连栽杉木人工林参与土壤碳氮转化过程酶活性及其与土壤理化因子的相关性

Soil carbon and nitrogen transformed enzyme activities in continuously cultivated Chinese fir (Cunninghamia lanceolate) plantations and their correlations with soil physicochemical factors

选取福建三明不同连栽代数杉木人工林(一代、二代、三代)及格氏栲天然林为研究对象,运用冗余分析法研究不同林地土壤理化性质、养分含量与参与碳,氮转化过程酶活性之间的相互关系,以探究中亚热带连栽杉木人工林土壤酶的季节变化及其影响因素,为揭示杉木人工林养分循环特点和林地土壤质量评价提供依据。结果表明:连栽杉木人工林地土壤pH显著低于天然林,但一、二、三代杉木林间无显著差异。12月份土壤全碳、全氮含量在不同连栽代数杉木林中无显著差异,并且二代和三代林土壤全碳、全氮含量均显著高于天然林(P<0.05);6月份杉木三代林土壤全碳含量显著高于一代林(P<0.05),但与二代林和天然林无显著差异。12月份土壤铵态氮和硝态氮含量在一、二、三代杉木林间无显著差异。6月份杉木一代林土壤硝态氮含量显著高于二代林和天然林(P<0.05),但与三代林无显著差异。12月份天然林土壤脲酶活性显著高于连栽杉木人工林(P<0.05),而一、二、三代杉木林土壤脲酶活性无显著差异;杉木一代、二代林和天然林土壤天冬酰胺酶活性无显著差异,均显著高于三代林(P<0.05)。冗余分析表明,土壤含水量、NO-3⁃N含量和pH对酶活性的影响较大,它们与土壤天冬酰胺酶、β⁃葡萄糖苷酶(BG)、和蛋白酶(protease)呈显著正相关,但与土壤N⁃乙酰氨基葡萄糖苷酶(NAG)呈显著负相关。本研究说明杉木林进入成熟林-过熟林阶段后,不同连栽代数林地许多土壤理化指标及酶活性均有不同程度恢复,而且它们受季节因素影响很大,建议今后加强土壤酶活性对环境变化响应的长期综合监测。

This study aims to investigate the seasonal changes of soil carbon and nitrogen⁃transformed enzyme activities and their driving factors in successive rotations of subtropical Chinese Fir(Cunninghamia lanceolate)plantation.The results would provide basis for assessing nutrient cycling and soil quality in forest.Through canonical redundancy analysis(RDA)the relationships between soil physical properties,nutrient conditions,and enzyme activities were analyzed in different generations of Chinese fir plantation(FRP,SRP,TRP)and Castanopsis Kawakamii forest(NF)in Fujian province,China.A significant decrease of soil pH was observed in Chinese fir plantation compared with NF,but no significant changes were found between FRP,SRP,and TRP.In December,there was no significant difference on soil total carbon and nitrogen among different generations of Chinese fir plantation,and the SRP and TRP were significantly higher than the NF(P<0.05).In June,soil total carbon of TRP was significantly higher than that of FRP(P<0.05),but not significantly different from that of SRP and NF.In December,there was no significant difference on soil NH+4⁃N and NO-3⁃N among different generations of Chinese fir plantation.In June,soil NO-3⁃N of FRP was significantly higher than that of SRP and NF(P<0.05),but not different from that of TRP.Soil urease activity of NF was significantly higher than that of FRP,SRP,and TRP,but no significant difference was found among FRP,SRP,and TRP in December.Soil asparaginase activity of FRP,SRP,and NF were significantly higher than that of TRP(P<0.05),but no significant difference was found among FRP,SRP,and NF.The RDA showed that soil moisture,NO-3⁃N,and pH made significant contributions to variations of soil enzyme activities,especially positively related to the activities of soil asparaginase,β⁃glucosidase(BG),and protease,but negatively related to soil N⁃acetyl⁃β⁃D⁃glucosaminidase(NAG).The soil physiochemical properties and enzyme activities in mature and over⁃mature Chinese fir plantations recovered to different degrees compared with the natural forest,and their variations were largely influenced by the seasonal changes.Additionally,a long⁃term observation on soil enzyme activities in response to the environmental changes is recommended.