. The Canadian field-naturalist. 618 The Canadian Field-Naturalist Vol. 114. â Yearl n Year 2 50 40 30-- i '""" i 10 + i 0 o E -10 + â o I -20-- -30- -40- -50-- FiGURE 4. Sand movement on an open sand dune between May and October in each of two subsequent yeai^s: (a) sand levels were measured against stakes placed every 50 m on the dune, (b) sand erosion is indicat- ed by negative values and deposition by positive values. dunes, an area of approximately km^, enclosed by the dashed line in Figures 2a and 2b, increased from about 14% in 1948 to 43% in 1974, to 66% in 1994. Veg
. The Canadian field-naturalist. 618 The Canadian Field-Naturalist Vol. 114. â Yearl n Year 2 50 40 30-- i '""" i 10 + i 0 o E -10 + â o I -20-- -30- -40- -50-- FiGURE 4. Sand movement on an open sand dune between May and October in each of two subsequent yeai^s: (a) sand levels were measured against stakes placed every 50 m on the dune, (b) sand erosion is indicat- ed by negative values and deposition by positive values. dunes, an area of approximately km^, enclosed by the dashed line in Figures 2a and 2b, increased from about 14% in 1948 to 43% in 1974, to 66% in 1994. Vegetation composition There were 22 families, 75 genera, and 98 species of vascular plants represented in the four sites. Two- thirds of the species were members of five families; Compositae (), Gramineae (Poaceae) (), Rosaceae (), Leguminosae (), and Cyperaceae (). The amelioration of xeric conditions was reflected in the increasing plant cover and number of species from Sites I to IV (see Appendix). The number of species in the samples changed from 11 in Site I, to 23 in Site II, 35 in Site III, and 75 in Site IV. The mean seasonal cover (May and September for both years) of vegetation increased from < 3% in Site I to 73% in Site IV. Bare ground decreased in a corre- sponding manner. The highest mean cover of any species was less than 10% with marked changes in the mean cover of key species from Site I to Site IV (Table 2). For example, the mean cover of Andropogon gerardi was low in Site I, reached a maximum of 8% in Site II, and gradually decreased in Sites III and IV. Koeleria cristata and Petalostemum candidum also followed this trend reaching maximum cover in Site II. Other species were characteristic of Sites III or IV. Schizachyrium scoparium was absent from Site I, its cover increased from 1% in Site II to 9% in Site III, and decreased to 3% in Site IV. Juniperus hori- zontalis, Bouteloua gracilis, and Stipa spartea were only present in Sites
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