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New Phytol. 2015 Apr;206(2):507-21. doi: 10.1111/nph.13203. Epub 2014 Dec 10.

Phosphorus limitation, soil-borne pathogens and the coexistence of plant species in hyperdiverse forests and shrublands.

Author information

1
School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA, 6009, Australia.

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.

KEYWORDS:

Janzen-Connell hypothesis; alpha diversity; kwongan; monodominance; mycorrhizal fungi; negative density dependence (NDD); plant-soil feedback; tropical rainforest

PMID:
25494682
DOI:
10.1111/nph.13203
[Indexed for MEDLINE]
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