Resprouting habits of cyclone damaged trees of the Miombo

Cyclone Idai made landfall in Mozambique, March 2019. Cyclones of Idai’s proportion (greater than category 3) are notorious for causing considerable damage to vegetation, often felling large trees (>10 cm diameter and with the potential to grow beyond 40 cm diameter) in their path. As part of the FEFA research program working to quantify the resilience of African woodlands through understanding the recovery dynamics of these woodlands, we are studying how agents of above-ground biomass removal (top-kill) impact large tree populations and subsequently how these populations persist (or not), particularly through resprouting. In July 2024, I joined a team of Socio-Ecological Observatory for Studying African Woodlands (SEOSAW) researchers, monitoring cyclone Idai damaged trees in long-term monitoring plots located in the Miombo woodlands of Gorongosa National Park.

Cyclone Idai is one the most destructive tropical cyclones ever recorded in the Southern Hemisphere, previous research indicates that the cyclone hit the park, felling and damaging 4% of the sampled tree population (in the eight monitored) 1hectare plots, and considerably affecting larger trees of the dominant species. My goal for this field survey, was to collect information that would enable us to quantify the resprouting propensity of cyclone top-killed trees in these ecosystems. In addition to the tree stem monitoring data already collected through the SEOSAW stem protocol, I collected information noting whether top-killed trees resprouted or not, mode of resprouting (trees will resprout from the base of the trunk, from the stem or through root suckering), the size of the resprouting stem etc. During this field season, we also tested out a resprouting protocol that we hope to incorporate into the SEOSAW stem monitoring protocol.

We could learn a considerable amount on recovery dynamics of Africa woodlands from the rich network of SEOSAW plots scattered through the African region. However, at the moment, many researchers within the network are not collecting information on resprouting dynamics and those that are might not be collecting the same information that can be easily combined for answering questions at a regional scale. With the protocol, our aim is to identify the most basic information that be can easily collected without spending too much additional time in the field and still help us answer these pressing questions around recovery of a arge trees post top-kill events. Additionally, this way we ensure that researchers are collecting data the same way and nothing is left to interpretation. Resprouting habits of Miombo trees: Fezile, SEOSAW researcher recording her first ‘proper’ root suckering tree from Millettia stuhlmannii. Cyclones are just one of six top-kill agents that we are studying in this multi-facetted project looking at top-kill and resprouting dynamics of African woodlands.

Over the past couple of years, we have also synthesized information on elephant, fire, frost, drought and human mediated tree top-kill. We have seen that most of these agents play an important role in shaping the population structure of trees even when trees have gotten big and are no longer threatened by fire. From an ecological perspective, our goal is to underscore the significance of top-kill and resprouting in the life history of savanna trees, such that we can think more clearly around regeneration of these tree species and inform vegetation modelling.

Dr Fezile Mtsetfwa is a Post-Doc researcher at the School of Animal Plant and Environmental Sciences at the University of the Witwatersrand. She holds a PhD in Interdisciplinary Ecology with research interests in plant ecology, global change ecology and conservation of large trees and biodiversity in savannas. Her current research with the FEFA program studies spatial and temporal distributional patterns of tree biomass removal- top-kill by fire, frost, drought, cyclones elephants, and humans, and investigates tree resprouting dynamics post top-kill. This work will make a significant contribution to filling the huge gap in understanding regeneration rates of African woodlands that is essential for understanding savanna ecosystem resilience and tipping points in both tree harvesting practices and the global carbon cycle.

Contact:
Dr Fezile Mtsetfwa – Post-Doctoral Researcher, School of Animal Plant & Environmental Sciences, University of the Witwatersrand
Email: Fezile.mtsetfwa@wits.ac.za
X: @FMtsetfwa

Related Posts Read on more of Fezile’s work on “Tree resprouting responses to charcoal harvesting in the Miombo woodlands of Zambia”, here.

Future Ecosystems For Africa

A unique opportunity for an Africa-led, Africa-centred program, which can influence thinking and action in novel, as yet unexplored ways