凋落物添加对不同龄级杉木林土壤养分与微生物特性的影响

Effects of litter additions on the soil nutrients and microbial properties in Cunninghamia lanceolata plantations of different stand ages

【目的】探讨并分析不同树种凋落物组合添加对各龄级杉木林土壤养分以及对土壤微生物特性的影响,为南方杉木纯林营造混交林提供理论依据。【方法】以江西分宜不同龄级杉木人工林为研究对象,设置不同树种凋落物组合添加处理,研究其在杉木不同发育阶段对土壤有机碳(SOC)、氮(N)、磷(P)养分及其化学计量比,以及对土壤微生物生物量碳(MBC)、生物量氮(MBN)、生物量磷(MBP)的影响。【结果】无论添加何种凋落物都能显著提高土壤有机碳和土壤全氮,但添加不同类型凋落物的提升效果存在明显差异。混合凋落物添加组和近熟林协同效应表现最优,相较于对照组其土壤有机碳及土壤全磷分别提升36.8%及69.1%,同时混合凋落物添加组与幼龄林协同效应也表现较好,相较于对照组土壤全氮提升了40.4%,阔叶树种凋落物添加组与幼龄林协同效应显著提高了土壤的N︰P,表明阔叶树种凋落物的输入显著改善了林地土壤中的养分比例。混合凋落物添加组处理的幼龄林土壤显著提高了MBN及MBP(分别提升了23.4%和23.9%),在近熟林中显著提升土壤MBN(提升了12.9%),而在幼龄林中显著降低了土壤MBN/MBP,微生物磷限制的情况得到缓解。相关性分析显示,土壤微生物生物量特性与土壤养分之间关系紧密。土壤微生物生物量碳、生物量氮及微生物量磷均与土壤中有效养分呈正相关,与土壤碳氮磷计量比呈负相关。【结论】在杉木人工林中可以通过引种阔叶树种方式来改善地力。在杉木纯林中引种阔叶树种或营造混交林,不仅能增加杉木林地凋落物量,还能输入阔叶树种凋落物,使林地表层凋落物分解和土壤微生物活动加速,进一步加快土壤碳氮磷循环。

【Objective】This work has explored the effects of different litter combinations from various tree species on soil nutrients and microbial characteristics in Chinese fir forests of different ages,in order to provide a theoretical basis for the establishment of mixed forests from pure Chinese fir(Cunninghamia lanceolata)forests in the subtropical region of China.【Method】In this study,the influence of different types of litter additions and stand age on soil nutrients and microbial biomass properties in C.lanceolata plantations was investigated.We measured soil microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),microbial biomass phosphorus(MBP),soil organic carbon(SOC),N and P concentrations in the C.lanceolata plantations of different stand ages in Fenyi,Jiangxi Province.【Result】The results showed litter additions could significantly improve soil organic carbon and total nitrogen,but there were obvious differences in the effect of different types of litter additions.The mixed litter addition group showed the best performance and that was more obvious in the pre-mature plantation compared with the control group.The soil organic carbon and total phosphorus increased by 36.8%and 69.1%respectively in the mixed litter addition group.At the same time,the synergistic effect of the mixed litter addition treatment and young forests was also significant.The soil total nitrogen increased by 40.4%compared with the control treatment.The synergistic effect of litter additions of broad-leaved tree species and young forests significantly increased soil N:P,indicating that broad-leaved litter additions significantly improved the proportion of soil nutrients.When mixed litters were added to the young plantation,MBN and MBP were significantly increased by 23.4%and 23.9%.When broad-leaved litters were added to the pre-mature plantation,MBC was significantly increased by 12.9%.However,MBN/MBP was significantly reduced when broad-leaved litters were used in the young forest,while the phosphorus limitation was alleviated.Correlation analysis showed that there was a strong correlation between soil microbial biomass characteristics and soil nutrients,while MBC,MBN and MBP were positively correlated with available nutrients in the soil,and negatively correlated with soil carbon,nitrogen,and phosphorus ratios.【Conclusion】Therefore,the introduction of broad-leaved tree species can improve soil fertility in C.lanceolata plantations.The introduction of broad-leaved tree species into a pure stand or the construction of mixed forests can not only increase the amount of litter,but also import the litter of broad-leaved tree species,which can promote litter decomposition and soil microbial activities,and further accelerate the cycle of soil carbon,nitrogen and phosphorus.