【摘要】 【目的】分析三峡库区消落带经历长期水库水位变化后的土壤化学性质,为揭示消落带水文环境变化提供科学依据。【方法】在秭归段消落带回水区选择典型次生灌丛固定监测样地,根据库区水位运行计划,于2008、2009、2012、2014和2015年(分别经历0、1、4、6和7次水位涨落)对不同海拔(145～155、155～165、165～175、175～185 m)样地的不同土层(0～10和10～20 cm)土壤的pH值和有机质及碱解氮、速效磷和速效钾含量进行测定。【结果】经历7次水位涨落后,所有海拔的pH值均明显增加,其中海拔145～155 m土壤由酸性(pH6. 1)变为碱性(pH8. 2),而其他海拔土壤逐渐由酸性趋于中性;水淹海拔区土壤有机质含量高于非水淹对照海拔(175～185 m),且随水淹时间增加,0～10 cm土层有机质含量较2008年呈逐年下降趋势,而10～20 cm土层则先增加后降低;随水位涨落周期的增加,土壤碱解氮含量呈波动性下降趋势,且0～10 cm土层土壤对水淹影响更为敏感,0～10 cm土层碱解氮以2009年和2015年下降最为显著(P<0. 05),和2008年相比各海拔降幅分别达37. 2%～54. 7%和50. 6%～65. 7%; 0～10 cm土层速效钾含量在2009年降幅最大,达17. 1%～50. 8%;速效磷含量则呈逐年下降趋势,且在速效养分中的流失量最大,在经历4、6和7次水位涨落后,速效磷含量较2008年分别下降78. 0%、94. 8%、91. 6%(0～10 cm)和89. 5%、93. 6、92. 5%(10～20 cm)。【结论】随三峡水库运行周期的不断延长,消落带土壤pH值升高、有机质含量下降,消落带土壤养分匮乏现象将突显,对于消落带经历长期水位涨落后的土壤化学性质变化仍需长期监督。更多还原

【Abstract】 【Objective】Chemical properties of soils at different altitudes and layers after long-term reservoir water level changes were analyzed to understand the degree of variation of soil environment after years of drastic changes in dry-wet alternation in the fluctuation zone of the Three Gorges Reservoir.【Method】Sample plots were set up in a secondary shrub forest within the typical hydro-fluctuation belt in the Three Gorges Reservoir. According to the water level operation plan of the reservoir area,the pH-value,organic matter,and contents of available N,available P and available K in the soil at different altitudes(145-155,155-165,165-175,and 175-185 m) in different soil layers(0-10 and 10-20 cm) were measured in 2008,2009,2012,2014,and 2015(that is,through 0,1,4,6,and 7 fluctuations of water level,respectively).【Results】Results showed that soil pH-values at all altitudes increased obviously,the pH value at 145-155 m changed from acid(pH6.1) to alkaline(pH8.2),and the pH-values at other altitudes gradually tended to be neutral after 7 fluctuations of water level. The extent of pH variation at different altitudes was: 145-155 m > 155-165 m > 165-175 m > 175-185 m. The content of soil organic matter in the flooded area was higher than that of the non-flooded area at 175-185 m. With the increase of flood duration,the content of organic matter in the 0-10 cm soil layer decreased year by year compared with that in 2008,but in the 10-20 cm soil layer it increased first and followed by a decrease. With the increase of the number cycles of water level fluctuation,the contents of soil alkali hydrolysable nitrogen and available potassium showed a downward trend of fluctuation,and the contents in the 0-10 cm soil layer were more sensitive to flooding compared with those in 10-20 cm layer. The alkali hydrolyzed nitrogen in 0-10 cm soil layer decreased most significantly in 2009 and 2015,and compared with 2008,the decrease at all altitudes was by 37.2%-54.7% and 50.6%-65.7%,respectively. Moreover,the decrease of available potassium in 0-10 cm soil layer was the largest in 2009,up to 17.1%-50.8%. The content of available P decreased year by year,and the loss of available P was the biggest among all the available nutrients. After 1,4,6 and 7 fluctuations of water level,the content of available phosphorus in 0-10 cm layer significantly decreased by 21.8%,45.4%,82.2%,and 90.2%,and the content of available phosphorus in 10-20 cm layer significantly(P < 0. 01) decreased by 44. 3%,61. 5%,83. 5%,and 92%,respectively.【Conclusion 】With continual extension of the operation period of the Three Gorges reservoir,the soil properties of the fluctuating zone change gradually,reflected by the increased soil pH-values,the decreased content of organic matter,and the depleted available nutrients. To a certain extent, this provides a new scientific basis for predicting succession process of ecological environment quality and the changes of soil properties in the reservoir area under long-term flooding conditions.更多还原