Department of Applied Ecology, Hochschule Geisenheim University, Geisenheim, Germany.
Department of Landscape Ecology, Institute for Natural Resource Conservation, Kiel University, Kiel, Germany.
PLoS One. 2020 May 29;15(5):e0233709. doi: 10.1371/journal.pone.0233709. eCollection 2020.
Populations of Arnica montana, a characteristic species of nutrient poor grasslands in Central Europe, have been deteriorating over the last decades, especially in lowland regions. Population size has been declining and signs of sexual reproduction are scarce. To start a long-term regeneration program, we investigated the major habitat specific drivers for the decline in Hesse, Germany. Firstly, we conducted a field study to analyze habitat characteristics of 32 Hessian lowland sites, comparing those on which this species has become extinct during the last 15 years with sites of small and declining, as well as large, stable populations. We compared habitat traits focusing on soil parameters, nutrients, and vegetation characteristics. Secondly, we set up a greenhouse experiment to study the response of A. montana seedlings to competition and nutrient input to assess the effects of competition pressure and fertilization. The results show lower carbon-to-nitrogen ratios and higher Ellenberg nitrogen indicator values on sites with extinct populations compared to existing populations. Both pH and Ellenberg soil reaction indicator values were higher on sites with extinct populations. In the greenhouse, the combination of nitrogen addition and competition resulted in lower seedling numbers. While rosette size was not dependent on fertilization, growth was strongly enhanced in the plots lacking vegetation. Both studies suggest that soil nutrient enrichment followed by competition pressure diminishes the number of safe sites for A. montana seedling recruitment and establishment and negatively impacts the growth of existing rosettes, thus leading to the continuous decline of populations. There is an urgent need for actions to reduce unintentional nitrogen deposition in the remaining nutrient poor areas as well as to modify land use to withdraw nutrients from enriched soils in order to preserve the remaining A. montana populations and to create bare ground for the safekeeping and enhancement of self-sustainable populations.
欧洲中部贫瘠草原特有的高山火绒草种群在过去几十年中不断恶化，尤其是在低地地区。种群数量一直在减少，有性繁殖的迹象也很少。为了启动一个长期的再生计划，我们调查了德国黑森州导致其数量下降的主要栖息地特定驱动因素。首先，我们进行了一项实地研究，分析了 32 个黑森州低地地点的栖息地特征，将这些地点与在过去 15 年内已经灭绝的地点以及规模较小且正在减少以及规模较大且稳定的地点进行了比较。我们比较了重点放在土壤参数、养分和植被特征上的栖息地特征。其次，我们建立了一个温室实验，研究高山火绒草幼苗对竞争和养分输入的反应，以评估竞争压力和施肥的影响。结果表明，与现存种群相比，灭绝种群所在的地点的碳氮比更低，埃伦伯格氮指示剂值更高。灭绝种群所在的地点的 pH 值和埃伦伯格土壤反应指示剂值都更高。在温室中，氮添加和竞争的结合导致幼苗数量减少。虽然罗塞塔的大小不依赖于施肥，但在缺乏植被的地块中，生长得到了强烈的增强。这两项研究表明，土壤养分富化随后是竞争压力，减少了高山火绒草幼苗定植和建立的安全地点数量，并对现有的罗塞塔生长产生负面影响，从而导致种群的持续下降。迫切需要采取行动减少剩余贫瘠地区的无意氮沉积，并改变土地利用方式，从富化土壤中去除养分，以保护剩余的高山火绒草种群，并为安全保存和增强自我可持续的种群创造裸露地面。
