The International Tree Mortality Network, an
initiative of the IUFRO task force on monitoring
trends and patterns in global tree mortality,
continues the online seminar series on March
15, 4 pm CET, with:
Bonaventure Ntirugulirwa
Title: Mortality
of Afrotropical trees in a temperature
manipulation experiment: Result from the
Rwanda TREE project
Abstract: Knowledge on mortality
responses of tropical trees and communities
under projected warmer climate is limited. Trees
in tropical montane forests (TMFs) are
considered particularly vulnerable to climate
change, but this hypothesis remains poorly
evaluated due to data scarcity. To reduce the
knowledge gap on the warming response of TMFs,
we have established a field experiment along an
elevation gradient ranging from 2400 m a.s.l.
(15.2 °C mean temperature) to 1300 m a.s.l.
(20.6 °C mean temperature) in Rwanda. Twenty
tree species, native to East and Central Africa,
from two forest types of origin (transitional
rainforest at 1600 – 2000 m a.s.l, and TMF at
2000 – 3000 m a.s.l.) and two successional
groups, early (ES) and late succession (LS),
were planted in multispecies plots at three
sites along the gradient. Tree growth and
survival of 5400 trees was monitored regularly
over two years. The results showed that ES trees
from lower elevations grew faster at warmer
sites while several of the LS species,
especially from higher elevations, did not
respond or grew slower. Moreover, tree mortality
increased in a warmer climate and this was more
pronounced in high-elevation and LS species
compared to lower-elevation and ES tree species.
ES species with transitional rainforest origin
strongly increased in proportion of stand basal
area at warmer sites, while tropical montane
forest species declined, suggesting that
higher-elevation and LS species are at risk to
be outcompeted by lower-elevation and ES species
in a warmer climate. We conclude that tree
mortality and growth responses combined may lead
to modified tree community composition in a
warmer climate, favouring lower-elevation and ES
tree species. This has important implications
for biodiversity and carbon storage of
Afromontane forests.
Bio: Bonaventure Ntirugulirwa is a
research fellow in the Forest Productivity and
Improvement Program at the Rwanda Forestry
Authority of the Ministry of Environment in
Rwanda. He is a PhD candidate at the University
of Rwanda and at the University of Gothenburg in
Sweden. His research focus are native tree
species, their relation to ecological regions,
and the influence of climate change on growth
and mortality.
Note that the talks might be recorded.
Previous seminars:
Seminar # 1: Matt Hansen - Global forest
monitoring using satellite data
https://youtu.be/snUSGNb9bAQ
Seminar # 2: Flavia Costa - Tree mortality in
the Amazon across local hydrological
gradients: how water table depth may save or
condemn trees as climate changes
https://youtu.be/5wmzX9ldn4Q
Seminar #3: Belinda Medlyn - Tree mortality in
Australian ecosystems: past, present and
future
https://youtu.be/T6S9VKklbyc
Seminar #4:
Nate McDowell - Rising tree mortality in the
Anthropocene
Seminar
#5: Lisa Hülsmann - Tree mortality modeling –
a tool for ecological inference and a
challenge for projecting forest dynamics
Seminar #6: Craig D Allen -
The global emergence of hotter-drought drivers
of forest disturbance tipping points
Seminar #7: Yude Pan -
Impacts of disturbances on leaf area index and
productivity of terrestrial ecosystems
Seminar #8: Viacheslav
Kharuk - Conifer decline and mortality in
Siberia
Seminar #9: Barbara
Bentz - Recipes for Climate-Induced Bark
Beetle-Caused Tree Mortality
Seminar #10: Ana
Bastos - Climate variability, extremes,
and attribution of high-impact ecological
events: challenges and ways forward