氮添加对天然油松林油松不同器官N⁃P分配策略的影响

Effects of nitrogen addition on N⁃P allocation strategies in different organs of Pinus tabulaeformis in its natural forest

作为植物重要器官,叶、茎、根对环境变化的响应策略一直是生态学研究的重要课题。然而,植物不同器官的氮⁃磷(Nitrogen⁃Phosphorus)分配策略对氮沉降的响应规律仍不清楚。为了揭示不同器官的养分对氮添加的响应规律,本研究以山西太岳山天然油松林为研究对象,设置4个人工氮添加水平,分别为对照(CK,0 kg hm^(-2)a^(-1))、低氮(LN,50 kg hm^(-2)a^(-1))、中氮(MN,100 kg hm^(-2)a^(-1))和高氮(HN,150 kg hm^(-2)a^(-1)),模拟氮沉降对油松不同器官N⁃P分配策略的影响。实验结果表明:1)随着氮添加浓度的增加,茎N含量显著降低(P<0.05),根N含量显著增加(P<0.05);茎P含量在低氮条件下与其他氮添加水平相比显著降低(P<0.05);叶N∶P在低氮条件下与其他氮添加水平相比显著增加(P<0.05),茎N∶P在高氮条件下与其他氮添加水平相比显著降低(P<0.05)。2)叶片的N含量和P含量在不同氮添加浓度下表现出显著的异速生长关系,高氮条件下会导致植物分配给叶和茎基于单位磷含量分配的氮含量显著降低,根在N、P养分关系中的变化速率具有一致性。3)氮添加处理下,根比茎和叶在分配单位含量的P素时会分配更多的N素。低氮条件下是油松生长的最佳环境,根、茎、叶三个器官氮磷分配的异速生长关系存在显著差异,其生长表现为对P的快速分配。以上结果表明,油松不同器官对氮沉降的响应存在差异,并且持续的氮添加会导致油松适应性的改变。

As important plants′organs,the response strategy of leaves,stems and roots to environmental changes plays an important role in ecological research.However,the response of nitrogen⁃phosphorus allocation strategies to nitrogen deposition in different plant organs is still unclear.In order to reveal the response of nutrients in different organs under nitrogen addition,we selected Pinus tabulaeformis forest in Taiyue Mountain of Shanxi Province as the research materials.Four artificial nitrogen levels were set as control(CK,0 kg hm^(-2)a^(-1)),low nitrogen(LN,50 kg hm^(-2)a^(-1)),medium nitrogen(MN,100 kg hm^(-2)a^(-1))and high nitrogen(HN,150 kg hm^(-2)a^(-1)).The results showed that:1)With the increase of nitrogen addition level,the N content in stem decreased significantly(P<0.05),the N content in root increased significantly(P<0.05);The P content in stem decreased significantly under low nitrogen condition(P<0.05);The N∶P of leaf increased significantly under low nitrogen condition(P<0.05)and the N∶P of stem decreased significantly under high nitrogen condition(P<0.05).2)The N and P contents of leaves showed a significant allometric relationship under different N addition levels.Under high N condition,the N content allocated to leaves and stems based on P content per unit was significantly reduced,and the rate of change in the N and P nutrient relationship between roots was consistent.3)Under nitrogen addition,the root allocated more N than the stem and leaf by using per unit P content.Low nitrogen was the best environmental condition for the growth of Pinus tabulaeformis.There were significant differences in the allometric growth relationship of nitrogen and phosphorus distribution in root,stem and leaf,and the growth showed rapid distribution of P.The results showed that the responses of different organs of Pinus tabulaeformis to nitrogen deposition were different,and nitrogen addition would lead the changes of adaptability of Pinus tabulaeformis.