Red Maple Research Articles

Forest ecosystems in the eastern United States are undergoing significant compositional and demographic shift. To understand these changes, we used Forest Inventory & Analysis data (2003 - 2021) to examine landscape-scale trends in the North Carolina Piedmont, focusing on forest type groups, taxonomic family, and species. We assessed metrics such as annual net primary productivity, relative density, and biodiversity, aiming to determine: i) Which forest group types are changing most, ii) Whether these changes extend to lower taxonomic units, and iii) How stability has shifted over time. Our findings reveal an increasing dominance of Pinus species, particularly naturally regenerated loblolly pine (Pinus taeda), accompanied by sweetgum (Liquidambar styraciflua). This shift corresponds to rising prevalence of pine and oak-pine forest type groups. Notably, while red maple (Acer rubrum) consistently had high seedling densities, its recruitment lagged behind species like sweetgum and yellow-poplar (Liriodendron tulipifera), defying broader regional trends. These results highlight a clear progression from species-level changes to broader taxonomic families and forest types, emphasizing a shift toward pine in the region. The study underscores the importance of multi-level analyses for capturing ecological trends and advancing understanding of forest dynamics in changing landscapes.

This paper is the second in a series on the topic of contemporary issues in Québec’s temperate forest. It considers biological invasions that may either cause new and significant mortality among indigenous trees or substantially alter those species’ regeneration processes in the forest. Our review of government authority websites and scientific literature led us to identify 11 species that are vulnerable or highly vulnerable to exotic or emergent pests, 14 that are less vulnerable and 11 in an intermediate situation. The most vulnerable species do not include Québec’s three most abundant temperate hardwood species, namely sugar maple ( Acer saccharum Marsh.), red maple ( Acer rubrum L.) and yellow birch ( Betula alleghaniensis Britt.). They do, however, include certain maple forest companion species. We also identified three animal groups, two tree species, three shrub species and five herbaceous species groups that, if they were to invade the forest, could have significant consequences for entire stands as opposed to specific tree species, by disturbing the undergrowth. Invasions such as these enhance the risk of losing biodiversity and forest productivity, thereby making productivity less predictable and creating challenges for assisted tree migration initiatives. On the other hand, they offer a potential opportunity for mitigating the invasiveness of certain other species such as the American beech ( Fagus grandifolia Ehrh.).

We propose a series of papers presenting the main issues for Québec’s temperate forest arising from the multiplicity of rapid environmental and socioeconomic changes. This first paper presents a brief profile of Québec’s forests to establish a basis for the reflections presented in the remaining papers. Compilations show that the area dominated by deciduous species typical of the Northern temperate zone accounts for 8.8% of the province’s total forest, and that these species are also found mixed with coniferous species on 4.9% of the territory. The disturbances affecting these forests are generally more partial than severe. The most abundant species include shade-tolerant hardwoods such as sugar maple ( Acer saccharum Marsh., 152.4 Mm 3 ), red maple ( Acer rubrum L., 141.5 Mm 3 ), yellow birch ( Betula alleghaniensis Britt., 135.6 Mm 3 ) and American beech ( Fagus grandifolia Ehrh., 27.5 Mm 3 ). A demographic analysis shows that populations of the first 3 species have declined slightly in recent decades, whereas the American beech has tended to proliferate. Sugar maple and American beech are likely to become more abundant toward the northern boundary of their range, possibly due to climate change. However, beech bark disease may hinder the progression of the American beech in Québec.

Engineered wood composites are being crafted with increasingly smaller and smaller components, yet a search of the literature indicates a lack of intra-ring mechanical property data for almost all commercial wood types, particularly the underutilized low density hardwoods. In addition, there is no universally accepted testing regime for determining micromechanical properties of wood samples. As a result, we developed a testing system for determining compression, tension, and bending properties of growth ring regions of wood samples. Our microtesting system consists of a 45.4 kg load stage, motor drive, data acquisition system, motor control, load cell, strain transducer, and software. In this study, intra-ring compression strength parallel to the grain was determined for small samples (a few ml3 in volume) of sweetgum (Liquidambar styraciflua), yellow-poplar (Liriodendron tulipifera), and red maple (Acer rubrum). It was determined that compression strength is weakly correlated with specific gravity but unrelated to growth rate. Specific gravity was also unrelated to growth rate. Sweetgum values were intermediate between yellow-poplar and red maple.

ABSTRACT Frequent fire historically maintained vegetation dominated by oak (Quercus), pine (Pinus), and other pyrophilic (fire-dependent) taxa in the eastern U.S. However, uncertainty remains about the spatial extent of pyrophilic versus pyrophobic (fire-sensitive) species across the landscape. We investigated the abundance and extent of pyrophilic and pyrophobic tree species as well as open, treeless areas along the southern Blue Ridge Escarpment, northeastern Georgia, using a series of historical and ecological datasets representing multiple periods over the past 250 years. Pyrophilic tree taxa covered most of the landscape under traditional land use by the Cherokee and, subsequently, Upland Southerners with a heritage of burning. Oak was the foundational genus, accounting for about half of all trees. American chestnut (Castanea dentata), pines, and hickories (Carya) composed most remaining trees. These species apparently formed open forests and woodlands, with treeless patches (e.g. grasslands, severely burned forest) interspersed. Pyrophobic species were largely restricted to fire-sheltered areas near streams. However, following early-twentieth-century logging and then fire exclusion, the forests grew denser. The pyrophobic red maple (Acer rubrum) expanded vigorously on mesic and xeric sites alike and is becoming poised to dominate the forest.

Abstract Understanding historical dynamics of peripheral populations over the Holocene provides key insights to anticipate species responses to ongoing global changes. A marginal stand at the leading edge of sugar maple (Acer saccharum) range was hereby investigated to infer the Holocene dynamics of sugar maple, red maple (Acer rubrum), eastern white pine (Pinus strobus), three prominent temperate tree species of the boreal–temperate forest ecotone in eastern Canada. Soil macrofossil charcoal analysis of 25,595 charred wood particles revealed that white pine is detected at this marginal temperate forest site since the early Holocene, red maple since the mid‐Holocene and sugar maple since the late‐Holocene. The transition from the warmer mid‐Holocene to the cooler late‐Holocene was marked by a decrease of white pine, which was expected because the environmental envelope of temperate species shifted southward in response to lower mean temperatures of the Neoglacial. In contrast, the abundance of sugar and red maples increased during the cool late‐Holocene period. There was a significant lag between the establishment of maples, whereby the hardier red maple was found since the warmer mid‐Holocene, while the cold intolerant sugar maple was only detected during the cooler late‐Holocene. A shift in the fire regime, a disruption of coniferous priority effects in the soil, as well as the introduction of shared mycorrhizal fungi might tentatively explain the late establishment of maples and the migration lag between the two species. Synthesis. As temperate tree species require warmer temperatures than boreal species, some thermophilous species such as white pine increased in abundance at their northern edge during historically warmer periods. Our data reveal that not all temperate species behaved accordingly: maples were scarce during the warm mid‐Holocene, while their abundance increased during the cool late‐Holocene. A migration lag suggests that an earlier arrival of generalist species such as red maple might be required to facilitate the later establishment of specialists such as sugar maple. The historic decoupling between macroclimatic trends and temperate species range shift sheds new light on the potential responses of the boreal–temperate ecotone facing modern‐day anthropogenic climate change.

Environmental stresses rarely occur in isolation, in fact plants often combat multiple stresses at once. Moreover, while most studies examining the combined effect of different factors have focused on greenhouse experiments, comparing experimental results with field studies is necessary to validate results. Here, we examine the effect low water and light on the growth of Acer rubrum, A. saccharum, and Quercus rubra in a greenhouse and the field. We tested whether the combined effects were additive, synergistic, or antagonistic and studied if these responses were mediated by functional traits. In the greenhouse we found an additive effect of the two stresses across species, however individual species responded differently with A. rubrum showing additive, and A. saccharum and Q. rubra showing antagonistic effects. Species were unique in their trait responses, but species with antagonistic effects tended towards more acquisitive strategies belowground. Our field results partially matched our greenhouse findings, with water and light stress resulting in additive effects in all species except for A. saccharum. Our results suggest that A. saccharum and Q. rubra may be better equipped to cope with low light and water, and that studies should be careful to extrapolate from greenhouse studies on multiple stress response alone.

ABSTRACTThe plant–mycorrhizal fungi relationship can range from mutualistic to parasitic as a function of the fungal taxa involved, plant ontogeny, as well as the availability of resources. Despite the implications this relationship may have on forest carbon cycling and storage, we know little about how mature trees may be impacted by mycorrhizae and how this impact may vary across the landscape. We collected growth data of two arbuscular mycorrhizal fungi (AMF)‐associated tree species, Acer rubrum and A. saccharum, and one ectomycorrhizal fungi (EMF)‐associated tree species, Quercus rubra, to assess how the mycorrhizal fungi–plant association may vary along a gradient of nitrogen (N) availability. Individual assessments of fungal taxa relative abundances showed non‐linear associations with tree growth; positive associations for the two AMF‐associated trees were mostly under low N, whereas positive to neutral associations for the EMF‐associated tree mainly took place at high N. Only A. rubrum exhibited greater tree growth with its tree soil‐specific mycorrhizal community when compared with predictions under a random mycorrhizal soil community. Because mycorrhizal fungi are likely to mediate how plants respond to warming, increasing levels of N deposition and of atmospheric CO2, understanding these relationships is critical to accurately forecasting tree growth.

Abstract The duration of tree seedling persistence in the understory varies greatly between forests and across environmental conditions within a forest ecosystem. To examine species‐level variation in understory persistence and passage to the sapling life stage, we followed 5236 seedlings in single‐tree canopy gaps and closed canopy conditions over three years and simulated seedling passage times and the number of seedlings required to produce one 1.5‐m tall sapling of five common tree species in a hemlock–hardwood forest of Massachusetts, USA. Averaged across species, it took 26 years in gaps and 31 years under closed canopies to go from a first‐year seedling to a 1.5‐m sapling. Across species, the average number of seedlings needed for one sapling was 294 in gaps and 2674 in closed canopy environments. We observed high interspecific variation in passage times and number required for one sapling. Betula congeners and Pinus strobus took less time and significantly fewer individuals than Acer rubrum and Tsuga canadensis, which are generally regarded as more tolerant of understory conditions. The largest intraspecific difference in gaps versus closed canopy environments was for Quercus rubra, where we estimated the number of seedlings required to produce one sapling in closed canopies to be 172 times higher than in gaps. Stem breakage also increased the number of seedlings needed per sapling, especially in closed canopy environments. We evaluated our estimates in the lab by aging cross‐sections obtained from seedlings in gap and closed canopy conditions. Compared to our empirical age‐to‐height relationships, most simulations tended to underpredict seedling age for a given height, suggesting that passage times may be even longer than our simulations indicated. Our study shows that trees can persist for decades in the seedling life stage, highlighting a need for better‐parameterized recruitment processes in demographic forecasting.

Abstract The grazing impact on epiphytic lichens by a non-native gastropod species is documented and quantified for the first time in the province of Newfoundland and Labrador using a unique combination of a multiple-choice feeding design with lichen transplant techniques under controlled laboratory conditions. The feeding experiment included three arboreal lichen species sewn onto a mesh and attached to red maple sticks inside a terrarium where four Cepaea nemoralis snails were introduced and allowed to graze over a five-day period. The three lichen species used in the feeding trials included the green-algal Platismatia glauca, the cephalolichen Lobaria pulmonaria, and the cyanolichen Lobarina scrobiculata. The trials also included two sets of L. pulmonaria from different regions of the island of Newfoundland. The levels of grazing and preference by the snails was very high. Herbivory was high for all lichen species but was highest for Platismatia glauca, for which 70% of thalli were consumed after only 24 hours. Our results show that C. nemoralis is probably affecting the distribution and abundance of epiphytic lichens in the forests of Newfoundland and Labrador. Furthermore, our observations of intense herbivory on reproductive structures challenges the universal application of the optimal defence theory in lichens.

Understanding how mixed-species forests uptake subsurface water sources is critical to projecting future forest water use and stress. Variation in root water uptake (RWU) depths and volumes is common among trees but it is unclear how it is affected by species identity, local water availability or neighboring tree species compositions. We evaluated the hypothesis that RWU depths and the age of water (i.e., time since water entered soils as precipitation) taken up by red maples (Acer rubrum) varied significantly between two forested plots, both containing red maples, similar soils, topography and hydrologic conditions, but having different neighboring tree species. We measured soil moisture contents as well as stable isotopes (δ2H, δ18O) in plant xylem water and soil moisture across two years. These data were used to calibrate process-based stand-level ecohydrological models for each plot to estimate species-level RWU depths. Model calibration suggested significant differences in red maple tree RWU depths, transpiration rates and the ages of water taken up by maples across the two stands. Maple trees growing with ash and white spruce relied on significantly deeper and older water from the soil profile than maple trees growing with birch and oak. The drought risk profile experienced by maple trees differed between the plots as demonstrated by strong correlations between precipitation and model simulated transpiration on a weekly time scale for maples taking up shallow soil moisture and a monthly time scale for maples reliant on deeper soil moisture. These findings carry significant implications for our understanding of water competition in mixed-species forests and for the representation of forest rooting strategies in hydrologic and earth systems models.

Introduction: The Red Maple Trials Naturalistic Exposure Chamber™ (NEC™) is a fixed, live-cat exposure chamber, wherein allergen shed from two resident cats is aerosolized using a modified robot vacuum. The EnviroMini™ is a portable allergen exposure tent, in which allergen (Fel d 1, primarily) from milled cat hair is aerosolized in a similar manner. This is a single-center validation study designed to compare the allergic response to cat antigen provocation in the EnviroMini to the response in the previously validated NEC. Methods: Eight cat allergic subjects were randomized to undergo sequential 2-h allergen challenges in the EnviroMini and the NEC, 28 or more days apart. A modified robot vacuum aerosolized cat allergen in both chambers. Airborne Fel d 1 was measured using ELISA. Nasal, ocular, and chest symptoms were recorded every 10 min and spirometry every 20 min. Challenges were stopped and not repeated if FEV1 fell >20% of baseline during the exposure. Results: Fifteen subjects completed at least one challenge, and eight completed both (“per-protocol”). Mean total nasal symptom score (TNSS) averaged over the last 30 min (“plateau”) was not significantly different between the EnviroMini and NEC (paired t test, p = 0.16; mean [SE] 6.1 [1.2] and 4.5 [0.6], EnviroMini and NEC, respectively). There was no difference in FEV1 change between the two challenges (p = 0.90). The same results were found for all subjects as for the per-protocol group. TNSS plateau was not correlated with Fel d 1 exposure, and there was no difference in average Fel d 1 concentrations between the chambers (EnviroMini: 55; NEC: 54 ng/m3). Conclusion: The EnviroMini offers comparable cat allergen exposure and nasal and respiratory responses to the NEC. Its portability facilitates expansion to multisite chamber studies for clinical validation of allergy therapies. Future work could expand its capabilities to other aeroallergens.

Tulip poplar (Liriodendron tulipifera) is a member of the Magnolia family, is a large, fast-growing, long-lived, deciduous tree native to eastern North America. One-year-old tulip poplar seedlings grown under field conditions in a commercial nursery in Warren County, Tennessee, exhibited severe root rot in May 2024. Dark brown to black lesions were observed on the affected roots. Disease severity was 60% of the affected root area, and disease incidence was 45% of 300 plants. Symptomatic root tissues were surface-disinfected with 70% ethanol and washed twice with distilled water. Small sections of root tissue were placed in Petri dishes containing V8-PARPH (V8 juice agar amended with pimaricin, ampicillin, rifampicin, pentachloronitrobenzene, and hymexazol) agar and incubated at 24°C in an 8-hour photoperiod cycle. After 3 days of incubation, whitish cottony mycelia with radiate and chrysanthemum flower-like growth patterns were observed (Supplementary Fig. 1a). The hyphae were coenocytic and 5.5 μm wide. Sporangia were subglobose with papillate, filamentous to globose smooth oogonia (18.35 to 23.86 μm; n = 50), bell-shaped antheridia, and spherical zoospores that are characteristic of Phytopythium vexans (de Cock et al. 2015) (Supplementary Fig. 1b and c). Total DNA was extracted (DNeasy PowerLyzer Microbial Kit) from 7-day-old isolates FBG7781-1 and FBG7781-2 and amplified using the ITS1/ITS4 (White et al. 1990), NL1/NL4 (Baten et al. 2014), Levup/Fm85mod (Robideau et al. 2011) and Cox2F/Cox2RC4 (Hudspeth et al. 2000) primer pairs. Isolates were sequenced using for genetic markers, including the ribosomal internal transcribed spacer (ITS), the 28S large subunit (LSU) of ribosomal RNA, the mitochondrial cytochrome c oxidase subunit I (COXI) and cytochrome c oxidase subunit II (COXII), respectively. The sequences (GenBank accession nos. PQ555199 and PQ555200 for ITS, PQ555205 and PQ555206 for LSU, PQ562067 and PQ562068 for COXI, and PQ562065 and PQ562066 for COXII) were 100% identical to the ITS, LSU, COX1, and COXII genetic markers of P. vexans isolates in GenBank (ITS: PQ050141, LSU: AB468723, COXI: GU133478, COXII: AB468910). Pathogenicity tests were performed on 1-year-old tulip poplar seedlings grown in 1-gal containers (3.8 L) to fulfill Koch's postulates. Tulip poplar seedlings were drenched and inoculated (150 ml/plant) with a pathogen slurry (two plates of 7-day-old culture/liter) as described in Panth et al. 2021, using isolates FBG7781-1 and FBG7781-2 (five plants per isolate). Five plants were drenched with V8-PARPH agar slurry without the pathogen and served as controls. The study was conducted in a greenhouse maintained at 21 to 23°C and 70% relative humidity and watered twice daily for 2 min using an overhead irrigation system. Fifteen days after inoculation, dark brown lesions developed in the roots of all inoculated plants (Supplementary Fig. 2a). No symptoms were observed in the control plants (Supplementary Fig. 2b). Isolates resembling the morphological characteristics of P. vexans were recovered from inoculated plants using the method described above, and their identity as P. vexans was confirmed by DNA sequencing with the same four primer pairs previously described. Phytopythium vexans has been reported to cause root rot in flowering cherry, ginkgo, red maple, and redbud in Tennessee (Baysal-Gurel et al. 2021, Liyanapathiranage et al. 2023, Panth et al. 2021). To our knowledge, this is the first report of P. vexans causing root rot of tulip poplar in Tennessee, the United States and worldwide. This finding is significantly important for the development of a successful disease management strategy for P. vexans in tulip poplar.

Acer rubrum is a widespread Acer species valued for its vibrant autumn foliage. The UGT (UDP-glycosyltransferase) gene family is integral to the biosynthesis of anthocyanins, the pigments responsible for leaf coloration. This study aimed to comprehensively identify and characterize the UGT gene family in the A. rubrum genome. The results of the phylogenetic analysis of 249 ArUGTs revealed 18 distinct subgroups. Conserved motif analysis demonstrated structural similarities within subgroups. Gene duplication analysis identified 21 tandem and 66 segmental duplication events across chromosomes. Transcriptomic data from autumn leaves of different colours and under low-temperature stress were analyzed for ArUGT expression patterns. Compared to controls, 44 UGTs were upregulated and 99 downregulated in yellow leaves, while 59 were upregulated and 84 downregulated in red leaves. Low-temperature treatments showed upregulation of 18 UGTs at 10 °C and 40 UGTs at 4 °C. Downregulation was observed in 7 UGTs at 10 °C and 33 UGTs at 4 °C. Among all UGT genes, ArUGT52 was common in highly expressed genes in both red leaf and low-temperature stress. Furthermore, the transient overexpression of ArUGT52 in tobacco plants demonstrated cytoplasmic localization and a marked increase in anthocyanin levels under cold stress. In vitro, biochemical assay results indicated that the ArUGT52 was involved in anthocyanin biosynthesis via the glucosylation of anthocyanidins. This study provides insights into the genetic mechanisms of leaf coloration and the potential of UGT manipulation for enhancing plant responses to low-temperature stress. These findings have applications in ornamental horticulture and agriculture.

Abstract In this study, the modulus of elasticity of red maple (Acer rubrum) veneer, a native species abundant in eastern North America, was evaluated. These veneer sheets were 3.5 mm thick by 304 mm wide by 2.44 m long. Over 500 specimens were visually graded and subjected to a nondestructive stress wave test to determine the dynamic modulus of elasticity (MOEd). Subsequently, 60 specimens were selected for tensile testing to measure the static modulus of elasticity (MOEs). The average MOEd was 19.10 GPa, while the MOEs obtained from tensile testing was 11.88 GPa. This tension-based MOE value was very close to the bending test value for red maple lumber reported in the wood handbook (11.31 GPa). A regression analysis was conducted to evaluate the effects of density and defects on MOE. The results showed that density has a greater effect on MOEd than defects. A correlation was also developed between MOEd and MOEs. The results showed that the MOEd was 60 percent higher than the MOEs, with a weak positive correlation (r = 0.40). The stress wave velocity, as affected by different factors such as density, defects, and fiber orientation, strongly correlated with MOEd.

Canopy hydrology and forest water inputs are directly linked to the physical properties of tree crowns (e.g., foliar and woody surfaces), which determine a tree’s capacity to intercept and retain incident rainfall. The changing forest structure, notably the decline of oak’s (Quercus) dominance and encroachment of non-oak species in much of the upland hardwood forests of the eastern United States, challenges our understanding of how species-level traits scale up to control the forest hydrologic budget. The objective of this study was to determine how the leaf water storage capacity varies across species and canopy layers, and how these relationships change throughout the growing season. We measured the leaf water storage capacity of overstory and midstory trees of native deciduous oaks (Q. alba, Q. falcata, Q. stellata) and non-oak species (Carya tomentosa, Acer rubrum, Ulmus alata, Liquidambar styraciflua, Nyssa sylvatica) using two methods (water displacement and rainfall simulation). Overstory Q. alba leaves retained 0.5 times less water per unit leaf area than other overstory species (p < 0.001) in the early growing season, while in the late growing season, C. tomentosa leaves had the lowest storage capacity (p = 0.024). Quercus falcata leaves displayed a minimal change in storage between seasons, while Q. alba and Q. stellata leaves had higher water storage in the late growing season. Midstory U. alata leaves had 3.5 times higher water storage capacity in the early growing season compared to all the other species (p < 0.001), but this difference diminished in the late growing season. Furthermore, the water storage capacities from the simulated rainfall experiments were up to two times higher than those in the water displacement experiments, particularly during the early growing season. These results underscore the complexity of leaf water storage dynamics, the methodology, and the implications for forest hydrology and species interactions. Broader efforts to understand species-level controls on canopy water portioning through leaf and other crown characteristics are necessary.

Soil-plant indicators are useful to select tree species suitable for the urban conditions and to maximize the benefits provided by green infrastructures (GE). To identify effective indicators for GE, soil-plant nutrient interaction and related physiological responses were assessed in evergreen (Cupressus sempervirens L.) and deciduous (Acer opalus Mill., Acer rubrum L., Tilia platyphyllos Scop., Ulmus ‘Plinio’) tree species, in a novel urban GE (Florence, Italy). Soil and leaf nutrient contents and the soil enzyme stoichiometry were applied as indicators of plant nutrient status and bioavailability. Gas exchange and stable isotopes of carbon (C) and nitrogen (N) were used as indicators of tree physiological status and resource-use strategies, respectively. The soil was suitable for tree growth, however, the enzyme activities estimated N limited condition. Trees differed in leaf nutrient composition and stoichiometry. Acer rubrum and A. opalus leaves had manganese concentration below and above the plant optimal range, respectively, leading to alteration in the nutrient uptake and on the leaf stoichiometry between C, N and phosphorus (C: N:P), with consequence for tree health status. Tilia platyphyllos and Ulmus ‘Plinio’ had the best photosynthetic performance, while photosynthesis in A. rubrum was severely impaired. Interspecific differences in N- and water-use strategies were observed. Tilia platyphyllos showed the highest water-use efficiency, leaf C: P and N: P compared to the other species. Tree nutritional and physiological traits gave insights into soil-plant nutrient interaction and may be proposed as useful indicators for choosing the most suitable species to improve GE management in urban environments.

The modulus of elasticity (MOE) of structurally graded one-inch-thick red oak (Quercus rubra) and red maple (Acer rubrum) lumber was measured in this work. The center-point, third-point static loading tests, and the stress wave timer methods were used. The objective was to determine if there are statistical differences between three structural lumber grades based on their MOE values. The study considered both the within separated grades and the across combined grades. For red oak and red maple, significant differences in MOE values from center-point static loading tests were observed solely between Select Structural and Below-grade lumber. With the dynamic method, no significant differences were found between any visual grades, including Below-grade lumber. Regardless of the MOE determination method used, the MOE value was not useful for distinguishing the structural, No. 2, and No. 3 visual grades. The strongest correlation existed between the global MOE and the dynamic MOE, which was even higher when the analyses were conducted on separated visual grades. In the case of red maple, stronger correlations between the dynamic MOE, local MOE, and global MOE were observed when separated by visual classes, compared to the analysis conducted on the combined grades. The global MOE was found to be a better predictor of the local MOE than the dynamic MOE.

Swamp white oak (Quercus bicolor) is a North American species of medium-sized trees in the beech family. One-year-old swamp white oak seedlings grown in field conditions in a commercial nursery in Warren County, Tennessee exhibited severe root rot in July 2024. Dark brown lesions were observed in the affected roots (Fig. 1a). Disease severity was approximately 40% of root area affected, and disease incidence was approximately 20% of 100 plants. Symptomatic fine root tissues were surface sterilized with 70% ethanol and rinsed twice with distilled water. Then, symptomatic root parts (1-cm pieces) were plated on V8-PARPH (V8 juice agar amended with pimaricin, ampicillin, rifampicin, pentachloronitrobenzene, and hymexazol) and incubated at 24°C under an 8-hour photoperiod. The rosette pattern accompanied by whitish mycelium resembling Phytopythium species was consistently observed after three days of incubation. Sporangia were globose or subglobose (19.11±1.71 μm, n=50) with or without papilla (Fig. 1b). Oogonia were smooth, filamentous to globose (21.04±1.74 μm, n=50) (Fig. 1c). Representative isolates (FBG7779-1 and FBG7779-2) were identified as Phytopythium vexans based on morphological characterization (de Cock et al. 2015; Ghimire and Baysal-Gurel 2023). To confirm pathogen identity, total DNA was extracted using the DNeasy PowerLyzer Microbial Kit from 7-day-old cultures of the isolates grown on V8-PARPH. The primer pairs ITS1/ITS4 (White et al. 1990), NL1/NL4 (Baten et al. 2014), OomCoxI-Levup/Fm85mod (Robideau et al. 2011), and Cox2-F/Cox2-R (Hudspeth et al. 2000) were used to amplify and sequence the ribosomal internal transcribed spacer (ITS), the large subunit (LSU), and the mitochondrial cytochrome c oxidase subunits I (CoxI) and II (CoxII) genetic markers, respectively. The ITS, LSU, CoxI and CoxII sequences of the isolates FBG7779-1 and FBG7779-2 (ITS: PQ567140 and PQ567141; LSU: PQ567376 and PQ567377; CoxI: PQ570510 and PQ570511; CoxII: PQ570512, and PQ570513) were 100% identical to those of P. vexans isolates MK011115, OQ754108, GU133478, and AB468910, respectively. To complete Koch's postulates, pathogenicity test was performed on two-year-old swamp white oak seedlings (165 to 170 cm height) grown in 3-gal containers. The plants were drench inoculated with pathogen slurry (150 ml per plant - two 9-cm plates of 7-day-old culture/liter) of the isolates FBG7779-1 and FBG7779-2 (five plants per isolate) (Panth et al. 2021). Five plants were drenched with agar slurry without the pathogen and served as a non-inoculated control plant. The study was conducted in a greenhouse condition (21 to 23°C, 70% relative humidity) and irrigated twice a day for 2 min each time using an overhead irrigation system. Two weeks after inoculation, dark brown lesions developed in the roots of all inoculated plants (Fig. 1d), whereas controls remained healthy (Fig. 1e). The morphology of the pathogen isolated on the V8-PARPH medium was identical to the original isolate and confirmed by sequencing the ITS, LSU, CoxI and CoxII markers. Phytopythium vexans has been previously reported to cause root and crown rot in flowering cherry, ginkgo, red maple, and redbud in Tennessee (Baysal-Gurel et al. 2021; Liyanapathiranage et al. 2023; Panth et al. 2021). To our knowledge, this is the first report of P. vexans causing root rot of swamp white oak in Tennessee and the United States. Identifying the pathogen as the causal agent is crucial in the development of a successful disease management strategy of P. vexans on swamp white oak.

Abstract Forest ecosystems with altered nutrient limitations are a common legacy of acidic deposition in North America. Continued acidic deposition has lowered soil pH and revealed phosphorus (P) limitations in many temperate forest ecosystems. Previous studies exploring P limitations or co‐limitations are often short term, and thus may potentially show a response to limitation that is not sustained over time. To better understand how a forest's response to P limitation and acidic deposition can change over time, we added P, limestone to raise pH, and a cross‐treatment where both P and limestone were added to 3 different northeastern Ohio forest stands over a 12‐year period. We tracked diameter at breast height of the trees annually, conducted foliar nutrient analyses, and collected tree roots to assess treatment impacts on mycorrhizal colonization. We analyzed our dataset in three sections: the first 6 years after manipulation, the latter 6 years, and the entire 12‐year period. These sections allowed us to compare differences between early responses to manipulation and later responses. Here, we found that P additions increased basal area growth across multiple species and throughout the entire study, confirming that our forest trees are P‐limited. Cross‐treatments similarly increased basal area growth, but not as much as P additions alone. Some species saw waning effects of treatment in the second half of the study. This could be due to changes in weather patterns, an adjustment of the study system's equilibrium, or the emergence of beech leaf disease in 2014, which has led to the decline of Fagus grandifolia. Early successional species such as Acer rubrum began to benefit from treatments after beech leaf disease killed canopy F. grandifolia trees, perhaps first being light‐limited, but later able to take advantage of the nutrient additions and pH alteration of their soils. Our results suggest that in forests subject to acidic deposition, soil P may co‐limit tree growth, but responses are species dependent.