Mineral cycling and epiphytic lichens: Implications at the ecosystem level

The nutrient contribution of lichens as litterfall in forests is discussed for a number of different ecosystems and it is hypothesized that lichens are important in capturing nutrients from wet deposition, occult precipitation, sedimentation, impaction and gaseous uptake. Most nutrients captured by these processes represent new nutrient inputs that would otherwise not be intercepted by the ecosystem. Part of these nutrients will be incorporated into lichen biomass and only become available upon death and decomposition, but a portion will be leached by precipitation and become deposited on the soil surface. Although quantifying nutrient sources, fluxes and pool sizes is a potentially complex task, we describe a simplified approach for determining whether lichens significantly affect the mineral cycling of a forest. Preliminary results for an oak woodland in California document that epiphytic lichens may reduce throughfall and alter throughfall chemistry.