Area of Ecology, University of León, E-24071 León, Spain; Institute of Environmental Research (IMA), University of Léon, E-24071 León, Spain.
Area of Ecology, University of León, E-24071 León, Spain; Institute of Environmental Research (IMA), University of Léon, E-24071 León, Spain.
Sci Total Environ. 2018 Oct 1;637-638:980-990. doi: 10.1016/j.scitotenv.2018.05.092. Epub 2018 May 13.
Elevated atmospheric nitrogen (N) deposition is a major driver of change, altering the structure/functioning of nutrient-poor Calluna vulgaris-heathlands over Europe. These effects amply proven for north-western/central heathlands may, however, vary across the ecosystem's distribution, especially at the range limits, as heathlands are highly vulnerable to land-use changes combined with present climate change. This is an often overlooked and greatly understudied aspect of the ecology of heathlands facing global change. We investigated the effects of five N-fertilisation treatments simulating a range of N deposition rates (0, 10, 20, and 50 kg N ha yr for 1 year; and 56 kg N ha yr for 9 years) on the Calluna-plants, the plant functional groups, species composition and richness of two life-cycle stages (building/young- and mature-phase) of Calluna-heathlands at their rear-edge limit. Our findings revealed a dose-related response of the shoot length and number of flowers of young and mature Calluna-plants to the addition of N, adhering to the findings from other heathland locations. However, cumulative high-N loading reduced the annual growth and flowering of young plants, showing early signs of N saturation. The different plant functional groups showed contrasting responses to the cumulative addition of N: annual/perennial forbs and annual graminoids increased with quite low values; perennial graminoids were rather abundant in young heathlands but only slightly augmented in mature ones; while bryophytes and lichens strongly declined at the two heathland life-cycle stages. Meanwhile there were no significant N-driven changes in plant species composition and richness. Our results demonstrated that Calluna-heathlands at their low-latitude distribution limit are moderately resistant to cumulative high-N loading. As north-western/central European heathlands under high-N inputs broadly experienced the loss of plant diversity and pronounced changes in plant species dominance, rear-edge locations may be of critical importance to unravel the mechanisms of heathland resilience to future global change.
大气氮（N）沉降的增加是变化的主要驱动因素，改变了欧洲贫营养的石楠-石南灌丛的结构/功能。这些在西北/中欧石南灌丛中得到充分证明的影响，然而，可能因生态系统的分布而有所不同，尤其是在生态系统的分布范围的限制区域，因为石南灌丛极易受到土地利用变化的影响，加上当前的气候变化。这是一个经常被忽视且研究不足的石南灌丛生态学方面，在全球变化背景下极具研究价值。我们研究了五种 N 施肥处理对石南植物、植物功能群、两种生活史阶段（幼年期和成熟期）的物种组成和丰富度的影响，这五种 N 施肥处理模拟了一系列 N 沉降速率（0、10、20 和 50 kg N ha yr 持续 1 年；和 56 kg N ha yr 持续 9 年）。在石南灌丛的后缘限制区。我们的研究结果表明，幼年期和成熟期石南植物的茎长和花数与 N 的添加呈剂量相关的响应，这与其他石南灌丛地点的研究结果一致。然而，高 N 负荷的累积减少了幼年期植物的年生长和开花，表现出 N 饱和的早期迹象。不同的植物功能群对 N 的累积添加表现出不同的反应：一年生/多年生草本植物和一年生草本植物增加，而多年生草本植物在幼年期灌丛中相当丰富，但在成熟期灌丛中仅略有增加；而苔藓和地衣在两个石南灌丛生活史阶段都强烈减少。同时，植物物种组成和丰富度没有明显的 N 驱动变化。我们的研究结果表明，在低纬度分布限制区的石南灌丛对累积的高 N 负荷具有中等抗性。由于西北/中欧石南灌丛在高 N 输入下广泛经历了植物多样性的丧失和植物物种优势的显著变化，后缘区域可能对揭示石南灌丛对未来全球变化的恢复力机制具有重要意义。
