外源性氮和磷对火力楠和马尾松混合凋落叶分解的影响

Effects of external N and P on decomposition of mixed leaf litters of Michelia macclurei and Pinus massoniana woodlands

【目的】研究外源性N和P对火力楠Michelia macclurei和马尾松Pinus massoniana凋落叶分解速率的影响,以及分解过程中的N、P、K含量变化,了解混合凋落叶分解对外源性N和P的响应机制,为森林资源管理提供参考。【方法】将火力楠和马尾松混合凋落叶置于火力楠林地及马尾松林地,分别设立4块5 m×5 m的小样方,喷施N、P和N+P,比较其分解速率及分解过程中的N、P、K含量变化。【结果】在2种林地的不同处理下,24个月后,火力楠林地混合凋落叶残留量为施N(4.99 g)>对照(4.14 g)>施N+P(2.17 g)>施P(1.16 g),马尾松林地混合凋落叶残留量为施N(2.72 g)>对照(1.21 g)>施N+P(0.36 g)>施P(0.16 g),施N对火力楠和马尾松林下的混合凋落叶的分解有抑制作用;施P后两者的混合凋落叶的分解速率均不同程度地有所加快;施N+P后两者的混合凋落叶的分解速率也均加快,但慢于施P处理。马尾松林下混合凋落叶残留量均小于火力楠林下混合凋落叶残留量。分解24个月后,火力楠林地施N、P和N+P的混合凋落叶N质量分数分别为13.72、12.34和13.70 g·kg^(–1),而马尾松林地分别为12.63、13.46和14.54 g·kg^(–1),均显著大于其凋落叶的初始N质量分数(9.90 g·kg^(–1));施P和N+P处理的火力楠林地混合凋落叶P质量分数由初始的0.38 g·kg^(–1)分别增至0.86和0.74 g·kg^(–1),而马尾松林地混合凋落叶P质量分数由初始的0.38 g·kg^(–1)分别增至1.37和1.05 g·kg^(–1)。凋落叶K含量的变化无规律。【结论】火力楠和马尾松混交可促进火力楠凋落叶分解,提高混合凋落叶的分解速率。

【Objective】To investigate the effects of external nitrogen(N)and phosphorus(P)on decomposition rate of mixed leaf litters of Michelia macclurei and Pinus massoniana woodlands,and analyze changes in N,P and potassium(K)contents during deposition process,in order to understand the response mechanism of leaf litter decomposition to external N and P,and provide reference for forest resource management.【Method】Mixed leaf litters of M.macclurei and P.massoniana were placed in woodlands of M.macclurei and P.massoniana.Four5m×5m plots were set in each wood land and were sprayed with N,P or N+P.The decomposition rates and changes in N,P,K contents of leaf litters were compared.【Result】Twenty-four months after treatments,the amounts of leaf litter residue were N addition(4.99g)>control(4.14g)>N+P addition(2.17g)>Paddition(1.16g)in M.macclurei woodland,and N addition(2.72g)>control(1.21g)>N+P addition(0.36g)>P addition(0.16g)in P.massoniana woodland.N addition inhibited decomposition of mixed leaf litters under M.macclurei and P.massoniana woodlands,whereas P and N+P additions both accelerated decomposition of mixed leaf litters with a faster decomposition rate compared to N+P addition.The amounts of leaf litter residue in P.massoniana woodland were less than those in M.macclurei woodland.Twenty-four months after treatments,N contents of mixed leaf litters treated with N,P and N+P additions were13.72,12.34and13.70g·kg–1respectively in M.macclurei woodland,and12.63,13.46,and14.54g·kg–1respectively in P.massoniana woodland,Which were greater than the initial N content of mixed leaf litters(9.90g·kg–1).The P content of mixed leaf litters treated with P and N+P additions increased from the initial value of0.38to0.86and0.74g·kg–1respectively in M.macclurei woodland,and increased from0.38to1.37and1.05g·kg–1respectively in P.massoniana woodland.K contents of mixed leaf litters changed irregularly.【Conclusion】Decomposition of M.macclurei leaf litter can be accelerated and decomposition rate of mixed leaf litters can be enhanced by mixed-planting M.macclurei and P.massoniana.