Nutrient addition experiment at the Alpine treeline site Stillberg, Switzerland

# Background information The availability of nitrogen (N) and phosphorus (P) is considered to be a major factor limiting growth and productivity in terrestrial ecosystems globally. This project aimed to determine whether the growth stimulation documented in previous short‐term fertilisation trials persisted in a longer‐term study (12 years) in the treeline ecotone, and whether possible negative effects of nutrient addition offset the benefits of any growth stimulation. Over the course of the 12 study years, NPK fertiliser corresponding to 15 or 30 kg N ha−1 a−1 was added annually to plots containing 30‐year‐old *Larix decidua* or 32‐year-old *Pinus uncinata* individuals with an understorey of mainly ericaceous dwarf shrubs. To quantify growth, annual shoot increments of trees and dwarf shrubs as well as radial growth increments of trees were measured. Nutrient concentrations in the soil were also measured and the foliar nutritional status of trees and dwarf shrubs was assessed. # Experimental design Over an elevation gradient of 140 m across the treeline afforestation site Stillberg, 22 locations were chosen that covered the whole range of microenvironmental conditions (*see* Nutrient addition experimental design.png). Half of the blocks included European larch (*L. decidua*) and the other half included mountain pine (*P. uncinata*). Within each block, three plantation quadrats were randomly selected as experimental plots and each plot was assigned to a control (no fertilisation) or to one of two fertiliser dose treatments (15 kg and 30 kg N ha−1 a−1). Treatments were assigned randomly but confined so that the location of fertilised plots within a block was not directly above control plots to avoid nutrient input from drainage. For details about the experiment, *see* Möhl et al (2019). # Data description The available datasets contain climate variables (2004-2016), nutrient isotope measurements (2010 & 2016), shrub growth measurements (2004-2016), soil parameter measurements and annual ring and shoot measurements (2004-2016). All data can be found here: <https://figshare.com/articles/dataset/Twelve_years_of_low_nutrient_input_stimulates_growth_of_trees_and_dwarf_shrubs_in_the_treeline_ecotone/7025858>

# 背景信息
氮（N）和磷（P）的可获得性被认为是全球陆地生态系统中限制植被生长与生产力的核心制约因子。本研究旨在探究：此前短期施肥试验中观测到的生长促进效应，在林线交错带开展的12年长期试验中是否依然存在；同时探明养分添加可能带来的负面效应是否会抵消生长促进带来的收益。

在为期12年的试验周期内，研究人员每年向样地施加NPK复合肥，施氮量分别为15 kg N ha⁻¹ a⁻¹或30 kg N ha⁻¹ a⁻¹；供试样地内种植有30年生的欧洲落叶松（*Larix decidua*）或32年生的山松（*Pinus uncinata*），林下植被以杜鹃花科矮灌木为主。为量化植被生长状况，研究人员测定了乔木与矮灌木的当年枝伸长量，以及乔木的径向生长量；同时测定了土壤养分浓度，并评估了乔木与矮灌木的叶片营养状态。

# 试验设计
本试验在海拔梯度跨度140 m的林线造林点Stillberg开展，共选取22个样点，覆盖该区域全部微环境条件（详见《养分添加试验设计.png》）。其中一半样区种植欧洲落叶松（*Larix decidua*），另一半种植山松（*Pinus uncinata*）。每个样区内随机选取3个造林样方作为试验样地，每块样地被随机分配至对照组（不施肥）或两种施肥剂量处理组之一（15 kg N ha⁻¹ a⁻¹或30 kg N ha⁻¹ a⁻¹）。处理组的分配采用随机原则，但同时设置约束：样区内施肥样地不得直接位于对照样地上方，以避免径流带来的养分输入干扰。试验详细细节参见Möhl等人（2019）的研究。

# 数据说明
本数据集包含以下内容：2004-2016年的气候变量数据、2010年与2016年的养分同位素测定数据、2004-2016年的矮灌木生长测定数据、土壤参数测定数据，以及2004-2016年的年轮与枝条生长测定数据。全部数据可通过以下链接获取：<https://figshare.com/articles/dataset/Twelve_years_of_low_nutrient_input_stimulates_growth_of_trees_and_dwarf_shrubs_in_the_treeline_ecotone/7025858>