模拟凋落物添加与氮磷沉降对红松凋落物生态化学计量特征的影响

Effects of simulated litter addition,and nitrogen and phosphorus deposition on ecological stoichiometry of Pinus koraiensis litter

【目的】探究红松(Pinus koraiensis)凋落物和氮(N)磷(P)沉降量、小气候因子、降水化学成分和地形对各层凋落物生态化学计量的影响,为红松林管理提供科学依据。【方法】本研究对阔叶红松混交林(天然林)和红松纯林(人工林)进行了为期712天的原位观测试验,模拟氮磷沉降与凋落物添加处理后,测定不同凋落物层次和林型的碳(C)、N、P含量,并对未分解层(L层)、半分解层(F层)、粗腐殖质化的枯枝落叶层(H层)生态化学计量学进行分析。【结果】1)凋落物添加量的差异导致其生态化学计量在各层凋落物中的含量显著不同。营养物质的周转速度在H层最快,其C∶N、C∶P、N∶P也较L、F层小。2)组成较复杂的高量凋落物在氮磷添加和凋落物添加处理下会抑制N、P富集,但有利于C的沉积;组成较单一的低量凋落物虽在N、P添加和凋落物添加处理下也会产生C沉积,但N、P的变化特征却与高量凋落物完全相反,表现为促进N富集和P富集。3)小气候因子和降水化学成分与生态化学计量呈正相关关系,尤其是温度和降水pH。【结论】本研究揭示了阔叶红松混交林和红松纯林中凋落物C、N、P生态化学计量特征及其随季节变化的动态趋势,推断阔叶红松混交林和红松纯林凋落物的分解主要受磷素限制,同时磷素可能是红松生长的限制因子。

【Objectives】We assessed the effects of litter quality,nitrogen and phosphorus addition,microclimate factors,precipitation chemistry and topography on ecological stoichiometry of Pinus koraiensis litter to provide scientific basis for management of Pinus koraiensis forest.【Methods】We conducted a 712-day observation experiment in broad-leaved Pinus koraiensis mixed forest(natural forest)and Pinus koraiensis pure forest(plantation).After nitrogen and phosphorus addition and litter treatment,the contents of C,N and P in different litter layers and forest types,as well as the ecological stoichiometry of undecomposed layer(L layer),semi-decomposed layer(F layer)and humic litter layer(H layer)were analyzed.【Results】1)The differences in litter quality resulted in significantly different ecological stoichiometry of the litter layers.The fastest turnover of nutrients was found in the H layer but the C∶N,C∶P,N∶P in H layer were smaller than those in L and F layers.2)The high-quality litter with complex composition inhibited N and P accumulation,but was beneficial to the deposition of C under N-P and litter addition.Although the low-quality litter with single composition produced C deposition under N-P and litter addition,the N and P addition promoted N and P enrichment.3)Microclimate factors and precipitation chemistry were positively correlated with ecological stoichiometry,especially temperature,precipitation,and pH.4)There were significant interaction effects of litter treatment,N-P deposition treatment,slope and temperature on ecological stoichiometry of litter.【Conclusions】This study reveales the eco-stoichiometric characteristics and seasonal variation trend of litter C,N and P in broad-leaved Pinus koraiensis mixed forest and Pinus koraiensis pure forest.We can infer that the litter decomposition in broadleaved Pinus koraiensis mixed forest and Pinus koraiensis pure forest is mainly limited by P.At the same time,P element may be the limiting factor of Pinus koraiensis growth.