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Fenceline ecology of four grassland sites in the southern interior of British Columbia. Ndawula-Senyimba, Michael Solomon

Abstract

An ecological study of grassland communities separated by fence lines in the Southern Interior of British Columbia was conducted from spring 1968 to spring 1969. Measurements to compare plant species composition, herbage yield, growth habits and edaphic features on both sides of the fences were taken in the field. Soil organic matter was determined in the laboratory and moisture penetration patterns were demonstrated in the greenhouse. Heavy grazing resulted in the removal of the principal climax caespitose species and their replacement by shrubs, annuals and rhizomatous grasses. There were reductions in the composition, herbage yield and vigor of the caespitose species at all sites following heavy grazing. The success of the increasers under heavy grazing seemed to be favored by possession of rhizomes, presence of unpalatable flowering culms and inflorescences, shortness of tillers and an elaborate means of seed dispersal. The vegetational changes introduced by grazing on the heavily grazed side, resulted in a high level of organic matter in the top 25 cm. of soil, a high soil moisture content and high summer and low winter soil temperatures. The dense vegetation on the lightly grazed side modified both summer and winter soil temperatures. A technique was developed to determine the ability of caespitose grasses to redistribute moisture in the soil. It was demonstrated that aerial parts of Agropyron spicatum collect light rains and concentrate them in the rooting zone of the plant. This phenomenon is likely to be one of the adaptive features which enables caespitose species to dominate arid habitats. It is possible that the great susceptibility of Agropyron spicatum and other caespitose grasses to heavy grazing might be related to soil moisture disturbances introduced by the removal of aerial parts of the plants.

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