Spores abundance and diversity of arbuscular mycorrhizal fungi in the Caldenal Forest, Argentina

ONTIVERO, R. E.; RISIO ALLIONE, L. V.; LUGO, M. A.

San Carlos de Bariloche

Workshop; II International Workshop: Mycorrhizal Symbiosis in the Southern Cone of South America.; 2019

Arbuscular mycorrhizal fungi (AMF, Glomeromycota) are biotrophic mutualistic symbionts of the80% of the terrestrial plants; AMF increase their hosts growth through its contribution to the waterand nutrients absorption from soil to the plant roots. The AMF mycelia and spores are commoncomponents of the biological soil communities. The different AMF taxa vary in their edaphic andnutritional preferences, the host species ranges and the seasonal changes in sporulationfeatures. The increase in world human population and the global demand for natural resources,have acted as an important driving force for agricultural changes in Argentina in the last 150years. Thus, a territory of high agricultural productivity and low population, such as the CentralArgentina, has changed drastically at this stage. Particularly, in Espinal ecoregion the synergy ofnatural and/or anthropogenic changes has modified intensely the dynamics of the xeric foreststhat dominated the region. Therefore, in San Luis province the Prosopis caldenia Burkart forests(or "Caldenales") have suffered a reduction of 12.600ha in the last 10 years. This changesprobably also have affected soil community, for that reason is important to study the AMF communities in the Caldenal Forest soils. The aim of this work was to know the abundance anddiversity of AMF spores at the northern limit of the Caldenales. The sampling sites were fourforests in San Luis (Argentina); at each site, soil samples were collected, packed and transportedto the laboratory. The AMF spores were extracted from 100g of field soil from each sample bywet sieving followed by sucrose centrifugation and quantified using an optical microscope.Species identification was performed using the specific bibliography and the INVAM database.There were plots with spore abundance differences, the most abundant plot had almost twice thetotal number of spores. All plots showed similar values of Shannon-Wienner index and Simpson´sDiversity index. Herbaceous stratum, shrub stratum and tree stratum diversity none have effecton spore abundance; instead, the lowest spore abundance occur in the plot with highest numberof young trees. Furthermore, the lowest abundance of spores coincided with the only plot grazedby horses; the other plots were occasionally cattle grazed. Hence, in Caldén Forests thesepreliminary results showed that spores abundance could be influenced by different factors suchas plant phenology and forest uses history