供氮水平对长白落叶松幼苗生物量、氮磷浓度及其季节变化的影响

在温室内以长白落叶松幼苗为材料进行砂培试验,探讨了4种不同氮素浓度(1、4、8、16 mmol/L代号分别为N₁、N₄、N₈、N₁₆)处理对长白落叶松幼苗生物量以及根、茎、叶氮磷分配的影响。结果表明:①氮素供给浓度显著影响幼苗生物量,7、8、9月份均在N₈水平下达最大,从7月份到9月份,叶片生物量占全株比例逐渐降低,而根系生物量所占比例逐渐增加。②随着供氮水平的提高,苗木根、茎、叶中氮浓度明显增加。生长末期根、茎、叶中氮浓度平均达到生长初期的1.46、1.48、1.17倍。不同氮处理下幼苗根、茎和叶全磷浓度呈现波动性变化。③幼苗体内氮贮量随着落叶松的生长呈明显上升趋势。9月份全株氮贮量比7月份平均增加了2.86倍。氮贮量分配在不同部位有很大不同,分配到叶片中的比例在7月份最高,平均为60%,而分配到幼苗根系中氮贮量的比例随苗木的生长而逐渐增加,在9月份相对值最高,达到41%。不同氮处理之间氮贮量分配比例相差不大。④长白落叶松幼苗根、茎、叶磷贮量变化规律与氮贮量一致,只是变化幅度低于氮。

Effects of different nitrogen supply on biomass,N and P concentration and their seasonal variation of Larix olgensis seedlings

The effects of different concentration of nitrogen treatments on the biomass, nitrogen and phosphorus partition in roots, stems and leaves of one-year-old Larix olgensis seedlings were studied by a sand culture experiment in greenhouse. The results suggested that N supply could significantly increase the seedling biomass. The biomass of roots, stems and leaves were the highest when 8 mmol/L nitrogen was applied in July, August and September. The biomass of leaves decreased gradually, while that of roots increased from July to September. The N concentrations increased significantly along with the N supply levels increasing. The mean N concentrations in roots, stems and leaves in the latter growth stage were 1.46, 1.48 and 1.17 times respectively more than that in the initial stage. The P concentrations fluctuated with the N levels change. The N stocks of whole plant increased markedly as the growth of plant, and it was 2.86 times more in September than in July. The N allocation also varied in leaf, stem, and root. The proportion of N allocation in leaf was the highest in July(60% in average). The proportion of N allocation in root increased with plant growth, which was the highest in September(41% in average). There was no obvious difference in N stocks among different N levels. The P stocks of the roots, stems and leaves were basically consistent with the N, but the variation scope was smaller than that of N.