Gordon C, Wynn J M, Woodin S J
Department of Plant and Soil Science, Cruickshank Building, University of Aberdeen, St Machar Drive, Aberdeen, AB24 3UU, UK.
New Phytol. 2001 Mar;149(3):461-471. doi: 10.1046/j.1469-8137.2001.00053.x.
• This study investigates effects of nitrogen and phosphorus on high Arctic heath vegetation, particularly bryophytes. • Heath communities received factorial combinations of nitrogen (0, 10 and 50 kg ha yr ) and phosphorus (0 and 5 kg ha yr ) in five applications per growing season, for 8 yr. • Nitrogen decreased lichen cover but did not affect cover of any other functional type. However, just 10 kg ha yr increased the proportion of physiologically active bryophte shoots, and decreased their nitrate assimilation capacity. Phosphorus had greater effects, and the combination of both nutrients altered species composition. Individual bryophyte species displayed contrasting responses to fertilization, suggesting that they should not be grouped as a single functional type. • The 'critical load' of nitrogen for Arctic heath lies below 10 kg ha yr . Nitrogen and phosphorus are colimiting in this sytem, so the critical load of nitrogen will be lower where phosphorus availability is greater. Responses of vegetation to any increase in net mineralisation due to soil warming will depend on the ratio in which nitrogen and phosphorus availabilities increase. The effects of nutrient enhancement are very persistent.
• 本研究调查了氮和磷对北极高沼地植被，特别是苔藓植物的影响。
• 高沼地群落每个生长季节分五次施用氮（0、10和50千克/公顷·年）和磷（0和5千克/公顷·年）的析因组合，持续8年。
• 氮减少了地衣覆盖，但未影响任何其他功能类型的覆盖。然而，仅10千克/公顷·年就增加了生理活性苔藓枝条的比例，并降低了它们的硝酸盐同化能力。磷的影响更大，两种养分的组合改变了物种组成。个别苔藓物种对施肥表现出不同的反应，这表明它们不应被归为单一功能类型。
• 北极高沼地氮的“临界负荷”低于10千克/公顷·年。在这个系统中氮和磷共同起限制作用，所以在磷有效性更高的地方氮的临界负荷会更低。植被对因土壤变暖导致的净矿化增加的反应将取决于氮和磷有效性增加的比例。养分增加的影响非常持久。
