Impact of stocking rate on species diversity and composition of a subtropical grassland in Argentina.

PIZZIO, R.; HERRERO JÁUGUERI, C.; PIZZIO, M.; OESTERHELD, M.

APPLIED VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016

1402-2001

Questions: What is the effect of a range of controlled stocking rates on plantspecies richness and diversity?Location: Subtropical grasslands of Corrientes, Argentina, South America.Methods: We studied the effect of three controlled stocking rates (0.6, 0.8 and1.0 cow equivalentsha1) on species diversity and composition during 8 yr. Wecalculated species diversity using the antilog of the Shannon-Wiener index, andconsidered its two components, richness and evenness. We also assessed theproportion of prostrate and erect species. Species abundance was based on bio-mass estimations.Results: Species diversity under high stocking rates gradually decreasedthroughout the experiment and became nearly 50% lower than under lowstocking rate. This decline was largely accounted for by changes of evennessbecause species richness was not affected by stocking rates. Species compositionclearly diverged among the three treatments over time. Low stocking rate main-tained a fairly constant relative cover of erect and prostrate grasses throughoutthe experiment, whereas intermediate and high stocking rate treatments weregradually and consistently enriched in prostrate grasses and forbs. These effectsoccurred simultaneously with drastic inter-annual changes likely driven byannual precipitation.Conclusions: The range of stocking rates had no effect on speciesrichness, but reduced diversity through the effect on evenness. High stock-ing rate progressively increased the proportion of prostrate species in thebiomass.