Plant succession in saline areas of Saskatchewan
Dodd, Jimmie Dale
Studies have not previously interrelated in detail the vegetation and soils in areas of soluble salt accumulation in North America. The reports which have appeared have been limited to general descriptions and distribution of communities and their general relationship to soil characteristics. Two brief accounts of this nature have considered Canadian vegetation. The surface glacial deposits in the northern Great Plains grassland have favored the development of saline areas by providing a source of salts and in restricting the flow of runoff water out of the area. Evaporation from shallow "kettles" and depressions in glacial lake beds and drainage channels has resulted in the gradual accumulation of soluble material from the till. Approximately 2 percent (over 1,000,000 acres) of the settled areas of Saskatchewan is affected by this process. The concentration of salts is sufficient so that a large part of this is not cultivated or utilized in any way. Elsewhere, lower salinity permits cropping, but with poor results. Some areas are periodically affected by movement of the salt within the soil. The relatively level surface and topographic position of these areas provide a situation where irrigation would be practical in the absence of saline conditions. The purposes of the present study were to relate characteristics of the native vegetation within such areas in Saskatchewan to conditions within the soil and to ascertain the course of parallel changes taking place in soil and vegetation during plant succession. This information is of value in planning for proper land use, particularly with respect to the potential value of marginal areas as irrigated cropland. The area of study was within the major agricultural region of Saskatchewan, south of a line drawn from Melfort to the Alberta Boundary through North Battleford and to the Manitoba Boundary near Moosomin. About 270 saline areas were observed and/or sampled during three summers (1957-59). This enabled a comparison of saline conditions and native vegetation throughout the entire region. A recent classification of salty soil distinguishes between "saline", "nonsaline-nonalkali", "nonsaline-alkali", and "saline-alkali" (U. S. Salinity Laboratory 1954). Saline soils have an electrical conductivity of the saturation extract in excess of four mmhos./cm. This is similar to that of the saline-alkali group, but greater than the nonsaline-nonalkali and nonsaline-alkali. The exchangeable-sodium-percentage of saline and nonsaline-nonalkali soils is less than 15, while it exceeds this value in the nonsaline-alkali and saline-alkali soils. The pH of saline soil, like saline-alkali, is usually 8.5 or less, while that of nonsaline-alkali soil exceeds 8.5. Nonsaline- nonalkali soil ranges from slightly acid to slightly alkaline in reaction. Saline soil is similar to saline-alkali in most respects, except that sodium comprises a higher proportion of the soluble cations in the latter, while sodium and the alkaline-earth carbonates are prominent in the former. Many papers have used the term "alkali" in a broader sense than indieated above. Undoubtedly much of this work relates to saline soil, but it is often difficult to distinguish between the types of salty soils because of lack of uniformity in definition in many previous papers. In the present investigation the term "saline" is used in the narrower sense, as defined above. This investigation was conducted while the author was a graduate student in the Department of Plant Ecology at the University of Saskatchewan. It was made possible through the provision of funds by the Saskatchewan Research Council and the Saskatchewan Agricultural Research Foundation. Plants collected during the investigation were placed in the W. P. Fraser Memorial Herbarium (SASK.) at the University of Saskatchewan. Uncertain identifications were checked by the staff of the herbarium of the Canada Department of Agriculture (DAO) at Ottawa. The author expresses his gratitude to members of the Soil surveys of the Saskatchewan and Canada Departments of Agriculture and the Department of Soil Science, particularly Dr. D. A. Rennie, for advice, criticism, and assistance throughout this study, and for the unrestricted use of equipment. Appreciation is also extended to the Department of Dairy Science for the use of their cryoscope. Help, advice, and criticisms from the members of the Department of Plant Ecology is gratefully acknowledged. Thanks and appreciation are extended to Dr. R. T. Coupland, Head of the Department of Plant Ecology, who provided the opportunity and initiative for this study, and under whose helpful criticism, advice, and supervision this thesis has been prepared.