氮磷添加对亚热带常绿阔叶林土壤碳氮及其稳定性同位素的影响

Effects of nitrogen and phosphorus additions on soil carbon and nitrogen and their stable isotopes in a subtropical evergreen broad-leaved forest

【目的】通过分析氮磷添加对亚热带常绿阔叶林土壤碳氮及其稳定性同位素的影响,探讨大气氮沉降背景下森林土壤碳循环及其周转特征,为亚热带常绿阔叶林合理经营提供理论依据。【方法】在安徽省黄山市祁门县查湾自然保护区内全面勘查基础之上选取6个标准样地,设置对照(CK,不添加氮和磷)、氮加磷(N+P,添加N 100 kg·hm^(-2)a^(−1)+P 50 kg·hm^(-2)a^(−1))和氮(N,添加100 kg·hm^(-2)a^(−1))添加试验,分析不同氮磷添加处理和不同土层下SOC、TN和土壤δ^(13)C、δ^(15)N之间的差异。【结果】1)连续5 a氮磷添加对土壤有机碳(SOC)、土壤全氮(TN)和土壤碳氮比(C/N)无显著影响(P>0.05),SOC、TN大小依次为CK>N处理>N+P处理,土壤C/N大小为N处理>CK>N+P处理,均是N+P处理最小;2)连续5 a氮磷添加对土壤δ^(13)C、δ^(15)N丰度无显著影响(P>0.05),δ^(13)C、δ^(15)N丰度值大小均表现为N+P处理>N处理>CK;3)SOC、TN和土壤C/N比在不同处理下0~10 cm土层均显著高于10~20 cm土层(P<0.001),而土壤δ^(13)C、δ^(15)N值则随着土层深度的增加而增加,除CK两土层间无显著性差异外,N和N+P处理下10~20 cm土层土壤δ^(13)C均显著高于0~10 cm土层,N+P处理显著提高了10~20 cm土层δ^(15)N丰度。【结论】氮磷添加对亚热带常绿阔叶林土壤有机碳、全氮及土壤C/N影响不甚显著,其长期动态变化有待进一步的监测分析;氮磷添加对土壤稳定性碳、氮同位素的影响也不显著,但是氮磷添加均显著增加了下层土壤的δ^(13)C、δ^(15)N丰度,未来可结合土壤微生物做进一步分析。

【Objective】The effects of nitrogen(N)and phosphorus(P)addition on soil carbon and nitrogen and their stable isotopes in subtropical evergreen broad-leaved forest were explored in order to reveal the carbon cycling and turnover characteristics under atmospheric N deposition and to provide the basis for the reasonable forest management.【Method】At Zhawan nature reserve in Qimen of Huangshan city,Anhui province,six fixed plots were set up in 2011 for the simulated N deposition experiment.Three treatments were designed,CK(no N and/or P additions),N+P(100 kg N hm^(-2)yr^(−1)+50 kg P hm^(-2)yr^(−1))and N(100 kg N hm^(-2)yr^(−1))additions.The changes of soil organic carbon(SOC),total nitrogen(TN),andδ^(13)C andδ^(15)N in 0-10 cm and 10-20 cm soil layers were analyzed.【Result】Sixyear continuous addition of N and P had no significant effect on SOC,TN and C/N ratio(P>0.05).The SOC and TN were ranked as CK>N>N+P treatments,and C/N ratio was in N>CK>N+P treatments.The addition of N and P had no significant effect on soilδ^(13)C andδ^(15)N abundance.The concentrations ofδ^(13)C andδ^(15)N were ordered as N+P>N>CK.The SOC,TN and C/N ratio in the under different treatment were significantly higher in 0-10 cm soil layer than in 10-20 cm soil layer(P<0.001).The concentrations of soilδ^(13)C andδ^(15)N were increased with soil depth except for CK.In N and N+P additions,the soilδ^(13)C concentration were significantly higher in 10-20 cm soil layer than in 0-10 cm soil layer,while in N+P addition,soilδ^(15)N was significantly increased in 10-20 cm soil layer.【Conclusion】The effects of N and P additions on SOC,TN and C/N ratio in subtropical evergreen broad-leaved forest were not significant.The soil stable carbon and nitrogen isotopes were not significantly changed by N and P additions.However,N and P additions significantly increased the abundance ofδ^(13)C andδ^(15)N in the subsoil.It is necessary to further study to reveal the long-term change of soil C and N in combination with soil microorganisms in the future.