不同干湿交替频率对土壤速效养分、水溶性有机碳的影响

Influence of different drying-rewetting frequencies on available soil nutrients and DOC

为了探究不同干湿交替频率对速效养分、DOC的影响机理,选择北京褐土(表层0—10cm土壤)为研究对象,采用室内模拟控制实验法,控制其他变量,设计一系列不同频率的干湿交替实验,在58d内设置了10d土壤培育期和48d试验期,其中48d试验期设置0、1、2、3、4次干湿交替,试验结束(第58天)进行速效养分、水溶性有机碳(DOC,Dissolved organic carbon)等主要土壤速效养分指标测定。采用单因素方差分析与LSD多重比较法进行数据分析,研究结果显示:恒湿组的速效钾、硝态氮含量比干湿交替组高;低频率的干湿交替使得土壤速效钾含量减少,高频率可能在后期出现释钾现象,速效钾含量随着干湿交替频率增加可能会有所增加,趋近恒湿组速效钾水平,4次干湿交替频率是出现速效钾回升的临界次数;硝态氮含量随着频率增加也有增加趋势,低频率的1次干湿交替(DW1,1 drying-rewetting cycle)硝态氮含量最低,高频率的4次干湿交替(DW4,4 dryingrewetting cycles)最高,干湿交替频率增加更频繁的打破平衡,促进矿化,干湿交替组也趋近恒湿组的硝态氮水平。经过干湿交替,土壤中速效钾、铵态氮、DOC的含量下降,硝态氮含量增加,速效磷、pH的变化不明显。在固定时间内(48d),随着干湿交替的频率增加(从1次到2、3、4次),周期变短(从48d到24、16、12d),干燥与湿润的持续时间变短(从24d到12、8、6d),干湿交替组的速效钾、硝态氮含量分别趋于恒湿组的速效钾、硝态氮水平。

To investigate the mechanism of influence of different drying-rewetting frequencies on available soil nutrients and DOC,in this study, we collected cinnamon soil at a depth of 0-10cm below the surface in Beijing and manipulated soil water stress in the laboratory by exposing soil to 0, 1, 2, 3, or 4 drying-rewetting cycles for 58 days, including a 10 day pre-incubation period and a 48 day treatment period. After 58 days, principal soil fertility indexes such as available nutrients and DOC were tested to observe changes as a result of different drying-rewetting frequencies. Data were analyzed using single-factor variance analysis and the Least Significant Difference method （LSD） for the dependent groups. Available K and nitrate nitrogen were lower in the drying and rewetting treatments than in the constantly moist treatment（CM）. Low drying-rewetting frequency might lead to the loss of available K, while K release might appear in the late stages of high drying-rewetting frequency conditions. As drying-rewetting frequency increased, the available K also increased. Four drying-rewetting cycles were critical for K release. Increasing the drying-rewetting frequency would result in frequent perturbations to the balance between various forms of nitrogen, and the mineralization rate would increase at the lowest drying-wetting frequency （DW1, 1 drying-rewetting cycle） and the highest drying-wetting frequency （DW4, 4 drying-rewetting cycles）. As drying-wetting frequency increased, nitrate nitrogen of drying-rewetting treatment become closer to that of constantly moist （CM）. Soil nitrate nitrogen significantly increased, while available K, ammonium nitrogen, and DOC significantly decreased, with drying-wetting frequency, and available P and pH were relatively insensitive to drying-rewetting frequency. In 48 days, with increase in drying-rewetting frequency （from 1 cycle to 2, 3, and 4 cycles） and decrease in drying-rewetting period （from 48d to 24, 16, and 12d） and the last period of each drying or wetting period （from 24d to 12, 8, and 6d）, nitrate nitrogen and available K tended to increase to levels close to those of the constantly moist condition.