Paleotemperature oscillations in the Middle and Late Miocene of the northeastern Pacific

The paleoclimatic and paleoceanographic history of the Middle and Late Miocene marginal eastern North Pacific as been studied in a north-to-south transect encompassing DSDP Site 173, the Newport Beach surface section, and DSDP Site 470, based on quantitative diatom and planktic foraminiferal analyses. Fourteen cold and 12 warm events that show close agreement with other microfossil studies as well as oxygen isotope records from low-latitude Pacific sites have been identified. Hiatuses are recognized at 7 to 6.5 Ma. 9.8 to 8.5 Ma, and 12 to 11 Ma at the three reference localities, and they correspond to widely recognized deep-sea hiatuses in the World Ocean.

Fire History at the Eastern Great Plains Margin, Missouri River Loess Hills

The purpose of this paper is to provide quantitative fire history information for a geographically unique region, the Loess Hills of northwest Missouri. We sampled 33 bur oak (Quercus macrocarpa Michx.), chinkapin oak (Q. muehlenbergii Engelm.), and black oak (Q. velutina Lam.) trees from the Brickyard Hill Conservation Area in northwest Missouri. The period of tree-ring record ranged in calendar years from 1671 to 2004 and fire-scar dates (n = 97) ranged from 1672 to 1980. Fire intervals for individual trees ranged from 1 to 87 years. The mean fire interval was 6.6 years for the pre-Euro-American settlement period (1672-1820), and 5.2 years for the entire record (1672-1980). A period of more frequent fire (mean fire interval = 1.6 for 1825 to 1850) coincided with Euro-American settlement of the area. The average percentage of trees scarred at the site was 16.8%, or about 1 in 7 trees sampled per fire. No significant relationship between fire years and drought conditions was found; however, events prior to 1820 may have been associated with wet to dry mode transitions.

Distribution of Dioecious Eastern Red Cedar (Juniperus virginiana) along an Environmental Gradient in Ogallala, NE.

Abstract The purpose of this research was to study the sex distribution and energy allocation of dioecious Eastern Red Cedars (Juniperus virginiana) along an environmental resource gradient. The trees surveyed were growing in a canyon located at the University of Nebraska’s Cedar Point Biological Research Station in Ogallala, Nebraska. Due to the geography of this canyon, environmental factors necessary for plant growth should vary depending on the tree’s location within the canyon. These factors include water availability, sun exposure, ground slope, and soil nitrogen content, all of which are necessary for carbon acquisition. Juniperus virginiana is a dioecious conifer. Dioecious plants maintain male and female reproductive structures on separate individuals. Therefore, proximal spatial location is essential for pollination and successful reproduction. Typically female reproductive structures are more costly and require a greater investment of carbon and nitrogen. For this reason, growth, survival and successful reproduction are more likely to be limited by environmental resources for females than for male individuals. If this is true for Juniperus virginiana, females should be located in more nutrient and water rich areas than males. This also assumes that females can not be reproductively successful in areas of poor environmental quality. Therefore, reproductive males should be more likely to inhabit environments with relatively lower resource availability than females. Whether the environment affects sexual determination or just limits survival of different sexes is still relatively unknown. In order to view distribution trends along the environmental gradient, the position of the tree in the canyon transect was compared to its sex. Any trend in sex should correspond with varying environmental factors in the canyon, ie: sunlight availability, aspect, and ground slope. The individuals’ allocation to growth and reproduction was quantified first by comparing trunk diameter at six inches above ground to sex and location of the tree. The feature of energy allocation was further substantiated by comparing carbon and nitrogen content in tree leaf tissue and soil to location and sex of each individual. Carbon and nitrogen in soil indicate essential nutrient availability to the individual, while C and N in leaf tissue indicate nutrient limitation experienced by the tree. At the conclusion of this experiment, there is modest support that survival and fecundity of females demands environments relatively richer in nutrients, than needed by males to survive and be reproductively active. Side of the canyon appeared to have an influence on diameter of trees, frequency of sex and carbon and nitrogen leaf content. While this information indicated possible trends in the relation of sex to nutrient availability, most of the environmental variables presumed responsible for the sex distribution bias differed minutely and may not have been biologically significant to tree growth.

Correlation of the middle Eocene Kellogg Shale of northern California

The Kellogg Shale of northern California has traditionally been considered to be late Eocene in age on the basis of benthic foraminifer, radiolarian, and diatom correlations. The 30-m-thick Kellogg section exposed west of Byron, California, however, contains middle Eocene planktonic foraminifers (Zone P12), coccoliths (Subzones CP13c and CP14a), silicoflagellates (Dictyocha hexacantha Zone), and diatoms. Quantitative studies of the silicoflagellates and diatoms show a general cooling trend through the section which is consistent with paleoclimatic trends for this part of the middle Eocene (ca. 42-45 Ma) from elsewhere in the world. Seven new silicoflagellate taxa (Corbisema angularis. C, exilis, C, hastate miranda, C. inermis ballantina, C. regina, Dictyocha byronalis, Naviculopsis Americana) and one new coccolithophorid species (Helicosphaera neolophota) are described.

SEASONAL, HABITAT AND SEX-SPECIFIC PATTERNS OF FOOD UTILIZATION BY RED-WINGED BLACKBIRDS (Agelaius phoeniceous) IN EASTERN ONTARIO AND THEIR ECONOMIC IMPORTANCE

Crop depredation by red-winged blackbirds (Agelaius phoeniceus) causes serious economic losses to agricultural crops each year in both Canada and the United States. The concentration of vulnerable, monocultural crops, particularly corn, during periods when large flocks of blackbirds congregate in roosting areas prior to migration has invariably led to heavy feeding pressure (Stone et al., 1972; Wiens and Dyer, 1975; Tyler et al., 1978). Efforts to reduce damage levels by mechanical and chemical dispersal agents have been largely unsuccessful, at least in terms of a long-term solution to the problem. Recently, the lethal control of blackbird populations using surfactants has been proposed. However, the potential repercussions of the removal of substantial numbers of birds from northern breeding areas are virtually unknown (Robertson et al., 1978). Much of the research dealing with the feeding ecology of red-winged blackbirds has been limited to fall and winter periods when large aggregations of birds are actively involved in crop depredation (Goddad, 1969; Williams, 1976; Dolbeer et al., 1978) or pose a potential health hazard (Monroe and Cronholm, 1976). However, what is not known is the degree to which the removal of deleterious weed seed and insect pests cited in several studies (Bird and Smith, 1964; Mott et al., 1972; Robertson et al., 1978) might be of potential value to agriculture. The issue of whether the benefits derived from redwing foraging compensate for the negative aspects associated with crop depredation and health hazards remains largely unresolved. The present study attempted to evaluate the pest status of this species using diet information derived from food habits analysis conducted during the residency of red- winged blackbirds in a northern breeding area. By determining how the feeding ecology of red-winged blackbirds varies on a seasonal basis, among different breeding habitats and between sexes, we hoped to determine more realistically which segments of the population might be responsible for the greatest benefits or detriments and, thereby, more accurately evaluate the economic impact of the species as a whole. To achieve this aim, the study provides an accurate description of the common insects and weed pests utilized by redwings. By determining the relative proportions of those items known to be detrimental, we hoped to illustrate, at least qualitatively, the degree to which redwing foraging is comprised of both beneficial and harmful components.