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不同恢复年限下洪泽湖湿地沉积物胞外酶活性变化

Variations in extracellular enzyme activities in sediments of wetlands with different restoration durations in Hongze Lake

  • 摘要: 湿地沉积物胞外酶与湿地沉积物中的碳、氮、磷等营养元素循环以及环境质量密切相关。为了探究不同恢复年限湿地沉积物胞外酶活性的变化及其影响因素,2023年7月选取江苏泗洪洪泽湖湿地国家级自然保护区不同恢复年限(0 a、2 a、3 a、5 a、10 a)的自然恢复湿地,通过野外采样并结合室内分析,利用荧光测定技术及常规化学分析方法,分析沉积物胞外酶活性及沉积物的理化性质。研究结果表明,与退化湿地(恢复0 a)相比,3 a及3 a以下恢复区0~10 cm深度沉积物中与碳、氮、磷循环相关的胞外酶活性变化不大,3 a以上恢复区其沉积物胞外酶活性显著增加(n=3,p<0.05)。3 a及3 a以上自然恢复湿地,随着湿地恢复年限增加,沉积物中与碳循环相关的纤维二糖水解酶(CBH)、β-1, 4-木糖苷酶(βX)和β-葡萄糖苷酶(βG)以及与磷循环相关的磷酸酶(PHOS)活性均增加;与氮循环相关的N-乙酰-β-D-氨基葡萄糖苷酶(NAG)活性也增加,但是亮氨酸氨基肽酶(LAP)活性在5 a与10 a恢复区中差异不大。沉积物胞外酶(除PHOS外)活性均随着深度增加而降低,且在0~10 cm深度显著高于其他深度(n=3,p<0.05)。相关分析结果表明,在3 a及3 a以上自然恢复区,沉积物胞外酶活性与沉积物有机质、全氮、全磷、速效磷含量和pH显著相关,但是在10 a自然恢复区,PHOS活性与沉积物中有机质、全氮、全磷、速效磷含量无显著相关性。由此可见,湿地恢复过程中,沉积物酶活性增加以及有机质和全氮含量的增加,有助于提高沉积物碳库及氮库。

     

    Abstract: Extracellular enzymes are essential for mediating the biogeochemicalcycling of carbon, nitrogen, and phosphorus in wetland sediments, influencing nutrient dynamics and environmental quality. To explore the variations in extracellular enzyme activity in sediments of naturally restored wetlands across different restoration periods and to identify the driving factors, this study was conducted in the Hongze Lake Wetland National Nature Reserve. Sediment samples were collected from wetlands with varying restoration durations (0, 2, 3, 5, and 10 years since restoration). Enzyme activities were measured by fluorescence measurement technology, and sediment chemical properties were analyzed using conventional chemical methods. The results showed that in wetlands restored for 3 years or longer (≥3a), extracellular enzyme activity in the 0-10 cm sediment layer significantly increased compared to degraded wetlands (0 years of restoration, 0 a). In contrast, enzyme activity in sediments of wetland restored for less than 3 years (<3 a) remained relatively unchanged. Additionally, in wetlands restored for 3 years or longer (≥3a), enzymes activities (except for phosphatase) were significantly higher in the surface sediment layer (0-10 cm)than in deeper layers (>10-20 cm and >20-30 cm). Furthermore, enzyme activity in deeper sediments exhibited a lagged response to restoration duration, indicating that surface sediments are more sensitive to restoration-induced changes. During natural restoration of 3 years or longer, the organic matter and total nitrogen content in sediments increased progressively, Correspondingly, enzymes involved in carbon cycling such as cellobiohydrolase (CBH), β-1,4-xylanase (βX) and β-Glucosidase (βG), and phosphatase involved in phosphorus cycling (PHOS), showed increasing trends with restoration time. Among nitrogen (N)-cycling enzymes, N-acetyl-β-D-glucosaminidase (NAG) activity increased, while leucine aminopeptidase (LAP) activity remained stable between 5 and 10 years of restoration. Except for phosphatase, all measured enzymes exhibited higher activity in surface sediments (0-10 cm) compared to deeper layers, highlighting the stratification of microbial and enzymatic processes in sediment profiles. Correlation analysis revealed that in wetlands restored for 3 years or longer, the activities of carbon- and nitrogen-transforming enzyme (CBH, βX, βG, NAG, and LAP) were significantly correlated with sediment properties, including organic matter, total nitrogen, total phosphorus, available phosphorus, and pH. However, in wetlands restored for 10 years, phosphatase activity showed no significant correlation with organic matter, total nitrogen, total phosphorus, or available phosphorus, suggesting that phosphorus cycling may become less dependent on sediment nutrient status in long-term restored wetlands. These findings indicate that wetland restoration enhances sediment enzyme activity and promotes the accumulation of organic matter and total nitrogen, thereby facilitating carbon and nitrogen sequestration in sediments.

     

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