Small but visible: Predicting rare bryophyte distribution and richness patterns using remote sensing-based ensembles of small models.

In Canadian boreal forests, bryophytes represent an essential component of biodiversity and play a significant role in ecosystem functioning. Despite their ecological importance and sensitivity to disturbances, bryophytes are overlooked in conservation strategies due to knowledge gaps on their distribution, which is known as the Wallacean shortfall. Rare species deserve priority attention in conservation as they are at a high risk of extinction. This study aims to elaborate predictive models of rare bryophyte species in Canadian boreal forests using remote sensing-derived predictors in an Ensemble of Small Models (ESMs) framework. We hypothesize that high ESMs-based prediction accuracy can be achieved for rare bryophyte species despite their low number of occurrences. We also assess if there is a spatial correspondence between rare and overall bryophyte richness patterns. The study area is located in western Quebec and covers 72,292 km2. We selected 52 bryophyte species with <30 occurrences from a presence-only database (214 species, 389 plots in total). ESMs were built from Random Forest and Maxent techniques using remote sensing-derived predictors related to topography and vegetation. Lee's L statistic was used to assess and map the spatial relationship between rare and overall bryophyte richness patterns. ESMs yielded poor to excellent prediction accuracy (AUC > 0.5) for 73% of the modeled species, with AUC values > 0.8 for 19 species, which confirmed our hypothesis. In fact, ESMs provided better predictions for the rarest bryophytes. Likewise, our study revealed a spatial concordance between rare and overall bryophyte richness patterns in different regions of the study area, which have important implications for conservation planning. This study demonstrates the potential of remote sensing for assessing and making predictions on inconspicuous and rare species across the landscape and lays the basis for the eventual inclusion of bryophytes into sustainable development planning.

Soil data for mapping paludification in black spruce forests of eastern Canada.

Soil data and soil mapping are indispensable tools in sustainable forest management. In northern boreal ecosystems, paludification is defined as the accumulation of partially decomposed organic matter over saturated mineral soils, a process that reduces tree regeneration and forest growth. Given this negative effect on forest productivity, spatial prediction of paludification in black spruce stands is important in forest management. This paper provides a description of the soil database to predict organic layer thickness (OLT) as a proxy of paludification in northeastern Canada. The database contains 13,944 OLT measurements (in cm) and their respective GPS coordinates. We collected OLT measurements from georeferenced ground plots and transects from several previous projects. Despite the variety of sources, the sampling design for each dataset was similar, consisting of manual measurements of OLT with a hand probe. OLT measurements were variable across the study area, with a mean ± standard deviation of 21 ± 24 cm (ranging from a minimum of 0 cm to a maximum of 150 cm), and the distribution tended toward positive skewing, with a large number of low OLT values and fewer high OLT values. The dataset has been used to perform OLT mapping at 30-m resolution and predict the risk of paludification in northeastern Canada (Mansuy et al., 2018) [1]. The spatially explicit and continuous database is also available to support national and international efforts in digital soil mapping.

Genetic signals of ancient decline in Aleppo pine populations at the species' southwestern margins in the Mediterranean Basin.

Microsatellite markers were used to characterize the structure of genetic diversity in natural Moroccan Aleppo pine (Pinus halepensis Mill.) populations, the most southwesterly marginal populations of the species in the Mediterranean Basin. Twenty-two natural populations and one artificial population, located in four regions covering most of the natural range of P. halepensis in the country, were sampled. Across this range, towards the south and west (and towards high altitudes) the populations become increasingly discrete and discontinuous. The nuclear microsatellite marker analysis suggests that a large proportion of the Aleppo pines in Morocco have derived from a single genetic lineage, represented by a central group of 11 of the examined populations located in the High and Middle Atlas Mountains. In addition, two smaller groups, represented by the marginal southwestern High Atlas populations, and three still smaller north / northeastern groups of populations located in the Rif and northeast Middle Atlas Mountains, could be genetically distinguished. Further, coalescence analysis of historical demographic population patterns suggests that ancient bottlenecks occurred in all of the natural populations. However, the population differentiation and genetic diversity levels we found were good (F(st) =15.47), presumably because of the species' good potential for long-distance dispersal of seeds and high invasive capacity, which appear to have maintained a state of stable near-equilibrium, meta-population dynamics since ancient times.