Xu Guorong, Li Guang, Wu Jiangqi, Ma Weiwei, Wang Haiyan, Yuan Jianyu, Li Xiaodan
College of Forestry, Gansu Agricultural University, Lanzhou, 730070, China.
State Key Laboratory of Aridland Crop Science, Gansu Agricultural University, Lanzhou, 730070, China.
Sci Rep. 2023 Sep 8;13(1):14860. doi: 10.1038/s41598-023-39267-3.
Global climate change has led to a significant increase in the frequency of extreme rainfall events in the Qinghai-Tibetan Plateau (QTP), thus potentially increasing the annual rainfall amounts and, consequently, affecting the net soil nitrogen (N) mineralization process. However, few studies on the responses of the soil net N mineralization rates to the increases in rainfall amounts and frequencies in alpine wet meadows have been carried out. Therefore, the present study aims to assess the effects of rainfall frequency and amount changes on the N fixation capacity of wet meadow soils by varying the rainfall frequency and amount in the Gahai wet meadow in the northeastern margin of the QTP during the plant-growing season in 2019. The treatment scenarios consisted of ambient rain (CK) and supplementary irrigation at a rate of 25 mm, with different irrigation frequencies, namely weekly (DF1), biweekly (DF2), every three weeks (DF3), and every four weeks (DF4). According to the obtained results, the increased rainfall frequency and amount decreased the soil mineral N stock and increased the aboveground vegetation biomass (AB) amounts and soil water contents in the wet meadows of the QTP. Ammonium (NH-N) and nitrate N (NO-N) contributed similarly to the mineral N contents. However, the ammonification process played a major role in the soil mineralization process. The effects of increasing rainfall amount and frequency on N mineralization showed seasonal variations. The N mineralization rate showed a single-peaked curve with increasing soil temperature during the rapid vegetation growth phase, reaching the highest value in August. In addition, the N mineralization rates showed significant positive correlations with soil temperatures and NH-N contents and a significant negative correlation with AB (P < 0.05). The results of this study demonstrated the key role of low extreme rainfall event frequencies in increasing the net soil N mineralization rates in the vegetation growing season, which is detrimental to soil N accumulation, thereby affecting the effectiveness of soil N contents.
全球气候变化导致青藏高原极端降雨事件的频率显著增加，从而可能增加年降雨量，进而影响土壤净氮矿化过程。然而，关于高山湿草甸土壤净氮矿化速率对降雨量和降雨频率增加的响应的研究很少。因此，本研究旨在通过改变2019年植物生长季节青藏高原东北缘尕海湿草甸的降雨频率和降雨量，评估降雨频率和降雨量变化对湿草甸土壤固氮能力的影响。处理方案包括自然降雨（CK）和以25毫米的速率进行补充灌溉，灌溉频率不同，即每周（DF1）、每两周（DF2）、每三周（DF3）和每四周（DF4）。根据所得结果，降雨频率和降雨量的增加降低了土壤矿质氮储量，增加了青藏高原湿草甸的地上植被生物量（AB）和土壤含水量。铵态氮（NH-N）和硝态氮（NO-N）对矿质氮含量的贡献相似。然而，氨化过程在土壤矿化过程中起主要作用。降雨量和降雨频率增加对氮矿化的影响呈现季节性变化。在植被快速生长阶段，氮矿化速率随土壤温度升高呈单峰曲线变化，8月达到最高值。此外，氮矿化速率与土壤温度和NH-N含量呈显著正相关，与AB呈显著负相关（P<0.05）。本研究结果表明，低频率极端降雨事件在植被生长季节增加土壤净氮矿化速率方面起关键作用，这不利于土壤氮积累，从而影响土壤氮含量的有效性。
