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在我国南方亚热带湿地松人工林设置了3个水平的野外氮添加控制试验(0、40、120kg N·hm~(-2)a(-1)),于2014和2015年生长季高峰期(7月底)和末期(10月底)采集湿地松成熟绿叶和落叶,分析外源氮添加对湿地松叶片碳(C)、氮(N)、磷(P)、钾(K)、钙(Ca)、镁(Mg)、铝(Al)、铁(Fe)、锰(Mn)9种元素浓度及其养分回收的影响.结果表明:N添加显著增加了湿地松绿叶中N、Al、Mn浓度,降低了P和2014年的Ca浓度,而对C、K、Mg、Fe浓度无显著影响.N添加显著提高了绿叶N/P,且该比值及绿叶养分浓度(N、P、Mn)对N添加的响应依赖于N的剂量(高N条件下响应更强).N添加显著降低了2015年N的回收效率,提高了2014年K的回收效率.相比于养分回收效率,回收能力对增加的可利用氮响应更强.N添加显著降低了N的回收能力,提高了P、K的回收能力,降低了枯叶中的Fe浓度,而对枯叶中Ca、Mg、Al、Mn浓度无显著影响.这表明,N添加对叶片化学计量的影响因不同元素而异,植物会通过调整自身的养分内循环(养分回收)来应对环境变化.N添加提高了绿叶N/P和K/P,说明氮添加条件下植物生长可能由N、P共同限制转变为P限制.氮添加增加了绿叶中Al、Mn浓度,表明N添加下湿地松面临潜在的金属离子毒性风险升高.
Three levels of field nitrogen addition control trials (0, 40, 120 kg N · hm -2 (a) -1) were set up in the subtropical Pinus elliottii plantation in southern China. During the peak season of 2014 and 2015 The mature green leaves and deciduous leaves of P. elliottii were collected at the end of July and the end of October. The effects of exogenous nitrogen on the contents of carbon (C), nitrogen (N), phosphorus (P), potassium (K) , Magnesium (Mg), aluminum (Al), iron (Fe) and manganese (Mn) were studied.The results showed that N addition significantly increased N, Al and Mn concentrations in the leaves of P. elliottii, P and Mn concentrations decreased in 2014 and 2014, respectively, but had no significant effect on the concentrations of C, K, Mg and Fe.N addition significantly increased the N / P ratio of green leaves, and the ratio of N and P The response to add depends on the dose of N, which is more responsive at high N. The N addition significantly reduces the recovery efficiency of N in 2015 and increases the recovery efficiency of K in 2014. The recovery capacity increases compared to the nutrient recovery efficiency Of available nitrogen had a stronger response, N addition significantly reduced the recovery ability of N, enhanced the recovery ability of P and K and decreased the Fe concentration in dead leaves, while the concentration of Ca, Mg, Al and Mn in dead leaves was no Significant impact This shows that N The effect of added stoichiometry on leaf stoichiometry varies with different elements, and the plant responds to environmental changes by adjusting its own nutrient internal recycling (nutrient recovery) .N addition increased N / P and K / P of green leaves, The growth may be limited by the common restriction of N and P. The nitrogen addition increases the concentration of Al and Mn in the green leaves, indicating that the increased risk of potential metal ions toxicity to Pinus elliottii under N addition.