Abstract: The concept of "beautiful mountains and valleys" is proposed in the paper as well as its evaluation index system. Further more, preliminary discussion is made on the evaluation of eco-environment construction in the arid area of Northwestern China. The concept is put forward in view of the severe desertification in Northwestern China and needs the establishment of an integrated ecosystem to be realized. The maintenance and balance of the ecosystem should be achieved by biological measures. The integrated forestry ecosystem is the final goal of "beautiful mountains and valleys", which can be reached through long-term development and construction. The semi-integrated forestry ecosystem is a temperary goal of "beautiful mountains and valleys", which also needs a long time to realize. Followings suggestions are proposed based on the construction of semi-integrated forestry ecosystem: partition of natural geo-region in the arid area of Northwestnre China; partition of unit for evaluating the forestry ecosystem; setting up principles and requirements for the evaluation index system; selecting indexes for forestry eco-environment evaluatian; determination of index weights; thoughts and establishing methods for forestry ecosystem evaluation.

Key words: root cell wall of tea plant, lead, chemical modification, adsorption.