Abstract: To understand the effects of light regimes on the height growth  of Pinus koraiensis saplings, an investigation was made under the canopies of secondary forests treated by light thinning (stand A), heavy thinning (stand B), and clear cut (stand C) as well as the currentyear height growth of P. koraiensis under the canopies. The canopy openness on the top of P. koraiensis saplings was measured by hemispherical photographs, and the relationship between the light regimes and the height growth increment of P. koraiensis saplings was established. The light transmittance in stand C dominated by Quercus mongolica was highers, while that in stands A and B dominated by mixed broadleaved species was lower. The major factor limiting the growth of P. koraiensis saplings was the shading of the understory broadleaved trees with a height of 10 m. The height growth increment of the P. koraiensis saplings in stand C was significantly higher than that in stands A and B. There was a significant positive relationship (R²=0.516, P<0.01) between the currentyear height growth increment of P. koraiensis saplings and the canopy openness. It was suggested that to accelerate the positive succession of the secondary forests in eastern Liaoning Province, the canopy openness on the top of P. koraiensis saplings should be modified to more than 30%.

Key words: root characteristics, available potassium releasing from mineral, mechanism of potassiumenriched.