Differences in Functional Trait Distribution Between Inselberg and Adjacent Matrix Floras

Hindawi Publishing Corporation International Journal of Ecology Volume 2016, Article ID 6417913, 7 pages http://dx.doi.org/10.1155/2016/6417913 Research Article Differences in Functional Trait Distribution between Inselberg and Adjacent Matrix Floras John T. Hunter School of Environmental and Rural Science, University of New England, Armidale, Australia Correspondence should be addressed to John T. Hunter; [email protected] Received 30 June 2016; Accepted 26 September 2016 Academic Editor: Bela´ Tothm´ er´ esz´ Copyright © 2016 John T. Hunter. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 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. 1. Introduction a worldwide distribution with replicate geomorphological structure [10–13]. Inselbergs are harsher and drier environ- Central to functional ecology is the ability to link changes ments compared to the matrix in which they are embedded. in species traits to ecosystem processes [1]. The distribution Inselbergs shed up to 95% of precipitation, the soils are skele- of functional traits is linked to the unique key evolutionary, tal, humic, and highly acidic [10, 12, 14–22]. Temperatures up ∘ ∘ environmental, predation, and competition pressures within to 18 C higher than the ambient air and in excess of 60 C a community. Functional traits determine how resources within the soil have been recorded; greater exposure to wind are secured and how those resources are allocated and/or and solar radiation means that the thin soils rapidly dry out stored, determining how species persist, compete, disperse, [16, 20, 22–25]. The vegetation around adjacent to the base coexist, and reduce loss from herbivory [2–6]. Comparisons of inselbergs receives increased moisture from runoff and of trait differences between community types can allow nitrogen loads from inselberg biofilms [26].udel B¨ et al. [26] for a more nuanced understanding of how traits and taxa showed that nitrogen content in the matrix soils adjacent to may redistribute under global climate change [6]. However, inselbergs was three times higher than the surrounding area. selection acts on individuals and not on individual traits These characteristics are inherent features of inselbergs and themselves indicating that it is a suite of coordinated traits their adjacent matrices worldwide [13]. that influence persistence, regeneration, and dispersal [7–9]. As granitic inselbergs have a less favorable environment While functional trait investigations are increasingly than the adjacent matrix in which they are imbedded, common, comparisons between the floras of adjacent but plants from such environments should develop persistence contrasting environments are lacking. Granitic inselberg life history traits [13, 27]. Species may persist in situ by environments offer “habitat islands” that contrast dramat- increasing the longevity of above ground parts, by increas- ically from the surrounding vegetated matrix and have ing the longevity of below ground parts or via dormancy 2 International Journal of Ecology mechanisms of diaspores [5, 7]. Benwell [28] and Clarke Table 1: Inselberg insular guilds as defined by McGann [12]. [29] suggested that vegetative reproduction (resprouting and clonality) was a stress tolerant regeneration strategy Guild Category of insularity compensating for high-risk recruitment and such strategies 0 Never found on inselbergs, taxa restricted to the should be more common in drought affected environments surrounding vegetation and thus favored on inselbergs. In contrast, Halassy et al. [30] 1 Taxa always found in surrounding matrix but in provided evidence that species that put greater resources into low abundance on inselbergs vegetative reproduction and/or storage organs were favored 2 Ubiquitous taxa found equally on inselbergs or under mesic, resource rich, and competitive environments. the matrix Taxa with shorter stature with larger seeds, smaller long-lived 3 Taxa common on inselbergs but occasionally leaves, longer lifespan, and denser wood are more likely to found in the surrounding matrix occur within areas of low resource availability compared to 4 Taxa restricted to inselbergs on the New England taxa from resource rich environments [5–7, 9, 31–33]. Batholith but found in other habitats elsewhere Although inselbergs are ideal “habitat islands,” how per- 5 Taxa restricted to inselbergs and other rock meable the barrier is between environments varies consider- outcrops throughout their distribution ably,andthussomeinselbergsareeffectivelymorefloristically 6 Taxa restricted to granitic inselbergs throughout insular than others [12, 34]. For example, within the New their distribution England Batholith of eastern Australia 76% of the granitic inselberg flora is shared with the surrounding matrix to varying degrees with overall endemism decreasing across the Hunteretal.[38,39],J.T.HunterandV.H.Hunter[40], landscape with increasing landscape aridity [12]. McGann Hunter [41], Hunter [42], and Hunter and Sheringham [43]. [12]createdasetofguildsbasedonrestrictiontotheinselberg Rainfall is seasonal and occurs mostly in summer (60– environment and Hunter [13] used these in an investigation 70%) with snow occurring occasionally at higher altitudes into the distribution of obligate seeding and resprouting life (Bureau of Meteorology http://www.bom.gov.au/). Rainfall history traits on granitic inselbergs and within the adjacent ranges from 600 to 1000 mm annually in the west and from matrix. 1000 to 2500 mm annually along the eastern escarpment Many species are likely to be uninformative in cross (Bureau of Meteorology http://www.bom.gov.au/). communityanalysesastheyarecommonlysharedtaxa with similar abundances across both environments. Here, 2.2. Survey Design. The survey was conducted using 32m selected trait expressions between taxa with high specificity × 32 m (c. 0.1ha)nestedplots(9nests;hencearelative to the granitic inselberg environment of eastern Australia are abundance score out of 10 was derived for each species within compared to taxa with specificity to the immediate adjacent each plot) [44] and collected solely by the author. A total of forested matrix based on the guilds of McGann [12]. Tested 399 plots were allocated to 216 inselbergs and 123 plots were traits include plant height, specific leaf area, fruit size, seed placed within the surrounding forested matrix. Full details of size, life form, regenerative capacity, phenology, dormancy, thesurveyprocedureandthestratificationofsitesaregivenin and dispersal. Due to the contrasts between these adjacent Hunter and Clarke [37]. In total 840 vascular plant taxa were vegetation types I hypothesized that inselberg endemics found within plots during April 1994 to June 1996. are likely to have long generation times, slow growth, and locally dispersed seeds and once established dominate spatial 2.3. Soil pH Determination. The pH of both matrix and resources as occurring with other persistence niche special- inselberg soils were tested at each site. The “1 : 5 Soil/Water ists [13, 27]. suspension method” of Raymont and Higginson [45] was used for determining soil pH. 20.00 g of air-dry soil and 2. Methods 100 mL of deionized water were placed within jars and tumble within a mechanical tumbler for one hour at room 2.1. Study Area. The New England Batholith lies in the north temperature. Solutions were allowed to settle for 30 mins. eastern corner of the state of New South Wales and the south Electrodes of a standardized pH meter were placed within eastern corner of the state of Queensland within Australia. solutions that were mechanically stirred until the reading The batholith extends for approximately 400 km north to settled. After each measurement electrodes were washed with southand110kmeasttowest[35].Elevationsarehigheston deionized water. Replicate determinations were periodically theeasternescarpmentandfalltowardsthewest.Surveyed made on the same solutions to ensure that readings did not areas varied in altitude from 310–1520 m above sea level. The vary within samples by more than 0.1 pH.

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