关键词: 长期定位试验, 氮肥利用率, 差减法, 累计计算法, 比值法, 土壤氮素平衡法

Abstract: By using the principles and methods of fractal geometry theory,the relationship between aboveground biomass and plant length or sheath height of Carex lasiocarpa population was studied,The results showed that there was a good staic fractal relationship between them.and the resulted fractal dimension was an efficient description of the accumulation of aboveground biomass in each organ.The dynamic fractal relationship showed that during the whole growing season,the increase of aboveground biomass had a self-similarity,being a fractal growth process and the pattern of its increase was the fractal dimension D.Based on these results,a fractal growth model of Carex lasiocarpa population was established ,which regarded the bigger grass as the result of the amplification of seedling growth.

Key words: long-term experiment, nitrogen use efficiency (NUE),  , traditional subtraction method,  , cumulative calculation method,  , ratio method,  , soil N balance method.