The use of individual and nested circular plots for plant ecology studies has increased in recent years. This method is efficient for sampling vegetation but suffers from problems inherent in the use of chain or rope sampling devices to determine the edge of the circular plot boundary (especially in areas of moderate to dense shrub and tree cover). This note describes the construction of a circular plot sampling instrument with improved adjustability, and ease of use over other methods. The instrument is adaptable to a wide variety of field situations. Because it is optically based, the circular plot sampling instrument and prism provide rapid indication of circular plot boundaries anywhere within sight of the plot sampling instrument.
This update of the Bowling Green Study (BGS) of the primary and secondary prevention of atherosclerotic disease (ASD) presents additional information to expand the previously published database. Research methodology has not changed. The expanded database now includes the risk factor data for all BGS patients known to have developed some form of clinical ASD from 4 November 1974 to 1 January 1994. The expanded ASD patient database contains data for 267 male and 248 female patients. Plotting the systolic blood pressure (SBP) versus the cholesterol retention fraction (CRF or [LDL-HDL]/LDL, where LDL is low-density lipoprotein cholesterol and HDL is high-density lipoprotein cholesterol) for all ASD patients for whom this information is known revealed that plots for 82% of male and 75% of female patients lie above the ASD threshold line. If only ASD patients less than 80 years of age are considered, then plots for 85% of male and 78% of female ASD patients lie above the ASD threshold line.
Excision repair has been shown to be the major pathway for repair of damage in DNA caused by cis and trans-diamminedichloridoplatinum(II) (DDP) in Escherichia coli. The effects of limiting excision repair on resistance to DDP was determined using three uvrD mutants of E. coli having different defects in the UvrD protein, DNA helicase II. Excision repair is limited because the UvrD protein function is necessary for catalytic activity of the UvrABC nuclease. The compound ds-DDP was more toxic than trans-DDP in decreasing survival of exposed bacteria and transforming ability of treated plasmid DNA. Repair of chromosomal DNA damaged with DDP was dependent on uvrD function as both compounds were more toxic to uvrD mutants than to isogenic wild-type bacteria. The transforming ability of plasmids treated withtrans-DDP was also decreased further when competent bacteria were deficient in the UvrD gene function, whereas, plasmid DNA treated with cis- DDP had similar transforming ability in bothw#rD mutant and wild-type cells. Repair of ds-DDP modified plasmid DNA in competent bacteria was inefficient and therefore did not require UvrD function.
(1994-09) Williams, Christopher K.; Witmer, Valerie A.; Casey, Megan; Barrett, Gary W.
The present study examined the effects of strip-cropping and harvesting practices on small mammal population dynamics in soybean agroecosystems. Small mammals were live-trapped in four treatments (three replicates each): soybean monoculture, soybean-clover, soybean-buckwheat, and soybean-corn. Peromyscus maniculatus was found in all four treatment types, whereas Mus musculus resided mainly in the soybean-corn treatment. Peromyscus population densities were significantly greater in the soybean monoculture during the week preceding harvest than in the soybean-clover strip-cropped treatment. Peromyscus population densities immediately increased following harvesting practices, then declined. Short-term changes in density were attributed to seed accessibility; long-term changes appeared to be in response to reduced crop cover resulting in increased predation. Populations of Mus were unaffected by harvest practices. Interestingly, more Peromyscus dispersed from strip-cropped treatments than from the monoculture (control) treatment. Female deer mice were found to have larger mean home ranges in the corn strip-cropped treatment than in the monoculture or buckwheat strip-cropped treatment suggesting an impact of spatial resource patterning on small mammal population dynamics.
A five meter sediment core was taken from Old Woman Creek National Estuarine Research Reserve and State Natural Area and Preserve along the western basin of Lake Erie, U.S.A., to determine the historical biogeochemistry of the wetland. Analysis of pollen and sediment chemistry revealed that the area has remained a wetland since ca. 5,500 yr BP, despite changing lake levels. Pollen stratigraphy indicates a distinctive local succession, which has been divided into three zones. Sediments from sometime after glaciation to 5,500 yr BP were characterized by low concentrations of herb pollen; the next zone showed an establishment of hardwood forest vegetation. The modern local vegetation developed after deforestation (about 200 years ago), when sedimentation increased an order of magnitude, phosphorus deposition increased, and the ecosystem changed from a macrophyte dominated wetland to a plankton dominated marsh. After European settlement, the wetland retained its ability to act as a sink and biotic transformer of bioavailable phosphorus; however, abiotic processes seemed to be more important than the biotic transformations that dominated before deforestation.
The germinable seeds in the soil of a relict Ohio prairie were investigated to determine the composition and density of dicots of potential value in restoration. Soil samples were collected from three areas of the prairie with distinctive species compositions: swale, north upland, and south upland. Seed density and species composition were based on seedling emergence over 90 days.