The benefits of plantations for wood production are well known, but it is unclear whether they have a clear negative effect on biodiversity, compared to natural forests. It is also unclear how overstory species identity (i.e., exotic, compared to native) would interact with the simple plantation effects on understory vegetation biodiversity. Here, we assessed bryophyte, lichen, and vascular plant diversity and composition in mono-specific and mixed plantations of exotic and native hybrid poplars (Populus spp.) and exotic and native spruces (Picea spp.). We compared these plantations to reference forests with similar overstory types (coniferous, deciduous, mixed) to those of the plantations in the southern boreal forest of Quebec. We also assessed whether the overstory species identity in plantations influenced understory vegetation biodiversity compared to reference forests. Our results show that plantations were not biological deserts, since mixed plantations contained similar bryophyte and vascular plant diversity as reference mixed native forests. The presence of native spruces and exotic poplars in mixed plantations increased bryophyte and vascular plant diversity respectively. This suggests that the influence of plantations on understory species diversity, compared to reference forests, was linked to the overstory species identity. Plantations were associated with ruderal plant species, while reference forests were composed of forest species. Bryophyte composition was similar in plantations and reference forests, while lichen species were only present in plantations. Our findings highlight that plantations, especially mixtures of white spruce and exotic poplar, are a promising option for planting strategies to enhance biodiversity.

Managed forests contribute to both economic and non-timber values, but the ecological role of managed, including planted, forests to biodiversity objectives at the landscape scale needs to be better understood. In this project in collaboration with J.D. Irving, Limited, we: 1) used airborne LiDAR and field data to identify terrestrial habitats; 2) monitored selected taxa by 18 stand type/seral stage habitat types in intensively and extensively managed forests and reserves; 3) assessed effects of management intensity on water quality and aquatic habitat; and 4) projected forest and wildlife habitat under planned management and natural disturbance scenarios. Taxa studied included songbirds, bryophytes and beetle species associated with mature-overmature forests, and several listed ground vegetation species. LiDAR-based enhanced forest inventory provided forest structure variables that improved bird habitat models and spatial predictions of bird habitat, metrics explaining bryophyte composition and richness, and variability in beetle abundance and richness. There was no evidence of negative landscape-level effects of increasing management intensity on bird communities in mature forest stands, suggesting that managed spruce-fir-tolerant hardwood landscapes provide habitat for bird species that need old forest. Richness, diversity, and composition of bryophyte guilds in reference stands in Mount Carleton Provincial Park unmanaged reserve did not differ from stands in the intensively managed District. The landscape focus and stratification into stand type/seral stages were important to understand habitat requirements. Catchments with greater forest management did not show any consistent signs of biological impairment from smaller to larger scales, and all sites had good or very good biological water quality based on the aquatic insect communities. This study helped to evaluate forest management effects on habitat areas, detected with airborne LiDAR data, that need to be addressed to enhance decision making processes.

Human disturbances lead to forest degradation and a drastic reduction in forest area. In Africa, the most affected continent by this phenomenon, selective cutting of trees remains the main forest management strategy. However, the effects of management on biodiversity are insufficiently known, particularly in Africa. We investigated how forest management affects tree species diversity, composition, size structure and carbon biomass of mature and juvenile trees in the sudanian domain of Senegal by comparing unmanaged forests and three types of managed forests, while considering the disturbance level of each stand. We collected floristic data on five and fifteen unmanaged and managed forest stands, respectively. We calculated species richness, the Shannon-Wiener diversity Index (alpha, beta and gamma), as well as carbon stocks of trees for each forest stand. Then we fitted linear models to estimate the differences between forest types for each index. We also analyzed tree size structure and species composition of highly valuable species. In total, 26,009 mature and juvenile trees in 183 species were recorded. Our findings showed that management status and disturbance level affect tree species in different ways and that disturbance level explains a greater proportion of the variation in species diversity than management status. Considering alpha, beta and gamma diversity, we found no significant association between any of these metrics and management status, for either mature or juvenile trees. Disturbance level was only significantly associated with the gamma diversity of mature trees. Species composition of juvenile trees of highly valuable species was significantly associated with both management status and disturbance level, unlike mature tree species composition where the associations were not significant. The distribution of mature tree diameter forms an inverted J-shape for each management category and disturbance level. However, neither the median tree diameter nor the median absolute deviation presented significant differences as a function of management status or disturbance level. For carbon stocks, none of the differences observed by management status and disturbance level are statistically significant. Our findings indicated that forest management in the sudanian zone affects species composition more than diversity and that mature trees respond differently than juvenile trees. Disturbances more than forest management were the underlying process for biodiversity changes both in managed and unmanaged forests. These findings suggest a better protection of unmanaged forests, and also a development of specific conservation action plans for highly valuable species, especially for species that are threatened at national or global levels in order to minimize their risk of local extinction.

Forest management can have major impacts on the dynamic of ecological communities, including shifts in reproduction and survival strategies in newly recruited individuals. This study aims to predict the probability of presence of saplings of various species in managed forests in the Sudanian domain of Senegal based on their functional traits. Data on functional traits and the main commercial and domestic uses of twenty high-socio-economic value species were collected, along with their presence-absence, in 12, 832 plots from twenty sites in Senegal's savannahs spanning four different types of forest management, including unmanaged forests, old managed forests, recently managed forests, and community reserve forests. Mixed logistic regression models were used to predict whether high-value species would be present in different forest management types, depending on their main uses, and regeneration, growth and reproduction functional traits. We hypothesised that forest management would favour species with more efficient colonising and competitive abilities, particularly at high levels of disturbance. Our findings demonstrated that unmanaged forests were more likely to host high-value species, regardless of their functional traits and main uses. These protected forests also hosted the greatest variety of regeneration functional traits, heights and uses. Old managed forests were more likely to host high-value species compared to recently managed and community reserve forests. Moreover, high-value species capable of vegetative regeneration and those with low maximum height were more likely to occur in all types of forests, but this trend was more pronounced under higher management and disturbance intensities. This study highlights that the availability of forest products can be optimised by encouraging management strategies that promote a diversity of functional traits rather than the selective harvesting of certain high-value species. Additionally, the temporal variation in the responses of tree species could be beneficial for forest management, with more diverse values of functional traits and more high-value species being present in older managed forests relative to newly managed forests. These results indicate that it is essential to promote forest resilience after management by protecting high-value species that have the potential to restore forest functional composition over time in managed forests.

Boreal landscapes face increasing disturbances which can affect cultural keystone species, i.e. culturally salient species that shape in a major way the cultural identity of a people. Given their importance, the fate of such species should be assessed to be able to act to ensure their perennity. We assessed how climate change and forest harvesting will affect the habitat quality of Rhododendron groenlandicum and Vaccinium angustifolium, two cultural keystone species for many Indigenous peoples in eastern Canada. We used the forest landscape model LANDIS-II in combination with species distribution models to simulate the habitat quality of these two species on the territories of three Indigenous communities according to different climate change and forest harvesting scenarios. Climate-sensitive parameters included wildfire regimes as well as tree growth. Moderate climate change scenarios were associated with an increased proportion of R. groenlandicum and V. angustifolium in the landscape, the latter species also responding positively to severe climate change scenarios. Harvesting had a minimal effect, but slightly decreased the probability of presence of both species where it occurred. According to the modeling results, neither species is at risk under moderate climate change scenarios. However, under severe climate change, R. groenlandicum could decline as the proportion of deciduous trees would increase in the landscape. Climate change mitigation strategies, such as prescribed fires, may be necessary to limit this increase. This would prevent the decrease of R. groenlandicum, as well as contribute to preserve biodiversity and harvestable volumes.

Mechanical site preparation (MSP) is used prior to planting to control competing vegetation and enhance soil conditions, particularly in areas prone to paludification. Tree planting density can be adapted to the management context and objectives, as it influences yield and wood quality. However, the combined effects of MSP and planting density on understory vegetation composition, functional traits, and diversity remain uncertain. We thus conducted a study in the Clay Belt region of northwestern Quebec, Canada. After careful logging, the study area was divided into nine sites, each receiving one of three treatments: plowing, disc trenching, or no preparation. Sites were further divided into two, with black spruce (Picea mariana [Mill.] Britton, Sterns & Poggenb.) seedlings planted at either a low planting density of 1100 seedlings ha-1 or a high planting density of 2500 seedlings ha-1. After nine years, we assessed understory composition, diversity, key functional traits, sapling density and growth of planted trees. Careful logging alone led to a higher density of naturally established conifers compared to plowing or disc trenching. The interaction between planting density and MSP significantly influenced understory diversity and composition in plowed plots. Understory composition was affected by the soil C/N ratio, coniferous species, and deciduous species density. The growth of black spruce was notably enhanced with higher planting density in the plow treatment only. Neither planting density nor MSP alone affected tree height and diameter. Our results suggest that combining plowing with high-density planting can enhance stand growth and improve forest productivity. These findings guide future research on paludified forests.

The natural disturbance-based management (NDBM) aims to maintain specific structural and compositional attributes of natural forests in managed stands. Operationally, NDBM relies on diversifying and adapting silvicultural practices, including partial harvesting (PC), to expand the range of options beyond that of simply clearcuts (CC).