Diversity of mycorrhizal types along altitudinal gradients in mountain tropical forests of northern South America

Abstract

Mycorrhizal fungi play key roles in the functioning of terrestrial ecosystems. The main types of mycorrhizal associations are arbuscular mycorrhizas (AM), ectomycorrhizas (EcM), ericoid mycorrhizas (ErM) and orchid mycorrhizas (OM). Previous studies have shown that the abundance of AM, EcM and ErM plants change gradually along latitudinal and altitudinal gradients driven by the effects of climate on decomposition, reflected in the accumulation of carbon and nutrients in the soil. The Colombian Andean mountain range reaches altitudes over 5,000 m and it is a great system to test the effects of altitude in tropical ecosystems. We aimed to understand how altitude and climatic and soil conditions shape the distribution patterns of mycorrhizal types in plant species distributed in this region. To test this, we used an herbarium plant record database and assigned mycorrhizal type based on the available literature. We also used bioclimatic and soil variables at a resolution of 10 km. We calculated the proportion of each of the different mycorrhizal associations types per grid cell and created a diversity index to explore their spatial distribution and their association with abiotic factors based on GLMs. We found that the diversity of mycorrhizal associations increases with altitude and soil carbon stock.