Journal Article

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

Decocq, Guillaume, Salmon, Karina L., Morgan, John W.

2020

Overview

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. To determine the resilience of C3 tussock grasses to the re‐introduction of fire, we quantified resprouting capacity of Austrostipa spp. Long‐unburned C3 tussocks were resilient to a single fire. Future studies should examine the response of C3 tussocks to a fire regime to determine whether they are sensitive to short fire‐return intervals despite resilience to an individual fire event.

• Publisher: Wiley Subscription Services, Inc
• Subject: Australia / Austrostipa / C3 plants / C4 grasses / C4 plants / Circumferences / fire behavior / Fire exposure / fire intensity / fire regime / fire suppression / Grasses / grassland fires / Grasslands / indigenous species / Intervals / Mortality / Recovery / Regrowth / resprouting / Structure-function relationships / Survival / Themeda triandra / tussock grasses / tussock grasslands / tussock mortality