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In recent decades, most subalpine hay meadows and pastures have been abandoned, and trees have been recolonizing these sites where forest existed before agricultural activity. This study examined how woody vegetation, dominated by the deciduous fleshy-fruited tree Sorbus aucuparia (rowan), expanded on subalpine meadows in the Western Bieszczady Mountains (eastern Carpathians, Poland) after the cessation of agricultural use. The aims were to determine the abundance of rowan in the woody vegetation, to estimate the rate of rowan expansion in the studied area, and to characterize the variability of rowan stands and growth forms. Rowan dominated the current plant community of abandoned subalpine meadows, though this species is not considered a rapid colonizer of open areas and was not frequent in the uppermost forest belt before the colonization. The whole area was encroached by rowans in a very short period of time 60-70 years ago. Rowan tree density was similar throughout the elevational gradient but the growth form changed, becoming more shrub-like with increasing elevation. Rowan stands will likely be the main element of the subalpine belt in this region in the upcoming decades. At present, no tree species can be considered a rapid successor to rowan in the area.

Production of wood charcoal is a traditional form of forest use that lasted for millennia in the Mediterranean countries. Following their almost complete abandonment in the last century, thousands of old charcoal platforms remain in present-day forest landscapes. These sites are characterized by peculiar ecological conditions, whose effects on the recolonization by woody plants are still unknown. We examined 61 platforms in evergreen sclerophyllous woodlands and deciduous broadleaf forests with oaks and beech, spread over a wide geographic range in Tuscany (Italy). At each site, one kiln plot (on charcoal platform) and one control plot (in the adjacent stand) were established, and soil, light conditions and herb cover were measured. We examined species richness and composition of trees and shrubs in the understorey layer ( 1.3-4 m). In the latter, structural parameters such as number of stools, dbh, mean height and number of stems were compared. The density of seedlings of dominant tree species in the understorey was also measured in a subsample of sites per forest type. In the understorey, a general positive effect of kiln platforms was found on species richness at both the habitat and plot-scale level, as well as on species composition, especially in oak forests. Increased light availability, total C content and soil pH were positively related with species richness, while N content was a negative predictor. Density of seedlings was not substantially affected. Contrastingly, woody species richness in the established regeneration layer was considerably lower in the kiln plots of all three forest types. In sclerophyllous forests, all species in this layer were taller, denser and with a higher basal area compared to control plots, while regeneration was completely lacking on platforms of the two other forest types. Soil N content had a positive influence on structural parameters, while total C content resulting from charcoal accumulation had a negative influence. We conclude that charcoal platforms are a favorable microhabitat only in the first regeneration stages of woody species, as their further growth is hindered by long-term effects that should be investigated with an experimental approach.

This research has examined the genetic consequences of colonization in five tree species on the Krakatau islands, Indonesia after habitat had been destroyed over a century earlier by extreme volcanic events. The Krakatau islands provide a unique, well-documented example of island colonization in the tropics. The islands are continental and lay approximately midway between Java and Sumatra; the nearest points on these landmassess to the islands being approximately 41 and 31 km, respectively. Currently the islands are covered in species poor, early seral monsoonal forest that is little disturbed by humans. With the increasing levels of habitat destruction occurring in the tropics due to human mediated environmental degradation, it is important to understand the processes involved in ecosystem restoration. This is the first study to use genetic markers to examine the genetic consequences and patterns of colonization on these islands. The final conclusions of this study are these: Species dispersal ability, distance to the islands, island positioning and ecological factors are all important in structuring genetic diversity. Species with high dispersal ability maintain higher levels of genetic diversity within populations and lower levels of differentiation between populations relative to species with poorer dispersal ability. Dispersal ability alone was not a good predictor for the effect of colonization on genetic diversity within populations as other ecological factors are also important in structuring genetic variation. Counter to expectation, most of the study species maintained equivalent or higher levels of genetic diversity on Krakatau relative to mainland sites and other islands in the Sunda Strait closer to the coast. Small plant population size and island isolation is thought to be an important factor leading to hybridization in some species.