After more than a century of research the typical growth pattern of a tree was thought to be fairly well understood. Following germination height growth accelerates for some time, then increment peaks and the added height each year becomes less and less. The cross sectional area (basal area) of the tree follows a similar pattern, but the maximum basal area increment occurs at some time after the maximum height increment. An increase in basal area in a tall tree will add more volume to the stem than the same increase in a short tree, so the increment in stem volume (or mass) peaks very late. Stephenson et al. challenge this paradigm, and suggest that mass increment increases continuously. Their analysis methods however are a textbook example of the 'ecological fallacy', and their conclusions therefore unsupported.

Global warming is forcing many species to shift their distributions upward, causing consequent changes in the compositions of species that occur at specific locations. This prediction remains largely untested for tropical trees. Here we show, using a database of nearly 200 Andean forest plot inventories spread across more than 33.5° latitude (from 26.8° S to 7.1° N) and 3,000-m elevation (from 360 to 3,360 m above sea level), that tropical and subtropical tree communities are experiencing directional shifts in composition towards having greater relative abundances of species from lower, warmer elevations. Although this phenomenon of 'thermophilization' is widespread throughout the Andes, the rates of compositional change are not uniform across elevations. The observed heterogeneity in thermophilization rates is probably because of different warming rates and/or the presence of specialized tree communities at ecotones (that is, at the transitions between distinct habitats, such as at the timberline or at the base of the cloud forest). Understanding the factors that determine the directions and rates of compositional changes will enable us to better predict, and potentially mitigate, the effects of climate change on tropical forests.

No abstract

ABSTRACT. Forest Landscape Restoration (FLR) involves the ecological restoration of degraded forest landscapes, with the aim of benefiting both biodiversity and human well-being. We first identify four fundamental principles of FLR, based on previous definitions. We then critically evaluate the application of these principles in practice, based on the experience gained during an international, collaborative research project conducted in six dry forest landscapes of Latin America. Research highlighted the potential for FLR; tree species of high socioeconomic value were identified in all study areas, and strong dependence of local communities on forest resources was widely encountered, particularly for fuelwood. We demonstrated that FLR can be achieved through both passive and active restoration approaches, and can be cost-effective if the increased provision of ecosystem services is taken into account. These results therefore highlight the potential for FLR, and the positive contribution that it could make to sustainable development. However, we also encountered a number of challenges to FLR implementation, including the difficulty of achieving strong engagement in FLR activities among local stakeholders, lack of capacity for community-led initiatives, and the lack of an appropriate institutional and regulatory environment to support restoration activities. Successful implementation of FLR will require new collaborative alliances among stakeholders, empowerment and capacity building of local communities to enable them to fully engage with restoration activities, and an enabling public policy context to enable local people to be active participants in the decision making process.

I quantified monthly variation in species composition and captures of birds in a premontane forest of northwestern Argentina. Seasonal patterns of frugivore-insectivores and nectarivores were compared with fruit and flower abundances, respectively. The composition of the entire bird community fluctuated seasonally; frugivore-insectivores showed a peak in captures during the wet season, insectivores peaked at the end of the dry season, and nectarivores peaked during the dry season. At a local scale (∼50 ha), captures of frugivore-insectivores were not correlated with number of plant species with ripe fruits for any vegetation stratum considered, but were correlated with a fruit phenology index that considers crop size. At a plot scale (∼7.5 ha), only understory flower abundance and captures of nectarivores were correlated, but only in the plot where both were more abundant. At a net-site scale (50 m2), captures of the Rufous-bellied Thrush (Turdus rufiventris) were correlated with understory fruit abundance, but only in the plot where fruits were more abundant. These results suggest that seasonal fluctuations in birds may be driven to some extent by their food resources. Premontane forest provides habitat for many migrants and also presumably acts as a source of birds that emigrate to disturbed areas. Although premontane forests should be a conservation priority for the region, they are poorly protected and suffering high deforestation.