University of Exeter

About: University of Exeter is a education organization based out in Exeter, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 15820 authors who have published 50650 publications receiving 1793046 citations. The organization is also known as: Exeter University & University of the South West of England.

Reconciling the temperature dependence of respiration across timescales and ecosystem types

Abstract: Ecosystem respiration is the biotic conversion of organic carbon to carbon dioxide by all of the organisms in an ecosystem, including both consumers and primary producers. Respiration exhibits an exponential temperature dependence at the subcellular and individual levels, but at the ecosystem level respiration can be modified by many variables including community abundance and biomass, which vary substantially among ecosystems. Despite its importance for predicting the responses of the biosphere to climate change, it is as yet unknown whether the temperature dependence of ecosystem respiration varies systematically between aquatic and terrestrial environments. Here we use the largest database of respiratory measurements yet compiled to show that the sensitivity of ecosystem respiration to seasonal changes in temperature is remarkably similar for diverse environments encompassing lakes, rivers, estuaries, the open ocean and forested and non-forested terrestrial ecosystems, with an average activation energy similar to that of the respiratory complex (approximately 0.65 electronvolts (eV)). By contrast, annual ecosystem respiration shows a substantially greater temperature dependence across aquatic (approximately 0.65 eV) versus terrestrial ecosystems (approximately 0.32 eV) that span broad geographic gradients in temperature. Using a model derived from metabolic theory, these findings can be reconciled by similarities in the biochemical kinetics of metabolism at the subcellular level, and fundamental differences in the importance of other variables besides temperature—such as primary productivity and allochthonous carbon inputs—on the structure of aquatic and terrestrial biota at the community level.

Poikilohydry and homoihydry: antithesis or spectrum of possibilities?

Abstract: Summary Plants have followed two principal (and contrasting) strategies of adaptation to the irregular supply of water on land, which are closely bound up with scale. Vascular plants evolved internal transport from the soil to the leafy canopy (but their ‘homoihydry’ is far from absolute, and some are desiccation tolerant (DT)). Bryophytes depended on desiccation tolerance, suspending metabolism when water was not available; their cells are generally either fully turgid or desiccated. Desiccation tolerance requires preservation intact through drying–re-wetting cycles of essential cell components and their functional relationships, and controlled cessation and restarting of metabolism. In many bryophytes and some vascular plants tolerance is essentially constitutive. In other vascular plants (particularly poikilochlorophyllous species) and some bryophytes tolerance is induced by water stress. Desiccation tolerance is adaptively optimal on hard substrates impenetrable to roots, and on poor dry soils in seasonally dry climates. DT vascular plants are commonest in warm semiarid climates; DT mosses and lichens occur from tropical to polar regions. DT plants vary widely in their inertia to changing water content. Some mosses and lichens dry out and recover within an hour or less; vascular species typically respond on a time scale of one to a few days.

The spatial distribution of star formation in the solar neighbourhood: do all stars form in dense clusters?

Abstract: We present a global study of low mass, young stellar object (YSO) surface densities (�) in nearby (< 500 pc) star forming regions based on a comprehensive collection of Spitzer Space Telescope surveys. We show that the distribution of YSO surface densities in the solar neighbourhood is a smooth distribution, being adequately described by a lognormal function from a few to 10 3 YSOs per pc 2 , with a peak at � 22 stars pc

Mimicking the colourful wing scale structure of the Papilio blumei butterfly

Abstract: The brightest and most vivid colours in nature arise from the interaction of light with surfaces that exhibit periodic structure on the micro- and nanoscale. In the wings of butterflies, for example, a combination of multilayer interference, optical gratings, photonic crystals and other optical structures gives rise to complex colour mixing. Although the physics of structural colours is well understood, it remains a challenge to create artificial replicas of natural photonic structures. Here we use a combination of layer deposition techniques, including colloidal self-assembly, sputtering and atomic layer deposition, to fabricate photonic structures that mimic the colour mixing effect found on the wings of the Indonesian butterfly Papilio blumei. We also show that a conceptual variation to the natural structure leads to enhanced optical properties. Our approach offers improved efficiency, versatility and scalability compared with previous approaches.