Ever since I was a child, I have been a nervous wreck of a person. I guess, with time, and the responsibilities of growing up, the nervousness and anxiety got worse. However, I was lucky enough to recognize I had a problem and did something about it. I received help from family, friends and counselors that all enabled me to become a little more resilient.
Resilience, I believe, is a crucial part of being human, as life isn’t always ‘hunky dory’. Some people are naturally resilient, others learn to be so by adapting to situations and changes in their lives.
The same applies for plants too. They might not feel the same emotions and hardships as we do, but they can be faced with extreme stress. With time, most plant species adapt to the stress or disturbances. When faced with similar situations again, they are able to deal better with the stress.
One such disturbance that many plant communities face too often in recent times is wildfire, as seen in the recent Australia bushfires. The flames burned through 19 million hectares, and killed about 1.25 billion animals. These are astronomical numbers, and only time will tell how Australia recovers (or IF it will recover at all), considering the unpredictable consequences of climate change.
Human-induced climate change is real (yes President Trump, it is!) and its effects are seen worldwide, including New Zealand. With severe fire weather predicted for NZ in the future, and given that NZ had infrequent natural fire activity, it is vital to figure out if the NZ flora is resilient enough to persist after a fire.
Ana Teixeira and colleagues wanted to investigate the resilience of NZ flora to fire by looking at a trait, called resprouting, in woody vegetation. Resprouting (the ability in plants to develop shoots or seeds after a disturbance) is one of the many vital fire protection functional traits in woody vegetation, along with heat or smoke-triggered germination and developing thick barks. The researchers addressed the following questions:
Can woody species in NZ that have evolved in a land with comparatively low fire occurrence resprout after a fire? Do the resprouting rates vary between species? How does species composition and abundance determine the resprouting rates within the local plant community?
There were two parts to the study; a literature review (to find out if there was any existing information on the resprouting ability of NZ species), and field work (studying burnt patches of native regenerating forest several months after an intense fire that occurred on the Port Hills in Christchurch in February 2017). All burnt woody plants of ≥ 5cm diameter and 30 cm above ground level were numbered, identified and any sign of resprouting was recorded for each of the identified plants.
If the resprouting rate in a species was ≥70%, it was considered as a strong resprouter, 30-70% it was an intermediate resprouter and species with rates ≤30% were classified as weak or non-resprouters.
In looking at previous studies, 73 species of NZ woody plant species were found to have resprouting abilities. All main species found in beech forests (Nothofagaceae), one of two main forest types in NZ, were classified as non-resprouters. The other main forest type, conifer-broadleaved forests mostly consisted of non-resprouters, with Agathis australis (kauri) an exception, though it is considered sensitive to fire.
In the field, 453 individual woody plants were evaluated, from 24 species (20 natives and 4 exotics). The resprouting rate increased from 17% at five months after the fire, to 38% at ten months after the fire. 92% of the sample was represented by the 15 most common species, of which three species were classified as strong resprouters, four as intermediate resprouters and eight as weak or non-resprouters. Melicytus ramiflorus (Whiteywood), was the most abundant species in the plots, and an intermediate resprouter.
The results tell us that, just like us, plant species take time to recover after facing adversity (as their resprouting ability increases after ten months).
Most of the native species in the field were classified as either weak or non-resprouters. This was not surprising, given the infrequent natural fire activity in NZ.
Species, such as Pseudopanax arboreus (Five Finger), Kunzea robusta (Kanuka) and some Pittosporum, were weak or non-resprouters but were found to be abundant in pre-fire vegetation. This poses strong implications for post-fire vegetation as they may not be able to recover to their original abundance, risking not being able to recover at all, which may be a threat to the biodiversity of that landscape.
Ana and her colleagues suggested that the resprouting response of some species may be dependent on fire intensity, as the resprouting ability declines with an increase in fire intensity. This makes sense as, no matter how good the intrinsic capability of a species is, if external conditions are very harsh (like a wildfire), the plant may not be able to live up to its capabilities. This can apply to us too. No matter how positive and strong-willed you may be, if you are burdened with too many “external conditions”, you may burn out (luckily, we do not literally burn out, as in the case of plants!).
Native species, such as Cordyline australis (NZ Cabbage Tree) and Fuchsia excorticata (Fuchsia), were found to be strong resprouters. The researchers recommended that these species may be used to help with restoration planting in areas with increased fire risk, such as the east side of the country (predicted to be windier, warmer and prone to increased periods of drought). Resprouters demand less active management. If plant species are persistent resprouters, they don’t need to be looked after as much as non-resprouters because these species are more prone to population loss.
They also suggested that native resprouter species that are low in flammability may be used as green firebreaks (strips of vegetation with low flammability that are strategically placed around a landscape to avoid widespread fire) to further help with native biodiversity restoration.
Using higher proportions of native low flammable and resprouter species, we can design NZ forests to be more fire resilient, while also being resistant to invasive species. Environmental conditions are proving to be increasingly unpredictable in future, and restoration projects using plant species identified in this study, may help to slow down the effects of climate change (such as increased temperature, winds and drought periods), helping our future generations.
The past cannot be changed, but we may have a shot at doing better in the future. Maybe NZ flora can become resilient (strong resprouters), as they begin to adapt to a severe fire weather. But we must lend a helping hand to our green friends. They do breathe life into us, after all.
I will leave you with one of my favourite quotes from the movie Mulan: “The flower that blooms in adversity is the most rare and beautiful of all”.
Tanmayi Pagadala is a postgraduate student completing a Master of Natural Resources Management and Ecological Engineering. She wrote this article as part of her assessment for ECOL 608 Research Methods in Ecology.