Abstract:

Soil enzyme activity plays a crucial role as a key participant in the material cycling and energy flow within soil ecosystems, and the magnitude of its activity distinctly indicates soil nutrient levels and biochemical reaction processes. Freeze-thaw cycling frequently affects northern high-latitude wetlands, resulting in changes in soil enzyme activity along with soil temperature changes. However, the mechanism of spring freeze-thaw effects on soil enzyme activities remains unclear. In order to explore the effects of spring freeze-thaw processes on soil physicochemical properties and soil enzyme activities in riparian wetlands, as well as the relationship between soil physicochemical properties and soil enzyme activities, two typical wetland plant communities, Phragmites australis and Carex appendiculata, which are the most widely distributed plants in riparian of the Xilin River, were selected to analyze the changes and influencing factors of soil urease, sucrase, and catalase activities during the spring freeze-thaw period. The results showed that during the freezing period, the soil enzyme activities in the riparian wetland remained relatively high, and the activities of soil urease and sucrase increased rapidly and then decreased in the freeze-thaw period, and then increased again in the thawing period. However, soil catalase had little response to the freezing-thawing effect. During the freeze-thaw process, the activities of sucrase and catalase in the soil covered by Phragmites australis were significantly higher than those in the Carex appendiculata community, showing significant spatial heterogeneity. Correlation analysis showed that soil urease activity in the riverside wetland during the spring freeze-thaw period was significantly positively correlated with soil temperature, total carbon, and total nitrogen, while soil sucrase was significantly positively correlated with total carbon and total nitrogen. The catalase activity had no significant correlation with soil temperature, but had significant correlation with other physical and chemical factors. Soil enzyme activities are closely related to carbon and nitrogen contents of riparian wetland in different plant communities during freeze-thaw period, and frequent freezing-thawing has important effects on soil enzyme activities and soil material circulation in riverside wetland. In this study, the responses of three soil enzymes to the spring freezing and thawing process and the differences among plant communities were investigated, which provided a theoretical basis for the cycling of carbon and nitrogen in the ecosystem of the riparian wetland.

Key words: riparian wetland, freezing-thawing, soil enzyme activity, plant community, Xilin River, path analysis

摘要：

土壤酶活性是土壤生态系统物质循环和能量流动的重要参与者，其活性大小对土壤养分和生化反应过程有明显指示作用。北方高纬度湿地经常受到冻融作用的影响，由于土壤温度的变化，土壤酶活性会发生变化。然而，春季冻融对土壤酶活性的影响机制仍不清楚。为探讨春季冻融过程对河滨带湿地土壤理化性质和土壤酶活性的影响，以及土壤理化性质与土壤酶活性间的关系，选取锡林河河滨带分布最广泛的芦苇（Phragmites australis）和灰脉苔草（Carex appendiculata）这2种典型湿地植物群落为研究对象，分析春季冻融期间土壤脲酶、蔗糖酶、过氧化氢酶活性的变化及其影响因素。在冻结期，河滨带湿地土壤酶活性均保持较高活性，土壤脲酶和蔗糖酶活性在冻融期均出现迅速增高而后降低的趋势，并在土壤融化期又升高，然而土壤过氧化氢酶对冻融作用的响应较小。在冻融过程中，芦苇覆盖下土壤蔗糖酶和过氧化氢酶活性显著高于灰脉苔草群落且表现出明显的空间异质性。通径分析结果表明，春季冻融期河滨带湿地土壤脲酶活性与土壤温度、总碳、总氮显著正相关，土壤蔗糖酶与总碳、总氮呈显著正相关；过氧化氢酶活性除与土壤温度没有显著相关性，与其他理化因子均有显著相关性。冻融期不同植物群落下土壤酶活性与河滨带湿地碳、氮含量密切相关，频繁的冻融对土壤酶活性以及河滨带湿地土壤物质循环产生重要影响。该研究探讨了3种土壤酶活性对春季冻融过程的响应及在植物群落间的差异，为河滨带湿地生态系统碳、氮等营养物质的循环提供理论依据。

关键词: 河滨带湿地, 冻融交替, 土壤酶活性, 植物群落, 锡林河, 通径分析