Abstract

TORRES, Yanina; BUSSO, Carlos; ITHURRART, Leticia  and  AMBROSINO, Mariela. Morphological traits which contribute to the long-term persistence of Pappophorum vaginatum in rangelands of Argentina. Multequina [online]. 2020, vol.29, n.1, pp.27-59. ISSN 1852-7329.

Pappophorum vaginatum is the most abundant C4 perennial grass desirable (i.e., preferred) to livestock in rangelands of northeastern Patagonia, Argentina. Other less abundant, native pe rennial grasses in the community are Aristida spegazzinii and A. subulata, and the desirable Sporobolus cryptandrus. Aristida spegazzini and A. subulata are only grazed when a better forage is not available. The objective of this study was to determine various above- and belowground morphological traits that might help to explain the greater abundance of P. vaginatum in relation to the other species, in a community where P. vaginatum is the only perennial grass available for livestock grazing since decades ago. Plants of all species were either exposed or not exposed to a severe defoliation twice a year during two growing seasons (i.e., 2007-2008 and 2008-2009). These growing seasons had 42 % (2007-2008) and 30 % (2008-2009) lower precipitation than the annual mean precipitation (i.e., 416.7 mm). This was a desirable water stress to know the response of both species to extreme water levels under field conditions. Plant developmental morphology stages were delayed, on all studied perennial grasses, more in the drier (2008-2009) than in the wetter (2007-2008) study year. Defoliation did reduce the studied morphological characteristics after plants of all species were defoliated twice in 2007-2008 and 2008-2009. The higher values of most of the components of leaf area production in P. vaginatum than in the oth er species in the study could help to explain its higher abundance in the rangelands of Argentina. Knowledge of the mechanisms involved in grazing tolerance of P. vaginatum will be useful to: (1) increasing its grazing tolerance through a genetic improvement plan, and (2) implementing management guidelines that increase its plant production under grazing conditions.

Keywords : Pappophorum vaginatum; Warm season grasses; Defoliation; Genetic improvement.

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