Plants, fungi, and invertebrates of Northern red oak (Quercus rubra L.) experimental stands in Rogów Arboretum (Poland)

Oak (Quercus spp.) research and management often focus on northern red oak (Quercus rubra) and assume that associated upland oaks have similar growth patterns. To test this premise, we measured the survival and development of four species of acorn-origin oak seedlings growing in four different levels of understory sunlight for 8 years. Northern red oak had better survival than black (Quercus velutina), chestnut (Quercus montana), and white oak (Quercus alba) in 5% sunlight, but none of the species exhibited much growth. In 15 and 40% sunlight, survival was equal among species, but for growth the seedlings formed two groups with chestnut/northern red oak growing more than black/white oak. In 75% sunlight, survival was equal among species, but northern red oak grew faster than the other three species. Assuming that other oaks have growth habits similar to those of northern red oak could lead to a reduction in or the inadvertent loss of an oak species. Management and Policy Implications This study points out key differences in the survival and growth of black, chestnut, northern red, and white oak seedlings at the light levels created by a three-cut shelterwood sequence. Important management recommendations based on those differences include the following: In advance of an acorn crop, decrease dense shade to diffuse or partial shade (15–40% sunlight) by removing the midstory and understory canopies. If premasting shade control is not possible, begin regeneration treatments no later than 1–2 years after black, chestnut, and white oaks mast or no later than 3–5 years after northern red oak produces acorns. Conduct species-specific inventories for oak seedlings rather than grouping them together as oak reproduction. To emphasize chestnut or northern red oak, use the two-cut or three-cut shelterwood sequence because seedlings of these two oak species can grow reasonably well in 15–40% sunlight. To emphasize black or white oak, use a two-cut shelterwood because seedlings of these species need approximately 40% sunlight or more to initiate and sustain vigorous height growth.

SummaryForests in the Ozark Mountains of northern Arkansas recently experienced a widespread oak decline event. Armillaria, a root rot fungus, has been associated with other oak decline events and may have been an important contributing factor to tree mortality in this event. Although Armillaria has been identified from the Ozark Mountains in Missouri, it has never been investigated in the Arkansas Ozarks. Molecular diagnostic techniques were used in this study to identify species of Armillaria present on roots removed from dead trees of two common oak species, northern red oak, Quercus rubra L., and white oak, Q. alba L., from three geographic areas and on three topographic positions – ridges, south‐ and west‐facing benches. Armillaria(A. mellea, A. gallica or A. tabescens) was identified from 31% of root samples taken from 102 trees in seven of nine sample plots. Armillaria mellea, occurred most often (20 samples, both oak species on seven plots) followed by A. gallica (10 samples, northern red oak only on four plots), and A. tabescens occurred twice (on northern red oak in a single plot). Thus, all three Armillaria species occurred on northern red oaks while A. mellea was the only species recovered from white oaks. Results varied by topographic position with samples from tree roots on ridges having the fewest positive identifications, one of 29. West‐facing benches had the highest positive samples with 20 of 41 testing positive and trees on south‐facing benches were intermediate with 11 of 32 samples from infected trees. This study documents the occurrence of three species of Armillaria in the Arkansas Ozarks and their association with oak mortality resulting from an oak decline event coupled with a red oak borer, Enaphalodes rufulus, outbreak. Further, it documents some potential variation in host/pathogen combinations and forest site conditions.

Site and stand variables influencing red oak borer, Enaphalodes rufulus (Coleoptera: Cerambycidae), population densities and tree mortality

The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), is an introduced defoliator that preferentially feeds on oaks, Quercus spp. (Fagaceae) in the north‐eastern USA. As the gypsy moth expands its geographic range, the extensive oak component in forests and urban environments of the USA assure its successful establishment. Given their economic and ecological importance, and the gypsy moth's potential to cause mortality, we evaluated caterpillar preference and performance on various oaks prevalent in the central hardwoods region. Most of the physical and chemical characteristics we measured, from budbreak phenology to foliar chemistry, varied significantly among the oak species tested. Similarly, insect preference and performance varied significantly, though not always in predictable ways. Caterpillar preference was compared for black, Q. velutina Lamarck, burr, Q. macrocarpa Michaux, cherrybark, Q. pagoda Rafinesque, northern red, Q. rubra L., pin, Q. palustris Muenchhausen, swamp white, Q. bicolor Willdenow, white, Q. alba L., and willow, Q. phellos L., oaks. Gypsy moth preference was greatest for black and burr, and least for northern red, pin, and willow oaks. We assessed foliar characteristics and caterpillar performance on foliage from burr, cherrybark, northern red, pin, and willow oaks. Caterpillar preference did not always correlate with performance. Gypsy moth consumption and growth were highest, and development most rapid, on pin oak, which had high nitrogen and tannin levels, and was among the least preferred. Northern red and willow oaks were also among the least preferred and were the least suitable tested, producing caterpillars with moderate to low consumption and growth rates, as well as the longest development. Northern red oak contained the lowest foliar tannins; willow oak foliage was lowest in carbohydrates and nitrogen. Our results suggest that a combination of foliar characteristics may be responsible for gypsy moth preference and performance, and that an optimal combination of foliar components serves to maximize host suitability. These data will provide information useful for planning and managing urban forests in the presence of expanding gypsy moth populations.

Individual variation in acorn production by five species of southern Appalachian oaks

Ecological impact of phytoinvasions in Ukraine

The paper describes and provides examples of the application of the developed spatial dataset on the spread of invasive woody plant species in the forests of Transcarpathia, Ukraine. The dataset was developed based on forest inventory data using the open source QGIS program, which performed digitisation of forest plantation plans of permanent forest users and overlay analysis. The created dataset contains 4212 records of the distribution of the following invasive woody plant species: black locust (Robinia pseudoacacia L.), northern red oak (Quercus rubra L.), ash maple (Acer negundo L.), and brittle willow (Salix fragilis L.). The dataset contains information on the location of forest plots, silvicultural and taxonomic characteristics of stands with predominance and participation of invasive woody plant species. The created spatial dataset was used to study the distribution of invasive woody species of black locust and northern red oak in Transcarpathia by geobotanical and floristic zones. The results of the study showed that the most favourable conditions for the distribution of black locust are the area of beech-oak and oak-beech foothill forests of the Volcanic Range of the Ukrainian Carpathians within Transcarpathia, as well as the Transcarpathian Plain forest area. Unlike the artificially created northern red oak forests, the distribution of the black locust in the study area is primarily due to its biological properties, specifics of environmental relationships and of forestry in the past. Regarding the distribution of the northern red oak, the results of using our spatial dataset show that such forests have the largest portion in the areas of hornbeam-beech and beech forests (39.4%) and in the forests of the Volcanic Ridge (24.2%). The created spatial dataset can be used to study the distribution of invasive woody plant species within the forest cover of Transcarpathia. The spatial dataset can also be utilised as a source of training samples for machine learning, which is involved in the processing of satellite images to identify new habitats of invasive woody plant species.

Northern red oak ( Quercus rubra L.) seedling growth has been extensively studied. White oak ( Quercus alba L.) and chestnut oak ( Quercus prinus L.), however, are far less investigated despite their importance among upland oak species in eastern North American forests. We characterized white and chestnut oak seedling response to light and available soil nutrients while using northern red oak as a benchmark. Germinants were grown within one of three shade treatments (25%, 18%, and 6% of full sun) in one of two native forest soil mixes over two growing seasons. Leaf area, shoot mass, and root mass of all three species showed positive growth responses to increasing light. Growth and biomass were higher for all species grown in the more nutrient-rich forest soil, but chestnut oak displayed the greatest positive responses to the higher nutrient levels. White oak seedlings were the slowest growers and demonstrated the most root-centered growth, with root to shoot ratios almost twice that of either chestnut or northern red oak seedlings. The oak species evaluated here responded differently to changes in resource availability. Our study demonstrates the differential response of upland oaks to low light and nutrients. These differences need consideration when developing oak management prescriptions for specific oaks.

A Red Pine (Pinus resinosa Aiton) plantation and adjacent Northern Red Oak (Quercus rubra L.) – Large-toothed Aspen (Populus grandidentata Michx.) woods, both of which developed from a savannah scrub beginning approximately 60 years ago, were compared with regard to terrestrial snail diversity and abundance. The comparison involved a 30-minute search of ten 1-m2 quadrats at ten sites in each habitat. In the Northern Red Oak – Large-toothed Aspen woodland, 13 species and 661 individuals were recorded, whereas, in the Red Pine plantation, six species and 24 individuals were recorded. In the Northern Red Oak – Large-toothed Aspen woodland, the most characteristic and abundant species was Novisuccinea ovalis (Say, 1817), which was present in 74 of the 100 quadrats and was represented by 460 individuals. In the pine plantation, the most common species was Zonitoides arboreus (Say, 1816), which was present in 16 quadrats and was represented by 17 individuals. This species was the second most common in the Northern Red Oak – Large-toothed Aspen woodland where 70 individuals were found in 34 quadrats. In both habitats, Z. arboreus was associated with downed wood. Other species occurring in more than 15% of quadrats in the Northern Red Oak –Large-toothed Aspen woodland were Strobilops labyrinthicus (Say, 1817), Glyphyalinia indentata (Say, 1823), and Euche motrema fraternum (Say, 1824). Although a lower number and diversity of terrestrial snails in the conifer plantation was expected, the contrast was greater than anticipated. The estimated abundance of 46 000 N. ovalis per hectare suggests the potential importance of these medium-sized snails in the relatively dry Northern Red Oak – Large-toothed Aspen ecosystem.

Due to the relevance of protected areas to the conservation of native biota, the magnitude of invasions and threats posed by alien plants are currently important issues for the preservation of these areas. The paper summarises data on invasive alien plant species presence in the most valuable protected areas in Poland, i.e. national parks (NPs). We investigated the distribution of invasive alien plant species and management attempts concerning those species. We analysed data obtained from 23 national parks originating from published and unpublished sources. Invasive plants were present in all protected areas analysed, from two to 42 species in a particular national park, and 68 in total. The most widely distributed species were: Impatiens parviflora (present in 19 NPs), I. glandulifera (17), Solidago gigantea (17), Reynoutria japonica (17), and Robinia pseudoacacia (16). The conducted analyses showed that the number of invasive species decreased with the higher altitude (asl) of the national park. The most often managed species were Impatiens glandulifera (being removed in seven NPs), I. parviflora (six), Padus serotina (four) and Quercus rubra (four). In the majority of NPs, control activities are limited to small areas and singular species, thus having an incidental character. Only in five objects (Białowieża NP, Biebrza NP, Kampinos NP, Tuchola NP, Wigry NP), management has been focused on several species. We conclude that a lack of comprehensive management of invasive plant species in the majority of national parks currently limits the effectiveness of IAS (invasive alien species) eradication. Exchange of expertise among protected areas, documenting best practice examples, synthesising lessons learnt in IAS management, as well as the development of minimum standards for invasive plants surveillance and management are pivotal.

Northern red oak (Quercus rubra L.) is widely distributed in the eastern United States and southeastern Canada. It has also been introduced to Europe, where it has become an economically important plantation species now. Despite growing genomic resources, the number of available EST-SSR (expressed sequence tag – simple sequence repeat) markers for Q. rubra is still limited. Here, we used existing sequence information to provide a new set of EST-SSRs for northern red oak. In total, we report 20 polymorphic EST-SSRs, for which performance was evaluated in three Q. rubra populations from different regions in Michigan. We further tested the transferability of these markers to six additional oak species of section Lobatae (Quercus ellipsoidalis E.J. Hill, and Quercus georgiana M.A. Curtis) and Quercus (Quercus robur L., Quercus alba L., Quercus pedunculiflora K. Koch, and Quercus petraea (Matt.) Liebl.), as well as to European beech (Fagus sylvatica L.). The reported markers can be used in future population genetic studies.

SummaryIn the United States, diseased oaks (Quercus species) exhibit tip blight, branch and stem cankers, and dieback often attributed to Diplodia species or related fungi. Emergence of Diplodia corticola as a pathogen of European oaks, and reports of this fungus in the eastern and western United States, prompted re‐examination of strains from Wisconsin. These had been obtained in the late 1990s and early 2000s and previously identified only as Diplodia species. Nuclear ribosomal ITS sequences were obtained from the Wisconsin strains and analysed with other sequences from GenBank. Wisconsin strains confirmed as D. corticola were from northern red oak (Q. rubra), black oak (Q. velutina), white oak (Q. alba) and bur oak (Q. macrocarpa). Other strains from oaks in Wisconsin were D. mutila and D. seriata. Wound inoculation of northern red, white and bur oak seedlings with D. corticola in a greenhouse resulted in shoot death and stem lesions, from which the pathogen was reisolated. We conclude that D. corticola has been present in the northcentral United States for at least two decades and report two previously unrecognized hosts of this pathogen: white oak and bur oak. The roles of D. corticola, related fungi and influences of other environmental factors in deterioration of oak health in North America merit additional investigation.

Previous research by the authors found simulated acetochlor (with atrazine) and s-metolachlor drift to white oak at the leaf unfolding stage caused loss of interveinal tissues (leaf tatters). Reports of leaf tatters in the landscape and nursery settings are more common on white oak ( Quercus alba L.) than on northern red oak ( Quercus rubra L.). Our objectives were to determine if white and northern red oak differed in susceptibility to chloroacetanilide herbicides, if injury varied between chloroacetanilide herbicides, and if adding atrazine increased leaf injury. Two-year-old seedlings at the leaf unfolding stage were treated with acetochlor, s-metolachlor, and dimethenamid-P alone or combined with atrazine at 1%, 10%, and 25% of the standard field use rate. Within 6 days, all chloroacetanilides at 10% and 25% field use rates, alone or combined with atrazine, caused leaf tatter injury in both species. Acetochlor, s-metolachlor, and dimethenamid-P caused a similar type of leaf injury. Atrazine did not cause loss of leaf tissues or increase injury from chloroacetanilides. At 1% field use rate, only acetochlor, acetochlor + atrazine, and dimethenamid-P caused leaf injury to northern red oaks. The white oaks were not injured by all of the chloroacetanilide treatments at 1% field use rate. The northern red oaks were slightly more susceptible to chloroacetanilides compared with the white oaks. A second study found acetochlor only injured northern red oak when applied at the leaf unfolding stage and only at 25% of field use rate. Acetochlor at 1% field use rate did not injure red oak. Research is needed to explain the greater frequency of leaf tatters on white oaks than on northern red oaks in the landscape and to develop strategies to avoid tree injury.

In the landscape, loss of interveinal tissue in developing leaves (leaf tatters) is common for white oak (Quercus alba L.), but not northern red oak (Quercus rubra L.). Previous research identified the cause of leaf tatters, as exposure of unfolding leaves, to low concentrations of chloroacetanilide herbicides. Both white oak and northern red oak were injured by these herbicides at the leaf unfolding stage. Reports from landowners suggest white oak is injured more often than red oak, leading us to theorize that white and northern red oak leaves emerge at different times, and white oaks were more likely to be at the leaf unfolding stage when chloroacetanilide herbicides are applied. A study of comparative leaf phenology of white and northern red oak was done at three sites in Urbana, IL. Identifying oak pairs was challenging, and at each location, four to six paired mature white oak and northern red oak trees were used to observe phenological events. Key development stages (swollen bud, leaf unfolding, or fully expanded leaf stages) were considered to have occurred when reached by greater than 50% of the canopy. Northern red oak expanded leaf stage occurred earlier when compared to white oak. Time between phenological events was similar for both species. Although northern red oak leaves emerged earlier, there was a range of emergence times within short distances. Difference between locations illustrates the problem in predicting tree phenology even among populations a few kilometers apart. Leaf phenology alone does not explain leaf tatters, and other factors including distribution differences in oak species must explain landowner observations of tree injury. There was a strong correlation between growth phases of the two oak species with cumulative growing degree days, cumulative rainfall, and day length.

An endotrophic mycorrhiza was found during a study of the morphological forms of ectotrophic mycorrhizae of northern red oak (Quercus rubra L.) and southern red oak (Q. falcata Michx.). The endotrophic type was frequently found on short roots of 7 northern red oaks and 4 southern red oaks from each of 3 locations in the Mountain, Piedmont, and Sand Hills regions of North Carolina. The mycorrhizae are beadlike (FIG. 1), with 1-9 beads in succession, dull white, and range from 2 to 8 mm in length and 0.4 to 0.8 mm in diam. Root hairs were not observed. Occasionally branched forms were found and in all instances, the branches were also beaded. To avoid mistaking roots for those of surrounding plants, all root samples were carefully traced back to the tree in question. Microscopically the type is a typical vesicular-arbuscular endotrophic mycorrhiza with intracellular hyphae (FIG. 2), well developed arbuscular haustoria (FIG. 3), and intracellular vesicles (FIG. 4). There was no evidence of a fungal mantle or Hartig net. Attempts to grow the fungal symbiont in pure culture failed. This endotrophic mycorrhiza is similar to those formed by species of Endogone (Gerdemann, personal communication). Most mycorrhizae formed by species of Quercus are ectotrophic (Trappe, 1962); however, Henry (1933), reported an ectendotrophic mycorrhiza on Q. rubra. To find an endotrophic mycorrhiza commonly occurring on red oak is unusual and to my knowledge, the form described has not been previously reported. Descriptions of beaded endotrophic mycorrhizae have been reported on roots of Acer platanoides L. (Henry, 1933), A. rubrum L. (McDougall, 1914; Henry, 1934; Vozzo and Hacskaylo, 1964), A. saccharum Marsh. (Kessler, 1966), Amelanchier canadensis (L.) Medic. (Henry, 1934), Cornus florida L. (Henry, 1933), Ilex opaca Ait. (Vozzo and Hacskaylo, 1964), Liquidambar styraciflua L. (Vozzo and Hacskaylo, 1964; Filer and Toole, 1966), and Nyssa sylvatica Marsh.; Populus alba L.; Prunus serotina Ehrh.; and Sorbus americana Marsh. (Henry, 1934). The beaded endotrophic mycorrhiza described in this report is simi408