Regional boreal biodiversity peaks at intermediate human disturbance.

The worldwide biodiversity crisis has intensified the need to better understand how biodiversity and human disturbance are related. The 'intermediate disturbance hypothesis' suggests that disturbance regimes generate predictable non-linear patterns in species richness. Evidence often contradicts intermediate disturbance hypothesis at small scales, and is generally lacking at large regional scales. Here, we present the largest extent study of human impacts on boreal plant biodiversity to date. Disturbance extent ranged from 0 to 100% disturbed in vascular plant communities, varying from intact forest to agricultural fields, forestry cut blocks and oil sands. We show for the first time that across a broad region species richness peaked in communities with intermediate anthropogenic disturbance, as predicted by intermediate disturbance hypothesis, even when accounting for many environmental covariates. Intermediate disturbance hypothesis was consistently supported across trees, shrubs, forbs and grasses, with temporary and perpetual disturbances. However, only native species fit this pattern; exotic species richness increased linearly with disturbance.

Spectrum of selection: new approaches to detecting the scale-dependent response to habitat.

Detecting habitat selection depends on the spatial scale of analysis, but multi-scale studies have been limited by the use of a few, spatially variable, hierarchical levels. We developed spatially explicit approaches to quantify selection along a continuum of scales using spatial (coarse-graining) and geostatistical (variogram) pattern analyses at multiple levels of habitat use (seasonal range, travel routes, feeding areas, and microsites). We illustrate these continuum-based approaches by applying them to winter habitat selection by woodland caribou (Rangifer tarandus caribou) using two key habitat components, Cladina lichens and snow depth. We quantified selection as the reduction in variance in used relative to available sites, thus avoiding reliance on correlations between organism and habitat, for which interpretation can be impeded by cross-scale correlations. By consistently selecting favorable habitat features, caribou experienced reduced variance in these features. The degree to which selection was accounted for by the travel route, feeding area, or microsite levels varied across the scale continuum. Caribou selected for Cladina within a 13-km scale domain and selected shallower snow at all scales. Caribou responded most strongly at the dominant scales of patchiness, implicating habitat heterogeneity as an underlying cause of multi-scale habitat selection. These novel approaches enable a spatial understanding of resource selection behavior.

Operant conditioning and behavioral analyses using a minicomputer.

An operant conditioning and data analysis software system was developed for use on a PDP-12A minicomputer. The operant software functions in quasi time-sharing fashion to control and acquire data from any peripheral device that operates in the binary mode. In addition to independently running different experiments in near simultaneous fashion, the program also provides information on the current status of each experiment using a cathode ray-tube display. Response data from each experimental subject is stored on magnetic tape and analyzed, off-line, by the data analysis portion of the software system. A discussion of the operation of this system is given for one possible application: visual discrimination training.

A minicomputer interface for realtime operations: an application to operant conditioning.

A PDP-12 interface was designed, constructed, and tested for realtime imput and output of binary information. Within limits this interface can be used with any peripheral device which operates in the binary mode. In addition to its generality of application the interface features include ease of expansion and low cost. A description of its design and operation is give here is terms of a typical application: the control of behavioral equipment (i.e. "Skinner Boxes") for operant conditioning.

Memory in the Japanese quail: effects of puromycin and acetoxycycloheximide.

Intracerebral injections of puromycin produced memory deficits in naive quail trained to discriminate between red and green stimuli. Puromycin aminonucleoside, acetoxycycloheximide, and saline had no such effect. After a single reversal of the visual cues, naive quail treated with puromycin performed better than control birds. Also, puromycin had no effect on performance when injected into previously trained animals. High doses both of puromycin and acetoxycycloheximide inhibited ribonucleic acid and protein synthesis to a similar extent, while low doses of puromycin inhibited only protein synthesis. Since only puromycin inhibited memory, the basis for its effect appears more likely to be mediated by the action of peptidyl-puromycin rather than by the quantitative inhibition of macromolecular synthesis or by some nonspecific toxic action.