Combined effects of environment and grazing on vegetation structure in Argentine granite grasslands

Abstract

Abstract. Effects of grazing and environment on vegetation structure have been widely acknowledged, but few studies have related both factors. We made 57 floristic samples in a highly variable landscape of mountain grasslands in central Argentina; 26 sample were in fence‐lines with contrasting vegetation. For each sample, we recorded topographic and edaphic parameters, as well as grazing intensity indicators. Floristic gradients were analysed with DCA and relations with abiotic and grazing‐related variables were detected with DCCA. Floristic axis 1 was explained by edaphic parameters associated to topography, ranging from communities in well drained soils on upper topographic positions to hydromorphic vegetation in poorly drained soils on lower topographic positions. Species richness decreased as soil moisture increased. Floristic axis 2 was associated with present and long‐term grazing indicators, and reflected shifts in vegetation physiognomy and species evenness. Tall tussock grasslands, with low species evenness and evidences of low or null grazing intensity were located at one extreme. Tussocks were gradually replaced by short graminoids and forbs towards the centre of the gradient, as grazing increased, and evenness reached a maximum. In degraded sites with heavy long‐term grazing intensities, short perennial species were replaced by an annual species, and evenness decreased. The magnitude of changes in floristic composition produced by grazing decreased with increasing soil moisture, and vegetation‐environment relationships were stronger in moderate to highly grazed situations than in lightly or non grazed situations.

Soil Microbial Community Changes in Wooded Mountain Pastures due to Simulated Effects of Cattle Grazing

“…The effect of cattle or sheep on their environment can be subdivided into three categories of stress factors: herbage removal, dunging and trampling. Many studies have addressed effects of grazing (e.g., Cingolani et al, 2003;Milchunas and Lauenroth, 1993;Schlaepfer et al, 1998), trampling (Cole, 1995;Guethery and Bingham, 1996), dung deposition (Dai, 2000;Malo and Suarez, 1995), manuring or fertilizing (Gough et al, 2000) on grassland, heathland or woodland plant communities. Moreover, herbage removal, manuring and trampling have significantly different effects on seasonal plant dynamics of grasslands .…”

Distribution patterns and trophic characteristics of salmonids and native species inhabiting high altitude rivers of Pampa de Achala region, Argentina

“…Most streams belong to headwaters basins, and therefore first and second order streams become the dominant riverscape. Stream segments located outside the National Park exhibit impaired riparian areas due to ranching activity that have changed the vegetation structure (Cingolani et al, 2003). This may be an important factor affecting salmonid abundance which has been shown as negatively associated to lack of riparian vegetation (Dales Jones et al, 1999) and inflow of woody debris (Bryant, 1983;Dollof, 1986;MacMahon & Hartman, 1989).…”

La degradación de los bosques de altura del centro de Argentina reduce su capacidad de almacenamiento de agua

“…Además, el ganado, en combinación con el fuego, promueve la apertura de los pajonales en mata, lo que da lugar a céspedes de pastoreo. Ante condiciones de sobrepastoreo se generan pavimentos de erosión o pedregales donde la cobertura vegetal se reduce al mínimo y prevalece la roca expuesta debido a la pérdida parcial o total del suelo (Cingolani et al 2003(Cingolani et al , 2008(Cingolani et al , 2013(Cingolani et al , 2014. Si bien la profundidad del suelo es naturalmente variable debido a la microrugosidad de la roca madre y a la topografía, se ha encontrado que el disturbio actúa de manera sinérgica con estas variaciones naturales, alterando las propiedades edáficas (Cingolani et al 2008(Cingolani et al , 2013.…”

“…El paisaje se conforma por un mosaico de vegetación con estructura variable, que comprende desde bosques de P. australis y pajonales con distinto grado de apertura hasta pedregales y pavimentos de erosión con sólo pequeños parches de suelo remanente (Cingolani et al 2003(Cingolani et al , 2008(Cingolani et al , 2013(Cingolani et al , 2014Renison et al 2006Renison et al , 2010. El pastoreo por ganado doméstico y el fuego asociado al manejo impactaron fuertemente sobre el sistema y causaron cambios estructurales, en algunos casos poco reversibles (Cingolani et al 2003(Cingolani et al , 2008(Cingolani et al , 2013(Cingolani et al , 2014.…”