Abstract: The nutrient contents in plant tissues have a seasonal variation during the process of plant growth. Aiming at this feature, the shoot tisses (induding stems and leaves) of Stipa baicalensis were collected in growth season (from May to September, 2009), and their decomposition characteristics and related affecting factors were studied by using litterbags. The shoot tissues collected in different months had obvious difference in their decomposition rates, being decreased in the order of May > June > July > August > September. The decomposition rates of the substrates were significantly positively correlated with their initial nitrogen, phosphorus, zinc, potassium, magnesium, and manganese contents, significantly negatively correlated with their initial carbon content and C∶N, but less correlated with their initial calcium content and N∶P. There was an obvious correlation between the soil microbial biomass nitrogen and the remaining mass of the substrates. In addition, the soil microbial biomass nitrogen had obvious correlations with the substrate carbon and nitrogen contents. The mass loss of the substrates had significant positive correlation with soil moisture content but weak correlation with soil temperature, suggesting that precipitation change could affect litter decomposition via affecting soil moisture content.

Key words: agricultural heat resource, crop cultivation zone, cotton, potato, Shanxi.