Estimating Twig and Foliage Biomass of Sagebrush, Bitterbrush, and Rabbitbrush in the Great Basin

Abstract

Shrub crown characteristics useful in regression equations for predicting two biomass components (annual production and fine fuels) were identified for six shrubs common to the Great Basin. Shrub characteristics most useful in these equations were maximum and minimum crown diameter, and crown denseness and depth. Prediction equations were developed for each species or subspecies included in this study. Additionally, biomass equations were developed for combined species or subspecies of morphological similarity within the Artemisiu genus. As early as 1958, Evans and Jones addressed the practical importance of a method for determining forage production in which clipping or mowing was not necessary. Since then, much attention has been directed toward developing methods for predicting shrub production from easily measured crown dimensions. Volumetric or crown area relationships based on crown height and diameters have been described for serviceberry (Amelanchier alnifolia) by Lyon (1968), for eight Chihuahuan desert shrubs by Ludwig et al. (1973, and for big sagebrush (Artemisia tridentata wyomingensis) by Rittenhouse and Sneva (1977). Brown and Marsden (1976) and Alexander (1978) developed equations for predicting fuel loadings from height and percent crown cover measurements. Various stem diameter measurements were used as biomass predictors by Ohmann et al. (1976), Brown (1976), and Grigal and Ohmann (1977). Davis et al. (1972) related forage production to ring widths for several salt desert shrub species. Thus, the value and practicality of such methods has been well documented. The sagebrush taxon, Artemisia, constitutes the most abundant and widespread shrub component of ecosystems in the Great Basin and provides a source of food and cover for livestock and wildlife. Taxonomic difficulties exist within this genus at the species, subspecies, and variety levels. Although ecological differences have been described (Winward and Tisdale 1977), field identification of sagebrush species is often difficuh to determine. This is especially true between low and black sagebrush (A. arbuscula and A. nova) and the subspecies differentiations for big sagebrush (A. tridentata ssp. tridentata, A. tridentata spp. vaseyana, and A. tridentata spp. wyomingensis). A reliable dimension analysis technique for determining canopy biomass components in which species differences were not necessary would expedite field data collection and data analysis procedures. The primary objective of this study was to identify shrub crown characteristics which could be used to predict two shrub biomass components (annual production and fine fuels) and to formulate reliable prediction equations from these characteristics.

Forage biomass of 22 shrub species from Monfragüe Natural Park (SW Spain) assessed by log–log regression models

“…In some studies where a different statistical approach (e.g. asymptotic or multi-variate) was used, the r 2 values were less significant than in our data (Dean et al, 1981;Smith et al, 1983). Table 3 shows the log-log equations (to the base e) for the 22 species, the number of sampled (measured) and harvested (forage biomass) plants, and the percentage of outliers.…”

Pr�diction de la biomasse a�rienne d'Acacia cyanophylla Lindl. (Syn. A. saligna (Labill.) H. Wendl) � partir de mensurations dimensionnelles

“…En d'autres termes, on peut s'attendre à une forte corrélation entre la masse et le volume occupé par l'arbuste. En effet, la régression linéaire a été adoptée par plusieurs travaux de recherche visant l'établissement d'un modèle qui permet la prédiction de la biomasse des arbustes fourragers [8,9,19,27]. Pieper [26] note que la plupart des régressions tentées entre la biomasse et le volume de l'arbuste ont donné des coefficients de détermi-nation qui varient de 0,89 à 0,99.…”

Rangeland vegetation productivity and biomass

“…Log transformations have been used for big sagebrush (Artemisia tridentata) (Rittenhouse and Sneva 1977), mountain mahogany (Medin 1960), Gambel oak (Hutchings and Mason 1970), various shrubby species on the Edwards Plateau of Texas (Bryant and Kothmann 1979), several California shrubs (Bentley et al 1970) and several Great Basin shrubs (Dean et al 1981).…”

“…Twig length or diameter has been used to predict shrub biomass (Basile and Hutchings 1966, Telfer 1969, Halls and Harlow 1971, Ferguson and Marsden 1977, Lyon 1980, Dean et al 1981, Provenza and Urness 1981, Bartolome and Kosco 1982, Ruyle et al 1983) for a variety of browse species. In some cases, additional measurements increased the r2 values (Schuster 1965).…”