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1,436 results for “Oaks”
Ungulate-Forest Interactions in Partially Harvested Oak-Pine Stands in Central Massachusetts 2009
Ungulates are attracted to forest openings created by natural disturbance and timber harvesting due to the abundance of high quality browse in these openings. Despite the increased activity and browsing of ungulates in forest openings, the importance of browsing relative to abiotic factors such as light on forest regeneration is often unclear. In southern New England, medium-intensity harvesting is the predominant forest disturbance attracting white-tailed deer and moose. Oaks are the foundation hardwood taxon and predominant timber tree in the region and are in decline. Hence, the effects of ungulate browsing on oak forests are of great interest to ecologists, conservationists and forest and wildlife managers. We sampled tree regeneration and ungulate foraging activity across a range of canopy disturbances (35-90% basal area removed) in 34 stands of the Quabbin and Ware River Watershed Forests. Browsing was very high across the plots with about 80% of red maple and oak stems browsed. Taller stems were generally browsed more frequently than shorter stems. Oak regeneration in the smaller size classes was generally lower in stands with higher percent cover of hay-scented fern. The proportion of browsed red maples and oaks generally increased with increasing density of these taxa. Despite intensive herbivory, oaks appear to be regenerating well with increased light in these partially harvested stands.
Sap Flow of Northern Red Oak Trees Under Ecosystem Warming at Harvard Forest 2011
Over the next century, air temperature increases up to 5 °C are projected for the northeastern USA. Because evapotranspiration dominates water loss from terrestrial ecosystems, tree ecophysiological response to warming will have important consequences for forest water budgets. We measured growing season sap flow rates in mature northern red oak (Quercus rubra L.) trees in a combined air (up to 5.5 °C above ambient) and soil (up to 1.85 °C above ambient at 6-cm depth) warming experiment at Harvard Forest, MA, USA. Principal components analysis found air and soil temperatures had the largest effects on sap flow. On average, each 1 °C increase in temperature increased sap flow rates by approximately 1100 kg H2O m-2 sapwood area day-1 throughout the growing season and by 1200 kg H2O m-2 sapwood area day-1 during the early growing season. Reductions in the number of cold winter days correlated positively with increased sap flow at night during the early growing season (a decrease of 100 heating-degree-days was associated with a sapflow increase of approximately 5 kg H2O m-2 sapwood area day-1). Soil moisture declined with increased treatment temperatures, and each soil moisture percentage increase resulted in an increase in sap flow of approximately 360 kg H2O m-2 sapwood area day-1. At night, soil moisture correlated positively with sap flow rate. These results demonstrate that warmer air and soil temperatures in winter and throughout the growing season lead to increased sap flow rates, which could affect forest water budgets throughout the year.
Root Exudation Simulation Experiment in a Red Oak Stand at Harvard Forest 2011
Root exudation is thought to increase the activity of microbes and the exoenzymes they synthesize, leading to accelerated rates of carbon (C) mineralization and nutrient cycling in rhizosphere soils relative to bulk soils. The nitrogen (N) content of microbial biomass and exoenzymes may introduce a stoichiometric constraint on the ability of microbes to effectively utilize the root exudates, particularly if the exudates are rich in C but low in N. We combined a theoretical model of microbial activity with an exudation experiment to test the hypothesis that the ability of soil microbes to utilize root exudates for the synthesis of additional biomass and exoenzymes is constrained by N availability. The field experiment simulated exudation by automatically pumping solutions of chemicals often found in root exudates (“exudate mimics”) containing C alone or C in combination with N (C:N ratio of 10) through microlysimeter “root simulators” into intact forest soils in two 50-day experiments. The delivery of C-only exudate mimics increased microbial respiration but had no effect on microbial biomass or exoenzyme activities. By contrast, experimental delivery of exudate mimics containing both C and N significantly increased microbial respiration, microbial biomass, and the activity of exoenzymes that decompose low molecular weight components of soil organic matter (SOM, e.g., cellulose, amino sugars), while decreasing the activity of exoenzymes that degrade high molecular weight SOM (e.g., polyphenols, lignin). The modeling results were consistent with the experiments; simulated delivery of C-only exudates induced microbial N-limitation, which constrained the synthesis of microbial biomass and exoenzymes. Exuding N as well as C alleviated this stoichiometric constraint in the model, allowing for increased exoenzyme production, the priming of decomposition, and a net release of N from SOM (i.e., mineralization). The quantity of N released from SOM in the model simulations was
Ectomycorrhizal Community of Red Oak at Harvard Forest 2013
There is evidence that ectomycorrhizal Pezizales prevail on roots at woodland edges or habitats where trees are well spaced, and where there is minimal understory vegetation, soil pH is relatively high, and bare soil is a feature. This observation was repeated in a recent study of mitospores produced by these fungi, where they were found most often at woodland edges, road sides, the middle of paths, and lawns. A key feature that distinguishes Basidiomycota from Ascomycota is that the dikaryon necessary for sexual reproduction is generally formed early after spore germination in the former, but not until fruitbody formation in the latter. Our hypothesis is that the mitospores produced by ectomycorrhizal Pezizales act as spermatia, and that these spores are more effectively produced and dispersed from bare soil than from areas with a thick organic layer. Here we tested our hypothesis by comparing the community of ectomycorrhizal root fungi on red oak trees in Harvard Forest and the Arnold Arboretum.
Sap Flow in Red Maple and Red Oak in the Harvard Forest Snow Removal Study 2011
The climate is changing in mid and high latitude environments with the depth and duration of snowpack shrinking for many temperate forest ecosystems. A reduced snowpack and increased depth and duration of soil frost can injure fine roots, which are essential for plant water uptake. Water uptake is a crucial component of ecosystem functioning because this process strongly impacts other biological processes, such as primary productivity and nutrient uptake. We evaluated the effects of changing winter climate, including snow and soil frost dynamics, on rates of water uptake (i.e. sap flow) in a snow manipulation study at Harvard Forest. We had three reference and tree plots from which we removed snow and induced soil freezing.
Coarse Roots and Rock Content in Oak, Hemlock, and Ash Stands at Harvard Forest 2020
When collecting soil samples in the very rocky soils of the Harvard Forest, researchers are forced to core the soil away from rocks. Thus, the resulting samples tend to underestimate the rock content of the soil and overestimate the sand, silt, and other fine particles content. When scaling the results to a spatial area larger than the sample’s (e.g., m2, hectare) it is important to know the actual rock content of the soil to apply the right correction factor. Therefore, we dug pits in three different stands at the Harvard Forest to determine the rock content. At the same time we also collected coarse roots (>2mm diameter) to measure their biomass, which can’t be easily done using the usual soil coring techniques.
Nonstructural Carbohydrates in Defoliated Oaks in Central Massachusetts 2019-2020
Carbon starvation posits that defoliation- and drought-induced mortality results from drawing down stored nonstructural carbohydrates (NSCs), but evidence is mixed and mortality is often observed prior to full drawdown of NSCs. We tested the relationship between defoliation severity, NSC drawdown, and tree mortality by measuring NSCs in mature oak trees defoliated by Lymantria dispar across a natural experimental gradient of defoliation severity. We collected stem and root samples from oaks (Quercus rubra and Q. alba) in interior forests (n=34) and forest edges (n=47) in central Massachusetts, USA. Total NSC (TNC; sugar + starch) stores were analyzed with respect to tree size, species, and defoliation severity, which ranged between 5 and 100%. Forest edge trees had higher TNC stores that were less sensitive to defoliation than interior forest trees. However, TNC stores declined significantly in both groups with increasingly severe defoliation. Furthermore, we observed a mortality threshold of 1.5% dry weight TNC. Our study draws a direct link between insect defoliation and TNC reserves and defines a TNC threshold below which mortality is highly likely. These findings advance understanding and improve model parametrization of tree response to insect outbreaks, an increasing threat with globalization and climate change.
Oak Forest Response to Lymantria dispar Defoliation in Central Massachusetts since 2019
Invasive forest insects are a major global change driver, and the Northeastern U.S. is an invasion hotspot. Lymantria dispar is one of the region’s most destructive defoliators. After thirty years of quiescence, a surprisingly severe outbreak began in 2015 in southern New England, and by 2018 had caused dramatic oak mortality across thousands of forested acres. Lymantria dispar is considered a generalist, but in New England, oaks (Quercus sp.) are its preferred host trees. Oaks are key overstory trees in eastern North America. In New England, they have been a dominant component of the forest for thousands of years, and play a leading role in providing habitat, timber, and carbon sequestration. However, oak prominence is declining throughout New England. The reasons for oak’s decreasing abundance are the subject of lively debate but the role of L. dispar is likely underappreciated. Therefore, we need to understand the causes and consequences of oak dieback and mortality to this disturbance event, so that we can better predict responses to future outbreaks. To address this need, we established a set of permanent plots in central Massachusetts, chosen to capture a range of defoliation severity.
Long-Term Dynamics of Oak and Chestnut in Central Massachusetts from 3500 BP to Present
Despite decades of study we have limited insights into the nature of the pre-European landscape of the northeastern USA and the forces and changes that shaped modern forest patterns. Information on such long-term forest dynamics would provide critical insights into the relationships among environmental change, land-use history and biotic responses and is greatly needed for conservation planning. To address these issues we used modern, historical, and paleoecological approaches to reconstruct the 3500-year history of a New England upland region dominated by oak and (formerly) chestnut forests and to interpret the interactions among climate change, natural and human disturbance, and site factors in controlling vegetation patterns and dynamics at different spatial scales. The results indicate that stand, landscape and regional forest dynamics were most strongly driven by climate, notably an apparent cooling and increase in moisture availability c. 1500 yr BP, and European land-use activities commencing 260 yr BP. However, the abundance of oak and chestnut (fire-tolerant, sprouting species) and the distribution of hemlock (fire-intolerant) at a stand to landscape scale were also influenced by fire, which, in turn, varied with climate and human activity. Despite, or perhaps as a consequence of ongoing disturbance by fire and presumably windstorms in this hurricane-prone region, the pre-European period was marked by two 1000+ year periods of remarkably stable forest composition, separated by an abrupt compositional shift. In contrast, over the past 260 years the vegetation has changed rather continuously in response to human activity, producing stand, landscape and regional patterns that are novel as well as recent in origin. Chestnut was a major component of some pre-European landscapes in New England, in part because of occasional fire, and that cultural and physical factors have interacted over millennia to control vegetation patterns and dynamics. Our analyses also su
Dataset on tree diversity metrics and aboveground carbon storage in Southeastern U.S. oak-pine forests, 2009–2019
This dataset contains measurements of tree structural and taxonomic diversity, stand attributes, and aboveground carbon storage from mixed oak-pine forests in Florida, Georgia, and Alabama, located in the southeastern United States. Data were collected from 946 mixed oak-pine, and 7224 longleaf-slash pine and oak-pine Forest Inventory and Analysis (FIA) plots respectively spanning the years 2009 to 2019. Variables include aboveground carbon, aboveground biomass, tree density, basal area, stand age, and diversity metrics such as Shannon indices for tree species and diameter-based structural classes. Functional diversity metrics—including functional dominance and functional divergence—are also included. These data were used to support a published study examining the interactive effects of diversity metrics on carbon storage using structural equation modeling. The geographic coverage represents humid subtropical forest regions of the southeastern U.S.
Northern red oak regeneration in burned and unburned stands in the White Mountain National Forest, New Hampshire, USA, 2023-2024
This project aimed to determine whether prescribed burning of managed forest stands improves the regeneration of Quercus rubra near its northern range limit in New Hampshire. We measured oak seedling density and growth rates in three pairs of managed stands in which one had received a prescribed burn since 2017. We also measured the density of competing seedlings and shrubs, leaf area index above seedling height, soil nutrients, mycorrhizal colonization, foliar carbon/nitrogen ratio, and stable isotopes of nitrogen and carbon. We found greater oak seedling density and faster oak seedling growth rates in burned stands relative to unburned stands. A subset of these measurements were also collected in additional burned and unburned study stands in the region. A companion mesocosm experiment showed faster growth in oak seedlings grown in soil from burned vs. unburned stands. Together these studies show that the benefits of fire to oak regeneration are mediated both via greater light availability as well as effects mediated via soil.
Tree Mast Production in Pinyon-Juniper-Oak Forests at the Sevilleta National Wildlife Refuge, New Mexico
The purpose of this study is to monitor the fruit production of three common woody tree species that occur on the Sevilleta National Wildlife Refuge (NWR) in New Mexico. We estimate fruit production of two monoecious species, Pinus edulis (pinon pine) and Quercus turbinella (Sonoran scrub oak) and one dioecious species, Juniperus monosperma (one-seed juniper). During August – November, we estimate fruit production for these three species at up to six sites within the Sevilleta NWR. Different protocols are used for each species (see Methods). In addition, the age and/or size of each individual tree was assessed at the beginning of the study, excepting in one site (WM) where fruit counts occurred at the plot, rather than individual tree, scale. For P. edulis and J. monosperma, trees wre binned into categories of young, medium, old, or very old trees. For Q. turbinella, we estimate canopy surface area in m 2
Percent cover of under- and mid-story vegetation and seedling counts in the Future of Oak Forests project at Black Rock Forest, Cornwall, NY.
Black Rock Forest established a series of 12, 0.56 ha plots in 2005 to assess impacts of the loss of tree in the genus Quercus on the forest ecosystem (entitled the Future of Oak Forests experiment). Three trunk girdling treatments, with control plots were instituted in 2008. Each plot also contained an ~10m by ~15m deer exclosure to assess the impact of herbivory post-disturbance. In 2006 and 2008, before exclosures were erected, pre-treatment surveys were conducted in all unexclosed (n=120) quadrats. Surveys of all 240 understory quadrats were conducted annually in late summer (August to September) from 2009 to 2018 and then again in 2021. At each quadrat, trained observers identified all vascular plants to species and assigned each species a percent cover value. The percent cover of moss was also recorded but moss species were not identified. Counts of tree seedlings and some woody shrubs were also recorded in addition to percent cover values. Seedlings were considered saplings, and therefore not counted, once they reached 1.3 m tall (breast height).
Oak litter decomposition parameters across 19 Nutrient Network grassland sites in response to NPK and herbivore exclusion treatments
These data are from a study examining how herbivory and nutrient supply affect long-term aboveground decomposition. A novel oak litter was decomposed across 19 grassland sites of the Nutrient Network distributed experiment. At each site, a full-factorial experiment of combined nitrogen, phosphorus, and potassium plus micronutrients ('control' or 'NPK') and mammalian herbivore exclusion ('fencing') was carried out in a randomized block design. The duration of the decomposition experiment varied by site but litter bags were harvested at approximately annual intervals for up to seven years. Litter decay parameters were calculated using four alternative statistical models of litter decomposition. Covariate data describing site and plot-level abiotic and biotic characteristics were also measured, including climate, atmospheric nitrogen deposition, live and dead aboveground biomass, and percent cover.
Red Oak Root and Soil Environmental Gradient Study, Midwest U.S., 2022-2023.
Fine root trait and soils data for Quercus rubra L. (northern red oak) sampled along a Midwestern latitudinal gradient. Fourteen sites spanning 5-14 degrees C were sampled. Each sample represents 2 6 cm deep x 5 cm wide soil cores obtained from near the base of a Q. rubra individuals, with 6 sampled plots per site. Plots were located approximately 40 m apart along a linear transect to be at a cluster of Q. rubra individuals. All 14 sites were visited twice in the growing season of 2022: between June 1st and June 21st, and between July 5th and July 21st. Root traits sampled include average diameter, root tissue density, specific root length, branching intensity, and specific respiration rate. A 1 mm diameter limit cut-off was used. These traits were measured in the field (respiration rates) or from output from RhizoVision Explorer image analysis. Traits are associated with the smaller fine root sample used for respiration measurement in the field (~2 g dry weight). Fine root biomass was also obtained by removing all remaining fine roots in the core, drying, and weighing, and then was multiplied by weight-normalized respiration rates to obtain estimates of fine root ecosystem respiration. This data package is complete, but will be associated with data from 4 sites revisited in 2023 to obtain repeat fine root trait measurements and fungal community community metrics.
Hubbard Brook Experimental Forest: Oak seedling demography, 2011 - ongoing
This data set was built from a larger data set of marked northern red oak seedlings surveyed from 2011-2023. In this data set, only seedlings marked in their year of germination with full environmental and seedlings measures were kept (N = 937). The data set was built for an accelerated failure time model of seedling survival that found year of germination, seedling density, shrub cover and elevation to have the largest effect on survival time. The status of the seedling acorn (attached or missing) was also important. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.
Carbon and water fluxes in a cork oak woodland in Central Portugal
<p>The Data set contains eddy covariance measurements of carbon and water fluxes and ancillary measurements observed at a cork oak woodland (<em>Quercus suber </em>L.) in central Portugal. The climate is Mediterranean, with mild, wet winters and hot, dry summers.</p> <p>Data are available in the file data.csv (UTF-8 encoding), the description of the variables and units are available in the file meta.csv (UTF-8 encoding).</p> <p>Further description of the site, methods and data processing can be viewed in the files metadata.pdf and metadata.csv</p> <p> </p>
Bird Communities in Fragmented, Non-Native Pine Plantations in the Oak Openings Region of Northwest Ohio
Comprehensive surveys, while preferred, are not always feasible due to time, logistical, and funding constraints. However, limited surveys of focal taxa, such as birds, coupled with vegetation surveys, can provide critical information to guide land management. In the 1930s non-native conifers were planted in the Oak Openings Region of northwestern Ohio, a biodiversity hotspot. The stands are declining, and management is needed, but restoration to native habitat is time consuming and expensive. Our research utilized an avian perspective of ecological function of introduced pine plantations versus native remnants to guide management. We surveyed bird activity May through July 2020 with point-counts in nine sites (1.3-2.3 ha) with three each of white pine, red pine, and oak forest sites. At each site, we estimated bird richness, abundance, and diversity, as well as structural characteristics (e.g., canopy cover), composition (e.g., vegetation types), and landscape context (e.g., landcover). Superficially, the pine sites appear to be beneficial as pine habitat for breeding birds, with high Simpson’s indices (up to 0.89) and high species richness compared to oak sites. However, our results reveal that the pines are not truly functioning as pine habitat for birds based on the limited occurrence of pine specialist species, proportion of generalists to pine specialists, and landscape context. Simple measures of diversity with no consideration as to species identity and without the environmental context fail to provide reliable measures of ecological value. Instead, we recommend selective sampling and consideration of landscape context, vegetation structure, and species classification to guide management.
Factors Influencing Aboveground Carbon Storage in Mixed Oak-Pine Forests: USDA FIA Data from Southeastern U.S. (2009-2019)
This study explores factors affecting aboveground carbon (AGC) storage in mixed oak-pine forests across the Southeastern United States. Utilizing USDA Forest Inventory and Analysis (FIA) data from 2009 to 2019, the research spans nine states: Alabama, Mississippi, Florida, Georgia, North Carolina, South Carolina, Texas, Louisiana, and Virginia. Data processing in R included converting units to the metric system and calculating structural diversity using Shannon diversity indices. Climate data from the PRISM Climate Group were integrated with FIA data using longitude and latitude. The research aims to uncover how various factors influence AGC storage and contribute to informed forest management practices.
Stream nitrate concentrations and discharge, stream nitrate uptake, and results of stream network nitrate model to determine lateral nitrate load from land to stream in Oak Creek, Arizona, USA
Data package associated with Handler et al. (2024) "Nitrate loads from land to stream are balanced by in-stream nitrate uptake across season in a dryland stream". The study describes the nitrate dynamics in Oak Creek watershed. Data include measurements from four seasonal synoptic sampling campaigns, nine seasonal stream nitrate uptake experiments on the main stem and tributaries, and the results of a network model that estimates the lateral load of nitrate from surrounding landscape to the stream network as well as network-level stream nitrate uptake and retention.
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