| Acid rain is one of the worldwide regional disasters by which China is the third largest area after Europe and North America. Numerous research progresses regarding acid rain have been reported worldwide. It has been almost unknown, however, that the effect of acid rain on Chinese herbs, microbial species, and microbial activity in the natural habitat of herbs.The thesis observes the effects of acid rain on the soil nutritional composition, microbial biomass, microbial activity, and growth of herbs, in the tested soil and three Chinese herbs, including Airactylodes macrocephala, Corydalis yanhusuo and Fritillaria thunbergli treated by soaking or spraying with simulated acid rain at pH 2.5, 3.5, 4.5, and 50, respectively, and takes an extra controlled CK as a reference, which specially focused on the soil nutritional composition and growth of Atractylodes macrocephala. The results obtained showed as the followings: (1) Acid rain caused the acidification of soil and the pH values of soil decreased obviously with the decline of acid rain pH. Acid rain interfered with :hemical behavior of the multi-kinds of elements, and destroyed their balance in soil. As a result, it led to the loss of organic matter and some cations, the reduction of base saturation degree, and the loss of the buffering capacity of soil. (2) In the different treated soils with icid rain at various pH, the effect of acid rain varied, but it had a similar trend. Acid rain inhibited the growth of bacteria, actinomycetes and influenced the growth of fungi. The 'esults also showed that acid rain could inhibit the growth and reproduction of bacterial group for nitrogen cycling and affected also the growth of cellulose-decomposing microbes, rhe total numbers of various group of microbe in the soil were decreased. Furthermore, thehigher the acidity of acid rain, more severe inhibition there was. (3) Acid rain inhibited the activities of dehydrogenase, catalase, urease, and protease. The lower the pH of acid rain, more severe inhibition there was, exception of phosphatase. Moreover, acid rain inhibited microbial respiration, cellulose decomposition, ammonia-oxidation, and nitrogen-fixation with different degrees. (4) Acid rain reduced the total number of microbes in rhizospheric soil. However, with the presence of roots, the effect of acid rain on rhizospheric microbes was different from non-rhizospheric microbes. (5) Acid rain also affected the growth of herb itself It inhibited the seed germination of Atractylodes macrocephala, reduced the viability of seeds, and the amount of chlorophyll in leaves, therefore leading to the decrease of photosynthesis.Based on the comprehensive analysis of acid rain effects on physical-chemical properties of soils tested and microbes, it could be concluded that long-term effect of acid rain is detrimental to the ecological balance of soil, not only leading to the reduction of biological activities but also affecting the persistable development of agriculture.
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