Maintaining floristic diversity in recognized biodiversity hotspots is a priority for ecosystem conservation. However, different taxonomical treatments often lead to over or underestimation of floristic diversity in species-rich groups, in particular in Tropical regions as Mesoamerica where floristic surveys are less detailed. Also, understanding the effects of climate changes on species distribution is an emerging question of conservation biology and ecological studies. Here, we used the species-rich genus Piper (Piperaceae) in Veracruz, as a model system to compare reported and actual species richness and to model their occurrence under a climate change scenario. We compared morphological characters of specimens preserved in three of the main Mexican herbaria and then applied new taxonomical treatments. We also used environmental niche models (ENMs) as implemented in Maxent to detect the effects of climate changes on species with different levels of habitat specificity and with specialized biotic interactions. We found that from a total of 108 Piper species reported in Veracruz, 80 were consistent to the new taxonomical treatments due to synonymy or misidentification. ENMs showed that the main determinants of Piper distribution are linked to temperature and precipitations depending on the species. Therefore, different species are likely to respond differently to climate changes. As expected, species with higher habitat specificity and species exhibiting specialized mutualisms are more likely to experience niche contractions. This study shows the importance of reconsidering species richness and of modelling species distribution including specialized ecological interactions as prerequisite for establishing conservation criteria.

At the end of the last glacial period in the northern hemisphere, meltwater from receding ice sheets accumulated into large proglacial lakes, potentially limiting postglacial afforestation. We explored whether former islands of proglacial Lake Ojibway (Canada) (hilltops in the current landscape) could have acted as migration outposts and thus accelerated the postglacial migration. We extracted sediments from two small lakes located on “paleo-islands” and used XRF to detect changes in soil erosion and vegetation biomass. We also used plant macro-remains and wood charcoal to determine if (and which) tree species colonized the sites and to detect local fire events. Organic sediment accumulation started around 9657 and 9947 cal. yr BP at Lakes Perché and Despériers, respectively, before the level of Lake Ojibway started to decrease and liberate parts of the studied landscape ca 9400 cal. yr BP. Lithogenic elements (Ti, K, Sr, Fe, Zr, and Rb) decreased between the beginning of organic sediment accumulation and 8800–8700 cal. yr BP, indicating reduced soil erosion, possibly due to soil stabilization by vegetation. Then, the S/Ti ratio, a proxy of organic matter increased around 8800 and 8400 cal. yr BP. The earliest tree macro-remains (Larix laricina and Pinus spp.) were found between 9850 and 9500 cal. yr BP. Local fires were detected around 9820 and 8362 cal. yr BP. Early afforestation occurred on the islands of Lake Ojibway, 200 and 450 years before its level started to decrease, confirming that some islands acted as migratory outposts accelerating postglacial migration.

Dry and warm conditions have exacerbated the occurrence of large and severe wildfires over the past decade in Canada’s Northwest Territories (NT). While temperatures are expected to increase during the 21st century, we lack understanding of how the climate-vegetation-fire nexus might respond. We used a dynamic global vegetation model to project annual burn rates, as well as tree species composition and biomass in the NT during the 21st century using the IPCC’s climate scenarios. Burn rates will decrease in most of the NT by the mid-21st century, concomitant with biomass loss of fire-prone evergreen needleleaf tree species, and biomass increase of broadleaf tree species. The southeastern NT is projected to experience enhanced fire activity by the late 21st century according to scenario RCP4.5, supported by a higher production of flammable evergreen needleleaf biomass. The results underlie the potential for major impacts of climate change on the NT’s terrestrial ecosystems.

Abstract Climate change is expected to increase wildfire activity in boreal ecosystems, thus threatening the carbon stocks of these forests, which are currently the largest terrestrial carbon sink in the world. Describing the ecological processes involved in fire regimes in terms of frequency, size, type (surface vs. crown) and severity (biomass burned) would allow better anticipation of the impact of climate change on these forests. In Fennoscandia, this objective is currently difficult to achieve due to the lack of knowledge of long-term (centuries to millennia) relationships between climate, fire and vegetation. We investigated the causes and consequences of changes in fire regimes during the Holocene (last ~11,000 years) on vegetation trajectories in the boreal forest of northern Finland. We reconstructed fire histories from sedimentary charcoal at three sites, as well as vegetation dynamics from pollen, moisture changes from Sphagnum spore abundance at two sites, and complemented these analyses with published regional chironomid-inferred July temperature reconstructions. Low-frequency, large fires were recorded during the warm and dry mid-Holocene period (8500–4500 cal. year BP), whereas high-frequency, small fires were more characteristic of the cool and wet Neoglacial period (4500 cal. year BP onward). A higher proportion of charcoal particles with a woody aspect—characterizing crown fires—was recorded at one of the two sites at times of significant climatic and vegetational changes, when the abundance of Picea abies was higher. Synthesis. Our results show both a direct and an indirect effect of climate on fire regimes in northern Fennoscandia. Warm and dry periods are conducive to large surface fires, whereas cool and moist periods are associated with small fires, either crown or surface. Climate-induced shifts in forest composition also affect fire regimes. Climatic instability can alter vegetation composition and structure and lead to fuel accumulation favouring stand-replacing crown fires. Considering the ongoing climate warming and the projected increase in extreme climatic events, Fennoscandian forests could experience a return to a regime of large surface fires, but stand-replacing crown fires will likely remain a key ecosystem process in areas affected by climatic and/or vegetational instability.

Major socio-economic changes over the last few decades have reduced Indigenous peoples’ engagement in cultural practices, such as harvesting of forest resources. Nevertheless, some species remain important for culture, subsistence and livelihood, such as the chiuri tree (Diploknema butyracea (Roxb.) H. J. Lam) to the Chepang people of Central Nepal. Using the cultural keystone species framework, we conducted interviews within Chepang communities to assess the biocultural importance of the chiuri tree. It is central to the Chepang culture, and no other species could provide the same benefits. It also provides food and habitat for a number of wildlife species, including bats, which are themselves culturally important. Strictly observed tree ownership rules, as well as a cultural ban on tree cutting and branch lopping, have so far contributed to chiuri conservation. However, these rules are increasingly less adhered to. Other threats to chiuri sustainability are excessive flower foraging by bees (reducing pollen production) and bat hunting (reducing pollen transport). Further studies are needed to quantify these threats and to adjust forest and wildlife management practices so that the cultural landscape continues to provide multiple benefits to the Chepang people. Our study of the chiuri case attests to the usefulness of the cultural keystone species framework in landscape assessment for management and conservation.

Interspecific interactions can mediate site occupancy of sympatric species and can be a key factor in habitat use patterns. American martens (Martes americana) and Fishers (Pekania pennanti) are two sympatric mesocarnivores in eastern North American forests. Due to their larger size, fishers have a competitive advantage over martens. We investigated site occupancy of martens and fishers in temperate deciduous forests of Québec, an environment modified by forest management and climate change. We formulated hypotheses on the spatial distribution of the studied species based on the knowledge of local trappers and on the scientific literature regarding forest cover composition, habitat fragmentation, and competitive relationships. We used a network of 49 camera traps monitored over two fall seasons to document site occupancy by both species. We used two-species site occupancy models to assess habitat use and the influence of fishers on martens at spatial grains of different sizes. None of the habitat variables that we considered explained site occupancy by fishers. Availability of dense old coniferous stands explained the spatial distribution of martens both at the home range grain size and at the landscape grain size. We identified the characteristics of habitat hotspots based on the knowledge of trappers, which highlighted the importance of stand composition, height, age, and canopy closure. The characteristics of habitat hotspots for martens in temperate deciduous forests refine the habitat suitability model for American martens that was originally developed for boreal forests of Québec.

En 2013, le gouvernement du Québec a introduit un nouveau régime forestier qui a transformé la dynamique dans la gouvernance de la forêt publique. Parmi les changements apportés, l’État est désormais chargé de planifier et de gérer les activités d’aménagement forestier.

L’aménagement forestier comprend des activités commerciales et non commerciales. De 1986 à 2013, le gouvernement attribuait aux entreprises forestières des volumes de bois à long terme au moyen de « contrats d’approvisionnement et d’aménagement forestier » (CAAF). Ces entreprises avaient également la responsabilité d’assurer les travaux sylvicoles non commerciaux visant la régénération des peuplements forestiers. La Loi sur l’aménagement durable du territoire forestier, en vigueur depuis 2013, a transformé en profondeur l’organisation des activités dans ce secteur. Sur le plan des activités commerciales, l’octroi de CAAF est remplacé par des « garanties d’approvisionnement », lesquelles confèrent à leurs bénéficiaires un volume de bois de la forêt publique à des fins de transformation. Sur le plan des activités non commerciales, l’État assume désormais l’entière responsabilité de la planification et de la gestion des opérations, jadis confiée aux titulaires de CAAF.

À partir de données empiriques, ce texte met en lumière la façon dont le régime forestier instauré en 2013 a permis l’émergence d’acteurs, exogènes au champ du droit du travail, dont les pratiques et les schémas d’action façonnent aujourd’hui les conditions de travail des ouvriers et des ouvrières sylvicoles effectuant des tâches non mécanisées. Cette main-d’oeuvre effectue des opérations d’éducation de peuplement au moyen d’une scie débroussailleuse ainsi que du reboisement. Les acteurs identifiés interviennent dans la dynamique d’attribution et de supervision des contrats de travaux sylvicoles non commerciaux et jouent un rôle de contrôle et de surveillance des conditions de travail, laissant aux parties à la relation d’emploi un pouvoir limité.

Précis

En 2013, le gouvernement du Québec a introduit un nouveau régime forestier sur fond de crise sociale alors que plusieurs estimaient que l’exploitation de la forêt se faisait de façon erratique et sans égards aux écosystèmes et communautés s’y établissant. L’un des objectifs poursuivis par le nouveau régime forestier était notamment de mettre en place une gestion forestière assurant le développement du « potentiel économique, écologique et social des forêts ». Qu’en est-il toutefois des conditions de travail de la main-d’oeuvre assurant la régénération des peuplements forestiers? À partir de données empiriques, ce texte explore la façon dont la détermination des conditions de travail des ouvriers et des ouvrières sylvicoles dépend de l’intervention d’acteurs exogènes au champ du droit du travail.