High Resprouting of Plants Within 16 Months of Wildfire in a Dry Grassland in Aotearoa New Zealand

Abstract

Wildfires are projected to increase in severity and frequency in dryland ecosystems due to climate change. To predict how plant communities will respond to these changes in wildfire patterns, it is vital to understand how plants establish following fire; such knowledge is limited in Aotearoa New Zealand. Individual plants regenerate after fire by resprouting or germinating from seeds. We aimed to quantify short-term community dynamics and regeneration strategies of plants after a wildfire in the eastern dryland zone in the Pukaki Scientific Reserve, Canterbury, Aotearoa New Zealand in August 2020. We established seven plots and recorded all vascular plant taxa present 1 and 4 months post-fire and again 16 months post-fire for two plots. Additionally, we used destructive sampling to determine whether individual plants had resprouted post-fire or germinated from seed. A total of 63 taxa were observed in the repeated surveys. Graminoids dominated at all times, particularly the exotic grasses Anthoxanthum odoratum and Agrostis capillaris. Species composition among the seven plots differed 1 month post-fire but tended to converge over 4–16 months. Woody species took longer to recover compared with forbs and graminoids. Of the 242 destructively sampled plants from 25 taxa, most individuals present after fire (215) had resprouted; six exotic taxa were the only ones to regenerate via seed. All six woody taxa resprouted. These results suggest that substantial changes in plant community structure occur 16 months after fire that is not evident in the first month, which has implications for management decisions. Further, while many native plants in this dryland zone can resprout post-fire, their lack of recruitment from seed may result in long-term shifts favoring exotic species under increased fire activity.