关键词: 土壤微生物群落结构, 磷脂脂肪酸, 罗浮栲天然林, 杉木人工林

Abstract: By the method of establishing artificial moisture gradient and based on completely controlling environment, an experiment was designed to study the relationships between soil water stress and flax (Linum usitatissimum) seedling emergence as well as the soil moisture critical value for the emergence resisting soil drought, aimed to ensure the springsowing crop seedlings safely in northern arid or semiarid regions of China. The responses of the emergence to soil moisture exhibited 3 types, i.e., jump, ascending, and S-curve. The moisturesensitive domain of the emergence was from 3.5% to 6.0% for sandy chestnut soil, and from 9.0% to 15.0% for meadow chestnut soil. Taking the emergence rate as a standard, the soil moisture threshold value was 5.5% for sandy chestnut soil, and 13.0% for meadow chestnut soil. With the drought-resistance and conserving seedling as the standard, the soil moisture threshold value was 5.0% for sandy chestnut soil, and the seeding level should be increased to 1.52 times of that in average years. When the soil moisture threshold value for meadow chestnut soil was 12.0%, the seeding level should be increased to 1.72 times of that in average years.

Key words: soil microbial community structure, PLFA, natural forest of Castanopsis fabri,  Cunninghamia lanceolata plantation.