ABSTRACT Within the study of aquatic invasive species, small aquatic ecosystems are often neglected, despite representing most global freshwater bodies. This study uses community composition and environmental and geographic factors to explain the occurrence of invasive species in small lakes in the southeastern United States. Four invasive species widespread in the southeastern United States were selected as the focus of this study: Alternanthera philoxeroides, Cyperus blepharoleptos, Panicum repens, and Triadica sebifera. The aquatic plant communities of the lakes were surveyed using littoral zone point sampling. Generalized linear models for each species were fit with the probability of occurrence (Pocc) as the response variable and Secchi depth, plant species diversity (α‐diversity), point richness, perimeter, latitude, and longitude as potential predictors; all predictors were subjected to model selection to define the best‐fit models. All best‐fit models were strongly predictive with area under the receiver operating characteristic curve values > 0.80. Plant species diversity was positively correlated with Pocc of A. philoxeroides, P. repens, and T. sebifera. Latitude was negatively correlated with Pocc of P. repens and T. sebifera. Perimeter was negatively related to Pocc of A. philoxeroides. Secchi depth was negatively related to the Pocc of C. blepharoleptos. Although plant species diversity and latitude were most commonly predictive, Pocc was usually explained by multiple predictors, suggesting that these relationships are best explained with multiple environmental factors.

The ability to predict the impact of abiotic stressors on plant assemblage characteristics during habitat restoration is critical in the success of targeted restoration efforts. In an effort to determine wetland plant responses to common agricultural stressors, we seeded 75 mesocosms with soil collected from three restored wetlands in the Mississippi River Alluvial Valley. These mesocosms were subjected to four different combinations of nitrogen and sediment addition and monitored for two growing seasons. Resulting assemblages showed strong effects from site of origin with weaker effects of imposed treatments on assemblage composition. In contrast to species composition, summary metrics of assemblage quality (e.g., richness and diversity) were negatively affected by increased nitrogen and sediment levels, vs. controls. Over time, assemblage phylogenetic relatedness became more clustered, indicating the importance of abiotic filtering on wetland plant assemblages in agricultural landscapes. Our results indicate that agriculturally derived stressors can exert a filtering effect on plant assemblages, impact their perceived quality, and lessen the importance of soil site of origin in restored wetlands in agricultural landscapes.

Aim Humans influence species distributions by modifying the environment and by dispersing species beyond their natural ranges. Populations of species that have established in disjunct regions of the world may exhibit trait differentiation from native populations due to founder effects and adaptations to selection pressures in each distributional region. We compared multiple native, expansive and introduced populations of a single species across the world, considering the influence of environmental stressors and transgenerational effects. Location United States Gulf and Atlantic coasts, United States interior, European Atlantic and Mediterranean coasts, east coast of Australia. Taxon Baccharis halimifolia L. (eastern baccharis). Methods We monitored seed germination, seedling emergence, survival and early growth in a common garden experiment, conducted with over 18,200 seeds from 80 populations. We also evaluated the influence of environmental stress and maternal traits on progeny performance. Results Introduced European Atlantic populations had faster germination and early growth than native populations. However, this was not the case for the more recently naturalized European Mediterranean populations. Introduced Australian populations grew faster than native populations in non-saline environments but had lower survival in saline conditions commonly encountered in the native range. Similarly, expansive inland US populations germinated faster than coastal native populations in non-saline environments but grew and germinated more slowly in saline environments. Maternal inflorescence and plant size were positively related with seed germination and seedling survival, whereas flower abundance was positively correlated with seedling early growth and survival. However, maternal traits explained a much lower fraction of the total variation in early demographic stages of B. halimifolia than did distributional range. Main conclusions Phenotypic differentiation could allow B. halimifolia to adapt to different biotic and abiotic selection pressures found in each distributional range, potentially contributing to its success in introduced and expansive ranges.

In early successional stages, seedlings serve as a link between past and future wetland plant assemblages. Our objectives were to 1) enumerate seedling density in soil exposed to various hydrologic treatments 2) determine similarities between standing vegetation, germinated seedlings, and early successional stage assemblages, and 3) better understand effects of landscape-level factors on overall wetland seedling density. Soil samples were collected and standing vegetation characterized from 12 restored and three non-managed wetlands in the Mississippi River Alluvial Valley (MAV). Seedling germination was observed in a greenhouse experiment, while early-stage plant assembly was followed in outdoor mesocosms. Hydrology significantly affected seedling density, with constantly moist treatments increasing seedling germination above that observed in fluctuating or continually inundated treatments. Standing vegetation in MAV wetlands differed from germinated seedlings; however, germinated seedlings were similar in terms of structure and identity to early successional mesocosm assemblages, indicating close linkages of these two vegetation stages. When landscape-level factors were examined, we found that wetland size was positively correlated, and surrounding land use and watershed nitrogen (N) loading negatively correlated with seedling numbers. Thus, seedling dynamics were affected by factors internal and external to wetlands, necessitating landscape-scale perspectives when making management decisions, even for individual wetlands.

While dissolved organic matter (DOM) is an important indicator of water quality, land use and land cover (LULC) of watersheds define the source, quality, and quantity of DOM delivered to a waterbody. This study examined the influence of various LULC classes in the spatial distribution of DOM in 41 lakes across the state of Mississippi. To scale the influence of LULC classes on DOM distribution, we have classified 41 lakes into five clusters based on DOM compositions determined by parallel factor analysis. Four major DOM compositions including terrestrial humic-like (C1), microbial humic-like (C2), soil-derived humic-like (C3), and tryptophan-like or tyrosine like (C4) components were identified. Higher amounts of terrestrial humic-like and soil-derived humic-like DOM compositions were observed in lakes within watersheds dominated by forested, barren, wetlands, or agricultural areas with exposed unconsolidated soil. Higher amounts of microbial humic-like composition were observed in lakes surrounded by hay/pasture, rangeland, and urbanized areas. Additionally, protein-like DOM and ammonia were more enriched in larger lakes, indicating the influences of photochemical reactions. High amounts of forested areas and higher concentrations of terrestrial humic-like DOM composition were identified in all lakes suggesting forested areas in the watershed as the principal source of DOM in Mississippi lakes.

Soils from four sites distributed along an elevation gradient from marsh to coastal forest in a wetland bordering the Gulf of Mexico were sampled over a 16-months period. In addition to measuring a suite of environmental conditions, terminal restriction fragment length polymorphism analyses of the resident bacterial communities were performed. Wetland soil bacterial communities varied across both space and time, with all measured variables (temperature, pH, percentage of soil organic matter, salinity, and concentrations of sulfide, NH4+, NO3−, and soluble reactive phosphorus) showing significant site by time interactions. Analyses of bacterial communities showed both marsh zones (Spartina and Cladium) supported similar communities, as did the ecotone and coastal forest. Bacterial communities within coastal forest soils were significantly different than those within marsh soils, and the ecotone communities were significantly different from the Spartina marsh soil. Temperature and pH were the most influential environmental factors impacting bacterial community composition but no predictable patterns were identified, suggesting that community changes are likely the result of intrinsic factors that are affected by local-scale processes. The dynamic nature of the physiochemical variables within wetlands suggests that more work is needed to determine potential interactive effects on bacterial community structure.

Canebrakes in the southeastern United States form a unique ecosystem composed of monotypic stands of the cane species Arundinaria gigantea Michaux within bottomland hardwood forests. Since European settlement, canebrakes have been reduced to less than 2% of their historic range and are considered a critically endangered ecosystem. Despite efforts to restore bottomland hardwood forests to the landscape, current practices have yet to address restoration strategies for canebrakes. This paper synthesizes current understanding of abiotic and biotic factors limiting canebrake reestablishment within bottomland hardwood forest complexes. Consideration is given to the effects of hydrology, landscape and biogeographic factors, disturbance, cane reproductive history, growth patterns, and herbivory on canebrake establishment and persistence. While there is no single factor controlling the distribution and abundance of canebrakes, it is reasonable to believe abiotic factors have a greater impact on the establishment of canebrake systems than biotic factors. Once ecosystem hydrology, topography, and disturbance regimes are restored, biotic factors may have a greater limiting effect on canebrake reestablishment. Herbivory is particularly detrimental to canebrake formation and maintenance by decreasing cane density and cover, selectively removing root stock, and facilitating colonization of areas formerly occupied by cane. This review concludes that under current restoration and management practices of restored bottomland hardwood forests, widespread canebrakes seem unlikely to reestablish.

Excess nutrient loading from agricultural landscapes contributes to downstream water quality degradation. To mitigate these issues, agricultural drainage ditches have recently gained attention as potential sites for nutrient reduction. We examined the effects of vegetation and hydrology on oxidation-reduction (redox) potential. Testing occurred in an agricultural drainage ditch fitted with weirs in the summer of 2012. Redox potential was recorded using continuous automated data loggers and analyzed using both frequentist and Bayesian methods. Significant difference was found when analyzing redox potential response to vegetation (t = −1.75, P = 0.08, df = 9754) and hydrology treatments (t = 7.51, P < 0.001, df = 9754) in a frequentist manner. Vegetation and hydrologic treatments were significant when analyzed using Bayesian methods; however, the interactions of the two terms had the greatest posterior weights. This study suggests that the innovative use of vegetation and controlled drainage can affect Eh, in particular Eh heterogeneity within ditch systems. Results obtained by analyzing these data in both a frequentist and Bayesian methods were similar in terms significance and magnitude. However, Bayesian methods, and their ability to incorporate prior information into a management framework, may be better suited for systems where previous information can be incorporated into analyses.

Water quality degradation from excessive fertilizer use and runoff is a worldwide problem. While this degradation impacts wetlands, these systems can also be a vehicle for water quality improvement. Restoration of wetlands in agricultural landscapes has recently increased, but little work has evaluated the relationship of plant assemblages and water quality parameters in restored, non-treatment wetlands. This study examines the impact of self-designed wetland plant assemblages on nitrogen and sediment dynamics. Thirty mesocosms were seeded with soil from restored wetlands and allowed to develop from the seed bank to emergent assemblages. During the 2015 growing season (seven to nine months after establishment), these assemblages were exposed to treatment loads of nitrogen and sediment, common stressors to wetlands in agricultural landscapes. Water samples were taken up to five days post-treatment in July and September to quantify interactions between the stressors and plant assemblages. Analyses showed plant assemblage identify was not structured by treatment, but by the site of soil origin. Treatment removal rates were influenced by total amount of the stressor present, with nitrogen removal rates being higher, in relative terms, in low nitrogen amended treatments. Additionally, plant quality, not quantity, was linked to nitrogen and sediment loss rates, and over time, elevated nitrogen and sediment loads were associated with decreased plant assemblage quality. This study demonstrates the ability of plants from restored wetlands to affect nutrient and sediment dynamics, with three significantly differing plant assemblages all exhibiting substantial nutrient and sediment reduction capacity. Nevertheless, we also found that in a relatively short time (seven to nine months) common stressors in agricultural settings can significantly impact wetland plant assemblage quality, and that this may be linked to a reduced capacity for nutrient and sediment removal.

Reduction-oxidation or redox potential is typically collected by measuring redox at a single time interval and returning to the electrode to collect subsequent intervals to generate a temporal gradient of changes in redox. Typically, intervals between sampling are on the scale of hours, days, and weeks, rather than one, five, or 20 minutes due to logistical constraints of collection. These constraints are labor (i.e., constant measurements 24/7) and technology driven (i.e., construction of a unit that is capable of accurately and precisely measuring redox at fine temporal scales). This study describes a continuous, short interval redox data logger that is capable of measuring ±10 mV at minute time intervals. To ensure quality assured and quality controlled data, the redox unit was subjected to tiered verification procedures that documented hardware and probe sensitivity to changes in voltage. Furthermore, the setup was laboratory tested against known mV redox solutions (Zobel, 225 mV), flooded in soil medium over 48 h, and subjected to drying over 48 h. Results highlight and verify the accuracy and precision of the redox probes and hardware for measuring stability and changes in redox. Future research will investigate field operations of redox probes and create spatially and temporally detailed investigations to changes in redox as a result of vegetation, flooding, and management.

Communal winter roosts of American Crows (Corms brachyrhynchos) often occur in urban areas and may number in the thousands of individuals. We documented the distribution of urban roosts of American Crows in central Ohio and, on 12 January 2010, we observed a roost of 2,500 individuals with similar to 250-300 birds roosting on the ground. The ground roosting birds remained stationary for the entire observation period of similar to 45 min indicating this location was not a stopover site. This behavior may increase thermoregulatory benefits during cold nights assuming decreased predation threats in urban environments. We suggest urban ground roosting behavior by crows may be adaptive in colder environments. Received 16 February 2010. Accepted 11 November 2010.