A simple procedure has been described to provide an estimate of the wear characteristics of a vulcanized polymer by means of a towing device. The present paper describes modifications that have been adopted to increase the efficiency of this procedure and reports the effect of various test conditions that have been explored by statistical methods. Estimates of the wear resistance of various types of rubber in suitable tread recipes are given together with an observed order of rating based upon their response to the severity of the imposed conditions.

Harris, I. W. E. 2013. The response of invertebrate populations in three undisturbed soils in southwestern Ontario, Canada, to variations in local soil properties, seasonal changes, and climate. Canadian Field-Naturalist 127(2): 103-117.Three distinctly different undisturbed mature forested sites at the northern limits of the Carolinian forest system in Lambton County, Ontario, were examined to test the hypothesis that the abundance of each order of soil invertebrates captured is dependent on a unique set of soil properties, seasonal changes, and climate variations. Sixteen independent variables were recorded over five consecutive years. With the exception of rainfall, air temperature, and soil temperature, means of the measured variables differed significantly (P < 0.05) among soils. Twenty-eight taxa of invertebrates were captured, of which acari, Collembola, and Nematoda were most abundant. Only the mean of total abundance and the mean abundance of acari, Nematoda, and Haplotaxida differed significantly (P < 0.05) among soils. Haplotaxida was the only taxon in all three soils found to be influenced significantly (P < 0.05) by seasonal variation. The usual mid-summer minimum in the abundance of Haplotaxida was latest and most clearly defined in the clay soil and earliest and least clearly defined in the sand soil. Regression analysis showed that each site is sufficiently separated in the factor space observed that the abundance of each invertebrate taxon is dependent on different combinations of local variables. The hypothesis was rejected.Key Words: micro-invertebrates; abundance; richness; soil properties; self-organization; climate; seasonal effect; Haplotaxida; Carolinian forest; Ontario; CanadaThe Canadian Field-Naturalist Volume 127, Number 2 April-June 2013of Lake Huron (Figure 1). The underlying rock formation is reported by the geological Survey of Canada (1969) to be part of the Middle Devonian Hamilton group, an argillaceous and crinoidal limestone. In this area, three types of soil, representative of 50% of the county, occur within a radius of 3 km: Brookston clay (Dark grey gleisolic, poorly drained), Brisbane loam (grey Brown Podzolic, imperfectly drained), and Plainfield sand (Regosol, excessively drained) (Soil Survey of Lambton County 1979). The environment is rural, with the nearest urban/industrial centre (Sarnia) 50 km to the southwest. The study area is essentially free of urban/industrial stresses, except for long-range atmospheric deposition. The land varies from 5 to 20 m above mean lake level, including a line of dunes along the lake. a few small creeks drain to the north. Level sites, 50 m 2 , were selected for sampling in forests growing in the above soil types. On the UTM grid, the centres of these sites are as follows: The loam site is near plot number of the Ontario Hardwood Forest Survey (4780990 northing, 424965 easting), as reported by McLaughlin et al. (2000).Tree ring counts showed the soil in each of the sites chosen had not been disturbed for at least 200 years. The loam ...

Richness (the number of invertebrate families/sample site) and density (the number of invertebrates/sq m) of benthic populations in the North Sydenham River were measured and compared with similar estimates for the St. Clair River. Seventeen sample sites were examined from May to October over five consecutive years. At each sample site, particle size distribution of the sediment, sediment temperature, total phosphorous, total nitrogen, total carbon, and water flow rate were measured. Physical and chemical characteristics of the North Sydenham system over the 100 km run examined were less variable than those of the St. Clair. Statistically significant but weak multiple linear correlations were found for richness and density with several of the measured variables. Invertebrate populations in the North Sydenham River were less rich and less dense than those in the downstream reach of the St. Clair and exhibited a different distribution of abundance among the orders of organisms. As in the St. Clair River, some evidence of long term cycling of abundance in several families of invertebrates was found in the North Sydenham.