Dominant C₃ tussock grasses are resilient to the re‐introduction of fire in long‐unburned temperate grasslands

Abstract

Questions The recovery of dominant tussock grasses following fire is crucial as they contribute disproportionately to the structure and function of grasslands. To determine how resilient native grasslands are to the re‐introduction of fire, we quantify how fire affects the resprouting of the dominant C3 tussock grasses in long‐unburned grasslands (Austrostipa spp.) and compare this to the recovery of C4 tussock grasses (Themeda triandra) in grasslands that have had regular exposure to fire. We also quantify if these two grassland types burn in different ways as a result of their different dominant grass compositions. Location Temperate native tussock grasslands on the Victorian volcanic plain, Australia. Methods To determine how fire affects tussock mortality, and whether this differs between C4 (regularly ) and C3 (long‐unburned) grasslands, tussocks were permanently marked pre‐fire and re‐censused for survival and growth at seven weeks after fire. To assess whether C3 grasslands burn in a different way to C4 grasslands, fire behaviour was quantified at 11 sites. Results Fire behaviour was similar in both grassland types. Both C3 and C4 grass tussocks were resilient to fire, despite decades of fire suppression in C3 grasslands. Tussock mortality was low (<5%) in both C3 and C4 grasses. Survival was independent of basal circumference in C4 Themeda tussocks, but smaller‐sized tussocks (<10 cm circumference) were less likely to survive fire in C3 Austrostipa grasslands. Basal area declined in both grasses after fire but rate of tiller regrowth after fire was similar for both grass types. Conclusion Long‐unburned C3 grass tussocks were resilient to a single fire. Future studies should examine the response of C3 grasses to a fire regime that comprises frequent return intervals to which C4 grasses are resilient; this may indicate whether C3 grasses are sensitive to short fire‐return intervals despite resilience to an individual fire event.

Reducing herbicide input and optimizing spray method can minimize nontarget impacts on native grassland plant species

“…Grasslands in our study area are broadly classified as Natural Temperate Grassland but there is variation across the region in the composition of dominant grasses (Smith et al, 2018), reflecting variation in soil depth, nutrient status, and disturbance regime. This variation drives differences in grassland physical structure (Morgan & Salmon, 2020) and biodiversity (Smith et al, 2018). The composition of dominant grasses therefore influenced which reserves we targeted for the two experiments.…”

Perennial pasture grass invasion changes fire behaviour and recruitment potential of a native forb in a temperate Australian grassland

“…The highest fuel mass and residence times in grasslands observed in this study were those that had been invaded by an exotic pasture grass. While most native species in temperate grasslands regenerate from fire by resprouting (Lunt and Morgan 2002;Morgan 1999a;Morgan and Salmon 2020), elevated soil temperatures may reduce recruitment opportunities for new cohorts (Morgan 2001;Tomat-Kelly et al 2021) or potentially affect resprouting from underground storage organs or bud banks (Gagnon et al 2015;Pausas and Paula 2020). The residence time of fires may therefore influence the local distribution of species (Bond et al 2005;Keely et al 2011), as would an invasiondriven increase in fire residence time.…”

“…Socially, increased fuel loads and fire intensity pose risks to communities and infrastructure (Adams et al 2020); environmentally, changes in fire behaviour and increased soil heating may influence native plant species recruitment and persistence, with corresponding decreases in species diversity and regeneration postfire (Gagnon et al 2010;2015;Tomat-Kelly et al 2021). Recent studies in the region have assessed the variation in fire behaviour between native grassland types (Morgan and Salmon 2020), but no studies have investigated how exotic grass invasion into native grasslands may alter fire behaviour.…”

Social and Ecological Dimensions of Urban Conservation Grasslands and Their Management through Prescribed Burning and Woody Vegetation Removal

“…From the total pool of publicly managed grasslands in Melbourne (n = 80), sites were selected where (i) part of the site had been burnt less than one year ago ('recently burnt', n = 14) or (ii) the site contained a patch of woody vegetation (trees or large shrubs) ('woody plant halos', n = 9). In both cases, sites were only selected when they also contained a patch that had been burnt >3 years ago ('unburnt'), noting that the fire frequency in these grasslands was historically very high and fires were likely to occur every 1-3 years [57]. Areas within woody plant halos that had been burnt were not surveyed as there were not enough replicates to assess this treatment.…”