Department of Science for Nature and Environmental Resources (DipNET), University of Sassari, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.
Euro-Mediterranean Centre on Climate Change (CMCC), IAFES Division, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.
Environ Sci Pollut Res Int. 2017 Dec;24(34):26160-26171. doi: 10.1007/s11356-017-8852-5. Epub 2017 Apr 6.
Increased atmospheric nitrogen (N) deposition is known to alter ecosystem carbon source-sink dynamics through changes in soil CO fluxes. However, a limited number of experiments have been conducted to assess the effects of realistic N deposition in the Mediterranean Basin, and none of them have explored the effects of N addition on soil respiration (R ). To fill this gap, we assessed the effects of N supply on R dynamics in the following two Mediterranean sites: Capo Caccia (Italy), where 30 kg ha year was supplied for 3 years, and El Regajal (Spain), where plots were treated with 10, 20, or 50 kg N ha year for 8 years. Results show a complex, non-linear response of soil respiration (R ) to N additions with R overall increasing at Capo Caccia and decreasing at El Regajal. This suggests that the response of R to N addition depends on dose and duration of N supply, and the existence of a threshold above which the N introduced in the ecosystem can affect the ecosystem's functioning. Soil cover and seasonality of precipitations also play a key role in determining the effects of N on R as shown by the different responses observed across seasons and in bare soil vs. the soil under canopy of the dominant species. These results show how increasing rates of N addition may influence soil C dynamics in semiarid ecosystems in the Mediterranean Basin and represent a valuable contribution for the understanding and the protection of Mediterranean ecosystems.
大气氮（N）沉降增加已知会通过土壤 CO 通量的变化来改变生态系统碳源-汇动态。然而，仅有少数实验评估了地中海盆地中实际氮沉降的影响，而且没有一个实验探索了氮添加对土壤呼吸（R ）的影响。为了填补这一空白，我们评估了氮供应对以下两个地中海地点的 R 动态的影响：卡波·卡西亚（意大利），在那里连续 3 年供应了 30 公斤/公顷；和埃尔雷加哈尔（西班牙），在那里连续 8 年以 10、20 或 50 公斤 N/公顷进行了处理。结果表明，土壤呼吸（R ）对氮添加的反应是复杂的、非线性的，R 总体上在卡波·卡西亚增加，而在埃尔雷加哈尔减少。这表明，R 对氮添加的反应取决于氮供应的剂量和持续时间，以及在生态系统中引入的氮可能影响生态系统功能的阈值的存在。土壤覆盖和降水的季节性也在决定氮对 R 的影响方面起着关键作用，这从不同季节和裸土与优势种冠层下的土壤之间观察到的不同反应中可以看出。这些结果表明，氮添加率的增加如何可能影响地中海盆地半干旱生态系统中的土壤 C 动态，为理解和保护地中海生态系统提供了有价值的贡献。
