Study On Above-ground And Below-ground Functional-structural Uniform Model Of Alfalfa

Alfalfa is the world’s most widely planted forage grass. It is famous for the excellent quality, and it is capable of meliorated soil and conserving soil and water. It is of great significance to study the regulation of alfalfa’s development and growth and the interaction with the environment. This study is based on the functional-structural mutual feedback mechanism, to build an integrated functional-structural model of alfalfa above and below ground. The contents and results are as follows:1. Establishment of functional-structural model of alfalfa above and below ground with unified pattern:According to the branch characteristic, basic unit of growth is divided and alfalfa topologic structure model is built. The response of alfalfa’s assimilated organs when photosynthetic active radiation reaches canopy is described by negative exponential function. Daily average photosynthetic rate is calculated by gauss integral formula, combining geometric characteristics of assimilate organs to build photosynthetic production model. To distribute the biomass above and below ground taking the product of sink strength and expansion rate as weight on the basis of sink-source theory. Get the geometrical dimension through allometrical rules of plant.2. Parameter calibration and realization of the model:To study the relationship between alfalfa branch above the ground and the active accumulated temperature, applying this relationship to the root system, in order to parameterize the topological structure model. Parameterize the photosynthetic production model with field measurement and computer calculation. Analyzing the above and below ground biomass change with accumulate temperature to extract parameters of biomass allocation. To parameterize the spatial geometry by studying the relationship among leaf area, node volume, root length and dry matter weight. Simulate the growing process of alfalfa above and below ground with the help of VBA and VC++.3. Verification of alfalfa growth model with pot experiment. The results show that simulated value and measured value are in good consistency. The model is greatly capable of describing the growing process of alfalfa above and below ground.