Oak Height Research Articles

Growth and quality of 16-year-old sessile oak (Quercus petraea (Matt.) Liebl.) planted in traditional and alternative row planting patterns

Abstract Traditional oak silviculture is costly due to high initial planting density required to obtain management goals of producing high quality timber. New methods therefore reduce the initial planting density and use a planting pattern that allows the inclusion of naturally regenerated trees of other species. The study presents the results of a 13-year experiment on the growth and quality of sessile oak planted in traditional and three alternative planting patterns. We hypothesized that increasing of initial spacing and use of natural regeneration to compensate for lower intra-specific competition does not deteriorate growth and quality parameters of oak. Breast height diameter, height, slenderness, height of the first live branch, diameter of the thickest branch, stem shape and potential future crop oak trees (PFCT) were measured and analysed. The local competition of admixture species was estimated on the basis of the relationship between the height of the oak and the height of admixture trees in its close proximity. The type of planting pattern had no significant effect on oak diameter, but oak height was greater in the traditional pattern than in alternative patterns. Height of the first live branch was the only qualitative trait that differed significantly between the compared planting patterns. The probability of an oak being selected as a PFCT was similar in traditional and alternative patterns, but PFCT absolute number was increasing with an increase of oak planting density. Analysis of competition of admixture species in alternative methods shows that it can reduce height, diameter and stability of oaks. On the other hand, the probability of trees being selected as a PFCT increases significantly with increasing interspecific competition. We conclude that, with controlled competition and at least moderate natural regeneration, the alternative planting patterns can produce oaks with similar growth and quality to those in the traditional pattern.

Soil change and broadleaf tree growth 10 years after wood ash and brash co-application to a clearfelled lowland conifer site in Britain

Abstract Wood ash use, to raise pH and replace nutrients lost through forest harvesting, is well regulated in Scandinavia and Canada, but not yet in the UK. This experiment applied granulated wood ash from mixed tree thinnings to a lowland clay mineral soil at ~2.3 t ha−1 dose rate, after clearfell of western hemlock (Tsuga heterophylla (Raf.) Sarg.). With brash (~56 t ha−1 dry weight) as N resource, a 4 × 4 matrix of ash only, ash + brash, brash only and control treatments were planted with oak seedlings (Quercus robur L.). Soil survey was undertaken before ash application and followed over 10 years. By year 2, self-sown grass was dominant in the control and ash plots, and birch (Betula pendula, Roth.) was present across all treatments by year 4. In year 10, oak height was 25–29 per cent greater in brash and ash + brash plots, with DBH increased >20 per cent over the controls. Birch DBH was greater by 30 per cent in brash plots but was over 50 per cent in the ash + brash plots. Foliar concentrations of Ca, K and P significantly increased with ash addition in both oak and birch, as Al, Mn, Fe and Cr decreased. Soil pH (CaCl2) was reduced in all treatments in year 2 likely due to nitrification, during organic matter and needle breakdown, but recovered 8 years later to be significantly highest in ash and ash + brash plots. Mg, K, Ca, Na, Ba and S concentrations were higher in ash plot soils, but soil organic matter, total carbon and total nitrogen declined due to mineralization and uptake by grass and trees. Wood ash addition did not significantly increase heavy metal concentrations in either soil or foliage. In the long term, wood ash aided soil recovery and promoted tree growth in combination with the brash – it could be beneficial for tree growth after thinning/coppicing on heavy mineral soils, with the prerequisite of an existing ground cover. Aim To quantify the effects of wood ash and brash addition over time to soils and tree growth after conifer clearfelling on a lowland clay soil site.

Invasive microstegium vimineum (Japanese stiltgrass) hinders growth and biomass of hardwood seedlings regardless of light and moisture regime

Limited natural oak (Quercus spp.) regeneration in current-day, closed-canopy upland oak forests across the eastern and central United States has prompted increased use of various silvicultural practices, including prescribed fire and/or thinning, to reduce competition from shade-tolerant, often fire-sensitive species, and ultimately, restore and/or maintain oak landscapes. However, these practices create disturbances that can promote the spread of invasive plants and complicate oak restoration attempts, especially if invasion differentially impacts oaks compared to competitor species during early seedling development. To evaluate if Japanese stiltgrass (Microstegium vimineum (Trin.) A. Camus), an invasive C4 grass common in the understory of these systems, impacts growth and biomass of hardwood seedlings in different light and moisture environments, we established a shadehouse experiment in May 2020 with one-year old seedlings of white oak (Quercus alba L.) and two competitor species, red maple (Acer rubrum L.) and sweetgum (Liquidambar styraciflua L.), in the following treatments: M. vimineum (MV) presence (with/without), light (40/10 % full irradiance), soil moisture (high/low), and their interactions. Monthly, from May to October 2020, we measured seedling height growth, stem basal diameter, and MV cover and height if present. In October 2020, we harvested a subset of seedlings and measured their above- and belowground biomass and aboveground MV biomass when present. At study cessation, regardless of light or moisture treatment, red maple and sweetgum were significantly shorter when grown with MV (17.9 and 15.6 cm, respectively) than without MV (33.5 and 22.3 cm, respectively) and had smaller basal diameters (with MV: 1.03 and 0.94, respectively; without MV: 1.34 and 1.25 cm, respectively) and ∼ two times less biomass. White oak basal diameter was 1.2 times lower with MV (0.77 cm) compared to without MV (0.93 cm), but MV had no impact on white oak height growth or biomass, likely because of its conservative growth strategy and high-water use efficiency. Light and moisture treatments had little impact on MV height and cover, but MV biomass was greater with high (462 dry wt m−2) compared to low (398 g dry wt m−2) moisture treatment and ∼ 1.3 times greater when grown without vs with tree competition. Thus, MV invasion into closed-canopy upland oak forests may have species-specific effects on early seedling growth, reducing growth of competitor seedlings with non-conservative growth strategies more than that of upland oaks, but long-term studies are needed to better understand the potential legacy effects of MV on growing conditions and tree regeneration.

Chances and Limitations of Mixed Oak Regeneration under Continuous Canopy Cover—Evidence from Long-Term Observations

Traditionally, due to its light ecology, oak is regenerated on clear cuts or areas where the crown coverage is heavily reduced. Thus, the regeneration phase is relatively short. Recently, selective long-term regeneration phases avoiding large gaps in the canopy but fostering mixed-species stands have been advocated as being more in keeping with close-to-nature forestry in Central European forests. However, examples of the successful regeneration of oak in mixtures following this type of regeneration are largely missing. Here, we report the results of long-term experiments located in three different forest types, where oak was long-term regenerated under different mixing and canopy cover situations. The observation periods reached from 26 to 36 years. We focused on the dynamics of stem number reduction, as well as the height and biomass development of oaks and their interaction with interspecific competition and canopy density. The probability of oaks occurring in the regeneration basically decreased over the duration of the regeneration period. Despite this, considerable regeneration biomass growth could be observed, especially in the case of the lower standing volume of the mature stand. The development of beech as the main competitor is scarcely slowed down by the canopy cover compared to oak. Increasing canopy cover noticeably impeded oak regeneration in the considered mixed stands. The model results suggest that a reduction in competition within the regeneration by lowering the proportion of beech below 30% enhanced the success of oak regeneration in the long run even in small patches. The productivity of the remaining stand was primarily driven by standing volume. However, a negative trend of its productivity emerged with high regeneration biomasses. The study results show that small-scale oak regeneration with prolonged regeneration duration is possible in principle. However, oak regeneration requires active and continuous silvicultural assistance, which has to be adjusted to the specific site conditions.

Conversion of low-value stands by corridor method in Left-Bank Forest-Steppe, Ukraine

Abstract The aim of the study was to identify the influence of different widths and cardinal directions of felled corridors on the condition and mensuration characteristics of the English oak trees planted there during the conversion of low-value young stands using the corridor method. The study was carried out in oak forests in the forest-steppe zone at a permanent sample plot. The experiment included the conversion of a low-value 8-year-old stand to improve its species composition. The sample plots were laid out in a fertile hardwood forest site. The conversion was realised by felling corridors of various widths (6, 9 and 12 m) and directions and planting English oak trees (Quercus robur L.) within them in rows. For the planted oaks, tending felling was carried out three times: weeding (8 years), cleaning (13 years) and thinning (32 years). A comparative analysis of mensuration characteristics (average height, diameter, growing stock, radial increment, health condition, etc.) was carried out for 32-year-old oak trees grown in the corridors and a part of a low-value stand in the unfelled strips after the tending felling. It was found that the average height and diameter at breast height of oaks in the 6, 9 and 12 m wide corridors of different cardinal directions did not differ significantly. The difference in oak stocks within 6 and 9 m wide corridors of different cardinal directions was also insignificant. The stock differences were statistically significant for 6 and 12 m wide corridors as well as for 9 and 12 m wide ones. The article made recommendations on the width of felled corridors and unfelled strips to effectively convert low-value young stands by the corridor method.

Long-term effects of organic matter removal, compaction, and vegetation control on tree survival and growth in coarse-textured, low-productivity soils

The Long-Term Soil Productivity Network is providing a systematic examination of the effects of organic matter removal and compaction on a variety of different soils and forest types across North America. Here we report on the 22nd-year survival and height growth of white oak (Quercus alba), northern red oak (Q. rubra), and shortleaf pine (Pinus echinata) on rocky, nutrient-poor soils that have a low to moderate water holding capacity in the Missouri Ozark Highlands. Treatments included three levels of organic matter removal (sawlog, whole tree, and whole-tree plus forest floor) and three levels of soil compaction (none: bulk density = 1.34 g cm−3; moderate: bulk density = 1.65 g cm−3; and severe: bulk density = 1.78 g cm−3) each with and without vegetation control. Following treatments, bareroot, 1–0 white oak, northern red oak, and shortleaf pine seedlings were planted at a 3:3:1 ratio, approximating the distribution of these species in this region. Within half of each plot, a vegetation control treatment was applied for the first 10 years by treating competing vegetation with herbicide. After 22 years, vegetation control significantly increased biomass and height of all planted species. The average height for northern red oak with vegetation control treatments was 884 cm with vs. 606 cm without; white oak was 837 cm with vs. 424 cm without; shortleaf pine was 1339 cm with vs. 1220 cm without. Moderate compaction increased average white oak height by 15% and severe compaction increased average height by 18% compared to no-compaction treatments. Compaction was not a significant treatment for red oaks or for shortleaf pines. However, the coarse fragments in the study soils appear to have muted much of the compaction to the soil’s fine-earth fraction and may have had the unintended effect of providing partial vegetation control. Whole-tree removal reduced average shortleaf pine heights by 6% vs. sawlog-only removal, while whole-tree + forest floor removal increased heights 3% compared to sawlog harvests. Organic matter removal was not a significant treatment for either oak species. Red oak survival probability was 0.79 with vegetation control vs. 0.34 without; white oak was 0.81 with vs. 0.65 without; shortleaf pine was 0.49 with vs. 0.45 without. Overall, vegetation control was the dominant factor driving survival and growth of oaks, and to a lesser degree, growth of shortleaf pine. Organic matter removal and compaction treatments had relatively little negative effect on height, indicating the resilience of these species to harvest-related disturbances in Ozark Highlands soils.

Factors affecting admixed pedunculate oak growth under heavy browsing by deer: benefits from inter- and intraspecific neighbourhoods

One of the most important ecosystem processes, especially in temperate and boreal forests, is herbivore browsing. In this study, we tested five hypotheses: (H1) oak tree density would positively affect their height; (H2) despite severe browsing pressure, the height of oaks would increase with the age after planting; (H3) oaks growing among the planted pines would be taller than those among the sown ones; (H4) the growth of single oak saplings or of oak nests would be positively affected by the height of the pines growing in the immediate neighbourhood of the oaks; and (H5) the oak height would be affected by the location within a nest and oaks growing in the central zone would be taller than the others. The study was conducted in the Piska Forest in the north-eastern part of Poland. We established three variants of experiment. In the first variant, oaks were planted individually. In the second and third variants, oaks were planted in small nests. The second and third variants differed in the spacing of the nests: 8 × 8 m and 6 × 6 m, respectively. The division into the sub-variants referred to type of pine regeneration. In the first sub-variant, Scots pine was planted. In the second, pine was sown. In general, oaks growing within nests were significantly taller than those planted individually in the Scots pine rows. Despite heavy browsing, oak height consistently increased during the course of the study. Oak height also depended on the type of pine regeneration, and the mean height of oaks surrounded by planted pines was significantly higher than that of oaks surrounded by sown pines (which, in average, was shorter). That was because the planted pines were taller than the sown ones. We found that Spearman’s correlation coefficients were positive and significant between pine and oak heights in variants 2 and 3. Growth of oaks did not depend on their location within a nest. The results of the regeneration method of oak (single vs nest and few vs many nests) are modified by browsing. The best method found in the heavy browsing circumstances was planting oaks in many nests within successful pine regeneration (providing the oaks with protection against the browsing). The pine will provide the most efficient protection if regenerated a few years before the oaks.

Early Tree Growth in Reclaimed Mine Soils in Appalachia USA

Surface mining disturbs hundreds of hectares of land every year in many areas of the world, thereby altering valuable, ecologically-diverse forests. Reforestation of these areas after mining helps to restore ecosystem functions and land value. In Appalachia, native topsoil is normally replaced on the surface during reclamation, but waivers allow for brown and gray sandstone materials to be used as topsoil substitutes. Numerous studies report the growth of trees in these substitute mine soil materials, but few studies have compared the height of trees grown in reclaimed mine soils to the heights of trees grown in native soils. This study determined the growth of red oak (Q. rubra L.), white oak (Quercus alba L.), and tulip poplar (Liriodendron tulipifera L.) in two mine soil types which were compared to projected growth in native soils. Heights of tree seedlings in native soils at 11 years were estimated from site indices (SI) from USDA Soil Survey data. At the mine sites, areas with brown and gray mine soils (one site with a mulch treatment) had 12 tree species planted and growth was measured annually for 11 years. Mine soil pH after 11 years was 5.3 for brown mine soils, 6.6 for gray mine soils, 7.0 for mulched mine soils, and 4.1 to 5.2 for native forest soils. After 11 years, tree heights in gray mine soils were significantly lower (0.5 m) than tree heights in brown mine soils (2.8 to 4 m) for all three species. Trees in mulched mine soils were up to 0.7 m taller than trees in un-mulched brown mine soils. After 11 years, red oak height was 6.3 m in native soils and 3 m in brown and mulched mine soils (52% lower); white oak was 7.3 m tall in native soils compared to 3.6 m in brown mine soils (50% lower); and tulip poplar was 11.5 m tall in native soils and 3.5 to 4 m tall in brown and mulched mine soils (70% lower). In gray mine soils, trees were not growing at all. While the trees in brown mine soils are growing, tree growth has not reached projected levels of tree growth in native soils during the first 11 years after planting. The purpose of forestry reclamation is to restore ecosystem diversity and function. This study showed that one measure of ecosystem function, tree growth, was 50% lower on reclaimed mine soils than native forest soils. Maturing mine soils may develop properties over time that are similar to native soils and, with the increased rooting depth, may provide conditions where increased tree growth rates and height may be attained during the next several decades.

Pedunculate and Sessile Mixed Oak Forest Regeneration Process in Lithuania

Pedunculate and sessile oak species are sympatric. These oaks hybridize with one another, and this process influences the development of undergrowth. The purpose of this study was to determine how different oak species influence the forest regeneration process. For this purpose, the forest was divided into eight transects of 300 m and 100 m widths, distinguished into temporary plots of 10 m in diameter covering the whole territory of the forest. The distribution of oak undergrowth was calculated by four oak height groups, determining the composition of the first storey, covering of underbrush and herbaceous plant, and forest site. We determined that the spread of oak differed depending on the first storey tree species and underbrush. Grass cover was the biggest influence on the sessile oak. The impurity of sessile oak in oak stands had a positive impact on the development of undergrowth, since the entire undergrowth develops faster than separate components of the undergrowth.

Effects of interspecific competition from surrounding vegetation on mortality, growth and stem development in young oaks (Quercus robur)

Facilitation by a neighboring woody understory has been suggested as a cost-effective and sustainable way to regenerate oaks. However, concerns about reduced plant growth and quality due to competing neighboring vegetation have hindered implementation. Here we studied competitive effects from herbaceous and woody vegetation on survival, growth, canopy development and stem quality in pedunculate oak (Quercus robur) in an open-field experiment in southern Sweden. Oaks were grown for eight years in four different competition treatments: no competing vegetation, with herbaceous vegetation (mainly grasses), with woody vegetation, and with both herbaceous and woody vegetation. During the first four years, competition had little effect on oak survival. However, after eight growing seasons, survival rates decreased to about 20% for oaks surrounded by woody vegetation, in contrast to oaks grown with only herbaceous vegetation that had a survival rate of near 100%. Competition from herbaceous and woody vegetation both reduced oak stem diameter and height growth, but they affected height growth differently. During the first growing seasons, oaks in the treatment with woody vegetation were able to keep up with the height growth of the surrounding vegetation. Thereafter, height growth stagnated, and after eight growing seasons heights of oaks in the treatment with woody competitors were only 30–39% that of oaks in the treatment without competing vegetation. In contrast, competition from herbaceous vegetation only restricted oak height development marginally. Interspecific competition not only restricted growth and survival but also shifted shoot architecture, resulting in a greater frequency of oaks with straight monopodial stems. Although competition from both herbaceous- and woody vegetation positively affected stem straightness, plots with woody vegetation had a greater proportion (0.42) of oaks with a single straight monopodial stem. Our results demonstrate that the facilitative competitive effects from herbaceous and woody vegetation could be used to control allocation patterns in young oaks, promoting development of tall straight monopodial stems. Considering the observed trade-off between high stem quality and survival, we recommend long-term assessment of this trade-off prior to application in practical forestry.

Oak restoration in water-limited pine plantations: interactive effects of overstory light interception and water availability on understory oak performance

Oak regeneration within pine monocultures is an opportunity to diversify forest structure. We examined the relationships between overstory (Pinus brutia) light interception and understory oak (Quercus ithaburensis) performance in water-limited forests. The study was performed in a mature pine plantation in Mediterranean Israel. Twenty-year-old oaks differing in location with respect to pine overstory and representing a gradient of light availability, such as open space (irradiance 100 %), interface (17–77 %), and understory (14–23 %), were monitored. Photosynthetic photon flux density (PPFD), leaf gas exchange, and twig water potential (TWP) were measured during the growth season under increasing drought stress. Predawn TWP decreased sharply from early to late spring and was positively related to irradiance during mid-spring only. Predawn to midday TWP gradient was positively related to irradiance mostly so during mid-spring. Daily averages of stomatal conductance (gs), net carbon assimilation rate (A), and transpiration rate (E) were highest in early spring and decreased gradually toward late spring. They were positively related to irradiance though this relationship became less pronounced from early to late spring. Oak height and stem basal area were positively related to irradiance. A/gs ratio was positively related to irradiance throughout the entire growth season. It increased from early to mid-spring but decreased toward late spring. A/PPFD ratio decreased from early to late spring showing a negative relationship with irradiance. We concluded that light availability was mainly responsible for spatial variation in oak performance and proposed that small-scale overstory gaps aiming for direct sunlight exposure during early spring should achieve maximum understory oak performance with minimal pine removal.

Restoration release of overtopped Oregon white oak increases 10-year growth and acorn production

In the Willamette Valley–Puget Trough–Georgia Basin ecoregion of the North American Pacific Northwest, there has been widespread encroachment of Douglas-fir (Pseudotsuga menziesii) upon Oregon white oak (Quercus garryana) savanna and woodland stands that were historically maintained by frequent anthropogenic fire. Restoration of these stands requires removal of the Douglas-fir overstory, although there is little information on how oak trees that have been suppressed for decades respond to release. Our objective was to evaluate the 10-year response of oak trees to three release treatments from overtopping Douglas-fir in a study replicated at four western Washington sites. Treatments were: full release (removal of all Douglas-fir within a radius equal to the oak’s height), half release (removal of Douglas-fir within a half-height radius), and thin only (stand-level commercial thinning of the Douglas-fir overstory; oaks not targeted for release). Periodic diameter growth of oak trees in the full-release treatment was significantly greater (by as much as 243%) than that in the other treatments and increased with time since treatment. Oak height and crown area growth rates were not influenced by treatment, but larger pre-treatment crown size was associated with greater post-treatment diameter growth and acorn production. Full release increased acorn production compared to thin only in years when region-wide production was moderate to high (5 of 9years); half release increased production relative to thin only in 2 of 9years, but to a lesser degree. Height growth of residual Douglas-fir trees was greater than that of oak trees in all treatments. The increasing post-treatment growth rate of the fully released oak trees and their increased acorn production indicate the capacity of long-suppressed Oregon white oak to rapidly recover following complete removal of a conifer overstory. The oak trees showed no negative effects following the dramatic change in environment associated with this treatment. Thus, a single-entry, complete release from overtopping conifers was effective in restoring overstory structure and composition, which is an initial step in restoration of invaded oak woodland or savanna.

Temperate Silvopasture Tree Establishment and Growth as Influenced by Forage Species and Cultural Management Practices

Tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) is known to inhibit tree growth. Competition for moisture and nutrients, and possibly allelopathy are suspected. This study examined if tall fescue inhibits tree growth more than two other cool-season forages, if tree growth differences are attributed to forage yield or tall fescue’s endophyte, and if irrigation and fertilizer can alleviate forage inhibition of tree growth. Four silvopasture tree species were planted into sods of three cool season forage species and grown four years with and without irrigation and fertilizer. Differences in tree growth did not correspond with forage dry matter yield or tall fescue endophyte status. Black walnut and red oak height and diameter growth and pitch x loblolly pine diameter growth were greater in Kentucky bluegrass and orchardgrass compared to the forage tall fescues [Ky-31 (E+), Ky-31 (E-), and Max-Q]. Irrigation and/or fertilizer did not alleviate forage competition on two tree species.

Thinning effect on light regime and growth of underplanted red oak and black cherry in post-agricultural forests of south-eastern Canada

Over the last century, north-eastern North America has seen the gradual abandonment of much agricultural land that had become unsuitable for modern practices. This shift in land-use has released large areas that are now dominated by early-successional forests with limited mid- and late-successional species regeneration. Enrichment underplanting, with the partial preservation of the existing vegetation to serve as a shelterwood, has been proposed to restore the production of valuable timber. The present study reports mid-term (8–12 year) results from an enrichment planting experiment located at two sites in the St-Lawrence River Valley, eastern Canada. The objective was to identify the required frequency of low-intensity thinnings necessary to secure an optimal density of promising stems of black cherry (Prunus serotina Ehrh.) and red oak (Quercus rubra L.). Partial thinning treatments were applied during the 3rd and 7th growing seasons and compared to a single thinning applied at the 7th year. Each thinning treatment increased available light to 20–30 % in the understory (measured the following year at 2 m from ground level). The height of red oaks released twice was almost double that of red oaks thinned only once. The effect on black cherry was less dramatic and significant only at one of the two sites. A higher intensity or an earlier application of thinning regimes may be required for black cherry. The early thinning allowed a larger number of planted trees to react positively to the second thinning. The practice of double thinning over a period of 12 years allowed for the production of a significant number of competitively successful trees for the landowner.

Spatio-temporal analysis of tree height in a young cork oak plantation

Cork oak is one of the most valuable natural forest genera in the Mediterranean basin. Modelling cork oak growth has been a challenge for foresters in recent years because of strong site and genetic influences, below-ground competition, management regimes and age effects. Because cork productivity is related to forest height, which is, in turn, related directly with site characteristics, an increase in the accuracy of height prediction implies improved productivity estimation. A Bayesian maximum entropy (BME) geostatistical model was applied to characterize the space–time pattern of height of young cork oak in a forest stand from central Sardinia in the years 2000, 2002, 2003, 2006 and 2008. Cork oak height maps were produced for each of the 5 years. The main goals were to analyse and interpret through time (i) the changes in spatial correlation and (ii) the changes in spatial distribution of cork oak height. The plantation was characterized by an increasing spatial dependence through time, whereas the temporal range was 2 years. Cork oak height was significantly correlated with wind speed (reduced by a neighbouring forest) in all the years implying a single trend. The correlations were larger for 2006 and 2008 than for previous years. Three other environmental variables (shade, elevation and slope) were less significant and their influence restricted to 2 years only. This research has several implications for the management of cork oak in the young phase.

Effect of Fabric and Plastic Containers on Plant Growth and Root Zone Temperatures of Four Tree Species

Abstract Live oak (Quercus virginiana Mill.), red maple (Acer rubrum L.), and sweet gum (Liquidambar styraciflua L.) trees were planted in #7 fabric or plastic containers on April 18, 2004, and grown for two growing seasons. Live oak and golden rain tree (Koelreuteria paniculata Laxm.) trees were planted in #10 fabric or plastic containers on May 6, 2005, and harvested the following summer. Plant height, canopy width, and caliper were measured periodically, and root zone temperatures were recorded at 30-min intervals throughout each study. In the 2004 planting, live oak height and canopy width increased more for plants in plastic containers than for those in fabric containers from May to July 2004. In contrast, no difference in live oak height or canopy width growth occurred between container types from July to September 2004, but trunk caliper increased more in plastic than in fabric containers during this time interval. No differences between container treatments were noted for any measured parameter for red maple or sweet gum trees planted in 2004 or for golden rain tree or live oak trees planted in 2005 at any measurement interval during the study. Average monthly high and low substrate temperatures were similar between the two container types throughout the study. Fabric containers appear to be a reasonable alternative to plastic containers for above ground nursery crop production, although small differences in growth occur for some species.

Konkurrenz zwischen Stieleiche und Buche auf Lothar-Sturmflächen | Competition between pedunculate oak and European beech on Lothar windthrow areas

The competitive pressure of naturally regenerated European beech (Fagus sylvatica) saplings on planted pedunculate oak (Quercus robur) was investigated on two 1.8 ha permanent plots near Habsburg and Murten (Switzerland). The plots were established with the aim to test methods of artificial oak regeneration after large-scale windthrow. On both plots, 80 oaks exposed to varying levels of competitive pressure from at most 10 neighbouring beech trees were selected. The height of each oak as well as stem and branch diameters were measured. The competitive pressure was assessed using Schütz's competition index, which is based on relative tree height, crown overlap and distance from competing neighbours. Oak trees growing without or with only slight competition from beech were equally tall, while oaks exposed to moderate to strong competition were smaller. A threshold value for the competition index was found above which oak height decreased strongly. The stem and branch diameters of the oaks started to decrease even if the competition from beech was slight, and decreased much further with more competition. The oak stems started to become more slender even with only slight competition from beech. On the moderately acid beech sites studied here, beech grow taller faster than oak. Thus where beech is competing with oak and the aim is to maintain the oak, competitive pressure on the oak must be reduced at an early stage. The degree of the intervention should, however, take the individual competitive interaction into account, with more intervention if the competition is strong.

The increasing scarcity of red oaks in Mississippi River floodplain forests: Influence of the residual overstory

Red oaks – cherrybark oak ( Quercus pagoda Raf.), willow oak ( Quercus phellos L.), water oak ( Quercus nigra L.), and Nuttall oak ( Quercus texana Buckley; aka: Quercus nuttallii Palmer) – are not regrowing in Mississippi Delta river floodplain forests in the southeastern United States in sufficient numbers to sustain the former species composition and timber and wildlife values. Even if vigorous red oak reproduction becomes established, partial harvesting that does not remove the taller trees will suppress understory red oak height growth more than it will suppress height growth of such other species as sugarberry ( Celtis laevigata Willd.), American elm ( Ulmus americana L.), cedar elm ( Ulmus crassifolia Nutt.), swamp dogwood ( Cornus foemina Mill.), green ash ( Fraxinus pennsylvanica Marshall), and sweetgum ( Liquidambar styraciflua L.). Consequently, the red oaks in these partially harvested stands become increasingly suppressed and probably die; and there is a shift in species composition to the other species. In addition to ensuring vigorous oak reproduction, silvicultural clearcutting or rapid removal of the residual trees following shelterwood or seed tree harvesting to provide full sunlight is needed to ensure red oaks become a dominant part of these future river floodplain stands.

A Random-Parameter Height-Dbh Model for Cherrybark Oak

Abstract A random-parameter model was used to relate total height to diameter at breast height (dbh) for cherrybark oak (Quercus pagoda Raf.). Data were obtained from 561 trees located in 50 stands occurring on bottomland hardwood sites in East Texas, near the western extent of the cherrybarkoak natural range. Mixed-model estimation techniques were used to fit fixed-effects parameters to the height-dbh relationship for cherrybark oak, with random-effects parameters representing sample stands from which tree data were obtained. The fixed-effect parameter estimates can be used topredict average cherrybark oak height for a given dbh in the region from which the data were obtained. Because random parameters associated with stands were used in the data-fitting process, the models can be calibrated to fit new stands by obtaining measurements to fit appropriate randomparameters for that stand. This calibration improves height predictions for individual stands while requiring less data than would the development of a completely new height prediction model for that stand. South. J. Appl. For. 29(1):22–26.

Vegetative Characteristics of Recently Reforested Bottomlands in the Lower Cache River Watershed, Illinois, U.S.A.

Abstract Interest in restoring native ecosystems is resulting in conversion of marginal agricultural lands to bottomland hardwood‐dominated forests in the midwestern and midsouthern United States. Growing stock for these efforts typically consists of planted oak (Quercus spp.) and volunteer vegetation. Reports of mixed reforestation success and the lack of post‐establishment tree growth data prompted this evaluation of vegetation characteristics of 5‐ to 7‐year‐old operational restorations in the Lower Cache River Watershed in southernmost Illinois, U.S.A. Fraxinus pennsylvanica (green ash), Acer negundo (box‐elder), and Liquidambar styraciflua (sweetgum) together comprised 77% of all tree stems observed. Full stocking of overstory tree species can be expected to produce a closed canopy stand within 160 m of a forested edge, due primarily to the abundance of rapidly growing volunteer‐origin trees. Planted oaks contributed minimally to total tree stocking but were present in sufficient numbers to eventually improve wildlife habitat, and therefore satisfied restoration objectives. Oak height was 23% greater when in the presence of a non‐oak tree species. Herbaceous cover was dominated by Solidago gigantea (late goldenrod) and Juncus spp. (rushes). Solidago gigantea was associated with poor growth and low density of non‐oak stems, whereas Juncus dudleyi (Dudley's rush) was associated with taller non‐oak stems. These results suggest that the presence of volunteer‐origin trees is crucial for the creation of full stand stocking that will result in rapid development of a closed canopy forest. Improved success of future reforestation efforts will require more intensive methods to establish adequate stocking beyond 160 m of a forest edge. Methods described here could be adapted for agricultural field to forest restorations in other regions to predict critical distances from volunteer seed sources within which supplemental planting would be unnecessary to meet tree stocking objectives.