneration. Mortality from Dendroctonus and cut and leave practices shifted loblolly pine communities to mixed upland hardwoods in model predictions generated by the southern variant of the Forest Vegetation Simulator. In addition to being an effective bark beetle control, cut and leave suppression did not alter predicted forest composition 50 years hence when compared with unsuppressed bark beetle-caused mortality. Because of the predicted shift to hardwood domination and a low pine basal area, it is expected that mortality from D. frontalis and cut and leave will substantially reduce future hazards from D. frontalis outbreaks.