The Climatic Debt Explained

I guess some of you may wonder: what the hell is the climatic debt? Well, in ecology, this term is used to refer to communities of living organisms being in a state of disequilibrium with climate (cf. the equilibrium between community composition and climatic conditions has been disrupted). This is best illustrated by time-lagged response of living organisms to climate change. The inertia of long-lived organisms such as trees or perennial plants after a climate-forcing event makes forest ecosystems particularly prone to the climatic debt.

In a recent paper led by Romain Bertrand, we found that the magnitude of the disequilibrium with climate, aka climatic debt, in understory plant communities across the French forests (see map) increases with the severity of baseline temperature conditions, the exposure to climate warming and species thermal tolerance.

Bertrand_carteDetteClimHD_en

I’m really proud to write these few lines, not only because this is an important result (sorry I might be biased here) but mostly because it is always inspiring, rewarding and cool to work with a good buddy on a fun topic. Romain and I discussed this idea of “explaining the climatic debt” a very long time ago. It all started in 2011, few days after Romain’s original work on the assessment of the climatic debt in french forests’ understory plant communities was published. Well, we were not smart enough to use the fancy “climatic debt” at that time but reported it as “biotic responses lagging behind climate change” instead. Anyway, the thing is that we received a thorough (and inspiring) commentary from Pieter De Frenne and his colleagues arguing that the climatic debt we found in understory plant communities of temperate deciduous forests could be the result of changes in forest management practices. The reasoning behind this argument being that the abandonment of coppicing (a traditional sylvicultural practice in Europe: see picture below) and the subsequent natural succession towards mature close forests may provide microclimatic conditions that buffer understory plant communities against macroclimate warming. This is indeed a very important hypothesis and you can learn more on the potential importance of microclimate as a moderator of plant responses to macroclimate warming by reading the excellent paper written by Pieter De Frenne and his team. Although neither their commentary nor our reply was published, this was a fruitful discussion that has generated new and exiting findings.

The seminal analyses that we provided five years ago in our reply to the commentary just involved the respective impacts of macroclimate warming and changes in understory light conditions on the magnitude of the climatic debt and demonstrated that changes in understory light conditions had a minor impact on the climatic debt, as it is also the case in the now published paper. It would have been a shame to stop there given the efforts made to provide a convincing reply (we might have been too much convincing on this). So, we elaborated a list of the potential drivers involved in the climatic debt that we observed in understory forest plant communities. In that respect, Romain went far beyond our initial list and provided a very comprehensive (23 explanatory variables) analysis of the potential determinants of the climatic debt not only involving environmental (i.e. baseline conditions and exposure to environmental changes) and anthropogenic (e.g. sylvicultural practices, land-use changes, habitat fragmentation) constraints but also plant traits and characteristics involved in persistence (e.g. species’ life span and thermal tolerance) and migration (e.g. species’ dispersal limitation) mechanisms.

Although we expected climate-change exposure to be an important determinant (plants are more likely to lag behind climate change in locations where the magnitude of the change is the highest), we were very surprised to find that both baseline temperature conditions and species’ intrinsic ability to tolerate water and thermal stresses outweigh the impact of climate-change exposure. Warmer baseline conditions (cf. lowland forests at low latitudes) contribute to a high climatic debt and yet these ecosystems are usually given less priority than cold ecosystems (e.g. mountains) in conservation biology. Similarly, species’ persistence mechanisms as a response to climate change have been neglected so far due to the strong emphasis on migration mechanisms involved in climate-driven range shifts that are particularly pronounced along the elevation gradient where short distances between isotherms allow plants to move upslope. And yet, both lowland ecosystems and persistence mechanisms are very important to consider, especially so for forest plant which dispersal abilities are very limited. Consequently and importantly, persistence mechanisms outweigh migration mechanisms in explaining the climatic debt in forest ecosystems. We also note that lowland ecosystems and warm climates in general are richer in stress-tolerant plants, which could be a reason why warmer climates are more likely to harbour plant communities lagging behind climate change.

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Carpet of flowering bluebells (Hyacinthoides non-scripts) in a coppice dominated by beech (Fagus slvatica) and hornbeam (Carpinus betulus) (Vadencourt Wood, 80560 Contay, France). Due to its wide climatic-niche breadth and its affinity for moist and buffered microhabitats, bluebells likely contribute to increase the climatic debt in the understory (Photo: J. Lenoir).

Unfortunately, plants can only tolerate a limited amount of change in temperature conditions and future climate change projections suggest temperature increases that may go far beyond the thermal tolerance of plants, thus initiating local extirpation events with potential cascading effects for living organisms relying on these habitat-forming species.

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A Call for a Post-Doc Position in Ecoinformatics and Vegetation: Combining Remote Sensing and Field Data in a Toolbox to Map Non-Native Plant Distribution

Project aim:

IMAG3774

Saplings of Prunus seronita, a non-native plant, in a mixed Oak-Beech forest stand in Compiègne (France)

This postdoctoral position is part of a BiodivERsA project entitled “Detection of invasive plant species and assessment of their impact on ecosystem properties through remote sensing (DIARS)”. By combining field data together with two aircraft remote sensing technologies (hyperspectral imaging and light detection-and-ranging), DIARS aims at monitoring and modelling spread and risk assessment of invasive plant species at fine spatial resolution. Both remote sensing and field data are already available within the DIARS consortium for three different study sites (Belgium, France and Germany). The postdoc will develop a toolbox in a Free and Open Source environment (cf. R or GRASS GIS) to help end-users to combine both remote sensing and field data in a modelling framework that will allow mapping the invasion dynamic of non-native plants. More specifically, the toolbox will handle hyperspectral data preprocessing and classification, LiDAR data processing, species distribution modeling based on spatial proxies as well as field occurrences, and spatial representation of the uncertainty related to statistical modeling procedures. There will be many opportunities for independent and collaborative research in related areas of ecoinformatics.

Canopy_density

Canopy density derived from LiDAR data at 50-cm resolution across the entire Compiègne forest (144 km2) in northern France (Tarek Hattab)

The candidate is expected to have the following qualifications:

  • A Ph.D. in environmental sciences, computer sciences, statistics or mathematics;
  • Cutting-edge expertise in modeling and advanced statistical analyses;
  • Coding skills in Free and Open Source environments (R or GRASS GIS);
  • Basic knowledge and interest in plant ecology and biological invasions;
  • Experience in remote sensing;
  • Strong collaborative skills;
  • Proven abilities to publish at a high International level;
  • Good oral and written communication skills in English;
  • Ability to self-manage European project under European Commission, e.g. FP7.

Supervisors and collaborators:

The main supervisors are Dr. Jonathan Lenoir and Dr. Duccio Rocchini who are Associate Professor in Biostatistics and Researcher in Geographical Modeling and Spatial Ecology, respectively. The postdoc will work in close collaboration with Tarek Hattab, who is a Post-Doctoral fellow involved in DIARS, and will benefit from interactions with researchers in remote sensing (Dr. Ben Somers, Dr. Feilhauer Hannes, Prof. Sebastian Schmidtlein and Prof. Gregory Asner), conservation ecology (Prof. Olivier Honnay) and biological invasions (Prof. Guillaume Decocq).

Where:

Ecologie et Dynamique des Systèmes Anthropisés (EDYSAN), Jules Vernes University of Picardie, Amiens, France. EDYSAN is a young, diverse, vibrant and international research community with strong collaborative interdisciplinary ties within and beyond Amiens. More information about the people and research activities of the group can be here.

When:

The postdoctoral position should start at the latest on January 1st 2016. For further information, please contact: Dr. Jonathan Lenoir (jonathan.lenoir@u-picardie.fr).

Duration:

One year

Net salary:

2 100 EUR/month

Application deadline:

Please send your CV, including a list of publications, together with a cover letter and the contact information of 3 references to Jonathan Lenoir (jonathan.lenoir@u-picardie.fr). The application deadline is November 23rd 2015.

DIARS is funded by the ERA-Net BiodivERsA, with the national funders BelSPO,
DFG and ANR, part of the 2012-2013 BiodivERsA call for research proposals.

BiodivERsAANR

A Call for a Post-Doc Position in Ecoinformatics and Vegetation: Fine-Grained Modeling of Invasive Plants by Remote Sensing

Digital surface model of the tree canopy from the southern part of the forest of Compiègne (France). Emilie Gallet-Moron2-yr postdoc position in ecoinformatics: fine-grained modeling of biological invasions

This is a call for a PhD who is interested in either biological invasions, remote sensing or species distribution modeling. Applications are invited for a 2-yr postdoc position starting in late 2014 or beginning of 2015 in the research team “Ecologie et Dynamique des Systèmes Anthropisés (EDYSAN)”, based at Jules Vernes University of Picardie, Amiens, France. EDYSAN is a young, diverse, vibrant and international research community with strong collaborative interdisciplinary ties within and beyond Amiens. More information about the people and research activities of the group can be found here.

The successful applicant will be tightly involved in the BiodivERsA project entitled “Detection of invasive plant species and assessment of their impact on ecosystem properties through remote sensing (DIARS)”. By combining two aircraft remote sensing technologies (hyperspectral imaging and light detection-and-ranging), DIARS aims at monitoring and predicting spread and risk assessment of invasive plant species at fine spatial resolution. Focusing on three different study sites in Southern France, Belgium and Western Germany, the postdoc will use LiDAR-derived data to assess current and future distributions of three invasive plants: one moss (Campilopus introflexus); one perennial herb (Oxalis pes-caprae); and one tree (Prunus serotina). The postdoc will also be involved in an ecoinformatics initiative designing a toolbox to facilitate the use of remote sensing data for assessing and characterizing the ecosystem impacts of invasive plants in a Free and Open Source environment. There will be ample opportunity for independent and collaborative research in related areas of ecoinformatics.

The candidate is expected to have:

  • A Ph.D. in environmental sciences, computer sciences, statistics or mathematics;
  • Cutting-edge expertise in modeling and advanced statistical analyses;
  • Programming skills in Free and Open Source environments (R and GRASS);
  • Basic knowledge and interest in ecology;
  • Strong collaborative skills;
  • Proven abilities to publish at a high International level;
  • Good oral and written communication skills in English.

Experience in remote sensing, species distribution modeling, plant ecology or biological invasions would also be an advantage for the position.

The main supervisors are Dr. Jonathan Lenoir and Dr. Duccio Rocchini who are Associate Professor in Biostatistics and Researcher in Geographical Modeling and Spatial Ecology, respectively. The postdoc will benefit from interactions with researchers in remote sensing (Dr. Ben Somers, Dr. Feilhauer Hannes, Prof. Sebastian Schmidtlein and Prof. Gregory Asner), conservation ecology (Prof. Olivier Honnay) and biological invasions (Prof. Guillaume Decocq).

Please send your CV, including a list of publication, together with a cover letter and the contact information of 3 references to Jonathan Lenoir – jonathan.lenoir@u-picardie.fr