Canopy characterization is a key factor to improve pesticide application methods in tree crops and vineyards. Development of quick, easy and efficient methods to determine the fundamental parameters used to characterize canopy structure is thus an important need. In this research the use of ultrasonic and LIDAR sensors have been compared with the traditional manual and destructive canopy measur...

Results from two nested-grid large-eddy simulations comparing cases with and without a plant canopy are presented. Through comparisons of numerically generated mean and turbulence statistics, the in uence of a plant canopy with a leaf area index of two is shown to modify the air  ow compared with an identical case without plants. Investigations of instantaneous Ž elds and spatial spectra show...

During the last century, the density of Ashe juniper (Juniperus ashei Buchholz) has greatly increased in oak savannahs of central Texas. Recently, juniper removal has been advocated as a regional water conservation tool. In this study, we investigated whether juvenile trees released from an overstory canopy after clearing exhibited accelerated growth and water consumption. We compared leaf-leve...

Accurate estimates of forest canopy are essential for the characterization of forest ecosystems. Remotelysensed techniques provide a unique way to obtain estimates over spatially extensive areas, but their application is limited by the spectral and temporal resolution available from these systems, which is often not suited to meet regional or local objectives. The use of unmanned aerial vehicle...

Leaf-level morphological and physiological responses of mature, winter-deciduous, shade-tolerant Acer saccharum Marsh. trees to gap formation caused by selection harvest were studied experimentally over a 2-year period. We found no evidence for either physiological stress or positive acclimation following gap creation during the 1-2-week post-harvest period. Rather, lower-canopy leaves showed g...

Physical and functional properties of foliage were measured at a variety of microsites in a broad-leaved Nothofagus fusca (Hook. f.) Ørst. canopy. The light climate of the foliage at these sites was monitored for 39 days in the late spring and early summer with in situ sensors. Foliage nitrogen content (N), mean leaf angle, and gas exchange characteristics were all correlated with the amount of...

In June 1993, net photosynthetic rates, stomatal conductance and isoprene emission rates of sweetgum leaves (Liquidambar styraciflua L.) were measured at the top of the forest canopy (sun leaves) and within the canopy at a height of 8-10 m above ground level (shade leaves). Large differences in net photosynthetic rates and stomatal conductance were found between sun and shade leaves. Mean rates...

The adjustment of pesticide dose rates according to canopy size and leaf area density is not encouraged by current label formulations. However, experimental evidence shows that the application of a constant dose per unit ground area consistently results in average foliar deposits that are inversely proportional to the leaf area index (LAI) of the crop. Several methods for dose rate adjustment h...

Heavy atmospheric nitrogen (N) deposition has been associated with altered nutrient cycling, and even N saturation, in forest ecosystems previously thought to be N-limited. This observation has prompted application to such forests of non-N mineral nutrients as a mitigation measure. We examined leaf gas-exchange, leaf chemistry and leaf and shoot morphological responses of Acer saccharum Marsh. ...