title: Phosphorus limitation, soil-borne pathogens and the coexistence of plant species in hyperdiverse forests and shrublands.
abstract: Hyperdiverse forests occur in the lowland tropics, whereas the most species-rich shrublands are found in regions such as south-western Australia (kwongan) and South Africa (fynbos). Despite large differences, these ecosystems share an important characteristic: their soils are strongly weathered and phosphorus (P) is a key growth-limiting nutrient. Soil-borne pathogens are increasingly being recognized as drivers of plant diversity in lowland tropical rainforests, but have received little attention in species-rich shrublands. We suggest a trade-off in which the species most proficient at acquiring P have ephemeral roots that are particularly susceptible to soil-borne pathogens. This could equalize out the differences in competitive ability among co-occurring species in these ecosystems, thus contributing to coexistence. Moreover, effective protection against soil-borne pathogens by ectomycorrhizal (ECM) fungi might explain the occurrence of monodominant stands of ECM trees and shrubs amongst otherwise species-rich communities. We identify gaps in our knowledge which need to be filled in order to evaluate a possible link between P limitation, fine root traits, soil-borne pathogens and local plant species diversity. Such a link may help to explain how numerous plant species can coexist in hyperdiverse rainforests and shrublands, and, conversely, how monodominant stands can develop in these ecosystems.
authors.affiliation: School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA, 6009, Australia.
authors.forename: Etienne
authors.initials: E
authors.lastname: Laliberté
authors.forename: Hans
authors.initials: H
authors.lastname: Lambers
authors.forename: Treena I
authors.initials: TI
authors.lastname: Burgess
authors.forename: S Joseph
authors.initials: SJ
authors.lastname: Wright
mesh_terms: D044822:Biodiversity; D017753:Ecosystem; D065928:Forests; D038821:Mycorrhizae / Q000502:physiology*; D010758:Phosphorus / Q000172:deficiency*; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D010944:Plants / Q000378:metabolism* / Q000382:microbiology; D012988:Soil Microbiology; D013019:South Africa; D013021:South Australia; D014197:Trees; D014904:Western Australia
chemical_list: D010758:Phosphorus
keywords: Janzen-Connell hypothesis; alpha diversity; kwongan; monodominance; mycorrhizal fungi; negative density dependence (NDD); plant-soil feedback; tropical rainforest