为探究不同降雨频率对甘南尕海湿草甸土壤铵态氮（$\mathrm{NH}_{4}^{+}-\mathrm{N}$）、硝态氮（$\mathrm{NO}_{3}^{-}-\mathrm{N}$）、全氮（TN）的影响,于2019年植物生长季（5—10月）,通过模拟极端降雨（25 mm灌溉量）设置5种不同降雨频率处理：CK只接收自然降雨,DF1每周浇灌1次（19次×25mm）,DF2每2周浇灌1次（9次×25 mm）,DF3每3周浇灌1次（6次×25 mm）,DF4每4周浇灌1次（4次×25 mm）;所有处理均接收自然降雨。结果表明：不同降雨频率处理对尕海湿草甸土壤氮组分有显著影响（P<0.05）。降雨频率的增加提高了5—10月土壤$ \mathrm{NH}_{4}^{+}-\mathrm{N}$和$\mathrm{NO}_{3}^{-}-\mathrm{N}$含量,$ \mathrm{NH}_{4}^{+}-\mathrm{N}$和$\mathrm{NO}_{3}^{-}-\mathrm{N}$的峰值有显著升高,两者的峰值并未提前出现;与CK相比,降雨频率的增加提高了土壤$ \mathrm{NH}_{4}^{+}-\mathrm{N}$和$\mathrm{NO}_{3}^{-}-\mathrm{N}$含量,降低了TN含量;而在不同降雨频率间,随降雨频率的梯度增加,0~40 cm土层$ \mathrm{NH}_{4}^{+}-\mathrm{N}$和$\mathrm{NO}_{3}^{-}-\mathrm{N}$均呈先增后减的趋势,TN呈先减后增的趋势;不同降雨频率处理下,各土层$\mathrm{NH}_{4}^{+}-\mathrm{N}$的$\mathrm{TN}$占比均高于$\mathrm{NO}_{3}^{-}-\mathrm{N}$,且土壤$ \mathrm{NH}_{4}^{+}-\mathrm{N}$、$\mathrm{NO}_{3}^{-}-\mathrm{N}$、$\mathrm{TN}$含量均随土层深度增加而降低。

In the context of global climate change, precipitation patterns have changed significantly, both in terms of rainfall frequency and amount of precipitation. Changes in precipitation patterns will significantly affect the ecosystem functions of wetlands, especially the process of soil nitrogen cycle transformation. To explore the effects of different rainfall frequencies on the soil ammonium nitrogen ( $\mathrm{NH}_{4}^{+}-\mathrm{N}$), nitrate nitrogen ($\mathrm{NO}_{3}^{-}-\mathrm{N}$), and total nitrogen (TN) of the Gahai wet meadow in Gannan (located in Gansu Province, China), we set five different rainfall frequencies by simulating extreme rainfall (25 mm irrigation) in the 2019 plant growth season, May-October: CK, natural rainfall only; DF1, watered once a week (19 times×25 mm); DF2, watered once every 2 weeks (9 times × 25 mm); DF3, watered once every 3 weeks (6 times×25 mm); and DF4, watered once every 4 weeks (4 times × 25 mm). All treatments were exposed to natural rainfall. The results showed that different rainfall frequencies have significant effects on the soil nitrogen components of the wet meadow (P < 0.05). The increase of rainfall frequency increased the soil $\mathrm{NH}_{4}^{+}-\mathrm{N}$ and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ content in the growing season, from May to October; the peak of $\mathrm{NH}_{4}^{+}-\mathrm{N}$ and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ increased significantly. Compared with CK, the increase in rainfall frequency increased the soil $\mathrm{NH}_{4}^{+}-\mathrm{N}$ and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ content and reduced the TN content. Among different rainfall frequencies, with the gradient of rainfall frequency increasing, the 0-40 cm layer $ \mathrm{NH}_{4}^{+}-\mathrm{N}$ and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ showed a trend of first increasing and then decreasing and $\mathrm{TN}$ showed a trend of first decreasing and then increasing. Under different rainfall frequency treatments, the proportion of TN of $\mathrm{NH}_{4}^{+}-\mathrm{N}$ in each soil layer was higher than that of $\mathrm{NO}_{3}^{-}-\mathrm{N}$, and soil$\mathrm{NH}_{4}^{+}-\mathrm{N}$, $\mathrm{NO}_{3}^{-}-\mathrm{N}$, and $\mathrm{TN}$ content decreased with the increase in soil depth.