杉阔异龄复层林对土壤团聚体稳定性和有机碳及养分储量的影响

Effects of Uneven-aged Cunninghamia lanceolata and Evergreen Broadleaved Mixed Plantations on Soil Aggregate Stability and Soil Organic Carbon and Nutrients Stocks

[目的]研究杉木纯林转化为杉木阔叶树异龄复层混交林(简称杉阔复层林)对土壤团聚体稳定性和有机碳及养分储量的影响,为杉木人工林结构优化调控和可持续发展提供理论依据。[方法]以浙江开化不同树种构建的杉阔复层林和杉木纯林为研究对象,分析0~20 cm土层水稳性团聚体(WSA)稳定性以及全土和团聚体有机碳(SOC)、总氮(TN)、总磷(TP)和镁(Mg)储量的变化。[结果](1)杉阔复层林和杉木纯林<0.25 mm水稳性团聚体(WSA<0.25 mm)占比最高;与杉木纯林相比,复层林均显著增加>5 mm水稳性团聚体(WSA>5 mm)比例,同时也显著提高土壤平均质量直径(MWD)和几何平均直径(GMD),降低了团聚体分形维数(D)。(2)杉阔复层林和杉木纯林不同粒级团聚体中SOC和TN储量变化趋势一致,均为WSA>5 mm、2~5 mm粒径水稳性团聚体(WSA2~5 mm)>0.25~2 mm粒径水稳性团聚体(WSA0.25~2 mm)>WSA<0.25 mm,而不同粒级团聚体中TP和Mg储量差异较小。(3)全土和团聚体有机碳及养分储量主要受>5 mm粒径团聚体有机碳(SOCA>5 mm)、2~5 mm粒径团聚体总氮(TNA2~5 mm)含量以及土壤pH的影响;团聚体稳定性主要受WSA>5 mm、土壤pH以及2~5 mm粒径团聚体有机碳(SOCA2~5 mm)含量的影响。(4)复层林不同伴生树种对团聚体组分、稳定性、土壤有机碳及养分储量有重要影响,主成分分析(PCA)发现,杉木纯林引入紫楠(杉木+紫楠)后显著影响全土和团聚体磷镁储量以及MWD和GMD;杉木纯林引入红茴香(杉木+红茴香)后显著影响全土和团聚体碳氮储量。[结论]杉阔异龄复层林的构建有利于改善杉木纯林土壤理化性质,尤以乔木阔叶树种紫楠和红茴香引入,对杉木纯林土壤团聚体稳定性和有机碳及养分储量的改善效果更佳。

[Objective]To study the effect of uneven-aged mixed plantations(Cunninghamia lanceolata+evergreen broadleaved tree species)on soil aggregates stability,organic carbon and nutrient storage,so as to provide references for optimizing the plantation structure and improving the sustainable forest management.[Method]This study investigated the uneven-aged mixed and the monoculture C.lanceolata plantations in Kaihua County of Zhejiang Province,and analyzed the stability of water-stable aggregates(WSA)and the changes of soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP)and magnesium(Mg)stocks in 0~20 cm soil layer.[Result](1)The proportion of water-stable micro-aggregates(size<0.25 mm,WSA<0.25 mm)was the highest in the uneven-aged mixed and monoculture plantations.Compared with the monoculture plantation,the>5 mm aggregates proportions(WSA>5 mm),the soil mean weight diameter(MWD)and geometric mean diameter(GMD)significantly increased in the unevenaged mixed plantations,but the soil fractal dimension(D)reduced.(2)The changes of SOC and TN stocks in different aggregate size of the uneven-aged mixed and the monoculture plantations were similar:WSA>5 mm,WSA2~5 mm>WSA0.25~2 mm>WSA<0.25 mm.The stocks of TP and Mg less varied in different aggregate sizes.(3)The stability of aggregate was mainly affected by WSA>5 mm and SOC>5 mm contents,pH,SOC2~5 m.bulk soil and soil aggregates organic carbon and nutrient stocks were mainly affected by SOCA>5 mm,2~5 mm nitrogen contents(TNA2~5 mm)and pH.(4)Tree species composition in the uneven-aged mixed plantations greatly affected on aggregate composition and stability,SOC and nutrient stocks.The results of principal component analysis(PCA)showed that C.lanceolata+Phoebe sheareri significantly affected TP and Mg stocks in bulk soil and soil aggregates,and also affected MWD and GMD;C.lanceolata+Illicium henryi significantly affected SOC and TN stocks in bulk soil and soil aggregates.[Conclusion]In general,the establishment of uneven-aged C.lanceolata and broadleaved evergreen mixed plantations is beneficial to improve the soil physical and chemical properties of monoculture plantation,especially the introduced tree species of Ph.sheareri and I.henryi greatly enhance soil aggregate stability,soil organic carbon stocks and nutrient stocks of monoculture plantations.