Growth Dynamics of Nassella tenuis (Phil.) Barkworth, a Palatable Perennial Tussock Grass of Central Argentina: Effects of Water Regime and Grazing History

Abstract

This study examines the growth dynamics of Nassella tenuis (Phil.) Barkworth, a palatable perennial tussock grass, abundant in the natural grasslands of Central Argentina. It focuses on the effects of water regimes and grazing history. Plants were collected from sub-humid and semiarid grasslands with contrasting grazing histories (grazed and ungrazed) and cultivated under controlled conditions. Key growth traits, such as leaf elongation, senescence, and net growth rates, as well as tiller production, were assessed across the growth cycle. The results reveal that sub-humid grasslands favor faster growth rates and higher tiller production, while semiarid grasslands exhibit lower growth rates, potentially reflecting adaptive strategies for water-limited environments. Seasonal analysis revealed distinct life cycle patterns: plants from sub-humid grasslands exhibited higher elongation rates during autumn and spring, whereas growth in semiarid plants remained consistently low across seasons. Grazing history significantly influenced growth patterns, with grazed plants showing reduced tiller numbers and growth rates but lower senescence rates, particularly in semiarid grasslands. These findings underscore the importance of aligning grazing management practices with the growth dynamics of N. tenuis and the water regime of the site to optimize forage production while maintaining grassland resilience.