Résumé
Biofunctool® is a new framework for assessing the impact of land management on soil quality – defined as the capacity of the soil to function. Biofunctool® uses a set of twelve indicators to monitor changes in three key soil functions: carbon transformation, nutrient cycling and structure maintenance (part A). Information from all the indicators is integrated in a Soil Quality Index using multivariate analysis (PCA) weighting. We used Biofunctool® to assess the impact of land use, land use change and agricultural practices on soil quality. The Biofunctool® index was measured for soils in Thailand within rubber plantations, forests and intensive cash crops (cassava and sugar cane). The results demonstrate that the Biofunctool® index provides an aggregated synthetic soil functioning score that is sensitive to land management and is robust in various pedo-climatic contexts. Firstly, the index revealed the impact on soil of land conversion from annual cropping to rubber plantations and ranked the effect on soil with respect to a natural forest reference. Secondly, it showed the positive effect of legume cover-crops on soil functioning. Thirdly, it highlighted a trend of improving soil quality with increasing age of rubber plantations, in contrasted pedo-climatic contexts. It is concluded that the Biofunctool® index is a reliable and relevant descriptor of integrated soil functioning (i.e. soil quality) that could be useful for environmental impact assessment at regional to global scales.
Auteurs, date et publication :
Auteurs Alexis Thoumazeau , Cécile Bessou , Marie-Sophie Renevier , Phantip Panklang , Porntip Puttaso , Monrawee Peerawat , Pusanisa Heepngoen , Prapatsorn Polwong , Nitjaporn Koonklang , Sayan Sdoodee , Pisamai Chantuma , Phrueksa Lawongsa , Prakaijan Nimkingrat , Philippe Thaler , Frédéric Gay , Alain Brauman
Publication : Ecological Indicators
Date : 2019
Volume : 97
Pages : 429-437
Catégorie(s)
#CIRAD #FORET RubberfluxRésumé
The assessment of soil quality is a scientific issue that has been widely debated in the literature for the last twenty years. We developed the Biofunctool® framework to assess soil quality based on an integrative approach that accounts for the link between the physico-chemical properties and the biological activity of soils. Biofunctool® consists in a set of twelve in-field, time- and cost-effective indicators to assess three main soil functions: carbon transformation, nutrient cycling and structure maintenance. The indicators were applied in a network of mostly rubber plantations compared with three other land uses in Thailand. We collected 1952 indicators values in 180 sampling points over a wide range of pedo-climatic and agronomic contexts in order to assess the validity of the indicators. A reliability, redundancy and sensitivity analysis was performed to validate the capacity of the set of indicators to assess the impact of land management on soil quality. The results showed the relevance and consistence of each of the twelve indicators to assess the soil functioning. Improvements are finally discussed to guide further implementation of the indicators in various contexts and build a soil quality index.
Auteurs, date et publication :
Auteurs Alexis Thoumazeau , Cécile Bessou , Marie-Sophie Renevier , Jean Trap , Raphaël Marichal , Louis Mareschal , Thibaud Decaëns , Nicolas Bottinelli , Benoît Jaillard , Tiphaine Chevallier , Nopmanee Suvannang , Kannika Sajjaphan , Philippe Thaler , Frédéric Gay , Alain Brauman
Publication : Ecological Indicators
Date : 2019
Volume : 97
Pages : 100-110
Catégorie(s)
#CIRAD #FORET RubberfluxRésumé
Tropical forests harbor the greatest terrestrial biodiversity and provide various ecosystem services. The increase of human activities on these forests, among which logging, makes the conservation of biodiversity and associated services strongly dependent on the sustainability of these activities. However the indicators commonly used to assess the impact of forest exploitation, namely species richness and biomass, provide a limited understanding of their sustainability. Here, we assessed the sustainability of common forest exploitation in the Guiana Shield studying the recovery of two ecosystem services i.e. carbon storage and wood stock, and an ecosystem function i.e. seed dispersal by animals. Specifically, we compared total and commercial biomass, as well as functional composition in seed size of animal-dispersed species in replicated forest plots before and 27 years after exploitation. Species richness is also studied to allow comparison. While species richness was not affected by forest exploitation, total and commercial biomass as well as seed size of animal-dispersed species decreased 27 years after exploitation, similarly to forests affected by hunting. These results show that ecosystem services and function likely did not recover even at the lowest intensity of forest exploitation studied, questioning the sustainability of the most common rotation-cycle duration applied in the tropics.
Auteurs, date et publication :
Auteurs Benjamin Yguel , Camille Piponiot , Ariane Mirabel , Aurelie Dourdain , Bruno Hérault , Sylvie Gourlet-Fleury , Pierre-Michel Forget , Colin Fontaine
Publication : Forest Ecology and Management
Date : 2019
Volume : 433
Pages : 528-534
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The primary objective of the European Space Agency's 7th Earth Explorer mission, BIOMASS, is to determine the worldwide distribution of forest above-ground biomass (AGB) in order to reduce the major uncertainties in calculations of carbon stocks and fluxes associated with the terrestrial biosphere, including carbon fluxes associated with Land Use Change, forest degradation and forest regrowth. To meet this objective it will carry, for the first time in space, a fully polarimetric P-band synthetic aperture radar (SAR). Three main products will be provided: global maps of both AGB and forest height, with a spatial resolution of 200 m, and maps of severe forest disturbance at 50 m resolution (where “global” is to be understood as subject to Space Object tracking radar restrictions). After launch in 2022, there will be a 3-month commissioning phase, followed by a 14-month phase during which there will be global coverage by SAR tomography. In the succeeding interferometric phase, global polarimetric interferometry Pol-InSAR coverage will be achieved every 7 months up to the end of the 5-year mission. Both Pol-InSAR and TomoSAR will be used to eliminate scattering from the ground (both direct and double bounce backscatter) in forests. In dense tropical forests AGB can then be estimated from the remaining volume scattering using non-linear inversion of a backscattering model. Airborne campaigns in the tropics also indicate that AGB is highly correlated with the backscatter from around 30 m above the ground, as measured by tomography. In contrast, double bounce scattering appears to carry important information about the AGB of boreal forests, so ground cancellation may not be appropriate and the best approach for such forests remains to be finalized. Several methods to exploit these new data in carbon cycle calculations have already been demonstrated. In addition, major mutual gains will be made by combining BIOMASS data with data from other missions that will measure forest biomass, structure, height and change, including the NASA Global Ecosystem Dynamics Investigation lidar deployed on the International Space Station after its launch in December 2018, and the NASA-ISRO NISAR L- and S-band SAR, due for launch in 2022. More generally, space-based measurements of biomass are a core component of a carbon cycle observation and modelling strategy developed by the Group on Earth Observations. Secondary objectives of the mission include imaging of sub-surface geological structures in arid environments, generation of a true Digital Terrain Model without biases caused by forest cover, and measurement of glacier and icesheet velocities. In addition, the operations needed for ionospheric correction of the data will allow very sensitive estimates of ionospheric Total Electron Content and its changes along the dawn-dusk orbit of the mission.
Auteurs, date et publication :
Auteurs Shaun Quegan , Thuy Le Toan , Jerome Chave , Jorgen Dall , Jean-François Exbrayat , Dinh Ho Tong Minh , Mark Lomas , Mauro Mariotti D'Alessandro , Philippe Paillou , Kostas Papathanassiou , Fabio Rocca , Sassan Saatchi , Klaus Scipal , Hank Shugart , T. Luke Smallman , Maciej J. Soja , Stefano Tebaldini , Lars Ulander , Ludovic Villard , Mathew Williams
Publication : Remote Sensing of Environment
Date : 2019
Volume : 227
Pages : 44-60
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Understanding the Global Climate Change and the way it will affect the Earth and preserving biodiversity are two major challenges of the 21st century. Forests cover 30% of continental surfaces and are a major contributor to the carbon cycle. Sequestration of carbon in forest biomass appears as an important mechanism - in conjunction with reduced emissions - for mitigating climate change. Adequate management of forest resources could strengthen the action of forests as a carbon sink. Forests also play a key role for biodiversity conservation and energy supply. Sustainable management of forest ecosystems is thus critical for the future of mankind. However, the lack of consistent information on forest structure and biomass and on their dynamics at global scale hampers the development of ecological models and of earth-vegetation-atmosphere interaction global models that are essential to improve knowledge on forest ecosystem functioning and to address the challenge of forest sustainable management. By its ability to measure the vertical structure of land cover, airborne Lidar technology is highly qualified for forest applications. NASA's ICESat1 mission (2003-2009) paved the way for Earth observation from space with Lidar systems. ICESat2, launched in September 2018, although primarily designed for ice monitoring will also provide vegetation height measurements worldwide. Vegetation profiles with high vertical resolution should also become soon available with GEDI (NASA) and MOLI (JAXA) missions that will be installed on the ISS at the end of 2018 and in 2019 or 2020, respectively. Although data coverage will be limited from 52°S to 52°N, both these missions will contribute to ecosystem structure observation from space in conjunction with radar missions, especially the BIOMASS ESA's mission. Combined with Sentinel 2 imagery, which provides spectral information with high spatial and temporal resolutions, they will also enable to evaluate the complementarity between information on 3D structure, composition and phenology for a comprehensive monitoring of forest ecosystem conditions. LEAF (Lidar For Earth and Forests) mission has been under study at CNES since 2008 and could contribute in the future to the international effort to sustain global carbon and biodiversity monitoring systems. The system under study combines a NIR full-waveform Lidar profiler and a very high resolution multispectral imager. CNES has supported scientific projects in order to refine instrument specifications and design a system that will meet user requirements. Due to the high cost associated with the development of an airborne prototype, priority has been given to simulation approaches. The aim of this contribution is to present LEAF mission concept and to focus on the recent "LEAF ExpeVal" experiment, designed to consolidate and validate the simulation approaches developed to model a realistic Lidar signal on various forest types, including complex tropical forests. These approaches rely on DART, a radiative transfer model developed at CESBIO. A Lidar module was introduced into DART in the early 2010s and has undergone constant improvement since then. However, simulating a realistic signal also requires to work on model inputs and to develop methods to build detailed forest scenes. The objective of the LEAF-Expeval experiment was twofold: first, to validate the simulations by comparing simulated and experimental Lidar waveforms on a tropical forest; second, to develop a new approach to simulate spaceborne Lidar data from small footprint airborne Lidar data (ALS data). Achieving the first objective is a key step to refine LEAF system specifications in order to ensure that the system will provide accurate height measurements and vegetation profiles on tropical forests, which are the most constraining environment for a space Lidar. Field and airborne data were collected in Paracou experimental forest in French Guiana. The processing and analysis steps include (1) the construction of forest scenes from TLS (Terrestrial Lidar Scanner) and reflectance measurements on a dense forest plot, (2) the estimation of the calibration coefficient of the airborne system, coefficient that is used to convert digital count into physical units, (3) the simulation of airborne Lidar data on the forest scene using DART and (4) the comparison of simulated and real waveforms. As ALS data are now widely available, achieving the second objective would enable the simulation and evaluation of LEAF data on a variety of forest ecosystems. This part of the study relies on Lidar simulations realized on temperate broadleaved forest scenes created using Allostand (Amap) and Genesis software. Small footprint lidar point clouds were simulated using DART and were in turn used to simulate large footprint lidar waveforms. The resulting waveforms were compared to reference data, i.e. large footprint waveforms obtained directly with DART on the same forest scenes. First results are encouraging and showed that large footprint waveforms obtained from the processing of small footprint data were very similar to reference waveforms, even with a change of waveband between lidar point clouds and large footprint waveform.
Auteurs, date et publication :
Auteurs S. Durrieu , F. de Boissieu , J. P. Gastellu Etchegorry , G. Vincent , C. Lavalley , G. Couderc , S. Mpili , F. Heuschmidt , J. Costeraste , J. B. Feret , D. Ebengo , N. Lauret , M. J. Lefèvre Fonollosa , T. Yin
Date : 2019
Pages : 21
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Increasing evidence shows that the functioning of the tropical forest biome is intimately related to the climate variability with some variables such as annual precipitation, temperature or seasonal water stress identified as key drivers of ecosystem dynamics. How tropical tree communities will respond to the future climate change is hard to predict primarily because several demographic processes act together to shape the forest ecosystem general behavior. To overcome this limitation, we used a joint individual-based model to simulate, over the next century, a tropical forest community experiencing the climate change expected in the Guiana Shield. The model is climate dependent: temperature, precipitation and water stress are used as predictors of the joint growth and mortality rates. We ran simulations for the next century using predictions of the IPCC 5AR, building three different climate scenarios (optimistic RCP2.6, intermediate, pessimistic RCP8.5) and a control (current climate). The basal area, above-ground fresh biomass, quadratic diameter, tree growth and mortality rates were then computed as summary statistics to characterize the resulting forest ecosystem. Whatever the scenario, all ecosystem process and structure variables exhibited decreasing values as compared to the control. A sensitivity analysis identified the temperature as the strongest climate driver of this behavior, highlighting a possible temperature-driven drop of 40% in average forest growth. This conclusion is alarming, as temperature rises have been consensually predicted by all climate scenarios of the IPCC 5AR. Our study highlights the potential slow-down danger that tropical forests will face in the Guiana Shield during the next century.
Auteurs, date et publication :
Auteurs Mélaine Aubry-Kientz , Vivien Rossi , Guillaume Cornu , Fabien Wagner , Bruno Hérault
Publication : Scientific Reports
Date : 2019
Volume : 9
Issue : 1
Pages : 10235
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Synthetic aperture radar (SAR) tomography (TomoSAR) is an emerging technology to image the 3D structure of the illuminated media. TomoSAR exploits the key feature of microwaves to penetrate into vegetation, snow, and ice, hence providing the possibility to see features that are hidden to optical and hyper-spectral systems. The research on the use of P-band waves, in particular, has been largely propelled since 2007 in experimental studies supporting the future spaceborne Mission BIOMASS, to be launched in 2022 with the aim of mapping forest aboveground biomass (AGB) accurately and globally. The results obtained in the frame of these studies demonstrated that TomoSAR can be used for accurate retrieval of geophysical variables such as forest height and terrain topography and, especially in the case of dense tropical forests, to provide a more direct link to AGB. This paper aims at providing the reader with a comprehensive understanding of TomoSAR and its application for remote sensing of forested areas, with special attention to the case of tropical forests. We will introduce the basic physical principles behind TomoSAR, present the most relevant experimental results of the last decade, and discuss the potentials of BIOMASS tomography.
Auteurs, date et publication :
Auteurs Stefano Tebaldini , Dinh Ho Tong Minh , Mauro Mariotti d’Alessandro , Ludovic Villard , Thuy Le Toan , Jerome Chave
Publication : Surveys in Geophysics
Date : 2019
Volume : 40
Issue : 4
Pages : 779-801
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
In this work we investigate the role of volume scattering obtained from tomography and ground/volume decomposition in retrieving AGB (Above Ground Biomass). Results here presented originate from the BIOMASS L2 study, aimed at defining and implementing the tomographic and interferometric processors of the BIOMASS mission. In particular we aim at discussing whether, and to what extent, ground/volume decomposition can provide a valid alternative to tomography. To do this, both are tested based on the P-Band data collected at the forest site of Paracou, French Guiana, during the TropiSAR campaign, and validated against in-situ AGB measurements in terms of correlation and sensitivity of the retrievals. Quite surprisingly, results indicate that volumebackscattered power as obtained by ground/volume decomposition is almost unsensitive to AGB, notwithstanding different solutions for volume scattering are tested, and lead to conclusion that forest structure actually plays a non-negligible role in AGB retrieval in tropical areas.
Auteurs, date et publication :
Auteurs F. Banda , M. M. d’Alessandro , S. Tebaldini , D. Giudici
Date : 2019
Pages : 1073-1076
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The architecture (here, the size distribution combined with the spatial pattern of individuals) of natural forest at demographic equilibrium can be used to infer the demographic processes that drive the forest dynamics. In particular, a constant growth rate and a constant mortality rate for all trees would generate an exponential distribution of their size, whereas the metabolic scaling theory predicts a power distribution. In an undisturbed tropical rainforest in French Guiana, the diameter distribution was significantly steeper than the best-fit exponential distribution and significantly flatter than the best-fit power distribution. A simple individual-based model of forest dynamics with asymmetric competition between trees, where the strength of competition was regulated by a single parameter, was able to predict the observed distribution. Competition drove the forest into a self-organized state with stronger inequalities of size among trees, a lower mean competition index, and a spatial pattern of trees that deviated from complete spatial randomness.
Auteurs, date et publication :
Auteurs Nicolas Picard
Publication : Forest Science
Date : 2019
Volume : 65
Issue : 5
Pages : 562-569
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Improving our understanding of the spatiotemporal dynamics of fine roots in deep soil layers is of utter importance to manage tropical planted forests in a context of climate change. Our study aimed to assess the effect of dear-cutting and drought on fine-root dynamics down to the water table in Brazilian ferralsol under eucalypt plantations conducted in coppice. Fine roots (i.e. diameter 13 m) and, surprisingly, root mortality remained extremely low whatever the depth and the treatment. Total fine-root biomass in coppice down to 17 m depth was 1266 and 1017 g m(-2) in + W and -W, respectively, at 1.5 year after the clear-cut and was 1078 g m(-2) in NH 7.5 years after planting. Specific root length and specific root area were about 15% higher in -W than in + W. Proliferation of fine roots at great depths could be an adaptive mechanism for tree survival, enhancing the access to water stored in the subsoil. The root system established before clear-cutting provides access to water stored in very deep layers that probably contribute to mitigate the risk of tree mortality during prolonged drought periods when the eucalypt plantations is conducted in coppice after the clear-cut.
Auteurs, date et publication :
Auteurs Amandine Germon , Christophe Jourdan , Bruno Bordron , Agnes Robin , Yann Nouvellon , Lydie Chapuis-Lardy , Jose Leonardo de Moraes Goncalves , Celine Pradier , Irae Amaral Guerrini , Jean-Paul Laclau
Publication : FOREST ECOLOGY AND MANAGEMENT
Date : 2019
Volume : 445
Pages : 48-59