Abstract: By using emergy analysis theory and method, this paper analyzed the emergy flow and ecological value of the forest ecosystem in Haxi area in eastern part of Qilian Mountains’ northern slope. In the study area, the input energy flow of forest ecosystem was larger than the output energy flow, indicating that the energy was accumulating in the forest ecosystem. Through energy flow, low-quality energy transformed into high-quality energy, and the environment of the ecosystem was relatively safe. The total emergy of five ecological services, including organic matter production, water conservation, soil maintenance, CO2 fixation, and air purification was 9.35 ×1021 sej, and the total emergy monetary value was 7.77×108 US$. The emergy monetary value of water conservation and soil maintenance was apparently higher than that of other services. The monetary value of each service was in the order of water conservation > soil maintenance > air purification > organic matter production > CO2 fixation. Water conservation was the most important ecological service in the study area, and the proportion of the emergy monetary value of water conservation was 69.6%. Among different vegetations, shrub land had the largest value of water conservation, while arbor forest had the largest value of water conservation per unit area.

Key words: Bombax ceiba, fiber development, capsule fiber, anatomical structure, dry-hot valley.