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Questions While mowing is a viable management tool for the maintenance of diversity in grasslands, the suitability of mowing in grasslands with invasion by exotic plants is poorly understood. In this 18-yr study, we investigate the effects of long-term mowing on a tallgrass prairie community invaded by exotic yellow bluestem ( Bothriochloa ischaemum; BOIS). We explore the influence of BOIS on species richness and composition in the face of different mowing treatments as well as monitoring any post-treatment legacy effects. Location Northeast central Oklahoma, US. Methods A total of 144 permanent plots were laid out comprising eight treatments (i.e. all combinations of Mar, Jun and Sept, mows resulting in three single mows, three double mows, one triple mow and an un-mowed control). Plots were mowed 1996-2011 and recovery was monitored through 2014. Repeated mixed model ANOVA, PERMANOVA and principal response curves were employed to analyse species richness and compositional changes from mowing. Correlation was used to explore the effects of BOIS on species richness. Results Mowing resulted in higher species richness relative to the absence of mowing, with the highest levels being sustained in the late season mown plots throughout the study. Once mowing had ceased, early season mown plots declined in species richness down to the same levels as the un-mown plots, concomitant with the sharpest increased cover of BOIS in these plots relative to all other treatments. Overall, we found a strong negative correlation between BOIS cover and species richness. Species dissimilarity was highest between any plot that was mowed and the un-mown controls, as well as between March and September only treatments. Conclusions Our study highlights the potential of mowing in maintaining high species richness. However, the positive response to early season mowing of the exotic yellow bluestem and ensuing negative effect on species richness suggests that BOIS can confound the favourable effects of mowing. We found only minor post-treatment legacy effects, since BOIS strongly re-established in the absence of mowing in all previously mown plots, especially the early season mown plots. Thus, we recommend sustained late season mowing to help control the spread of BOIS and maintain species-rich grasslands. [ABSTRACT FROM AUTHOR]

The article comments on the paper "Plant Species Invasions Along the Latitudinal Gradient in the United States," by Curtis H. Flather, Thomas J. Stohlgren, Catherine Jarnevich, David Barnett, and John Kartesz. The authors assert that the study made by Stohlgren and colleagues has two major deficiencies in which the researchers's data set of county richness values underestimates true county richness and the richness values were incorrectly transformed to report for variation in survey area. They argue the conclusions of the researchers which include the absence of relationship between native plant richness and latitude at the country level and the strongest single predictor of exotic species richness is native species richness.

Maize samples were obtained at two depths [0–30 cm (top sample) and 30–60 cm (bottom sample) from the maize surface] at 19–28 locations from a naturally infested maize storage facility in Wisconsin, USA. Based on identification of insects in stored-maize samples from 13 weekly sampling events, four topics were addressed: (i) the seasonal fluctuation in the insect community; (ii) ordination analysis was conducted to examine the association among insect taxa and to determine their distribution along abiotic and geographic gradients; (iii) the demographic characteristics of insect communities in maize samples with high abundance of either Plodia interpunctella ( Plodia samples) or Sitophilus zeamais ( Sitophilus samples); and (iv) to what extent natural enemies were spatially associated with their prey species. We identified a total of 18 different taxa, composed of adults and larvae of 14 determined species, and others identified to genus, family or order. Insect density was significantly higher in top samples compared to bottom samples, and the insect taxa occurred more frequently in top samples compared to bottom samples. In the ordination analysis, the three explanatory variables accounting for eastern, northern and vertical position of maize samples explained the largest part of the total variance. There was a gradual time trend with some of the insect species mainly occurring early or late in the monitoring period. Moisture content of the maize was the weakest of the significant explanatory variables, while temperature in the grain mass did not explain a significant part of the total variance. Plodia samples and Sitophilus samples had significantly different spatial distribution patterns and had markedly different insect species composition. Plodia samples were characterized by low abundance of all granivores and fungivores, except P. interpunctella. Conversely, Sitophilus samples had high abundance of T. castaneum, A. advena, and C. ferrugineus. Consequently, Sitophilus samples seemed to comprise more diverse insect communities than Plodia samples. Natural enemies were not significantly associated with their most common hosts. In a highly homogeneous habitat (stored maize), we demonstrated that stored-product insect species had significantly different distribution patterns mainly along geographic gradients. Stochasticity of the initial infestation process or interspecific competition are two of the possible explanations for the spatial segregation of stored-product insects, and the spatial segregation of insects on the same trophic level may have profound implications for the understanding of how these ecosystems develop over time and thereby how integrated pest management strategies are implemented to control insect pest populations. [ABSTRACT FROM AUTHOR]

Abstract: Although the relationship between soil reaction and species richness is of great theoretical interest, and has been relatively well studied in temperate latitudes, the southern Great Plains of North America have not received much attention. We analyzed the relationship between species richness and measures of soil reaction (pH, cation exchange capacity, Ca) in 418 10 m x 10 m samples (with nested smaller quadrats) in the Tallgrass Prairie Preserve, Osage County, Oklahoma. We found a negative correlation of richness with soil reaction that is consistent across scales and years in grasslands, with soil calcium exhibiting the strongest relationships. The relationship in woodlands is weakly positive. The proportion of (primarily Eurasian) exotic species is positively related to calcium concentrations in both woodlands and grasslands. Although our results are not inconsistent with species pool hypotheses, critical tests of such hypotheses are operationally difficult. [ABSTRACT FROM AUTHOR]

We studied the effects of windthrow on the understory plant species composition of a pine forest (dominated by Pinus strobus) and an oak forest (dominated by Quercus ellipsoidalis). We recorded the presenceof vascular plant species in randomly located quadrats in the two forests, and in three microsite types associated with tipup mounds (pit, old soil and new soil) in the pine forest at irregular intervals over the course of 14 years. The understories of the two forests remained distinct throughout the study. The frequency of occurrence of a number of forest floor species considerably increased; few species decreased. The disturbance specialists Rubus idaeus and Polygonum cilinode increased in frequency throughout the study in the pine forest, butare beginning to decline in the less disturbed oak forest. Annuals and biennials preferentially colonized the disturbed soil of microsites on tipups, and declined in frequency after about 7 yr. Both forestshave increased in understory species richness, but have not changed substantially in the distribution of growth forms. Despite early differences in species composition, microsite types associated with tipupmounds became more similar through time. Although small in magnitude, there was a directional change in understory composition at both forests, with no apparent sign of a return to pre-disturbance conditions. [ABSTRACT FROM AUTHOR]

We measured tree damage and mortality following a catastrophic windthrow in permanent plots in an oak forest and a pine forest in centralMinnesota. We monitored changes in forest structure and composition over the next fourteen years. Prior to the storm, the oak forest was dominated by Quercus ellipsoidalis, and the pine forest by Pinus strobus. The immediate impacts of the storm were to differentially damageand kill large, early-successional hardwoods and pines. Subsequent recovery was characterized by the growth of late-successional hardwoods. In both forests the disturbance acted to accelerate succession. Ordination of tree species composition confirmed the trend of accelerated succession, and suggested a convergence of composition between thetwo forests. [ABSTRACT FROM AUTHOR]

Abstract: Viruses are most frequently discovered because they cause disease. To expand knowledge of plant-associated viruses beyond these narrow constraints, non-cultivated plants of the Tallgrass Prairie of the United States were systematically surveyed for evidence of viruses. This report discusses putative viruses of the family Secoviridae identified by the survey. Sequence analysis suggests the presence of at least six viruses in the study site, including Bean pod mottle virus, Maize chlorotic dwarf virus, three previously undescribed viruses within the subfamily Comovirinae and one unclassifiable virus. [Copyright &y& Elsevier]

Abstract: This study investigates stable carbon isotopes (δ 13C), opal phytolith assemblages, burnt phytoliths, microscopic charcoal and Sporormiella spores from modern soils and paleosols in Kansas and Oklahoma. Grass and dicot phytoliths in combination with δ 13C are used as proxies for reconstructing the structure of grasslands and woodlands. Burnt grass phytoliths and microscopic charcoal are evaluated as proxies for reconstructing paleofire incidence. Concentrations of the fungal spore Sporormiella are used as a proxy for assessing large herbivore activity. These proxies were tested on various modern grassland communities of the central and southern Great Plains, including areas with bison, cattle, and small herbivores, and areas under different fire frequencies. Opal phytolith assemblages and δ 13C values show that before cal 11ka, C3 grasses and woody plants predominated in areas that today are dominated by C4 grasses. The origin of the shortgrass prairie dates back to about cal 10ka. The origin of the tallgrass prairie, however, is not clear as phytolith data show variable assemblages throughout the Holocene (mixed-grass, tallgrass, and tallgrass–woodland mosaic). Different proxies (burnt phytoliths vs. charcoal) reveal different fire frequencies, but it is apparent that microfossil evidence for fire incidence is closely related to the abundance of woody plants in the landscape. Before cal 12ka, soils show somewhat elevated concentration of Sporormiella, but lower concentrations than the modern high-density bison and cattle grazing areas. Throughout the Holocene, Sporormiella frequencies are low, which suggests lower large ungulate densities and perhaps high mobility. [Copyright &y& Elsevier]

We present novel rearing records of Agromyzidae (Diptera) from throughout the United States. We describe leaf mines or other larval habits for 27 species, plus five others whose identification is tentative, and another five that are identified only to genus due to the absence of male specimens. We review host and distribution data for the known species, reporting 26 new host species records (including the first rearing records for Phytomyza flexuosa Spencer, P. notopleuralis Spencer, and (tentatively identified) Ophiomyia frosti Spencer) and 25 new state records (including the first USA records for P. krygeri Hering, P. thermarum (Griffiths), and (tentatively identified) Liriomyza cracentis Lonsdale). We also describe and provide natural history information for the following 13 new species: Haplopeodes loprestii Eiseman Lonsdale, Liriomyza euphorbivora Eiseman Lonsdale, L. hypopolymnia Eiseman Lonsdale, Melanagromyza arnoglossi Eiseman Lonsdale, M. gentianivora Eiseman Lonsdale, M. hieracii Eiseman Lonsdale, M. rudbeckiae Eiseman Lonsdale, M. urticae Eiseman Lonsdale, M. verbenivora Eiseman Lonsdale, Ophiomyia nabali Eiseman Lonsdale, O. rugula Eiseman Lonsdale, Phytomyza flavilonicera Eiseman Lonsdale, and P. triostevena Eiseman Lonsdale.