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Accueil du site → Doctorat → États-Unis → 2009 → Invasive Lehmann lovegrass (Eragrostis lehmanniana) in Chihuahua, Mexico : Consequences of invasion

OKLAHOMA STATE UNIVERSITY (2009)

Invasive Lehmann lovegrass (Eragrostis lehmanniana) in Chihuahua, Mexico : Consequences of invasion

Sanchez Munoz, Alfonso de Jesus

Titre : Invasive Lehmann lovegrass (Eragrostis lehmanniana) in Chihuahua, Mexico : Consequences of invasion

Auteur : Sanchez Munoz, Alfonso de Jesus

Université de soutenance : OKLAHOMA STATE UNIVERSITY

Grade : Doctor of Philosophy (PhD) 2009

Résumé
Plant community dynamics, including vegetation changes in cover (%), species richness, diversity, evenness and similarity indices were assessed in a bunchgrass type rangeland in central Chihuahua, Mexico over a 20 year period (1985-2005). The goal of this study was to quantify the progressive invasion of Lehmann lovegrass (Eragrostis lehmanniana) from its original source of introduction in the mid-1960’s. Vegetation was recorded along 46 permanent transects located and evenly distributed from 3 000 to 6 000 m distance from the original Lehmann lovegrass seed source. Vegetation changes were evaluated by using a pair t-test (P < 0.05) comparison among years. From all species ; 15% disappeared, 30% declined, 49% remained unchanged and 6% increased in cover. Most grasses reduced cover over 50%, Bouteloua gracilis appeared in site, and invasive Lehmann lovegrass expanded cover for over 200 times. Six forbs species disappeared and five declined in cover by more than 80%. Two semi-shrubs : Gutierrezia microcephala and Viguiera decurrens disappeared. Seventy percent of shrubs remained unchanged, where Prosopis glandulosa appeared and Nolina texana expanded by 5 times. Species richness (species per transect) decreased from 15 species in 1985 to 6 species in 2005 from 3 000 to 4 500 m from the original seed source. Similarly, plant diversity (Shannon’s index) declined from 1985 (from 2–3.5 to 1–2.5 index value) in 2005. Vegetation changes in the 20 year period affected the abundance of many plant species and community diversity, Lehmann lovegrass exhibited a significant and progressive invasion of this central rangeland of Chihuahua. Key Words : diversity, evenness, invasive, plant cover, richness, similarity index.

Mots clés : Ecology, Lehmann lovegrass, Inavsive species, Range management, Biological sciences, Eragrostis lehmanniana Diversity, Nutrient value, Richness

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