Research On Dynamic Simulation Of Canopy Structure For Walnut In Agroforestry Systems

Agroforestry system has important value in the practice of resolving the contradictions ofagricultural and forest land use, improving the ecological environment and the use efficiency ofnatural resources, promoting the rural economic development. Dynamic simulation technologysystems of fruit tree canopy were constructed in the fruit-crop intercropping system. Thistechnology system has important technological support roles in forecasting the structure ofagroforestry system scientifically, further studying on prediction and evaluation of the functionand effect for agroforestry system, and increasing the efficiency of regulation and managementfor agroforestry system. Compared to experimental research and treatment on field, applicationof this technology system can also reduce expend of manpower and material resources andincrease research level and efficiency to some extent. The walnut-crops/herb intercroppingsystem is important land-use way, and is also one of main pattern for reafforestation projects.The dynamic simulation research of tree canopy structure in agroforestry system with walnuthas well typical and practical application. Application of the research results can be beneficialto the harmonious development of economy and ecology in different types of fragile ecotope ofthe low hilly areas.The observation experiment of field for walnut(Juglans regia) growth and canopygeometric structure were done in walnut experimental plot of Xiaolangdi Forest EcosystemResearch Station of the Yellow River which located in Jiyuan, Henan province during2008-2011. As the extraction of morphological parameter was very complicated and spatial andtemporal resolution was low in relative field measure technology and model of tree geometrystructure, two key technologies including three dimensional morphological character parametermeasurement and geometry simulation of canopy geometric structure were adopted. Takinggrowth phase as time dimension, theories and methods containing mathematics, fractal theoryas well as computer visualization technology were synthesized, and field experiment and numerical simulation test were constructed in the agroforestry system based on a great deal ofmeasured data. The main results are as follows:(1) A multi-baseline close-range photogrammetry technology to establish the3D geometrymeasurement technology in trees was adopted. The technology was based on estimates ofcanopy geometrical parameters, which involving in measurement of plant three-dimensionalcoordinates; estimates of the plant height and brest diameter of trunk, length, basal diameter,growth tilt angle and stretch direction of lateral branch. This technology offered a cheap andpractical technology of obtaining forest geometry data and character parameters for therealization of the forest virtual plant.The measurement and its accuracy of this method was based on the measuring precisionof three-dimensional coordinate for walnut plant. The case analysis showed that the absoluteerror of X-coordinate was0.000-0.023m, and0.006m for the averaged value, the relative errorwas0.000%-0.162%,0.042%for the averaged value; the absolute error of Y-coordinate was0.001-0.032m, and0.006m for the averaged value, the relative error was0.007%-0.240%,0.047%for the averaged value; the absolute error of Z-coordinate was0.000-0.031m, and0.002m for the averaged value, the relative error was0.000%-0.269%,0.020%for theaveraged value. The measuring precision fully met the requirements of quantitative expressionfor plant canopy geometric strcture.(2) A simulation model of walnut phonological development based on the concept of daynumber of effective development was established; and simulation models of growth withwalnut plant height, trunk thick, lateral branch length and height, and the model of leaf shapeand leaf growth were established. Establishment of these models provides the basic parametersand data of three-dimensional geometry for the virtual plan.Compared to the observation data of walnut phonological development in2011, theabsolute error of simulation value of phonological model in whole growth season was2-4day,the relative error was0.0%-1.2%.Compared to the observation data of tree height and brest diameter for15walnut plants in2011, the absolute error of simulation value for tree height was0.8-61.8cm and the average was27.6cm, the relative error was0.2%-14.1%and the average was5.5%; the absolute errorof simulation value for tree brest was0.1cm-3.2cm and the average was1.4cm, the relativeerror was0.4%-24.5%and the average was11.4%. On average for15plants, the tree heightwas505.5cm and the brest diameter was12.7cm, the absolute and relative error for tree heightwas respectively4.7cm and0.9%, the absolute and relative error for brest diameter wasrespectively0.3cm and2.4%.Compared to the measured data for59leaflets of7compound leaves, the absolute error ofsimulation value for the single leaflet was0.0-14.9cm2, the average was2.2cm2, the relativeerror was0.2%-11.9%, the average was3.8%.(3) Based on the OpenGL3D visualization technology and L-system Fractal Technologywith Virtual plant simulation capability, a visualization model of dynamically simulatingwalnut's single plant growth was established.On the basis of establishing a single plant model, a stand scale, four-dimensional virtualplant growth model was constructed. This model used leveled and layered implementation,changing of the size and stretching angle for lateral branches, changing of blade angle andcolor shades, a vector angle calculation to achieve multi-row plant simulation.These models were developed with modularization. Model in terms of growth parameterswith branches and leaves had the corresponding input interface, while achieving the expressionof quantification of plant growth models and graphical plant geometry. It laid a goodfoundation to further improve the model system.(4) Based on blade shape and the Monte Carlo probability method with pixel as thecalculated cell, the Boolean algorithms of geometry was adopted to simulate the canopy lighttransmission characteristics in single-plant and stand scale respectively. The error analysis forsimulation value of canopy transmittance showed that the relative error was15%. Thesimulation model basically had the quantitative description function of the dynamic predictionof solar radiation transfer law in the agroforestry systems. Model could providewalnut-crops/herb intercropping system with the support of the radiation data. Furtherimproving of these models was anticipated. (5) The reasonable intercropping years and spatial configuration for agroforestry systemsuch as walnut-cash crops and walnut-herb were suggested, which being based on thesimulation result of canopy radiation transfer for walnut in walnut-crop/herb intercroppingsystems, combining with temperature and photoperiod characteristic of cash crops andmedicinal plants which being local and common such as cassia(Catsia tora Linn),mung-bean(Vigna radiata), red bean(Vigna angularis), capsicum(Capsicum frutescens) andpeanut(Arachis hypogaea). These suggestion could provide important instructive effect forstructure control and regulation as well as sustainable management of agroforestry system atdifferent age of fruit tree. Meantime, the above research also established a basis for simulationexperiment of growth and development of intercropping crop in the co-growth period in thefuture.The above results will have extensive application foreground in the management practiceof agroforestry system after gradual improvement, and can provide important technologicalsupport for the implement of national ecology strategy. Whereas, the actual research time isonly4years, and researches only has focused on part of the tree growth periods, which isobviously insufficient for growth and development simulation of fruits like walnut which has arelative long growth cycle. Therefore, acquirement of further research results need long-termlocation study, and long-term quantitative study of the interaction between the dynamic changeof tree geometry character parameter and environments such as light, temperature and water inagroforestry system should be enhanced especially.