Estimation of scavenger abundance and distance of attraction to bait

Patterns of arrival, times of first arrival on bait, and instantaneous numbers of animals on bait may be used to estimate abundance and distance of attraction for scavenging species of fish and invertebrates. A simple Gaussian odour plume model, which takes into account the rate of odour production by bait, chemosensory threshold of scavengers, swimming speed of scavengers relative to current velocity, and satiation time, was used. Scavengers are assumed to be stationary and randomly or evenly distributed prior to detecting odour, and presumably respond immediately to odour. Calculations with the model are made with new and published data for various fish and the parameters and assumptions which are critical to the model.     

Variation in resource consumption across a gradient of increasing intra- and interspecific richness

Based on the premise that ecosystems with more species will function at more efficient rates, declining biodiversity is expected to alter important ecosystem functions, goods, and services across the globe. However, applicability of this general hypothesis to genetic or clonal richness in assemblages composed of few species is understudied. This illustrates the need to expand the focus of biodiversity-ecosystem-function experiments across all levels of biological diversity (including genetic). To explore this generality, we manipulated intraspecific (clonal) and interspecific (species) richness of a primary consumer, Daphnia, and measured assemblage feeding rate and total resource consumption. Our results showed that greater clonal richness had no effect on Daphnia feeding, and greater species richness decreased feeding-related effects of Daphnia. This suggests that multiclonal Daphnia assemblages may be no more efficient at consuming resources than monocultures, and that monocultures of Daphnia may consume resources more efficiently than more species-rich assemblages. The inhibitory effect of increasing richness observed in this study resulted from chemical and mechanical interference among some of the Daphnia taxa. This suggests that consumer-mediated ecosystem functions could be reduced when assemblages include taxa equipped with adaptations for interference competition.     

Development of a multilevel Ecological Classification System for the state of Minnesota

The Minnesota Department of Natural Resources (MNDNR) began development of an Ecological Classification System (ECS) in 1991. The ECS is hierarchically organized into six levels following the United States Forest Service structure. The upper four levels are being developed State-wide by an interdisciplinary group from several agencies. Geographic Information Systems approaches are being used to overlay and integrate existing data. The first two levels (Province and Section) have been completed. The third level (Subsection) is nearly completed, and work on the fourth level (Land Type Association (LTA)) started in January 1995. Classification and inventory for the lowest two levels (Ecological Land Type and Ecological Land Type Phase) was cooperatively undertaken on two Land Type Associations within the Chippewa National Forest. A sample set of management interpretations is being developed and tested for the two lower levels. Workshops demonstrating how ECS can be used for natural resource management began in mid-1995 and will continue for several years, as will development of the lower two levels on LTAs beyond the Chippewa National Forest.     

Particle sedimentation in the ocean

Annual particle sedimentation is calculated for various ocean regions using an empirical equation based on studies published prior to 1980. Organic carbon sedimentation is predicted from annual phytoplankton production and water depth. Published data show that organic carbon (as weight percent) in sedimented material decreases with depth and independent of depth increases with phytoplankton production. A matrix of values of organic carbon in settled material over depth for three levels of primary production, generally consistent with published data, is derived and used to calculate dry matter sedimentation over depth for various ocean regions. Ranges of values overlap those reported since 1980 except near continental margins. Resuspension and lateral transport of particulate matter increase sedimentation in these regions above rates predicted for the open ocean.