Productivity of temperate broad-leaved forest stands differing in tree species diversity

? Understanding the effects of tree species diversity on biomass and production of forests is fundamental for carbon sequestration strategies, particularly in the perspective of the current climate change. However, the diversity-productivity relationship in old-growth forests is not well understood.

? We quantified biomass and above-ground production in nine forest stands with increasing tree species diversity from monocultures of beech to stands consisting of up to five deciduous tree species (Fagus sylvatica, Fraxinus excelsior, Tilia spp., Carpinus betulus, Acer spp.) to examine (a) if mixed stands are more productive than monospecific stands, (b) how tree species differ in the productivity of stem wood, leaves and fruits, and (c) if beech productivity increases with tree diversity due to lower intraspecific competition and complementary resource use.

? Total above-ground biomass and wood production decreased with increasing tree species diversity. In Fagus and Fraxinus, the basal area-related wood productivity exceeded those of the co-occurring tree species, while Tilia had the highest leaf productivity. Fagus trees showed no elevated production per basal area in the mixed stands.

? We found no evidence of complementary resource use associated with biomass production. We conclude that above-ground productivity of old-growth temperate deciduous forests depend more on tree species-specific traits than on tree diversity itself.

     

Sustainable development and sustainable forestry: analogies,differences, and the role of flexibility

Various approaches have been developed to achieve sustainability in forestry, under changing social needs and, consequently, changing definitions of sustainability. This has led to the confusing situation in which various groups have different understandings of the meaning of ‘sustainability’. Likewise, the concepts utilized to achieve sustainability, often with a poorly defined objective, are sometimes not clear and/or inconsistent as a systematic overview regarding definitions and concepts is lacking. Based on a literature review, this paper discusses related terms such as sustainability, sustained yield management, sustainable forestry, sustainable forest management and sustainable development: their history, concepts and relationships, from a European perspective. Finally, flexibility is proposed as a solution to overcome the identified shortcomings at all scales, while focussing on the enterprise level. The origin of the sustainability concept in forestry was first driven by forest experts, while participatory elements have been considered since the more recent idea of sustainable development. Since then, much effort has been made to achieve intragenerational fairness by creating an improved participatory process. Concurrently, the original idea of sustainable forestry as long-term and future-oriented management, considering future generations’ needs fell behind. An increasing standing timber volume in Europe and the discussion on climate change brought new interest in how to cope with risks in the context of pervasive future uncertainties within the scope of promoting sustainable development. Although the consideration of risk has been concentrated on as a topic in forest science in recent years, studies have mainly focused on the enhancement of forest resistance against disturbances. However, precaution and risk avoidance alone are probably insufficient to achieve an improved sustainable development that focuses on intergenerational fairness, as these more defensive approaches may disregard important management opportunities involved with an uncertain future. A perhaps more promising approach, the idea of future options and the ability to respond to changing social and biophysical circumstances (i.e. flexibility) as criteria for sustainable development have only shown a shadowy existence up to now. To further develop the consistency of sustainability concepts, a shift of sustainability approaches from continuity towards flexibility options is proposed.     

Identification of Avibacterium paragallinarum serovar B-1 from severe infectious coryza outbreaks in Panama

The isolation and identification of Avibacterium paragallinarum serovar B-1 from severe infectious coryza outbreaks in broiler breeders in Panama is reported for the first time. Infectious coryza was absent for over a decade in the breeder farms area. Disease outbreaks were characterized by an up to 45% drop in egg production and increased mortality. Use of a commercial trivalent bacterin and a strengthened biosecurity program prevented outbreaks in susceptible flocks in the farm.     

Pathogenicity determinants in smut fungi revealed by genome comparison

Biotrophic pathogens, such as the related maize pathogenic fungi Ustilago maydis and Sporisorium reilianum, establish an intimate relationship with their hosts by secreting protein effectors. Because secreted effectors interacting with plant proteins should rapidly evolve, we identified variable genomic regions by sequencing the genome of S. reilianum and comparing it with the U. maydis genome. We detected 43 regions of low sequence conservation in otherwise well-conserved syntenic genomes. These regions primarily encode secreted effectors and include previously identified virulence clusters. By deletion analysis in U. maydis, we demonstrate a role in virulence for four previously unknown diversity regions. This highlights the power of comparative genomics of closely related species for identification of virulence determinants.     

Dynamics of magnetic domain walls under their own inertia

The motion of magnetic domain walls induced by spin-polarized current has considerable potential for use in magnetic memory and logic devices. Key to the success of these devices is the precise positioning of individual domain walls along magnetic nanowires, using current pulses. We show that domain walls move surprisingly long distances of several micrometers and relax over several tens of nanoseconds, under their own inertia, when the current stimulus is removed. We also show that the net distance traveled by the domain wall is exactly proportional to the current pulse length because of the lag derived from its acceleration at the onset of the pulse. Thus, independent of its inertia, a domain wall can be accurately positioned using properly timed current pulses.     

Evidence for a collective intelligence factor in the performance of human groups

Psychologists have repeatedly shown that a single statistical factor--often called "general intelligence"--emerges from the correlations among people's performance on a wide variety of cognitive tasks. But no one has systematically examined whether a similar kind of "collective intelligence" exists for groups of people. In two studies with 699 people, working in groups of two to five, we find converging evidence of a general collective intelligence factor that explains a group's performance on a wide variety of tasks. This "c factor" is not strongly correlated with the average or maximum individual intelligence of group members but is correlated with the average social sensitivity of group members, the equality in distribution of conversational turn-taking, and the proportion of females in the group.