Aboveground biomass estimation of broom snakeweed (Gutierrezia sarothrae) plants

Two growth season-specific multiple linear regression models were developed to estimate individual broom snakeweed (Gutierrezia sarothrae (Pursh) Brit t. & Rusby) aboveground biomass from plant morphological variables that can be measured easily and non-destructively in the field. Predictor Variables were plant height, number and estimated average length of leafy stems (cur rent year's growth), number of woody stems (past years' growth), and length of longest woody stem. Number of woody stems, number of leafy stems, estim ated average length of leafy stems, and estimated total length of leafy ste ms accounted for 89% of the variation in individual aboveground biomass for plants collected in early spring (April). Number of woody stems, length of longest woody stem, number of leafy stems, and estimated total length of l eafy stems accounted for 95% of the variation in individual aboveground bio mass of plants collected in late summer (August). Successful cross-validati on suggests that these models may have wide applicability in predicting abo veground biomass of snakeweed.