Grazing and plant growth interactions in a semiarid Festuca pallescens grassland.

BERTILLER, M. B.; DEFOSSÉ, G. E.

JOURNAL OF RANGE MANAGEMENT

Society For Range Management

Lugar: Lakewood; Año: 1990 vol. 43 p. 300 - 303

0022-409X

The effects of grazing on relative (g g-1 d-1) and absolute (g m-2 d-1) aboveground net primary productivity and senescence of coir´´on blanco (Festuca pallescens (St. Yves) Parodi)were investigated in northwestern Patagonia.  Aboveground net primary productivity under ungrazed and grazed conditions was estimated by means of a simulation model fitted to biomass data.  Relative and absolute aboveground net primary productivity was greater for grazed than ungrazed plants during the early growing season while the inverse occurred during the late growing season (reproductive period).  Grazing reduced the relative and absolute aboveground senescence during the late growing season.  Relative and absolute effective primary productivity expressed as the difference between the corresponding primary productivity and senescence, were greater for grazed than ungrazed plants.   This increase was in accordance with the grazing optimization hypothesis.  However, the increase was not of sufficient magnitude as to compensate for the loses of green biomass caused by grazing. Results imply that current grazing intensities in this region reduce aboveground productivity of coirón blanco.  It follows that a reduction in stocking rates would be necessary to increase aboveground primary productivity.