Abstract: Based on 57 years (from 1960 to 2016) data of daily precipitation, temperature, sunshine hours, relative humidity, wind speed and vapor pressure from 70 meteorological stations in Shanxi, we calculated modified relative moisture index (M_10i) using the relative moisture index (M). The spatial distribution of drought frequency and intensity in Shanxi was analyzed at annual and seasonal scales. The results showed that drought years were well expressed by M_10i. In the study period, annual drought intensity tended to be more serious. Drought was light in the 1960s, and became serious in the 1980s and 1990s, then continuously decreased. Spatially, drought intensities were higher in the north and lower in the south, with the most severe drought in the north and the middle part of Taiyuan. Drought was more serious in winter and spring than in summer and autumn. Specially, heavily severe drought occurred with the highest frequency, followed by severe drought, light drought, and moderate drought. Drought happened most frequently in winter, followed by spring, autumn and summer in Shanxi.

Key words: plant size, stand age, ecological stoichiometry, nutrient transfer,  Machilus pauhoi.