Species distributional patterns in dune sand areas in the grasslands of Saskatchewan
Gary, Hulett K.
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Dune sand areas present a complex and variable environment for the growth of plants, especially where erosion or deposition has occurred. The instability of the sand surface, along with other physical conditions imposed by the sand particles (moisture relations, hydrology, nutrient status, etc.), is restrictive in its effect on the vegetation and permits the existence of only those species whose adaptive capabilities allow the efficient utilization of the resources of the habitat. This results in a diverse array of vegetation that is often anomalous to that on surrounding finer-textured soils. This, coupled with the severe economic threat posed by sand areas through erosion, has promoted intensive research on dunes in many parts of the world. Stabilization of dunes that are encroaching upon arable land and the improvement of management practices in dune areas utilized for grazing constitute a major portion of this research. Investigations of this nature require an intimate knowledge of the interactions of the vegetational components and their environment, information that can be best utilized when quantitative measurements have been made as to where a particular species grows, where it attains its greatest success and what factors are responsible for its behavior. The purpose of this study was to examine species distributions on dune sand in an attempt to explain the interrelations between the plants and their habitat. Although such information is available in Saskatchewan for soils ranging in texture from clay to sandy loam, there is none concerning dune sand vegetation. This study was initiated in 1959 and continued through 1961. During this time, quantitative data were collected, by various methods, in 101 stands located in two major and two minor study areas selected as representative of the overall dune vegetation in the grasslands of Saskatchewan. One major study area was in the Dundurn sand dunes, approximately 15 miles south of Saskatoon, and the other in the Great Sand Hills, particularly south of Sceptre, Lemsford and Portreeve. The minor study areas, in which only a few stands were located, were near Elbow and north of Webb in Prairie Farm Rehabilitation Administration pastures (Fig. 1). The areal extent of the two major study areas differs considerably, with the Great Sand Hills (Sceptre area) totalling approximately 425 square miles, but the dunes near Dundum cover only 170 square miles. The areas exhibit characteristic dune topography consisting of actively eroding and depositing areas along with a variety of stabilized forms. It should be emphasized that the study areas represent only a sample or the total dune environment and that physiographical phenomena, vegetation and factorial gradients, other than those to be described, may exist. The techniques used in the interpretationÂ· of the data., although not new in theory or practice, are being applied for the first time in vegetation in the Canadian Mixed Prairie. It is hoped that, in addition to the primary purpose expressed, the methods will aid future researchers in quantitative studies concerning northern grassland vegetation.