M.D. Mayor

Botanical composition and seasonal trends of cattle diets in central Argentina.

About 40,000 km2 of the Caldenal in central semiarid Argentina are rangelands where the most important economic activity is cow-calf operations. Some information on forage species, mainly regarding taxonomy, ecophysiology, and nutritive value, is available, but detailed studies on composition of free-ranging cattle diets are lacking. The objective of this work was to study the botanical composition and seasonal trends of cattle diets in the southern Caldenal. Diets were studied through microscopic analysis of cattle feces collected monthly in a typical plant community during a 12-month period. Grasses were the bulk of the diets, except in November when more than 50% of the diet was Medicago minima (L.) Grufberg. Highest consumption among the grasses was of Piptochaetium napostaense (Speg.) Hack., one of the dominants in the grass layer. High consumption of Pappophorum mucronulatum Nees, one of the few warm-season grasses in the region, was found during the summer. Calden (Prosopis caldenia Burk.) pods, consumed in late summer and fall, were the only woody fragments found in appreciable amounts. Classification and ordination techniques were used to analyze seasonal trends. In spite of a relatively high homogeneity in the diets, 2 well-defined seasonal trends were detected, one in the fall-winter period and another in the spring. Cattle diet diversity was minimum during the coldest months of the year.

Effect of fire on growth of three perennial grasses from central semi-arid Argentina

Abstract The effect of fire on growth of Piptochaetium napostaense , Stipa tenuis , and Stipa gynerioides , three important native perennial grasses in the semi-arid region of central Argentina, was evaluated under different fire temperature regimes: 300–400°C (low temperature regime), 500–600°C (high temperature regime) and no fire (control). Fire treatments were applied with a portable propane plant burner in April and December 1994, May 1995, and January 1996. Overall results indicate that during the first months after fire occurrence, average total green length of S . tenuis , P . napostaense and S . gynerioides tillers was severely reduced ( p P . napostaense , S . tenuis , and S . gynerioides were similar or greater ( p S . tenuis , P . napostaense and S . gynerioides were greater than in tillers of control plants. Our results indicate that fire affected differentially the growth of the studied species; S . gynerioides was more affected by fire than P . napostaense and S . tenuis . The species most tolerant to fire was P . napostaense .