Yield-SAFE: A parameter-sparse, process-based dynamic model for predictingresource capture, growth, and production in agroforestry systems.

摘要

1. Silvoarable agroforestry (SAF) is the cultivation of trees and arable cropson the same parcel of land. SAF may contribute to modern diversified land useobjectives in Europe, such as enhanced biodiversity and productivity, reducedleaching of nitrogen, protection against flooding and erosion, andattractiveness of the landscape. Long-term yield predictions are needed toassess long-term economic profitability of SAF. 2. A model for growth, resourcesharing and productivity in agroforestry systems was developed to act as a toolin forecasts of yield, economic optimization of farming enterprises andexploration of policy options for land use in Europe. The model is called Yield-SAFE; from “YIeld Estimator for Long term Design of Silvoarable AgroForestry inEurope”. The model was developed with as few equations and parameters aspossible to allow model parameterization under constrained availability of datafrom long-term experiments. 3. The model consists of seven state equationsexpressing the temporal dynamics of: (1) tree biomass; (2) tree leaf area; (3)number of shoots per tree; (4) crop biomass; (5) crop leaf area index; (6) heatsum; and (7) soil water content. The main outputs of the model are the growthdynamics and final yields of trees and crops. Daily inputs are temperature,radiation and precipitation. Planting densities, initial biomasses of tree andcrop species, and soil parameters must be specified. 4. A parameterization ofYield-SAFE is generated, using published yield tables for tree growth and outputfrom the comprehensive crop simulation model STICS. Analysis of tree and cropgrowth data from two poplar agroforestry stands in the United Kingdomdemonstrates the validity of the modelling concept and calibration philosophy ofYield-SAFE. A sensitivity analysis is presented to elucidate which biologicalparameters most influence short and long-term productivity and land equivalentratio. 5. The conceptual model, elaborated in Yield-SAFE, in combination withthe outlined procedure for model calibration, offers a valid tool forexploratory land use stud