title: Variation in decomposition rates in the fynbos biome, South Africa: the role of plant species and plant stoichiometry.
abstract: Previous studies in the fynbos biome of the Western Cape, South Africa, have suggested that biological decomposition rates in the fynbos vegetation type, on poor soils, may be so low that fire is the main factor contributing to litter breakdown and nutrient release. However, the fynbos biome also comprises vegetation types on more fertile soils, such as the renosterveld. The latter is defined by the shrub Elytropappus rhinocerotis, while the shrub Galenia africana may become dominant in overgrazed areas. We examined decomposition of litter of these two species and the geophyte Watsonia borbonica in patches of renosterveld in an agricultural landscape. In particular, we sought to understand how plant species identity affects litter decomposition rates, especially through variation in litter stoichiometry. Decomposition (organic matter mass loss) varied greatly among the species, and was related to litter N and P content. G. africana, with highest nutrient content, lost 65% of its original mass after 180 days, while E. rhinocerotis had lost ca. 30%, and the very nutrient poor W. borbonica <10%. Litter placed under G. africana decomposed slightly faster than when placed under E. rhinocerotis. Over the course of the experiment, G. africana and E. rhinocerotis lost N and P, while W. borbonica showed strong accumulation of these elements. Decomposition rates of G. africana and E. rhinocerotis were substantially higher than those previously reported from fynbos vegetation, and variation among the species investigated was considerable. Our results suggest that fire may not always be the main factor contributing to litter breakdown and nutrient release in the fynbos biome. Thus, biological decomposition has likely been underestimated and, along with small-scale variation in ecosystem processes, would repay further study.
authors.affiliation: Department of Ecology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden. Jan.Bengtsson@ekol.slu.se
authors.forename: Jan
authors.initials: J
authors.lastname: Bengtsson
authors.forename: Charlene
authors.initials: C
authors.lastname: Janion
authors.forename: Steven L
authors.initials: SL
authors.lastname: Chown
authors.forename: Hans Petter
authors.initials: HP
authors.lastname: Leinaas
mesh_terms: D035722:Aizoaceae / Q000378:metabolism / Q000502:physiology*; D019659:Asteraceae / Q000378:metabolism / Q000502:physiology*; D017753:Ecosystem; D013019:South Africa; D013045:Species Specificity
references.citation: Ecology. 2009 Jan;90(1):90-9
references.pmid: 19294916
references.citation: Ecology. 2007 Jul;88(7):1611-21
references.pmid: 17645007
references.citation: Science. 2008 Aug 1;321(5889):684-6
references.pmid: 18669860
references.citation: Onderstepoort J Vet Res. 1992 Dec;59(4):323-33
references.pmid: 1297961
references.citation: Biol Rev Camb Philos Soc. 2003 Nov;78(4):597-638
references.pmid: 14700393
references.citation: Science. 1977 Jan 21;195(4275):260-2
references.pmid: 17787798
references.citation: Proc Natl Acad Sci U S A. 1998 May 12;95(10):5632-6
references.pmid: 9576935
references.citation: Ecol Lett. 2007 Dec;10(12):1135-42
references.pmid: 17922835
references.citation: Oecologia. 1993 Jul;94(4):457-471
references.pmid: 28313985