为了解不同退化阶段盐碱草甸草原土壤硝化作用强度特征及其影响因素,采用空间代替时间的方法,以松嫩平原盐碱草甸草原植被退化过程中4种典型植物群落为对象,以未做处理为参照,设置刈割、施氮和刈割同时施氮3种处理,测定了土壤的硝化作用强度(NI)、pH值、电导率(EC)、含水量(SMC)和有效磷(OP)、硝态氮(NO-3-N)、铵态氮(NH+4-N)及全氮(TN)的含量。结果 显示:(1)土壤NI与pH值、电导率、含水量、OP和NO-3-N呈极显著正相关关系(p<0.01); 通过逐步回归分析的方法得出土壤NI的重要影响因子,重要影响因子对土壤NI影响强弱表现为:pH值>有效磷含量>含水量>硝态氮含量,并推断土壤硝态氮含量可作为土壤NI的一个重要表征参数。(2)未作处理时,星星草群落与碱蓬群落土壤硝化作用强度分别为13.4,13.5 mg/(kg·h),显著高于羊草群落和退化羊草群落的5.0,2.5 mg/(kg·h),刈割和施氮处理分别使星星草群落土壤NI提高96.88%,253.77%,混合处理使其提高413.70%,显著高于其他3种植物群落,由此可见,在人为刈割和施氮肥的干预下,星星草群落土壤铵态氮可能更易转变为硝态氮,氮素流失的风险也更大,因此可认为星星草群落处于盐碱草甸退化过程中的关键阶段。
In order to understand the characteristics and influencing factors of soil nitrification intensity in saline-alkaline meadow grasslands at different degradation stages, based on space-for-time method, and four typical plant communities in the process of saline-alkaline meadow grassland vegetation degradation in the Songnen Plain were selected as objects. Based on the untreated treatment, three treatments of cutting, nitrogen application and simultaneous nitrogen application were set. The soil nitrification intensity(NI), pH, electrical conductivity(EC), soil moisture content(SMC)and available phosphorus(OP), nitrate nitrogen(NO-3-N), ammonium nitrogen(NH+4-N)and total nitrogen(TN)content were investigated. The results showed that:(1)the soil nitrification intensity had a very significant positive correlation with pH, EC, SMC, OP and NO-3-N(p<0.01); through stepwise regression analysis, important influence factors of soil nitrification intensity were obtained, the influence of important factors on soil nitrification intensity were ranked as order: pH>OP>SMC>NO-3-N, and it could be concluded that soil nitrate nitrogen content could be used as an important characterization parameter for soil nitrification intensity;(2)the soil nitrification intensity of untreated Puccinellia tenuiflora community and Suaeda salsa community were 13.4 mg/(kg·h)and 13.5 mg/(kg·h), respectively, which were both much higher than those of Leymus chinensis community and degraded Leymus chinensis community [5.0 mg/(kg·h)and 2.5 mg/(kg·h)], respectively; mowing and nitrogen treatment increased the soil nitrification intensity of Puccinellia tenuiflora community by 96.88% and 253.77%, respectively, and mixed treatment increased 413.70%, which was significantly higher than that of the other three plant communities. It can be seen that the soil ammonium nitrogen in the Puccinellia tenuiflora community may be more easily converted to nitrate nitrogen under the intervention of man-made mowing and nitrogen fertilizer application, and the risk of nitrogen loss is also greater. Therefore, it can be considered that the Puccinellia tenuiflora community is at a critical stage in the degradation process of saline-alkali meadows.
