© 1986 Heron Publishing—Victoria, Canada
Simulation model of a laboratory-grown phreatophytic woody legume
D. Bachelet (1), W. M. Jarrell (2) and R. A. Virginia (3)
1. Department of Biology, New Mexico State University, Las Cruces, NM 80523, USA / 2. Dry Lands Research Institute, and Soil and Environmental Sciences, University of California, Riverside, CA 92521, USA / 3. Biology Department and Systems Ecology Research Group, San Diego State University, San Diego, CA 92182, USA /
Summary
A mechanistic model was developed to simulate growth of mesquite Prosopis glandulosa Torr. trees under a phreatic (groundwater) moisture regime. Experimental data obtained in a greenhouse reproducing the phreatic
environment (2 m soil columns with 10 cm of water-saturated soil at the bottom) were used to parameterize three submodels
predicting carbon (C), nitrogen (N) and water dynamics in leaves, branches, roots and root nodules. In the column simulation
model (COLSIM), photosynthesis was driven by air temperature and soil salinity. Water availability was nonlimiting. Nitrogen
was absorbed by the roots from inorganic soil N and also fixed by root nodules. Comparison of the simulation with results
from the greenhouse experiment showed that the model accurately reproduced shoot biomass and nitrogen content dynamics up
to three years with or without a high soil salinity content. Root biomass was underestimated when soil salinity was high because
the model did not account for the increased allocation of C to roots under conditions of high salinity. Observed annual cycles
of water uptake during the three-year run were not reproduced because the model did not include a phenological function which
apparently drives these cycles.
