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Title: Modeling cotton (Gossypium spp) leaves and canopy using computer aided geometric design (CAGD)

item ALARCON, VLADIMIR - Mississippi State University
item Sassenrath, Gretchen

Submitted to: Ecological Modelling
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2011
Publication Date: 4/22/2011
Citation: Alarcon, V.J., Sassenrath, G.F. 2011. Modeling cotton (Gossypium spp) leaves and canopy using computer aided geometric design (CAGD). Ecological Modelling. 222:1951-1963.

Interpretive Summary: Modeling crop canopies allows us to explore interactions between the environment and plant performance. The environment within the crop canopy depends on the environment external to the canopy, and the leaf and canopy structure. Changes in the canopy environment affect the crop plant performance because of differences in environmental conditions, such as temperature, sunlight, and gases that the plant uses in photosynthesis. The plant performance determines the net productivity of the crop, and the amount of material harvested. Insects that live within the crop canopy are also affected by the environment within the canopy, and different insects prefer different types of environments. Most of the current models of crop canopies have been developed based on an approximation of the leaf shape and canopy structure. While these models are useful in exploring light profiles within the canopy, they are limited in fully exploring interactions within the canopy microenvironment. In this study, we developed a model of cotton leaves that is geometrically accurate, and populated the leaves into a model of a cotton canopy element. The modeled canopy adequately simulates the profile of sunlight within the crop, as measured by the leaf area index, in comparison to actual crop canopies. The geometrically accurate model is more detailed and accurate, and hence will more accurately capture changes in canopy microenvironment with leaf shape and canopy structure. The model will be used to explore insect distribution within crops to developed improved management protocols.

Technical Abstract: The goal of this research is to develop a geometrically accurate model of cotton crop canopies for exploring changes in canopy microenvironment and physiological function with leaf structure. We develop an accurate representation of the leaves, including changes in three-dimensional folding and orientation with age and cultivar. Photogrammetrical analysis of leaf surfaces is used to generate control points. Interpolation of the control points is then performed with a tensor products interpolants model that generates a generic leaf shape. Dynamic changes in leaf shape and canopy position over the growing season are based on measurements of cotton canopies in the field, and are used to modulate the generic leaf shape. The simulated leaves populate a canopy element based on statistical distributions from measured crop canopies. The simulation is found to give a good representation of cotton canopies leaves, adequately capturing the three-dimensional structure of the leaves and changes over the growing season. The simulated canopy accurately estimates leaf area index, except for the earliest measurement period prior to canopy closure. The method of developing leaves, populating a crop canopy element, and visualizing the canopies is found to be a useful tool for studies of physiological function and biophysical dynamics within a crop canopy.