Components and drivers of root fungal community composition in coffee agroecosystems: how do farming decisions influence diversity?

Coffee is a cash crop of central importance to smallholder well-being and local economies throughout the tropics. In Costa Rica, coffee farms range from organic management in forest gardens to industrialized monocultures. How do differences in field management influence rhizosphere diversity? Which factors are key to maintaining belowground fungal diversity on coffee farms? What roles do root fungi play on these farms and to what extent can fungi that benefit coffee plants be manipulated to improve yield while minimizing external inputs? These are some of the questions that we are currently addressing at twenty-five coffee fields in two regions of Costa Rica, Monteverde and San Vito.

How does plant root architecture influence root fungal community and functional roles of arbuscular mycorrhizas?

Plant root systems vary from barely branched and coarse to very finely-divided, with plants from the oldest lineages usually exhibiting coarser root systems and members of more recently evolved groups often producing fine roots that rival fungal hyphae in diameter. A major assumption in mycorrhizal ecology is that, by way of being far smaller in diameter than roots, fungal hyphae are able to access nutrients not otherwise available to the plant. Consistent with this hypothesis is the observation that plant families in which members are generally not mycorrhizal also tend to produce extremely fine roots. However, other plant families with fine roots do form mycorrhizas. Is nutrient acquisition always the primary function of arbuscular mycorrhizas for the plant? As hypothesized by other researchers, do arbuscular mycorrhizas play a role in protection of roots from natural enemies? Dr. Ylva Lekberg of MPG Ranch and I are addressing the question of how community composition of arbuscular mycorrhizal (AM) fungi may be influenced by root architecture and the roles that different AM fungi may play in the rhizosphere by comparing community composition across a precipitation and growing season-length gradient for plant species found from the mesic tallgrass prairie of western Minnesota to the semi-arid foothills prairie of western Montana.