Arbuscular mycorrhizae in a tropical sand dune ecosystem on the Gulf of Mexico

Abstract

 The effects of arbuscular mycorrhizal fungi on the growth of seven plant species established during the first stages of colonization in different areas of a tropical sand dune system on the Gulf of Mexico were investigated by comparing several growth parameters in 21- and 63-day-old mycorrhizal and non-mycorrhizal plants. There were no significant differences between mycorrhizal and non-mycorrhizal plants in root, stem and leaf biomass after 21 days, but after 63 days, mycorrhizal responsiveness was evident. Ipomoea pes-caprae, Sporobolus virginicus and Canavalia rosea, stoloniferous pioneer species of the beach, embryo dunes and foredunes, were less responsive to the mycorrhizal treatment, following the trend predicted for early seral species. However, large increases in total dry weight, leaf area and relative growth rate of Chamaecrista chamaecristoides, Palafoxia lindenii and Trachypogon gouinii (plants from the beach, embryo dunes and foredunes as well as mobile dunes) suggest that mycorrhizal infection is also crucial for the growth of early successional species. Most species allocated the same or more biomass to shoots than to roots. With the exception of T. gouinii, this pattern of biomass allocation was not altered by the mycorrhizal treatment. C. rosea and S. virginicus showed a higher allocation to the roots in the non-mycorrhizal plants. The possible relationship between mycorrhizae and succession in this tropical sand dune ecosystem is discussed.