IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Overgrazing affects arbuscular mycorrhizae diversity and abundance in Patagonian steppe.
Autor/es:
VON DUDINSZKY N, CABELLO MN, GRIMOLDI AA, SCHALAMUK S, GOLLUSCIO RA
Lugar:
Hohhot, China
Reunión:
Congreso; VIII International Rangeland Congress.; 2008
Institución organizadora:
Internacional Rangeland Society
Resumen:
Introduction:Arbuscular mycorrhizae fungi (AMF) are critical for survival of most plants in arid ecosystems (Titus et al. 2002). This also might be true in the case of Patagonian steppe, which faces desertification processes mainly as a result of overgrazing (León y Aguiar 1985). AMF diversity is affected by plant diversity; if the latter decrease it is expected that the former would do the same (Johnson et al. 2003). Losses in plant cover and substitution of palatable species by unpalatable ones are overgrazing consequences in the Patagonian steppe. Therefore, the effects of overgrazing on the AMF community were evaluated in the Patagonian steppe.  Materials and methods:  AMF spore abundance and diversity were evaluated in Patagonian steppe in ungrazed, moderately grazed and overgrazed plots. Soil samples were taken from the rhyzospheric soil of the more conspicuous Patagonian steppe grasses (palatable Bromus pictus and Poa ligularis, less palatable Stipa speciosa and unpalatable Stipa humilis) and under bare soil patches. Spores were extracted by the methods of Gerdeman and Nicholson (1863) and Walker et al. (1982). Fungal density was considered as total spore number per 100g of soil. Fungal specific spore density was quantified to calculate the biodiversity index Shannon-Weaver, H. Trap cultures were made for spore identification.  Results & Discussion:  AMF spore abundance in general was highest in the ungrazed plots and lowest in the overgrazed ones. AMF community associated with S.humilis was less affected by grazing and showed a higher AMF spore abundance under moderately grazed conditions. AMF fungal diversity was highest in ungrazed and moderately grazed plots and lowest in overgrazed plots. Glomaceae familly was dominant in all sites and Gigasporacea family disappeared in the overgrazed sites. Pacispora sp. was present in all sites and it was the first time ever it was found in an Argentinian ecosystem. <!--[if !vml]--> <!--[endif]--><!--[if !mso]--> <!--[endif]--> Fig.2 AMF spore biodiversity index (Shannon-Weaver), H. Under ungrazed (UG), moderately grazed (MG) and overgrazed (OG)   conditions.<!--[if !mso]--><!--[endif]--><!--[if !mso & !vml]--> <!--[endif]--><!--[if !vml]--><!--[endif]--> <!--[if !vml]--> <!--[endif]--><!--[if !mso]--> <!--[endif]--> Fig.1. Number of spores/100g soil in the rhizospheric soil of B.pictus (BP), P.ligularis (PL), S.speciosa (SS), S.humilis (SH) and Bare Soil (BS); in ungrazed, moderately grazed and overgrazed plots. <!--[if !mso]--><!--[endif]--><!--[if !mso & !vml]--> <!--[endif]--><!--[if !vml]--><!--[endif]-->Conclusions: Overgrazing may alter the ecosystem functioning of the Patagonian steppe not only by reducing the plant cover but also by reducing AMF abundance and diversity, thus increasing the process of desertification Overgrazing may alter the ecosystem functioning of the Patagonian steppe not only by reducing the plant cover but also by reducing AMF abundance and diversity, thus increasing the process of desertification Overgrazing may alter the ecosystem functioning of the Patagonian steppe not only by reducing the plant cover but also by reducing AMF abundance and diversity, thus increasing the process of desertification Overgrazing may alter the ecosystem functioning of the Patagonian steppe not only by reducing the plant cover but also by reducing AMF abundance and diversity, thus increasing the process of desertification