Crown architecture of understory and open-grown white pine (Pinus strobus L.) saplings

Crown architecture and growth allocation were studied in saplings of eastern white pine (Pinus strobus L.), a species classified as intermediate in shade tolerance. A comparison was made of 15 understory saplings and 15 open-grown saplings that were selected to have comparable heights (mean of 211 cm, range of 180-250 cm). Mean ages of understory and open-grown trees were 25 and 8 years, respectively. Understory trees had a lower degree of apical control, shorter crown length, and more horizontal branch angle, resulting in a broader crown shape than that of open-grown trees. Total leaf area was greater in open-grown saplings than in understory saplings, but the ratio of whole-crown silhouette (projected) leaf area to total leaf area was significantly greater in understory pine (0.154) than in open-grown pine (0.128), indicating that the crown and shoot structure of understory trees exposed a greater percentage of leaf area to direct overhead light. Current-year production of understory white pine was significantly less than that of open-grown white pine, but a higher percentage of current-year production was allocated to foliage in shoots of understory saplings. These modifications in crown structure and allocation between open-grown and understory white pine saplings are similar to those reported for more shade-tolerant fir (Abies) and spruce (Picea) species, but the modifications were generally smaller in white pine. As a result, white pine did not develop the flat-topped "umbrella" crown structure observed in understory fir and spruce, which approaches the idealized monolayer form that maximizes light interception. The overall change to a broader crown shape in understory white pine was qualitatively similar, but much more limited than the changes that occurred in fir and spruce. This may prevent white pine from persisting in understory shade as long as fir and spruce saplings.     

Regeneration patterns of Eastern white pine (Pinus strobus L.) in hardwood-dominated forests in Virginia, USA

Eastern white pine (Pinus strobus L.) is a moderately shade-tolerant species that co-occurs with hardwood tree species in many forests of the eastern United States, as well as in pure stands. The species is valued for its timber, as well as for wildlife and recreation. Regeneration of this species is somewhat unpredictable and often occurs in patches of similarly-aged cohorts. We described the regeneration patterns of this species and examined their relation to environmental variables within hardwood forests of southwestern Virginia, USA. An average of 5.3 white pine patches per ha were observed in this study. The majority of patches consisted of saplings (85%), with 9% of patches in pole size classes, and 6% in seedling size classes. The average density of patches was 43.5 stems with an average age of 20 years. The size of patches averaged 80.6 m². The total density of seedlings and the number of regeneration patches of all sizes of regeneration (seedlings, saplings, and poles) in plots was related to the surrounding density of large white pine trees (potential seed trees). The density of seedlings or patches was not significantly related to current vegetation cover or soil surface cover variables, but more than half of regeneration patches were located in or adjacent to old canopy gaps, most of which were old logging gaps. While seedling regeneration may occur within the understory of these forests near seed trees, advancement to the sapling and pole stage appears to be associated with canopy gap formation.     

Effects of soil organic matter,moisture, shading and ash on white pine (Pinus strobus L.) seedling emergence

The effects of soil organic matter, soil moisture, shading and ash on white pine (Pinus strobus L.) emergence were investigated using soil monoliths in greenhouse experiments. White pine seedling emergence increased with soil organic matter removal, and levelled with the elimination of the litter and fermentation layers, where seedling emergence did not significantly increase further. Increased shade and soil moisture levels also improved seedling emergence whereas ash had no or little impact on white pine seedling emergence. The silvicultural implications of these findings are discussed with regard to white pine management.     

Estimating seed quantity and quality in shortleaf pine (Pinus echinata Mill.) cones from natural stands

The quantity and quality of seeds were studied in 886 shortleaf pine cones collected from 48 trees in each of two 15-ha natural stands in western Arkansas, USA. The number of seeds per cone ranged from 0 to 102, and averaged 34.6 and 38.0 in the two stands. Between 30 and 50 percent of the seeds were sound. Overall mean values for total number and total sound seeds compare with previous work. However, the wide variation between individual trees in a stand needs to be considered when evaluating cone abundance and estimating potential seed yields. For the stands observed in this study, a sample of 65 to 85 cones would be needed to estimate the number of sound seeds per cone (within ±3 seeds) with 95 percent probability. Sampling 1 or 2 cones from each of about 3 trees per ha would provide a reliable estimate of sound seed contents.     

Thinning increases cone production of stone pine (Pinus pinea L.) stands in the Northern Plateau (Spain)

Context

Edible stone pine (Pinus pinea L.) nut is a forest product which provides the highest incomes to the owners of stone pine forests.

Aim

The objective of this work is to evaluate the effect of first thinning on growth and cone production in an artificially regenerated stand in order to determine optimum intensity.

Methods

A thinning trial was installed in 2004 to compare two thinning regimes (heavy and moderate) and a control treatment. From 2004 to 2012, six inventories of forest attributes were carried out, and the cone crop was harvested annually. We evaluated the effect of thinnings on growth using repeated measures analysis of variance with a mixed model approach. With regards to cone production, we first estimated the probability of finding cones in a tree by applying a generalized mixed model and then estimated cone production by using a mixed model, including climatic variables.

Results

We found that thinning had a positive influence on tree diameter increment. Thinning increased the probability of finding cones and cone production. However, significant differences between heavy and moderate thinnings were not found.

Conclusion

We recommend early silvicultural treatments in stone pine stands to favor the development of trees and larger edible pine nut production.     

Correlations between needle and shoot growth characteristics in Scots pine (Pinus sylvestris L.) stands

Shoot, needle and bud growth in three stands of different ages(9, 20, and 60 years) of Scots pine were studied in order toreveal relations between these variables. Within the growingseason the sizes of buds and needles developed in parallel.Significant regressions between number of short shoots and eitheraverage needle length or total needle length of the parent shootwere found. The strongest regressions were found in the twoyoungest stands as well as in the top of the canopy.     

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

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

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.     

Spatial structure of semi-natural and plantation stands of Scots pine (Pinus sylvestris L.) in northern Scotland

The success of current initiatives to maintain and enhance thearea of and the special habitats provided by the remnant semi-naturalpinewoods of northern Scotland will depend upon foresters' abilityto foster more natural structures in even-aged plantations throughstand manipulation. However, there is little information onthe structures and spatial patterns that can be found in Scottishpinewoods; such knowledge could be used to design appropriatesilvicultural regimes. A study was carried out to compare spatialstructure in three 0.8–1.0 ha plots in the CairngormsNational Park; one plot was a 78-year-old plantation stand,the other two were semi-natural stands with trees up to 300years old. Basic mensurational data showed that the semi-naturalstands were characterized by a wider range of tree sizes andmore large (>50 cm d.b.h.) trees. Spatial structure was evaluatedwith a range of different indices: the aggregation index ofClark–Evans (CE), the uniform angle and diameter differentiationindices, Ripley's L function of tree spatial distribution, pairand mark correlation functions and experimental variograms oftree diameter. The CE revealed a regular distribution in theplantation with the semi-natural stands having a random pattern.Further analysis of the latter stands indicated that, in eachcase, the older trees in the stand were regularly distributedwhile the younger ones were clustered. There was little differencein uniform angle values between the stands while the diameterdifferentiation distributions suggested greater variety in diameterwithin the semi-natural stands than in the plantation. The Ripley'sL function showed that trees in the plantation were regularlydistributed at close distances but clustered over wider distances.There were differences in pattern between the semi-natural stands;in one, trees were clustered because the positions of the youngertrees were influenced by past regeneration trials, whereas inthe other stand a random pattern was observed. Similarly, thevariogram indicated widespread homogeneity in diameter withinthe plantation, while the semi-natural stands showed high variationat close spacing because of competition followed by spatialautocorrelation up to 20 m distance. Thereafter, one of thesestands had a very different pattern because of a more intensiveregeneration history. All the indices, apart from uniform angle,were able to discriminate between the plantation and the twosemi-natural stands, but only the more detailed spatial indiceswere capable of identifying differences within the latter. Theimplications of these results for management strategies in plantationsare discussed.     

Effect of magnetic treatment on seed germination of loblolly pine (Pinus taeda L.)

Based on preliminary experiments, the speed of germination (SG) was in general increased for Pinus taeda L. seeds treated with a static magnetic field (B = 150 mT) for 10, 30 and 60 min. Negative impact was obtained for seeds treated with SMF for 24 h and 48 h. Mean germination time (MGT), the SG, and time required to obtain 10%, 25%, 50%, 75%, and 90% of seeds to germinate (T₁₀–T₉₀) were calculated. Results showed a reduction of the MGT and T₁₀–T₉₀ for seeds treated with SMF for 10, 30, and 60 min; therefore, the germination speed was increased. Among various magnetic treatments, loblolly pine seeds treated with S3 (SMF60 min) yielded the peak performance.     

Development of oaks (Quercus petraea (Matt.) Liebl.) emerged from bird-dispersed seeds under old-growth pine (Pinus silvestris L.) stands

In East Germany, there are a lot of areas covered by old pine stands. They are growing on soils, on which under natural conditions without anthropogenic impact mixed stands of oak (Quercus petraea (Matt.) Liebl.) and pine (Pinus silvestris L.), would form a natural forest. An important objective of ecological silviculture in these areas is to convert the pure pine stands into mixed oak–pine stands by using natural regeneration methods. A highly appreciated assistant in this connection is the European jay (Garrulus glandarius L.). The remarkable results of its work have been found by analyzing the natural regeneration in a few old pine stands in the forest district of Weißwasser in Saxony. Although mother trees of oak are very scarce there, natural regeneration of oak was found everywhere in the research area. The oak regeneration, undoubtedly created by the jay, amounted to at least 2000 oaks/ha. They were mainly distributed at random, while pine regeneration was aggregated in places where gaps in the pine canopy occurred. Oak regeneration was established much earlier than pine regeneration. Thus, oaks exceeded pines in age, height and diameter. The oaks were also superior to pines concerning height increment for the last three years. Thus, there is a good chance for oak to defend its prevailing role in the regeneration in the future. Probably, the next forest generation will be composed of oak and pine trees. The analysis of the quality of the oak regeneration shows that there is no substantial difference to artificially sown oak stands. This indicates that the European jay creates oak stands sufficiently both in number and quality.     

Natural Variation in Seed Characteristics of Eastern White Pine (Pinus strobus L.)

Natural variation in seed characteristics of eastern white pine (Pinus strobus L.) trees and its relationship with the size, form, and crown class of parent trees was examined in second-growth, white pine mixedwood stands in Ontario. Cones were collected prior to and following partial harvesting of two stands during 2 years of above-average seed production. Fully enlarged seed extracted from mature cones was X-rayed to determine seed yield per cone, the percentage of sound, partially filled, and empty seed, and the sound seed mass for each tree. Variation in seed yield per cone, the proportion of sound, partially filled, and empty seed, and seed mass was much greater among individuals than between stands or seed years. The strength and significance of the relationship of seed mass with sound seed yield differed with stand and seed year. In uncut stands, seed mass was higher for trees with dominant crown class, larger live crown ratios, and smaller height to diameter ratios, suggesting tree vigour and microsite quality influence seed mass. Proportion of partially filled seeds was significantly reduced in both stands in the second year likely due to increased growing degree days during female gametophyte development. The implications of these results to natural and artificial regeneration of white pine are discussed.     

Cone and seed production from stone pine (<Emphasis Type="Italic">Pinus pinea</Emphasis> L.) stands in Central Range (Spain)

Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be difficult to attain. The success of this regeneration is affected by factors such as the total amount of seed available, the short dispersal ability of the pinyon, the conditions required for germination, specific problems associated with the establishment, early survival of the seedlings due to severe summer heat and drought, competition for water and mineral resources and grazing damage. This study focuses on seed availability. The amount of available seeds depends on the number and size of the cones and the number of viable pinyons within the cones. In stone pine stands, both variables show great year to year variability. Both cone and seed production, for a given year, are also conditioned by the vigour and health of the tree, its size, the condition and attributes of the stand and the loss of seed through pests or predation. In this study, the main factors which influence cone and pinyon production are identified and a multivariate model to predict annual cone and viable seed production is developed. To consider the correlation among observations coming from the same tree, stand or year, random components are included in the model. The multivariate random structure allows for future calibration of the model for a given year from a small additional sample of observations. It is important to know the total amount of viable seed produced in a stand for a given year since regeneration cuttings for Stone pine should be concentrated in high crop years.     

Scots pine (Pinus sylvestris L.) plantations contribute to the regeneration of holly (Ilex aquifolium L.) in mediterranean central Spain

The aim of this study is to evaluate the recruitment possibilities of holly (Ilex aquifolium L.) populations under Pinus sylvestris plantations in the mountains of Central Spain. Population recruitment of holly under P. sylvestris L. plantations was studied at two localities. We sampled holly seed rain, seed bank, and seedling emergence and survival (of both emerged and planted seedlings) in both localities. Seed germination was analysed by randomly sowing Ilex seeds and their subsequent recollection and analysis over the following 3 years (only in one locality). Seed rain, seed bank and emerged seedling densities did not differ between localities. Seed bank density was between 10 and 20 seeds m⁻², considerably higher than the observed seed rain (0.4–1.2 seeds m⁻²), and also higher than the emerged seedling density (0–4 seedlings m⁻²). But Ilex is not very efficient in germinating under pine forests (29.1% germination after 3 years). This may indicate a seed accumulation process of at least 5 years. Seedling survival for the first year differed among the studied sites (50–60 vs. 17%). Nevertheless these survival rates are higher than those found for the same seedling populations in different forest habitats (not Scots pine forests) from near locations. Differences in summer water stress between the study sites are proposed as the main cause of the observed differences in seedling survival. It is concluded that P. sylvestris forests may provide one of the best regeneration habitats for holly in the Mediterranean area, where this species is close to the Southern limit of its distribution.     

Morphological indicators of stock quality and field performance of red oak (Quercus rubra L.) seedlings underplanted in a central Ontario shelterwood

The value of initial stem diameter near the root collar, shoot length and number of first-order lateral roots (FOLR) as morphological indicators of stock quality and field performance was examined for bareroot (1+0, undercut) red oak (Quercus rubra L.) underplanted in a shelterwood in central Ontario. These three attributes were measured on more than 400 seedlings prior to planting, and their relationship with height and basal diameter growth two years after planting was determined using correlation and regression analysis. Initial diameter, shoot length and number of FOLR were positively and significantly correlated with second-year height and diameter. These relationships were strongest for diameter, but this variable explained less than 25% of the total variation in growth. Of the three indicators, diameter was also the best predictor of several physical characteristics of root systems two years after planting. Initial diameter was significantly correlated with root volume, root area and lateral root, taproot and total root dry mass. Weaker relationships existed between initial shoot length and number of FOLR and second-year root system features. Stem diameter two years after planting was more strongly related to root volume, area and dry mass than was initial diameter, the probable result of adjustment in root-shoot balance of planting stock to the shelterwood environment.     

Histopathology of primary needles and mortality associated with white pine blister rust in resistant and susceptible Pinus strobus

White pine blister rust caused by Cronartium ribicola is a damaging non‐native disease of five‐needled pines in North America. Efforts to control the disease and mitigate damage to date have been only somewhat effective. Recent efforts to improve the health of eastern white pine and reestablish the tree as a dominant species in the North Central United States have focused on identification and propagation of disease‐free eastern white pine (Pinus strobus) growing in areas with a high incidence of blister rust. Many of these selections have been shown to resist infection following artificial inoculation with C. ribicola. In this study, 13 eastern white pine families derived from controlled pollination of selections previously determined to possess putative resistance as well as susceptible selections were inoculated with C. ribicola. Mortality data from inoculation studies show superior survivability in three families with over 60% of seedlings able to survive the 52 week post‐inoculation monitoring period compared to 0–10% survival of the most susceptible families. Primary needles were collected for histological analysis from all inoculated families 4 weeks after inoculation and from selected families 6.5 weeks and 38 weeks after inoculation. Histological observations of infection sites show distinct resistance reactions in the families more likely to survive infection based on mortality data. Analysis of the reactions in susceptible families revealed extensive hyphal colonization of the vascular bundle and adjacent mesophyll cells that appear uninhibited by tree responses. In resistant families, collapsed cells adjacent to infection sites, heavy deposition of phenolic compounds and abnormal cell growth were documented more frequently and appear to play an integral role in the ability of these eastern white pine families to impede growth of C. ribicola in primary needle tissue.     

Microstructural investigation of UV-laser irradiated pine (Pinus silvestris L.)

Summary Different surfaces of pre-sanded pine (Pinus silvestris L.), namely radial surfaces, tangential surfaces and cross sections, have been subjected to microstructure examination. UV-laser irradiation with a wavelength of 248 nm and an energy of 350 mJ is used to enhance the microstructure exposure. It has been shown that UV-laser irradiation is a useful and practical method for revealing microstructural details. This is more pronounced on the cross section. Sanding with emery paper finer than 800 mesh can reveal microstructure on the radial surface equivalent to that revealed by UV-laser irradiation. On the radial and tangential surfaces, more earlywood is extracted after UV-laser irradiation, resulting in an uneven surface. Some features such as loose fibres and a rack-gearing-like structure on the radial and tangential surfaces, as well as a loss of radially oriented cell walls on the cross section are observed as a result of the UV-laser treatment. The rack-gearing structure is composed mainly of a sawtooth-like pattern. The length of the sawtooth is in most cases approximately 9 and 19 m.This work was carried out in the Department of Wood Technology and Processing, Royal Institute of Technology (KTH). Financial support from KTH is gratefully acknowledged.     

Evaluation of seed production in a first-generation seed orchard of Chinese pine(Pinus tabuliformis)

We evaluated seed production in a first-generation orchard of Chinese pine(Pinus tabuliformis) during the crucial transition period from first generation to advanced generations.Clones varied significantly in all traits related to seed production.Repeatability of these traits ranged from 0 to 0.96.Seed production per ramet(SPPR),seed producing index(SPI),the number of relative female strobili(RFS),the number of scales,and the number of ineffective scales had comparatively high repeatability at 0.86,0.87,0.89,0.96,and 0.91,respectively.Correlation analysis showed that SPPR was greatly influenced by RFS and by the number of full seeds per cone.Finally,we showed that SPI was the best predictor of the seed-producing ability of clones.Our findings will assist seed orchard managers in effectively predicting and improving seed production of Chinese pine seed orchards.     

Mevalonate kinase activity during different stages of plant regeneration from nodular callus cultures in white pine (Pinus strobus)

Mevalonate kinase (MK) catalyzes a step in the isoprenoid biosynthetic pathway, which leads to a huge number of compounds that play important roles in plant growth and development. Here, we report on changes in MK activity in white pine (Pinus strobus L.) during plant regeneration by adventitious shoot organogenesis from cotyledons of mature embryos, including nodular callus induction, shoot formation and rooting. Nodular calli were induced from Pinus strobus (PS) embryos by culture in nodular callus induction medium in a 0-, 8- or 16-h photoperiod. Mevalonate kinase activity peaked in nodular calli after three weeks of culture on nodular callus induction medium in a 16-h photoperiod, whereas frequency of nodular callus formation peaked after 4 weeks of culture on nodular callus induction medium in darkness. During adventitious shoot formation, MK activity peaked in shoots derived from dark-grown nodular calli after 3 weeks on bud formation medium, and frequency of shoot formation was highest in dark-grown nodular calli cultured on bud formation medium for 4 weeks. During rooting, MK activity peaked 2 weeks after transfer of adventitious shoots to rooting medium and rooting frequency was highest in adventitious shoots after 3 weeks on rooting medium. Although during nodular callus induction in darkness MK activity was inversely related to frequency of nodular callus formation, MK activity was highly correlated with frequency of shoot formation and with rooting frequency. The observed increase in MK activity preceding rooting suggests that MK could serve as a marker for rooting of white pine shoots in vitro.