Abstract: hrough investigation,this paper classified the green lands in Xi'an into six planting structures, i.e.,trees+shrubs+herbs (T+S+H),trees+herbs (T+H),shrubs+herbs (S+H),trees (T),shrubs (S),and lawn (L).After determining the photosynthetically active radiation,relative humidity,temperature,noise,and bacteria in the air in the center and outside of the green lands,the ecological functions of the green lands on regulating urban microclimate were analyzed.All kinds of these green lands had the function of shading,which was decreased in order of S>T+S+H>T+H>S+H>T> L.Green lands also had obvious effect on lowering temperature,with the order of T+S+H>T>S>T+H>S+H> L.The effect of increasing humidity was in order of T+H > T+S+H>T>S>S+H> L,that of lowering noise was in order of T+S+H>T+H>T>S+H>S> L,and that on killing bacteria was in order of T+S+H>T+H>T>S+H>S> L.Green lands with multilayer structure had greater ecological functions than those with single layer.According to above results,the measures of increasing ecological functions of urban green lands were put forward.

Key words: Soybean (Glycine max L.), Allelopathy, Hydroxy phenylacetic acid