Leaf economics fundamentals explained by optimality principles

The life span of leaves increases with their mass per unit area (LMA). It is unclear why. Here, we show that this empirical generalization (the foundation of the worldwide leaf economics spectrum) is a consequence of natural selection, maximizing average net carbon gain over the leaf life cycle. Analyzing two large leaf trait datasets, we show that evergreen and deciduous species with diverse construction costs (assumed proportional to LMA) are selected by light, temperature, and growing-season length in different, but predictable, ways. We quantitatively explain the observed divergent latitudinal trends in evergreen and deciduous LMA and show how local distributions of LMA arise by selection under different environmental conditions acting on the species pool. These results illustrate how optimality principles can underpin a new theory for plant geography and terrestrial carbon dynamics

Optical properties and charge-transfer excitations in edge-functionalized all-graphene nanojunctions

We investigate the optical properties of edge-functionalized graphene nanosystems, focusing on the formation of junctions and charge transfer excitons. We consider a class of graphene structures which combine the main electronic features of graphene with the wide tunability of large polycyclic aromatic hydrocarbons. By investigating prototypical ribbon-like systems, we show that, upon convenient choice of functional groups, low energy excitations with remarkable charge transfer character and large oscillator strength are obtained. These properties can be further modulated through an appropriate width variation, thus spanning a wide range in the low-energy region of the UV-Vis spectra. Our results are relevant in view of designing all-graphene optoelectronic nanodevices, which take advantage of the versatility of molecular functionalization, together with the stability and the electronic properties of graphene nanostructures.Comment: J. Phys. Chem. Lett. (2011), in pres

Induction of leaf senescence in Arabidopsis thaliana by long days through a light-dosage effect

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74662/1/j.1399-3054.1996.tb00463.x.pd

Simulating the carbon balance of a temperate larch forest under various meteorological conditions

<p>Abstract</p> <p>Background</p> <p>Changes in the timing of phenological events may cause the annual carbon budget of deciduous forests to change. Therefore, one should take such events into account when evaluating the effects of global warming on deciduous forests. In this article, we report on the results of numerical experiments done with a model that includes a phenological module simulating the timing of bud burst and other phenological events and estimating maximum leaf area index.</p> <p>Results</p> <p>This study suggests that the negative effects of warming on tree productivity (net primary production) outweigh the positive effects of a prolonged growing season. An increase in air temperature by 3°C (5°C) reduces cumulative net primary production by 21.3% (34.2%). Similarly, cumulative net ecosystem production (the difference between cumulative net primary production and heterotrophic respiration) decreases by 43.5% (64.5%) when temperatures are increased by 3°C (5°C). However, the positive effects of CO₂enrichment (2 × CO₂) outweigh the negative effects of warming (<5°C).</p> <p>Conclusion</p> <p>Although the model was calibrated and validated for a specific forest ecosystem, the implications of the study may be extrapolated to deciduous forests in cool-temperate zones. These forests share common features, and it can be conjectured that carbon stocks would increase in such forests in the face of doubled CO₂and increased temperatures as long as the increase in temperature does not exceed 5°C.</p

Optimal stomatal behaviour around the world

This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this recordStomatal conductance (g s) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of g s in predictions of global water and carbon cycle changes, a global-scale database and an associated globally applicable model of g s that allow predictions of stomatal behaviour are lacking. Here, we present a database of globally distributed g s obtained in the field for a wide range of plant functional types (PFTs) and biomes. We find that stomatal behaviour differs among PFTs according to their marginal carbon cost of water use, as predicted by the theory underpinning the optimal stomatal model and the leaf and wood economics spectrum. We also demonstrate a global relationship with climate. These findings provide a robust theoretical framework for understanding and predicting the behaviour of g s across biomes and across PFTs that can be applied to regional, continental and global-scale modelling of ecosystem productivity, energy balance and ecohydrological processes in a future changing climate.This research was supported by the Australian Research Council (ARC MIA Discovery Project 1433500-2012-14). A.R. was financially supported in part by The Next-Generation Ecosystem Experiments (NGEE-Arctic) project, which is supported by the Office of Biological and Environmental Research in the Department of Energy, Office of Science, and through the United States Department of Energy contract No. DE-AC02-98CH10886 to Brookhaven National Laboratory. M.O.d.B. acknowledges that the Brassica data were obtained within a research project financed by the Belgian Science Policy (OFFQ, contract number SD/AF/02) and coordinated by K. Vandermeiren at the Open-Top Chamber research facilities of CODA-CERVA (Tervuren, Belgium)

Optimal stomatal behaviour around the world

© 2015 Macmillan Publishers Limited. All rights reserved. Stomatal conductance (g s) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of g s in predictions of global water and carbon cycle changes, a global-scale database and an associated globally applicable model of g s that allow predictions of stomatal behaviour are lacking. Here, we present a database of globally distributed g s obtained in the field for a wide range of plant functional types (PFTs) and biomes. We find that stomatal behaviour differs among PFTs according to their marginal carbon cost of water use, as predicted by the theory underpinning the optimal stomatal model and the leaf and wood economics spectrum. We also demonstrate a global relationship with climate. These findings provide a robust theoretical framework for understanding and predicting the behaviour of g s across biomes and across PFTs that can be applied to regional, continental and global-scale modelling of ecosystem productivity, energy balance and ecohydrological processes in a future changing climate

Relationship between home care service use and changes in the care needs level of Japanese elderly

<p>Abstract</p> <p>Background</p> <p>With the introduction of long-term care insurance (LTCI) in Japan, more home care services are available for the community-dwelling elderly. To deliver effective home care services, it is important to know the effects of service use. In this study, as the first step to determine this, we sought to describe different home service use in the sustained/improved group and deteriorated group in their care needs levels, and to report the relationship between the use of home care services and changes in care needs levels.</p> <p>Methods</p> <p>The participants included 624 of a total of 1,474 users of LTCI services in one city in Japan. Home care service users were stratified into a 'lower care needs level subgroup' and a 'higher care needs level subgroup' based on the baseline care needs level. Simple statistical comparison and multiple logistic regression analyses in which the change in care needs level was set as a dependent variable were performed. Gender, age, and baseline care needs level were designated as control variables. Home based services were treated as independent variables. In this study, home care services consisted of home help, home bathing services, a visiting nurse, home rehabilitation, nursing home daycare, health daycare, loan of medical devices, respite stay in a nursing home, respite stay in a health care facility, respite stay in a sanatorium-type medical care facility, and medical management by a physician.</p> <p>Results</p> <p>In the lower care needs level subgroup, age (OR = 1.04, CI, 1.01-1.08), use of respite stay in a nursing home (OR = 2.55; CI, 1.43-4.56), and the number of types of long-term care services (OR = 1.33; CI, 1.02-1.74) used during an 11 month period were significantly related to a deterioration of the user's care needs level. In the higher care needs level subgroup, use of medical management by a physician (OR = 6.99; CI, 1.42-41.25) was significantly related to a deterioration of the user's care needs level. There were no home based services significantly related to sustaining or improving the user's care needs level.</p> <p>Conclusion</p> <p>There were different home service use in two groups (the sustained/improved group and the deteriorated group). Respite stay in a nursing home service use and more types of service use were related to experiencing a deterioration of care needs level in lower care needs level community-dwelling elderly persons in Japan. Further, medical management by a physician service was related to experiencing a deterioration of care needs level in higher care needs level community-dwelling elderly persons.</p

Mixed-species plantations of eucalyptus with nitrogen fixing trees: a review

Mixed-species plantations of Eucalyptus with a nitrogen (N2) fixing species have the potential to increase productivity while maintaining soil fertility, compared to Eucalyptus monocultures. However, it is difficult to predict combinations of species and sites that will lead to these benefits. We review the processes and interactions occurring in mixed plantations, 5 and the influence of species or site attributes, to aid the selection of successful combinations of species and sites. Successful mixtures, where productivity is increased over that of monocultures, have often developed stratified canopies, such that the less shade-tolerant species overtops the more shadetolerant species. Successful mixtures also have significantly higher rates of N and P cycling than 10 Eucalyptus monocultures. It is therefore important to select N2-fixing species with readily decomposable litter and high rates of nutrient cycling, as well as high rates of N2-fixation. While the dynamics of N2-fixation in tree stands are not well understood, it appears as though eucalypts can benefit from fixed N as early as the first or second year following plantation establishment. A meta-analysis of 18 published studies revealed several trials in which mixtures were significantly 15 (