农业耕作和外来植物入侵对金沙江下游库区新生消落带土壤养分和酶活性的影响

Effects of Agricultural Farming and Alien Plants Invasion on Soil Nutrients and Enzymes in New Water Level Fluctuation Zone in Reservoirs of the Lower Jinsha River

金沙江下游梯级水电站新生消落带上农业耕作较为普遍,同时广泛存在外来植物入侵,这可能会对其土壤养分状况产生潜在影响。基于此,以乌东德电站库区新生消落带为研究区域,以淹水后自然形成的狗牙根(Cynodon dactylon)群落为对照,选择典型农作物玉米(Zea mays)与入侵植物银胶菊(Parthenium hysterophorus)为研究对象,通过比较不同群落下0~10 cm和10~20 cm深度土壤养分含量及酶活性差异,探讨农业耕作和外来植物入侵对消落带土壤养分状况的影响。结果表明:①玉米和银胶菊群落下0~10 cm土层有机质、全氮、全磷、速效钾含量显著高于狗牙根群落(P<0.05),增幅为24.58%~136.98%;10~20 cm土层的有机质、氮磷钾养分全量和速效养分含量也较狗牙根群落显著高出16.67%~141.68%(P<0.05)。②相较狗牙根群落,玉米和银胶菊群落下0~10 cm和10~20 cm土层的脲酶、蔗糖酶、碱性磷酸酶、硝酸还原酶活性均显著增加(P<0.05),增幅为5.60%~378.65%。3个群落中,银胶菊群落土壤酶指数最高,较狗牙根群落显著高出23.49%(P<0.05)。③消落带土壤有机质、全氮、全磷、碱解氮、有效磷、速效钾含量均与脲酶、蔗糖酶、硝酸还原酶、碱性磷酸酶活性之间呈显著正相关(P<0.05),表明上述酶活性可作为消落带土壤养分状况变化的有效表征。总的来看,农耕活动和银胶菊入侵促进了落干期金沙江下游新生消落带土壤养分的积累和有效性的增加。因此,应加强消落带农业耕作的管控并尽快开展入侵植物防治,以减少淹水期消落带土壤养分流失风险。

The completion and operation of cascade hydropower station in the lower region of the Jinsha River have led to the emergence of numerous newborn water-level-fluctuating zones(NWLFZ)in the reservoir area.Agricultural activities are more common in the NWLFZ,and alien plants often invade the area and may affect soil nutrient status.Therefore,the Wudongde NWLFZ is selected as the study area.The typical agricultural crop maize(Zea mays)and the invasive plant species Parthenium hysterophorus were selected as the research objects,and the naturally formed Cynodon dactylon community after flooding was selected as the control.The impact of agricultural activities and invasive plants on soil conditions was investigated by comparing the differences in soil nutrient contents and enzyme activities in the 0-20 cm soils.The results showed that the contents of organic matter,total nitrogen,total phosphorus,and available potassium in the 0-10 cm soil layer were significantly higher than those in C.dactylon community,ranging from 24.58%to 136.98%(P<0.05).Similar increases were observed in the 10-20 cm soil layer.On the other hand,the activities of urease,sucrase,alkaline phosphatase and nitrate reductase in the 0-20 cm soil layers of maize and P.hysterophorus communities increased significantly(P<0.05),with an increase ranging from 5.60%to 378.65%.Among the three communities,the soil enzyme index of P.hysterophorus community was significantly higher(P<0.05)than that of the C.dactylon community by 23.49%.Correlation analysis indicated that the activities of urease,sucrase,nitrate reductase,and alkaline phosphatase were positively correlated with the contents of soil organic matter,total nitrogen,total phosphorus,alkali-hydrolyzed nitrogen,available phosphorus,and available potassium(P<0.05).This suggests that the enzyme activities could be effectively used to represent changes in soil nutrient status in the NWLFZ.Agricultural cultivation and P.hysterophorus invasion promoted the accumulation and availability of soil nutrients in the NWLFZ of the lower Jinsha River.Therefore,the control of agricultural cultivation should be strengthened.Additionally,the control of invasive plants should be initiated promptly to reduce the risk of soil nutrient loss in the NWLFZ during the flooding period.In the follow-up work,the soil physical structure,aggregate composition,and microbial community composition should also be studied to fully understand the comprehensive effects of different land use types and plant communities on soil conditions in the NWLFZ in the lower region of the Jinsha River.