SE US Research Articles

Impact of Heatwaves and Declining NOx on Nocturnal Monoterpene Oxidation in the Urban Southeastern United States.

Nighttime oxidation of monoterpenes (MT) via the nitrate radical (NO3) and ozone (O3) contributes to the formation of secondary organic aerosol (SOA). This study uses observations in Atlanta, Georgia from 2011-2022 to quantify trends in nighttime production of NO3 (PNO3) and O3 concentrations and compare to model outputs from the EPA's Air QUAlity TimE Series Project (EQUATES). We present urban-suburban gradients in nighttime NO3 and O3 concentrations and quantify their fractional importance (F) for MT oxidation. Both observations and EQUATES show a decline in PNO3, with modeled PNO3 declining faster than observations. Despite decreasing PNO3, we find that NO3 continues to dominate nocturnal boundary layer (NBL) MT oxidation (FNO3 = 60%) in 2017, 2021, and 2022, which is consistent with EQUATES (FNO3 = 80%) from 2013-2019. This contrasts an anticipated decline in FNO3 based on prior observations in the nighttime residual layer, where O3 is the dominant oxidant. Using two case studies of heatwaves in summer 2022, we show that extreme heat events can increase NO3 concentrations and FNO3, leading to short MT lifetimes (<1 h) and high gas-phase organic nitrate production. Regardless of the presence of heatwaves, our findings suggest sustained organic nitrate aerosol formation in the urban SE US under declining NOx emissions, and highlight the need for improved representation of extreme heat events in chemistry-transport models and additional observations along urban to rural gradients.

Holocene hydroclimate stability in three lake sediment records from the southeastern United States

Many Holocene paleoclimate records from the southeastern United States (SE US) have limited chronological constraints and/or low sedimentation rates and consequently low resolution; this presents challenges in discerning the relative importance of synoptic–scale drivers of past hydroclimate. In this study we summarize three lake sediment records that are uniquely located to test hypotheses regarding the importance of the Pacific North American (PNA) pattern and the North Atlantic Oscillation (NAO) over the last 5000 years. At Pigeon Marsh, Buck Pond, and Halls Pond, we used sedimentological (radiocarbon dating of transect cores), physical (grain size), geochemical (carbon and nitrogen ratios and isotopes), and biological (palynomorphs) proxies to reconstruct lake level and lake environment. Moderate lake and environmental changes occur around 2000 cal yr BP at Buck and Halls Pond, which is regionally consistent with other paleorecords and may suggest that the NAO was an important control. However, our results generally indicate fairly stable hydroclimate conditions up until historical European settlement when land clearance caused vegetational and lake hydrologic balance changes that were unprecedented in both magnitude and rate compared to the middle/late Holocene.

Carinata, the Sustainable Crop for a Bio-based Economy: Production Recommendations for the Southeastern United States

Brassica carinata is a non-food industrial oilseed crop that can be grown in the winter in the southeast US without impacting food, feed, or fiber crops. Carinata is a low carbon advanced renewable fuel feedstock and a good source of animal protein. Carinata research in the SE US through a public-private partnership has developed a comprehensive body of knowledge regarding carinata agronomics, life cycle analysis, best management practices and economics. This article aims to help growers and others interested in carinata to understand its biology, agronomy, and production aspects.

Double-cropping effects of Brassica carinata and summer crops: II. Effects of winter cropping history on subsequent summer crop production

There is an opportunity for crop farmers in the Southeast United States (SE US) to increase income by producing carinata during the winter following summer crop production. However, a major limitation to the use of carinata as a winter annual in the SE US is the lack of information on double-cropping with summer commodity crops common to the region. Considering that integrating carinata into cropping systems common to the region could impact productivity of those systems, it is critical to quantify the potential effects of carinata on existing cropping systems. To this end, a study was conducted in Jay, Florida for three years to evaluate the effects of winter cropping history (carinata vs. fallow) on the productivity of subsequent summer crops including cotton, peanut, sorghum, and soybean. Treatments (winter carinata vs. winter fallow) were laid out in a randomized complete block design with eight replications. Data were collected on infiltration; plant population; plant canopy height; aboveground biomass; and yield. Infiltration rates, determined within a week of carinata harvest, were affected by winter cropping history, being greater in former carinata plots than former fallow plots. Carinata harvest coincided with the timely planting of cotton and peanut which resulted in these summer crops being sown three to four weeks later than their typical sowing window for the SE US. Winter cropping history (including the winter fallow control) did not influence commodity crop (cotton, peanut, sorghum, and soybean) yields when all summer crops were planted at the same time, as in a double-crop scenario. Regarding the combined productivity of winter (carinata vs. winter fallow) and summer crops, carinata-cotton, carinata-peanut, carinata-sorghum, and carinata-soybean systems were necessarily more productive than their winter fallow counterparts due to no crop production in the fallow during the winter cropping years. Overall, results from this study showed that carinata can successfully replace winter fallow, and can be double-cropped with summer-planted sorghum and soybean with no adverse effect on yield. Double-cropping carinata caused a delay in timely planting of cotton and peanut, and represents a limitation that may hinder its adoption in the SE US until such time a faster-maturing carinata cultivar can be developed.

Double-cropping effects of Brassica carinata and summer crops: I. Effects of summer cropping history on carinata production

Row croppers in the Southeast United States (SE US) are interested in diversifying their cropping systems and increasing revenue by growing a winter cash crop between summer crops, especially cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.). Double-cropping carinata (Brassica carinata A. Braun) between summer crops has potential to boost grower revenue and increase land use efficiency in the region. Given that this winter crop is fairly new in the SE US, its successful establishment in the region depends on its rotational fit into current cropping systems. Since incorporating carinata into the existing cropping systems in the region could influence the productivity of those systems, it is crucial to determine what changes row croppers should expect. To resolve this, research was conducted to quantify the effects of summer cropping history on the performance of carinata as part of diversified crop rotations in the SE US. A randomized complete block design with eight replications was implemented in Jay, Florida, over three years. Summer cropping history treatments were peanut, cotton, and summer fallow. Data was collected on carinata aboveground biomass and stover [including carbon (C) and nitrogen (N)]; yield (including yield components); and seed chemical composition (glucosinolates concentration, protein and oil contents, and oil composition). Carinata biomass, biomass C and N, stover residue, stover residue C and N, and stover residue C:N ratio were not affected by summer cropping history across years. Likewise, yield and seed chemical composition were not affected by summer cropping history. In terms of combined productivity of summer crops and carinata, cotton-carinata was the most productive system while fallow-carinata was the least productive. Overall, results from this study show that the insensitivity of carinata yield or seed quality to previous summer crops allows for flexibility in integrating carinata into existing rotations in the SE US. This simplifies the agronomic management of carinata as a biofuel crop since growers can concentrate on meeting yield goals without the risk of affecting yield or seed quality with different summer cropping histories.

Source appointment of volatile organic compounds and evaluation of anthropogenic monoterpene emission estimates in Atlanta, Georgia

Emissions of monoterpenes from volatile chemical products (VCPs) have been shown to contribute substantially to secondary organic aerosol (SOA) formation in a number of cities across the US. In the southeast US (SE US), monoterpenes are the dominant precursor to SOA production. Previous studies have assumed that monoterpenes are primarily biogenic in origin. We examine that assumption here using a total of nine months of volatile organic compound (VOC) observations spanning across 2020 and 2021 which are made via proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) in Atlanta, Georgia. The dataset is resolved via non-negative matrix factorization (NNMF) into two biogenic, four anthropogenic, and two secondary factors. NNMF results show that VCP sources contribute to 0.28 ± 0.17 ppb of monoterpenes, or about 26% of all monoterpenes in the summer and 53% in the winter. Interannual comparison suggest minimum impact of the COVID-19 pandemic on atmospheric VOC composition in Atlanta during the second half of 2020. Comparison of NNMF anthropogenic monoterpenes-to-benzene ([Manthro/B]) and anthropogenic-to-total monoterpenes ([Manthro/MT]) ratios with emission ratios in the National Emission Inventory 2016v1 modeling platform (NEI16) and Fuel-Based Inventory of Vehicle Emissions and Volatile Chemical Products (FIVE-VCP) suggests that NEI16 underestimates anthropogenic monoterpene emissions by as much as 70% in Atlanta. FIVE-VCP estimates higher anthropogenic monoterpene emissions than NEI16 and provides better agreement with observations, especially during winter months. Anthropogenic monoterpenes may impact as much as 17% of total summertime SOA formation in Atlanta and the SE US, with potential additional influence of limonene from anthropogenic monoterpene sources due to its higher reactivity and SOA yield potential.

Southeastern United States Hydroclimate During Holocene Abrupt Climate Events: Evidence From New Stalagmite Isotopic Records From Alabama

AbstractWe present new high‐resolution absolute‐dated stalagmite δ18O and δ13C records from Alabama, southeastern United States (SE US), spanning the last 12 thousand years (ka). A local relationship between annual rainfall amount and its amount‐weighed δ18O composition exists on interannual timescales, driven mostly by an amount effect during summer and spring seasons. Based on a novel quantitative interpretation of modern rainfall isotopic data, stalagmite δ18O variability is interpreted to reflect the relative contribution of summer and spring precipitation combined, relative to combined fall and winter precipitation. Precipitation amount in the SE US increases during an interval of 500 yr coeval with the Younger Dryas and during the 8.2 ka and Little Ice Age abrupt cooling events. High precipitation during these events reflects enhancement of spring and summer precipitation by 90% combined, relative to today's conditions, while the contribution of fall and winter rainfall remained unchanged or decreased slightly. Results from this study support model simulation results that suggest increased precipitation in the SE US during Atlantic Meridional Overturning Circulation (AMOC) slowdown/shutdown. In association with Northern Hemisphere mid‐latitude cooling from the Early to mid‐Holocene, annual precipitation in the SE US decreases, a pattern distinctive from that observed during abrupt cooling events related to AMOC shifts. Long‐term hydroclimate change in the SE US is likely sensitive to summer insolation reduction as inferred to have occurred in other tropical and subtropical regions. The dynamical link between AMOC shutdown and precipitation variability in the SE US remains to be examined.

The carbon footprint of beef cattle systems in the Southeast United States

Grasslands in the Southeast United States (SE US) cover 15.8 million ha and most of this area is dedicated to beef production systems. This region holds 6.3 million beef cows and 12.1 million cattle, including calves. Beef cattle systems in the SE US are mostly cow-calf based, and most of the greenhouse gas emission from cattle occurs during this phase (cow-calf) because of their forage-based diet. This review assessed the carbon footprint (C footprint) of beef cattle systems in the SE US and indicates possible ways to reduce it. Major emissions in beef cattle systems come from livestock enteric fermentation and greenhouse gases from excreta. Cow-calf systems in the SE US are typically low input, although they use some industrial fertilizers, machinery, and fossil fuel, which adds to the C footprint of the sector. There are opportunities to reduce the beef C footprint in the SE US by adopting climate-smart practices, including preservation of natural ecosystems that have potentially high carbon sequestration, afforestation, integration of forage legumes (and reduction of nitrogen fertilizer), use of slow-release fertilizers, and dietary interventions. In fact, depending on the level of adoption of some of these practices, it is possible to establish climate-neutral beef at the farm gate in the SE US. Beef is a key food for humans and has large economic effects. Development of climate-smart beef could create opportunities for a niche market that recognizes the environmental footprint of agricultural production and could incentivize producers to pursue those systems.

Challenges and opportunities for sustaining coastal wetlands and oyster reefs in the southeastern United States

Formed at the confluence of marine and fresh waters, estuaries experience both the seaside pressures of rising sea levels and increasing storm severity, and watershed and precipitation changes that are shifting the quality and quantity of freshwater and sediments delivered from upstream sources. Boating, shoreline hardening, harvesting pressure, and other signatures of human activity are also increasing as populations swell in coastal regions. Given this shifting landscape of pressures, the factors most threatening to estuary health and stability are often uncertain. To identify the greatest contemporary threats to coastal wetlands and oyster reefs across the southeastern United States (Mississippi to North Carolina), we summarized recent population growth and land-cover change and surveyed estuarine management and science experts. From 1996 to 2019, human population growth in the region varied from a 17% decrease to a 171% increase (mean = +43%) with only 5 of the 72 SE US counties losing population, and nearly half growing by more than 40%. Individual counties experienced between 999 and 19,253 km2 of new development (mean: 5725 km2), with 1–5% (mean: 2.6%) of undeveloped lands undergoing development over this period across the region. Correspondingly, our survey of 169 coastal experts highlighted development, shoreline hardening, and upstream modifications to freshwater flow as the most important local threats facing coastal wetlands. Similarly, experts identified development, upstream modifications to freshwater flow, and overharvesting as the most important local threats to oyster reefs. With regards to global threats, experts categorized sea level rise as the most pressing to wetlands, and acidification and precipitation changes as the most pressing to oyster reefs. Survey respondents further identified that more research, driven by collaboration among scientists, engineers, industry professionals, and managers, is needed to assess how precipitation changes, shoreline hardening, and sea level rise are affecting coastal ecosystem stability and function. Due to the profound role of humans in shaping estuarine health, this work highlights that engaging property owners, recreators, and municipalities to implement strategies to improve estuarine health will be vital for sustaining coastal systems in the face of global change.

Quantifying organic matter and functional groups in particulate matter filter samples from the southeastern United States – Part 2: Spatiotemporal trends

Abstract. Organic species within atmospheric particles vary widely in molecular structure. The variety of molecules that comprise the aerosol make it rich in information about its sources and chemical life cycle but also make particulate organic matter (OM) difficult to characterize and quantify. In Part 1 of this pair of papers, we described a direct method for measuring the composition and concentrations of OM in aerosol samples that is compatible with routine monitoring of air quality. This method uses Fourier transform infrared (FT-IR) spectrometry of filter-based aerosol samples to quantify bonds, or functional groups, that represent the majority of organic composition. Summation of these functional groups gives OM. In this paper, functional group and OM concentrations are directly measured in 8 years of aerosol samples collected at two rural and two urban sites in the Southeastern Aerosol Research and Characterization (SEARCH) network. FT-IR spectrometry with a multivariate calibration is used to quantify the concentrations of aliphatic C−H (aCH), carboxylic acid (COOH), oxalate (oxOCO; representing carboxylates), non-acid and non-oxalate carbonyl (naCO), and alcohol O−H (aCOH) in approximately 3500 filter samples collected every third day from 2009 through 2016. In addition, measurements are made on samples from all days in 2016. To the best of our knowledge, this is the longest time period over which this type of analysis has been applied, and this work also demonstrates the application of a more chemically complete and less destructive method than in prior work using alternate techniques. A decline in the total OM is observed from 2011 to 2016 due to a decrease in the more oxygenated functional groups (carboxylic acid and oxalate) and is attributed to anthropogenic SO2 and/or volatile organic compound (VOC) emissions reductions. The trend in OM composition is consistent with those observed using more time- and labor-intensive analytical techniques. Concurrently, the fractional contributions of aCOH and naCO to OM increased, which might be linked to monoterpene-derived secondary OM, with plausible influences from decreasing NOx and/or increasing O3 concentrations. In addition, this work demonstrates that OM to organic carbon (OM/OC) ratios in the southeastern US (SE US) did not appreciably change over the study time period as a result of these competing functional group contributions to OM. Monthly observations support the sources suggested by these overall trends, including evidence of strong biogenic and photo-oxidation influences. Daily samples from 2016 further elucidate the consistent impact of meteorology and biomass burning events on shorter-term OM variability, including prescribed burning in the winter or spring and wildfires in the autumn, although these sources did not appear to be strong contributors to long-term OM or composition trends in the SE US. These shorter-term and spatial observations reinforce the results of the broader dataset and serve to evaluate the applicability of FT-IR spectrometry measurement to trends analysis on various timescales relevant to routine monitoring of aerosol composition.

Mechanisms for Springtime Onset of Isolated Precipitation across the Southeastern United States

This study uses four-year radar-based precipitation organization and reanalysis datasets to study the mechanisms that lead to the abrupt springtime onset of precipitation associated with isolated storms in the Southeast United States (SE US). Although the SE US receives relatively constant precipitation year-round, previous work demonstrated a “hidden” summertime maximum in isolated precipitation features (IPF) whose annual cycle resembles that of monsoon climates in the subtropics. In the SE US, IPF rain abruptly ramps up in May and lasts until sometime between late August and early October. This study suggests that the onset of the IPF season in the SE US is brought about by a combination of slow thermodynamic processes and fast dynamic triggers, as follows. First, in the weeks prior to IPF onset, a gradual seasonal build-up of convective available potential energy (CAPE) occurs in the Gulf of Mexico. Then, in one-to-two pentads prior to onset, the upper-tropospheric jet stream shifts northward, favoring the presence of slow-moving frontal systems in the SE US. This poleward shift in the jet stream location in turn allows the establishment of the North Atlantic subtropical high western ridge over the SE US which, with associated poleward transport of high CAPE air from the Gulf of Mexico, leads to the establishment of the warm-season regime of IPF precipitation in the SE US.

Effects of Production of Woody Pellets in the Southeastern United States on the Sustainable Development Goals

Wood-based pellets are produced in the southeastern United States (SE US) and shipped to Europe for the generation of heat and power. Effects of pellet production on selected Sustainability Development Goals (SDGs) are evaluated using industry information, available energy consumption data, and published research findings. Challenges associated with identifying relevant SDG goals and targets for this particular bioenergy supply chain and potential deleterious impacts are also discussed. We find that production of woody pellets in the SE US and shipments to displace coal for energy in Europe generate positive effects on affordable and clean energy (SDG 7), decent work and economic growth (SDG 8), industry innovation and infrastructure (SDG 9), responsible consumption and production (SDG 12), and life on land (SDG 15). Primary strengths of the pellet supply chain in the SE US are the provisioning of employment in depressed rural areas and the displacement of fossil fuels. Weaknesses are associated with potential impacts on air, water, and biodiversity that arise if the resource base and harvest activities are improperly managed. The SE US pellet supply chain provides an opportunity for transition to low-carbon industries and innovations while incentivizing better resource management.

Translating CDSMP to the Workplace: Results of the Live Healthy Work Healthy Program.

Report the results of a randomized, controlled trial of Live Healthy, Work Healthy (LHWH), a worksite translation of the Chronic Disease Self-Management Program (CDSMP). 14 worksites were randomly assigned to LHWH, standard CDSMP (usual care) or no-intervention (control) group. The diverse set of work organizations centered around a rural community in SE US. 411 participants completed baseline data with 359 being included in the final analyses. LHWH had been adapted to fit the unique characteristics of work organizations. This translated program consists of 15 sessions over 8 weeks and was facilitated by trained lay leaders. The primary outcomes including health risk, patient-provider communication, quality of life, medical adherence and work performance were collected pretest, posttest (6 mos.) and follow-up (12 mos.). Analyses were conducted using latent change score models in a structural equation modeling framework. 79% of participants reported at least one chronic condition with an average of 2.7 chronic conditions reported. Results indicated that LHWH program demonstrated positive changes in a most outcomes including significant exercise (uΔ = 0.89, p < .01), chronic disease self-efficacy (uΔ = 0.63, p < .05), fatigue (uΔ = -1.45, p < .05), stress (uΔ = -0.98, p < .01) and mentally unhealthy days (uΔ = -3.47, p < .001). The translation of LHWH is an effective, low cost, embeddable program that has the potential to improve the health and work life of employees.

In pursuit of a homegrown biofuel: Navigating systems of partnership, stakeholder knowledge, and adoption of Brassica carinata in the Southeast United States

An emerging off-season crop in the Southeast United States (SE US) may provide farmers and industry with a climate-friendly means of enhancing the region’s agricultural and bioenergy landscapes. Carinata (Brassica carinata) is an industrial oilseed that serves as a feedstock for renewable jet fuel and promises producers financial and soil health benefits. The likelihood of carinata adoption among producers depends on how well this technology fits within the region’s complex cultural and socio-economic conditions. This paper examines factors shaping adoption among producers in the SE US, taking into consideration theories of technology adoption that place emphasis on both the individual and complex systemic factors. Findings indicate respondents perceive agronomic and economic benefits of adopting carinata into seasonal rotations, but previous growers largely fail to link carinata to environmental benefits beyond the farmgate. Respondents identify barriers to carinata adoption at multiple scales. Unfamiliarity with carinata leads as a major barrier and respondent narratives reflect wide-ranging perceptions defying analytical categorization. Respondents identify solutions to overcome critical adoption barriers, such as industry responsibility, research on carinata variety improvement, and land grant extension activities. Results reinforce the complex interconnectivity of factors influencing adoption decision-making and highlight the importance of clearly defining stakeholder roles within the public-private partnership promoting carinata expansion. The study highlights opportunities and challenges of land grant extension systems that attempt to unite stakeholders across scales. Finally, the study discusses implications of the apparent disconnect between factors that influence producers’ adoption decision-making locally and the global forces that drive the carinata market.

Spatiotemporal recruitment patterns of two introduced Magnolia L. species in a disturbed oak forest

ABSTRACT Although nearly half of all Magnolia species are threatened globally, human-assisted movement and cultivation of some species has led to their escape within non-indigenous ecosystems. The ongoing naturalization of select Magnolia taxa has been associated with climate change and variously characterized as assisted-migration, range shift/expansion, or biological invasion. This study documented recruitment patterns in space and time for two species of introduced ‘umbrella’ magnolias, which have become increasingly prolific in New England. A census was conducted that identified a total of 388 Magnolia macrophylla (SE US.) and M. obovata (Japan) individuals that escaped from cultivation and colonized an adjacent oak forest. Seedling recruitment occurred rapidly in response to forest disturbance, and mean tree age was significantly different as a function of three discrete disturbance events. M. obovata was a more successful colonizer overall, yielding more individuals (326 vs. 62), and recruiting further (90% quantile = 388 ± 91 vs. 228 ± 44 m) than M. macrophylla, given founding populations that were of identical size (n = 3) and similar age. This study represents the first documented escape of M. obovata in North America, while M. macrophylla has been documented elsewhere in New England and linked to increased temperature and precipitation patterns.

Brassica carinata genotypes demonstrate potential as a winter biofuel crop in South East United States

Brassica carinata A. Braun, grown as a winter crop on underutilized agricultural land in the southeast United States (SE US), may provide a new rotation alternative and augment income for producers. Widespread adoption of Brassica carinata as a winter crop in the SE US requires varieties with cold tolerance, acceptable and stable seed yield, oil content, protein content so that the crop will be complementary with the normal cultivation of summer crops such as cotton (Gossypium hirsutum L.), corn (Zea mays L.), soybean (Glycine max L. Merr), sorghum (Sorghum bicolor L. Moench) and peanut (Arachis hypogaea L.). The objective of this study was to evaluate the performance of 11 Brassica carinata genotypes for agronomically important traits including seed yield, oil and protein content, oil quality, days to bolting, flowering and maturity at three locations during two growing seasons (2015–2017) as a winter crop in the SE US. Interactions between genotype and environment played a crucial role in overall agronomic performance. This study provides key information on the effect of environmental conditions, such as precipitation and temperature on the agronomic performance of carinata along with generation of information related to region-specific requirements for the crop in the SE US. Days to maturity ranged from 154 to 165 days. The average yield of the 11 genotypes tested ranged from 2814 kg/ha to 3401 kg/ha, which were improved from earlier studies, demonstrating gain due to regional selection and breeding efforts. Total oil content ranged from 42.0 % to 52.4 %, while the erucic acid (C22:1) content ranged from 40.7 % to 42.9 % on a whole seed basis. Based on these results, specific genotypes with consistently high seed yield, oil, erucic acid and protein content with shorter life cycle irrespective of location or year were identified. Brassica carinata has potential as a viable bioenergy winter crop to be integrated into the cropping systems in the SE US and other regions of the world.

Effects of the North Atlantic Subtropical High on summertime precipitation organization in the southeast United States

AbstractThis study analyzes the effect of the location of the North Atlantic Subtropical High (NASH) western ridge on the daily variability of precipitation organization in the southeastern United States (SE US). The western side of the NASH, also known as the NASH western ridge, plays an important role in the variability of summertime precipitation in this region. In this study, the mean summertime position of the NASH western ridge was determined and used to classify each summer day during 2009–2012 into one of four quadrants. Composites of synoptic‐scale circulation and precipitation from mesoscale and isolated precipitation features (MPF and IPF) were calculated for each NASH western ridge quadrant. MPF contributed most (about 65%) of the total summertime precipitation and accounted for most of the differences between the four NASH quadrants. Domain‐averaged precipitation was highest (lowest) during NASH‐SW (NASH‐NW) when IPF (MPF) precipitation was strongest (weakest). The regionality of MPF precipitation maxima was generally associated with the location of low‐level jets and upper‐level troughs. For instance, positive MPF anomalies occurred across the SE US during NASH‐SW when the Great Plains low‐level jet turned eastward bringing moisture to fuel convection in the SE US. In contrast, IPF rain was distributed more uniformly across the SE US. Finally, this study revealed a dipole of precipitation that is controlled by the position of the NASH western ridge and its associated low‐level jets. In one extreme of the dipole NASH‐SE, periods are associated with enhanced MPF precipitation along the coast and offshore for days at a time, and suppressed MPF precipitation inland. The opposite pattern occurs during NASH‐NW when MPF precipitation is enhanced inland and suppressed along the coast and offshore.

Plant Growth Nullifies the Effect of Increased Water‐Use Efficiency on Streamflow Under Elevated CO2 in the Southeastern United States

AbstractPlant response to elevated CO2 concentration is known to increase leaf‐level water‐use efficiency through a reduction in stomatal opening. Recent studies have emphasized that increased plant water‐use efficiency can ameliorate the impact of drought due to climate change. However, there is a potentially counterbalancing impact due to the increased leaf area. We investigate long‐term trends (1951 to 2015) of observed streamflow in the Southeastern United States (SE US) and quantify the contribution of major drivers of streamflow changes using single factor climate modeling experiments from Community Land Model Version 5 (CLM5). The SE US streamflow observations do not exhibit a trend, which is in agreement with the CLM5 control experiment. Using the factorial set of CLM5 experiments, we find that increased leaf area under elevated CO2 leads to decreased runoff and completely counteracts increased runoff due to water‐use efficiency gains under elevated CO2 and land‐use change.

Opportunities and attitudes of private forest landowners in supplying woody biomass for renewable energy

Woody biomass has been identified as a source of dispatchable, renewable energy. Private lands supply the majority of the wood-based pellets that is produced in the southeastern United States (SE US) and shipped to countries in the European Union (EU) for energy generation. To assess the perspectives of potential suppliers of woody biomass in the SE US, nonindustrial private forest landowners were surveyed in the fuelsheds of the two primary ports for wood pellets exported to the EU. The survey assessed owners' characteristics, attitudes, and future management plans. Survey results were examined to explore the relationships among these factors and owners' intentions for providing material for wood-based energy. The results indicate that forest landowners have multiple reasons for maintaining their forest land, with more than 40% of the owners ranking timber production as a very important reason. Furthermore, the majority of landowners would be willing to provide woody biomass for producing bioenergy. Among factors that would enhance landowners' willingness to provide woody biomass for energy, technical assistance to improve stand productivity and future value was the most popular option, followed by reducing fire and disease risk, long-term markets, and high prices. Landowner willingness to provide woody material for bioenergy also varied depending on demographics including age and gender, property characteristics including holding size and distance to residence, and perceptions regarding the impact on forest value of wood pellet demand and the viability of bioenergy as an alternative to fossil energy.

Multi-year surface radiative properties and vegetation parameters for hydrologic modeling in regions of complex terrain—Methodology and evaluation over the Integrated Precipitation and Hydrology Experiment 2014 domain

Study regionSoutheast US (SE US). Study focusThis study probes the propagation of errors in standard remote-sensing vegetation products caused by cloud contamination and the impact of time-variant radiative properties for correctly describing land-surface properties in hydrologic models. Spatiotemporally-varying quality-controlled vegetation attributes (i.e., leaf area index and fractional vegetation coverage) and surface radiative properties (i.e., longwave broadband emissivity and shortwave broadband albedo) were derived from MODIS (Moderate Resolution Imaging Spectroradiometer) products over the SE US at 1 km × 1 km and hourly resolutions from 2007 to 2013. The data sets are publicly available. The impact of uncorrected standard vegetation products and static treatments of radiative properties was assessed systematically clearly illustrating improvements in simulated water and energy fluxes using the developed landscape attributes with a fully-distributed uncalibrated hydrologic model. New hydrological insights for the regionThrough simulations in the Southern Appalachian Mountains, we found that the spatiotemporal variability of radiative properties significantly influences the diurnal cycle of the surface energy budget with marked differences in sensible heat fluxes (up to 10–20%). Better performance of streamflow simulations achieved by using the improved vegetation attributes is tied to changes in rainfall interception and evapotranspiration, reflecting the importance of SE forests in the regional water cycle. The largest improvements in streamflow simulations result from larger corrections to MODIS products in the inner mountain region where cloudiness is persistent.