Mast Flowering Franklin Et Al
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North Queensland Naturalist 46 (2016) A mast flowering event in a eucalypt of tropical upland dry sclerophyll forest Donald C. FranklinA,B, Terry A. BarnesB,C and Alan WinlawB AResearch Institute for Environment & Livelihoods, Charles Darwin University, Darwin NT 0909, Australia and Ecological Communications, 24 Broadway, Herberton Qld 4887, Australia. Email: [email protected] BTablelands National Park Volunteers, PO Box 1250, Atherton Qld 4883, Australia CDeceased 22 Aug. 2015 Abstract Synchronised flowering of individuals of long-lived plant species at intervals of greater than one year, and which is bimodal between “much” and “few”, is known as masting. Masting appears to be common among eucalypts but has not been formally described as such. We provide quantitative data on a mass-flowering event in the Inland White Mahogany (Eucalyptus mediocris) in upland dry sclerophyll forest in north Queensland, along with anecdotal evidence that mass-flowering events in this species occur as infrequently as once per decade. Based on a survey of 549 trees spread across 37 sites, we estimate that 97% of healthy, mature Inland White Mahogany flowered between late November 2013 and February 2014, and 75% of these flowered heavily. Within the study area, flowering was staggered over about 12 weeks, with local synchrony being greater than regional synchrony. Fourteen percent of trees had capsules from a previous flowering event, and these trees displayed lower flowering effort than those without capsules. We argue that the event is appropriately described as masting. The factors driving masting in eucalypts are unknown, but this event may have been synchronised by a short but sharp drought 12 months prior. Copyright: © 2016, Franklin et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Handling editor: Stephen Murphy Citation: Franklin DC, Barnes TA, Winlaw A. 2016. A mast flowering event in a eucalypt of tropical upland dry sclerophyll forest. North Queensland Naturalist 46: 1-10. Introduction Many shrubs and trees flower and fruit annually trees in south-east Asia (Sakai 2002), a variety of and at a more-or-less set time of year, and if trees in New Zealand (Schauber et al. 2002), and a flowering varies in intensity from year to year, it is variety of plants elsewhere (Kelly and Sork 2002). It a direct response to limiting conditions in that has recently been described for a species of Mulga year. A few species, however, flower only at (Acacia aptaneura) and a species of Triodia in intervals of two or more years (supra-annually), central Australia (Wright and Zuur 2014; Wright et and if this is synchronised among individuals to al. 2014). produce major flowering events, it is known as Many eucalypts do not flower annually and stands masting. Masting is rarely a categoric state, may exhibit a periodicity of two to four years however, a more typical form being in which a few between major flowering events (Ashton 1975; individuals flower in most years but most Law et al. 2000; Birtchnell and Gibson 2006). In individuals flower together supra-annually (Kelly northern Australia, large variation between years 1994). Masting is well-known among dipterocarp in flowering intensity has been reported for Darwin Franklin et al.: eucalypt masting 1 North Queensland Naturalist 46 (2016) Woollybutt Eucalyptus miniata, Darwin Stringybark updated 2011, downloaded June 2013), and is E. tetrodonta and Long-fruited Bloodwood adopted here. However, in the Queensland Corymbia polycarpa (Setterfield and Williams 1996; Herbarium’s most recent checklist (Queensland Williams 1997; Brady 2009). Burrows and Burrows Herbarium 2014) and the official description of (1992) documented a “pattern of light and heavy Queensland’s regional ecosystems (REDD v8.0, seed production … over different years” in a http://www.ehp.qld.gov.au/ecosystems/ number of eucalypt species in the seasonally-dry biodiversity/regionalecosystems/how_to_ sub-tropical area of Rockhampton, Queensland. download_redd.html, downloaded 1 Jan. 2014), For the most part, the reported year-to-year white mahoganies in the Herberton area are variations appear to grossly exceed environmental known as E. portuensis. E. portuensis was described (e.g. rainfall) variation. Notwithstanding, the term by Hill (1999) as restricted to the vicinity of the “masting” has never, to our knowledge, been Whitsunday Passage on the central Queensland applied to eucalypts, though it is implicit in the coast, and we know of no published morphological predator satiation study of Eucalyptus delegatensis basis for interpreting white mahoganies in the by O’Dowd and Gill (1984). In seeming Herberton area as belonging to that taxon. confirmation of the latter point, a Web of Science In the Herberton area, Inland White Mahogany is search (http://thomsonreuters.com/thomson- widespread in dry sclerophyll forest on well- reuters-web-of-science/, 19 May 2014) on the drained granite- and metamorphic-derived soils, terms “eucalypt*” and “mast*” yielded not one and may be the most abundant eucalypt on these listing of relevance. It hardly needs stating that the parent materials. As mapped in Fig. 2, there is an dominance of eucalypts in the Australian landscape estimated 87.5 km2 of forest in which Inland White means that masting has major implications for the Mahogany is a primary species and a further variety of fauna that depend on them for nectar 121.25 km2 of forest in which it is secondary, the and seed. former mostly east of a line just west of Herberton In this paper we report on the timing and intensity and the latter mostly further west. (Areas of a mass-flowering event in Inland White Mahogany (Eucalyptus mediocris L.A.S.Johnson & K.D.Hill; but see below for issues with the naming of this taxon) in the Herberton area of north Queensland in 2013/14. We also provide anecdotal evidence that this was a “once-in-a-decade” event that strongly suggests masting. Methods Study species and area Inland White Mahogany (Fig. 1) is a member of the E. acmenoides (white mahogany) complex of species for which the taxonomy and nomenclature remains ill-resolved. Members of the complex in the Herberton area were known as E. acmenoides until Hill (1999) split the species and named local populations as E. irritans. The Centre for Plant Biodiversity Research (CPBR 2006) merged E. irritans into another species described by Hill, E. mediocris, arguing that “the type specimens are virtually identical and there are no consistent morphological differences between numerous herbarium specimens of the two.” CPBR’s resolution of this and other members of the Figure 1. Inland White Mahogany (Eucalyptus complex has been adopted by the Australian Plant mediocris): bark, foliage and flowers. Census (https://www.anbg.gov.au/chah/apc/, Photo: Don Franklin, Herberton, 12 Dec. 2013 Franklin et al.: eucalypt masting 2 North Queensland Naturalist 46 (2016) Figure 2. Distribution of survey sites and regional ecosystems featuring Inland White Mahogany (Eucalyptus mediocris) in the vicinity of Herberton, north Queensland. “Primary” and “Secondary” reflect the prominence of Inland White Mahogany in descriptions of regional ecosystems (DEHP 2014). Franklin et al.: eucalypt masting 3 North Queensland Naturalist 46 (2016) estimated by imposition of a 0.5 km grid on the of zero, less than 25% and greater than 25% of map [legend area excluded] and counting the the available reproductive organs. “flowers” intercepts, each intercept thus representing 0.25 were defined as any reproductive organ with km2 of vegetation.) Our sites (below) ranged in stamens present and “spent flowers” as any elevation from 850 to 1,050 m ASL, a range that is reproductive organ from which all stamens had probably representative of its local occurrence. dropped (i.e. various stages of developing Inland White Mahogany is often co-dominant with fruit). Lemon-scented Gum (Corymbia citriodora) with a . the extent of current-season reproductive number of other eucalypt species interspersed, but effort was scored relative to potential in at wetter, higher elevation sites it occurs with classes of 0 = 0%; 1 = 1–25%; 2 = 26–50%; 3 = Tindal’s Stringybark (Eucalyptus tindaliae, also 51–75%; 4 = 76–100%. Because buds are known as E. reducta). produced sub-terminally on leafy shoots, and leaves are confined to the outer portion of Field surveys shoots, this is effectively a measure of the On six days between 21 Dec. 2013 and 4 Jan. 2014, percentage of leafy shoots with reproductive we surveyed flowering of E. mediocris at 3 to 10 organs present, a measure that was readily sites per day, 37 sites in total, in open forests attributed to these abundance classes. within 12 km of Herberton (Fig. 2). On each day we . the presence of fruit (capsules) from a previous took a different route radiating out from flowering season, in classes of “none”, “few” Herberton, following roads and forest trails where and “many”. habitat was suitable. Sites were selected for their Consistently, sites and trees were selected and abundance of E. mediocris and were separated by data recorded by DCF, diameters measured by TAB, at least 0.5 km and mostly by at least 1.0 km. The and reproductive state assessed by AW. location and elevation of each site was determined using a GPS. At each site, we evaluated 15 trees (at Data analysis one site only 9 met our criteria), a total of 549 From our field data, the phenological state of a trees. For inclusion in the survey, E. mediocris had tree is rated in three classes representing buds, to meet the following criteria: flowers and spent flowers [fruit] respectively. For 1. be not adjacent to a major disturbance example, a tree with a phenological state of >25%, such as a road or cleared land; 0 and 0 is entirely in bud.