The Faustmann model as a model for a forestry of prices     

Peter Deegen  Martin Hostettler  Guillermo A. Navarro 《European Journal of Forest Research》2011,130(3):353-368

The relation between the Faustmann model and “a forestry of prices” as a concept of thought was examined. At first, the meaning of the Faustmann model in economic sciences is the explanation of allocation and distribution by prices. The rotation age determination plays a secondary role only. Secondly, “a forestry of prices” as an application of the “free to choose” way of thinking is explained. The concept allows us to understand how individuals of anonymous groups achieve forest sustainability and provide forest environmental goods. Thirdly, the relation between the Faustmann model and “a forestry of prices” is discussed. For this purpose, the Faustmann model is described as a scientific laboratory. It helps us to observe how equilibrium arises as a non-intended result of individual welfare maximization in anonymous interactions. And conversely with the help of “a forestry of prices”, we understand also that the individual maximization approach of the Faustmann model re-enacts the unintended interaction situations in anonymous group. With help of the Faustmann model, we can understand deep aspects of “a forestry of prices”. Vice versa, “a forestry of prices” shows the meaning of the formal solutions of the Faustmann model.  相似文献   

Dynamics of transpiration, sap flow and use of stored water in tropical forest canopy trees     

Meinzer FC  James SA  Goldstein G 《Tree physiology》2004,24(8):901-909

In large trees, the daily onset of transpiration causes water to be withdrawn from internal storage compartments, resulting in lags between changes in transpiration and sap flow at the base of the tree. We measured time courses of sap flow, hydraulic resistance, plant water potential and stomatal resistance in co-occurring tropical forest canopy trees with trunk diameters ranging from 0.34-0.98 m, to determine how total daily water use and daily reliance on stored water scaled with size. We also examined the effects of scale and tree hydraulic properties on apparent time constants for changes in transpiration and water flow in response to fluctuating environmental variables. Time constants for water movement were estimated from whole-tree hydraulic resistance (R) and capacitance (C) using an electric circuit analogy, and from rates of change in water movement through intact trees. Total daily water use and reliance on stored water were strongly correlated with trunk diameter, independent of species. Although total daily withdrawal of water from internal storage increased with tree size, its relative contribution to the daily water budget (approximately 10%) remained constant. Net withdrawal of water from storage ceased when upper branch water potential corresponded to the sapwood water potential (Psi(sw)) at which further withdrawal of water from sapwood would have caused Psi(sw) to decline precipitously. Stomatal coordination of vapor and liquid phase resistances played a key role in limiting stored water use to a nearly constant fraction of total daily water use. Time constants for changes in transpiration, estimated as the product of whole- tree R and C, were similar among individuals (~0.53 h), indicating that R and C co-varied with tree size in an inverse manner. Similarly, time constants estimated from rates of change in crown and basal sap flux were nearly identical among individuals and therefore independent of tree size and species.  相似文献   

Public health. Increasing international gaps in health-related publications     

Paraje G  Sadana R  Karam G 《Science (New York, N.Y.)》2005,308(5724):959-960

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Kepler-16: a transiting circumbinary planet     

Doyle LR  Carter JA  Fabrycky DC  Slawson RW  Howell SB  Winn JN  Orosz JA  Prša A  Welsh WF  Quinn SN  Latham D  Torres G  Buchhave LA  Marcy GW  Fortney JJ  Shporer A  Ford EB  Lissauer JJ  Ragozzine D  Rucker M  Batalha N  Jenkins JM  Borucki WJ  Koch D  Middour CK  Hall JR  McCauliff S  Fanelli MN  Quintana EV  Holman MJ  Caldwell DA  Still M  Stefanik RP  Brown WR  Esquerdo GA  Tang S  Furesz G  Geary JC  Berlind P  Calkins ML  Short DR  Steffen JH  Sasselov D  Dunham EW  Cochran WD  Boss A  Haas MR  Buzasi D  Fischer D 《Science (New York, N.Y.)》2011,333(6049):1602-1606

We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20 and 69% as massive as the Sun and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5° of a single plane, suggesting that the planet formed within a circumbinary disk.  相似文献   

Evaluation of some quality characteristics in cassava storage roots     

Christopher Wheatley  Guillermo Gómez 《Plant foods for human nutrition (Dordrecht, Netherlands)》1985,35(2):121-129

The susceptibility to physiological deterioration and the hardness (penetration) of fresh peeled cassava roots as well as the cooking time, taste and texture of cooked roots of four (one local and three promising) cultivars at four plant ages (6, 8, 10 and 12 months) were evaluated. Variety or cultivar, plant age and their interactions significantly affected all these parameters. Roots produced by the local cultivar (M Col 113) had lower DM contents and susceptibility to physiological deterioration, a longer cooking time and higher penetration measurements than the promising cultivars. Physiological deterioration and penetration values tended to decrease, whereas cooking time increased as the plants became older. The variation in correlation coefficients between quality and chemical parameters among the different cultivars was substantial, with no correlation being significant in all four cultivars. The experimental results demonstrate the great variability among cassava cultivars in the root quality factors.  相似文献   

Abarenicola pusilla (Quatrefages, 1866): A novel species for fish waste bioremediation from marine recirculating aquaculture systems          下载免费PDF全文

Silvia Gómez  Carlos Felipe Hurtado  Jaime Orellana  Guillermo Valenzuela‐Olea  Alice Turner 《Aquaculture Research》2018,49(3):1363-1367

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Effect of castration at 10 months of age on growth physiology and behavior of male feral beef cattle          下载免费PDF全文

Javier Álvarez‐Rodríguez  Pere Albertí  Guillermo Ripoll  Isabel Blasco  Albina Sanz 《Animal Science Journal》2017,88(7):991-998

This study compared the growth performance, plasma testosterone and cortisol levels around castration at 10 months of age, and plasma insulin‐like growth factor (IGF)‐I concentration and flight speed, in intact bulls and steers from 10 to 21 months of age in a feral Spanish breed. Fourteen bulls (366.5 ± 48.5 kg live weight) were assigned at random to one of two treatments: surgically castrated (steers) or intact (bulls), and submitted to an identical fattening period. Steers reared until heavy live weights (21 months of age) grew slowly and had lower plasma IGF‐I concentrations than intact bulls. These differences were mainly highlighted the month after surgery (11 months of age) and the last part of the fattening period (from 19 to 21 months of age). After surgical castration (11 and 12 months of age), steers showed a tendency to display greater flight speed values than intact bulls but baseline plasma cortisol concentration did not differ between groups at this time. At the end, steers and bulls reached nearly similar temperament, as flight speed did not differ between them. The results confirm the role of IGF‐I as a key anabolic hormone in male beef cattle and thus it may reflect growth differences due to altered sex steroids production.  相似文献   

The relative importance of soil properties and regional climate as drivers of productivity in southern Patagonia’s <Emphasis Type="Italic">Nothofagus antarctica</Emphasis> forests     

Héctor A. Bahamonde  Guillermo Martínez Pastur  María V. Lencinas  Rosina Soler  Yamina M. Rosas  Brenton Ladd  Sandra Duarte Guardia  Pablo L. Peri 《Annals of Forest Science》2018,75(2):45

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Tree Quality in Agroforestry Systems Managed by Small-Scale Mayan Farmers in Chiapas,Mexico     

Lorena Soto Pinto  Manuel Anzueto Martínez  Pablo Martínez Zurimendi  Guillermo Jiménez-Ferrer 《Small-Scale Forestry》2017,16(1):103-118

Increasingly, plantations for food, fiber and wood, are necessary to provide a growing world population. Agroforestry systems become more and more important, however these systems usually develop in marginal conditions, limited land, restricted funding, occasional technical support and above this, there is limited documentation and evaluation of innovated traditional systems in indigenous and small-scale contexts, which challenge forest scientists. The aim of this research was to assess the quality of trees in plots managed by Mayan indigenous farmers who planted agroforestry systems with fine wood species to increase the value of land and labor in localities with highly-marginal social conditions in Northern Chiapas, México. Twenty oldest plots were selected within a group of previously established plots (eight with improved fallow, six with shaded coffee and six with maize crop associated to trees) where forest inventories were carried out in nested 100 and 1000 m²-circular plots. In all plots tree diameter, height, quality indicators and the incidence of the pest Hypsipyla grandella were measured. Trees in the maize-associated-to-trees system are favored by the practices applied to annual crop during the first 3rd–5th years, a period in which they are free from the interference of other trees and benefit from favorable light conditions, weeding and a higher intensive care from the farmer while shaded coffee and improved fallow have higher tree densities and a more closed canopy condition than maize associated to trees. In consequence, maize associated to trees shows 68.1 % stems with good form; shaded coffee and improved fallow averaged 40.5 and 39.7 % of good quality stems, respectively; improved fallow exhibited a greater number of suppressed trees than shaded coffee and maize associated to trees (p < 0.0001). In addition, maize associated to trees showed the highest proportion of trees with commercial value with 56.9 %, followed by improved fallow with 28.2 %, and shaded coffee with 11.8 % (p < 0.0001); the rest were trees with domestic uses. However, maize associated to trees significantly result with high incidence of H. grandella probably due to the crown exposure. Timber volume averaged 92.9 ± 68.9 m³ for improved fallow, 77.3 ± 24.8 m³ for shaded coffee, and 52.5 ± 39.7 m³ for maize associated to trees. The value of the fine wood represents increment in income, variety of products and self-employment for households. Nonetheless, improved fallow and coffee plantations might benefit from the elimination of competitors from larger trees to favor promising immature ones and pruning, while maize crop associated to trees might benefit from opportune pruning for controlling the stem borer as well as tree replacement to achieve long term replacement and harvesting.  相似文献