Showing papers in "Agricultural and Forest Meteorology in 1996"

TL;DR: A scheme for the characterization of the quality of direct turbulence measurements using the Navier-Stokes equations, which are the basis of direct surface-based measurements of turbulent fluxes via the eddy correlation method.

TL;DR: In this article, the feasibility of detecting the seasonal variation in leaf area index (LAI) in boreal conifer forests is investigated using optical instruments, and the results showed that most of the seasonal information is contained in the needle-to-shoot area ratio, which can not be measured indirectly using in situ optical instruments and has to be obtained from a large quantity of shoot sample analysis.

TL;DR: Sap flow was measured on several species from the tropical rain forest in French Guiana during two successive years over the dry season as discussed by the authors, and the results showed that sap flow densities exhibited high variations from one species to another.

TL;DR: In this paper, a mechanistically based C 3 leaf photosynthesis model combined with an empirical stomatal model and a canopy model of light interception and microclimate was used to simulate Quercus ilex canopy net photosynthesis and transpiration at l'Avic watershed (NE Spain).

TL;DR: In this article, a series of LANDSAT greenness vegetation index (Gi) images, calibrated to a common reference image, were used to model the foliar phenological dynamics of 30 quaking aspen (Populus tremuloides) and 29 black spruce (Picea mariana) stands in the boreal forest of Northeast Minnesota.

TL;DR: In this paper, the authors used a set of site-specific parameters, including on-site observations to specify more realistic soil and vegetation characteristics, and optimized minimum surface resistance and plant wilting parameters, resulted in a substantial improvement in model performance.

TL;DR: In this article, a new dynamic model for the interception of rainfall in a beech forest (WiMo) which considers the influence of wind upon canopy storage capacity was presented, and the canopy interception capacity was calculated by an optimization technique from a 17-month data set from a 97-year-old beech forests (Asperulo-Fagetum) in Northern Germany.

TL;DR: In this paper, the authors used remotely-sensed measurements of surface reflectance and temperature to allow application of the Penman-Monteith theory to partially-vegetated fields without a prior knowledge of the percent vegetation cover and canopy resistance.

TL;DR: In this article, the adaptability of North American agriculture to climate change is assessed through a review of current literature, which suggests several agronomic and economic adaptation strategies that are available to agriculture.

TL;DR: In this paper, a Ricardian method is used to compare actual farmer behavior across different climates to capture how climate effects both the per acre value of farms and how much land is farmed and these empirical relationships are used to predict the agricultural impacts of simple climate warming scenarios.

TL;DR: In this paper, the variations of the ratio of photosynthetically-active radiation to broadband solar radiation with sky conditions are described by means of variables that could be accessible in common radiometric networks.

TL;DR: In this article, the LAI-2000 plant canopy analyzer tends to underestimate the leaf area index (LAI) of coniferous stands because of the clumped (nonrandom) arrangement of needle area in the crown.

TL;DR: In this paper, a single Scots pine (Pinus sylvestris L.) was subjected to elevated temperature (year-round elevation), elevated CO2 (elevation from April 15 to September 15) and a combination of elevated temperature and CO2 for three years in open-topped chambers.

TL;DR: A model test reveals that the current approach to use a model for assimilation rate, An, to calculate stomatal conductance, gs, reasonably well, and is able to simulate the photosynthetic rate and stomatic conductance of grapevines reasonably well.

TL;DR: In this article, the effect of the extreme and highly variable environment, represented by the saturation deficit, D, and integrated water content of the upper soil layers, Φ, was discussed.

TL;DR: Thermal soil properties were clearly related to θ (and thus rainfall) throughout the measurement campaigns: hardly any changes occurred during the EFEDA-I experiment where continuous dry conditions prevailed, whereas for HAPEX-Sahel a clear decrease in all thermal properties was observed after the last rainfall.

TL;DR: In this article, the physical mechanisms involved in natural ventilation of a greenhouse equipped with continuous lateral windows were investigated using the following experimental procedures: • • air exchange rate measurements, using tracer gas or heat and water balance techniques; • direct determination of the air and heat flows through an opening, using an eddy correlation system, comprising a sonic anemometer and a fine wire thermocouple; measurements of mean and turbulent pressure differences at ground level between inside and outside.

TL;DR: In this article, the authors investigate the importance of such a pattern in determining future wheat (Triticum aestivum ) yields in the Central United States by using a dynamic crop growth model, CERES-Wheat, modified to include physiological effects of temperature and CO 2 on canopy photosynthesis.

TL;DR: The diurnal course of photosynthesis and transpiration of different plants can exhibit a dissymmetric behaviour between the morning and the afternoon, a photosynthetic midday depression and a transpiration ‘plateau' as discussed by the authors.

TL;DR: Seasonal variations of the CO2-exchange rate between treatments were evident, and they can be largely attributed to changes in the apparent quantum yield, the light-saturated rate of assimilation, leaf area index, and the ability to adapt to environmental stress conditions.

TL;DR: In this article, the Bowen ratio method was used to measure the vineyard energy balance including total latent heat flux (λE) from the canopy (λEc) was determined from sap flow measurements of transpiration.

TL;DR: In this paper, the authors studied the impact of climate changes on arable crop production in Scotland using simulation models for three crops of contrasting developmental type: faba or field bean, potato, spring and winter wheat.

TL;DR: In this article, tethered balloons were used to obtain vertical profiles of temperature, humidity, wind speed and direction from the surface to heights of 50 m at the leading and downwind edges of the field.

TL;DR: In this paper, the effect of temperature and moisture on CO2 and CH4 emissions from two peat sites in Scotland were monitored and related to temperature and humidity, and it was found that only 23% of the variation in CH4 flux could be explained by temperature with a Q10 of 2.8.

TL;DR: In this paper, a catalogue of hemispherical photographs was collected from conifer forest plantations in order to assess light obstruction by tree crowns, and a tree reconstruction technique called the vectorization method provided the means by which to reproduce fine 3-dimensional spatial distributions of the foliage and support structures of forest trees.

TL;DR: In this paper, the sky radiance distribution of the photosynthetically active radiation (PAR) was modeled using physically-based, non-linear equations, where the scattering angle (ψ) and the zenith position in the sky (Θ) were used.

TL;DR: In this paper, the relative influences of soil properties and meteorological conditions on the soil energy balance were determined in three fields during sugar beet establishment (April-May) in Northern France in 1991.

TL;DR: In this paper, the authors conducted an extensive energy and microclimatic assessment of different greenhouse covering materials, including single glass and three types of double polyethylene (PE) claddings.

TL;DR: A 40-layer canopy model is compiled to investigate the micrometeorological aspects of rainfall interception over an evergreen broad-leaved forest and shows that the evaporative efficiency is not only a function of water storage as described by the Rutter model, but also depends on the canopy structure and meteorological conditions.