Huabin Li
Through the analysis of dialect materials from the Tang and Song dynasties, the Ming and Qing dynasties, and the modern era in Northwest China, it is found that in the northwest dialects during the Tang Dynasty and the Song Dynasties, the de, mai, mo-II rhymes (three Middle Chinese rhyme categories) had already been merged, with the main vowel being [e]. In a few cases, [e] was raised to [i], which led to the merger with the zhi, xi, xi rhymes (three Middle Chinese rhyme categories). During the Western Xia period, after these vowels reached the highest degree of raising, they began to undergo breaking, following the pattern of e > i > iə > ie. Such phonetic changes continued and developed in the Lanyin Mandarin of the Ming and Qing dynasties and in the modern Jin dialect. From the perspective of the identity and difference of phonetic changes, this characteristic of the Northwest Chinese dialects is of a cognate nature, not a result of contact-induced convergence. Under the influence of the Central Plains Mandarin, this phonetic change in the northwest dialects gradually retreated. Nowadays, it is only limited to the Jin dialect and the Lanyin Mandarin, mostly involving labial initial characters, and shows a declining trend. Rounded syllables do not participate in this phonetic change, and the phonetic changes of yangsheng rhymes and rusheng rhymes are not synchronized.