Global patterns in belowground communities

A b s tra c t A lthough below ground ecosystems have been studied extensively and soil biota play integral roles in biogeochem icai processes, surprisingly we have a lim ited understanding o f global patterns in below ground biom ass and com m unity structure. T o address this critical gap, we conducted a meta-analysis o f published data (> 1300 datapoints) to com pare below ground plant, m icrobial and faunal biom ass across seven o f the m ajor biom es on Earth. W e also assem bled data to assess biome-level patterns in below ground m icrobial com m unity com position. O ur analysis suggests tha t variation in m icrobial biom ass is predictable across biom es, w ith m icrobial biom ass carbon representing 0.6— 1.1% o f soil organic carbon ( / — 0.91) and 1-20% o f to tal p lant biom ass carbon ( / — 0.42). A pproxim ately 50% o f to tal anim al biom ass can be found below ground and soil faunal biom ass represents < 4% o f m icrobial biom ass across aU biomes. The structure o f below ground m icrobial com m unities is also predictable: bacterial com m u­ nity com position and fungal : bacterial gene ratios can be predicted reasonably well from soil p H and soil C : N ratios respectively. T ogether these results identify robust patterns in the structure o f below ground m icrobial and faunal com m unities at broad scales which m ay be explained by universal m echanism s tha t regulate below ground biota across biomes. Noah Fiererd’^* Michael S. Stricklandd Daniel Liptzind Mark A. Bradford^ and Cory C. Cleveland® ’D epartm ent o f Ecology and Evolutionary Biology, University o f Colorado, Boulder, CO 80309, USA ^Cooperative Institute for Research in Environmental Sciences, University o f Colorado, Boulder, CO 80309, USA ^Odum School o f Ecology, University o f Georgia, Athens, GA 30602, USA "'Department o f Environmental Science, Policy, and M anagem ent, University o f California, Berkeley, CA 94720, USA ^School o f Forestry and Environmental Studies, Yale University, N ew Haven, CT 06511, USA ^Department o f Ecosystem and Conservation Sciences, University o f Montana, Missoula, MT 59812, USA * Correspondence: E-mail: [email protected] K eyw ords Acari, CoUembola, nem atodes, 16S rRN A , soil bacteria, soil faunal biomass, soil food webs, soil fungi, soil m icrobial biomass.