Quercus Macrocarpa Michx Research Articles

Trading tree growth for soil degradation: Effects at 10 years of black plastic mulch on fine roots, earthworms, organic matter and nitrate in a multi-species riparian buffer

This study assessed the effects of two vegetation management treatments (black polyethylene mulch and a control treatment) on tree growth, fine root biomass of trees and of competing vegetation, earthworms, and physiochemical soil properties in a 10 year-old agricultural riparian buffer planted in southern Québec (Canada) with five trees species: Populus × canadensis Moench (hybrid poplar), Fraxinus pennsylvanica Marsh. (red or green ash), Quercus macrocarpa Michx. (bur oak), Quercus rubra L. (red oak), and Pinus strobus L. (eastern white pine). Vegetation management treatments had a significant effect on tree growth, fine root biomass, earthworms and on many soil properties. Overall, the use of plastic mulch increased tree growth in all species (not to the same extent), but locally decreased soil organic matter, total soil carbon, total soil nitrogen, earthworm biomass and abundance, competing vegetation fine root biomass and the biomass of the total pool of fine roots. Also, more than three times more soil nitrate was measured under mulch despite the higher tree growth. Lower soil phosphorus availability (in some species), base cation saturation and moisture content under the mulch suggested higher uptake of these soil resources to sustain high tree growth. Across treatments and species, significant and strong correlations were observed between total fine root biomass and soil carbon, between competing vegetation fine root biomass and earthworm biomass, and between total soil carbon and earthworm biomass. These highlight the central role of the total pool of fine roots in maintaining or enhancing soil carbon, the importance of understory herbaceous vegetation for earthworm populations and the importance of organic matter as a factor limiting earthworm activity. Species × Treatment interactions were observed on tree growth, fine roots, and earthworms. Pine growth was little enhanced by the mulch and its fine root biomass peaked in the control treatment, suggesting plasticity in allocation to fine roots in response to resource limitations. Pine had similar earthworm biomass across both vegetation management treatments, with two to three times less earthworm biomass than other tree species observed in control plots, reflecting its low needle litter quality. Only poplar and ash had higher tree fine root biomass under the mulch. Red oak was the species the most negatively affected by herbaceous competition. In practice, plastic mulch is rarely removed from tree plantation sites. This should change in a context where plastic mulch is increasingly used as an alternative to herbicide, and where riparian agroforestry projects need to meet both timber and non-timber objectives (carbon sequestration in the soil and in tree biomass, N and P storage in woody biomass, soil quality restoration), while minimizing their impacts in terms of nitrate leaching. Identifying alternative mulching materials and strategies that would provide high growth benefits without degrading the soil or water quality is a priority to optimize ecosystem services provision in tree plantations and riparian buffers.

Growth and stem quality of hardwood trees planted 18–29 years ago on abandoned farmland following recommended silvicultural practices

The objective of this study is to provide an account of the growth results of valuable hardwood plantations several decades old which have received silvicultural treatments recommended for planting hardwoods on abandoned farmland. Diameter growth and stem quality of sugar maple (Acer saccharum Marsh.), black walnut (Juglans nigra L.), bur oak (Quercus macrocarpa Michx.) and red oak (Quercus rubra L.) are analysed. Data were from 15 plantations located in south-western Quebec. The mean annual diameter increments were highest for red oak (0.83 cm yr-1) and black walnut (0.75 cm yr-1), and lowest for bur oak (0.55 cm yr-1) and sugar maple (0.51 cm yr-1). These values are comparable to, or exceed, the best rates in the literature. A mean proportion of 78% to 95% of the first log without defects were produced, depending on the species. Tree mean densities (640 trees/ha) will allow a selection of better stems by thinning. Elite trees have diameters that are 17% to 23% above the average. These results lead us to believe in the potential for the production of quality hardwood timber in plantations in Québec.

Bur oak (Quercus macrocarpa) biomass production on a former coal mine site: positive effects of coppicing on rapid recovery of growth and yield

Ten-year-old bur oak (Quercus macrocarpa Michx.) saplings established on the exposed, infertile, treeless barrens of a former coal mine site in New Brunswick, Canada, were harvested to assess the effects of subsequent coppicing on regrowth parameters and biomass production. Two years after harvesting, coppice height growth exceeded that of the original 10-year-old saplings by 20%. Mean stem numbers were 1.2 and 6.7 for 10-year-old and coppiced trees, respectively. Mean dry mass recovered after 2 years with 214, 112, and 207 g for 10-year-old saplings and the 1- and 2-year-old coppices, respectively. Site quality of the broken shale rock overburden was similar across four of the five sites, with the exception that one site had twice the soil nitrogen (N) at 0.123% than the other four site types, which had an average of 0.064% N. This high N site had 2.3-fold the productivity of the mean for the other four sites. Mean coppice stem height showed the strongest predictive relationship to total coppice dry mass when compared with the greatest stem height, greatest or mean stem basal diameter, or coppice stem number. The most dramatic result of this bur oak coppicing experiment was the rapid recovery of height growth, biomass production, and observable stem quality within coppices over the 2-year period following harvesting of the original, 10-year-old saplings.

Forest adaptation strategies aimed at climate change: Assessing the performance of future climate-adapted tree species in a northern Minnesota pine ecosystem

Climate change is expected to impact the function, health, and productivity of many northern latitude forests, including North American mixed-pine ecosystems. Additionally, forest managers face increasing challenges to sustaining forests in the face of high uncertainty associated with response to climate change. The Adaptive Silviculture for Climate Change (ASCC) project was developed to provide operational-scale research opportunities to assess and demonstrate various adaptation approaches to forest management in regionally important forest types. The ASCC project framework includes three treatments (resistance, resilience, and transition) representing a gradient of silvicultural approaches aimed at climate change. The first of five ASCC installations is located on the Cutfoot Experimental Forest-Chippewa National Forest (CEF), Minnesota USA, in a mixed-species northern pine forest. Using habitat suitability models under projected future climates, as well as expert opinion, we chose eight future climate-adapted species for planting as part of the transition treatment, consisting of four native species to the CEF: eastern white pine (Pinus strobus L.), northern red oak (Quercus rubra L.), bur oak (Quercus macrocarpa Michx.), and red maple (Acer rubrum L.); and four novel species to the CEF: white oak (Quercus alba L.), bitternut hickory (Carya cordiformis Wangenh.), black cherry (Prunus serotina Ehrh.), and ponderosa pine (Pinus ponderosa C. Lawson). The seedlings were planted under two canopy conditions, a thinned matrix (14–18 m2 ha−1 residual basal area) and 0.2-ha gap openings (through harvesting). We measured how overstory canopy conditions (gap openings versus a thinned matrix) and understory shrub/herbaceous cover affect species performance. We measured 45 plots over the course of three growing seasons (Spring 2016 – Fall 2018), taking measurements of seedling basal diameter and survival, as well as estimates of understory vegetation density. Our findings highlight strong variations in species performance across treatment conditions. While overstory canopy condition was found to be a weak predictor of seedling survival and growth, our results show post-treatment colonization of understory shrub/herbaceous cover being a strong predictor of seedling survival (p < 0.001), with 86.67% (±8.04; 1 standard error) of seedlings surviving in the lowest understory cover class, and 74.23% (±3.04) surviving in the highest understory cover class. Seedling growth did not appear affected by understory shrub/herbaceous cover. Additionally, growth and survival varied significantly among native and novel seedlings, with ponderosa pine exhibiting the highest growth rates at 0.31 cm cm−1 year−1 (±0.004), while also having the lowest survival of any species at 45.66% (±1.2). Results from this study can be directly used by managers to inform planting decisions and species selections that align with management planning to promote forest health and sustainably in the face of climate change.

Weed control and overstory reduction improve survival and growth of under‐planted oak and hickory seedlings

Weed control and overstory reduction are important silvicultural treatments for improving survival and growth of under‐planted oak and hickory seedlings. Mast‐producing trees in the bottomland forests of the blackland prairie and Post Oak Savannah ecoregions of Texas have declined in abundance. Oaks and hickories have been replaced by more shade‐tolerant species, including green ash (Fraxinus pennsylvanica Marshall) and sugarberry (Celtis laevigata Willd.), which do not produce significant hard mast for priority wildlife species. A split‐plot experiment design was installed on three sites at Richland Creek Wildlife Management Area in Freestone County, Texas, studying the effects of canopy coverage and competition control on survival and growth of bur oak (Quercus macrocarpa Michx.), Shumard oak (Quercus shumardii Buckl.), and pecan (Carya illinoinensis (Wagenh.) K. Koch) seedlings. Uprooting by hogs shortly after planting resulted in greater than 90% mortality of pecan on the two lower elevation sites. Year one survival of Shumard oak was significantly higher than bur oak. However, bur oak was more preferred by hogs than Shumard oak. Year one growth of bur oak was significantly greater than Shumard oak. Severe flooding during the second growing season caused complete mortality on the lower two sites. None of the species were well suited to such prolonged (3–4 months) inundation as seedlings. On the remaining site, density reduction and weed‐barrier mats improved growth and survival while herbaceous weed control with herbicides actually reduced both growth and survival.

Black Plastic Mulch or Herbicide to Accelerate Bur Oak, Black Walnut, and White Pine Growth in Agricultural Riparian Buffers?

This study was conducted in a riparian buffer bordering a 1 km segment of a headwater stream crossing a pasture site located in southern Québec (Canada). Three species were planted (black walnut (Juglans nigra L.), bur oak (Quercus macrocarpa Michx.), and eastern white pine (Pinus strobus L.)) with three vegetation treatments (control, herbicide (one application/year for 3 years), and black plastic mulch)). The main objective was to determine to which extent herbicide and plastic mulch, used with species having different ecological characteristics, affect tree growth and soil nutrient status in riparian buffers. Survival was high (&gt;93%) for all species in all treatments. In the control (no vegetation treatment), growth was similar among species. Black walnut had the strongest growth response to herbicide and plastic mulch, and white pine had the weakest. For all species, growth was similar in the herbicide and the plastic mulch treatments. During the fifth growing season, plastic mulch increased soil nitrate and phosphorus compared to the herbicide treatment. In the plastic mulch treatment, higher soil nitrate supply was observed for species that preferentially uptake ammonium (black walnut and white pine). Soil nutrient supplies were similar between the control and herbicide treatments. Despite the more favorable nutritional conditions it provides, permanent black plastic mulching does not provide higher growth benefits after 5 years than a 3-year herbicide treatment. The high soil nitrate supply observed in mulched black walnut and mulched white pine may indicate a limited capacity for nitrate phytoremediation by these species.

Comparative Transpiration Studies on the Invasive Eastern Redcedar (Juniperus virginiana L.) and Adjacent Woody Trees

Fire suppression and grazing on the Great Plains have resulted in alteration of the grassland ecosystem, including an increase in woody trees. Eastern redcedar ( Juniperus virginiana L.) is a native but invasive conifer that is rapidly expanding its range in Oklahoma due to human and ecological factors and the ability to tolerate aridity. It is known to reduce soil moisture due to high rates of water uptake compared to neighboring grasses and herbaceous species. The objectives of this study were to compare average amounts of water transpired between eastern redcedar and adjacent woody trees in central Oklahoma to determine how water loss in the conifer compares with other trees in the same locality. Average amounts of transpiration in eastern redcedar were compared with those of loblolly pine ( Pinus taeda L.) , white mulberry ( Morus alba L.) , eastern cottonwood ( Populus deltoides W. Bartram ex Marshall) and bur oak ( Quercus macrocarpa Michx.). Three to six branch tips per tree were securely bagged over 24-hour periods, and water collected in each bag was weighed and analyzed. Three to five sampling months spanning two or three seasons were conducted for each comparative study. Results indicated that for winter, spring, and fall, transpiration from eastern redcedar exceeded that from the other tree species. Weather variables such as day length and temperature were found to have strong to moderate effects on transpiration in eastern redcedar. Day length and temperature also had strong effects on transpiration in white mulberry and bur oak, respectively, and humidity had an effect on transpiration in loblolly pine. No reliable or significant effect of weather variables was detected in eastern cottonwood.

Species selection – A fundamental silvicultural tool to promote forest regeneration under high animal browsing pressure

Abstract Heavily disturbed post-mining sites are often difficult to restore to forestland due to chemical and physical soil limitations, as well as frequent animal herbivory of planted tree seedlings. Forest tree species differ in how they allocate resources to defensive compounds or growth in order to resist abiotic and biotic stresses after outplanting. However, the influences of plant nutrition and secondary metabolite production on browse susceptibility and recovery are not well understood within and among species, especially for temperate deciduous forest trees. We investigated foliar tannin and nutrient responses under fenced (to exclude white-tailed deer, Odocoileus virginianus) and non-fenced environments on an abandoned mine land in southwestern Indiana, USA. Using field fertilization (15N-9P-10K controlled-release fertilizer at 0, 30 g, and 60 g per seedling), we also created a gradient of nutrient availability for planted black cherry (Prunus serotina Ehrh.), bur oak (Quercus macrocarpa Michx.), northern red oak (Quercus rubra L.), and white oak (Quercus alba L.) seedlings. Fencing improved growth relative to non-fenced seedlings; fertilization improved growth for all species except northern red oak, but only when combined with fencing. Fertilization reduced foliar tannin concentrations for black cherry and white oak, but did not change browsing preference or browse recovery for any species. Without fencing, browsing selection was solely driven by tree species, whereby black cherry had a higher likelihood of being browsed compared to all oak species. This response was likely associated with differences among species in resource allocation patterns; black cherry prioritizes structural growth and recovery, while oaks allocate resources to both growth and secondary metabolite production. As fencing is often considered cost-prohibitive for mine reclamation and other restoration efforts, species selection is perhaps the most fundamental silvicultural tool to promote forest regeneration success under conditions of high animal browsing pressure.

Dasistoma macrophylla: Hemiparasite growth and impact onAcer saccharumandQuercus macrocarpa

Abstract Dasistoma macrophylla (Nutt.) Raf. is a photosynthetically competent hemiparasitic plant known to parasitize 21 different tree species. How different tree species vary in quality as hosts for this hemiparasite and how parasitism affects host growth have not been explored. We tested the hypothesis that D. macrophylla form more vascular connections, known as haustoria, to roots of the tree species that promotes greater growth of the hemiparasite in a greenhouse experiment. Juvenile Acer saccharum Marshall (sugar maple), a known host, and Quercus macrocarpa Michx. (bur oak), a previously untested species common to the locality, were grown alone or with one seedling of D. macrophylla derived from one of two populations. Additional D. macrophylla seedlings were grown alone. After 17 wk, dry shoot and root mass of the tree, dry shoot, and root mass of the hemiparasite, and the number of haustoria formed by the hemiparasite were determined. Dasistoma macrocarpa grew better with A. saccharum than it did ...

Annual rings of perennial forbs and mature oaks show similar effects of climate but inconsistent responses to fire in the North American prairie–forest ecotone

For the prairie–forest ecotone of central North America, research of the effects of climate and fire on the annual growth of nonwoody plant types is currently needed to compliment dendrochronological research used for predicting the stability of this ecotone in the future. Using cores of Quercus stellata Wangenh. and collars of taproots of Asclepias viridis Walter from central Oklahoma, as well as cores from Quercus macrocarpa Michx. and Lespedeza capitata Michx. collars in central Minnesota, we aimed to distinguish the response towards annual precipitation and temperature, as well as fire regime, between these co-existing plant types through patterns in annual ring growth. The effect of spring fire on the annual growth increment was only consistently significant for one of the forbs, with a positive relationship. The strong negative effect of summer temperature was consistent between forbs and Q. stellata, while the positive effect of either growing season precipitation was consistent between plant types. Furthermore, we found stronger patch-specific annual ring patterns in forbs in comparison with trees when patches are separated based on unique fire histories. Overall, such efforts could be used in further studies to better predict growth rates of dominant plant types in landscapes susceptible to significant environmental change.

Establishment success of trees planted in riparian buffer zones along an agricultural intensification gradient

Although riparian zones provide numerous ecological services, they have been widely degraded by agricultural intensification. To recover water quality and restore other critical services, tree planting has been implemented in agricultural riparian buffer zones worldwide. However, intensive agricultural practices adjacent to tree plantations are likely to impede their establishment. In this study, we assessed the survival and size of trees planted in riparian buffer zones along a gradient of agriculture intensification. We studied 68 riparian buffer zones in two agricultural watersheds of southeastern Québec (Canada) where trees had been planted 3⿿17 years prior to sampling. Tree survival and size (height, diameter and crown width) were measured and related to agricultural intensification, quantified as the frequency of annual crops in the agricultural field adjacent to riparian zones during the seven years prior to sampling. Tree survival decreased by 25% with increasing frequency of annual crops (P<0.0001; R2=35%), independently of the planting year. Aside from the influence of tree age, tree size varied with the frequency of annual crops but only for three of the six most frequently planted tree species (P=0.0007; R2=46%). These three species (Fraxinus pennsylvanica Marsh., Quercus macrocarpa Michx. and Picea glauca (Moench) Voss) showed reduced size with higher cultivation frequency of annual crops, whereas the other three species (Acer saccharum Marsh., Larix laricina (Du Roi) K. Koch and Quercus rubra L.) were more tolerant to agricultural intensification. While tree planting is carried out in riparian buffer zones to mitigate the environmental impacts of agricultural practices, agricultural intensification in turns impedes the establishment success of trees. To increase the environmental benefits provided by agroforestry projects, tree planting in riparian buffer zones should focus on species that tolerate agricultural intensive practices. Additionally, more frequent inclusion of hay meadows in the crop rotation of fields adjacent to riparian buffer zones may be beneficial to the establishment success of planted trees.

Drivers of radial growth and carbon isotope discrimination of bur oak (Quercus macrocarpa Michx.) across continental gradients in precipitation, vapour pressure deficit and irradiance

Tree-ring characteristics are commonly used to reconstruct climate variables, but divergence from the assumption of a single biophysical control may reduce the accuracy of these reconstructions. Here, we present data from bur oaks (Quercus macrocarpa Michx.) sampled within and beyond the current species bioclimatic envelope to identify the primary environmental controls on ring-width indices (RWIs) and carbon stable isotope discrimination (Δ(13) C) in tree-ring cellulose. Variation in Δ(13) C and RWI was more strongly related to leaf-to-air vapour pressure deficit (VPD) at the centre and western edge of the range compared with the northern and wettest regions. Among regions, Δ(13) C of tree-ring cellulose was closely predicted by VPD and light responses of canopy-level Δ(13) C estimated using a model driven by eddy flux and meteorological measurements (R(2) = 0.96, P = 0.003). RWI and Δ(13) C were positively correlated in the drier regions, while they were negatively correlated in the wettest region. The strength and direction of the correlations scaled with regional VPD or the ratio of precipitation to evapotranspiration. Therefore, the correlation strength between RWI and Δ(13) C may be used to infer past wetness or aridity from paleo wood by determining the degree to which carbon gain and growth have been more limited by moisture or light.

Forest dynamics at Minnesota's prairie-forest border driven by invasive buckthorn (Rhamnus cathartica) and native bur oak (Quercus macrocarpa)1

Wyckoff, P. H., R. Greiman, A. Krueger, and L. Luce. (Biology Discipline, University of Minnesota, Morris, MN 56267). Forest dynamics at Minnesota's prairie-forest border driven by invasive buckthorn (Rhamnus cathartica) and native bur oak (Quercus macrocarpa). J. Torrey Bot. Soc. 139: 311–322. 2012.—Quercus macrocarpa Michx. (bur oak) is the key pioneer species as forests establish at the prairie-forest ecotone in western Minnesota, but invasive Rhamnus cathartica L. (European buckthorn) is an abundant and increasing secondary tree. Here we contrast microsite utilization and growth as a function of light and soil moisture for Q. macrocarpa and R. cathartica saplings at an ecotonal forest in an effort to establish the roles these two species are likely to play in near-term forest dynamics. Compared to Q. macrocarpa, R. cathartica saplings are found, on average, in darker microsites (P < 0.001) with higher soil moisture (P < 0.001), though the range of light levels at which saplings were seen to occur is much larger for Q. macrocarpa than for R. cathartica. We fit a variety of models which predict sapling growth and compared fits using AICc. With our best fitting models, light, size, and soil moisture together explain approximately half of the variation in growth among R. cathartica saplings and two-thirds of the variation in Q. macrocarpa. Most similar studies utilize models that include an a priori assumption that growth will asymptote with increasing light availability, but we find no evidence to support the use of asymptotic models. All top ranked models include light and sapling size, but the calculated importance of both light and soil moisture is dependent on the choice of growth metric, a disturbing finding given the variety of metrics utilized in the sapling growth literature. For neither species does the addition of soil moisture significantly improve growth models if the growth metric used is absolute radial stem growth increment, but soil moisture becomes important when absolute basal area increment is the growth metric for Q. macrocarpa, and when relative growth increment is used for either species. Limited success of R. cathartica in light, dry microsites suggests that the invasive tree may be near its climatic limit at our ecotonal forest site. At the same time, the relative success of the species in the dark understory of our warm dry forest suggests that near-term warming, with an expected increase in continental-climate drought, is unlikely to limit R. cathartica across the bulk of forests it has invaded in North America.

Spring temperature responses of oaks are synchronous with North Atlantic conditions during the last deglaciation

Paleoclimate proxies based on the measurement of xylem cell anatomy have rarely been developed across the temperature range of a species or applied to wood predating the most recent millennium. Here we describe wood anatomy‐based proxies for spring temperatures in central North America from modern bur oaks (Quercus macrocarpa Michx.). The strong coherence of temperature signals across the species range supports the use of these proxies across thousands of years of climatic change. We also used 79 subfossil oak log cross sections from northern Missouri, 14C‐dated to 9.9–13.63 ka (ka is 1000 cal yr BP), to assess the frequency of oak deposition into alluvial sediments and a subset of these oaks for a wood anatomy‐based reconstruction of spring paleotemperatures. Temperatures during the Younger Dryas cold period (YD) were up to 3.5°C lower than modern temperatures for that region, equivalent to or lower than those experienced at the northern edge of the modern species range. Compared to extant oaks growing at much higher [CO2], subfossil oaks had greater vessel frequencies. Besides very low theoretical (or estimated) xylem conductivity near the beginning of the oak record near 13.6 ka, vessel frequencies greater than modern trees compensated for reduced vessel dimensions so that theoretical xylem conductivity was consistently above that of modern trees at the cold northern sites. Significant correlations were found between the frequency of 14C‐dated oaks and either δ18O from the NGRIP (North Greenland Ice Core Project) ice core or from the Cariaco grayscale marine‐sediment record from the southern Caribbean sea. Oak deposition into alluvial sediments during the YD was significantly lower than expected given the average sample depth of oaks from 9.9 to 13.6 ka. Reduced oak deposition during the YD suggests that an abrupt shift in climate reduced oak populations across the region and/or changed the rates of channel movement across drainages.

The association of two invasive shrubs, common buckthorn (Rhamnus cathartica) and Tartarian honeysuckle (Lonicera tatarica), with oak communities in the midwestern United States

Oak forests throughout North America are declining due to changes in disturbance regimes that have led to increased competition from other tree and shrub species. We evaluated associations between oak regeneration, the occurrence of two common invasive shrubs (common buckthorn ( Rhamnus cathartica L.) and Tartarian honeysuckle ( Lonicera tatarica L.)), and forest edges in oak forests in a portion of the midwestern United States where bur ( Quercus macrocarpa Michx.), red ( Quercus rubra L.), and white oak ( Quercus alba L.) were historically dominant. We found poor recruitment of oaks in comparison to other, more shade-tolerant tree species. Results further revealed a strong stand-scale association between bur oak, open canopy conditions, high soil nutrient levels, and the presence of common buckthorn and Tartarian honeysuckle; these same site characteristics were disassociated with red and white oak. Within red and white oak stands, however, the presence of the invasive shrubs was more pronounced near forest edges. While oak recruitment is hampered throughout stands, our research suggests that predominant constraints may vary based on soil and light gradients found along forest edges.

Diurnal and seasonal changes of leaf lamina hydraulic conductance in bur oak (Quercus macrocarpa) and trembling aspen (Populus tremuloides)

The aim of this study was to examine the diurnal and seasonal variations in the sensitivity of leaf lamina (Klam) hydraulic conductance to irradiance in bur oak (Quercus macrocarpa Michx.) and trembling aspen (Populus tremuloides Michx.), which vary in their responses of Klam to irradiance. Klam was determined using the high-pressure method and the measurements were carried out in June, August and September. The irradiance response of Klam in bur oak was present throughout the day and declined in senescing leaves. In trembling aspen, Klam declined from morning to late afternoon and drastically decreased before the onset of leaf senescence, but it was not sensitive to irradiance. In both tree species, the capacity of the petioles to supply water to leaf lamina changed during the day in accordance with the ability of the leaf lamina to transport water. Petiole hydraulic conductivity (Kpet) declined during the season in bur oak leaves, while it tended to increase in trembling aspen leaves. There was no correlation between the Klam values and air temperature or light intensity at the time of leaf collection. For trembling aspen, Kpet was negatively correlated with the air temperature suggesting sensitivity to drought. We conclude that the water transport properties of petioles and leaf lamina in the two studied tree species reflect their ecological adaptations. Trembling aspen leaves have high hydraulic conductivity and high stomatal conductance regardless of the irradiance level, consistent with the rapid growth and high demand for water. In contrast, the increased lamina hydraulic conductivity and stomatal conductance under high irradiance in bur oak trees reflect a water conservation strategy.

Notice of release of Ekalaka Germplasm bur oak selected class pre-varietal release

A Selected Class pre-varietal release of bur oak ( Quercus macrocarpa Michx. [Fagaceae]) designated as Ekalaka Germplasm bur oak has been released for use in the Northern Great Plains and Intermountain West for windbreaks, shelter-belts, riparian forest buffers, wildlife habitat plantings, Xeriscapes®, and other conservation plantings. This selection is a bulk of 9 indigenous seed sources from Montana, North Dakota, and South Dakota selected for superior percentage survival, rate of height growth, and vigor rating compared with other seed sources tested at Bridger, Montana. Ekalaka Germplasm bur oak can be used in many conservation applications in place of Russian-olive ( Elaeagnus angustifolia L. [Elaeagnaceae]) and green ash ( Fraxinus pennsylvanica Marsh. [Oleaceae]) given adequate soil aeration and low salinity.

Our current understanding of the Upper Mississippi River System floodplain forest

The silver maple-American elm floodplain forest spans throughout the floodplains of the Upper Mississippi River System (UMRS). These forests of the UMRS today are less diverse than those of pre-European expansion (ca. early 1800s). Scientists and land managers are concerned about loss of species diversity including mast species such as pin oak (Quercus palustris Muenchh.), swamp white oak (Quercus bicolor Willd.), bur oak (Quercus macrocarpa Michx. Q), pecan (Carya illinoinensis (Wangenh.) K. Koch), and other hickories. The Great Midwest Flood of 1993 maintained species diversity in the lower, unimpounded region of the Upper Mississippi River, providing an opportunity for eastern cottonwood and black willow to regenerate in this portion of the Mississippi River. However, throughout the entire region, floodplain forests of the Upper Mississippi River have become less diverse, and have become dominated by the flood-tolerant and shade-tolerant silver maple (Acer saccharinum L.). The imminent loss of green ash (Fraxinus pennsylvanica Marsh.) to the Emerald Ash Borer (Agrilus planipennis Fairmaire) follows an already changing forest structure due to a disease-related shift of American elm (Ulmus americana L.) from the overstory to the midstory strata. Another invasive, reed canary grass (Phalaris arundinaceae L.), interferes with evolved mechanisms for establishment as it outcompetes trees of the early successional floodplain forest. Further research is needed to create and maintain diverse floodplain forest communities that have been lost under current conditions. Returning flood-prone agricultural lands within the floodplain to the floodplain forest will improve the health and connectivity of the river system, increase the diversity of habitats, and provide flood relief for communities of the Upper Mississippi River.

Cutting Back Stock Plants Promotes Adventitious Rooting of Stems of Quercus bicolor and Quercus macrocarpa

Abstract Studies were conducted to investigate the severity of cutting back stock plants on adventitious rooting of layered stems and stem cuttings of Quercus bicolor Willd. (swamp white oak) and Quercus macrocarpa Michx. (bur oak). Rooting averaged 77% in Q. bicolor and 70% in Q. macrocarpa layered stems from the cutback stock plant group, compared to air layered stems from intact plants which averaged 1% in Q. bicolor and 0% in Q. macrocarpa. In another experiment cuttings were taken from three stock plant heights [4 cm (1.6 in), or 100 cm (39.4 in) stumps and intact plants ∼ 170 cm (66.9 in)] which were either etiolated or grown in natural light and rooted under mist. The best rooting (59%) and average number of roots (9.3) were found in etiolated Q. bicolor cuttings taken from 4 cm (1.6 in) stumps. Q. macrocarpa cuttings rooted poorly with only 7% of the cuttings rooting. By taking cuttings a week earlier for rooting (2 weeks, at the softwood stage), rooting in Q. macrocarpa was possible, with the best rooting (46%) found in etiolated cuttings taken from 4 cm (1.6 in) stumps. Overall, the highest rooting and greatest number of roots occurred in etiolated layers and cuttings from the 4 cm cutback group. Rooting generally increased with increasing extent of stock plant cutback

Aquaporin gene expression and apoplastic water flow in bur oak (Quercus macrocarpa) leaves in relation to the light response of leaf hydraulic conductance.

It has previously been shown that hydraulic conductance in bur oak leaves (Quercus macrocarpa Michx.), measured with the high pressure flow meter technique (HPFM), can significantly increase within 30 min following exposure to high irradiance. The present study investigated whether this increase could be explained by an increase in the cell-to-cell pathway and whether the response is linked to changes in the transcript level corresponding to aquaporin genes. Four cDNA sequences showing high similarity to members of the aquaporin gene family from other plant species were characterized from bur oak leaves and the expression levels of these cDNA sequences were examined in leaves by quantitative real-time PCR (QRT-PCR). No change was found in the relative transcript abundance corresponding to these four putative aquaporin genes in leaves with light-induced high hydraulic conductance (exposed to high irradiance) compared to leaves with low hydraulic conductance (exposed to low irradiance). However, in sun leaves that were exposed to different light levels prior to leaf collection (full sunlight, shade, and covered with aluminium foil for 16 h), the relative transcript levels of two of the putative aquaporin genes increased several-fold in shaded leaves compared to the sun-exposed or covered leaves. When the leaves were pressure-infiltrated with the apoplastic tracer dye trisodium 3-hydroxy-5,8,10-pyrenetrisulphonate (PTS3, 0.02%), there was no change in the PTS3 concentration of leaf exudates collected in ambient light or in high irradiance, but there was a small apoplastic acidification. There was also no change in PTS3 concentration between the leaves infiltrated under high irradiance with 0.02% PTS3 or with 0.1 mM HgCl2 in 0.02% PTS3. The results suggest that the putative aquaporin genes that were identified in the present study probably do not play a role in the light responses of hydraulic conductance at the transcript level, but they may function in regulating water homeostasis in leaves adapted to different light conditions. In addition, it is shown that high irradiance induced changes in the pH of the apoplast and that there does not appear to be a significant shift to the cell-to-cell mediated water transport in bur oak leaves exposed to high irradiance as measured by the apoplastic tracer dye.