Negative Plant–Soil Feedback and Positive Species Interaction in a Herbaceous Plant Community

Abstract

Increasing evidence shows that facilitative interaction and negative plant-soil feedback are driving factors of plant population dynamics and community processes. We studied the intensity and the relative impact of negative feedback on clonal growth and seed germination of Scirpus holoschoenus, a 'ring' forming sedge dominant in grazed grassland, and the consequences for species coexistence. The structure of aboveground tussocks was described. A Lithium tracer assessed belowground distribution of functional roots. Seed rain and seedling emergence were compared for different positions in relation to Scirpus tussocks. Soil bioassays were used to compare growth on soil taken from inside and outside Scirpus tussocks of four coexisting species (Mentha acquatica, Pulicaria dysenterica, Scirpus holoschoenus and Dittrichia viscosa). We also compared plant performance of dominant plant species inside and outside Scirpus tussocks in the field. The 'ring' shaped tussocks of S. holoschoenus were generated by centrifugal rhizome development. Roots were functional and abundant under the tillers and extending outside the tussocks. The large roots mats that were present in the inner tussock zone were almost all dead. Seedling emergence and growth both showed a strong negative feedback of Scirpus in the inner tussock zone. Scirpus clonal development strongly reduced grass biomass. In the degenerated tussock zone, Pulicaria and Mentha mortality was lower, and biomass of individual plants and seed production were higher. This positive indirect interaction could be related to species-specific affinity to soil conditions generated by Scirpus, and interspecific competitive release in the degenerated tussock zone. We conclude that Scirpus negative feedback affects its seedling emergence and growth contributing to the development of the degenerated inner tussock zone. Moreover, this enhances species coexistence through facilitative interaction because the colonization of the inner tussock zone is highly species-specific.

Is plant biodiversity driven by decomposition processes? An emerging new theory on plant diversity

“…This has been reported for coastal sand dunes during primary succession (Van der Putten et al 1993), secondary succession and temperate grasslands (Bever 1994, Klironomos 2002, Bonanomi et al 2005b, and temperate (Streng et al 1989, Packer andClay 2000) and tropical forests (Webb et al 1967, Kiers et al 2000. In a literature survey, reported as Appendix to this paper, we found 138 experimental cases of plant-soil negative feedback on terrestrial ecosystems, but none for flowering plants and algae in marine and freshwater environments Appendix 1).…”

Islands of fertility induce co-occurring negative and positive plant-soil feedbacks promoting coexistence

“…Negative plant-soil feedback is defined as the negative condition for the establishment, growth, and reproduction of plants induced in the soil by the plants themselves. This has been reported for coastal sand dunes during primary succession (Van der Putten et al 1993), secondary succession (Brown and Gange 1992;De Deyn et al 2003), temperate grasslands (Bever 1994;Klironomos 2002;Bonanomi et al 2005b), and temperate (Streng et al 1989;Packer and Clay 2000) and tropical forests (Webb et al 1967;Wills et al 1997). Mechanisms proposed explaining this negative feedback include soil nutrient depletion (Berendse 1994;Ehrenfeld et al 2005), the build-up of soil-borne pathogen populations (De Rooij-van Der Goes 1995;Packer and Clay 2000), the changing community composition of soil microbial organisms (Bever 1994), and the release of allelopathic compounds during organic matter decomposition causing phytotoxicity (Singh et al 1999;Armstrong and Armstrong 2001;Bonanomi et al 2006a).…”

Assessing occurrence, specificity, and mechanisms of plant facilitation in terrestrial ecosystems

“…More recently, Callaway (2007, p. 160) pointed out that such plant-soil negative feedback has not been explicitly considered in the context of plant facilitation. New evidence from studies carried out in temperate grasslands (e.g., Klironomos 2002;Bonanomi et al 2005b) indicates that plant species can produce a mosaic of microsites detrimental to conspecifics, but beneficial to other species (review in Mazzoleni et al 2007;Kulmatisky et al 2008). The effects of such facilitative mechanism are cryptic, and can be assessed only by specific experiments (Klironomos 2002;Bonanomi et al 2005b).…”