Mycorrhizal dynamics and dependence of Desmoncus orthacanthos martius (Arecaceae), a native palm of the Yucatan Peninsula, Mexico

Abstract

Field observations were carried out to determine the seasonal patterns and recovery from disturbance by arbuscular mycorrhizal (AM) associations in Desmoncus orthacanthos Martins, eight years following shifting agriculture and in a mature forest. In addition, a greenhouse experiment was performed to determine the relative mycorrhizal dependency (RMD) of this species. Four growth stages were selected, and roots and rhizosphere soil of five individuals from each stage were monitored during one year A seasonal pattern, but no difference in abandoned agriculture and mature forest were found in AM fungal activity. Soil moisture, spores per gram of soil, and percentage of root colonization were not correlated during this year. Root colonization was highest at both sites during the wet season, but was equally high during one dry season observation in the abandoned milpa. Spore density was highest during the dry season. The RMD ranged from 7.8 to 54.9%, with greater biomass of mycorrhizal than non-mycorrhizal plants using P solutions that mimicked field soil concentrations. This suggests that this slow-growing palm is highly dependent on mycorrhizal fungi in local soils and maintains relatively high AM activity even during the dry season. Culture of this slow-growing, understory palm for the rattan industry requires that soils be managed for high levels of AM fungi. The study showed that the standard local practice of shifting agriculture enables sufficient recovery of soil inoculum for growth of D. orthacanthos.