论文以内蒙古克氏针茅草原为研究对象,通过设置不同降雨强度的等量增雨和氮添加实验,研究温带草原土壤氮矿化潜力对不同增雨模式的响应以及氮添加对这种响应的影响。两个增雨处理分别是在6月和7月共增加60 mm降水和自然降雨。增雨方式是单次降雨强度分别为每次2、5、10、20、30 mm,对应的频率分别为每隔2、5、10、20和30 d一次。两个氮添加处理分别是10 g N·m~(-1)·a~(-1)和无氮添加。处理2 a后于8月采集各处理原状土样,在20 ℃和60%田间持水量下进行4周的室内培养实验,测定土壤无机氮含量,计算氮矿化潜力。结果表明:1)总体上,增雨对土壤无机氮含量和氮矿化潜力没有显著影响,但不同的增雨方式对土壤氮矿化潜力影响不同,高强度低频率的增雨有利于提高土壤氮矿化潜力;2)氮添加增加了土壤无机氮含量和氮矿化潜力,与对照相比分别提高了256%和29%;3)氮添加后,每次5 mm的低强度高频率的增雨方式显著提高了土壤氮矿化潜力。这说明,未来增雨模式的短期改变不会影响土壤供氮能力,而氮沉降则能够改变土壤供氮能力对降雨模式的响应。
英文摘要:
Increase in precipitation amount and extreme precipitation events are important characteristics of global change in temperate grasslands and may affect grassland productivity. However, the effects of precipitation increase and extreme precipitation events on soil nitrogen (N) supply capacity remain unclear, which limits the prediction of grassland productivity. In this study, precipitation increase experiments with different intensities and N addition experiments were carried out on a temperate Stipa krylovii steppe in Inner Mongolia, China. The aims of the experiments were to investigate the responses of soil potential N mineralization (SPNM) to precipitation increase and N addition. Precipitation treatment was to increase 60 mm precipitation during June and July, compared to ambient precipitation. Precipitation intensities were set to 2, 5, 10, 20, 30 mm and the frequencies of precipitation were every 2, 5, 10, 20, 30 days, respectively. The treatment of N addition was 10 g N·m~(-1)·a~(-1), compared with ambient N deposition. Soil samples in each treatment were collected at the end of August after two years and then incubated in lab under 20 ℃ and 60% of water holding capacity for four weeks. SPNM were obtained by measuring the soil inorganic nitrogen (SIN). The results showed that: 1) Precipitation increase had no influence on SIN and SPNM, but high intensity and low frequency of precipitation increased SPNM. 2) N enrichment increased SIN and SPNM by 256% and 29%, respectively, compared to control. 3) After N addition, 5 mm precipitation each time significantly increased the SPNM. The work indicates that future precipitation increase has no much influence on soil N supply capacity, however, the effects of future precipitation might be modified by increasing N deposition.