Record dry spells and effects on forests
"Associate Professor Cate Macinnis-Ng, School of Biological Sciences and Te Pūnaha Matatini, University of Auckland, comments:
“We often think about the devastating impacts drought can have on agriculture but forests and other ecosystems also suffer under drought. Around the world, there are growing records of forest dieback due to increasing frequencies and intensities of drought due to climate change. Here in Aotearoa, droughts don’t generally cause forest death because our droughts last months rather than years.
“While there are some examples of forest death due to drought in the literature, our ongoing research on kauri suggests their deep roots, stem water stores and conservative water use make this species well-prepared for dry periods.
“However, in the 2013 drought, we found that litter fall increased in kauri forest as kauri trees lost leaves to reduce leaf area and therefore save water. This type of response may complicate ongoing efforts to use remote sensing techniques to detect kauri dieback but continuing work at our experimental drought plot will help us tease apart canopy changes due to drought from canopy changes due to dieback.
“Interactions between kauri dieback impacts and drought are not clear. Dry conditions may prevent spread of the pathogen but when rain does arrive, trees weakened by drought may be vulnerable to infection.
“Established forests may be relatively safe from drought impacts, seedlings and restoration plantings are vulnerable as developing root systems of smaller plants do not have access to deep soil water stores. If drought continues for extended periods, carbon uptake may be reduced as plant productivity slows.
“Drier plant tissues are also more flammable so we all need to be especially careful with fire. The recent forest fires across Australia were exacerbated by drought and severe fire weather across large areas. While we are unlikely to suffer such catastrophic events here, we still need to plan carefully to protect forest and manage our water supply."
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