氮添加对大果木姜子凋落叶分解及养分释放的影响

  目的  研究不同施氮水平对大果木姜子Cinnamomum migao凋落叶养分分解的影响。  方法  于2017年1月，以药用植物大果木姜子人工林凋落叶为研究对象，将凋落叶清洗风干后装入分解袋中，每袋10.00 g。试验期间放置在不同施氮处理[对照(ck，0 g·m?2·a?1)、N₁(5 g·m?2·a?1)、N₂(15 g·m?2·a?1)、N₃(30 g·m?2·a?1)]样地中，每处理3个重复，分别于试验的3、5、7、9、11月采集凋落叶样品，测定凋落叶质量及养分质量分数的变化，分析氮沉降对大果木姜子凋落叶养分释放动态影响。  结果  凋落叶分解试验结束时，各施氮组凋落叶质量损失率整体小于ck，凋落叶残留率整体大于ck，且N₂与ck差异不显著，N₂、N₃差异显著(P＜0.05)，ck、N₁、N₂、N₃凋落叶分解95%时所需的时间分别为2.973、3.626、3.285、3.671 a；各处理凋落叶碳质量分数总体均呈下降趋势，全氮质量分数整体上均呈先增加后降低的趋势，全磷与全钾质量分数变化趋势相似，为分解初期下降，之后整体上升，最后趋于平稳；各处理凋落叶碳、全磷、全钾残留率总体呈降低趋势，全氮残留率整体上呈先上升后下降趋势。其中分解各时段各施氮处理碳残留率均显著高于ck (P＜0.05)；随着时间推移，ck处理氮的残留率呈先上升后下降趋势，各施氮处理的氮残留率整体上呈先上升后下降趋势；整个分解过程中各施氮组碳氮比均小于ck，且分解前期与ck表现出显著差异(P＜0.05)。  结论  添加氮不利于大果木姜子凋落叶的分解及养分的释放，且施氮越多抑制分解作用更显著。图4表1参33

Effects of nitrogen addition on decomposition and nutrient release of Cinnamomum migao litter leaves

  Objective  This research aims to examine the effects of different nitrogen application levels on nutrient decomposition of Cinnamomum migao litter leaves.  Method  In January 2017, the litter leaves of the medicinal plant C. migao were taken as the research object. The leaves were washed, air dried and put into decomposition bags, 10.00 g each. Nitrogen treatments were designed as ck(0 g·m?2·a?1), N₁(5 g·m?2·a?1), N₂(15 g·m?2·a?1), and N₃(30 g·m?2·a?1), and there were three repetitions for each treatment. The samples of litter leaves were collected in March, May, July, September and November, respectively. The quality and nutrient contents of the leaves were measured, and the dynamic effects of nitrogen deposition on nutrient release from the leaves were analyzed.  Result  At the end of litter decomposition experiment, the mass loss rate of litter leaves in all nitrogen application groups was lower than that of ck, the residue rate of litter was higher than that of ck. The difference between N₂ and ck was not significant, but the difference between N₂ and N₃ was significant (P＜0.05). The time needed for 95% decomposition of ck, N₁, N₂ and N₃ was 2.973, 3.626, 3.285 and 3.671 a, respectively. In the leaves of all treatments, the content of C decreased and the content of total N increased first and then decreased, while the content of total P and total K was similar, which decreased at the initial stage of decomposition, then increased as a whole, and finally stabilized. The residual rates of C, total P, total K in the leaves decreased, while the residue rates of total N increased first and then decreased. The residual rate of C in each nitrogen treatment was significantly higher than that of ck (P＜0.05). With the passage of time, the residue rate of N, which increased first and then decreased in ck treatment, showed an overall upward and then downward trend in each nitrogen application treatment. C/N ratio of each nitrogen application group was lower than that of ck in the whole decomposition process, and there was a significant difference between the early decomposition stage and ck (P＜0.05).  Conclusion  Nitrogen addition is not conducive to the decomposition and nutrient release of litter leaves. The more nitrogen is applied, the more obvious the inhibition of decomposition is.[Ch, 4 fig. 1 tab. 33 ref.]