Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Master → Etats Unis → 1979 → Vegetation analysis and ecology of rangelands in northwest Libya, Africa

University of Wyoming (1979)

Vegetation analysis and ecology of rangelands in northwest Libya, Africa

Shawesh, Othman Mohamed

Titre : Vegetation analysis and ecology of rangelands in northwest Libya, Africa

Auteur : Shawesh, Othman Mohamed

Université de soutenance : UNIVERSITY OF WYOMING

Grade : Master of Science (MS) 1979

Résumé
Quantitative description and ecological investigations of semi-arid rangeland in northwestern Libya were initiated in May 1976. A 25,000 ha livestock exclosure near Assa, some 25 km from the Mediterranean seacoast, was utilized. Average annual precipitation is 138 mm, most occurring from October to March. Average annual temperature is about 30°C. Soils are mostly azonal sands with average pH value of 8.51 and mean electrical conductivity of 1.1 millimhos/cm. Vegetation and soil relationships were investigated with permanently established transects for measures of height, diameter and density of perennial plants and percent cover of all live vegetation, and by soil profile sampling for detailed analysis of physical and chemical characteristics. The relatively stable rangeland sites were characterized by the frequent presence of common sagewort, which comprised 33% of all vegetation composition. Helianthemum lippii, Thymelia microphylla , and Echiochilon fruticosum were the most common additional shrubs. The most common grasses were Lygeum sparteum and Koeleria pubescens . Height, diameter and density of all perennial vegetation was observed to have an average of 24.35 cm, 2.83 cm, and 2.72 plants/m2 , respectively. The average percent cover for the entire life form was 7.46%. Statistical analysis showed some variability among transects. Percent cover for the entire vegetation in the anlaysis of variance indicated no significant differences among transects. The relatively low variations among some transects may be attributed to the uniformity of soil electrical conductivity, plant heights and diameter, a long grazing history of the study area, and minimal areas of severe wind erosion affects.

Annonce (WorldCat)

Search Oxford Libraries Online (SOLO)

ProQuest : Dissertations & Theses

Page publiée le 25 mai 2012, mise à jour le 20 novembre 2018