Institute of Biological, Environmental and Rural Sciences, Penglais Campus, Aberystwyth University, Wales SY23 3DD, United Kingdom; Centre for Ecology & Hydrology, Bangor, Environment Centre Wales, Bangor LL57 2UW, United Kingdom.
Centre for Ecology & Hydrology, Bangor, Environment Centre Wales, Bangor LL57 2UW, United Kingdom.
Sci Total Environ. 2018 Mar 15;618:1199-1209. doi: 10.1016/j.scitotenv.2017.09.202. Epub 2017 Sep 24.
Reactive nitrogen (N) deposition can affect many ecosystem processes, particularly in oligotrophic habitats, and is expected to affect soil C storage potential through increases in microbial decomposition rate as a consequence of greater N availability. Increased N availability may also result in changes in the principal limitations on ecosystem productivity. Phosphorus (P) limitation may constrain productivity in instances of high N deposition, yet ecosystem responses to P availability are poorly understood. This study investigated CO and CH flux responses to N and P enrichment using both short- (1year) and long-term (16year) nutrient addition experiments. We hypothesised that the addition of either N or P will increase CO and CH fluxes, since both plant production and microbial activity are likely to increase with alleviation from nutrient limitation. This study demonstrated the modification of C fluxes from N and P enrichment, with differing results subject to the duration of nutrient addition. On average, relative to control, the addition of N alone inhibited CO flux in the short-term (-9%) but considerably increased CO emissions in the long-term (+35%), reduced CH uptake in the short term (-90%) and reduced CH emission in the long term (-94%). Phosphorus addition increased CO and CH emission in the short term (+20% and +184% respectively), with diminishing effect into the long term, suggesting microbial communities at these sites are P limited. Whilst a full C exchange budget was not examined in the experiment, the potential for soil C storage loss with long-term nutrient enrichment is demonstrated and indicates that P addition, where P is a limiting factor, may have an adverse influence on upland soil C content.
活性氮（N）沉积会影响许多生态系统过程，特别是在贫营养生境中，并且预计会通过增加微生物分解率来影响土壤 C 储存潜力，因为 N 的可用性增加。增加的 N 可用性也可能导致生态系统生产力的主要限制因素发生变化。在高 N 沉积的情况下，P 限制可能会限制生产力，但对 P 可用性的生态系统响应知之甚少。本研究使用短期（1 年）和长期（16 年）养分添加实验，调查了 N 和 P 富集对 CO 和 CH 通量的影响。我们假设添加 N 或 P 都会增加 CO 和 CH 通量，因为植物生产力和微生物活性都可能随着养分限制的缓解而增加。本研究证明了 C 通量从 N 和 P 富集的改变，由于养分添加的持续时间不同，结果也有所不同。与对照相比，单独添加 N 在短期内平均抑制 CO 通量（-9%），但在长期内大大增加 CO 排放（+35%），在短期内减少 CH 吸收（-90%），并在长期内减少 CH 排放（-94%）。P 添加在短期内增加了 CO 和 CH 排放（分别增加 20%和 184%），长期内效果减弱，表明这些地点的微生物群落受到 P 的限制。虽然实验中没有检查完整的 C 交换预算，但长期养分富集导致土壤 C 储存损失的潜力得到了证明，并表明在 P 是限制因素的情况下，P 添加可能对旱地土壤 C 含量产生不利影响。
