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371.
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
372.
In large trees, the daily onset of transpiration causes water to be withdrawn from internal storage compartments, resulting in lags between changes in transpiration and sap flow at the base of the tree.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
373.
374.
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
375.
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
376.
377.
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
378.
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
Key message
Soil texture and temperature-related variables were the variables that most contributed to Nothofagus antarctica forest height in southern Patagonia. This information may be useful for improving forest management, for instance related to the establishment of silvopastoral systems or selection of suitable sites for forest reforestation in southern Patagonia.Context
Changes in forest productivity result from a combination of climate, topography, and soil properties.Aims
The relative importance of edaphic and climatic variables as drivers of productivity in Nothofagus antarctica forests of southern Patagonia, Argentina, was evaluated.Methods
A total of 48 mature stands of N. antarctica were selected. For each study site, we measured the height of three mature dominant trees, as an indicator of productivity. Seven soil, five spatial, and 19 climatic features were determined and related to forest productivity. Through partial least squares regression analyses, we obtained a model that was an effective predictor of height of mature dominant trees in the regional data set presented here.Results
The four variables that most contributed to the predictive power of the model were altitude, temperature annual range, soil texture, and temperature seasonality.Conclusion
The information gathered in this study suggested that the incidence of the soil and temperature-related variables on the height of dominant trees, at the regionally evaluated scale, was higher than the effect of water-related variables.379.
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