Many types of vegetation have more or less ground cover and recruitment of new individuals often occurs only in temporarily empty patches or gaps. Ever since Watt’s (1947) Presidential address to the BES, the Journal of Ecology has been publishing the results of investigations into the importance of processes in such gaps in the determination of community structure. Three recent papers from Norway, the UK and the USA (Vandvik 2004, Turnbull et al. 2004 and Ewanchuk and Bertness, 2004, respectively - all in volume 92, issue 1), report different approaches to addressing this issue.
Working in salt marches in New England, USA, Ewanchuk and Bertness show that the recolonisation of gaps generated by ice scour is slow and driven by competitive processes. Parts of these marshes consist of patches of sparse, but species-rich, vegetation dominated by non-grassy herbaceous plants (forbs). These areas were found to be inhospitable to plants which grew well nearby, suggesting physical limitation at the local scale, while the forbs were restricted to these patches by interspecific competition.
Vandvik showed that revegetation of gaps in subalpine grassland in Norway depended upon gap size and grassland age along a gradient of secondary succession. The degree to which individual species depended on gaps for regeneration changed as the disturbance regime altered during succession, with such gap phase processes being important for a majority (74%) of species in the system. Taking a more mechanistic and small-scale approach, Turnbull et al. also found that most species of annuals in a limestone grassland showed a preference for colonizing unvegetated patches. Through a series of exacting and careful measurements of individual plants and neighbourhood modeling they derived individual-level competition coefficients for seven annuals. Seed size was found to be a key trait determining both competitive and colonizing ability.
Becky Allen | alfa
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Successful calculation of human and natural influence on cloud formation
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Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
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Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
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