Forb Diversity Research Articles

Plant diversity in four chalk grassland sites with different aspects

Plant diversity and its components was studied on four chalk grassland sites in southeast England over a fourteen-month period. The sites were almost adjacent, and each faced one of the major compass points, N, S, E and W. Aboveground vegetation was recorded at monthly intervals by cover repetition, using a point quadrat technique. Seasonal patterns in the development of leaf area, bare ground, number of species present and diversity were similar on all sites. The N and W facing slopes and the S and E facing slopes resembled each other in several characteristics, while these two pairs of slopes differed markedly from each other. Thus, (i) there were more grasses but fewer forbs on the N and W slopes, (ii) overall diversity and forb diversity were lower on the N and W slopes but grass diversity was higher, (iii) equitability was lower on the N and W slopes, (iv) percentage similarity of begetation present was high when the N slope was compared with the W and when the S slope was compared with the E; other comparisons gave lower percentage similarity. It is proposed that the greater abundance of Carex flacca on the N and W slopes is important in causing these differences, and that it results in lower diversity on these slopes by occupying part of the habitat of the species-rich forb community which occurs on the S and E slopes. Dominance-diversity curves range from lognormal to geometric in form; some interpretation of changes they display can be made by assuming that the community is in a non-equilibrium state caused by seasonal environmental fluctuations each winter.

Effects of Grazing on Lizard Abundance and Diversity in Western Arizona

Effects of Grazing on Lizard Abundance and Diversity in Western Arizona

High elevation vegetation of the Enchantment Lakes Basin, Washington

The vegetation of the Enchantment Lakes Basin, which is located at and above timberline on the slopes of Mount Stuart, Washington, was examined by classification and ordination methods. A vegetation map relates the 21 recognized community types to physiographic and topographic features. Vegetation was divided into plots with and without trees. The 11 forested communities include those dominated by Larix lyallii and Cassiope mertensiana on moist slopes, L. lyallii and Phyllodoce glanduliflora on steep north-facing slopes, Abies lasiocarpa and Vaccinium inyrtillus on low elevation, moist sites, and several communities dominated by Pinus albicaulis on dry, exposed slopes. The 10 alpine communities include dry fell-fields dominated by Lupinus lepidus with a variety of forbs, communities dominated by Cassiope mertensiana and Phyllodoce glanduliflora and by P. empetriformis, and lush and wet meadow communities dominated by Lupinus polyphyllus and Carex nigricans. These communities are related to those identified by other workers in the Pacific Northwest. Keys to the vegetation of this area are presented. Indirect gradient analysis using reciprocal averaging revealed both vegetation and species patterns. In the subalpine, moisture appears to be the dominant operational gradient, while inferred temperature is a secondary factor. In the alpine vegetation, a combined gradient of moisture and exposure is indicated by reciprocal averaging. Special ordinations derived from reciprocal averaging reflect these interpretations and identify indicator species for particular habitats in both subalpine and alpine. The patterns are summarized with a mosaic diagram. The use of multivariate methods provided means to summarize primary survey data quickly and efficiently. The pattterns thus revealed are comparable to other studies in the Pacific Northwest and thus engender confidence in the use of indirect gradient analysis as a valuable tool for primary survey in these ecosystems. A vegetation map, keys to vegetation types, community and species patterns, and the relationship between classifications and ordinations emerged from this study.

The Effect of Nitrogen, Phosphorus and Potassium Fertilization on Chemical Content of Sheep Diets

The Effect of Nitrogen, Phosphorus and Potassium Fertilization on Chemical Content of Sheep Diets

Observations on the Biology of Gunnison's Prairie Dog in Central Colorado

A study was conducted from July 1965 to September 1966 on the biology of Gunnison's prairie dog (Cynomys gunnisoni gun- nisoni) in South Park, Park Co., Colorado. Prairie dogs within the colony were loosely organized into clans with adult females playing the major role in caring for the young and! warning of danger. Clan bound- aries were not patrolled or defended by clan members, but individual burrows, burrow systems or food supplies were protected by individual animals. Little aggression was observed within the clans but members of different clans would engage in disputes when they encountered each other in the common feeding areas. Females had a high ratio of suc- cessful pregnancies or uterine implantation sites, but mortality caused by a plague (Yersinia pestis) epizootic resulted in the extinction of the main study colony by the spring of 1967. Mean weights of adult males were significantly higher than weights of adult females. Weights of pups in- creased during the first summer so that by September a few individuals were as large as smaller adults. Immigration and emigration were not important in the colony and the only known successful predators were badgers and red-tailed hawks. Tactile, visual and vocal communication was important in the colony, but in general social behavior was not as well developed as in black-tailed prairie dogs. Prairie dogs were diur- nal with two periods of maximum surface activity. Gunnison's prairie dogs completely terminated surface activity for 7 months during the cold seasons of the year, with pups being the last animals to hibernate. Gun- nison's prairie dogs did not work or shape their mounds and their activ- ity had little visible impact on their environment. Most of the time the animals spent aboveground was occupied in eating or searching for food. Grasses were the preferred foods but a variety of forbs were also utilized.