Abstract: In this article, a Paulownia-wheat intercropping system was used as an example to study the relationships of wheat yield with shelterbelt structure and its coverage. The optimized structure of Paulownia-belt was formulated through a series of mathematical models. The results show that during one rotation of Paulownia, the average of relative accumulative wheat yield reached the highest (105.4) when the average of accumulative shelterbelt coverage was 10.1～ 10.9 % which is the best one. The regression equation of the optimized distance (D) and Paulownia rotation period (T) is showed as follows: D=0.600+11.042T-0.787T²⁺0.0273T³(R²=99.9%) .

Key words: Paulownia-wheat intercropping, Shelterbelt coverage, Average of accumulative shelterbelt coverage, Shelterbelt distance, Rotation, climate change., statistical experiment, Lancang River, abrupt change, hydrological time series