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Blackwater rivers and streams have stained or tea‐colored water from tannins released by decaying plant matter. Natural conditions in these waters often differ from non‐blackwater systems. For example, the pH and oxygen levels in waters can be very low, but completely natural. We examined an existing USEPA data set and found that blackwaters existed across the contiguous United States but were most common in the east. Water chemistry showed differences between blackwater and non‐blackwater sites, but differences were not consistent across ecoregions making national scale generalizations difficult. Physical habitat data analysis did not show dramatic differences between blackwater and non‐blackwater sites. Blackwater typically arises from streams that drain tannin‐rich bogs/muskeg and wetlands, so as expected blackwater sites had a shorter Euclidean distance to wetlands than non‐blackwater sites and existed in watersheds with a higher percentage of wetland habitat. Blackwaters in Northern and Temperate Plains tended to have higher acid neutralizing capacity, conductivity, and lower True Color; a visual color scale used for water purity. We posit that differences were because Color and Dissolved Organic Carbon at these sites were from buried wetland deposits rather than contemporary wetland habitats. Research needs that may increase our understanding and management of blackwaters include development of an operational definition that includes a classification framework and reference conditions for different blackwater types, identification of stressors and their associated dynamics that negatively impact blackwater systems, and development of data‐driven, consistent, and repeatable assessment methods, including development of targets, protective of unique conditions in blackwater rivers and streams. Plain Language Summary: Blackwater rivers and stream systems have stained or tea‐colored water due to tannins released by decaying plant matter. Although blackwaters exist across the contiguous United States, they are most common in the eastern United States. Beyond their distinct appearance, the chemistry of blackwater systems can be very different from other stream types. For example, the pH and amount of oxygen in the water can be very low, but completely natural. As a result of these and other characteristics, the fish, plants, and animals that live in blackwaters can also be unique. Because of these considerations, management of these systems can be challenging. To address these challenges, U.S. Environmental Protection Agency scientists are studying these systems. One of their early findings is that different types of blackwaters exist across the country. The team has highlighted the need for a classification system to distinguish among these types. Once this system exists, scientists can begin to identify what is required to protect blackwater systems and the services they supply. Key Points: There are a substantial number of blackwater rivers in multiple ecoregions of the United StatesThe water chemistry of blackwater rivers and streams is often very different than that of non‐blackwater rivers and streamsWe explore these differences and identify research needs that would contribute to their management and protection [ABSTRACT FROM AUTHOR]

Candidatus Liberibacter asiaticus (CLas), which causes huanglongbing (HLB) in citrus trees, has a great impact on tree root health, fruit development, and juice quality. HLB-affected trees have a fibrous root density loss of ~30% to 80%, resulting in the limited capacity of citrus trees to uptake nutrients. Therefore, this study was conducted for 3 years to 1) assess the temporal changes in root density as a result of varied fertilization, 2) determine dynamics of HLB with regard to root growth and distribution as a result of varied fertilization for Valencia orange trees, and 3) evaluate the impact of varied fertilization rate and method of fertilization on fruit yield for HLB-affected trees. Macronutrients and micronutrients were applied at varying fertilization rates (0×, 1×, 2×, and 4×, of University of Florida guidelines). Root scans were done using minirhizotrons at 0 to 19.1 cm, 19.1 to 40.7 cm, 38.2 to 59.8 cm, and 57.3 to 78.9 cm soil depths. Results obtained from the study showed that root growth and distribution were greater in 0 to 19.1 cm than 19.1 to 40.7 cm to 57.3 to 78.9 cm soil depths. Thus, root growth decreased (P < 0.0004) with increasing soil depth due to variation in nutrient availability for tree uptake. Increased nutrient availability at occurrence of physiological processes in citrus trees also influenced root growth and distribution, resulting in root growth flushes in the months of Nov to early Feb and Jul to early Aug. Fruit yield was significantly different between treatments in 2 of the 4 years of the study (P 5 0.001 and P 5 0.003), and largely ascribed to soil fertilization of micronutrients compared with foliar. Therefore, at higher fertilization rates, particularly via soil application, nutrient availability was increased, thus promoting root growth and distribution and fruit yield in HLB-affected orange trees. [ABSTRACT FROM AUTHOR]

Rhizosphere interactions are an understudied component of citrus production. This is even more important in Florida flatwood soils, which pose significant challenges in achieving sustainable and effective fruit production due to low natural fertility and organic matter. Citrus growers apply soil amendments, including oak mulch, to ameliorate their soil conditions. Thus, the aim of this research was to evaluate the effects of oak mulch on citrus nutrient uptake, soil characteristics, and rhizosphere composition. The plant material consisted of 'Valencia' sweet orange (Citrus × sinensis) trees grafted on 'US-812' (C. reticulata × C. trifoliata) rootstock. The experiment consisted of two treatments, which included trees treated with oak mulch (300 kg of mulch per plot) and a control. The soil and leaf nutrient contents, soil pH, cation exchange capacity, moisture, temperature, and rhizosphere bacterial compositions were examined over the course of one year (spring and fall 2021). During the spring samplings, the citrus trees treated with oak mulch resulted in significantly greater soil Zn and Mn contents, greater soil moisture, and greater rhizosphere bacterial diversity compared to the control, while during the fall samplings, only a greater soil moisture content was observed in the treated trees. The soil Zn and Mn content detected during the spring samplings correlated with the significant increases in the diversity of the rhizosphere bacterial community composition. Similarly, the reduced rates of leaching and evaporation (at the soil surface) of oak mulch applied to Florida sandy soils likely played a large role in the significant increase in moisture and nutrient retention. [ABSTRACT FROM AUTHOR]

Candidatus Liberibacter asiaticus (CLas), which causes huanglongbing (HLB) in citrus trees, has a great impact on tree root health, fruit development, and juice quality. HLB-affected trees have a fibrous root density loss of ∼30% to 80%, resulting in the limited capacity of citrus trees to uptake nutrients. Therefore, this study was conducted for 3 years to 1) assess the temporal changes in root density as a result of varied fertilization, 2) determine dynamics of HLB with regard to root growth and distribution as a result of varied fertilization for Valencia orange trees, and 3) evaluate the impact of varied fertilization rate and method of fertilization on fruit yield for HLB-affected trees. Macronutrients and micronutrients were applied at varying fertilization rates (0×, 1×, 2×, and 4×, of University of Florida guidelines). Root scans were done using minirhizotrons at 0 to 19.1 cm, 19.1 to 40.7 cm, 38.2 to 59.8 cm, and 57.3 to 78.9 cm soil depths. Results obtained from the study showed that root growth and distribution were greater in 0 to 19.1 cm than 19.1 to 40.7 cm to 57.3 to 78.9 cm soil depths. Thus, root growth decreased (P < 0.0004) with increasing soil depth due to variation in nutrient availability for tree uptake. Increased nutrient availability at occurrence of physiological processes in citrus trees also influenced root growth and distribution, resulting in root growth flushes in the months of Nov to early Feb and Jul to early Aug. Fruit yield was significantly different between treatments in 2 of the 4 years of the study (P = 0.001 and P = 0.003), and largely ascribed to soil fertilization of micronutrients compared with foliar. Therefore, at higher fertilization rates, particularly via soil application, nutrient availability was increased, thus promoting root growth and distribution and fruit yield in HLB-affected orange trees.

Huanglongbing (HLB) disease has caused a severe decline in citrus production globally over the past decade. There is a need for improved nutrient regimens to better manage the productivity of HLB-affected trees, as current guidelines are based on healthy trees. The aim of this study was to evaluate the effects of different fertilizer application methods and rates with different planting densities on HLB-affected citrus root and soil health. Plant material consisted of 'Ray Ruby' (Citrus × paradisi) grapefruit trees grafted on 'Kuharske' citrange (Citrus × sinensis × Citrus trifoliata). The study consisted of 4 foliar fertilizer treatments, which included 0×, 1.5×, 3× and 6× the University of Florida Institute of Food and Agriculture (UF/IFAS) recommended guidelines for B, Mn and Zn. Additionally, 2 ground-applied fertilizer treatments were used, specifically controlled-release fertilizer (CRF1): 12−3−14 + B, Fe, Mn and Zn micronutrients at 1× UF/IFAS recommendation, and (CRF2): 12−3−14 + 2× Mg + 3× B, Fe, Mn and Zn micronutrients, with micronutrients applied as sulfur-coated products. The planting densities implemented were low (300 trees ha−1), medium (440 trees ha−1) and high (975 trees ha−1). The CRF fertilizer resulted in greater soil nutrient concentrations through all of the time sampling points, with significant differences in soil Zn and Mn. Grapefruit treated with ground-applied CRF2 and 3× foliar fertilizers resulted in the greatest bacterial alpha and beta diversity in the rhizosphere. Significantly greater abundances of Rhizobiales and Vicinamibacterales were found in the grapefruit rhizosphere of trees treated with 0× UF/IFAS foliar fertilizer compared to higher doses of foliar fertilizers. [ABSTRACT FROM AUTHOR]

Blackwater rivers and streams are a distinct resource type in multiple ecoregions of the United States, including the Coastal Plains. Given the unique nature of blackwaters, they may not be fully protected if using typical water quality standards. Information provided by State agencies was used to identify specific research needs that would directly enhance current assessment approaches. Protection of blackwater rivers and streams would be aided by (1) development of an operational definition; (2) development of a classification framework that distinguishes among blackwater system types; (3) identification of undisturbed or minimally disturbed blackwater systems; (4) identification of stressors that challenge blackwater condition and resilience; and (5) development of criteria that are more suited to the unique conditions of blackwater rivers and streams. Benefits stemming from addressing these research needs may include identification of sites that are unrecognized as impaired and the re-evaluation of sites that may be erroneously listed as impaired when they are not. This would improve reporting by states for Clean Water Act (CWA) Section 305(b) and, for some states, could represent a significant resource savings by reducing the number of sites on CWA Section 303d lists. [ABSTRACT FROM AUTHOR]

Introduction: The rhizosphere community composition has been shown to provide benefits in nutrient acquisition and plant health. Rhizosphere communities can be heavily influenced by cultural practices in citrus production systems, providing benefits in soil and root health, and plant physiology. Florida growers are implementing new and more sustainable soil management practices, such as using fabric mulch ground covers to improve weed and pest control, while retaining soil moisture. Little is known regarding the influence of these ground covers on the rhizosphere microbial communities of lemon trees, especially under endemic Huanglongbing pressure. Understanding how lemon roots and the rhizosphere microbiome are influenced by fabric mulch ground covers can potentially lead to improved management practices. The aim of this research was to evaluate the effects of fabric mulch ground covers on lemon tree rhizosphere health. Methods: The experiment was conducted in a commercial citrus grove located in Fort Pierce, FL, US. Plant material consisted of four-year old lemon trees cv. 'Meyer' (Citrus limon) grafted on 'sour orange' (Citrus × aurantium) rootstocks. The experiment consisted of two treatments, which included trees grown with fabric mulch ground covers and trees grown without fabric mulch ground covers. Rhizosphere DNA was extracted, sequenced, and analyzed to assess differences in diversity and composition (alpha and beta diversity) of rhizosphere bacteria among treatments. Results and Discussion: Obtained results showed that lemon trees treated with fabric mulch ground covers had significantly greater rhizosphere bacterial diversity when compared to the uncovered trees. The presence of fabric mulch ground covers resulted in significantly greater soil Zn, soil Mn, soil temperatures and pH, potentially contributing towards the significant more diverse rhizosphere bacterial community composition compared than those grown without fabric mulch ground covers. [ABSTRACT FROM AUTHOR]

Rhizosphere interactions are an understudied component of citrus production. This is even more important in Florida flatwood soils, which pose significant challenges in achieving sustainable and effective fruit production due to low natural fertility and organic matter. Citrus growers apply soil amendments, including oak mulch, to ameliorate their soil conditions. Thus, the aim of this research was to evaluate the effects of oak mulch on citrus nutrient uptake, soil characteristics, and rhizosphere composition. The plant material consisted of ‘Valencia’ sweet orange (Citrus × sinensis) trees grafted on ‘US-812’ (C. reticulata × C. trifoliata) rootstock. The experiment consisted of two treatments, which included trees treated with oak mulch (300 kg of mulch per plot) and a control. The soil and leaf nutrient contents, soil pH, cation exchange capacity, moisture, temperature, and rhizosphere bacterial compositions were examined over the course of one year (spring and fall 2021). During the spring samplings, the citrus trees treated with oak mulch resulted in significantly greater soil Zn and Mn contents, greater soil moisture, and greater rhizosphere bacterial diversity compared to the control, while during the fall samplings, only a greater soil moisture content was observed in the treated trees. The soil Zn and Mn content detected during the spring samplings correlated with the significant increases in the diversity of the rhizosphere bacterial community composition. Similarly, the reduced rates of leaching and evaporation (at the soil surface) of oak mulch applied to Florida sandy soils likely played a large role in the significant increase in moisture and nutrient retention.

IntroductionThe rhizosphere community composition has been shown to provide benefits in nutrient acquisition and plant health. Rhizosphere communities can be heavily influenced by cultural practices in citrus production systems, providing benefits in soil and root health, and plant physiology. Florida growers are implementing new and more sustainable soil management practices, such as using fabric mulch ground covers to improve weed and pest control, while retaining soil moisture. Little is known regarding the influence of these ground covers on the rhizosphere microbial communities of lemon trees, especially under endemic Huanglongbing pressure. Understanding how lemon roots and the rhizosphere microbiome are influenced by fabric mulch ground covers can potentially lead to improved management practices. The aim of this research was to evaluate the effects of fabric mulch ground covers on lemon tree rhizosphere health.MethodsThe experiment was conducted in a commercial citrus grove located in Fort Pierce, FL, US. Plant material consisted of four-year old lemon trees cv. ‘Meyer’ (Citrus limon) grafted on ‘sour orange’ (Citrus × aurantium) rootstocks. The experiment consisted of two treatments, which included trees grown with fabric mulch ground covers and trees grown without fabric mulch ground covers. Rhizosphere DNA was extracted, sequenced, and analyzed to assess differences in diversity and composition (alpha and beta diversity) of rhizosphere bacteria among treatments.Results and DiscussionObtained results showed that lemon trees treated with fabric mulch ground covers had significantly greater rhizosphere bacterial diversity when compared to the uncovered trees. The presence of fabric mulch ground covers resulted in significantly greater soil Zn, soil Mn, soil temperatures and pH, potentially contributing towards the significant more diverse rhizosphere bacterial commu nity composition compared than those grown without fabric mulch ground covers.

Dichanthelium caerulescens is documented for the first time in Louisiana, as the result of floristic fieldwork performed in 2019 through 2021. Louisiana records extend the range of D. caerulescens westward by approximately 265 mi (426.5 km) into the Western Gulf Coastal Plain ecoregion. These findings also identify a new habitat, coastal prairie, utilized by D. caerulescens. [ABSTRACT FROM AUTHOR]

Huanglongbing (HLB), which is believed to be caused by the phloem-restricted bacterium Candidatus Liberibacter asiaticus (CLas), has decimated Florida's citrus production. Grapefruit production has declined 75%, mandarin 78%, and sweet orange 52% due to the high sensitivity of commercial scions and rootstocks to the disease. New combinations of scions and hybrid rootstocks may provide better performance than current commercial selections for Florida's fresh citrus production, particularly in the Indian River District. The objective of this study was to evaluate and compare University of Florida rootstocks and other recently released rootstocks grafted with grapefruit, navel orange, and mandarin scions by measuring tree growth and HLB tolerance. Three independent large-scale field trials were established in September 2019 in Fort Pierce, FL, USA. Trial 1 (T1) included 36 rootstocks with 'Ray Ruby' grapefruit as the scion; Trials 2 and 3 (T2 and T3, respectively) included 30 rootstocks with 'Glenn' navel orange F-56-11 and 'UF-950' mandarin as the scion, respectively. Tree canopy volume, trunk diameter, CLas titer, HLB severity index, and leaf nutrient concentrations were evaluated during 2020 and 2021. Significant differences among rootstock-scion combinations were found in each trial for most of the assessed traits. In T2, UFR-15 consistently developed the largest 'Ray Ruby' grapefruit trees during both years. In T3, 'Glenn' navel orange F-56-11 trees were larger on C-22, and US-802. Similarly, US-802 and US-942 generated the largest 'UF-950' mandarin trees. Overall, trees had optimum levels of macro- and micronutrients except for calcium. CLas infection and HLB visual index varied among scion-rootstock combinations, especially during the first year of growth when intensive flushing was produced. Generally, trees grew vigorously with WGFT+50-7 and Willits inducing the lowest HLB symptoms in all evaluations. Production and fruit quality need to be evaluated to determine the suitability of potential scion-rootstock combinations that can confer consistent economical and biological advantages under the current HLB scenario in the Indian River District. [ABSTRACT FROM AUTHOR]

Geographically isolated wetlands provide a critical habitat for pond-breeding amphibians, a taxa of broad conservation concern. Global wetland loss and degradation has made restoration essential for amphibian conservation. Restoration goals typically include recovering the wetlands' physiochemical, hydrological, and ecological functions. However, for pond-breeding amphibians, successful restoration should also result in sustained populations, which is difficult to assess and infrequently reported. In this paper, we review the available evidence that restoration of geographically isolated wetlands promotes pond-breeding amphibian occupancy and population persistence. We provide an overview of restoration practices addressing hydrology, vegetation, and ecological processes within these unique environments and across spatial scales. We then summarize the evidence, and discuss the limitations, for evaluating successful restoration within the context of amphibian conservation across these categories. Finally, we provide recommendations for researchers and practitioners to leverage prior successes and establish systematic data collection and dissemination. Moving restoration of wetlands for amphibian conservation forward will require more robust data collection and reporting. [ABSTRACT FROM AUTHOR]

Huanglongbing (HLB) disease has caused a severe decline in citrus production globally over the past decade. There is a need for improved nutrient regimens to better manage the productivity of HLB-affected trees, as current guidelines are based on healthy trees. The aim of this study was to evaluate the effects of different fertilizer application methods and rates with different planting densities on HLB-affected citrus root and soil health. Plant material consisted of ‘Ray Ruby’ (Citrus × paradisi) grapefruit trees grafted on ‘Kuharske’ citrange (Citrus × sinensis × Citrus trifoliata). The study consisted of 4 foliar fertilizer treatments, which included 0×, 1.5×, 3× and 6× the University of Florida Institute of Food and Agriculture (UF/IFAS) recommended guidelines for B, Mn and Zn. Additionally, 2 ground-applied fertilizer treatments were used, specifically controlled-release fertilizer (CRF1): 12−3−14 + B, Fe, Mn and Zn micronutrients at 1× UF/IFAS recommendation, and (CRF2): 12−3−14 + 2× Mg + 3× B, Fe, Mn and Zn micronutrients, with micronutrients applied as sulfur-coated products. The planting densities implemented were low (300 trees ha−1), medium (440 trees ha−1) and high (975 trees ha−1). The CRF fertilizer resulted in greater soil nutrient concentrations through all of the time sampling points, with significant differences in soil Zn and Mn. Grapefruit treated with ground-applied CRF2 and 3× foliar fertilizers resulted in the greatest bacterial alpha and beta diversity in the rhizosphere. Significantly greater abundances of Rhizobiales and Vicinamibacterales were found in the grapefruit rhizosphere of trees treated with 0× UF/IFAS foliar fertilizer compared to higher doses of foliar fertilizers.

Huanglongbing (HLB), which is believed to be caused by the phloem-restricted bacterium Candidatus Liberibacter asiaticus (CLas), has decimated Florida’s citrus production. Grapefruit production has declined 75%, mandarin 78%, and sweet orange 52% due to the high sensitivity of commercial scions and rootstocks to the disease. New combinations of scions and hybrid rootstocks may provide better performance than current commercial selections for Florida’s fresh citrus production, particularly in the Indian River District. The objective of this study was to evaluate and compare University of Florida rootstocks and other recently released rootstocks grafted with grapefruit, navel orange, and mandarin scions by measuring tree growth and HLB tolerance. Three independent large-scale field trials were established in September 2019 in Fort Pierce, FL, USA. Trial 1 (T1) included 36 rootstocks with ‘Ray Ruby’ grapefruit as the scion; Trials 2 and 3 (T2 and T3, respectively) included 30 rootstocks with ‘Glenn’ navel orange F-56-11 and ‘UF-950’ mandarin as the scion, respectively. Tree canopy volume, trunk diameter, CLas titer, HLB severity index, and leaf nutrient concentrations were evaluated during 2020 and 2021. Significant differences among rootstock-scion combinations were found in each trial for most of the assessed traits. In T2, UFR-15 consistently developed the largest ‘Ray Ruby’ grapefruit trees during both years. In T3, ‘Glenn’ navel orange F-56-11 trees were larger on C-22, and US-802. Similarly, US-802 and US-942 generated the largest ‘UF-950’ mandarin trees. Overall, trees had optimum levels of macro- and micronutrients except for calcium. CLas infection and HLB visual index varied among scion-rootstock combinations, especially during the first year of growth when intensive flushing was produced. Generally, trees grew vigorously with WGFT+50-7 and Willits inducing the lowest HLB symptoms in all evaluations. Production and fruit quality need to be evaluated to determine the suitability of potential scion-rootstock combinations that can confer consistent economical and biological advantages under the current HLB scenario in the Indian River District.

Geographically isolated wetlands provide a critical habitat for pond-breeding amphibians, a taxa of broad conservation concern. Global wetland loss and degradation has made restoration essential for amphibian conservation. Restoration goals typically include recovering the wetlands’ physiochemical, hydrological, and ecological functions. However, for pond-breeding amphibians, successful restoration should also result in sustained populations, which is difficult to assess and infrequently reported. In this paper, we review the available evidence that restoration of geographically isolated wetlands promotes pond-breeding amphibian occupancy and population persistence. We provide an overview of restoration practices addressing hydrology, vegetation, and ecological processes within these unique environments and across spatial scales. We then summarize the evidence, and discuss the limitations, for evaluating successful restoration within the context of amphibian conservation across these categories. Finally, we provide recommendations for researchers and practitioners to leverage prior successes and establish systematic data collection and dissemination. Moving restoration of wetlands for amphibian conservation forward will require more robust data collection and reporting.

This guide is for Extension personnel who may encounter questions from growers about the functioning and accuracy of soil moisture sensors (SMSs) for fruit tree production. The 4-page publication focuses on two types of handheld sensors currently used in Florida for irrigation management of citrus and other trees: the transmission line oscillator (TLO) and time-domain transmissometer (TDT). Written by Eric Herrera, Sandra M. Guzmán, and Eduart Murcia, and published by the UF/IFAS Department of Agricultural and Biological Engineering, February 2021.

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Worldwide, humans are altering the fire regimes (fire‐return intervals, severity, seasonality) of fire‐prone ecosystems, fragmenting natural landscapes, and altering climates. Efforts to restore fire regimes in natural areas are usually guided by fire management plans (FMP) that rely on prescribed burning. Despite the common use of FMPs, limited efforts have gone to assessing vegetative and faunal responses. While some insights into responses to fire from short‐term studies are available, there is less knowledge about FMP outcomes applied over multiple decades. Peninsular Florida hosts many fire‐prone communities including globally threatened Florida scrub. We repeatedly sampled species composition and abundance during a 38‐yr period (1977–2015) at 11 upland stands including wet prairies, flatwoods, and Florida scrub (i.e., oak scrub, rosemary scrub, hickory scrub). A total of 22 fires impacted the stands with individual stands experiencing as few as 2 and up to 11 fires. There was no invasion of non‐native plants following fires and stands showed remarkable ecological resilience with limited change in species composition and modest abundance shifts due to differential recovery rates. Importantly, ecological resilience was not eroded with repeated fire. Species richness, evenness, and diversity were significantly higher at the end vs. beginning of our study, suggesting that current fire regimes are within the range of those with which species evolved. While resprouting shrubs and trees persevered under a range of fire‐return intervals, an obligate‐seeding shrub was adversely impacted by fires more frequent than FMP‐recommended intervals. Several lessons are apparent from our findings. Best practice should: use the full range of fire‐return variation at evolutionarily appropriate intervals; utilize natural fire seasons to the extent possible; compare outcomes and modify prescriptions as necessary to meet FMP goals; give special consideration to burn units with embedded associations of widely differing fire regimes than principal associations in order to maintain diversity of both associations; and account for climate change in FMPs since fire behavior, frequency, and community responses to fire will likely change in the coming decades. Outcomes of FMPs must be carefully evaluated to ensure prescriptions are evolutionarily appropriate and to ameliorate the impacts of altered climates. [ABSTRACT FROM AUTHOR]

Biomass regressions are useful in non-destructively deriving biomass estimates for many applications. We present aboveground biomass regressions for 14 species of resprouting plants found in pyrogenic Florida scrub and related ecosystems. Aboveground biomass was collected from sites within five time-since-fire classes and predicted by plant height, canopy length, canopy width, species, and time-since-fire class. We were generally able to predict 72-95% of biomass variation from the three plant measurements. Regressions without plant width were almost as successful. For six of the species, time-since-fire affected the allometric equations, so we present regressions for specific time-since-fire classes for these species. Species differed markedly in their biomass equations. Within species groups, individual species usually differed but were similar for lyonias. These equations will be useful in summarizing species responses to fire frequency and fire intensity in Florida scrub and related ecosystems. [ABSTRACT FROM AUTHOR]

There has been increasing interest in managing forest stands as uneven-aged structures to promote sustainable harvests as well as maintain ecosystem services. This study provides a framework for simulating conversion of mature even-aged stands to uneven-aged slash pine (Pinus elliottii Engelm.) stands using the USDA Forest Vegetation Simulator (FVS) model. A total of 73 scenarios, representing combinations of two harvest methods (based on either "BDq" and/or "low thinning"), two harvesting cycles (10 or 20 years), three harvest intensities (4.6 or 8.0 or 11.5 m2 ha-1 residual basal areas), and six levels of regeneration (0-2,224 seedlings ha-1) were evaluated for structural diversity, timber production, and carbon (C) stocks over a 100-year period. The BDq harvest approach, which applied selection cutting based on diameter regulation from the first cutting cycle onwards, resulted in higher structural diversity. Scenarios based on low thinning in the first cutting cycle and BDq method from the third cutting cycle onwards tended to result in higher total merchantable timber and C stocks over the entire simulation period, particularly at higher residual basal areas and longer cutting cycles. None of the scenarios maximized all of the three variables simultaneously. Based on the desired objectives, land managers can choose among scenarios presented. The study revealed that regeneration and establishment of as low as 247 seedlings ha-1 can lead to successful conversion and multiple benefits from uneven-aged slash pine stands. [ABSTRACT FROM AUTHOR]

Feral swine are estimated to annually cost hundreds of millions of dollars in economic loss to property and agriculture in the USA, while their ecological consequences remain largely unmeasured. Using submeter-accurate Global Positioning System technology over a multiyear project, we are quantifying in a novel way the spatial and temporal attributes of swine rooting damage within 587 ha of ecologically sensitive wetland plant communities at Avon Park Air Force Range in south-central Florida. We delineated damage polygons from 0.0023 to 4,335 m and were able to document recurrent damage through time at most sites during each assessment. For each polygon, we also estimated the age of damage and assigned to it a severity index, qualities of the rooting in which we detected changes in proportions over time. Spatially explicit damage assessments at fine scales conducted over several years can assist land managers in determining effects of rooting on rare plant populations, and will allow investigators to hypothesize what factors are driving patterns of this disturbance across ecologically sensitive plant communities. [ABSTRACT FROM AUTHOR]

The federally threatened frosted flatwoods salamander, Ambystoma cingulatum, occurs in isolated populations on the coastal plain of northern Florida, Georgia and South Carolina. An earlier phylogeographic study based primarily on mitochondrial DNA (mtDNA) and morphometrics demonstrated that the previously recognized species A. cingulatum contained two cryptic species, and that two distinct mtDNA clades were contained within the newly restricted A. cingulatum. However, salamanders from the northern extent of the species range in South Carolina were not previously available for analysis. Here, we used individuals from a newly discovered South Carolina breeding site to determine whether A. cingulatum from South Carolina are genetically distinct from their more southerly conspecifics. These analyses included the mitochondrial gene studied previously as well as broad geographic sampling of three rapidly evolving nuclear genes that allowed us to further investigate lineage diversification of flatwoods salamanders. The mitochondrial and nuclear results are largely congruent, yielding strong support for two distinct species of flatwoods salamanders and also two lineages within the eastern species. Further, the South Carolina specimens are closely related to other haplotypes found in eastern Georgia and Florida . Our summary of field surveys over the past 20 years indicates that this South Carolina population may be one of only three remaining in the entire Atlantic coastal plain distribution of this rare and declining amphibian species. [ABSTRACT FROM AUTHOR]

Fungi and vascular plant interactions are necessary components of natural community establishment, productivity and degradation. While many fungal species serve as decomposers of organic matter, others have evolved mutualistic or parasitic relationships with vascular plants. This research focused on characterizing associations among macrofungi, vascular plant communities and soils. Ha Ha Tonka State Park is in central Missouri and has a varying landscape with numerous natural community types that provide diverse habitats and microhabitats that are ideally suited to the investigation of fungal, floral and soil associations. Five communities sampled within the park included glades, open woodlands, flatwoods, closed-canopy forests and karst sinks. Permanent 0.01 ha. plots were surveyed in the 2006 and 2007 growing seasons. Surveys of plots and entire communities yielded 249 fungal taxa and approximately 265 floral taxa. Soils were analyzed to help define specific edaphic components of each community and used to associate soil attributes with plant and fungal communities. Forest communities contained the most ectomycorrhizal (ECM) fungi species. Karst sinks and glades had higher soil pH and phosphorus and fewer ectomycorrhizal fungi. Statistical analyses included non-metric multidimensional scaling, multiresponse permutation procedure and indicator species analysis. Indicator species were identified for flatwood, forest and karst communities, but results were inconclusive for glades and open woodlands. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the characteristics of the natural history, seasonality and spatial distribution of the ant Dolichoderus mariae Forel in Florida. The study utilizes the Apalachicola National Forest as a study site wherein the ant colonies are observed including their nest sociometry, rate of oviposition and queen fecundity. The results show that the colony cycle is characterized by polydomy wherein the number of workers increases in summer but decreases in winter.

To assess feasibility of reintroduction of extirpated spotted salamanders (Ambystoma maculatum) in restored flatwoods wetlands, hatching rates were monitored using pond enclosures. Ambystoma maculatum hatching success was compared to that of conspecifics in source ponds and to blue-spotted salamanders (Ambystoma laterale) that had persisted in restored ponds despite habitat degradation. Restored ephemeral ponds with hypoxic conditions had consistent hatching failure for A. maculatum. To isolate effects of dissolved oxygen (DO), laboratory gradients were used to identify levels of DO necessary for A. maculatum and A. laterale hatching success. DO treatments included 0, 2.0, 4.0, 5.0, 6.0, 7.0, and 8.0 mg/l for A. maculatum and 2.0, 4.0, and 6.0 mg/l for A. laterale. Ambystoma laterale hatched across all treatments. Ambystoma maculatum hatching was successful in treatments > 4.0 mg/l. Prescribed burns of dried ponds and selective girdling reduced leaf litter and increased in situ photosynthesis resulting in greater DO. Ambystoma laterale may have persisted in degraded ponds because of differences from A. maculatum in egg structure, and thus oxygen delivery. Land use changes contributing to hypoxia, including changes in forest composition and fire regime, may help explain the loss of A. maculatum from regional assemblages. [ABSTRACT FROM AUTHOR]

Florida citrus groves are typically grown in two regions of the state: flatwoods and ridge. The southern flatwoods citrus area has poorly drained fine textured sands with low organic matter in the shallow root zone. Ridge citrus is located in the northern ridge citrus zone and has fine to coarse textured sands with low water-holding capacity. Two commercial citrus groves, selected from each region, were studied from 15 July 2004 to 14 July 2005. The flatwoods citrus (FC) grove had a grass cover and used drainage ditches to remove excess water from the root zone. The ridge citrus (RC) grove had a bare soil surface with weeds periodically eliminated by tillage. Citrus crop evapotranspiration (ETc) rates at the two citrus groves were measured by the eddy correlation method, and components in the energy balance were also examined and compared. The study period had higher than average rainfall, and as a result, the two locations had similar annual ETc rates (1069 and 1044 mm for RC and FC, respectively). The ETc rates were 59% (RC) and 47% (FC) of the rainfall amounts during the study period. The annual reference crop evapotranspiration (ETo) rates were 1180 ram for RC and 1419 ram for FC, estimated using the standardized reference evapotranspiration equation. The citrus crop coefficients (Kc, ratio of ETc to ETo) were different between the two locations because of differences in latitude, ground cover, and rainfall amounts. The Kc values ranged from 0. 70 between December and March to 1.05 between July and November for RC, and from 0.65 between November and May to 0.85 between June and October for FC. The results are consistent with other Kc values reported from field studies on citrus in both Florida and elsewhere using these and alternate methods. [ABSTRACT FROM AUTHOR]

Abstract: Fire behavior was measured and modeled from eight 1ha experimental plots located in the Francis Marion National Forest, South Carolina, during prescribed burns on February 12 and February 20, 2003. Four of the plots had been subjected to mechanical chipping during 2002 to remove woody understory growth and to reduce large downed woody debris from the aftermath of Hurricane Hugo in 1989. The remaining four (control) plots were left untreated. The burns were low intensity (mean flame length=36.2cm) and slow moving (mean spread rate=1.18mmin−1). Neither flame length nor rate of spread differed significantly between treatments (ANOVA F''s<0.5, P >0.7, d.f.=1,4). Post-burn observations provided somewhat more convincing evidence of treatment effects on fire behavior. According to transect data, only slightly more than half the area in the chip plots burned as compared to upwards of 80% in the burn-only plots. BehavePlus and Hough–Albini (HA) fire models correctly predicted the low intensity, slow moving fires given the observed wind and fuel moisture conditions. Accuracy of BehavePlus predictions depended on the value for fuel height entered in the model. Use of mean fuel height for the fuel depth parameter, as is typically recommended, somewhat overestimated fire hazard in the burn-only plots. However, limiting fuel height to the observed litter depth resulted in roughly accurate predictions. HA predictions for untreated fuels were close to correct even without adjusting fuel depth. When provided with two “high-risk” fuel and fire weather scenarios both models predicted more extreme fire behavior in the untreated fuels. In contrast, chipping appeared to protect against dangerous wildfires as long as fuel heights remained low. Smoke monitoring data from a companion study carried out in the same plots indicated a 60% reduction in smoke particulate production from chipped areas, roughly consistent with predictions of the fire effects model FOFEM. Mechanical chipping is apparently a useful method for limiting fire-hazard and smoke production in long-unburned fuels. However, questions remain concerning the long-term fate of heavy chip fuels and resultant effects on fire and smoke during severe drought. [Copyright &y& Elsevier]