Rationale

The microclimate in the understory is an essential component of many services provided by forests. This is because forest canopies are able to buffer climate extremes; in particular, the understory microclimate temperature is usually cooler than the macroclimate temperature2 during the day and in summer, and warmer at night and in winter (De Frenne et al., 2019; Zellweger et al., 2019a). Several recent studies show that this buffering capacity is essential for understanding forest biodiversity dynamics because understory communities (plants, insects, fungi, etc.) respond to microclimate more than macroclimate change (De Frenne et al., 2013; Zellweger et al., 2020; Williamson et al., 2020). This capacity of forest canopies to buffer climate extremes is equally important for explaining the dynamics of forest regeneration and thus their resilience to climate change. It is also important for recreational activities, especially during heat waves in urban areas.

Forest management practices impact these different services, for better or worse, by modifying forest structure and composition and thus important factors governing understory microclimate. Today, however, forest managers have a limited toolkit to quantify the impact of their practices on understory microclimate. Recommendations to fight against biodiversity loss (leave stumps and residues in place, create islands of deciduous trees, maintain tree species diversity, etc.) remain rather qualitative. These recommendations are not necessarily well followed because they seem to work against other management objectives such as wood production or fire prevention. To provide better guidance to forest managers, we need tools that can quantify the impact of management on understory microclimate now and in a future climate.

Overall objective and long-term goal

The objective of this project is to develop observation-based tools to identify the main factors influencing forest understory microclimate, and biophysical and ecological models to anticipate the impact of forest management (density, fragmentation, thinning, choice of species, understory removal, etc.) on forest microclimate and understory vegetation, notably in terms of climate extremes (drought, heat wave, late frost, flooding, etc.) under future climate change scenarios. These tools and models will be key to help forest managers increase the resilience of forests and foster their ecological, recreational and climate services in a warming world.

Project organisation

We structured the scientific programme within MaCCMic around three rather independent scientific work-packages (WPs 1-3, Table 2), each focusing on a different research hypothesis, while a fourth work-package (WP0) is devoted to project coordination and dissemination. A short description of the scientific work-packages (WPs 1-3) is provided below.

WP1 | Impact of canopy structure and functional diversity on understory microclimate

This workpackage will focus on the impact of canopy structure and functional diversity on understory microclimate, in particular during drought, to test hypothesis (H1) that, beyond canopy cover, both canopy structure and plant functional diversity are important factors that influence the buffering capacity of forest understory microclimate and its decoupling from regional macroclimate, and that their relative importance increases with drought severity and duration. It involves all partners and will consist in two initial and independent tasks (Tasks 1.1 and 1.2) and two more dependent ones (Tasks 1.3 and 1.4), with possible feedbacks on the other initial tasks (notably for the deployment of new sensors in specific locations).

WP2 | Impact of landscape features on understory microclimate

In this work package, we will focus on the impact of landscape features on understory microclimate, in particular forest fragmentation and distance to water bodies, to test hypothesis (H2) that the microclimate in forest understory depends on landscape features such as the amount of forested area of the surroundings and its degree of fragmentation (i.e. woodland fraction within a given radius, average patch size, etc.).

WP3 | Impact of climate change on understory microclimate buffering and decoupling

In this work package, we will focus on the impact of climate change on understory microclimate, in particular CO2, to test hypothesis (H3) that on-going climate change, and especially the rapid rise in atmospheric CO2 levels, favours understory species and enhances the buffering of the understory microclimate from the regional macroclimate.

Project partners

A consortium of micrometeorologists, forest ecologists, remote-sensing image analysts and modellers from 8 complementary research units was created to achieve the objectives of the project. Together, the consortium gathers all the facilities required to conduct the experiments and modelling envisaged in this project:

  • partner 1 (ISPA) brings expertise in micrometeorology, microclimate modelling, forest management and remote sensing, and will provide existing and new microclimate and ancillary datasets from the ICOS/Fluxnet network and the Landes and urban sites, as well as the biophysical models MuSICA and MuSICA-ARPS;
  • partner 2 (EDB) brings expertise in tropical forest micrometeorology, ecology and remote-sensing;
  • partner 3 (EDYSAN) brings expertise on statistical microclimate, niche modelling and temperate forest ecology and biodiversity, and will provide microclimate and ancillary datasets from several ONF sites (Mormal, Blois, Augoual);
  • partner 4 (BIOGECO) brings expertise in temperate and urban forest ecology and biodiversity, and will provide microclimate and ancillary datasets from the Ciron, ORPHEE and urban sites;
  • partner 5 (TETIS) brings expertise in LiDAR data, satellite image analysis and forest ecology, and will provide remotely-sensed products of canopy structure and canopy biodiversity at the partners’ sites;
  • partner 6 (Dr. Pitter Ferrio, CITA, Spain) brings expertise in Mediterranean forest ecology and management, and will provide microclimate and ancillary datasets from the Moncayo sites;
  • partner 7 (Dr. Rosie Fisher, CICERO, Norway) brings expertise in large-scale dynamic vegetation modelling and will provide the global vegetation demography model CLM-FATES (in particular, Dr. Rosie Fisher is the external co-chair of the CLM-FATES model working group);
  • partner 8 (Prof. Gordon Bonan, NCAR, USA) brings expertise in large-scale microclimate modelling with the multi-layer, large scale land surface model CLM-ml.

Publications and communications

You can follow activities related to the MaCCMic project on this webpage and on Twitter using the hashtag #projectMaCCMic.

Project meetings and reports

Minutes and presentations of the different project meetings, as well as project reports sent to the funding body (ANR) will be added here as the project advances.

A 5′ presentation of the project given to the ANR office in November 2021 (in french) can be found here.

The kick-off meeting of the ANR project was virtual due to COVID19 restrictions. It was held on January 12, 2022, and was organised in two sessions: a first session in the morning to meet the partners and discuss the practicalities for the implementation of the project, and a second session in the afternoon to discuss science around presentations on MaCCMic-related topics and on-going work. The program of this afternoon session is given below.

  • Decametric-scale buffering of climate extremes in forest understory along a riparian corridor: implications for climate microrefugia. Jérôme Ogée, Adrià Barbeta, Yves Brunet, Emmanuel Corcket & Marion Walbott
  • Impact of restoration itineraries of old Mediterranean coppice on carbon sequestration and forest productivity, the CO2PPICE project. Juan Pitter Ferrio et al.
  • Impacts of microclimatic processes on forest biodiversity redistribution under macroclimate warming, the IMPRINT project. Eva Gril, Jonathan Lenoir et al.
  • Interactions between structure, microclimate and biodiversity along the Ciron riparian forest. Amandine Acloque, Frédéric Revers et al.
  • Climate change in cities: the impact of the urban heat island on microclimate, biodiversity and ecosystem functioning in urban forests. Karen De Pauw, Pieter De Frenne et al.
  • Implementing understory microclimate buffering in dynamic global vegetation models: challenges and opportunities. Gordon Bonan et al.
  • Contributions of remote sensing for monitoring functional biodiversity and forest structure. Sylvie Durrieu & Jean-Baptiste Feret