The editor’s choice for our August issue is “Seasonality regulates the structure and biogeochemical impact of ectomycorrhizal fungal communities across environmentally divergent neotropical dry forests“ by Katilyn Beidler et al. Here, Associate Editor James Dalling discusses the importance of this research:
We usually think of ectomycorrhizal (ECM) tree species in the tropics as occurring on the tops of mountains or in the dipterocarp forests of the wet lowland tropics of Southeast Asia. However, ectomycorrhizal species are broadly distributed – including a range of plant and fungal lineages that occupy seasonally dry tropical forests (SDTF) of Central and South America and the Caribbean. In their paper, Katilyn V. Beidler and collaborators explore the drivers of ECM fungal community composition across four environmentally divergent SDTF and assess the impact these communities have on soil carbon and nitrogen cycling.
Seasonally dry tropical forests are characterized by a prolonged and severe dry seasons, during which many plant species are deciduous. Unlike wet forests, that tend to be relatively homogeneous (at least in climate), SDTF occupy a wide range climate conditions. The researchers exploited this variation, with dry seasons ranging from 4 to 10 months, by establishing similar permanent plots in Mexico, Costa Rica, Puerto Rico and Colombia. They then used identical protocols to sample ECM fungi from the soil and collected standardized data on climate, soil chemistry and vegetation. These datasets allowed them to assess how environmental variables and physical distance affected the composition of the ECM community, characterized by sequencing fungal ITS rDNA.
Tropical dry forests are considered one of the most endangered ecosystem types – with large areas burned or converted to agriculture. This study adds to our understanding of the distinctiveness of these forests. Individual countries harbored distinct ECM fungal communities that were primarily structured by rainfall seasonality and by tree species community composition. Communities in each country were dominated by different fungal lineages, with not a single ECM fungal taxon in common. Information on the ECM community also improved model fits predicting carbon and nitrogen cycling. Broad scale sampling of ECM communities across habitat types (and across biogeographic regions) has only just begun. Comparative experimental studies such as these are a demonstration of the power of well-designed international research projects that build on existing expertise in tropical countries and, in this case, reveal larger patterns in the distribution of key symbionts that sustain the functioning of forest ecosystems.
