Ozark Highlands Research Articles

Soil carbon sequestration across a chronosequence of tallgrass prairie restorations in the Ozark Highlands region of northwest Arkansas

Prairie restoration studies and research conducted in native prairie systems have been mostly centered in the Great Plains region of the United States and little research has been pursued in Arkansas to further understand the soil carbon (C) sequestration potential over time of remnant prairie sites and prairie restorations. The objective of this study was to evaluate the effects of restoration age and soil moisture regime on near-surface soil C and other soil property changes over time in a chronosequence of humid-temperate tallgrass prairie restorations (i.e., 15, 16, 17, and 38 yr) in the Ozark Highlands region of northwest Arkansas. A nearby undisturbed, native prairie was also studied for comparison as a baseline. Soil samples were collected from the top 10 cm in 2005 and 2017 and the change over time was assessed for soil bulk density, pH, electrical conductivity, soil organic matter (SOM), total C (TC), total nitrogen (TN), and the fraction of TC and TN in SOM. Soil property magnitudes from the 2017 sampling only were also compared among sites to evaluate the current state of the restorations. Soil properties within the restorations generally behaved as expected, with beneficial decreases in soil BD and increases in SOM, TC, TN, and TC and TN fractions of SOM occurring over time as restoration age increased and tended towards that in the native prairie. The direct measurement of change in total C content over time differed (P = 0.03) between soil moisture regimes among ecosystems, where the greatest soil C sequestration rate of 0.6 Mg C ha−1 yr−1 was recorded in the native prairie in the aquic soil moisture regime, while soil C sequestration rates ranged from −0.21 to 0.12 Mg C ha−1 yr−1 across the four prairie restorations. Results indicate that the prairie restorations evaluated in this study are still evolving and have not yet reached the rate of C sequestration observed in the native, undisturbed prairie ecosystem and that direct measurement of soil C storage changes over time should be used whenever possible.

Modelling effects of invasive species and drought on crayfish extinction risk and population dynamics

Abstract Hydrological alteration, which may be exacerbated by climate change, is known to facilitate aquatic species invasion. Altered hydrology, invasive species, and the additive effects of these stressors pose a threat to aquatic biodiversity. Understanding extinction risk in the context of these stressors is crucial for prioritizing conservation efforts. As case studies, three narrow‐ranged endemic crayfish species of conservation concern (Faxonius marchandi, Faxonius roberti, and Cambarus hubbsi) in the Ozark Highlands of Arkansas and Missouri, USA, were used to examine the effects of invasive species and drought on crayfish population dynamics. The objectives of this study were to model the population dynamics of these imperilled species, assess how these populations may be affected under increased invasion effects and intensified drought, determine potential refuge effects, and examine the sensitivity of quasi‐extinction to model parameters. ramas‐metapop was used to construct stage‐based demographic models. Terminal extinction risk, median time to quasi‐extinction, and metapopulation occupancy were used to assess population viability under different scenarios. Cambarus hubbsi appears to be highly susceptible to decline if survival rates are reduced by simulated drought, as they have low reproductive potential and mature slowly. Models indicated that potential refuges allow F. roberti and C. hubbsi to persist, even when invasion and drought effects were extreme. Conversely, barriers to dispersal for F. marchandi led to reduced quasi‐extinction times and the greatest extinction risk under most invasion scenarios. Quasi‐extinction was most sensitive to changes in juvenile survival for all species examined, which indicates that improved estimates of stage‐specific demographic parameters for crayfish will improve model predictions. An increased understanding of the mechanisms of displacement of native crayfish by invasive crayfish is needed for most crayfish species. Limiting the spread of invasive species, maintaining natural habitat and hydrological regimes, and gaining insight into life histories and demographic parameters will increase the ability to conserve endemic and imperilled crayfish.

Phytophthora Species Detected in Two Ozark Forests with Unusual Patterns of White Oak Mortality.

Widespread decline and mortality of white oaks (Quercus alba) occurred in Missouri Ozark forests between 2011 and 2017. Symptoms included rapid crown death with bronzing of leaves, retention of dead leaves, crown dieback and thinning, and loss of large limbs within one year of death. Decline and mortality were associated with hillside drainages and fit descriptions of European oak forests predisposed to decline by pathogenic Phytophthora species. A survey was performed at two locations in 2014 and 2015 to assess the distribution of dead and declining white oaks, and the occurrence and distribution of Phytophthora species. Multiple Phytophthora species were detected, including P. cinnamomi, P. cactorum, P. europaea, and P. pini. P. cinnamomi was the most common and widely distributed species among plots at both locations. The detection of P. cinnamomi at the base of white oaks was not associated with poor crown vigor. However, more quantitative survey techniques are necessary to clearly evaluate this relationship. P. cinnamomi kills fine roots of white and red oaks in North America and has been associated with the decline of white oaks in the United States (Ohio) and other countries. Further studies are needed to determine the importance of P. cinnamomi in oak decline within the Ozark highlands.

Propagation of Eastern Hellbenders Cryptobranchus alleganiensis alleganiensis in a Recirculating Aquaculture System at Shepherd of the Hills State Fish Hatchery

AbstractThe hellbender Cryptobranchus alleganiensis is an endangered aquatic salamander inhabiting coldwater streams within the Ozark Highlands of Missouri. Over the past few decades, there has been a severe decline in the populations of the two subspecies of hellbender in this region—the Eastern hellbender C. a. alleganiensis and the Ozark hellbender C. a. bishopi—accompanied by little to no recruitment of young age‐classes; projections now call for negative long‐term population growth for both subspecies. Captive propagation is thus considered essential for the long‐term recovery of this species in Missouri, along with addressing the causes for its decline in the wild. Since 2007, Shepherd of the Hills Fish Hatchery has been the primary rearing facility in Missouri for the early life stages of Eastern hellbenders. This facility has focused on hatching fertilized eggs collected from the wild and rearing animals for repatriation into their natal streams. This paper describes the recirculating aquaculture system used to rear Eastern hellbenders, the culture techniques that have been developed, and some of the results.

Hybridization and Genetic Structure of Neosho Smallmouth Bass in the Ozark Highlands

AbstractThe Neosho Smallmouth Bass Micropterus dolomieu velox is endemic to Arkansas River tributaries originating in the Ozark Highlands and Boston Mountains. Although morphologically and genetically distinct from other populations of Smallmouth Bass M. dolomieu, the conservation‐genetic status of Neosho Smallmouth Bass is largely unknown. To assist in filling this data gap, we quantified introgressive hybridization, genetic diversity, and population structure of Neosho Smallmouth Bass in two major river basins (Grand River and Illinois River) using seven polymorphic microsatellite markers. Introgressive hybridization with stocked Tennessee lake‐strain Smallmouth Bass was most prevalent in the Illinois River, wherein the overall genomic proportion of Neosho Smallmouth Bass alleles was only 0.422. After accounting for hybrid individuals, genetic diversity of Neosho Smallmouth Bass was generally higher in larger rivers and lower in smaller, isolated streams. Three distinct population clusters were identified at the uppermost level of genetic structure—one from the Illinois River basin and two from the Grand River basin. These three population boundaries accounted for approximately 7% of the hierarchical genetic variation within our data set, and substructure below the uppermost level accounted for an additional 2% of genetic variation. The population structure we discovered can provide a blueprint for management that conserves diversity within and among populations; for example, population boundaries can be used to determine brood source locations for supplemental stocking efforts to counter nonnative introgression. Introgressive hybridization with nonnative Smallmouth Bass appears to be the most pertinent threat to the Neosho Smallmouth Bass subspecies, which is of conservation value to the overall adaptability of Smallmouth Bass as a species.

Spatiotemporal shifts in distribution of a recolonizing black bear population

AbstractFollowing one of the most successful relocations of a large carnivore species, American black bears (Ursus americanus; hereafter bears) have expanded from Arkansas to the Ozark Highlands of southern Missouri, USA, where they were potentially extirpated in the early 1900s. Our first objective was to estimate spatial and temporal shifts in probability of bear presence to understand the population distribution in Missouri. Our second objective was to assess which factors might influence any detected shifts. We used public sightings of bears to develop statewide spatial distribution models for early (1991–2003) and late (2004–2015) bear presence probability in Missouri using maximum entropy modeling and determine the rate and direction of population expansion. We evaluated the effects of environmental variables (e.g., land cover, roads) on bear presence probability and predicted the total area of three levels of bear presence probabilities. The average annual density of bear sightings increased temporally by about 3.4/1000 km2 in Missouri. The Ozark Highlands ecoregion contained the highest average annual density of sightings during both time periods. The bear presence probability increased spatially about 29 km in a north–northwest direction between the two time periods and the distribution became more dispersed over time. Our results corroborate prior findings suggesting bear presence is greatest in forests and rural areas. However, the increased importance of cultivated crops over time combined with the consistently positive relationship with roads indicates little negative effects from anthropogenic features on the bear presence probability in Missouri.

Efficiency of Sampling Sunfishes Using Snorkeling in Clear, Warm-Water Streams of the South-Central United States

AbstractThe continued evaluation of fish-sampling gears and methods is essential to identify their applicability across environmental conditions and among species. Although limited by visibility, snorkeling has potential advantages relative to other fish-sampling gears in wadeable streams (e.g., minimally intrusive, cost effective, and appropriate in deeper areas). Clear water is common to warm-water streams; however, the use of snorkeling for monitoring stream-fish populations has largely focused on cold-water systems. To assess relative snorkeling efficiency in warm-water streams, we compared standardized single-pass snorkel counts to tow-barge electrofishing abundance estimates for six sunfishes (Centrarchidae) in the Ozark Highlands ecoregion of northwest Oklahoma and southwest Missouri under relatively similar environmental conditions (i.e., clear water, cobble substrates, low-flow conditions). Snorkeling efficiency was variable among sunfishes and consistently low for species with cryptic traits and habitat use. We also did not detect cryptic sunfishes (i.e., a single individual was not encountered) using snorkeling at multiple stream reaches where estimated abundance was > 50 within a 0.5- to 1.0-km stream reach. Our findings indicate that snorkeling has applications for monitoring sunfish populations and assemblages when using an abundance estimator or accounting for imperfect detection; however, it is inappropriate for estimating population size of cryptic sunfishes. We encourage continued research into the applicability of snorkeling to estimate warm-water stream fish abundance.

Songbird nest success is positively related to restoration of pine–oak savanna and woodland in the Ozark Highlands, Missouri, USA

ABSTRACT Savanna and woodland are transitional vegetation communities that have largely disappeared while many early-successional bird species have simultaneously declined in abundance. Pine savanna and woodland are being restored in the Midwest through prescribed fire and tree thinning to create their characteristic open canopy, dense ground layer, and variable shrub cover. Ideally, these restoration strategies for vegetation should also facilitate bird conservation objectives. We determined daily nest survival (DSR) for 6 songbird species, representing both shrub-nesting and canopy-nesting species, in southern Missouri, USA, in 2014 and 2015. We evaluated support for hypotheses relating temporal, vegetation, and management factors to DSR. We predicted that nest survival of the 3 shrub-nesting species (Eastern Towhee [Pipilo erythrophthalmus], Yellow-breasted Chat [Icteria virens], and Prairie Warbler [Setophaga discolor]) would show positive relationships with thinning and fire, but only Yellow-breasted...

Using a tree seedling mortality budget as an indicator of landscape-scale forest regeneration security

Securing desirable forest regeneration outcomes is an essential component of sustainable forest management. When natural reproduction is preferred over planting, achieving desirable outcomes may be the principal challenge for forest managers, as reports of struggles and even failures are common across many regions and forest ecosystems. Informing managers and policymakers of the prospects of regeneration success before practices and policies are implemented promotes long-term sustainability because rehabilitating undesirable regeneration outcomes is often lengthy, expensive, and uncertain. In 2012, the USDA Forest Service, Northern Research Station, Forest Inventory and Analysis program implemented Regeneration Indicator (RI) protocols that added detailed seedling measurements and browse impact assessments to a subsample of inventory plots across 24 states in the northern United States. The goal of this expanded sampling effort is to improve the ability to monitor broad scale regeneration trends and better inform forest management planning and policy. Modeling probable regeneration outcomes is difficult and the rarity of vetted models that can fully utilize RI inventory data highlights an immediate need for flexible methods to evaluate regeneration of different taxa at large scales. This manuscript is premised on estimation of a tree seedling mortality budget for inventoried reproduction. The method offers a transparent structure for leveraging existing literature and expert knowledge to gain provisional insight into plausible regeneration outcomes. The resulting tool provides flexibility for users to examine regeneration for multiple species, site conditions, and user-defined quantitative regeneration objectives. The approach is demonstrated by applying a suite of multispecies regeneration objectives to RI data for two case studies with different forest composition and geographic scales, the Ozark Highland Ecological Section (OHES) and the Monongahela National Forest (MNF). Within the Quercus/Carya dominated OHES, analyses indicate that desirable regeneration outcomes are more likely than not based on current plot conditions. Regeneration events were projected to produce new fully stocked forests on 76% of OHES plots, produce a sizable component of characteristic overstory species on 57%, and produce a sizable component of commercially important species on 59%. Within the Acer/Fagus/Betula and Quercus/Carya forests of the MNF, analyses indicated that difficulties in achieving desirable regeneration outcomes were likely. Only 36% of MNF plots were projected to produce new fully stocked forests following a regeneration event and only 29% were projected to regenerate a sizable component of either characteristic overstory species or commercially important species.

Groundwater flux estimation in streams: A thermal equilibrium approach

Stream and groundwater interactions play an essential role in regulating flow, temperature, and water quality for stream ecosystems. Temperature gradients have been used to quantify vertical water movement in the streambed since the 1960s, but advancements in thermal methods are still possible. Seepage runs are a method commonly used to quantify exchange rates through a series of streamflow measurements but can be labor and time intensive. The objective of this study was to develop and evaluate a thermal equilibrium method as a technique for quantifying groundwater flux using monitored stream water temperature at a single point and readily available hydrological and atmospheric data. Our primary assumption was that stream water temperature at the monitored point was at thermal equilibrium with the combination of all heat transfer processes, including mixing with groundwater. By expanding the monitored stream point into a hypothetical, horizontal one-dimensional thermal modeling domain, we were able to simulate the thermal equilibrium achieved with known atmospheric variables at the point and quantify unknown groundwater flux by calibrating the model to the resulting temperature signature. Stream water temperatures were monitored at single points at nine streams in the Ozark Highland ecoregion and five reaches of the Kiamichi River to estimate groundwater fluxes using the thermal equilibrium method. When validated by comparison with seepage runs performed at the same time and reach, estimates from the two methods agreed with each other with an R2 of 0.94, a root mean squared error (RMSE) of 0.08 (m/d) and a Nash–Sutcliffe efficiency (NSE) of 0.93. In conclusion, the thermal equilibrium method was a suitable technique for quantifying groundwater flux with minimal cost and simple field installation given that suitable atmospheric and hydrological data were readily available.

Two new species of freshwater crayfish of the genus Faxonius (Decapoda: Cambaridae) from the Ozark Highlands of Arkansas and Missouri

Two new species of freshwater crayfish are described from the Ozarks Plateau of northern Arkansas and southern Missouri. Both species are restricted to the mainstem of rocky streams that are at least fourth-order or greater in size. Recent genetic and morphological investigations of the coldwater crayfish, Faxonius eupunctus Williams, 1952, indicated that it was actually composed of several undescribed species. Faxonius eupunctus is herein restricted to just the Eleven Point River system. Faxonius roberti, new species is found in the mainstem of the Spring and Strawberry river systems in northern Arkansas. It differs from F. eupunctus by lacking a male Form-I gonopod with a distal spatulate mesial process, and presence of two spines on the dorsal side of the merus, where F. eupunctus typically has 1 spine. Faxonius wagneri, new species is known from a 54 mile (86 km) stretch of the Eleven Point River mainstem, ranging from just southeast of Greer, Missouri to just north of Birdell, Arkansas. Faxonius wagneri can be differentiated from both F. eupunctus and Faxonius roberti sp. nov. by using the male Form-I and Form-II gonopods, the shape of the chelae, and the female annulus ventralis. In F. wagneri, the terminal elements of the first pleopod are almost twice as long as those in F. eupunctus and F. roberti, with the tips of the appendage reaching the posterior base of the first perieopod when the abdomen is flexed forward, whereas, in the other two species, these elements only reach the base of the second pereiopod. The species also possesses two spines on the dorsal side of the merus of the first pereiopod, which helps distinguish it from F. eupunctus.

The influence of drought on flow‐ecology relationships in Ozark Highland streams

Abstract Drought and summer drying can have strong effects on abiotic and biotic components of stream ecosystems. Environmental flow‐ecology relationships may be affected by drought and drying, adding further uncertainty to the already complex interaction of flow with other environmental variables, including geomorphology and water quality. Environment–ecology relationships in stream communities in Ozark Highland streams, USA, were examined over two years with contrasting environmental conditions, a drought year (2012) and a flood year (2013). We analysed fish, crayfish and benthic macroinvertebrate assemblages using two different approaches: (1) a multiple regression analysis incorporating predictor variables related to habitat, water quality, geomorphology and hydrology and (2) a canonical ordination procedure using only hydrologic variables in which forward selection was used to select predictors that were most related to our response variables. Reach‐scale habitat quality and geomorphology were found to be the most important influences on community structure, but hydrology was also important, particularly during the flood year. We also found substantial between‐year variation in environment–ecology relationships. Some ecological responses differed significantly between drought and flood years, while others remained consistent. We found that magnitude was the most important flow component overall, but that there was a shift in relative importance from low flow metrics during the drought year to average flow metrics during the flood year, and the specific metrics of importance varied markedly between assemblages and years. Findings suggest that understanding temporal variation in flow‐ecology relationships may be crucial for resource planning. While some relationships show temporal variation, others are consistent between years. Additionally, different kinds of hydrologic variables can differ greatly in terms of which assemblages they affect and how they affect them. Managers can address this complexity by focusing on relationships that are temporally stable and flow metrics that are consistently important across groups, such as flood frequency and flow variability.

Risk Indicators for Identifying Critical Source Areas in Five Arkansas Watersheds

Abstract. Change point analysis was used to explore the interactions between watershed characteristics and concentrations of nitrate-nitrogen, total nitrogen, soluble reactive phosphorus, and total phosphorus in streams within the Ozark Highlands, Arkansas Valley, and Ouachita Mountains ecoregions of Arkansas. Thresholds were identified for multiple watershed metrics used to predict water quality, including percent forest in the catchment, agricultural and forested land use in the riparian buffer, stream density, and poultry house density. Based on the observed relationships from the sampled watersheds, we propose four risk indicators to improve the identification of critical source areas for NPS pollution mitigation: subwatersheds that have less than 50% forested area within the drainage area, less than 50% forested area in the riparian buffer zone, more than 0.9 poultry houses km-2, and a stream density that exceeds 50 m ha-1. Keywords: Nonpoint-source pollution, Source water protection, Watershed management.

Seasonal Effects on Leachate Quality from an Ozark Highlands Managed Grassland Using Automated, Equilibrium‐Tension Lysimeters

Core Ideas Lysimeters aid subsurface water quality assessments in long‐term nutrient management plots. Broiler litter rates affected few leachate quality parameters during a continuous 8‐yr period. Leachate water quality was affected by season during a continuous 8‐yr period. In regions with concentrated broiler (Gallus gallus) production, land application is a useful means of managing broiler litter (BL). However, surface and subsurface water quality issues may arise when continued annual BL application to fields occurs for extended periods. The application of manure follows seasonal guidelines for surface water quality protection. The objective of this study was to evaluate the effects of BL rate (0, 5.6, and 11.2 Mg litter ha−1) and season on drainage and leachate water quality over an 8‐yr period (2003–2011) in the Ozark Highlands with karst geology using automated, equilibrium‐tension lysimeters. During the 8‐yr period, seasonal drainage was unaffected by season or BL rate, averaging 118 mm per season. Averaged across BL rates, seasonal leachate pH, electrical conductivity (EC), flow‐weighted mean (FWM) NO3–N, dissolved organic C, S, and Zn concentrations, and NH4–N, Cu, Fe, and Se loads differed (P < 0.05) among seasons. Averaged across seasons, seasonal leachate EC, FWM PO4–P, total P, and S concentrations, and Ni load differed (P < 0.05) among BL rates. With the exception of As and Se, seasonal FWM leachate Cd, Cr, Cu, and NO3–N concentrations were at least five times smaller than their maximum contaminant level for drinking water during any of the four seasons. Since rainfall patterns seasonally change in many regions of concentrated poultry production, seasonal differences in the leachate water quality response to continuous annual application of BL are important to help tailor best management practices to protect soil and water resources in regions underlain by karst geology.

Sampling the stream landscape: improving the applicability of an ecoregion-level capture probability model for stream fishes

Temporal and spatial variability in streams result in heterogeneous gear capture probability (i.e., the proportion of available individuals identified) that confounds interpretation of data used to monitor fish abundance. We modeled tow-barge electrofishing capture probability at multiple spatial scales for nine Ozark Highland stream fishes. In addition to fish size, we identified seven reach-scale environmental characteristics associated with variable capture probability: stream discharge, water depth, conductivity, water clarity, emergent vegetation, wetted width–depth ratio, and proportion of riffle habitat. The magnitude of the relationship between capture probability and both discharge and depth varied among stream fishes. We also identified lithological characteristics among stream segments as a coarse-scale source of variable capture probability. The resulting capture probability model can be used to adjust catch data and derive reach-scale absolute abundance estimates across a wide range of sampling conditions with similar effort as used in more traditional fisheries surveys (i.e., catch per unit effort). Adjusting catch data based on variable capture probability improves the comparability of data sets, thus promoting both well-informed conservation and management decisions and advances in stream-fish ecology.

Stream permanence is related to crayfish occupancy and abundance in the Ozark Highlands, USA

AbstractCrayfish use of intermittent streams is especially important to understand in the face of global climate change. We examined the influence of stream permanence and local habitat on crayfish occupancy and species densities in the Ozark Highlands, USA. We sampled in June and July 2014 and 2015. We used a quantitative kick–seine method to sample crayfish presence and abundance at 20 stream sites with 32 surveys/site in the Upper White River drainage, and we measured associated local environmental variables each year. We modeled site occupancy and detection probabilities with the software PRESENCE, and we used multiple linear regressions to identify relationships between crayfish species densities and environmental variables. Occupancy of all crayfish species was related to stream permanence. Faxonius meeki was found exclusively in intermittent streams, whereas Faxonius neglectus and Faxonius luteus had higher occupancy and detection probability in permanent than in intermittent streams, and Faxonius ...

Swamp Rabbit Distribution on the Northern Edge of their Range in Missouri

Sylvilagus aquaticus (Swamp Rabbit) is an imperiled species in Missouri that inhabits highly fragmented bottomland forested habitats in the southeastern portion of the state. Between 2010 and 2012, we conducted repeated, extensive presence—absence winterlatrine surveys in 15 counties to document their distribution. We compared our results to those of 2 previous winter-latrine surveys (2001–2002 and 1991–1992) conducted at the same sites. In addition, we used the Program MARK to estimate detection probability and site occupancy, and evaluate the influence of survey-site size on detectability and occupancy, and temperature at the time of the survey on detectability. We located 264 of 278 survey sites that were first surveyed in 1991, but could only survey 211. We detected Swamp Rabbits at 144 of 211 sites in 12 counties yielding a naive occupancy estimate of 0.68. This estimate was higher than reported by both previous surveys: 0.53 in 2001–2002 and 0.40 in 1991–1992. Using occupancy modeling for the 2010–2012 survey, the estimated detection probability was 0.89 (SE = 0.02) and site occupancy was 0.70 (SE = 0.03). As expected, the size of a survey site influenced both detectability of and occupancy by Swamp Rabbits, and temperature influenced detectability. As the size of a site increased, both detectability and occupancy increased, and detectability increased as temperature decreased. Swamp Rabbits continue to occur in 13 counties and occupy fragmented, sometimes isolated blocks of bottomland forested habitat across the Mississippi River Alluvial Basin and along some Ozark Highlands streams.

Legacy sediment, lead, and zinc storage in channel and floodplain deposits of the Big River, Old Lead Belt Mining District, Missouri, USA

The Old Lead Belt of southeastern Missouri was one of the leading producers of Pb ore for more than a century (1869–1972). Large quantities of contaminated mine waste have been, and continue to be, supplied to local streams. This study assessed the magnitude and spatial distribution of mining-contaminated legacy sediment stored in channel and floodplain deposits of the Big River in the Ozark Highlands of southeastern Missouri. Although metal concentrations decline downstream from the mine sources, the channel and floodplain sediments are contaminated above background levels with Pb and Zn along its entire 171-km length below the mine sources. Mean concentrations in floodplain cores >2000mgkg−1 for Pb and >1000mgkg−1 for Zn extend 40–50km downstream from the mining area in association with the supply of fine tailings particles that were easily dispersed downstream in the suspended load. Mean concentrations in channel bed and bar sediments ranging from 1400 to 1700mgkg−1 for Pb extend 30km below the mines, while Zn concentrations of 1000–3000mgkg−1 extend 20km downstream. Coarse dolomite fragments in the 2–16mm channel sediment fraction provide significant storage of Pb and Zn, representing 13–20% of the bulk sediment storage mass in the channel and can contain concentrations of >4000mgkg−1 for Pb and >1000mgkg−1 for Zn. These coarse tailings have been transported a maximum distance of only about 30km from the source over a period of 120years for an average of about 250m/y.About 37% of the Pb and 9% of the Zn that was originally released to the watershed in tailings wastes is still stored in the Big River. A total of ~157millionMg of contaminated sediment is stored along the Big River, with 92% of it located in floodplain deposits that are typically contaminated to depths of 1.5–3.5m. These contaminated sediments store a total of 188,549Mg of Pb and 34,299Mg of Zn, of which 98% of the Pb and 95% of the Zn are stored in floodplain deposits. Most of the metal mass in channel deposits is stored near the mines, with 72% of the Pb and 78% of the Zn occurring in the 25km of channel proximal to the mine source. Although environmental assessments of streams contaminated by mines often focus on evaluating metal concentrations in the geochemically active fine sediment fractions, about 60% of the Pb stored in channels is associated with coarse dolomite tailings fragments deposited in channels within 25km of the mines. The magnitude and basinwide distribution of Pb and Zn storage in legacy floodplain sediments ensures that remobilization by bank erosion will be a continuing problem for water quality far into the future.

Mortality, scarring, and growth in an oak woodland following prescribed fire and commercial thinning in the Ozark Highlands

Oak-dominated (Quercus Spp.) woodlands are commonly thinned and burned in the Ozark Highlands to prevent canopy closure and regenerate desired species, despite a lack of information regarding tree mortality, scarring, and growth in residual stands. Our study compared stand- and tree-level responses after two prescribed burns across four treatments: control, burn, thin, and thin+burn. Results showed that two prescribed fires led to 19% greater cumulative mortality than in unburned stands. In the burn treatment, 19.3% of residual live overstory trees were scarred, compared to 32.4% of trees in the thin+burn treatment. Analysis of scar area revealed that thinning before burning significantly increased the surface area (cm2) of fire scars. In general, trees in the red oak group (Erythrobalanus spp.) had the greatest percentage of scarred trees, followed by the white oak group (Leucobalanus spp.), hickories (Carya spp.), and shortleaf pines (Pinus echinata Mill.). Our data indicate that two fires did not significantly decrease the radial growth of white oaks, except in stands which were thinned prior to prescribed burns. Average percent change in ring-widths (mm) suggest a 1.9% growth decrease in control, 1.4% decrease in burn, 84% increase in thin, and a 35% increase in thin+burn. Covariates such as age, slope, surrounding basal area, canopy openness, and fire scars were analyzed, but tree diameter was the only significant predictor of growth response. Overall, results suggest that effects of prescribed burning are more pronounced in thinned stands as a function of increased fuel loads and fire intensity, causing greater mortality, fire scarring, and reductions in potential growth than fire or thinning alone. This study highlights important tradeoffs between prescribed fire and thinning in oak dominated ecosystems, especially where fire related damages are in potential conflict with other stand objectives.

Vegetation history since the last glacial maximum in the Ozark highlands (USA): A new record from Cupola Pond, Missouri

The timing and drivers of vegetation dynamics and formation of no-analog plant communities during the last deglaciation in the unglaciated southeastern US are poorly understood. We present a multi-proxy record spanning the past 19,800 years from Cupola Pond in the Ozarks Mountains, consisting of replicate high-resolution pollen records, 25 AMS radiocarbon dates, and macrofossil, charcoal, and coprophilous spore analyses. Full-glacial Pinus and Picea forests gave way to no-analog vegetation after 17,400 yr BP, followed by development of Quercus-dominated Holocene forests, with late Holocene rises in Pinus and Nyssa. Vegetation transitions, replicated in different cores, are closely linked to hemispheric climate events. Rising Quercus abundances coincide with increasing Northern Hemisphere temperatures and CO2 at 17,500 yr BP, declining Pinus and Picea at 14,500 yr BP are near the Bølling-Allerød onset, and rapid decline of Fraxinus and rise of Ostrya/Carpinus occur 12,700 yr BP during the Younger Dryas. The Cupola no-analog vegetation record is unusual for its early initiation (17,000 yr BP) and for its three vegetation zones, representing distinct rises of Fraxinus and Ostrya/Carpinus. Sporormiella was absent and sedimentary charcoal abundances were low throughout, suggesting that fire and megaherbivores were not locally important agents of disturbance and turnover. The Cupola record thus highlights the complexity of the late-glacial no-analog communities and suggests direct climatic regulation of their formation and disassembly.