Cardinal temperatures and morphogenetic characters of two forage Patagonian grasses. First step for sustainable grazing management

Abstract

Knowing the morphogenesis of forage species is an essential condition for the correct management of grazing in arid environments. Our aim was to define cardinal temperatures and morphogenetic characters for Poa ligularis and Bromus pictus, the most preferred and endangered Patagonian grass species. We grew plants in growth chambers at different temperatures under adequate water and nutrient supply. Our results were similar to those reported for other temperate species: base temperatures: 0°C, optimal temperatures: ≈22°C and maximum temperatures: ≈27.5°C for both species, and phyllochrons: 212.8 and 222.2 GDD (growing degree days), leaf appearance rates (LAR): 0.0047 and 0.0045 leaves.GDD−1, number of living leaves (NLL): 2.7 and 2.9 per tiller and leaf lifespan (LLS): 582 and 662 GDD, for P. ligularis and B. pictus, respectively. Cardinal temperatures, LAR and phyllochron did not differ between these species but NLL and LLS were lower for P. ligularis than for B. pictus. Results shown these species are similar to other temperate grasses under non-limiting water and nutrient conditions. These findings are the first step to propose field experiments that allow the accurate estimation of grazing and resting times in order to avoid consumption of unexpanded leaves and allow tillers to attain their maximum NLL.