Large wild ungulates are a major biotic factor shaping plant communities. They influence species abundance and occurrence directly by herbivory and plant dispersal, or indirectly by modifying ...plant‐plant interactions and through soil disturbance. In forest ecosystems, researchers’ attention has been mainly focused on deer overabundance. Far less is known about the effects on understory plant dynamics and diversity of wild ungulates where their abundance is maintained at lower levels to mitigate impacts on tree regeneration. We used vegetation data collected over 10 years on 82 pairs of exclosure (excluding ungulates) and control plots located in a nation‐wide forest monitoring network (Renecofor). We report the effects of ungulate exclusion on (i) plant species richness and ecological characteristics, (ii) and cover percentage of herbaceous and shrub layers. We also analyzed the response of these variables along gradients of ungulate abundance, based on hunting statistics, for wild boar (Sus scrofa), red deer (Cervus elaphus) and roe deer (Capreolus capreolus). Outside the exclosures, forest ungulates maintained higher species richness in the herbaceous layer (+15%), while the shrub layer was 17% less rich, and the plant communities became more light‐demanding. Inside the exclosures, shrub cover increased, often to the benefit of bramble (Rubus fruticosus agg.). Ungulates tend to favour ruderal, hemerobic, epizoochorous and non‐forest species. Among plots, the magnitude of vegetation changes was proportional to deer abundance. We conclude that ungulates, through the control of the shrub layer, indirectly increase herbaceous plant species richness by increasing light reaching the ground. However, this increase is detrimental to the peculiarity of forest plant communities and contributes to a landscape‐level biotic homogenization. Even at population density levels considered to be harmless for overall plant species richness, ungulates remain a conservation issue for plant community composition.
The French forest ecosystem monitoring network (Renecofor) provided vegetation surveys resampled over 10 years, of 82 pairs of exclosure (no ungulate) and control plots. The analysis revealed that ungulates reduce the cover and richness of the shrub layers, and increase species richness of the herbaceous layer to the benefit of light‐demanding, ruderal and non‐forest species. We also show that the magnitude of vegetation changes is proportional to local deer abundances. The tremendous increase of wild ungulate populations throughout the Northern Hemisphere in the last decades has been altering not only the woody regeneration but also the diversity of herbaceous species.
Questions: (1) How do extreme climatic events and climate variability influence radial growth of conifers (silver fir, Norway spruce, Scots pine)? (2) How do elevation and soil water capacity (SWC) ...modulate sensitivity to climate? Location: The sampled conifer stands are in France, in western lowland and mountain forests, at elevations from 400 to 1700 m, and an SWC from 50 to 190 mm. Methods: We established stand chronologies for total ring width, earlywood and latewood width for the 33 studied stands (985 trees in total). Responses to climate were analysed using pointer years and bootstrapped response functions. Principal component analysis was applied to pointer years and response function coefficients in order to elucidate the ecological structure of the studied stands. Results: Extreme winter frosts are responsible for greater growth reductions in silver fir than in Norway spruce, especially at the upper elevation, while Scots pine was the least sensitive species. Exceptional spring droughts caused a notable growth decrease, especially when local conditions were dry (altitude<1000 m and SWC<100 mm for silver fir, western lowlands for Scots pine). Earlywood of silver fir depended on previous September and November and current-year February temperature, after which current June and July water supply influenced latewood. Earlywood of Norway spruce was influenced by previous September temperature, after which current spring and summer droughts influenced both ring components. In Scots pine, earlywood and latewood depended on the current summer water balance. Local conditions mainly modulated latewood formation. Conclusions: If the climate becomes drier, low-elevation dry stands or trees growing in western lowlands may face problems, as their growth is highly dependent on soil moisture availability.
Aim
Climate warming reshuffles biological assemblages towards less cold‐adapted but more warm‐adapted species, a process coined thermophilization. However, the velocity at which this process is ...happening generally lags behind the velocity of climate change, generating a climatic debt the temporal dynamics of which remain misunderstood. Relying on high‐resolution time series of vegetation data from a long‐term monitoring network of permanent forest plots, we aim at quantifying the temporal dynamics – up to a yearly resolution – of the climatic debt in the understorey of temperate forests before identifying the key determinants that modulate it.
Location
France.
Time period
1995–2017.
Taxa studied
Vascular plants.
Methods
We used the community temperature index (CTI) to produce a time series of understorey plant community thermophilization, which we subsequently compared to a time series of mean annual temperature changes over the same period and for the same sites. The direction and magnitude of the difference (i.e., the climatic debt) was finally analysed using linear mixed‐effect models to assess the relative contributions of abiotic and biotic determinants, including forest stand characteristics.
Results
We found a significant increase in CTI values over time (0.08–0.09 °C/decade), whereas the velocity of mean annual temperature changes was three times higher over the same period (0.22–0.28 °C/decade). Hence, the climatic debt increased over time and was greater in forest stands with higher basal area or older trees as well as under warmer macroclimate. By contrast, a greater frequency of anthropogenic disturbances decreased the climatic debt, while natural disturbances and herbivory had no impact.
Conclusions
Although often overlooked in understanding the climatic debt of forest biodiversity, changes in forest stand characteristics may modulate the climatic debt by locally modifying microclimatic conditions. Notably, the buffering effect of the upper canopy layer implies microclimate dynamics that may provide more time for understorey plant communities to locally adapt.
This study is one of very few dealing with the distribution and the origin of heavy metals in French soils from
a priori non-polluted forest areas. The abundance of heavy metals measured in these ...soils decreases as follows: Cr>Zn>Pb>Ni>Cu>Co≫Cd. Total concentrations of Pb, Cr and Ni in some soils exceed the European thresholds for non-polluted soils and even the French association of normalization critical values for sludge spreading. The lowest heavy metal contents are observed in acid soils while the highest concentrations are in the calcaric cambisol and in the mollic andosol, which is rather scarce as compared with the other French forest soils. With the exception of the podzol, Cr and Ni concentrations increase with depth in all soil profiles. The distribution pattern of Co, Cu, Zn depends on the soil characteristics. In some acid soils, however, Cu and Zn decrease with depth. Pb and Cd are accumulated in the upper soil horizons. Heavy metals accumulate in deep soil horizons in relation to important clay content in the dystric planosol and stagnic luvisol. The concentration of each heavy metal is always controlled by different parameters (soil pH, iron and aluminum oxide content, clay content, organic matter and cation exchange capacity), which are heavy metal specific. This study highlights the metal-trapping character of andosol and calcaric soil, the weak heavy metal retention in acid soils, the leaching and trapping character in leached clayed soils, and the migration of heavy metals in the podzol. Pb and Cr concentrations indicate a significant enrichment in surface horizons from various soils in areas which receive significant acid atmospheric pollution. Particularly, the highest Pb content is observed in a soil located in the N-NE part of France. Lead isotope ratios measured in the cambic podzol and the calcaric cambisol, exhibit the importance of the anthropogenic sources and particularly the influence of global atmospheric inputs from leaded gasoline compared to regional and local industrial emissions. The anthropogenic Pb contribution is estimated to 83, 30 and 11%, respectively, for surface, intermediate and deep horizons of the cambic podzol located in the northern part of France, and to 68% in surface horizon of the calcaric cambisol located in the Alps.
Vegetation phenology is the chronology of periodic phases of development. It constitutes an efficient bio-indicator of impacts of climate changes and a key parameter for understanding and modelling ...vegetation-climate interactions and their implications on carbon cycling. Numerous studies were devoted to the remote sensing of vegetation phenology. Most of these were carried out using data acquired by AVHRR instrument onboard NOAA meteorological satellites. Since 1999, multispectral images were acquired over the whole earth surface every one to two days by MODIS instrument onboard Terra and Aqua platforms. In comparison with AVHRR, MODIS constitutes a significant technical improvement in terms of spatial resolution, spectral resolution, geolocation accuracy, atmospheric corrections scheme and cloud screening and sensor calibration. In this study, 250 m daily MODIS data were used to derive precise vegetation phenological dates over deciduous forest stands. Phenological markers derived from MODIS time-series and provided by MODIS Global Land Cover Dynamics product (MOD12Q2) were compared to field measurements carried out over the main deciduous forest stands across France and over five years. We show that the inflexion point of the asymmetric double-sigmoid function fitted to NDVI temporal profile is a good marker of the onset of green-up in deciduous stands. At plot level, the prediction uncertainty is 8.5 days and the bias is 3.5 days. MODIS Global Land Cover Dynamics MOD12Q2 provides estimates of onset of green-up dates which deviate substantially from in situ observations and do not perform better than the null model. RMSE values are 20.5 days (bias -17 days) using the onset of greenness increase and 36.5 days (bias 34.5 days) using the onset of greenness maximum. An improvement of prediction quality is obtained if we consider the average of MOD12Q2 onset of greenness increase and maximum as marker of onset of green-up date. RMSE decreases to 16.5 days and bias to 7.5 days.
In Boulanger et al. (2018), we investigated the effects of ungulates on forest plant diversity. By suggesting a revisit of our conclusions regarding ecosystem dynamics since the late Pleistocene, ...Fløjgaard et al. (2018) came to the conclusion that moderate grazing in forest should be a conservation target. Since major points of our paper were mis‐ or over‐ interpreted, we put the record straight on our study system and on the scope of our conclusions. Finally, we advocate for an assessment of the conservation issues of ungulates in forests not only regarding hypothetical and still debated states of past ecosystems but also considering timely challenges for forest ecosystems.
After modeling the large-scale climate response patterns of leaf unfolding, leaf coloring and growing season length of evergreen and deciduous French temperate trees, we predicted the effects of ...eight future climate scenarios on phenological events. We used the ground observations from 103 temperate forests (10 species and 3,708 trees) from the French Renecofor Network and for the period 1997–2006. We applied RandomForest algorithms to predict phenological events from climatic and ecological variables. With the resulting models, we drew maps of phenological events throughout France under present climate and under two climatic change scenarios (A2, B2) and four global circulation models (HadCM3, CGCM2, CSIRO2 and PCM). We compared current observations and predicted values for the periods 2041–2070 and 2071–2100. On average, spring development of oaks precedes that of beech, which precedes that of conifers. Annual cycles in budburst and leaf coloring are highly correlated with January, March–April and October–November weather conditions through temperature, global solar radiation or potential evapotranspiration depending on species. At the end of the twenty-first century, each model predicts earlier budburst (mean: 7 days) and later leaf coloring (mean: 13 days) leading to an average increase in the growing season of about 20 days (for oaks and beech stands). The A2-HadCM3 hypothesis leads to an increase of up to 30 days in many areas. As a consequence of higher predicted warming during autumn than during winter or spring, shifts in leaf coloring dates appear greater than trends in leaf unfolding. At a regional scale, highly differing climatic response patterns were observed.
The area of French forest has grew by 60% in a century, and is at the fourth position on the European rank; Its harvesting was doubled at the same time; however the national trade-balance of the wood ...products sector is still in deficit. This forest is also facing important changes: climatic (composition and productivity of forest are affected, frequency and intensity of forest disturbances increase), societal (workers are fewer in the forest and we are more aware of benefits and services to society provided by forest) and bioeconomic (fossil resources decrease and we need of renewable materials). Wood is a versatile material which is renewable and can be used from construction, furniture to pulp and composite material, with a final recycling in energy. This cascading use of wood products enables a low carbon production of materials and energy, particulary effective for new challenges in bioeconomy. To address this joint challenge of stronger and differentiated demands on wood resource and threats and constraints on the forest, some innovations and research of the public forest service are presented in this paper. The diversity of solutions (in harvesting, silvicultural treatment, species, soil monitoring…) underlines the potential of innovations in forest management and the need to mix and transfer them.
Même si la surface de la forêt française a progressé de 60% en un siècle, la plaçant à la quatrième place au rang européen, que sa récolte a dans le même temps doublé, la balance commerciale du bois et des produits dérivés est la seconde déficitaire au niveau national. Cette forêt est également confrontée à d’importants changements : climatiques, pouvant faire varier sa composition et son étendue spatiale ; sociétaux, avec de moins en moins de main-d’oeuvre en forêt simultanément à une prise de conscience des nombreux services écosystémiques rendus par ces espaces naturels ; mais surtout mondiaux avec la diminution des ressources fossiles, qui peuvent être pour partie remplacées par ce matériau polyvalent qu’est le bois. Le bois est effectivement une ressource renouvelable qui peut répondre à différents besoins de nos sociétés (construction, meubles, emballage, papier, chimie, matériaux composites, énergie), avec une utilisation des produits en cascade, jusqu’à un recyclage final ou une valorisation énergétique, assurant une production de matière et d’énergie à faible niveau de dioxyde carbone, particulièrement efficace. Pour relever ce défi conjoint de demandes plus fortes et plus différenciées sur la ressource, et de menaces importantes sur son évolution, quels sont les leviers à la disposition des gestionnaires de la forêt publique ? Cet article présente quelques pistes d’innovations à l’interface entre recherche et gestion, qui explorent des solutions différentiées mais ciblées sur des attentes des gestionnaires. La diversité des exemples en exploitation, renouvellement des peuplements, sylviculture et suivi de la fertilité des sols, souligne la richesse des innovations potentielles et le besoin de les mêler pour répondre aux attentes de la société. La forêt publique est façonnée par l’homme depuis des siècles, permettons-lui ensemble de s’adapter, et de nous aider à relever le défi d’une société plus sobre, valorisant les matériaux renouvelables, tout en continuant à assurer les multiples services écosystémiques.
La plantation forestière est un outil important pour l’adaptation des forêts aux changements globaux. Les échecs parfois récurrents dans certains contextes, les coûts associés à la plantation, la ...pénibilité du travail pour les ouvriers forestiers ainsi que les impacts environnementaux parfois négatifs sont autant de facteurs qui freinent le recours à la plantation et peuvent ainsi limiter la capacité d’adaptation des forêts. Un ensemble de travaux ont été menés pour répondre aux besoins en innovation technique sur les méthodes de plantation exprimés par les praticiens. Ces travaux portent sur le processus d’innovation en sylviculture et sur l’amélioration technique des méthodes de plantation. L’analyse du processus d’innovation indique une faiblesse des réseaux sociotechniques associée à un mauvais partage des connaissances entre acteurs, et une réticence à l’investissement dans du nouveau matériel, dans un contexte économique perçu comme incertain. Ces observations suggèrent qu’un des leviers possibles serait une meilleure mise en réseau des acteurs, à travers différents liens fonctionnels: partage d’information, échanges de services, construction de partenariats économiques. Des exemples de méthodes innovantes pour réaliser chacune des différentes étapes de l’itinéraire de plantation (préparation du site, plantation, entretiens), répondant aux besoins d’innovation technique exprimés par les praticiens, sont ensuite présentés.
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