Growth and physiological response of eastern white pine seedlings to partial cutting and site preparation

We examined how white pine (Pinus strobus L.) seedlings planted under a mature cover of white and red (Pinus resinosa Ait.) pine in eastern Ontario (Canada) responded to treatments aimed at improving light and soil conditions for seedling growth. The treatments were: (a) three levels of partial cutting (no cut or CS0, cut to one-crown spacing between residual trees or CS1, cut to two-crown spacing or CS2); (b) two levels of vegetation control (without herbicide or H0, with herbicide or H1); and (c) two levels of soil scarification (S0 and S1). On the third growing season after planting, total growth of seedlings was lowest in CS0 treatment and similar in CS1 and CS2 treatments. The CS2 created better growing light conditions than the CS1, with and average of 50% of full light at seedling height, which corresponded to the maximum height and diameter growth rates of seedlings. However, CS2 also stimulated the growth of competing woody vegetation (both understory trees and shrubs), and resulted in greater microsite heterogeneity of light availability. Scarification warmed the soil (approximately 1–3 °C in the middle of the growing season), decreased the density of competing trees, but increased the shrub density, with no impact on white pine seedling growth. The treatments had no effect on light-saturated photosynthetic rate (A) of current-year foliage of seedlings, nor on their midday shoot water potential. Leaf N was higher in partial cuts and with vegetation control, but the relationship between N and A was weak to non-existent for the different foliage classes. Measures of the proportion of aboveground biomass allocated to foliage (leaf-mass ratio) suggest an acclimation response of young white pine that improves growth under moderate light availability and compensates for the lack of leaf-level photosynthetic plasticity. We suggest a combination of soil scarification under a one-crown spacing partial cut (corresponding to 14 m² ha⁻¹ of residual basal area, or an average of 32% of available light at seedling height) as an establishment cut. This should provide optimum growth conditions for planted understory white pine, while also favoring natural regeneration and providing some protection against damage from insects and disease.     

Comparative mast seed production in unmanaged and shelterwood white pine (Pinus strobus L.) stands in central Ontario

The effect of the seed cut of the uniform shelterwood silvicultural system on white pine seed production, seed characteristics, and seed viability during 2 mast seeding events was examined in operationally harvested second growth, white pine-dominated forest stands in central Ontario. Seed traps placed along transects in unmanaged and shelterwood stands in each of 3 blocks were used to monitor seed production in 2000 and 2006 (4 and 10 years after harvesting). During these 2 mast seed years between 386,000 and 2,730,600 seed ha^?1 were produced among study stands. Total seed production expressed on a per hectare and unit pine basal area basis did not differ by harvest treatment or among blocks in either year. Variability in seed production among stands was primarily due to differences in stand structure, with seed production positively related to white pine basal area. Seed characteristics were largely similar between harvested and unmanaged stands and between seed years. Seed viability was relatively high in both years, with seed from shelterwoods germinating slightly slower than those from unmanaged stands. Seed quality, as estimated by laboratory germination performance, was higher in 2006 than 2000, likely due to improved seed development and maturation in the warmer, wetter growing season of 2006. Our results suggest that the seed cut of the uniform shelterwood system applied to second growth white pine stands is unlikely to adversely affect white pine seed production, seed quality, or potential for natural regeneration during mast seeding events.     

Long-term effects of stump harvesting on soil properties and tree growth in Scots pine and Norway spruce stands

Abstract

Effects of stump harvesting on the properties of surface soil and on the density, structure and growth of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) stands were estimated in a field trial in western Finland. The experiment was established in 1977 and measured in 2010. Stems and logging residues were harvested after clear-cutting, and stumps were lifted and removed from half of the experimental area. Sixteen plots were planted with pine seedlings and 16 with spruce. The main effects of stump harvesting were improved survival of planted trees and an increase in natural regeneration. No clearly negative effects were noted in the stand development. Stump harvesting had no or minimal effects on the properties of the organic layer and those of the 0- to 10-cm mineral-soil layer. Soil properties did not differ between tree species. Pine production was higher on plots with stump removal compared to plots without soil treatment.     

The effects of herbaceous and woody competition on planted white pine in a clearcut site

We investigated the effects of herbaceous and woody vegetation control on the survival and growth of planted eastern white pine (Pinus strobus L.) seedlings through six growing seasons. Herbaceous vegetation control involved the suppression of grasses, forbs, ferns, and low-shrubs, and was maintained for 0, 2, or 4 years after white pine seedlings were planted. Woody control involved the removal of all tall-shrub and deciduous trees, and was conducted at the time of planting, at the end of the second or fifth growing seasons, or not at all. Seedling height and basal diameter responded positively and proportionally to duration of herbaceous vegetation control. Gains associated with woody control were generally not significant unless some degree of herbaceous vegetation control was also conducted. Only herbaceous control increased pine crown closure and rate of crown closure. Herbaceous control and the presence of 5000–15,000 stems per ha of young overtopping aspen were associated with reduced weevil (Pissodes strobi Peck.) injury and increased pine height growth. The study suggests that white pine restoration strategies on clearcut sites should focus on the proactive, early management of understory vegetation and the gradual reduction of overtopping cover from woody vegetation to create a seedling light environment that supports acceptable growth with minimal weevil damage.     

Recruitment of tree species in mixed selection and irregular shelterwood forest stands

Context

Recruitment is an important process in forest stand dynamics, especially in uneven-aged stands. Continuous recruitment is a prerequisite for diverse, uneven-aged silvicultural systems, but patterns may vary significantly.

Aims

The main goals of the study were to examine the recruitment of the main tree species in selection and irregular shelterwood stands in silver fir?CEuropean beech?CNorway spruce forests and to determine the main predictors of the recruitment occurrence.

Methods

Data from 5,486 permanent inventory plots were used to study recruitment of saplings into the tree layer (diameter at breast height ??10?cm).

Results

Recruitment rate differed significantly between selection (7.6?trees?ha^?1?year^?1) and irregular shelterwood (26.1?trees?ha^?1?year^?1) stands. Shade-tolerant fir and beech recruited with higher probability in selection stands, while light-dependent sycamore recruited with higher probability in irregular stands. In addition, forest types, soil pH, stand basal area, mean diameter, and the basal area of the same tree species with respect to recruitment were found to be important predictors of recruitment occurrence.

Conclusions

The application of different uneven-aged silvicultural systems and their forms makes it possible to considerably influence the future tree species composition of uneven-aged forests.     

Long-term effects of single prescribed fires on hardwood regeneration in oak shelterwood stands

One of the arguments against using prescribed fire to regenerate oak (Quercus spp.) forests is that the improvement in species composition of the hardwood regeneration pool is temporary and multiple burns are necessary to achieve and maintain oak dominance. To explore this concern, I re-inventoried a prescribed fire study conducted in the mid-1990s to determine the longevity of the effects of a single prescribed fire on hardwood regeneration. The initial study was conducted in three oak shelterwood stands in central Virginia, USA. In 1994, each stand was divided into four treatments (spring, summer, and winter burns and a control) and the hardwood regeneration was inventoried before the fires. During the burns, fire intensity was measured and categorized in each regeneration sampling plot. Second-year postfire data showed marked differences in species mortality rates, depending on season-of-burn and fire intensity: oak and hickory (Carya spp.) regeneration dominated areas burned by medium- to high-intensity fire during the spring and summer while yellow-poplar (Liriodendron tulipifera) and red maple (Acer rubrum) seedlings dominated unburned areas and all areas treated with low-intensity fire regardless of season-of-burn. The treatments were re-inventoried in 2006 and 2007 to determine whether these fire effects were still present. The new data show that the species distributions by season-of-burn and fire intensity found in 1996 still existed 11 years after the treatments. The fact that fire effects in oak shelterwood stands can last at least a decade has important management implications for resource professionals interested in sustaining oak forests in the eastern United States.     

Tree regeneration and future stand development after bark beetle infestation and harvesting in Colorado lodgepole pine stands

In the southern Rocky Mountains, current mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreaks and associated harvesting have set millions of hectares of lodgepole pine (Pinus contorta var. latifolia Engelm. ex Wats.) forest onto new stand development trajectories. Information about immediate, post-disturbance tree regeneration will provide insight on dynamics of future stand composition and structure. We compared tree regeneration in eight paired harvested and untreated lodgepole pine stands in the Fraser Experimental Forest that experienced more than 70% overstory mortality due to beetles. New seedlings colonized both harvested and untreated stands in the first years after the beetle outbreak. In harvested areas the density of new seedlings, predominantly lodgepole pine and aspen, was four times higher than in untreated stands. Annual height growth of pine and fir advance regeneration (e.g., trees established prior to the onset of the outbreak) has doubled following overstory mortality in untreated stands. Growth simulations based on our regeneration data suggest that stand basal area and stem density will return to pre-beetle levels in untreated and harvested stands within 80-105 years. Furthermore, lodgepole pine will remain the dominant species in harvested stands over the next century, but subalpine fir will become the most abundant species in untreated areas. Owing to terrain, economic and administrative limitations, active management will treat a small fraction (<15%) of the forests killed by pine beetle. Our findings suggest that the long-term consequences of the outbreak will be most dramatic in untreated forests where the shift in tree species composition will influence timber and water production, wildfire behavior, wildlife habitat and other forest attributes.     

Evaluation of promoters and visual markers for transformation of eastern white pine

This report serves to evaluate possible promoters for use in theproduction of transgenic eastern white pine (Pinus strobus L.).Embryogenic cultures of eastern white pine were bombarded with goldparticles coated separately with a variety of gene constructs containingthe UidA -glucuronidase (GUS) or green fluorescentprotein (GFP) reporter gene. Transient expression of the UidAgene, driven by a novel algal virus adenine methyl transferase genepromoter, as well as five other promoters used in angiospermtransformation, were evaluated. The maize alcohol dehydrogenase promoterwas not effective in eastern white pine cultures. The construct with thedoubled Cauliflower Mosaic Virus 35S promoter plus Alfalfa Mosaic Virusenhancer showed the highest levels of expression. GUS expression wasdetected within 24 hours, but decreased after 5 days and was notdetectable 15 days after bombardment. Expression of GUS activity wasrecorded mainly in somatic embryonal heads of various stages ofdevelopment and occasionally in suspensor cells. Similar to GUSexpression, modified green fluorescent protein (GFP) was detected in theembryonal head cells 24 hours after bombardment. GFP-expressingsuspensor cells were both more infrequent and difficult to detect, astheir highly vacuolate nature rendered the GFP presence less visibleagainst the yellow background autofluorescence.     

Determination of elements removal in different harvesting scenarios of Scots pine (Pinus sylvestris L.) stands

Increasing demand for renewable energy and limiting CO₂ emissions have stimulated much interest in wood-based biofuels. Unfortunately, expanding the utilization of forest biomass may cause nutrient depletion in forested environments. This study investigates the element content from various parts of the tree. Comparisons were made between different harvesting scenarios and their impact on the amount of nutrients removed from the forest environment. The harvesting scenarios were: stem-only harvesting (SOH), branch and stem harvesting (BSH), and two variants of whole-tree harvesting (WTH). The elements taken into account were: carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), sulphur (S), copper (Cu), iron (Fe), nickel (Ni), manganese (Mn), zinc (Zn), cadmium (Cd), chromium (Cr) and lead (Pb). To make the results comparable, the same amount of removed biomass was taken into calculation. The differences between harvesting scenarios were significant. The amounts of removed elements formed similar pattern: the lowest level was found in SOH, average in BSH, and highest in both variants of WTH. This confirms that the application of WTH is connected with increased risk of nutrient depletion, even when the volume of harvest would be equal to other variants.     

Twenty year site preparation effects on sub-boreal lodgepole pine performance

We examined the effects of various mechanical site preparation methods and windrow burning on container-grown planted lodgepole pine (Pinus contorta var. latifolia) survival and growth for 20?years after treatment at a sub-boreal site in north-central British Columbia, Canada. Survival was uniformly high (??80%) regardless of treatment, indicating that site preparation was not necessary to establish pine on this site. Significant treatment effects on height, diameter, and stem volume were present at all assessment dates, but only the windrow burning treatment was associated with growth gains over the untreated control after two decades. Pine planted at the disk trench hinge were significantly larger than control pine only until year five. Of the mechanical treatments, only coarse mixing (by bedding plow) continued to have a significant effect on pine growth for as many as 9?years after treatment. Despite the disappearance of significant differences between mechanical treatments and the untreated control by year 20, the magnitude of stand volume increases suggests the potential for mechanical site preparation to have a beneficial effect on future timber supply. Repeated measures analysis confirmed that trends in early diameter growth differed between the untreated control and the windrow burning or coarse mixing treatments. These data are also potentially valuable for verifying growth and yield or carbon budgeting modelling tools.     

Long-term soil and shortleaf pine responses to site preparation ripping

A shortleaf pine (Pinus echinata Mill.) ripping study was established by the Missouri Department of Conservation in March 1988 at the Logan Creek Conservation Area, USA. The objective of the study was to evaluate the effects of ripping on soil chemical and physical properties, on free-to-grow status, and on survival and growth of planted shortleaf pine seedlings. After 16 years, ripping increased exchangeable calcium; however, it had no long-term effects on soil particle size, organic carbon, pH, exchangeable potassium and exchangeable magnesium. Ripping increased the percentage of free-to-grow saplings by 3.8% after two growing seasons. Ripping improved survival by 4% during the 1st three growing seasons and by 7.1% at age 16. After two growing seasons, ripping improved crown spread by 13.6%, height by 14.2%, diameter by 14%, and volume by 41.2%. At age 16, ripping no longer had an effect on shortleaf pine height and had reduced diameter by 5.3% and volume by 11.0%. Our results suggest that ripping 1) had no effect on long-term physical properties or chemical properties of the soil, 2) had no effect on the number of free-to-grow seedlings, and 3) produced short-term benefits on survival and growth of planted shortleaf pine.     

Use of carbofuran for control of eastern white pine cone and seed insects

The major insects that destroy cones and seeds of eastern white pine, Pinus strobus L., were controlled with soil applications of the systematic insecticide carbofuran in orchards at Murphy and Morganton, NC, U.S.A. Carbofuran applied once a year at rates of 4.5, 9.0 or 13.5 g AI (active ingredient) per cm of diameter at breast height protected trees from the white pine cone beetle, Conophthorus coniperda (Schwarz), the leaffooted pine seed bug, Leptoglossus corculus (Say), the shieldbacked pine seed bug, Tetyra bipunctata (Herrich-Schäffer), and the white pine cone borer, Eucosma tocullionana Heinrich. Control was reflected by increased cone survival and increased yields of filled seeds per cone. Increasing the rate of application from 4.5 to 9.0 or 13.5 g generally improved control, but the improvement was not of statistical or practical significance. Carbofuran was ineffective against a seed chalcid, Megastigmus atedius (Walker). White pine clones varied in inherent susceptibility to insect attacks.     

Effects of clearcutting and site preparation on water yields from slash pine forests

Three operational-sized watersheds in poorly-drained pine flatwoods forests on sandy soils of the Lower Coastal Plain in north Florida were isolated and continuously monitored for more than 3 years. Recording flumes assessed quantity of runoff water. After 1 year of calibration monitoring, two of the watersheds were harvested, site-prepared, and planted under distinct harvest and regeneration practices.Minimum practices, imposed on one watershed, consisted of manual shortwood harvest of pinelands, roller drum chopping of harvest residues and residual understory, bedding, and planting. Maximum practices, imposed on another, consisted of tree length logging of pinelands with heavy equipment, extraction of lightwood stumps, burning and windrowing of logging residue and residual understory, harrowing, bedding, and planting.Both systems increased water yields. Following minimum practices, yield increased intermittently depending on weather. Following maximum practices the increase in water yield was quicker, larger, and more persistent over various seasons and weather conditions. In both cases water yields returned to preharvest levels or less within the year following planting.     

Fine root biomass in relation to site and stand characteristics in Norway spruce and Scots pine stands

Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m(-2), and that of Scots pine ranged between 149 and 386 g m(-2). In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species, resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1 and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway spruce and Scots pine forests.     

Development of oak and beech seedlings planted under varying shelterwood densities and with different site preparation methods in southern Sweden

Effects of site preparation, shelterwood density and planting depth on the survival and growth of planted beech and oak seedlings were studied. Experiments were performed in one oak and one beech stand in southern Sweden. Two areas with different densities of shelterwood and one clearcut were established in each stand. Growth, damage and survival of the planted seedlings were observed for three years. Soil water potential was recorded weekly and radiation and soil temperatures were recorded continuously during the growing seasons.Neither site preparation methods nor planting depth affected oak seedling growth, when planting was carried out on fresh clearcuts or in shelterwoods, while growth of beech seedlings was positively affected by mounding. Growth of oak seedlings was inhibited by the shelterwood treatments. In beech seedlings, growth was lowest in dense shelterwood, while there was no difference in growth between seedlings on the clearcut area and in the shelterwood of low density. Differences in growth may be explained by differences in radiation and soil water potential.When planting was carried out on a one-year-old clearcut, site preparation improved the subsequent growth of oak and beech seedlings.     

Stem sapwood permeability in relation to crown dominance and site quality in self-thinning fire-origin lodgepole pine stands

Stem sapwood hydraulic permeability, tree leaf area, sapwood basal area, earlywood to latewood ratio of annual rings, radial variation in hydraulic permeability and stem hydraulic capacity were examined in dominant (D), codominant (CD) and suppressed (SP) lodgepole pine (Pinus contorta Dougl. ex Loud.) trees growing on medium and poor sites. Hydraulic permeability on a sapwood area basis (ks) was lower in suppressed trees (0.71 x 10(-12) m2) compared to dominants (1.97 x 10(-12) m2) and codominants (1.79 x 10(-12) m2), and higher on medium than on poor sites. The leaf/sapwood area ratio (S) varied with crown dominance position (D > CD > SP) but not by site type. Leaf specific conductivity (kL) did not vary between crown classes or site types. The relationship between leaf area and stem hydraulic supply capacity (Q*) was strong, but differed among crown classes. Dominant trees and trees from the medium sites had a greater proportion of earlywood in outer rings of sapwood than suppressed trees. Sapwood permeability declined from the cambium to the sapwood-heartwood boundary in all samples, but the decline was more gradual in dominant trees compared to codominant and suppressed trees; differences in the radial variation in sapwood permeability may be related to differences in S. Sapwood permeability is positively related to crown dominance, whereas subdominant (CD and SP) trees have greater Q* in relation to leaf area, leading us to propose that this may give subdominant trees a survival advantage, slowing self-thinning.