Topographic Variation in Forest Expansion Processes across a Mosaic Landscape in Western Canada

Changes to historic fire and grazing regimes have been associated with the expansion of tree cover at forest–grassland boundaries. We evaluated forest expansion across a mosaic landscape in western Canada using aerial photos, airborne laser scanning, and field transects. The annual rate of forest expansion (0.12%) was on the low end of rates documented across North America and was greater from the 1970s to the 1990s than from the 1990s to 2018. Most forest expansion occurred within 50 m of established forests, and 68% of all tree regeneration in grasslands was within 15 m of the forest edge. The intensity of cattle grazing did not affect the tree regeneration density. Despite the slow pace of land cover change, grassland areas near the forest edge had an average of 20% canopy cover and 9 m canopy height, indicating the presence of tall but sporadic trees. The rate of forest expansion, density of tree regeneration, and tree cover within grasslands were all greater at lower elevations where trembling aspen (Populus tremuloides) and white spruce (Picea glauca) were the dominant tree species. We conclude that proportions of forest–grassland cover on this landscape are not expected to change dramatically in the absence of major fire over the next several decades.

Recruitment facilitation in expanding forests of Mediterranean juniper is sex-biased

Despite noticeable concern about the deforestation rate worldwide, the forest surface in Europe has considerably expanded over the past centuries as a consequence of the rural exodus and abandonment of agrarian practices. Tree recruitment associated with forest regrowth is a multi-stage process influenced by several biotic and abiotic factors. Yet, it is uncertain whether their influence on recruitment patterns and dynamics varies along a gradient of forest expansion. Similarly, for dioceious species, the influence of tree sex in recruitment is not entirely understood. Here, we aim to elucidate what drives Spanish juniper recruitment in expanding forests. Specifically, we hypothesized that facilitation by conspecifics and other woody species would occur at the expanding front, where environmental conditions are harsher and that recruitment would be preferably associated to female trees because of the likelihood of mature cones produced by them germinating in the nearby area. The study was conducted in Mediterranean forests of Juniperus thurifera in central Spain. A total of 17 plots were delimited along a gradient of forest expansion including: i) old forests, ii) an intermediate zone and iii) novel forests at the expanding front. Within each plot all J. thurifera individuals (saplings and adults) were mapped. We also recorded bio-volumetric characteristics and tree sex for all adult trees and estimated the percentage of cover of woody species within the area of influence of each adult individual. We analysed the spatial pattern of J. thurifera individuals for each stand (plot). Using a novel spatial approach, we evaluated how conspecific (female and male tree sizes) and heterospecific (woody cover) vegetation influenced sapling density along a forest expansion gradient. We also studied the effects of the stage of the forest expansion gradient and the sex of adult trees on the spatial association between adults and saplings. Our results showed that sapling recruitment was negatively influenced by conspecific adult size along the whole gradient, while the effect of heterospecific woody vegetation was always positive. Conspecific facilitation of recruitment in J. thurifera forests occurred at their expanding front where saplings were associated to male adult trees. Despite having been overlooked in conservation policies, recently colonised areas in extreme environments are key targets to implement management measures aimed at achieving forest restoration, which aligns with the Aichi targets and the biodiversity policies of the European Union.

Effect of the Forest-Mine Boundary Form on Woody Colonization and Forest Expansion in Degraded Ecosystems

We evaluated the ecological significance of the boundary form between two patches with contrasting vegetation (mine grassland and adjacent forest) on woody colonization and forest expansion in open-cast coal mines in Northern Spain. Woody colonization and browsing traces were measured on three mine sites, along 24 transects that were laid out perpendicular to the forest-mine boundary and classified according to their shape (concave, convex, straight). Mine sites were colonized from the close forest by woody species, whose colonization intensity depends on the boundary form. The overall colonization intensity decreased with increasing distance to the forest and differed depending on the boundary form. The more intense colonization was found in concave boundaries and the strongest decrease in convex boundaries close to the forest, whereas straight boundaries showed an intermediate colonization pattern. Concave boundaries reached higher woody cover in the basal strata of the mines than convex (up to 2 m) or straight boundaries (up to 1 m) from 11 m to the forest edge, mainly by the presence of dense patches of Cytisus scoparius (L.) Link, with a scattered overstory of Genista florida L. These shrubs might reduce the browsing intensity and act as nurse plants facilitating the establishment of Quercus petraea (Matt.) Liebl. in mine areas at greater distances from the forest edge. The forest-mine boundary form does not affect the forest vertical structure that is homogenous and does not help explain the woody colonization pattern in the mines. We conclude that edge characteristics have a strong potential to be used in the restoration of native forests based on natural processes. The implications of our results for sessile oak (Quercus petraea (Matt.) Liebl.) forest expansion along edges in fragmented Mediterranean forest landscapes were discussed.

Pre-Columbian palaeodemography in the Atlantic Forest (Brazil): evaluating the role and influence of extreme hydroclimatic oscillations

<p>The Atlantic Forest is a major biogeographic zone of Brazil, encompassing biodiverse evergreen, semi‐deciduous, and <em>Araucaria </em>forests. It is presently home to millions of people, and, consequently, has experienced high levels of defaunation/deforestation through fragmentation and habitat loss in recent years. A growing archaeological and palaeoecological consensus indicates growing anthropic influences on forest distribution during the pre-Columbian period, hand-in-hand with land use intensification and increasing social complexity over time. </p><p>Against this backdrop, this paper expands upon recent palaeodemographic work in South America to evaluate the role of long-term (centennial-scale) hydroclimatic oscillations (and the antiphasing thereof) in the Atlantic Forest domain as a potential "push factor" engendering human-driven forest expansion. It will synthesise archaeological, palaeoclimatological, and palaeoecological records, evaluate data quality, and identify areas for expansive future research. </p>

Forest Changes by Precipitation Zones in Northern China after the Three-North Shelterbelt Forest Program in China

China launched the Three-North Shelterbelt Forest Program (TNSFP) in 1978 in northern China to combat desertification and dust storms, but it is still controversial in ecologically fragile arid and semi-arid areas, which is partly due to the uncertainties of monitoring of the spatial-temporal changes of forest distribution. In this study, we aim to provide an overall retrospect of the forest changes (i.e., forest gain and forest loss) in northern China during 2007–2017, and to analyze the forest changes in different precipitation zones. We first generated annual forest maps at 30 m spatial resolution during 2007–2017 in northern China through integrating Landsat and PALSAR/PALSAR-2 data. We found the PALSAR/Landsat-based forest maps outperform other four existing products (i.e., JAXA F/NF, FROM-GLC, GlobeLand30, and NLCD-China) from either PALSAR or Landsat data, with a higher overall accuracy 96% ± 1%. The spatial-temporal analyses of forests showed a substantial forest expansion from 316,898 ± 34,537 km2 in 2007 to 384,568 ± 35,855 km2 in 2017 in the central and eastern areas. We found a higher forest loss rate (i.e., 35%) in the precipitation zones with the annual mean precipitation less than 400 mm (i.e., the arid and semi-arid areas) comparing to that (i.e., 25%) in the zones with more than 400 mm (i.e., the humid areas), which suggests the lower surviving rate in the drylands. This study provides satellite-based evidence for the forest changes in different precipitation zones, and suggests that the likely impacts of precipitation on afforestation effectiveness should be considered in future implementation of ecological restoration projects like TNSFP.

OCCUPATION STRATEGY OF THE ARBOREAL SPECIES Tachigali rubiginosa (MART. EX TUL.) OLIVEIRA-FILHO: EVIDENCE OF FOREST EXPANSION OVER GRASSLAND AREAS.

ABSTRACT Understanding the dynamics of forest species occupation in savanna and grasslands environments allows us to assess how forest expansion operates over time. For eleven years, the population dynamics of Tachigali rubiginosa (Mart. ex. Tul.) Oliveira-Filho was registered to evaluate the occupation strategy of this species in the ecotone between forest (Mata de Galeria) and grassland (Campo Sujo), located within the Capetinga stream basin, at Fazenda Água Limpa, Federal District. This area has been protected from wildfires since 1987. This study allocated thirty-one transects of 5 m x 100 m perpendicularly to the Capetinga stream, covering forest and grassland environments. The measurements were taken from adult trees (DBH ≥ 5 cm), young trees (height > 1 m and DBH < 5 cm) and seedlings (height ≤ 1 m and DBH < 5 cm). The results indicated that, in the studied period, the population of T. rubiginosa increased from 179.5 to 262.8 ind / ha. In 2007, of the total of 280 individuals in 1.56 ha, 96 of them were in the forest (0.22 ha), 103 in the ecotone (0.16 ha), and 81 in the grassland (1.18 ha). In 2018, this proportion changed when the number of individuals decreased in the forest (83 individuals), while the number increased in the ecotone (135 individuals) and in the grassland (194 individuals). In 2007, the young trees dominated with 71% of the total, followed by the adults trees (28.5%) and the seedlings (20.7%). In 2018, the young trees represented most individuals (39.2%), but there was a balance between the three size categories, as the seedlings represented 30.0% and adults trees 30.7%. Over the period of the study, there was an increase in the population of T. rubiginosa, especially of young individuals, which indicates persistence over time and an expansion of this forest species into grassland environments.

Insights from macroevolutionary modelling and ancestral state reconstruction into the radiation and historical dietary ecology of Lemuriformes (Primates, Mammalia)

The lemurs are a highly species-rich clade of primates, which, confined almost entirely to the island of Madagascar, have evolved to rival the diversity of rest of the primate order. We test the adaptive radiation model of Malagasy lemur diversity using a novel combination of phylogenetic comparative methods and geometric methods for quantifying tooth shape. We apply macroevolutionary model fitting approaches and disparity through time analysis to dental topography metrics associated with dietary adaptation, an aspect of mammalian ecology which appears to closely related to diversification in many clades. Metrics were also reconstructed at internal nodes of the lemur tree and these reconstructions were combined to generate dietary classification probabilities at internal nodes using discriminant function analysis. We used these reconstructions to calculate rates of transition toward folivory per million-year intervals. Finally, lower second molar shape was reconstructed at internal nodes by modelling the change in shape of 3D meshes using squared change parsimony along the branches of the lemur tree. Our analyses of dental topography metrics do not recover an early burst in rates of change or a pattern of early partitioning of subclade disparity. However, rates of change in adaptations for folivory were highest during the Oligocene, an interval of possible forest expansion on the island. Reconstruction of the molar morphologies corresponding to the ancestral nodes of the lemur tree suggest that this may have been driven by a shift toward defended plant resources.