Responses of vegetation to different land-use histories in the North-east Patagonian Monte, Argentina

PETER, GUADALUPE; FUNK, FLAVIA ALEJANDRA; TORRES ROBLES, SILVIA SUSANA

RANGELAND JOURNAL

AUSTRALIAN RANGELAND SOC

Año: 2013 vol. 35 p. 273 - 283

1036-9872

In arid and semiarid lands around the world vegetation is distributed in patches within a bare-soil matrix. We hypothesized that grazing increases the patch physiognomy; and fires and eolic erosion homogenize the vegetation distribution. We predict: 1) Greater cover, specific frequency and richness of shrubs in grazed sites; 2) Greater cover, specific frequency and richness of herbs and palatable grasses in ungrazed sites; 3) Random pattern of distribution in burnt places. We measured aerial cover of all perennial species at six sites with different land uses: highly grazed, medium grazed, ungrazed, long exclosure suddenly grazed, burnt and ungrazed, and burnt and grazed. Species were grouped in five plant functional types: shrubs, subshrubs, palatable grasses, non-palatable grasses and forbs. Our results showed significant differences in the cover of palatable and non-palatable grasses, forbs and total cover; without any evidence of shrub encroachment. Species frequency and richness decreased especially with increased grazing intensity. The spatial distribution pattern changed from aggregated in grazed sites to random in ungrazed and burnt places for all plant functional types. At the population level, the cover of the grass Poa ligularis was greatest in ungrazed situations whereas the cover of the shrub Chuquiraga erinacea was greatest in burnt places. We conclude that after applying a heterogeneous patchwork of disturbance, such as grazing or fire, followed by periods of rest, the plant diversity and forage production are increased.