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 2UP, United Kingdom.
Sci Total Environ. 2017 Sep 1;593-594:688-694. doi: 10.1016/j.scitotenv.2017.03.136. Epub 2017 Mar 30.
Reactive nitrogen (N) deposition can affect ecosystem processes, particularly in oligotrophic upland habitats. Phosphorus (P) addition has been proposed to reduce the effects of N enrichment on N leaching and acidification, since P limitation can reduce biomass production and consequent sequestration of reactive N. However, biodiversity is often reduced in more productive ecosystems and P limitation may protect against this effect. Responses to P availability in instances of high N deposition are poorly understood. This study investigated the ecosystem response to alleviation of P limitation, using a long-term nutrient addition experiment (1996-2012) three years after ceasing N inputs and 15years after a single P application. Substantial differences were observed in the structure and composition of vegetation species and above-ground vegetation biomass. Vegetation height was greater in the N+P addition treatments (+38% cf. control), with increased cryptogam cover (+47%), whereas N addition increased graminoid species cover (+68%). Vegetation diversity was significantly reduced by the addition of P (-21%), indicating that P limitation is likely to be an important mechanism that limits biodiversity loss in upland habitats exposed to chronic N deposition. Significant differences in soil C and N contents were also observed between treatments. Relative to control, the addition of N increased soil C (+11%) and N (+11%) pool sizes, whereas the addition of N and P reduced soil C (-12%) and N (-13%) pool sizes. This demonstrated the importance of P availability for upland ecosystem processes, and highlights the long-term effects of P addition on vegetation species composition and C storage. Thus, the addition of P cannot be endorsed as a method for reducing impacts of N deposition. Capsule: Phosphorus limitation is a major mechanism governing ecosystem processes in situations of high atmospheric nitrogen deposition.
活性氮（N）沉积会影响生态系统过程，特别是在贫营养的高地生境中。已有人提议添加磷（P）以减少 N 富集对 N 淋溶和酸化的影响，因为 P 限制可以减少生物量的产生，并因此减少活性 N 的固定。然而，在生产力较高的生态系统中，生物多样性往往会减少，而 P 限制可能会防止这种效应。在高 N 沉积的情况下，对 P 可用性的响应尚不清楚。本研究通过一项长期养分添加实验（1996-2012 年），在停止 N 输入三年后和单次 P 应用后 15 年，调查了生态系统对缓解 P 限制的响应。在植被物种结构和组成以及地上植被生物量方面观察到了显著差异。N+P 添加处理的植被高度更高（+38%，与对照相比），隐花植物覆盖度增加（+47%），而 N 添加增加了禾本科植物的覆盖度（+68%）。P 添加显著降低了植被多样性（-21%），表明 P 限制可能是限制暴露于慢性 N 沉积的高地生境生物多样性丧失的一个重要机制。处理之间的土壤 C 和 N 含量也存在显著差异。与对照相比，N 添加增加了土壤 C（+11%）和 N（+11%）库大小，而 N 和 P 的添加减少了土壤 C（-12%）和 N（-13%）库大小。这表明 P 可用性对高地生态系统过程的重要性，并强调了 P 添加对植被物种组成和 C 储存的长期影响。因此，不能将 P 添加作为减少 N 沉积影响的方法。
注释：
