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221.
BELINDA E. MEDLYN REMKO A. DUURSMA DEREK EAMUS DAVID S. ELLSWORTH I. COLIN PRENTICE CRAIG V. M. BARTON KRISTINE Y. CROUS PAOLO DE ANGELIS MICHAEL FREEMAN LISA WINGATE 《Global Change Biology》2011,17(6):2134-2144
Models of vegetation function are widely used to predict the effects of climate change on carbon, water and nutrient cycles of terrestrial ecosystems, and their feedbacks to climate. Stomatal conductance, the process that governs plant water use and carbon uptake, is fundamental to such models. In this paper, we reconcile two long‐standing theories of stomatal conductance. The empirical approach, which is most commonly used in vegetation models, is phenomenological, based on experimental observations of stomatal behaviour in response to environmental conditions. The optimal approach is based on the theoretical argument that stomata should act to minimize the amount of water used per unit carbon gained. We reconcile these two approaches by showing that the theory of optimal stomatal conductance can be used to derive a model of stomatal conductance that is closely analogous to the empirical models. Consequently, we obtain a unified stomatal model which has a similar form to existing empirical models, but which now provides a theoretical interpretation for model parameter values. The key model parameter, g1, is predicted to increase with growth temperature and with the marginal water cost of carbon gain. The new model is fitted to a range of datasets ranging from tropical to boreal trees. The parameter g1 is shown to vary with growth temperature, as predicted, and also with plant functional type. The model is shown to correctly capture responses of stomatal conductance to changing atmospheric CO2, and thus can be used to test for stomatal acclimation to elevated CO2. The reconciliation of the optimal and empirical approaches to modelling stomatal conductance is important for global change biology because it provides a simple theoretical framework for analyzing, and simulating, the coupling between carbon and water cycles under environmental change. 相似文献
222.
The simultaneous study of the temporal dynamics of foraging behaviour, diet and seed abundance is essential to assess the way in which resources affect the behaviour and ecology of harvester ants. Here, we evaluate how fluctuations in grass seed abundance during three consecutive growing seasons influenced the foraging behaviour and diet of the harvester ants Pogonomyrmex rastratus, P. mendozanus and P. inermis in the central Monte desert, Argentina. Seed abundance of the most consumed grasses varied greatly through ant activity season, and ants altered their foraging behaviour in response to those changes. Foragers spent more time travelling and searching for food, and their foraging trips took longer during the low seed availability season. Foraging distance was very similar among species and, contrary to our expectations, did not vary between seasons. Foraging success of P. rastratus and P. inermis increased during the high availability season. This matched the seasonal pattern of foraging activity, suggesting that colonies may detect seed abundance and regulate their foraging effort with the rate of forager success. Although grass seeds were the main item in the diet of the three species, P. mendozanus, and to a lesser extent P. rastratus, turned more generalist when grass seeds were scarce. In contrast, P. inermis showed a very narrow diet breadth, only harvesting grass seeds in both seasons. Our results indicate the relevance of seed availability on foraging behaviour of harvester ants, which should be taken into account when predicting and evaluating the effect of ants on seed resources as well as numerical responses of harvester ant populations to the temporal and spatial variations in grass seed abundance. 相似文献
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MARC DE HERT DAN COHEN JULIO BOBES MARCELO CETKOVICH‐BAKMAS STEFAN LEUCHT DAVID M. NDETEI JOHN W. NEWCOMER RICHARD UWAKWE ITSUO ASAI HANS‐JURGEN MÖLLER SHIV GAUTAM JOHAN DETRAUX CHRISTOPH U. CORRELL 《World psychiatry》2011,10(2):138-151
Physical disorders are, compared to the general population, more prevalent
in people with severe mental illness (SMI). Although this excess morbidity
and mortality is largely due to modifiable lifestyle risk factors, the screening
and assessment of physical health aspects remains poor, even in developed
countries. Moreover, specific patient, provider, treatment and system factors
act as barriers to the recognition and to the management of physical diseases
in people with SMI. Psychiatrists can play a pivotal role in the improvement
of the physical health of these patients by expanding their task from clinical
psychiatric care to the monitoring and treatment of crucial physical parameters.
At a system level, actions are not easy to realize, especially for developing
countries. However, at an individual level, even simple and very basic monitoring
and treatment actions, undertaken by the treating clinician, can already improve
the problem of suboptimal medical care in this population. Adhering to monitoring
and treatment guidelines will result in a substantial enhancement of physical
health outcomes. Furthermore, psychiatrists can help educate and motivate
people with SMI to address their suboptimal lifestyle, including smoking,
unhealthy diet and lack of exercise. The adoption of the recommendations presented
in this paper across health care systems throughout the world will contribute
to a significant improvement in the medical and related psychiatric health
outcomes of patients with SMI. 相似文献
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CAROLINE MÜLLER ALISON BARKER JEAN-LUC BOEVÉ PETER W. DE JONG HELENE DE VOS PAUL M. BRAKEFIELD 《Biological journal of the Linnean Society. Linnean Society of London》2004,83(2):219-227
This study compares the population genetic structure of two obligate parthenogenetic sawfly species, Aneugmenus padi (L.) Zhelochovtsev and Eurhadinoceraea ventralis (Panzer) Enslin (Hymenoptera: Tenthredinidae). Allozymes were used to detect genetic differences in larvae collected at different sites in six European countries. For A. padi , scoring six polymorphic enzymes revealed the existence of five dominant, widely distributed clones and several more with only very few individuals occurring locally. The clonal diversity and identity differed across collection sites, with up to at maximum eight clones coexisting at a single locality. In contrast, in E. ventralis , individuals from different localities were all monomorphic for at least six different enzymes and are therefore assumed to belong to the same clone. Differences in population genetic structure of these sawfly species can be related to the differing distributions of their host plants: the fern, Pteridium aquilinum , the host of A. padi , has been an invasive species for more than two hundred years. Spread of clones of A. padi is likely to have closely followed the complex invasive pattern of spread of the plant. Larvae of E. ventralis were collected from local, horticultural plantings of Clematis spp. of recent origin probably with gardeners having traded plants infested with the sawfly. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 219–227. 相似文献
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