- Email: [email protected]
Promoting ecological engineering for restoration of biodiversity in temperate forests
Procedia Environmental Sciences
Available online at www.sciencedirect.com Available online at www.sciencedirect.com
Procedia Environmental Sciences 00 (2011) 000–000 Procedia Environmental Sciences 9 (2011) 118 – 123
www.elsevier.com/locate/procedia
Ecological engineering: from concepts to applications
Promoting ecological engineering for restoration of biodiversity in temperate forests Damien Maragea,b, * a
AgroParisTech-ENGREF Nancy, UMR 1092, Nancy F-54000, France b INRA, UMR 1092, Nancy F-54000, France
Elsevier use only: Received date here; revised date here; accepted date here
Abstract In temperate forest, managers have both used civil engineering, biological engineering and ecological principles to optimize one function: wood production, flood regulation or reduction of soil erosion. Other forest practitioners used biological interactions and biotic controls to manage uneven-aged stands, especially in mountain forests. These actions just required the knowledge and control of both coarse biological and physical processes at a local scale. The challenges inherent to solve multi-scale biodiversity changes are crucial today. In order to achieve these crucial issues and optimize several ecological functions and ecosystem services, spatial modelling approaches are developed at a landscape level using species traits associated with environmental databases. © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Laboratory “Biochemistry and ecology of continental environments © 2011 Published by Elsevier BV Keywords: biotic interaction; forest ecosystem; global change; mitigation; modelling
1. Introduction An ecological engineer wishes to design sustainable forest ecosystems consistently with ecological principles, and to integrate human society in this management for the benefit of both [1]. For attaining this aim, he should consider the relationships between organisms, including humans, and their environment and the constraints imposed on design by the complexity, variability and uncertainty inherent to natural systems. In practice, foresters drive both physical and biological processes, drive ecological interactions, drive connectivity at a landscape level, and maybe the most important issue, should also drive social interactions [2]. Taking these principles into consideration, many forest engineers have already driven physical and biological processes to create or restore ecosystems [3,4,5]. In doing so, they have created new ecosystems, which offer valuable goods and services. In each particular case, they have applied ecological principles to optimize a limited array of functions, i.e. dune fixation [6], soil erosion [7], or biomass production [8]. But what happens when huge collapses, such as hurricanes or landslides, arise? Uncertainty is inherent to natural system. Forest managers have driven species interactions in classical sylviculture [9], and fiercely with the "close to nature" sylviculture [10-12]. The latter maintains the species pool, but with fewer specialists and more generalists
* Corresponding author. Tel.: +3-383-396-881; fax: +3-383-396-878. E-mail address: [email protected].
1878-0296 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Laboratory “Biochemistry and ecology of continental environments doi:10.1016/j.proenv.2011.11.019
Damien Marage / Procedia Environmental Sciences 9 (2011) 118 – 123 D. Marage / Procedia Environmental Sciences 00 (2011) 000–000
119
species than the classical sylviculture. The “close-to-nature” sylviculture reduces beta-diversity among stands and thus forest heterogeneity at the landscape level [13]. The currently used rotations do not match natural disturbances very closely and are applied to a managed system rather than they mimic Nature [14]. Thus, the importance of landscape patterns and processes (e.g. connectivity) for maintaining and protecting biodiversity (for example saproxylic species inhabiting dead wood materials) becomes greater [15, 16]. Nowadays, our environment is currently evolving according to several drivers of change, such as land use, climate change, Nitrogen deposition, and species invasions [17]. Land use, fragmentation and climate change have obvious detrimental effects on many populations inhabiting forests [18]. Climate change induces a significant upward shift in the herbaceous forest species in French mountains, and affects in this way forest vegetation vulnerability [19]. Halting the loss of forest biodiversity, in order to maintain or optimize ecological functions for delivering goods and services [20], has been recognized as a major objective by the European Commission [21]. In this paper, I propose modelling approaches for better understanding what can be done for promoting ecological engineering in temperate forest management, by taking into account the heterogeneity of threats, vulnerabilities and stakes at a landscape level, in order to maintain or restore biodiversity. 2. Materials and methods 2.1. The conceptual framework The conceptual framework was inspired by risk assessment procedures in a spatially explicit context [22]. The landscape was decomposed into different patches (Fig. 1). The species richness and the number of functional groups within each patch were known. Within each patch, natural and/or anthropogenic disturbances drived pattern and process of biodiversity [23]. If the exposure to a particular disturbance already existed at a temporal and/or spatial scale, then both populations and communities were considered to be threatened. When the impact of a disturbance was unknown (e.g. the effect of climate change), it was defined as a stochastic event. Vulnerability1 was defined as the invert function of resilience. The latter is the magnitude of disturbance that can be tolerated before a system moves to a different region of state space, controlled by a different set of processes. So, it refers to the ecological resilience sensu Holling. Increased vulnerability, as a consequence of loss of resilience, places a region on a trajectory of greater risk to the panoply of stresses and shocks that occur over time. As a first approximation [24], [25], we considered that the higher is the number of functional groups within the specific pool, the greater is the resilience. We calculated a vulnerability vector that represented the linear combination of species richness and functional groups richness. Species richness was measured on the field, but it might also have been derived from previous ecological niche modelling approaches and then interpolated. Functional groups were derived from species trait databases already existing [26]. By combining vulnerability and threat matrices, a risk matrix was calculated. When expressed in two dimensional axes, it should be considered as a threshold and then as a direct assessment of the good ecological status.
1
the degree to which an ecosystem service is sensitive to global environmental change and the degree to which the sector that relies on the service is unable to adapt to the changes
D. Marage / Procedia Environmental Sciences 00 (2011) 000–000
120
Damien Marage / Procedia Environmental Sciences 9 (2011) 118 – 123
Drivers
Ecosystem
Disturbances
Populations Community
Exposure Effects
Species Richness Functional groups
Threats Matrix
Vulnerability Matrix
Fig. 1. Conceptual Framework for Forest Biodiversity Restoration in an Ecological Engineering Perspective
2.2. Case study 2.2.1. Study site In the French Pyrenean Mountains, the National Forest of Camporells is located ten km North of the Spain frontier (Fig. 2).
Damien Marage / Procedia Environmental Sciences 9 (2011) 118 – 123 D. Marage / Procedia Environmental Sciences 00 (2011) 000–000
121
Fig. 2. Study site location
This area covers twenty km2 and its elevation ranges from 1 500 and 2 700 m above sea level. The forest lies on a substratum mainly composed of granitic bedrock and the soils are mostly shallow rankers. Although today, it is devoid of any permanent settlement, the site has lived through a unique and eventful history, which has been known since the fourth century, illustrating the complex relationships which, in days gone, by uniting the local communities with their surroundings, where the grass and the forest formed the only exploitable resources. For about tree hundred years, forest communities have been profoundly affected by anthropogenic impacts, e.g. by metallurgic plans [27]. The intensity and duration of forest activities are crucial determinants in the patterns and processes of communities in this landscape. The exceptional richness of the fauna and flora of the National Forest of Camporells constitute a patrimony that we have inherited, and this area is now included in the European Natura 2000 network. 2.2.2. Sampling design and data analysis The sampling design was developed using a Geographic Information System. As a first step, we distributed field plots according to woody species cover as revealed by orthorectified photographs. As a second step, we identified, quantified and mapped human activities, i.e. grazing, skiing, harvesting, and hunting. As a third step, sampling units were defined by using a stratified sampling procedure on stages of succession and human activities. Sampling was limited to the altitudinal interval 1500 - 2300 m. A total of one hundred and twenty field plots were localized in the field. Each plot was subjected to an exhaustive inventory of vascular plants following the classical phytosociological method following [28], using a standardized plot size of 400 m². GIS modelling was used to estimate environmental variables such as classical topographical variables, climatic and soil nutrient parameters with a fifty-meter spatial resolution. All environmental and land-use GIS layers were generated at this resolution by vector to raster conversion. Geo-referenced data were gathered for the whole study area and stored, in a grid format with a 50-m resolution. 3. Results and discussion The spatial and statistical analyses provided maps of threats, vulnerabilities and stakes, respectively, according to our conceptual framework (Fig. 3). On the basis of the stake maps, the forest management staff organised several meetings with the stakeholders involved, i.e. hunters, fishers, tourism agencies, NGO, and the local officials of the winter sports resort. Then, they decided what part of the National Forest of Camporells would become a protected area.
122
Damien/ Marage Environmental Sciences (2011) 118 – 123 D. Marage Procedia/ Procedia Environmental Sciences 00 (2011)9000–000
(a)
(b)
(c) Fig. 3. Maps of the level of threats (a), vulnerabilities (b) and stakes (c) in the National Forest of Camporells
What strategies and opportunities can be drawn with our approach? To promote ecological engineering and restore biodiversity in temperate forests, four forward issues are needed, three of them in order to better understand ecosystem dynamics, and the other one to incorporate socio-economic dynamics. The latter should be really improved by using multi-criteria approaches, such as the ELECTRE method [29]. It should contribute to reduce inequalities among stakeholders and provide the best way to curb local conflicts. Concerning ecological dynamics, we should enhance resilience by describing and better taking into account species and ecological redundancy.
Damien Marage / Procedia Environmental Sciences 9 (2011) 118 – 123 D. Marage / Procedia Environmental Sciences 00 (2011) 000–000
123
Striving fiercely the Species Abundance Models is also an important issue because we rarely know a priori which species or communities are critical to current functioning or provide resilience and resistance to environmental changes; in introducing dispersal traits into modelling process and updating data, it would be curb uncertainty. Then, to cope with a changing climate, Regional Climatic Models should be fostered. We expect that this approach will be applied rapidly in temperate forests. Acknowledgments I wish to thank Stéphane Nouguier and Olivier Constantini from the French Forestry Commission of LanguedocRoussillon for granting permission to sample in the National Forest of Camporells and for providing some of the georeferenced data. I also thank students from the Paris Institute of Technology for Life, Food and Environmental Sciences for collecting field data. This project was carried out with a pedagogical grant from the French Forestry Commission. References [1] W.J. Mitsch, and S.E. Jørgensen, Ecological Engineering and Ecosystem Restoration, John Wiley & Sons, New York, USA, 2004. [2] S.D. Bergen, S.M. Bolton, and J.L. Fridley, Ecol. Eng., 18(2001)201. [3] T.W. Berger, and H. Hager, For. Ecol. Manag., 136(2000)159. [4] M. Burylo, F. Rey, and P. Delcros, Ecol. Eng., 30(2007)231. [5] F. Isselin-Nondedeu, F. Rey, and A. Bedecarrats, Ecol. Eng., 27(2006)193. [6] J. Favennec, Le contrôle souple des dunes littorales atlantiques, Rev. For. Fr., LIII(2001)279. [7] S. Luyssaert, J. Mertens, P. Vervaeke, B. de Vos, and N. Lust, Ecol. Eng., 16(2001)567. [8] H. Gruenewald, B.K.V. Brandt, B.U. Schneider, O. Bens, G. Kendzia, and R.F. Huttl, Ecol. Eng., 29(2007)319. [9] C. Barthod, and G. Landmann, Pourquoi gérer la végétation forestière ?, Rev. For. Fr., LIV(2002)617. [10] J.P. Schutz, Forestry, 75(2002)329. [11] J.P. Schutz, Forestry, 75(2002)327. [12] J.P. Schutz, Ann. For. Sci., 61(2004)149. [13] J.P. Schutz, Forestry, 72(1999)359. [14] G. Decocq, M. Aubert, F. Dupont, D. Alard, R. Saguez, A. Wattez-Franger, B. De Foucault, A. Delelis-Dusollier, and J. Bardat, J. Appl. Ecol., 41(2004)1065. [15] M.T. Jonsson, M. Edman, and B.G. Jonsson, J. Ecol., 96(2008)1065. [16] K. Schiegg, Ecography, 23(2000)579. [17] O.E. Sala, F.S. Chapin, J.J. Armesto, E. Berlow, J. Bloomfield, R. Dirzo, E. Huber-Sanwald, L.F. Huenneke, R.B. Jackson, A. Kinzig, R. Leemans, D.M. Lodge, H.A. Mooney, M. Oesterheld, N.L. Poff, M.T. Sykes, B.H. Walker, M. Walker, and D.H. Wall, Science, 287(2000)1770. [18] European Environment Agency, European forests — ecosystem conditions and sustainable use, Office for Official Publications of the European Communities, Copenhagen, Denmark, 2008. [19] J. Lenoir, J.C. Gégout, P. Marquet, P. de Ruffray, and H. Brisse, Science, 320(2008)1768. [20] Millennium Ecosystem Assessment, Ecosystems and Human Well-being: Biodiversity Synthesis, World Resources Institute, Washington DC, USA, 2005. [21] European-Environment-Agency, Halting the loss of biodiversity by 2010: proposal for a first set of indicators to monitor progress in Europe, EEA, Copenhague, Denmark, (2007)182. [22] A. Dauphiné, Risques et catastrophes : observer-spatialiser-comprendre-gérer, Armand Collin, Paris, France, 2001. [23] H.J. Connell, and W.P. Sousa, Am. Nat., 121(1983)789. [24] M. Loreau, S. Naeem, and P. Inchausti, Biodiversity and ecosystem functionning, Oxford University Press, Oxford, UK, 2002. [25] M. Scherer-Lorenzen, E.D. Schulze, A. Don, J. Schumacher, and E. Weller, Perspect. Plant Ecol., 9(2007)53. [26] I.C. Knevel, R.M. Bekker, J.P. Bakker, and M. Kleyer, J. Veg. Sci., 14(2003)611. [27] C. Rendu, La montagne d'Enveig, Une estive pyrénéenne dans la longue durée, Eds. Trabucaire, Canet, France, 2003. [28] J. Braun-Blanquet, Plant sociology, the study of plant communities, McGraw-Hill Book Company, New York, USA, 1932. [29] B. Roy, Multicriteria Methodology for Decision Analysis, Kluwer Academic Publishers, 1996.
Available online at www.sciencedirect.com Available online at www.sciencedirect.com
Procedia Environmental Sciences 00 (2011) 000–000 Procedia Environmental Sciences 9 (2011) 118 – 123
www.elsevier.com/locate/procedia
Ecological engineering: from concepts to applications
Promoting ecological engineering for restoration of biodiversity in temperate forests Damien Maragea,b, * a
AgroParisTech-ENGREF Nancy, UMR 1092, Nancy F-54000, France b INRA, UMR 1092, Nancy F-54000, France
Elsevier use only: Received date here; revised date here; accepted date here
Abstract In temperate forest, managers have both used civil engineering, biological engineering and ecological principles to optimize one function: wood production, flood regulation or reduction of soil erosion. Other forest practitioners used biological interactions and biotic controls to manage uneven-aged stands, especially in mountain forests. These actions just required the knowledge and control of both coarse biological and physical processes at a local scale. The challenges inherent to solve multi-scale biodiversity changes are crucial today. In order to achieve these crucial issues and optimize several ecological functions and ecosystem services, spatial modelling approaches are developed at a landscape level using species traits associated with environmental databases. © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Laboratory “Biochemistry and ecology of continental environments © 2011 Published by Elsevier BV Keywords: biotic interaction; forest ecosystem; global change; mitigation; modelling
1. Introduction An ecological engineer wishes to design sustainable forest ecosystems consistently with ecological principles, and to integrate human society in this management for the benefit of both [1]. For attaining this aim, he should consider the relationships between organisms, including humans, and their environment and the constraints imposed on design by the complexity, variability and uncertainty inherent to natural systems. In practice, foresters drive both physical and biological processes, drive ecological interactions, drive connectivity at a landscape level, and maybe the most important issue, should also drive social interactions [2]. Taking these principles into consideration, many forest engineers have already driven physical and biological processes to create or restore ecosystems [3,4,5]. In doing so, they have created new ecosystems, which offer valuable goods and services. In each particular case, they have applied ecological principles to optimize a limited array of functions, i.e. dune fixation [6], soil erosion [7], or biomass production [8]. But what happens when huge collapses, such as hurricanes or landslides, arise? Uncertainty is inherent to natural system. Forest managers have driven species interactions in classical sylviculture [9], and fiercely with the "close to nature" sylviculture [10-12]. The latter maintains the species pool, but with fewer specialists and more generalists
* Corresponding author. Tel.: +3-383-396-881; fax: +3-383-396-878. E-mail address: [email protected].
1878-0296 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Laboratory “Biochemistry and ecology of continental environments doi:10.1016/j.proenv.2011.11.019
Damien Marage / Procedia Environmental Sciences 9 (2011) 118 – 123 D. Marage / Procedia Environmental Sciences 00 (2011) 000–000
119
species than the classical sylviculture. The “close-to-nature” sylviculture reduces beta-diversity among stands and thus forest heterogeneity at the landscape level [13]. The currently used rotations do not match natural disturbances very closely and are applied to a managed system rather than they mimic Nature [14]. Thus, the importance of landscape patterns and processes (e.g. connectivity) for maintaining and protecting biodiversity (for example saproxylic species inhabiting dead wood materials) becomes greater [15, 16]. Nowadays, our environment is currently evolving according to several drivers of change, such as land use, climate change, Nitrogen deposition, and species invasions [17]. Land use, fragmentation and climate change have obvious detrimental effects on many populations inhabiting forests [18]. Climate change induces a significant upward shift in the herbaceous forest species in French mountains, and affects in this way forest vegetation vulnerability [19]. Halting the loss of forest biodiversity, in order to maintain or optimize ecological functions for delivering goods and services [20], has been recognized as a major objective by the European Commission [21]. In this paper, I propose modelling approaches for better understanding what can be done for promoting ecological engineering in temperate forest management, by taking into account the heterogeneity of threats, vulnerabilities and stakes at a landscape level, in order to maintain or restore biodiversity. 2. Materials and methods 2.1. The conceptual framework The conceptual framework was inspired by risk assessment procedures in a spatially explicit context [22]. The landscape was decomposed into different patches (Fig. 1). The species richness and the number of functional groups within each patch were known. Within each patch, natural and/or anthropogenic disturbances drived pattern and process of biodiversity [23]. If the exposure to a particular disturbance already existed at a temporal and/or spatial scale, then both populations and communities were considered to be threatened. When the impact of a disturbance was unknown (e.g. the effect of climate change), it was defined as a stochastic event. Vulnerability1 was defined as the invert function of resilience. The latter is the magnitude of disturbance that can be tolerated before a system moves to a different region of state space, controlled by a different set of processes. So, it refers to the ecological resilience sensu Holling. Increased vulnerability, as a consequence of loss of resilience, places a region on a trajectory of greater risk to the panoply of stresses and shocks that occur over time. As a first approximation [24], [25], we considered that the higher is the number of functional groups within the specific pool, the greater is the resilience. We calculated a vulnerability vector that represented the linear combination of species richness and functional groups richness. Species richness was measured on the field, but it might also have been derived from previous ecological niche modelling approaches and then interpolated. Functional groups were derived from species trait databases already existing [26]. By combining vulnerability and threat matrices, a risk matrix was calculated. When expressed in two dimensional axes, it should be considered as a threshold and then as a direct assessment of the good ecological status.
1
the degree to which an ecosystem service is sensitive to global environmental change and the degree to which the sector that relies on the service is unable to adapt to the changes
D. Marage / Procedia Environmental Sciences 00 (2011) 000–000
120
Damien Marage / Procedia Environmental Sciences 9 (2011) 118 – 123
Drivers
Ecosystem
Disturbances
Populations Community
Exposure Effects
Species Richness Functional groups
Threats Matrix
Vulnerability Matrix
Fig. 1. Conceptual Framework for Forest Biodiversity Restoration in an Ecological Engineering Perspective
2.2. Case study 2.2.1. Study site In the French Pyrenean Mountains, the National Forest of Camporells is located ten km North of the Spain frontier (Fig. 2).
Damien Marage / Procedia Environmental Sciences 9 (2011) 118 – 123 D. Marage / Procedia Environmental Sciences 00 (2011) 000–000
121
Fig. 2. Study site location
This area covers twenty km2 and its elevation ranges from 1 500 and 2 700 m above sea level. The forest lies on a substratum mainly composed of granitic bedrock and the soils are mostly shallow rankers. Although today, it is devoid of any permanent settlement, the site has lived through a unique and eventful history, which has been known since the fourth century, illustrating the complex relationships which, in days gone, by uniting the local communities with their surroundings, where the grass and the forest formed the only exploitable resources. For about tree hundred years, forest communities have been profoundly affected by anthropogenic impacts, e.g. by metallurgic plans [27]. The intensity and duration of forest activities are crucial determinants in the patterns and processes of communities in this landscape. The exceptional richness of the fauna and flora of the National Forest of Camporells constitute a patrimony that we have inherited, and this area is now included in the European Natura 2000 network. 2.2.2. Sampling design and data analysis The sampling design was developed using a Geographic Information System. As a first step, we distributed field plots according to woody species cover as revealed by orthorectified photographs. As a second step, we identified, quantified and mapped human activities, i.e. grazing, skiing, harvesting, and hunting. As a third step, sampling units were defined by using a stratified sampling procedure on stages of succession and human activities. Sampling was limited to the altitudinal interval 1500 - 2300 m. A total of one hundred and twenty field plots were localized in the field. Each plot was subjected to an exhaustive inventory of vascular plants following the classical phytosociological method following [28], using a standardized plot size of 400 m². GIS modelling was used to estimate environmental variables such as classical topographical variables, climatic and soil nutrient parameters with a fifty-meter spatial resolution. All environmental and land-use GIS layers were generated at this resolution by vector to raster conversion. Geo-referenced data were gathered for the whole study area and stored, in a grid format with a 50-m resolution. 3. Results and discussion The spatial and statistical analyses provided maps of threats, vulnerabilities and stakes, respectively, according to our conceptual framework (Fig. 3). On the basis of the stake maps, the forest management staff organised several meetings with the stakeholders involved, i.e. hunters, fishers, tourism agencies, NGO, and the local officials of the winter sports resort. Then, they decided what part of the National Forest of Camporells would become a protected area.
122
Damien/ Marage Environmental Sciences (2011) 118 – 123 D. Marage Procedia/ Procedia Environmental Sciences 00 (2011)9000–000
(a)
(b)
(c) Fig. 3. Maps of the level of threats (a), vulnerabilities (b) and stakes (c) in the National Forest of Camporells
What strategies and opportunities can be drawn with our approach? To promote ecological engineering and restore biodiversity in temperate forests, four forward issues are needed, three of them in order to better understand ecosystem dynamics, and the other one to incorporate socio-economic dynamics. The latter should be really improved by using multi-criteria approaches, such as the ELECTRE method [29]. It should contribute to reduce inequalities among stakeholders and provide the best way to curb local conflicts. Concerning ecological dynamics, we should enhance resilience by describing and better taking into account species and ecological redundancy.
Damien Marage / Procedia Environmental Sciences 9 (2011) 118 – 123 D. Marage / Procedia Environmental Sciences 00 (2011) 000–000
123
Striving fiercely the Species Abundance Models is also an important issue because we rarely know a priori which species or communities are critical to current functioning or provide resilience and resistance to environmental changes; in introducing dispersal traits into modelling process and updating data, it would be curb uncertainty. Then, to cope with a changing climate, Regional Climatic Models should be fostered. We expect that this approach will be applied rapidly in temperate forests. Acknowledgments I wish to thank Stéphane Nouguier and Olivier Constantini from the French Forestry Commission of LanguedocRoussillon for granting permission to sample in the National Forest of Camporells and for providing some of the georeferenced data. I also thank students from the Paris Institute of Technology for Life, Food and Environmental Sciences for collecting field data. This project was carried out with a pedagogical grant from the French Forestry Commission. References [1] W.J. Mitsch, and S.E. Jørgensen, Ecological Engineering and Ecosystem Restoration, John Wiley & Sons, New York, USA, 2004. [2] S.D. Bergen, S.M. Bolton, and J.L. Fridley, Ecol. Eng., 18(2001)201. [3] T.W. Berger, and H. Hager, For. Ecol. Manag., 136(2000)159. [4] M. Burylo, F. Rey, and P. Delcros, Ecol. Eng., 30(2007)231. [5] F. Isselin-Nondedeu, F. Rey, and A. Bedecarrats, Ecol. Eng., 27(2006)193. [6] J. Favennec, Le contrôle souple des dunes littorales atlantiques, Rev. For. Fr., LIII(2001)279. [7] S. Luyssaert, J. Mertens, P. Vervaeke, B. de Vos, and N. Lust, Ecol. Eng., 16(2001)567. [8] H. Gruenewald, B.K.V. Brandt, B.U. Schneider, O. Bens, G. Kendzia, and R.F. Huttl, Ecol. Eng., 29(2007)319. [9] C. Barthod, and G. Landmann, Pourquoi gérer la végétation forestière ?, Rev. For. Fr., LIV(2002)617. [10] J.P. Schutz, Forestry, 75(2002)329. [11] J.P. Schutz, Forestry, 75(2002)327. [12] J.P. Schutz, Ann. For. Sci., 61(2004)149. [13] J.P. Schutz, Forestry, 72(1999)359. [14] G. Decocq, M. Aubert, F. Dupont, D. Alard, R. Saguez, A. Wattez-Franger, B. De Foucault, A. Delelis-Dusollier, and J. Bardat, J. Appl. Ecol., 41(2004)1065. [15] M.T. Jonsson, M. Edman, and B.G. Jonsson, J. Ecol., 96(2008)1065. [16] K. Schiegg, Ecography, 23(2000)579. [17] O.E. Sala, F.S. Chapin, J.J. Armesto, E. Berlow, J. Bloomfield, R. Dirzo, E. Huber-Sanwald, L.F. Huenneke, R.B. Jackson, A. Kinzig, R. Leemans, D.M. Lodge, H.A. Mooney, M. Oesterheld, N.L. Poff, M.T. Sykes, B.H. Walker, M. Walker, and D.H. Wall, Science, 287(2000)1770. [18] European Environment Agency, European forests — ecosystem conditions and sustainable use, Office for Official Publications of the European Communities, Copenhagen, Denmark, 2008. [19] J. Lenoir, J.C. Gégout, P. Marquet, P. de Ruffray, and H. Brisse, Science, 320(2008)1768. [20] Millennium Ecosystem Assessment, Ecosystems and Human Well-being: Biodiversity Synthesis, World Resources Institute, Washington DC, USA, 2005. [21] European-Environment-Agency, Halting the loss of biodiversity by 2010: proposal for a first set of indicators to monitor progress in Europe, EEA, Copenhague, Denmark, (2007)182. [22] A. Dauphiné, Risques et catastrophes : observer-spatialiser-comprendre-gérer, Armand Collin, Paris, France, 2001. [23] H.J. Connell, and W.P. Sousa, Am. Nat., 121(1983)789. [24] M. Loreau, S. Naeem, and P. Inchausti, Biodiversity and ecosystem functionning, Oxford University Press, Oxford, UK, 2002. [25] M. Scherer-Lorenzen, E.D. Schulze, A. Don, J. Schumacher, and E. Weller, Perspect. Plant Ecol., 9(2007)53. [26] I.C. Knevel, R.M. Bekker, J.P. Bakker, and M. Kleyer, J. Veg. Sci., 14(2003)611. [27] C. Rendu, La montagne d'Enveig, Une estive pyrénéenne dans la longue durée, Eds. Trabucaire, Canet, France, 2003. [28] J. Braun-Blanquet, Plant sociology, the study of plant communities, McGraw-Hill Book Company, New York, USA, 1932. [29] B. Roy, Multicriteria Methodology for Decision Analysis, Kluwer Academic Publishers, 1996.