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KEYWORDS: Fire chronosequence, clonal growth, dendrochronology, Empetrum nigrum, sexual reproduction, fruit and viable seed production, chronoséquence de feux, croissance clonale, Dendrochronologie, reproduction sexuée, production de fruits et de graines viables
The relative importance of sexual reproduction and clonal growth for the long-term maintenance of crowberry populations is poorly understood. Our objective was to characterize reproductive output, recruitment and clonal growth in different populations along a fire chronosequence at the treeline. Our research hypothesis was that sexual reproduction would be more important in younger sites, but that clonal growth would be prevalent in older sites. We quantified cover and reproductive output and reconstructed the establishment chronology of the crowberry populations. The positive relationship between crowberry cover and site age is mainly attributable to the presence of a tree cover at older sites. Fruit production, lower in forested sites, and seed viability were not related to site age. Recruitment of individuals appeared to be relatively similar between sites, while the number of clonal individuals increased with the time elapsed since the last fire. Our results partially support our research hypothesis. While clonal growth is more important for population maintenance at older sites, the species keeps investing in sexual reproduction, even when dominant.
Bryophytes and pteridophytes are important contributors to ecosystem services in boreal regions. Abiotic agents are considered their main dispersers, but recent studies suggest that biotic agents including invertebrates, birds and large mammals might also be efficient dispersal agents. Dispersal of cryptogams by ground-dwelling small mammals is often assumed to occur, but has yet to be demonstrated. In this study, we present the first evidence of boreal cryptogam species being dispersed by ground-dwelling small mammals. In 2013 and 2014, we recorded bryophyte cover and fern presence in 35 sites in black spruce forest. We also collected diaspores by brushing the fur of 99 ground-dwelling small mammals live-trapped in the same sites. Diaspores were then germinated on nutrient agar for six months. Viable diaspores of five bryophyte species and one fern species were successfully grown. No association was found between the cryptogam community sampled on site and the diaspore community grown on artificial substrate. Unlike abiotic agents that randomly disperse cryptogams, small mammals are more likely to transport diaspores to suitable substrates where microhabitat requirements for germination are met. Our results highlight the need to consider a broad spectrum of dispersal agents when focusing on the community dynamics of cryptogams.
Traditional ecological knowledge (TEK) garners increasing attention in science-based wildlife management. We used the TEK of 16 First Nation hunters from the Eagle Village Algonquin community (Quebec, Canada) to evaluate moose (Alces americanus) habitat suitability in temperate deciduous forests, compared with a habitat suitability index (HSI) model. We found moderate to strong agreement between TEK and the HSI using Cohen's kappa (κ = 0.46–0.63). According to the Algonquin hunters, wetlands and lakes are frequented by moose to feed and to avoid temperature stress during warm summer days, something not taken into account by the HSI. Algonquin hunters also mentioned that unproductive areas are actively frequented by moose in the summer and during the rutting period, although they have a low weight in the HSI calculation. Also according to Algonquin hunters, mature coniferous stands and large-size regenerating areas are rarely used by moose. While the moose HSI model was developed in boreal mixed and coniferous forests, we have shown that it could also be used in temperate deciduous forests. It could be improved, however, to better correspond to TEK, notably by including wetlands and lakes, increasing the weight of unproductive stands and reducing weights of mature coniferous and regenerating stands.
Agro-ecosystem management focuses on developing grassland systems that meet sustainable productivity and biodiversity targets. Pasture management affects productivity and biodiversity, but the effects of previous management impacts are difficult to predict. Our objective was to identify the effects of key management factors and their timing on current biodiversity and productivity in public pastures in northeastern Japan. We surveyed pasture management histories (stocking rate, mowing frequency, fertilizer application and pasture renovation by plowing) from 1991 to 2010. We divided the data into periods and examined productivity, forage quality and biodiversity (plants and burrowing rodents). We included these parameters into generalized linear models, and found that recent fertilization level, mowing frequency and renovation were the most important factors affecting plant species diversity. In contrast, recent and past stocking rates were the dominant factors for productivity and forage quality, respectively. Thus, biodiversity and productivity were affected by different factors, suggesting that pasture management can balance the competing goals of biodiversity conservation and productivity improvement. From the effects of pasture management on biodiversity, forage productivity and quality, avoiding intensive pasture management is a practical application. In addition, a time lag effect of grazing pressure on forage quality should be considered during future pasture management.
A high-resolution sediment record from Lac Brûlé, southwestern Québec, was studied to determine the effects of long-term climate change and anthropogenic impacts on cladoceran assemblages of the late Holocene. Temporal shifts in cladoceran communities were closely associated with known century-scale climatic episodes, namely the Medieval Warm Period (750–1250 CE), the Little Ice Age (1450–1850 CE) and the twentieth-century warming. Forward selection indicated the importance of catchment variables and aquatic primary production in governing cladoceran communities. This suggests that higher trophic levels in Lac Brûlé were responsive to changes in the physical and chemical properties of the lake, perhaps as an indirect consequence of climatic change. The exploitation of the Wallingford-Back Mine in the immediate watershed of Lac Brûlé from 1924 to 1972 CE also had notable impacts on cladoceran assemblages. To strengthen interpretations of the Lac Brûlé record, relationships between cladoceran assemblages and limnological variables were studied in surface samples from 31 lakes from the surrounding region. This spatial analysis identified nutrients (phosphorus and nitrogen) and pH as the most influential variables driving changes in present-day cladoceran communities. However, the performance of cladocera-based inference models was insufficient to quantitatively reconstruct variables in the down-core analysis of Lac Brûlé.
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