Abstract: In 2005, sampling plots were set up in the farmland shelterbelt networks in Changling County, Songyuan City, Jilin Province to determine the gross caloric and nutrients (C, N and P) content of each component of poplars (Populus × cv. Bailin 2), maize (Zea mays) and soybean (Glycine max), with the annual economic benefits of poplar, maize and soybean as well as the profit of crop straw utilization analyzed. The results showed that the annual economic benefit per hectare was 5 110 yuan (RMB) for maize and 3 965 yuan for soybean. The aboveground parts of maize and soybean straws could generate caloric 113 318 800 kJ·hm^-2 (796 yuan profit) and 61 294 400 kJ·hm^-2 (430 yuan profit), respectively, when they were used to generate electricity, which could increase the profit by 15% for maize and by 10% for soybean. It was estimated that an investment of 1 176 yuan·hm^-2 for maize and 789 yuan·hm^-2 for soybean was needed if compound fertilizer was used to compensate the nutrient loss caused by straw utilization, indicating that such an investment couldn’t match the profit of straw utilization. The annual ecomomic benefit for poplar was 3 690 yuan per nectare, being lower than maize and sybean.

Key words: Soil microbial community, Microbial biomass, Metabolic diversity patterns, BIOLOG, Forest restoration