International tree mortality network

Seminars

Online seminars

We are happy to announce our #8 ITMN seminar. It will take place on December 9th (1400 CET).

To attend the seminar, please use this registration link.

Information on past events and links to recordings can be found below.

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).

Past seminars

Our #7 ITMN seminar took place on November 23 2021 (1600 CET)  We are happy to announce our speaker: 

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 the recording of Yude’s presentation. Enjoy!

Our #6 ITMN seminar took place on June 22 (1700 CEST)  We are happy to announce our speaker: 

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 the recording of Craig’s presentation. Enjoy!

Our #5 ITMN seminar took place on May 6 (1700 CEST)  We are happy to announce our speaker: 

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 the recording of Lisa’s presentation. Enjoy!

Our #4 ITMN seminar took place on Mar 24 (900 MDT) We are happy to announce our speaker: 

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 the recording of Nate’s presentation. Enjoy!

 

Our #3 ITMN seminar took place on Feb 23 (900 Sydney) We are happy to announce our speaker: 

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 the recording of Belinda’s presentation. Enjoy!


Our #2 ITMN meeting took place on Jan 19 (4 pm, CET) and we are happy to announce our  speaker: 

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 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 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.