Differences in Functional Trait Distribution between Inselberg and Adjacent Matrix Floras

Abstract

Inselbergs and the adjacent matrix represent extremes of different environmental conditions and should shed light on the changing allocation of plant resources across strong and abrupt resource gradients. Here I use collated life history trait data from 840 taxa found within typical insular inselberg and adjacent matrix floras from the New England Batholith region of eastern Australia. These species were sorted into guilds of specificity to the inselberg environment. Scored traits include life form, plant height, leaf area, fruit size, seed size, mono-or polycarpy, underground storage organs, regenerative/clonality, and flowering phenology. With reduced water and nutrient resources, typical of inselbergs, allocation of plant resources to vegetative reproduction and storage organs is a disadvantage. Plants restricted to inselbergs were shorter, usually polycarpic shrubs, with smaller leaves, fruits, and seeds. Flowering time was found to be earlier and reduced in length; diaspores often have dormancy and are dispersed locally in comparison to the matrix. The results show that with limited resources the creation of underground storage organs or vegetative reproduction becomes unviable on habitats characterised by shallow soil. Inselberg taxa of the study region are likely to be under greater threat than the matrix due to anthropogenic climate change.

The Effects of Fire and Manual Biomass Removal on the Vegetation of Granite Inselbergs

“…Thus, successive fires cause inselberg floras to be less distinctive and less insular from the surrounding matrix. Inselberg floras are often reported as refuge areas for species unadapted to fire, and these findings support this concept (Heinze et al 1997;Lawler et al 1998;Hopper 2000;Hunter 2003bHunter , 2016. Species richness per plot (density) is often used as a surrogate for understanding the potential benefits of fire to the biodiversity of a community (Russell and Parsons 1978, Clarke 1988, Ross et al 2002, Etherington and Shapcott 2014.…”

“…The flora of inselbergs within eastern Australia are highly con-generic with other heaths and shrublands of the region and the encompassing matrix (Clarke 2002a(Clarke , 2002bHunter 2003bHunter , 2004. This has led to the assignment of prescribed fire regimes from structurally similar, but potentially evolutionarily and floristically dissimilar floras (Hunter 2016), to inselberg vegetation (Bradstock et al 1995, Clarke and Fulloon 1999, Keith 2004, Kenny et al 2004. The island nature of the inselbergs stranded within, but above and separate from, the surrounding matrix imposes physical differences that change the nature, behavior, and effect of fire within the landscape.…”

“…Even if one patch burns, often only under conditions of a high intensity matrix fire, there is a high likelihood it will not reach an adjacent patch on the same inselberg. It is therefore not surprising that available evidence suggests inselberg floras may not be fire adapted, unlike other structurally similar heath-like communities in eastern Australia (Ashton and Webb 1977;Fuls et al 1992;Groger and Barthlett 1996;Hopper et al 1997;Lawler et al 1998;Hunter 2003aHunter , 2016. Disturbances such as fire are important in structuring plant communities and have the potential to influence the occurrence and density of species within a community (Keith 2004, Croft et al 2015.…”

“…Fires, for example, affect vegetation directly and indirectly by killing some organs or plants and stimulating others (Williams and Gill 1995). Anecdotal observations suggest that increasing fire frequency on inselbergs of the NEB to that of other heaths may cause significant floristic change, reducing the number of endemics and obligate seeders in favor of resprouting generalists (Binns 1992, Hunter 2016.…”

Beta diversity patterns of Bromeliaceae growing on rocky cliffs within the Atlantic Forest in southern Brazil

“…The physiological sensitivity and performance of bromeliads are directly related to their thermal tolerances (Benzing 2000), which also corroborates the importance of this variable. Recently, studies have shown differences in the anatomy and morphology of epilithic species, reinforcing the existence of different adaptations in certain species to deal with drought in rocky environments (Hunter 2016, de Paula et al 2019. Many bromeliads are adapted to environmental conditions with low water availability, being favoured by several functional attributes capable of efficiently capturing water and minimizing its loss.…”