Due to past limitations in experimental technology, canopy function has generally been inferred from leaf properties through scaling and/or indirect measurements. The development of a facility (EcoCELLs) at the Desert Research Institute has now made it possible to directly measure canopy gas exchange. In this experiment, sunflowers (Helianthus annus) were planted in the EcoCELLs and grown under...

Spatially distributed information on canopy parameters is an important input to precision agriculture. Remote sensing data, and especially high-resolution hyperspectral data of sensors such as the multi-directional satellite-sensor CHRIS or the airborne spectrometer AVIS provide such information. In order to derive the canopy parameters leaf area index and fraction of mature material as well as...

T h e potentials and limits of estimating canopy parameters are investigated using only a reflectance spectrum in the optical domain, and the PROSPECT + SAIL model. Simulations are performed on A VIRIS (Airborne Visible~Infrared Imaging Spectrometer) equivalent spectra, corrected for the atmospheric effects. It is established that this model is numerically invertible. The sensitivity analysis o...

Leaf respiration is an important component of carbon exchange in terrestrial ecosystems, and estimates of leaf respiration directly affect the accuracy of ecosystem carbon budgets. Leaf respiration is inhibited by light; therefore, gross primary production (GPP) will be overestimated if the reduction in leaf respiration by light is ignored. However, few studies have quantified GPP overestimatio...

The relationship between leaf area and diameter at breast height (d.b.h.) or sapwood area (AS) has been used to estimate stand leaf area or biomass of forest canopies. It has been suggested that intra-specifi c variations in the relationship between stand leaf area and d.b.h. or AS can introduce a systematic error in these estimates for younger and older stands unless additional parameters rela...

I evaluated the use of global remote sensing techniques for estimating plant leaf chlorophyll a + b (C(ab); μg cm(-2)) and water (C(w); mg cm(-2)) concentrations as well as the ratio of C(w)/C(ab) with the PROSAIL model under possible distributions for leaf and soil spectra, leaf area index (LAI), canopy geometric structure, and leaf size. First, I estimated LAI from the normalized difference v...

Leaf gas exchange, water potential, and specific leaf area of two tropical semi-deciduous tree species, Brosimum lactescens S. Moore and Tovomita schomburgkii Planch & Triana, were quantified to establish how these properties were affected by seasonal variations in rainfall and leaf canopy position. The study was conducted at a site near Sinop Mato Grosso, Brazil, which is located within the ec...

A Soil-Plant Analysis Development (SPAD) chlorophyll meter can be used as a simple tool for evaluating N concentration of the leaf and investigating the combined effects of nitrogen rate and leaf age on N distribution. We conducted experiments in a paddy field over two consecutive years (2008-2009) using rice plants treated with six different N application levels. N distribution pattern was det...

Canopy photosynthesis models have predicted an optimal leaf area index (LAI; leaf area per unit surface area) and leaf nitrogen distribution at which whole-plant carbon gain per unit N is maximized. In this study we experimentally tested these models, using transgenic P(SAG12)-IPT tobacco (SAG; Nicotiana tabacum L.) plants with delayed leaf senescence and therefore a greater LAI and more unifor...

Mature potato (Solanum tuberosum L. cv. Kennebec) canopies are composed of leaves originating frommainand axillary-stem branches. Canopy leaf distribution and its corresponding contribution to wholecanopy photosynthetic rates have not been quantified. An experiment using SPAR (Soil–Plant–Atmosphere–Research) chambers maintained at 16-h day/night thermoperiods of 14/10, 17/12, 20/15, 23/18, 28/2...