The research was made that the change of component of soil humic substances in larch plantations and its effects on the soil acidity at the different development stages (young stand, half_mature stand, near mature stand, mature stand and young stand in the second rotation).

After 50 years forestation, the larch plantations have already became near-mature forest or mature forest and been the important commercial forest base now.

Effect of major environment of canopy openness produced by thinning in larch plantation;

The effect of Zeiraphera lariciana and Zeiraphera grisecana on growth of larch plantations;

Soil acidity change of Larch plantations and relation between change and inorganic phosphorus types;

The soil degradationin in Larix olgensis plantations, to a certain extent, has been found.

Models for simulating locational distribution of total branches, both along and around the bole, and for estimating crown profile of primary branches within live crown were developed in a 26-year-old Larix olgensis plantation based on the circular branch analysis technique.

This study was conducted based on the common characteristics of low mixture degree and uniform distribution of Larix olgensis plantation in a 15-year-old plantation.