Revues majeures des disciplines concernées (1^er quartile)

Vila B., Torre F., Martin J.L., and Guibal F. Response of young Tsuga heterophylla to deer browse. Trees Structure and Function, en révision.

Abstract - We use dendroecological analysis to describe and understand the consequences of deer browsing on the growth of western hemlock (Tsuga heterophylla). We compared tree shape, growth rate, height and age at four different sites in Haida Gwaii (British Columbia, Canada) that had trees representative of the range of deer impact on western hemlock: (1) trees showing no sign of browsing, (2) escaped trees which were still browsed below the browse line and (3) stunted and heavily browsed trees. Repeated and intense browsing resulted in the small size, compact heavily ramified shape characteristic of stunted trees and in the short compact and ramified lower branches of escaped trees. These contrasted with the shape of non browsed trees a shape that was also found in escaped trees above the browse line. Before release, all browsed trees experienced a stagnation in growth characterised by narrow rings (0.3 mm/year) and a small annual height increment (2.5 cm/year). At release, growth rate increased and stabilised: rings were wider (1.3 mm/year) and annual height increments were larger (10.5 cm/year). Non browsed trees had a mean ring-width of 1.3 mm/year and an average height growth of 22 cm/year. Delay in tree recruitment caused by deer varied from site to site. It had been of about 15 years for the escaped trees we studied and we estimated that it will be at least 30-40 years for the stunted trees that we studied. Spatial variation in deer impact may reflect spatial variation of browsing pressure resulting from local differences in the availability of preferred forage or to differences in chemical defences / tree nutritional values.

Keywords - Tsuga heterophylla (Raf.) Sarg.- Deer browsing - Growth pattern - Diameter and height growth - Age - Dendroecology

 

Vila B., Guibal F., Martin J.L. and Torre F. Sous presse. Growth change of young Picea sitchensis in response to deer browsing. Forest Ecology and Management.

Abstract – Taking advantage of the introduction of the black tailed deer to the Haida Gwaii archipelago (Queen Charlotte Islands, British Columbia, Canada), we used dendro-ecological analyses to understand the consequences of deer browsing on Sitka spruce growth. We compared shape, radial growth, height growth and age of young spruce in 3 different sites. We identified two types of trees growing side by side (1) stunted and heavily browsed spruce, smaller than the browsing limit and (2) escaped spruce that were taller than the browsing limit but still browsed in their lower part. The compact and heavily ramified shape in stunted spruce was the result of repeated and intense browsing. In escaped spruce this was also the case below the browsing limit (1.16 ± 0.07 m), in sharp contrast with the normal shape that escaped spruce resumed above the browsing limit. We show that the release of browsing pressure, once the tree reaches the browsing limit, is characterised by an abrupt increase in radial growth. Before release, trees show a growth stagnation characterized by narrow rings (0.5 mm/year) and small annual height increments (<5cm/year). After release, there is a brief period of growth increase, followed by a stabilisation characterised by wider rings (3 mm/year) and larger annual height increments (20 cm/year). We use this pattern to estimate frequency and age at release and their possible variation over time. Age differences between stunted spruce and escaped spruce are highly significant and indicate that, despite of browsing, most if not all tree will ultimately reach the browsing limit and escape. Heavy deer pressure (30 deer/km²) delays spruce sapling recruitment by about 9 years. This delay varies in relation to site quality and seems to have increased over time, suggesting an increase in browsing pressure.

Keywords - Picea sitchensis (Bong.) Carrière – deer browsing – growth pattern – growth indices – age – temporal variations

 

Vila B., Vourc’h G., Gillon D., Martin J.L. and Guibal F., 2002. Is reaching browsing limit a matter of time in Picea sitchensis ? A chemical and dendroecological approach. Trees Structure and Function, 16 : 488-496.

Abstract - We combined chemical and dendroecological analyses to understand the mechanisms that are involved in escaping deer browse by young Sitka spruce (Picea sitchensis) exposed to browsing by Sitka black-tailed deer (Odocoileus hemionus sitchensis) on Haida Gwaii (British Columbia, Canada). We compared chemical defenses (terpenes), nutritive compounds (nitrogen, non structural constituents, cellulose, and lignin), as well as age and radial growth of two young spruce categories growing side by side: (1) "stunted spruces" that were heavily browsed, smaller than the browse line, and (2)"escaped spruces" that were taller than the browse line but still browsed below the browse line. Escaped and stunted spruces did not differ in terpene concentrations, or in nutritive compound contents, suggesting that they had similar palatability. Escaped spruces were older that stunted spruces. Stunted and escaped trees had similar slow growth when young, suggesting no difference in initial browsing between the two spruce categories. For escaped spruce, there was a dramatic increase in radial growth at about 12-13 years old suggesting that the apex of the trees had escaped deer browse. Because the two categories of spruces were all equally accessible and did not differ in chemical defenses or in nutritive compounds, and because escaped spruces were older than stunted trees and had a similar slow radial growth in their first 12-13 years old, we conclude that morphological differences between stunted and escaped browsed trees are due to age and that it is only a matter of time for spruce to escape deer on Haida Gwaii.

Keywords - Picea sitchensis (Bong.) Carrière- deer browsing - chemical defences - radial growth – age.

 

Vourc'h, G., B. Vila, D. Gillon, J. Escarré, F. Guibal, H. Fritz, T. P. Clausen, and J.-L. Martin., 2002. Disentangling the causes of damage variation by deer browsing on long-lived tree saplings. Oikos 98: 271-283.

Abstract - Long-lived trees experience different levels of damage due to mammalian herbivores. To untangle the mechanisms that underlie this variation, we combined chemical with dendrochronological analyses to study variation in browsing on Western redcedar (Thuja plicata) on Haida Gwaii (British Columbia, Canada). Since the last glaciation, Haida Gwaii forests had lacked large herbivore browser until Sitka black-tailed deer (Odocoileus hemionus sitkensis) were introduced at the beginning of the 20^th century. Dendrochronology yielded information on radial growth and plant annual responses to environmental stresses including herbivory. Secondary metabolite content and plant nutritional quality provided insights into proximate causes of food choices made by herbivores. We sampled lightly- and heavily-browsed young trees at four sites : three clear-cut sites with high browsing pressure and one old-growth forest site where browsing pressure had, until recently, been lower. Heavily-browsed young trees had secondary metabolites at lower concentrations and were of lower nutritive value than lightly-browsed trees at all sites. Under high browsing pressure, tree growth patterns suggested that all young trees were severely browsed until those that were currently lightly-browsed started to escape deer. At the old-growth site, both lightly- and heavily-browsed trees tended to have lower overall average secondary metabolite concentrations than those of all other sites. Furthermore, during the period of lower browsing pressure, lightly-browsed trees that were older, had a higher growth rate than heavily-browsed trees, but a similar year-to-year growth variation. This suggests that, under low browsing pressure, young trees with low levels of chemical defense were not strongly counter-selected and that differences in growth due to other factors than browsing could be expressed. Under strong browsing pressure however very young trees were equally browsed, and only those trees having the genetic potential to produce effective defenses may ultimately be able to escape deer. This suggests that selection by deer could occur on a long-lived tree.

 

Revues importantes des disciplines concernées (2^ème quartile)

Vila B., Keller, T. and Guibal F., 2001. Influence of browsing cessation on Picea sitchensis radial growth. Annals of Forest Science 58: 853-859.

Abstract - Picea sitchensis is an ecological and economical component of North America north temperate rain forest. On Haida Gwaii archipelago which is one of the most productive forest land of British Columbia (Canada), it is an important and valuable commercial species. The present study aims at precising deer browsing consequences on growth regeneration of Picea sitchensis. Using ring-width series, an empirical model is built which describes browsing impact on radial growth and removal of these pressure. Taking into account deer pressure and browsing upper limit when building predictive height growth models proves valuable for comparing growth pattern of different species under browsing pressure and deducing changes in forest dynamics.

Keywords - Picea sitchensis – radial growth – browsing – modeling – black-tailed deer.

 

Keller T., Edouard J-L., Guibal F., Guiot J., Tessier L., Vila B., 2000. Impact d’un scénario climatique de réchauffement global sur la croissance des arbres. Comptes Rendus de l’Académie des Sciences 323: 913-924.

English title – Impact of a climatic warming scenario on tree growth.

Abstract - The climatic impact on tree radial growth resulting from an atmospheric CO₂ doubling was studied for 24 populations of five tree species in the French Alps and the French Mediterranean area. The Arpege AGCM, which predicts a 3°C increase in mean temperature and a light increase of precipitation, is used to estimate the climatic perturbation. The method is based on the integration of estimated climate in an empirical tree-ring to climate model, involving artificial neural networks. Only a few populations are sensitive to the climatic change; all are located on the boundaries of their ecological area and can be divided in two groups. The first one is composed of high altitude populations which show a growth increase induced by the warmer climate during the growing season. The second one, composed of a single Mediterranean Scots pine population, reacts with a severe growth reduction induced by the stronger water stress in summer.

Keywords – tree-rings – response function – AGCM – global warming – CO₂ doubling – south-eastern France.

 

Autres publications

Vila B. and Guibal F., 2001. Assessing browsing influence in forest understory using dendrochronology on Haida Gwaii archipelago (British Columbia, Canada). Dendrochronologia, 19 (1) 139-151.

Abstract - The impact of introduced deer (Odocoileus hemionus sitchensis) on understory vegetation is assessed by analyzing browsed and non browsed individuals of a shrub (Gaultheria shallon) and a tree species (Picea sitchensis). Browsing is expressed in terms of morphology change, diameter growth patterns differences and traumatic anatomical characteristics occurrence on cross-sections.

At the impacted site, the upper browsing limit at a height of 1.10 m is evidenced. Abrupt growth change associated with scars can be evidenced on shrubs but a direct dendrochronological assessment of deer impact on shrub growth is not appropriate because of high inter-shrub variance in ring-width series. Deer impact can be assessed taking into account particular anatomical features as pith position, pith and stem form, wedging rings and scar occurrence for which impacted and non impacted populations differ statistically. Samples from the impacted population display non circular cross-sections with altered wood areas, eccentric piths and several discontinuous or wedging rings.

As regards with spruce, browsing pressure decreases apical growth and induces at severely browsed individuals a shrubby port. Narrow ring patterns are caused by browsing ; these patterns are followed by a sudden growth change occurring when herbivore pressure stops. That involves a lengthening of the recruitment period in windthrows which results in a delay of the habitat closing processes.

Keywords - disturbance - browsing - deer – abrupt growth change – traumatic characteristics

 

Vila B., Nicault A. et Vennetier M., 2001. Influence de la densité des peuplements sur la croissance en hauteur et radiale de Pinus sylvestris L. en région méditerranéenne française. Forêt Méditerranéenne tome XXII, N° 1: 65-74.

English title - Influence of the density on growth in height and diameter in stands of Pinus sylvestris L. in the French Mediterranean region.

Abstract – In naturally occurring irregular stands of Scots pine, competition better express as an index of competitivity rather than in terms of density or surface area, has a definite influence on the overall dendrometric growth parameters. Of the various factors monitored, competition favours growth in height. A threshold for both maximum and minimum densities has been evidenced, beyond which height growth falls. On the other hand, growth in diameter increases as competition drops. A comparison of growth in height and diameter of trees classified as "young" and "old", with the same cambium age, shows that trees grow faster today compared with fifty years ago. Thus, increased density in stands is not alone responsible for the observed increase in height growth. Considering the parameters of growth in height and diameter in tandem, the two types of growth are synchronic but the height growth lags behind diameter growth by one year. This gap is attributable to morphogenetic factors.

 

Vila B. et Lavagne A., 2001. Etude de la végétation du plateau de la Caume (Commune de Saint-Rémy, Alpilles orientales, Bouches-du-Rhône) : cartographie phytoécologique au 1/7000^ème. Bulletin de la Société Linéenne de Provence 52: 149-160.

English title - The vegetation of Plateau de la Caume – (Saint-Rémy, eastern Alpilles, Bouches-du-Rhône) : phytoecological cartography at 1/7000. Bulletin de la Société Linéenne de Provence 52: 149-160.

Résumé – Les auteurs proposent une cartographie phytoécologique au 1/7000^e du plateau de la Caume (Alpilles, Bouches-du-Rhône), un site présentant un intérêt botanique particulier à cause de la présence de certains groupements végétaux et d’espèces remarquables. Après un bref rappel de la place que jouent les Alpilles comme limite dans la répartition de certaines espèces et une mise au point sur les genres Ephedra et Genista présents sur le plateau, une comparaison est effectuée entre le présent travail et la carte établie par J. David 50 ans auparavant. Une lente remontée biologique (évolution progressive de la végétation) est mise en évidence. L’étude soulève de nombreuses questions relatives à la biologie de la conservation d’espèces trop méconnues qui constituent la richesse et la particularité du milieu.

 

Vila B., Guibal F. and J.L. Martin, 2001. Browsing influence in the understory of Haida Gwaii (B.C., Canada) forests using dendrochronology. Laskeek Bay Conservation Society: (10) 62-73.

Abstract - We assessed the impact of introduced deer on understory vegetation in some islands of Haida Gwaii by studying affected and control individuals of Salal, Red Huckleberry and Sitka Spruce. We analysed how browsing influences architecture, growth in diameter and the occurrence of traumatic anatomical features on cross-sections. For shrubs, a classical dendrochronological assessment of deer impact on growth has limited value because of high inter-shrub variance in ring-width series. However, samples from deer affected populations are characterized by abrupt changes in growth, that are associated with browsing scars, and by non circular cross-sections with altered wood areas, eccentric piths and several discontinuous or wedging rings. Deer affected and control populations differed statistically in these features. In spruce, severe browsing causes a shrubby growth form, with an overbranched crown and narrow growth rings. Browsing significantly decreases apical growth. When an individual tree becomes released from browsing, a sudden change in ring growth occurs. We studied the length of the time necessary for that change to occur and show that browsing induces, on average, an 8 year increase in the recruitment period in windthrows, delaying the process of habitat closing.

 

Articles soumis dans des revues majeures ou importantes (de 1^er et 2^ème quartile)

Vila B., Guibal F., Torre F. and Martin J.L. Can deer reshape forests ?

Abstract - We investigated how herbivores, which are recognized to influence forest composition, can, at high densities, override the effect of other environmental factors to induce drastic changes in forest composition. We studied the effect of the black-tailed deer (Odocoileus hemionus sitkensis) on the proportion of tree species in the forests of Haida Gwaii (British Columbia, Canada) by analyzing their impact on growth processes. Of the 3 dominant tree species growing on Haida Gwaii, we show that, in old growth forests, the regeneration of Picea sitchensis is the least affected whereas regeneration of Thuja plicata is entirely lacking. The better regeneration of Picea sitchensis is explained by the shorter delay it needs to reach the browse line and to escape deer browsing and by the vigor of its growth at release. In secondary forests also, Thuja plicata is the most affected by browsing but does achieve some regeneration. The combined impact of deer at seedling and sapling stages, will probably result in a low representation (secondary forest) or in the elimination (old growth forest) of Thuja plicata from the forests of Haida Gwaii and will change the ratio between Picea sitchensis and Tsuga heterophylla, especially in old growth forests.

Key words - over-browsing - growth phases – delay - tree response - forest compositional change - dendrochronology

Vila B., Guibal F., Martin J-L. and Torre F. Assessing the effect of deer browsing on Gaultheria shallon Pursh by ring analysis and wood anatomy.

Abstract - Black-tailed deer (Odocoileus hemionus sitkensis Merriam) was introduced on Haida Gwaii (Queen Charlotte Islands, British Columbia, Canada) in the early 20^th century and was not long to colonise most of the archipelago and to disturb the understory. We assessed the impact of browsing by deer on salal (Gaultheria shallon Pursh), a long lived shrub of the understory, by comparing adjacent islands in which deer were present (Reef Island) or absent (Low, South-Low Island). Salal plays an essential role in vegetation succession, habitat structuration, soil protection and ecology of several native animal species and could be used as an indicator of past and present deer impact. Annual radial growth and anatomical characteristics of salal were compared in the presence and in the absence of deer. High inter-individual variance in ring-width series makes crossdating difficult and precludes a direct assessment of browsing impact on growth. However, on the deer-affected island, salal stems are almost twice older (P < 0.01) (37.7 y) than on deer-free islands (19.6 y) and negative abrupt changes in radial growth are associated with scars caused by defoliation and shoot removal by deer. Thus, deer prevent stem recruitment, leading first to prolonged survival of existing stems and, after they die, to the elimination of salal from the understory. Deer browsing pressure on salal can be best assessed by the incidence of anatomical changes caused by browsing in section form, lobes (P < 0.001), pith form, pith position (P < 0.01) and the presence of decaying wood characterised by changes in texture and colours (P < 0.001). The frequency and distribution of these characteristics provides a novel way to reconstruct spatial and temporal interactions between woody plants and deer.

Key words - deer browsing - ring chronologies - negative abrupt growth change - anatomical characteristics - Gaultheria shallon Pursh

 

Vila B., Martin J.L., Guibal F. and Torre F. Deer impact on understory shrubs and its use to reconstruct browsing history: a methodological approach.

Abstract - We assessed the impact of browsing by black-tailed deer (Odocoileus hemionus sitkensis) on a common and deer sensitive long-lived shrub (the red huckleberry, Vaccinium parvifolium) on Haida Gwaii (British Columbia, Canada). We studied how deer impact can be used as a marker of deer abundance and fluctuation and a means to reconstruct the recent history of deer browsing. We compared islands with and without deer to identify how deer modified plant morphology, age structure and height, and to understand processes involved in these changes. In the absence of deer, individual plants are characterized by a large number of stems (7.8 ± 1.4) and by a low number of regenerating sprouts (0.9 ± 0.5) that will replace the older stems (ageing to 25.2 ± 1.9 years). In presence of deer regenerating sprouts are browsed and accumulate at the base of the plant (6.6 ± 1.1) and stems tall enough to escape deer will continue to grow and age (57.8 ± 2.3 years old). Ageing, stems eventually die off, leading to a reduction over time in the number of stems per individual and to the death of the plant. Site had no effect on stem age. Stem height had little value as an indicator of deer impact. The number of stems per age and height classes was a good indicator of deer browsing. In the case of the colonisation of new areas by deer, as in this study, such features can be used to assess the time when deer impact became prevalent. In our example deer became prevalent at least 40 years before this study. On Reef Island prevalence occurred 10 years before Louise and Haswell Islands although the latter were stepping stones of the former during the colonisation. This suggests that characteristics such as geographic isolation will affect the rate at which the impact increases.

Keywords - Vaccinium parvifolium Smith in Rees - shrub – deer – browsing – history – age structures - dendrochronology

 

Vila B., Guibal F., Torre F. and Martin J.L. Can we reconstruct browsing history and how far back? Lessons from Gaultheria shallon Pursh on Haida Gwaii.

Abstract – In order to reconstruct the history of black-tailed deer (Odocoileus hemionus sitkensis Merriam) browsing in temperate coniferous forests on Haida Gwaii (Queen Charlotte Islands, Canada) we compared age and height of salal (Gaultheria shallon Pursh) stems on islands with and without deer and along a north-south transect. Salal stems were two times older on islands with deer (29.9 years) than on islands without deer (16.0 years). On islands with deer we observed a deficit in stems in the youngest age classes which affected age structures and suggested that deer impact has been strong on these shrubs for the last 10 to 20 years. In addition to preventing stem recruitment deer browsing induced prolonged survival of existing stems. When these older stems will die, these salal shrubs will be eliminated from the understory. High site effect and the relatively low longetivity of salal make this shrub best adapted to reconstruct site specific deer impact over periods of only a few decades.

Keywords - Gaultheria shallon Pursh - deer browsing – age structures – browsing history – dendrochronology

Vila B., Torre F., Guibal F. and Martin J.L. Can we reconstruct browsing history and how far back? Lessons from Vaccinium parvifolium Smith in Rees on Haida Gwaii.

Abstract - We reconstructed the history of colonisation by black-tailed deer (Odocoileus hemionus sitkensis) over a significant section of a large archipelago situated in British Columbia (Canada) by studying present and past deer impact on a common and deer sensitive long-lived shrub, the red huckleberry (Vaccinium parvifolium). We used shrub features such as number of stems or regenerating sprouts, mean age and height of stems and stem age structures to compare browsing history between deer-free and deer-affected islands and to analyse spatial and temporal variation in deer impact within deer-affected islands. Deer by browsing regenerating sprouts stop stem replacement. On deer-affected islands the number of stems per individual shrub is 2 to 4 times lower than on deer-free islands, the number of regenerating sprouts is 8 to 15 times higher and stems are, on average, 2 to 3 times older. There was no variation in these shrub characteristics among deer-free islands, while characteristics varied both spatially and temporally among deer-affected islands revealing spatial and temporal variation in deer impact. Deer impact has been prevalent for at least 40-50 years before this study in all sites but one. In the latter, the most remote from the point of introduction, severe impact seems to date back to no more than 10 years before this study. However, on the basis of independant information, we interprete this difference as a possible consequence of differences in climate and habitat rather than to a delay in colonisation. Among the remaining sites, deer impact was widespread on Reef Island, Ramsay Island and Burnaby Island 10 to 20 years earlier than on Louise and Haswell Islands, although the two latter islands were stepping stones in the process of the colonisation of Reef Island and much closer to the point of introduction than Ramsay and Burnaby Islands. This suggests that factors such as geographic isolation (Reef Island and Ramsay Island), lack of extensive clear-cutting or lack of access to alpine summer range (Reef, Ramsay and Burnaby islands) may be factors that shorten the delay between colonisation and severe impact on the understory of old growth forests.

Keywords - Vaccinium parvifolium - shrub – deer – browsing – history – age structures - dendrochronology – context dependent impact

 

Vila B., Guibal F., Torre F. and Martin J.L. History of deer colonization as revealed by fraying scars.

Abstract - We studied fraying scars on two islands of Haida Gwaii, in order to document the history of island colonization by black-tailed deer (Odocoileus hemionus sitkensis). On Reef Island Thuja plicata was the tree species deer chose for fraying. On South Skedans Island where Thuja plicata is missing deer chose Salix sp and Alnus rubra. Deer chose only trees with a circumference inferior to 50 cm. About 2 to 3 fraying scars were recorded per tree. All of them extended between 30–40 cm and 70-80 cm from the ground. Fresh scars were between 5 and 6 cm in width. The age of scars did span over the last 50-60 years on Reef Island and over 10-15 years on South-Skedans Island. On Reef Island most scars were formed during the last 20 years (61.6%) and on South-Skedans Island most were formed over the last 10 years (95%). Age distribution of scars showed a constant increase of the number of scars over time and suggests that deer had already colonized Reef Island 53 years prior to this study but were absent or rare on South Skedans Island until 13 years prior to this study. These results suggest different colonization histories for the two islands. Results are consistent with those of studies on current differences in deer impact on the flora and fauna between these islands. Scars caused insect infestation and wood decay in Thuja plicata favoured by an absence of efficient compartmentalization and healing. For Salix sp and Alnus rubra effective compartmentalization and fast healing had limited pathogen infestation and wood discoloration.

Key words – deer colonization – dendrochronology - fraying scars – scars characteristics - damaged trees – island history

Communications à des colloques et conférences

Vila B., 2002. The impact of deer on woody plants : lessons from dendrochronology. International conference on Introduced species and what they tell us about how ecosystems work. Queen Charlotte City, Haida Gwaii, B.C., Canada. October 2 - 6, 2002.

Vila B., 2001. 200 ans de collections botaniques au muséum d’Aix. Conférence présentée au Muséum d’Histoire Naturelle d’Aix-en-Provence, le 12 mai 2001.

Vourc’h G, B. Vila, D. Gillon, J. Escarré, G. Guibal, H. Fritz, T. P. Clausen, and J.-L. Martin 2001. Who come first: the plant or the herbivore? An insight into the cause of differential deer browsing on long-lived trees. International Conference on Forest Dynamics and Ungulate Herbivory. Davos, Switzerland, October 3rd-6^th 2001.

Nicault A., Vila B. et Vennetier M., 2000. Influence de la densité des peuplements sur la croissance des pins sylvestres. Forêt Méditerranéenne : Journées d’étude et d’information sur le pin sylvestre. Comps-sur-Artuby, du 12 au 14 octobre.

Vila B. and Guibal F., 2000. Browsing influence in the understory of Haida Gwaii (B.C., Canada) forests using dendrochronology, poster presenté à l’International Conference on Dendrochronology for the third Millenium, Mendoza, Argentine, 2-7/04/2000.

Vourc’h G., Vila B., Gillon D., Clausen T. P., Escarré J. and Martin J.-L. 2000. Eat green but not any green. Consequences of herbivore introduction on a long-lived tree species. Ecological Society of America 85^th Annual Meeting. Snowbird, Utah, USA, August 5th-10th.

 

Rapports

Vila B., 2001. Collections de botanique : Principaux atouts des collections de botanique déposées au Muséum d’Histoire Naturelle d’Aix-en-Provence. Muséum d’Histoire Naturelle d’Aix-en-Provence, 21 p.

Nicault A. et Vila B., Vennetier M., Guibal F. et Edouard JL., 2000. Analyse de la croissance du pin sylvestre en région méditerranéenne. Influence du climat et de la densité des peuplements. Rapport ECOFOR: Forêts et changements climatiques. Division Agriculture et Forêt Méditerranéenne, Groupement d’Aix-en-Provence, 105 p.

Vila B. and Guibal F., 1999. Dendrochronological analysis of Gaultheria shallon Pursh: growth processes and disturbances caused by browsing in Haida Gwaii forests (British Columbia, Canada). Faculté des Sciences et Techniques de Saint-Jérome. Rapport interne 26 p.