. The Canadian field-naturalist. . FiGi RE 5. Distribution oi Shepherdia argeniea in the landscape; Frenchman River valley northeast of Climax, Saskatchewan. (c) Nutrient and water relations: The very wide range of nutrient status in the sites where 5. argentea occurs (Table 1) seems to warrant the conclusion that the level at which major nutrients are present is not critical for the development of the species at any one time. For example, in the areas of stands 12 and 23 (Table 2), in each of which several stands were sampled intensively along transects, levels of each nutrient show a range o
. The Canadian field-naturalist. . FiGi RE 5. Distribution oi Shepherdia argeniea in the landscape; Frenchman River valley northeast of Climax, Saskatchewan. (c) Nutrient and water relations: The very wide range of nutrient status in the sites where 5. argentea occurs (Table 1) seems to warrant the conclusion that the level at which major nutrients are present is not critical for the development of the species at any one time. For example, in the areas of stands 12 and 23 (Table 2), in each of which several stands were sampled intensively along transects, levels of each nutrient show a range of 3:1, or more. At the same time, lowering of the water table through prolonged drought caused stress, shown by wilting of the leaves. Recovery after heavy rains was rapid, however. 5. Plant Communities Shepherdia argentea can occur as solitary shrubs, but more commonly the species forms more or less dense shrub communities in which several woody species are represented. In dry-mesic sites the total number of species may reach seven or eight, and the herbaceous cover is scant. In mesic sites the communities can be well-developed, with as many as ! 0 species of shrubs or small trees represented, and a well-developed ground cover. In wet-mesic sites species of Salix are usually present in the shrub layer, and several wetland herbs appear in the ground cover. There are indications that succession can occur, and eventually results in "gallery forest", in which Populus spp. are dominant. In several areas along the South Saskatchewan River and Red Deer River (Alberta) such forests occur with 5. argentea as an important constituent of the shrub layer. A summary of plant communities with S. argentea. listing the more important species, is presented in Table 3. In the table, abundance is indicated as "cover"—ground cover for herbs, canopy cover for shrubs and trees—as follows: + = < 5%; 1 = 6-20%; 2 = 21-40%; 3 = 41-60%; 4 = 61-80%; 5 = 81-100%. The total numb
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