三江平原湿地不同土地利用方式对土壤养分及酶活性的影响

以中国科学院三江平原湿地生态试验站为对象，研究了不同利用方式（湿地草甸、旱田系统、退耕成草、退耕成林）对土壤酶活性分布特征及相关因子的影响。结果表明:土壤利用方式不同，土壤酶活性（转化酶、脲酶、磷酸酶和过氧化氢酶）、有机碳含量和土壤养分含量有较大差异。土壤有机碳、全氮、全钾、速效磷、碱解氮、微生物量碳和氮均呈现出一致的变化规律，依次表现为湿地草甸 > 退耕草地 > 退耕林地 > 旱田系统，也即由湿地草甸退化过程中，土壤养分含量逐渐降低，其中不同土地利用方式下土壤全磷含量差异不显著（p>0.05），在湿地的退化过程中，土壤全磷并没有发生显著的变化。与湿地草甸相比，土壤蔗糖酶、脱氢酶、脲酶和酸性磷酸酶活性均显著降低，其活性分别降低了32.69%，36.71%，50.00%，44.28%，由旱田系统恢复为湿地草甸系统后，土壤各种酶活性均显著增加，其中土壤蔗糖酶、脱氢酶、脲酶和酸性磷酸酶活性分别比旱田系统增加了26.68%，31.51%，48.19%，43.84%；表明由湿地草甸开垦为耕地和由耕地恢复为湿地草甸和林地，发生着两种不同的生物学过程，前者为微生物降解过程，而后者则为微生物累积过程。相关性分析表明SOC，TN和SMBC对土壤蔗糖酶、脱氢酶、脲酶和酸性磷酸酶活性的贡献为正，对土壤酶活性起到主导作用。主成分分析表明影响土壤酶活性最主要的因子为SOC，TN和SMBC。

Characteristics of Soil Nutrients and Enzyme Activity Under Different Types of Land Use in Wetland of Sanjiang Plain

The wetlands in the Sanjiang Ecology Station of Chinese Academy of Sciences were selected as the study sites, the characteristics of soil enzyme activities and nutrients under different types of land use, including wetland ecosystem, dryland ecosystem, conversion of dryland to wetland, conversion of dryland to forestland, were investigated. The results showed that there was a great significance difference in soil enzyme activities (invertase, urease, phosphatase and catalase) and soil nutrients. Soil organic carbon, total nitrogen, total potassium, available phosphorus, alkali-hydrolyzed nitrogen, microbial biomass carbon and nitrogen showed the same change trend among these land use types, which decreased in the order: wetland ecosystem > conversion from dryland to wetland > conversion from dryland to forestland > dryland ecosystem. When the reclaimed dryland was recovered to wetland, soil nutrients gradually decreased, while there was no significantly difference in total phosphorus (p>0.05). Compare to wetland ecosystem, invertase, urease, phosphatase, and catalase decreased by 32.69%, 36.71%, 50.00% and 44.28%, respectively. However, after the dryland ecosystem was converted to wetland ecosystem, soil enzyme activities increased, and invertase, urease, phosphatase, and catalase increased by 26.68%, 31.51%, 48.19% and 43.84%, respectively, suggesting that there were two different biological processes, one was the microbial degradation process after the dryland ecosystem was converted to wetland ecosystem, the other was the microbial accumulation process after the wetland ecosystem was converted to dryland ecosystem. Correlation analysis showed that soil organic carbon, soil total nitrogen and soil microbial biomass carbon had the negative correlation with soil enzyme activities. Principal component analysis showed that soil organic carbon, soil total nitrogen and soil microbial biomass carbon were the main driving factors on soil enzyme activities in wetlands of Sanjiang Plain.