Abstract: Based on the two-year man-made grassland experiments with alfalfa(Medicago sativa L.cv.Algonquin)and smooth brome grass(Bromus innermis Leyss cv.Carlton) under the different sowing patterns,which were with four treatments,namely one-line mixed sowing of alfalfa and smooth brome grass(TH),inter-line mixed sowing of alfalfa and brome grass(JH),mono-sowing of alfalfa(DM) and mono-sowing smooth brome grass(DW),the microclimate characteristics was studied.The results showed that both light intensity and wind speed were the highest in the DW treatment and the lowest in the DM treatment,while they were in between in the TH and JH treatments as the alfalfa was in initial bloom stage and smooth brome grass was in booting stage.The temperature was higher in the mono-sowing than that in the mixed sowing,while the relative humidity was higher in the mixed sowing than that in the mono-sowing.The average plant heights under the different sowing patterns were significantly negatively related with the average light intensity at 0 cm,20 cm and 40 cm above the ground with r0cm=-0.973,r20cm=-0.994 and r40cm=-0.973 respectively,and with average wind speed at 30 cm and 60 cm above the ground with r30cm=-0.959 and r60cm=-0.973 respectively.The light intercepted by the population of DM was the largest,but its bottom light came to light compensation point and leaves net photosynthetic rate in the bottom began to decrease.The bottom light intensity of TH and JH were appropriate,so the populations kept photosynthetic rate high and got relative higher biomass.

Key words: Sowing pattern, Sowing pattern, Alfalfa(Medicago sativa L.cv.Algonquin), Smooth brome grass(Bromus innermis Leyss cv.Carlton), Man-made grassland microclimate