Effect of freezing-thawing on nitrogen mineralization in vegetation soils of four landscape zones of Changbai Mountain

Introduction We studied the effect of freezing-thawing on nitrogen (N) mineralization of four vegetation soils from typical vegetation zones of Changbai Mountain with a laboratory incubation experiment. The soils were treated with two levels of soil water content, representing the low and high soil water contents found during late autumn and early spring in Changbai Mountain, respectively, and underwent cycling of freezing at -5 or -25 degrees C and thawing at 5 degrees C up to 15 times. Objectives The main purpose of this study was to examine the effects of freezing temperature, frequency of freezing-thawing cycles, and soil water content on N mineralization of four soils to reveal the different effects of spring and autumn freezing-thawing on soil N mineralization in Changbai Mountain. Results The results showed that inorganic N in the soils increased 1.67-26.77 times after 15 cycles of freezing-thawing, but N mineralization rate decreased with increased cycling of freezing-thawing. The lower freeze temperature and higher soil water content generally enhanced soil N mineralization. The results implied that freezing-thawing of vegetation soils to increase soil N mineralization to favor the growth of plants, and also increase the possibility of runoff loss of soil nutrients, is more effective in the spring than in the autumn.