The study looked at how different factors like the density of trees, width of shelterbelts, and height of trees affect wind speed in dry farmlands in North China. They found that shelterbelts with sparse structures had the best windbreak effect, while ventilated shelterbelts were the least effective. Windbreaks with a porosity between 0.30-0.50 had the best effect. The angle of the shelterbelt in relation to the wind direction also played a role in wind speed reduction. Wider shelterbelts had diminishing returns in windbreak effectiveness. Overall, the density of trees, width of shelterbelts, height of trees, and wind direction are the main factors that determine how well a shelterbelt can reduce wind speed.