Relationships between physical and chemical characteristics of 3 Sandhills grasses.

Abstract

Physical and chemical traits of grass tillers can be strongly correlated. Understanding such patterns would help define physiological development of tillers and changes in quality of forage in Sandhills grasses. Physical and chemical traits were quantified for sand bluestem (Andropogon hallii Hack.), prairie sandreed [Calamovilfa longifolia (Hook.) Scribn.], and little bluestem [Andropogon scoparius (Michx.)] on 3 sites at 4 times (mid-June, July, August, and October) during the 1990 and 1991 growing seasons. Thirty tillers were identified along two, 50-m transects (30 tillers/species/transect) within each site and tiller growth stage, length, and erectness determined. Tiller weight was defined from plants collected within 20 quadrats/site. Protein content, in vitro dry-matter digestibility (IVDMD), hemicellulose, total cell wall, acid detergent fiber (ADF), lignin, ash, total chlorophyll, and nonstructural carbohydrates (TNC) were determined on plant materials representing the dominant growth stages. Relationships among traits of the 3 species were determined by Spearman's rank correlation, and among linear combinations of sets of chemical and physical traits by canonical correlation analysis. Tiller length, weight, and growth stage were positively correlated (P < 0.05) and increased with length of growing season. Crude protein, digestibility, hemicellulose and chlorophyll were positively correlated and declined, but negatively correlated with lignin and ash. Significant (P < 0.05) correlations between the first canonical variates indicated a strong relationship between tiller maturity/architectural development (physical canonical variate) and forage quality (chemical canonical variate) was present, and large portions of variance in the original variables was defined. Results of this study defined large-scale multi-dimensional relationships between declining forage quality and increasing tiller maturity/architectural development, previously noted in many univariate analyses of limited sets of characteristics.