内蒙古温带典型草原羊尿斑块土壤化学特性变化

在内蒙古冷蒿小禾草草原1989年围封禁牧地,研究了天然羊尿尿斑土壤化学特性的变化规律,结果表明,土壤pH值于施尿后第2天达到最大值,以后呈下降趋势,58天后pH值基本稳定在6．5左右且低于对照区水平,施尿区土壤可溶性有机碳含量的变化趋势与pH值的变化基本一致,两者存在显著的正相关关系(P<0．01)．施尿后土壤总可溶性磷含量显著提高(P<0．05),第2天达到最大值(35．1mg·L^-1)。总可溶性磷各组分钼酸反应磷、可溶性有机磷和可溶性缩合磷百分比均存在两个明显的变化阶段,钼酸反应磷和可溶性有机磷与可溶性缩合磷存在显著的负相关关系(P<0．05)．施尿区土壤NH4^+-N在第2天达到最大值。以后呈下降趋势;NO3-N含量14天后开始显著增加,并于第21天达到最大值,其变化呈现明显的“双峰型”特征,并较NH4^+-N存在显著的时滞现象;施尿后土壤可溶性有机氮含量显著增加,并表现为“双峰型”变化特征。

Changes of soil chemical properties in sheep urine patches in Inner Mongolia steppe

Sheep play an important role in the nutrient cycling in extensively grazed grasslands, mainly through their annual return of around 5-25 kg N in the shape of urine. This return changes the temporal distribution of nutrients in soil and alters their bioavailability. Urine patches are the most important areas of the transformation and cycling of nutrients in the grazed grasslands. In order to make known the changes of soil chemical properties in sheep urine patches, an experiment was set up in the typical steppe area of central Inner Mongolia. The results indicated that soil pH value reached the maximum on the second day after urine excretion, and then declined. It maintained at around 6.5 from the 58th day, which was under the level of the control. Soil dissolved organic carbon (DOC) in urine patches exhibited the identical changing characteristics with soil pH, and had a significantly (P < 0.01) positive correlation with it. Soil total dissolved phosphorus (TDP) increased significantly (P < 0.05) after urine excretion, and reached the maximum at the 2nd day. The percentage of molybdate reactive phosphorus (MRP), dissolved organic phosphorus (DOP) and dissolved condensed phosphorus (DCP) showed significantly two changing phases, and there existed significantly (P < 0.05) negative correlations between MRP, DOP and DCP. Soil NH4+-N reached the maximum on the 2nd day after urine excretion and then declined, while soil NO3(-)-N increased significantly after 14 days and reached the maximum on the 21st day, showing significant "double peaks" characteristics. Soil dissolved organic nitrogen (DON) also increased significantly after urine excretion.