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

Accueil du site → Master → Etats Unis → 1979 → Quadrat frequency sampling in a semi-desert grassland

University of Arizona (1979)

Quadrat frequency sampling in a semi-desert grassland

Yavitt, Joseph Benjamin

Titre : Quadrat frequency sampling in a semi-desert grassland

Auteur : Yavitt, Joseph Benjamin

Université de soutenance : University of Arizona

Grade : Master of Science (MS) 1979

Frequency sampling on six semi-desert range sites was studied with the following objectives : (1) to determine the minimal repre sentative sample area, (2) to compare systematic quadrat placement to subsampling with transects, and (3) to determine relative efficiency of linear versus rectangular plots. Species presence was recorded in 11 plot sizes ranging from 2 2 .25 m to 900 m . Plot size needed to record 50% of total species in the stand was used as the criterion for a representative sample. A plot of 10 x 10 m met this criterion. 2 Species frequency was recorded in .16 m quadrats in a 20 x 20 grid (400 quadrats) spaced at 1.25 m intervals. Occurrence of species in quadrats was found, in most cases, to be independently distributed, thus permitting statistical treatment of systematic data. Grouping quadrats into 20 transects and analyzing components of variance showed that, for most species, use of transects gave no increase in precision compared to grid placement. Using 250 quadrats, sampling efficiency of rectangular plots (10 x 25 quadrat grid) was compared to linear plots with quadrats placed end-to-end spaced 1.75 m apart. Based on six.plots of each shape the number required to sample at a given level of precision was found to be 9-10 plots in both cases.

Mots clés : Grasses — Research — Arizona. ; Grasslands — Arizona. ; Plant populations — Measurement.


Version intégrale (1,03 Mb)

Page publiée le 25 janvier 2016, mise à jour le 18 décembre 2017