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Precipitation variability and heatwaves are expected to intensify over much of inland Australia under most projected climate change scenarios. This will undoubtedly have impacts on the biota of Australian dryland systems. However, accurate modelling of these impacts is presently impeded by a lack of empirical research on drought/heatwave effects on native arid flora and fauna. During the 2018–2021 Australian drought, many parts of the continent's inland experienced their hottest, driest period on record. Here, we present the results of a field survey in 2021 involving indigenous rangers, scientists and national parks staff who assessed plant dieback during this drought at Uluru‐Kata Tjuta National Park (UKTNP), central Australia. Spatially randomized quadrat sampling of eight common and culturally important plants indicated the following plant death rates across UKTNP (in order of drought susceptibility): desert myrtle (Aluta maisonneuvei subsp. maisonneuvei) (91%), yellow flame grevillea (Grevillea eriostachya) (79%), Maitland's wattle (Acacia maitlandii) (67%), waxy wattle (A. melleodora) (65%), soft spinifex grass (Triodia pungens) (53%), mulga (A. aneura) (42%), desert oak (Allocasuarina decaisneana) (22%) and quandong (Santalum acuminatum) (0%). The sampling also detected that seedling recruitment was absent or minimal for all plants except soft spinifex, while a generalized linear mixed model (GLMM) indicated two‐way interactions among species, plant size and stand density as important predictors of drought survival of adult plants. A substantial loss of biodiversity has occurred at UKTNP during the recent drought, with likely drivers of widespread plant mortality being extreme multi‐year rainfall deficit (2019 recorded the lowest‐ever annual rainfall at UKTNP [27 mm]) and record high summer temperatures (December 2019 recorded the highest‐ever temperature [47.1°C]). Our findings indicate that widespread plant death and extensive vegetation restructuring will occur across arid Australia if the severity and frequency of droughts increase under climate change. [ABSTRACT FROM AUTHOR]

Questions: Buffel grass (Cenchrus ciliaris L.) is a drought‐adapted invasive plant that has become a serious environmental weed in many arid and semi‐arid systems. This paper examined whether eradication of buffel grass infestations: (i) increases frequency, richness and diversity of native vegetation and seed bank pools; and (ii) improves availability of seed resources for granivores. Location: Alluvial ironwood/corkwood woodlands in arid central Australia. Methods: We assessed differences in floristic and seed bank composition between buffel‐infested sites and sites where buffel grass had been eradicated ca. 12 years previously. Plant species frequency data from nested‐quadrat sampling were amalgamated into plant functional groups to examine their relationship to buffel treatment. A seed flotation method was employed to: (i) assess seed bank composition of functional groups at eradicated vs. infested sites; and (ii) test whether the mass of seeds available for granivores was higher at buffel‐free sites. Results: Buffel‐eradicated sites supported richer and more diverse vegetation and seed banks across all functional groups except perennial grasses. The effect was strongest for perennial forbs, annual/short‐lived forbs, and annual/short‐lived grasses. The overall mass of seeds of non‐buffel grass species was ca. 10‐fold higher at buffel‐removed sites. Numbers of seeds of species in the 0.001–0.009 9 g and 0.000 1–0.000 99 g size classes, both of which contain species with seeds consumed by granivores, were ca. 20‐ and 14‐fold higher respectively at buffel‐removed sites. Conclusions: Buffel grass removal at localised scales provides islands of habitat with improved opportunities for native plant re‐establishment and abundant foraging resources for granivores. Future research must disentangle the relative importance of dispersal vs. residual seed banks for community restoration after buffel grass invasion. Extended delays in eradication could allow seed bank reserves to deteriorate to a state that no longer permits regeneration. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Fire typically triggers extensive regeneration of plants with heat-stimulated germination by causing short periods of intense soil heating. If plants with heat-stimulated germination are also subject to seed predation and display mast-seeding cycles, postfire recruitment may be contingent on the seedfall density of prefire masts, and on whether granivores are satiated at the time of fire. METHODS: We conducted a longitudinal seedbank study and a mensurative field experiment in central Australia to examine whether fire and the variation in seedfall density across sites in a mast year interact to influence recruitment of slender mulga (Acacia aptaneura), an iteroparous masting shrub with heat-stimulated germination. KEY RESULT: The seedbank study showed seedbank pulsing after masting, with mean seed counts in the upper 4-cm soil layer being 132.8 seeds/m2 12-mo after a dense seedfall, but only 3.8 seeds/m2 following a year with no seed production. Consistent with this, recruitment increased postfire at sites where denser seedfall had occurred during the preburn mast year. Conversely, little recruitment occurred at unburnt populations, irrespective of prefire seedfall density. CONCLUSIONS: We attribute our findings to: (1) elevated soil temperatures during fires stimulating germination of heat-cued seeds; and (2) granivore satiation following masting facilitating assimilation of seeds into the soil seedbank. These results highlight the importance of rare seed-input events for regeneration in fire-prone systems dominated by masting plants, and provide the first example from an arid biome of fire interacting with masting to influence recruitment. [ABSTRACT FROM AUTHOR]

Questions: The relationship between fire, aridity and seed banks is poorly understood in plant community ecology. We tested whether there was a close correspondence between the seed bank and standing vegetation composition with time-since-fire in a desert. We also examined whether longer-lived species showed seed limitation relative to more ephemeral species, as this could influence grass-woody ratios in a major biome. Location: Dune hummock grasslands/shrublands of central Australia. Methods: The effects of time-since-fire on floristic and functional group composition were examined by comparing plots unburned since 1984 against plots that had been burned in 2002. Three methods were used to quantify seed abundances: a germination trial using heat and smoke application, a flotation method, and a sieving method. Results: Seed bank densities were very low (<3000 m−2). Species similarity between the seed bank and standing vegetation was high at sites recently burned (0.86) and low in sites long-since burned (0.52). The relative abundance of ephemeral species in the seed bank peaked in recently burned plots, but the relative abundance of seeds of woody species did not match the pattern of abundance in the standing vegetation. Remarkably, the dominant perennial grasses and woody species were either absent from the seed bank or present at extremely low abundances. Discussion: Differences in the relative abundance of ephemeral species between standing vegetation and seed bank relate to the post-fire succession process. The small soil pool of seed from woody species may be explained by allocation to belowground carbohydrate storage over seed production. Field observations suggest, however, that production of strongly dormant seed can be prolific and that high levels of seed predation make this system strongly seed-limited. The discovery of this seed bank syndrome indicates that shifts in grass-woody ratios can be driven by the juxtaposition of unpredictable seed rain and fire events in these desert dunes. However, estimates of grass-woody ratios due to changing fire regimes will be difficult to predict. [ABSTRACT FROM AUTHOR]