Forecasting Algorithm

General seed behavior rule:  The behavior of an individual weedy Setaria seed in the soil is regulated by the amount of oxygen dissolved in water (the oxygen-water signal) that accumulates in the seed symplast, and temperatures favorable (or not) to germination growth (the germination temperature signal), over some time period (cumulatively oxy-hydro-thermal time).

General prediction algorithm:  An individual weedy foxtail seed will change state when the minimum inherently-required oxy-hydro-thermal time signal is received from its realized environment (plus signals not causing an effect due to inefficient transduction or insensitivity).

Three components (maps) of forecasting weedy foxtail behavior.  In essence, seed dormancy states respond to weather resulting in behavior:

Seed dormancy maps.  The first determinate of foxtail seed behavior is the dormancy state induced in individual seeds at abscission, at the time of dispersal from the parent plant.  See Dekker, Atchison and Jovaag, 2003; Dekker, 2003a, 2003b; for conceptual and experimental details.  See more general information on foxtail dormancy mechanisms and seed pool formation at the web site:  http://www.agron.iastate.edu/~weeds/Fox/foxSeedbehavior.html.

Environmental signal maps.  The inherent dormancy state of an individual foxtail seed interacts with the environmental signals it receives from the soil to determine its behavior.  Forecasting relies on 2 signals derived from monitoring soil temperature and moisture hourly:  the oxygen-water signal (OxSIG) and the germination temperature signal (TSIG), cumulatively oxy-hydro-thermal time.  See Dekker, Atchison and Jovaag, 2003; Dekker, 2003a, 2003b; for conceptual and experimental details.

Seedling emergence timing maps.  Foxtail seedlings emerge from the soil when sufficient environmental signals accumulate.  Foxtail seedling emergence timing exhibits predictable patterns of periodicity.  See Forcella et al., 1992, 1997 from NC-202 research; Dekker, Atchison and Jovaag, 2003. 

Forecasting behavior.  Several different types of forecasts can be made simultaneously, from very early coarse-grained predictions based only on dormancy maps and historical weather maps, to robust fine-grained forecasts based on all three maps.  Accurate seed behavior forecasting relies on all 3 maps: dormancy states, signals, patterns of seedling emergence.  Less accurate forecasts of seed behavior can be made with only one or two of these maps.  Organization of data from all maps that can be acquired will allow more robust regional forecasting.  Conducting regional protocols in conjunction with historical maps will allow ever more accurate forecasting. 

For a complete background and explanation to this forecasting approach read:

Dekker, J., B. Atchison, and K. Jovaag. 2003. Setaria spp. seed pool formation and initial assembly in agro-communities. Aspects of Applied Biology 69:247-259.  [.pdf 7.30.03]


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