An Ecophisiological Proposal to Manage Natural Grasslands: A Long Term Trial

Natural grasslands on Southern Brazil comprise the so called “Rio de La Plata Grasslands” in South America. They are an important fodder source for ruminant pastoral systems and contribute to regional ecosystem services. Strength of these grasslands is its floristic diversity that poses a dilemma to farmers: how to choose management protocols that could be applied for hundreds of species. We propose to use a functional ecophysiological approach based on groups of grasses, the most abundant on aerial biomass of this natural grasslands. We clustered the most frequent grasses in two groups based on its leaf traits (leaf dry matter content and specific leaf area). These traits are functional clues to growth rhythms and nutritive value that could separate grasses in “resource capture” and “resource conservation” groups, both important for forage production and ecosystem services. Evaluating the most frequent grasses in each group we found they have an average of 375 degree-days, for “resource capture” and 750 degree-day for “resource conservation” groups, as its leaf elongation duration. So we evaluated a rotational grazing system based on this morphogenic trait for beef heifers rearing on natural grasslands from 2010 to 2019. We chose these experimental animals, as a model by its nutrient requirements and relevance for regional rearing and breeding systems. Our results indicate an average daily gain that is adequate to reach mating age and weight targets (0,3 kg/heifer/day to mate at 24 months) and allowed a higher stocking rate and gain per area when compared to regional standards (1,100 kg of live weight/ha and 370 kg/ha versus 600 and 70 kg/ha). All this animal performance was obtained without changing floristic diversity and also enhancing ecosystem services as CO2 sequestration. We concluded that this approach could allow farmers to conciliate the dilemma of production and conservation in pastoral ecosystems