关键词: Hedley磷素分级, 土壤磷, 阔叶红松林, 择伐干扰, 磷素有效性

Abstract: It is not clear how the shrubs in peatlands respond to nitrogen deposition and phosphorus input, which could impact ecosystem processes. Our objective was to investigate the effects of different levels of nitrogen and phosphorus addition on three deciduous shrubs and three evergreen shrubs in Hani Peatland of Changbai Mountains through six years of simulation experiment. The responses of deciduous shrubs (with reduced abundance and coverage and increased height) and evergreen shrubs (with reduced abundance, coverage, and importance value) to nitrogen addition were different, while their responses to phosphorus addition was similar. Interspecific difference existed at species level. Nitrogen addition inhibited the growth of Potentilla fruticosa and Vaccinium uliginosum, and decreased their abundance and coverage. Meanwhile, nitrogen a ddition facilitated the growth of Betula ovalifolia, and height, coverage and importance value increased. Among the evergreen shrubs, nitrogen addition only decreased the abundance and importance value of Chamaedaphne calyculata but had no effect on Ledum palustre and R. parvifolium. Phosphorus addition relieved nutrient limitation of these shrubs and increased the coverage of B. ovalifolia, the height and importance value of R. parvifolium and the abundance of C. calyculata. Interactive effects of nitrogen and phosphorus addition were observed for deciduous shrubs. When little or no nitrogen was amended, phosphorus addition had no effects on the height or importance value of deciduous shrubs. Under the condition of high nitrogen addition rate, phosphorus addition increased the height and importance value of deciduous shrubs. This result indicated that only addition of nitrogen and phosphorus at a certain ratio can promote the growth of shrubs. Our study suggests that nitrogen and phosphorus addition can affect shrub performance and change the competitive balance between the two types of shrubs. B. ovalifolia may obtain growth advantage and restrain the growth of other shrubs, which will have a profound impact on vegetation pattern in peatlands.

Key words: phosphorus availability., selective cutting disturbance, Korean pine broad-leaved forest, soil phosphorus, Hedley phosphorus fractionation