Ecological Model for Classifying and Monitoring of Green Needlegrass/Western Wheatgrass/Blue Gramma/Buffalograss Ecological Type

Abstract

A multivariate statistical model was developed to classify plant seral stages and to monitor succession of the green needlegrass (Nassella viridula (Trin.) Barkworth), western wheatgrass (Pascopyrum smithii (Rydb.) Á Löve), blue grama (Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths), buffalograss (Bouteloua dactyloides (Nutt.) J.T. Columbus) ecological type on grasslands of North and South Dakota, eastern Montana and Wyoming. Seral stages are objectively derived groupings of vegetation composition based on the range of natural variability within the current grassland ecological type. The model developed in this paper can be used by range and wildlife managers to evaluate management objectives by monitoring changes in plant species cover and composition within and among seral stages and community phases.  Four ecological seral stages representing early to late succession were quantitatively identified with an estimated 98 percent accuracy. Three common perennial grasses provide the information to assign seral stages and monitor trends based on index values (canopy cover (%) x frequency of occurrence (%)) for western wheatgrass, buffalo grass and green needlegrass.  Estimates of canopy cover and frequency of occurrence of these three plant species are all that is required for the model. The four defined seral stages provide resource managers with options to quantitatively evaluate management alternatives and objectives associated with state and transition community phases. The developed model for this ecological type is simple to use, reliable, repeatable, accurate and cost effective to meet management objectives and monitoring plans.