Underground storage organs (USOs) allow many perennial herbaceous plants to survive disturbance and seasonal stress by storing resources that support resprouting. However, the cost of disturbance may depend strongly on when it occurs relative to plant phenology and resource allocation cycles. In temperate grasslands, prescribed fire has historically been applied during summer or autumn when many herbaceous species are dormant. Increasing use of spring burns means fire can coincide with active growth and reproduction; yet, the implications for USO-dependent species remains poorly understood. We tested how burn season influences growth and belowground resource dynamics in four perennial species common to temperate native grasslands. Plants were subjected to simulated fire treatments in either spring (during active growth) or summer (after the main growth season). USO dry mass was measured as a proxy for stored resources, and post-fire phenological responses were monitored to assess the effects of subsequent growth and reproduction. Responses varied among species. Eryngium ovinum (Apiaceae) and Arthropodium strictum (Asparagaceae) rapidly resprouted after spring burning, and in some cases, reproduced within the same growing season. Summer burning coincided more closely with their vegetative dormancy. Both species generally had lower USO biomass following spring burns than summer burns. In contrast, Burchardia umbellata (Colchicaceae) and Bulbine bulbosa (Asphodelaceae) showed little within-season resprouting after spring fire and no clear differences in USO biomass between treatments. These findings indicate that the timing of fire can interact with species-specific phenological strategies to influence the costs of resprouting from underground storage organs.
Context The multidecadal response of treeless subalpine vegetation on fertile sites in Lutruwita/Tasmania to the exclusion of vertebrate grazing animals might be expected to mirror the transition from grassy shrubland to complete vegetation cover dominated by tall herbs and grasses, as documented for alpine vegetation in the Australian Alps. Aims To determine whether long-term protection from vertebrate herbivore grazing results in a transition from treeless subalpine grassy shrubland to tall alpine herbs and grassland. Methods We conducted repeat sampling in treeless subalpine vegetation at a long-term monitoring site on Liawenee Moor, Lutruwita/Tasmania. Vegetation surveys were conducted in 20, 5 m × 5 m quadrats, and along 20, 10 m line transects in a vertebrate grazing exclosure in 1997, 2011, and 2018. Data on species presence and cover and the cover of lifeforms were used to track changes in vegetation over time. On-ground vegetation surveys were supplemented by drone imagery in 2022 to measure changes in the cover of the dominant shrub, Grevillea australis, across the whole experimental site. Key results The large shifts in species composition and cover from 1997 to 2018 were not in accordance with the expected trajectory, from shrub-dominated to herbaceous vegetation. Cover of both tall shrubs and tall herbs declined over time, whereas grass cover remained constant. There was no corresponding increase in cover for any lifeform groups that could account for the decline in litter. Overlapping vegetation cover decreased significantly over time, with most of the change in this variable occurring between the first two sampling periods (1997 and 2011). Changes in frequency and cover of individual species was variable within lifeform groups; however, the frequency of several short herbs decreased dramatically between 1997 and 2011. Warmer temperatures and soil moisture deficits are likely to be partly responsible for changes in vegetation over time. Conclusions After 50 years of vertebrate herbivore exclusion there is little evidence to suggest that the ungrazed full exclosure plot at Liawenee Moor is transitioning from a shrub-dominated community to one that is dominated by tall herbs and grasses. Overlapping vegetation cover was significantly lower in 2018 than in 1997, most likely related to the reduction in cover of the dominant shrub, G. australis. Climate signals such as warmer minimum temperatures in combination with soil moisture deficits during the growing season, may be partly responsible for changes in vegetation. The decline in cover of G. australis across the experimental site, regardless of grazing treatment, maybe a response to drought and has been observed in shrubs elsewhere on the Central Plateau and in the Australian Alps. Observed declines in some smaller-statured plants may also relate to soil moisture deficits and increasing air temperatures. Further monitoring of the whole experimental site, including the plots subjected to grazing, will help disentangle the impacts of a warming climate from responses to grazing pressure. Implications This is one of the oldest long-term monitoring sites in Lutruwita/Tasmania and is important for investigating changes in vegetation dynamics under a warming and drying climate.
Context Monoecy is a sexual system observed in slightly more than 7.0% of flowering plant species where individuals produce distinct male and female flowers on the same plant. Understanding the life history and climate conditions associated with monoecious species may reveal the survival advantages and opportunities for conservation for this rare reproductive system. Aim To identify monoecious species in central southern Australia, determine their life history and climate associations and map their proportional species richness by Interim Biogeographical Regionalisation of Australia (IBRA) subregions. Methods Monoecious species and life history trait data were identified from online Flora of South Australia (eFlora), the Flora of Australia or relevant peer-reviewed research. Proportions of monoecy were determined for 66 contiguous IBRA subregions in semi-arid south-east Australia using Australasian Virtual Herbarium collection records, as well as subregion climate averages using Terrestrial Ecology Research Network raster data. Generalised linear mixed-models were applied to determine associations between proportion of monoecious and climate. Key results Non-woody growth forms and abiotic pollination were associated with monoecy, as well as extremes of daily temperature and higher number of sun hours. Conclusions The occurrence of monoecy between subregions indicates that this reproductive system may confer greater survival advantages than dioecy in desert habitats where resources and reproductive assurance are limited. Implications With these new data, monoecious plants can be studied and conserved in the systems where they are most prevalent and may have fitness advantages compared to other plant sexual systems.
Context Cultural fire has recently been returned to semi-arid grasslands on Dja Dja Wurrung Country in southern Australia. However, its ecological effects on plant species in these modified grasslands have not been previously documented. Aims To assess the response of Maireana species to the return of a cultural fire regime in a long-unburnt grassland. Methods We measured the density, height, and proportion of fruiting of two Maireana species across three fire treatments (burnt twice, burnt four times, and long-unburnt) at a semi-arid grassland in central Victoria, Australia. Data were collected from 10 4-m2 quadrats per treatment. Key results Cultural burning significantly increased the density of two Maireana species compared with the unburnt treatment. For Maireana enchylaenoides, both plant height and fruiting proportion were significantly higher in the burnt treatments than in the unburnt treatment. While Maireana humillima showed no substantial height differences among treatments, the proportion of fruiting individuals was significantly greater in the burnt treatments. Conclusions Cultural fire promotes favourable conditions for Maireana species, enhancing both density and reproductive output. Implications This study has highlighted the potential of cultural fire to support the recovery of native grasslands where First Nations management has been disrupted, increasing native plant species abundance. Contrary to previous assumptions, both Maireana species resprout after fire and thrive under frequent low-intensity burning.
