International tree mortality network

Seminars

Online seminars

The next seminar will be announced soon!

Past seminars

Our #12 ITMN seminar took place on April 26th (1600 CET).

Andreas Bolte


 

Forest mortality dynamics in Germany – how can we cope with it?

Abstract: In the last years forests in Germany haved faced vitality decreases and mortality dynamics never seen before. About 25% of German forests are projected to be at risk for extensive disturbance events and ecosystem service losses within the next 30 years; their transformation to future resilient forests will cost billions of Euros. Based on an analysis of ongoing mortality dynamics and options for an adaptive forest management, solutions for future forest management will be discussed.

Here is the recording of Andreas’ presentation. Enjoy!

Our #11 ITMN seminar took place on March 15th (1600 CET).

Bonaventure Ntirugulirwa

 

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.

Here is the recording of Bonaventure’s presentation. Enjoy!

Our #10 ITMN seminar took place on February 15th (1600 CET).

Ana Bastos

Climate variability, extremes, and attribution of high-impact ecological events: challenges and ways forward

Abstract: Climate and weather extremes impact tree functioning directly and can further trigger forest disturbances, thus affecting forest functioning and dynamics over periods much longer than the extreme per-se. With increased frequency or intensity of extreme events projected in the coming decades, extreme events might cluster in periods shorter than recovery times, thereby amplifying impacts and potentially inducing degradation and mortality trajectories. Understanding the links between atmospheric variability controlling extreme event occurrence and downstream impacts on forests is, therefore, crucial to: (i) separate trends in disturbance/mortality events due to natural vs. anthropogenically forced climate variability, (ii) improve process understanding about the drivers of high-impact ecological events and (iii) increase the robustness of future projections of forest dynamics.

Here is the recording of Ana’s presentation. Enjoy!

Our #9 ITMN seminar took place on January 25th (1700 CET).

Barbara Bentz

Recipes for Climate-Induced Bark Beetle-Caused Tree Mortality

Abstract: Globally, native bark beetles are contributing to increases in tree mortality and changes in climate are playing significant roles. Projecting future trends will be complicated by environmentally determined, evolved traits in both host trees and insects. Ingredients for bark beetle population success in future climates will be discussed.

Here is the recording of Barbara’s presentation. Enjoy!

Our #8 ITMN seminar took place on December 9 2021 (1400 CET).

Viacheslav Kharuk

Conifer decline and mortality in Siberia

Abstract: Conifer decline and mortality in the 21st century has been observed all over the boreal forests zone (e.g., Boyd et al., 2019), Europe (e.g., Hasenauer, & Seidl, 2017), and Russia (e.g., Kharuk et al., 2020). This report focused mostly on the causes of Siberian pine (Pinus sibirica Du Tour.) and fir (Abies sibirica Ledeb) decline and mortality in Siberia. In addition, recent insect (Zeiraphera griseana) and fungi (Melampsora sp.) attacks on the Larix sibirica stands are considered.

Results
1. Warming caused northward and uphill migration of the Siberian moth (Dendrolimus sibiricus Tschetv.) outbreaks range into the former pristine taiga.
2. Siberian fir mortality caused by the synergy of bark-beetles (Polygraphus proximus Blandford.) attacks and water stress.
3. Siberian pine and fir forest mortality preceded by trees growth index (GI) reduction caused by elevated air temperatures, acute droughts and following on insect attacks.
4. In mountains forest mortality observed mostly at low elevations, whereas within the areas with sufficient moisture availability (i.e., at elevations above ~1000 m) trees GI and forest area are increasing.
5. Consecutive years with elevated air temperature provoked immense insect (Zeiraphera griseana) outbreak within relatively dry larch habitat and fungi (Melampsora sp.) outbreak within moisture larch habitat.
6. With the projected drought increase, precipitation-sensitive Siberian pine and fir would retreat from its southern low elevation ranges and substitute by tolerant species (e.g., Betula spp, Larix sibirica, Pinus sylvestris).

Here is the recording of Viacheslav’s presentation. Enjoy!

Our #7 ITMN seminar took place on November 23 2021 (1600 CET).

Yude Pan

Impacts of disturbances on leaf area index and productivity of terrestrial ecosystems   

Abstract: An empirical model depicting the relationship between changes in leaf area index (LAI) and aboveground net primary productivity (ANPP) of terrestrial ecosystems provides an opportunity exploring these changes at a global scale. As LAI can be an effective indicator for ANPP, it also facilitates observations of larger scaled disturbances on terrestrial ecosystems and evaluating consequences in ANPP. These disturbances were originated from both human activities and natural forces. Human disturbances such as deforestation around tropical rainforests evidenced losses in LAI. Natural disturbances related to changing climate are recognisable from intensified wildfires and droughts, which left marks in fire-prone regions and extremely dry lands. Although elevated atmospheric CO2 appeared to have enhanced global ANPP, disturbances and relevant tree mortality caused 30% of vegetated lands with reduced LAI and 14% with decreased ANPP.

Here is the recording of Yude’s presentation. Enjoy!

Our #6 ITMN seminar took place on June 22 (1700 CEST).

CRAIG D. ALLEN

The global emergence of hotter-drought drivers of forest disturbance tipping points

Abstract: Current research is presented on global-scale patterns and trends of forest responses to increasingly hotter droughts, particularly extensive tree mortality and forest die-offs involving a range of interactive disturbances (e.g., water stress, insect outbreaks, high-severity wildfire). Diverse cross-scale observations and empirical findings increasingly indicate that amelioration of hotter-drought stress via fertilization of photosynthesis from elevated atmospheric CO2 concentrations may soon be overwhelmed by heat and accelerated atmospheric drought. These findings highlight some current challenges in realistically projecting the future of global forest ecosystems (and their associated carbon pools and fluxes) with process-based Earth system models. In particular there is substantial evidence that forests dominated by larger, older trees may be disproportionately vulnerable to increased growth stress and mortality under hotter-drought conditions. The fates of these old trees in response to global change are of vital importance, given that they are essential as: a) disproportionately large carbon sinks; b) among the most biodiverse and rare terrestrial ecosystems; c) irreplaceable archives of environmental history; and d) venerated for many cultural reasons. Key scientific uncertainties that impede modeling progress are outlined, and examples of promising empirical modeling approaches are illustrated.

Here is the recording of Craig’s presentation. Enjoy!

Our #5 ITMN seminar took place on May 6 (1700 CEST).

LISA HÜLSMANN

Tree mortality modeling – a tool for ecological inference and a challenge for projecting forest dynamics

Abstract: Tree death is ubiquitous in forests, even without climate change, and has a lasting impact on forest structure, species composition, biomass, and biodiversity. By relating tree mortality and other vital rates to tree, forest, and environmental conditions, we can therefore identify the mechanisms that govern the shape of forest ecosystems. In turn, these empirical relationships can be useful for projecting future forest dynamics and range limits of tree species. In the talk, I will discuss empirical tree mortality models as a diagnostic opportunity and a modeling challenge through two examples: the role of conspecific negative density dependence (Janzen-Connell effects) for tree diversity and the tighter coupling of dynamic vegetation models to forest data.

Here is the recording of Lisa’s presentation. Enjoy!

Our #4 ITMN seminar took place on Mar 24 (900 MDT).

NATE MCDOWELL

Rising tree mortality in the Anthropocene

Abstract: Tree mortality is rising in most documented locations but the drivers and mechanisms of this trend are unknown. Changes in atmospheric carbon dioxide, temperature, and vapor pressure deficit, along with drought, are primary potential drivers. Mechanisms linking these drivers to mortality include water, carbon, and pathogen defense processes. These processes are interdependent such that failure of one can lead to failure of the others. Prediction of future mortality is challenged by our understanding of the mechanisms, however, some evidence suggests the growing mortality rates are likely to continue well into the future. I conclude by reviewing the numerous challenges and opportunities for predicting future tree mortality.

Here is the recording of Nate’s presentation. Enjoy!

 

Our #3 ITMN seminar took place on Feb 23 (900 Sydney).

BELINDA MEDLYN

Tree mortality in Australian ecosystems: past, present and future

Abstract: Australia is not only the driest inhabited continent, it also experiences high interannual variability in rainfall, and severe multi-year droughts. Tree death from drought is thus a recurring feature of the Australian landscape. In this talk I will review our current understanding of drought mortality in Australian ecosystems, including the historical context, current field research on the extent and mechanisms of drought dieback and recovery, and the development of models to predict future drought mortality risk.

Here is the recording of Belinda’s presentation. Enjoy!

 

Our #2 ITMN meeting took place on Jan 19 (4 pm, CET).

FLÁVIA COSTA

Tree mortality in the Amazon across local hydrological gradients: how water table depth may save or condemn trees as climate changes

Abstract: Dr Costa will present results of 20 years of investigation on patterns of forest response to soil hydrology (more specifically water table depth) during normal and extreme climatic years to examine the hypothesis that shallow water tables buffer forests from droughts and forests in these conditions may even be benefited by droughts. Dr Costa will also present some data on the hydraulic trait distributions along hydrological gradients to analyse the shifting implications to mortality during moderate to strong droughts.

Here is the recording of Flavia's presentation. Enjoy!

Our kick-off meeting was taking place on Nov 17 (5 pm, CET) with our first speaker:

MATT HANSEN

Global forest monitoring using satellite data

Abstract: Earth observation data enable the monitoring of forest extent and change from national to global scales. Consistent processing of time-series images has made possible the operational production of global tree cover extent, loss and gain products.  However, attribution of dynamics in the context 1) reference state, for example forest type, 2) change factor, for example fire or logging, and 3) outcome, for example land use type or natural recovery, is more challenging.   In addition to mapping, the requirement to perform robust sample-based analyses to report on all themes is underappreciated.  This talk will review our work on characterizing forest dynamics at the global scale using multi-source satellite imagery, including mapping and sampling, in the context of current operational versus future aspirational capabilities.

Here is the recording of Matt's Seminar. Enjoy!

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Past Workshops

Virtual Tree Mortality Workshops 2020

We organize a series of virtual discussions to merge and harmonize different data sources on tree mortality.