Toolik Lake E. Vaginatum Root Mineral Nutrition [Welker, J. and J. Fahnestock]

Soil cores of 5cm diameter and 20cm depth were taken at approximately 2 week intervals during the 2001 growing season. Three age classes of Eriophorum vaginatum roots (gray (senesced), brown (suberized) and white (active)) were extracted from the cores. Following extraction, cores were cut into 5 4cm sections and sorted for roots within 1 week of extraction. Prior to processing, cores were refrigerated at ~5(C. Some root samples were unwashed, then dried at 70(C for 48 hours prior to coupled combustion/reduction and gas chromatography analysis (CHN-1000, LECO Corporation). Additional samples were washed, and some unwashed, then analyzed using the soil-corrected method (Hunt et al., 1999). Unwashed roots were presumed to retain nutrient characteristics of the rhizoplane. Soil-corrected washed and unwashed root analysis was presumed to estimate nutrient concentrations specifically in the roots, provided a check upon the potential error associated with different degrees of washing and allow for correction of unwashed combustion/reduction and gas chromatography analyzed roots.在2001年植物生长季期间，以约两周为间隔采集直径5cm、深度20cm的土芯（soil cores）。从每份土芯中分离出羊胡子草（Eriophorum vaginatum）的3个年龄级根系：衰老的灰色根系、栓化的棕色根系以及活跃的白色根系。完成根系提取后，将剩余土芯切割为5段各长4cm的切片，并于根系提取后的1周内完成该切片中残留根系的分拣工作。进行所有后续处理前，所有土芯均置于约5℃的环境中冷藏保存。部分未清洗的根系样品先在70℃下烘干48小时，随后采用燃烧-还原联用法与气相色谱法进行碳氢氮元素分析（使用CHN-1000型仪器，力可公司（LECO Corporation）生产）。另有部分经清洗的根系样品，以及少量未清洗的样品，均采用土壤校正法开展分析（Hunt等，1999）。未清洗的根系被认为保留了根表（rhizoplane）的养分特征。采用土壤校正法对清洗与未清洗的根系样品进行分析，旨在精准估算根系内部的养分浓度，以此校验不同清洗程度可能引入的分析误差，并为经燃烧-还原联用法与气相色谱法分析的未清洗根系样品提供校正依据。