Abstract: In this paper, a comparison study was made on the characteristics of soil available nutrients inEucalyptus pure plantation (EPP), Acacia pure plantation (APP), and mixed plantations ofEucalyptus and Acacia planted row by row (MPRR) and individual by individual (MPII). The results showed that soil NO₃^--N content in APP and MPRR was much higher than that in EPP, and similar pattern was observed for soil NH₄⁺-N content. Eucalyptus plantation mixed with legumes could remarkably improve soil nitrogen supply. Soil available phosphorus content was the highest in EPP but the lowest in APP, which might result from the high P content in shed leaves in EPP and the accelerated plant growth under high soil nitrogen supply in APP. No distinct difference of soil available potassium and boron contents was observed among the four plantations, only with a slightly higher K and lower B in APP. The different patterns of soil K and B in APP might result from the different absorption of the two elements by APP. Soon after the establishment of plantations, soil available B dropped to a very low level, but then increased steadily.

Key words: Kerqin sandy land, Caragana microphylla, Artemisia halodendron, Artemisia frigida, Populus spp., Physiological characteristics