Paul G. Risser

The Sustainable Biosphere Initiative: An Ecological Research Agenda: A Report from the Ecological Society of America

In this document, the Ecological Society of America proposes the Sustainable Biosphere Initiative (SBI), an initiative that focuses on the necessary role of ecological science in the wise management of Earths resources and the maintenance of Earths life support systems. This document is intended as a call to arms for all ecologists, but it will also serve as a means to communicate with individuals in other disciplines with whom ecologists must join forces to address a common predicament. This document focuses primarily on the acquisition of ecological knowledge. It identifies the ecological research programs of highest priority and recommends steps required to pursue research objectives. The document also lays the groundwork for improving the communication and application of ecological knowledge. The SBI proposes three research priorities: global change; biological diversity; and sustainable ecological systems.

The Status of the Science Examining EcotonesA dynamic aspect of landscape is the area of steep gradients between more homogeneous vegetation associations

n the 1930s, scientists and natural resource managers began to consider the concept of ecotones. Ecotones-transitional areas between adjacent ecological systems or, more traditionally, between types of vegetation-were viewed at that time at three somewhat different spatial scales. First, wildlife biologists were aware of the value of local edges or margins (as ecotones are often called in the literature) for habitat, cover, and food for many game and nongame species (Leopold 1933). Second, there was considerable interest in conspicuous transitional areas at tree lines (Griggs 1938). Third, scientists were interested in the broad transitional areas between continental-scale biomes, such as between the Arctic tundra and the boreal forest or between the North American deciduous forest

Ecosystem Analysis of the Tallgrass Prairie: Nitrogen Cycle

Nitrogen cycling in tallgrass prairie was studied by using nitrogen content and concentration data for various ecosystem components on grazed and ungrazed tallgrass prairie in northeast Oklahoma. The seasonal dynamics of N in various plant parts was described, and the annual flow of N among different compartments was calculated. A simulation model was used to study the effect of grazing, fertilization, irrigation, and fire on nitrogen cycling. The results show that grazing, fertilization, and irrigation increase the nitrogen cycling rates. Annual spring fires reduce plant uptake and mineralization of N from plant parts, while mineralization of N from organic matter is increased.

Biomass, Annual Net Primary Production, and Dynamics of Six Mineral Elements in a Post Oak‐Blackjack Oak Forest

A bstract. Dimension analysis was used to estimate biomass and annual net primary production for a post oak-blackjack oak (Quercus stellata-Q. marilandica) forest in central Oklahoma. Concentrations of six mineral elements in various plant tissues were determined and used with biomass and production estimates to calculate the annual cycle of N, P, K, Ca, Mg, and Mn in the forest. Total organic material in the forest is 245,000 kg/ha, of which 1.6% is leaves, 26.4% live branches, 5.9% dead branches, 44.8% trunks, 15.9% roots, 9.6% understory, and 4.4% litter. Annual net primary production is 14,900 kg/ha, distributed as follows: 32.0% leaves, 28.0% twigs and branches, 24.9% trunks, 15.1% roots, and 2.0% understory. Maximum leaf area index was 4.8. Yearly mean litterfall is 5,400 kg/ha and is distinctly biomodal, with peaks in November and March. The biomass contains 1,157 kg/ha N, 101 kg/ha P, 1,258 kg/ha K, 4,549 kg/ha Ca, 311 kg/ha Mg, and 124 kg/ha Mn. Yearly mineral budgets were determined for the six elements. Unusually high values for Ca in the biomass and in the mineral cycle were due to high concentrations of Ca in post oak bark (90,200 tg/g). High annual values for increment of biomass and for retention of mineral elements indicate that the stand has not reached a steady state, a conclusion that is confirmed by observations of stand structure.

Landscape Ecology: State of the Art

Even casual observation reveals that most landscapes are composed of various components. A typical rural landscape might include several agricultural croplands, pastures, woodlands, streams, farmsteads, and roads. Thus, the landscape is heterogeneous, that is, consists of dissimilar or diverse components or elements. In addition to the rather obvious spatial heterogeneity, the landscape is temporally heterogeneous. Ecological processes operate at different time scales. For example, forest trees have life spans of decades, annual crops grow for less than a year, and individual stream insects may last only a few days. It is this mixture of processes consisting of different spatial and temporal scales, all operating as a system, that leads to the ideas of landscape ecology.

Diversity in Tree Species in Oklahoma Upland Forests

Tree—species diversity was measured in 61 Oklahoma upland forest stands. Most stands were dominated by Quercus stellata and Quercus marilandica, but the stands with the greatest diversity were those dominated by other species. There was an inverse relation of dominance concentration (Simpson and McNaughton indexes) to species diversity and the Shannon—Wiener index. The Shannon—Wiener index was positively related to stand basal area and inversely related to stand density. Diversity decreased and concentration of dominance increased along the precipitation gradient from seat to west. Species diversity of Oklahoma forests is generally low to medium compared to southern Appalachian forests. See full-text article at JSTOR

Habitat relationships of wood warblers (Parulidae) in northern central Minnesota

To analyze the habitat relationships of 16 species of wood warblers (Parulidae) breeding in northern central Minnesota, thirteen variables of the structure of the habitat were measured in 207 0.04-ha circular plots located in the territories of breeding males. Cluster analysis of the average habitats of the species identified three groups of species occupying (1) shrub-forest edge (D. magnola, Mniotilta varia, Setophaga ruticilla, V. ruficapilla, Wilsonia canadensis), (2) mature forest (D. coronata, D. fusca, D. pinus, D. virens, Seiurus aurocapillus, Parula americana), and (3) open fields with shrubs (Dendroica pensylvanica, D. petechia, Geothlypis trichas, Oporornis Philadelphia, Vermivora chrysoptera). A reciprocal averaging ordination of the average habitat of each species produced a two-dimensional ordination. The first axis extends from forest vegetation to habitats with few trees and dense ground cover. A second axis separates areas of coniferous forest from those of younger deciduous and mixed forest. A principal components analysis of 199 samples permitted the construction of ellipses that reflect the variability and overlap in the habitat of each species. The axes in these ordinations are multivariate resource axes, but we refrain from interpreting the results in terms of niche width and overlap. Instead we think the distribution of the species and the variation within the habitat of each are mainly attributable to affinities to biotic resources such as food, nest sites, and certain elements of the structure of the vegetation. To infer that these relationships represent the results of interspecific interactions is not justified.

Analyzing long-term changes in vegetation with geographic information system and remotely sensed data

Abstract Geographic information systems and remote sensing techniques are powerful tools in the analysis of long-term changes in vegetation and land use, especially because spatial information from two or more time intervals can be compared more readily than by manual methods. A primary restriction is the paucity of data that has been digitized from earlier periods. The Illinois State Geographic Information System has a number of automated data sets containing land-use information, including original land survey plat maps that show the boundaries of forests, prairies, and wetlands as they existed prior to European colonization in the early 1800s. More recent data include the United States Forest Service inventories of 1948, 1962, and 1985; the United States Geological Survey Land Use Data Analysis; National High Altitude Program photographs of vegetation; and Landsat MSS and TM information. These data can be used to compare vegetation patterns and changes in land use over time and to suggest factors that may have caused or influenced these variations. Profound changes have occurred in the Illinois landscape since European settlement, primarily because of conversion to agricultural use; in certain parts of the state, however, urbanization has been the major factor contributing to changes.

Some Vegetation-Environment Relationships in the Upland Forests of Oklahoma

This study represents a continuation of the series of investigations in the deciduous forest frontier initiated at the University of Oklahoma in 1953. The objectives of the present study were to determine the effect of certain climatic, topographic, soil physical, and soil chemical factors on stand composition and biomass (as measured by basal area) in relation to the four most important upland forest species in the state. Post oak (Quercus stellata Wang.) and blackjack (Q. marilandica Muenchh.) are by far the most important upland tree species in the state, accounting for almost 70%/ of the total basal area (Rice & Penfound 1959). The most important of the minor species are black hickory (Carya texana Buckl.) and black oak (Quercus velutina Lam.), both being widely distributed in the eastern half of the state. Important statewide ecological investigations have been made in Oklahoma by Bruner (1931) and by Rice & Penfound (1959). These studies, however, were more concerned with the characterization of vegetational relationships than with quantitative determination of environmental factors. Studies dealing with vegetation-environment relationships on a quantitative basis have been confined to smaller areas within the state (Rice 1960, 1962, 1965; Buck 1964). Investigations with objectives similar to those of the present study have been made in other areas (McBride 1933; Turner 1937; Lunt 1939; Einspahr & McComb 1951; Pluth & Arneman 1963; Waring & Major 1964). Results of these studies indicate that factors affecting the supply of available moisture usually have the greatest influence on the vegetation of an area.

Long‐Path Ftir Measurement of Atmospheric Trace Gas Concentrations

Extending the ecological knowledge base to larger scales will require new measurement tools. Long—path Fourier—Transform Infrared Spectroscopy (FTIR) is a promising technology because of its ability to measure the concentration of multiple trace gases simultaneously over spatial scales up to 1 km. Detection limits reaching 1μL/KL for numerous gases make this a powerful method with the potential to study spatial patterning of biological processes, fluxes between ecosystems, important processing pathways within terrestrial and aquatic ecosystems, and scale—dependent processing phenomena. Repeated measurements down to the second range add excellent temporal capabilities. This analytical tool, drawing on the latest developments in analytical chemistry, expands the temporal and spatial scales over which ecosystem nutrient cycling energy flow, and biospheric/atmospheric interactions can be studied. See full-text article at JSTOR