干旱区生态环境知识资源中心

Rainout shelters and irrigation systems were manipulated in a Mongolian pine plantations to simulate changes in precipitation amount and to explore how it would affect soil N availability in in Keerqin Sandy lands. Both reduced (RP) and increased (IP) precipitation treatments significantly affected soil inorganic N concentration, increasing it through the growing season under RP treatment, and decreasing it under IP treatment, in most growing season. Soil microbial biomass N in each month was significantly reduced by RP and raised by IP. Mongolian pine growth and root biomass were significantly reduced by precipitation decrease, while they had no significant response to precipitation increase. Above ground net primary productivity was reduced by precipitation decrease and was increased by precipitation increase significantly. Results indicated the asynchrony of soil moisture and soil nutrient availability in Mongolian pine plantations. Water availability is the overriding limiting factor on grass growth in Horqin Sandy Lands when precipitation decrease, and N limitation became increasingly important when precipitation increase.