蚯蚓与凋落物对杨树人工林土壤酶活性的影响

Effects of earthworms and litterfalls on the soil enzyme activities of poplar plantations

【目的】揭示接种蚯蚓和施用凋落物对杨树人工林土壤主要酶活性的影响,正确评价蚯蚓和凋落物在杨树人工林生态系统土壤养分循环中的作用,以促进其生产力长期维持及生态服务功能提升,为优化杨树人工林经营管理提供依据。【方法】以江苏省东台林场20年生杨树人工林为试验对象,采用随机区组试验设计,共设置杨树凋落叶表施(T1)、杨树凋落叶混施(T2)、接种蚯蚓(T3)、杨树凋落叶表施+接种蚯蚓(T4)、杨树凋落叶混施+接种蚯蚓(T5)共5种不同试验处理及不做处理为对照(CK),测定分析不同处理下土壤蔗糖酶、脲酶、过氧化氢酶及纤维素酶活性的变化,及土壤微生物生物量碳、微生物生物量氮含量、容重、pH、总有机碳含量、全氮含量等重要土壤环境因子的变化。【结果】(1)与CK相比,T3、T4、T5处理显著提升了土壤蔗糖酶、脲酶活性,土壤蔗糖酶活性平均增幅分别为30.85%、34.58%、50.90%,土壤脲酶活性平均增幅分别为27.57%、33.67%、66.64%。(2)与CK相比,5种处理均显著提升了土壤纤维素酶活性,平均增幅分别为38.39%、51.79%、79.91%、129.33%、149.52%。(3)与CK相比,T1、T2处理显著降低了土壤过氧化氢酶活性,平均降幅分别为13.23%、17.56%,T3、T4、T5处理与CK相比没有显著性差异。(4)季节动态分析表明,土壤蔗糖酶活性9月最高,为0.77 mg/(g·d);3月最低,为0.40 mg/(g·d)。土壤脲酶活性夏秋季较高,为10.57 mg/(g·d);冬春季较低,为5.61 mg/(g·d)。土壤过氧化氢酶活性6月最高,为4.20 mg/(g·h);其他季节较低,为2.22 mg/(g·h)。土壤纤维素酶活性夏秋季较高,为6.93 mg/(g·d);冬春季较低,为2.36 mg/(g·d)。与CK相比,接种蚯蚓及添加凋落物处理没有改变4种土壤酶活性的季节性变化规律。(5)重复测量方差分析表明,季节变化和试验处理均显著影响了土壤蔗糖酶、脲酶、纤维素酶和过氧化氢酶活性,其中季节变化和试验处理对土壤过氧化氢酶活性的影响具有显著性交互作用,而对土壤蔗糖酶、脲酶和纤维素酶活性的影响没有显著性交互作用。(6)相关分析表明,土壤蔗糖酶、脲酶及纤维素酶活性与土壤容重、pH呈显著负相关,与土壤全氮、总有机碳、微生物生物量碳、微生物生物量氮含量、微生物生物量碳氮比呈显著正相关;土壤过氧化氢酶活性则与上述各环境因子相关性不显著。【结论】接种蚯蚓能够显著提高杨树人工林土壤蔗糖酶、脲酶和纤维素酶活性,凋落物混施比表施更有利于促进接种蚯蚓对杨树人工林土壤蔗糖酶、脲酶和纤维素酶活性的影响;凋落物混施和接种蚯蚓处理均显著提升了土壤酶评价指数,凋落物混施+接种蚯蚓处理进一步提升了土壤酶指数。因此,在农林业生产中可考虑将凋落物混施与接种蚯蚓经营措施结合应用。

【Objective】We aimed to reveal the effects of the earthworm inoculation and litterfall addition on the soil enzyme activities of poplar plantations to provide a scientific basis for accurately evaluating the role of earthworms and litterfalls on the soil nutrient cycling in a poplar plantation ecosystem and optimizing the management of poplar plantations to promote their long-term productivity, maintenance and ecological service functional improvement.【Method】A poplar plantation was chosen as the study site in Dongtai Forest Farm of Yancheng City, Jiangsu Province. We used a randomized block design with five different experimental treatments as well as a control(CK). Specifically, the treatments were poplar leaf litter mulch on the soil(T1), the poplar leaf litter incorporation into the soil(T2), earthworm inoculation(T3), poplar leaf litter mulch on the soil with earthworm inoculation(T4) and poplar leaf litter incorporation into the soil with earthworm inoculation(T5). The enzyme activities of invertase, urease, catalase and cellulase in different treatments were determined. Additionally, changes in soil microbial biomass carbon, soil microbial biomass nitrogen content, soil bulk density, soil pH value, soil total organic carbon, soil total nitrogen content and other important soil environmental factors were also analyzed.【Result】(1)Compared with CK, treatments T3, T4 and T5 signi-ficantly increased the soil invertase activity and the soil urease activity, and the average increases in the soil invertase activity were 30.85%, 34.58% and 50.90%, respectively;the average increases in soil urease activity were 27.57%, 33.67% and 66.64%, respectively.(2)Compared with CK, all five treatments significantly increased soil cellulase activities, with an average increase of 38.39% in T1, 51.79% in T2, 79.91% in T3, 129.33% in T4, and 149.52% in T5.(3)Compared with CK, T1 and T2 treatments significantly reduced the soil catalase activity, with average decreases of 13.23% and 17.56%, respectively. T3, T4 and T5 treatments showed no significant difference compared with CK.(4)The seasonal dynamic analysis showed that the soil sucrase activity was the highest in September and the lowest in March, with a minimum value of 0.40 mg/(g·d) and a maximum value of 0.77 mg/(g·d). The soil urease activity was higher in summer and autumn, and lower in spring and winter, with a minimum value of 5.61 mg/(g·d) and a maximum value of 10.57 mg/(g·d). The soil catalase activity was highest in June and lower in other seasons, with a minimum value of 2.22 mg/(g·h) and a maximum value of 4.20 mg/(g·h). The activity of cellulase was higher in summer and autumn and lower in spring and winter, with a minimum value of 2.36 mg/(g·d) and a maximum value of 6.93 mg/(g·d). Compared with CK, the earthworm inoculation and litterfall addition treatments did not change the seasonal variation patterns of the four soil enzymes.(5)The repeated ANOVA measures showed that seasonal changes and treatments significantly affected soil invertase, urease, cellulase and catalase activities, which only had significant interactions on the soil catalase activity, but no significant interaction on soil invertase, urease and cellulase activities.(6)The correlation analysis showed that soil invertase, urease and cellulase activities were negatively correlated with the soil bulk density and pH value, and positively correlated with soil total nitrogen, soil total organic carbon, soil microbial biomass carbon, soil microbial biomass nitrogen content and soil microbial biomass C/N ratio. The soil catalase activity was not significantly correlated with the above soil environmental factors.【Conclusion】Soil enzyme activities of invertase, urease and cellulase in a poplar plantation could be significantly improved by the earthworm inoculation, and the effects of earthworm inoculation on soil enzyme activities of invertase, urease and cellulase could be further promoted by the poplar leaf litter incorporation into the soil than by mulch on the soil. The poplar leaf litter incorporation into the soil and earthworm inoculation treatments both significantly improved the soil enzymes indexes, while the litter incorporation into the soil with earthworm inoculation treatments further significantly improved the soil enzymes indexes. Therefore, the combination management measures of the litter incorporation into the soil and earthworm inoculation are recommended in agricultural and forestry production.