Macroscale Variation in Red Maple (Acer rubrum) Foliar Carbon, Nitrogen, and Nitrogen Resorption

Project Description The primary goal of this project was to investigate intraspecific variation of foliar nitrogen resorption for Acer rubrum (red maple). In particular, we are interested in examining whether foliar nutrient resorption is related to climatic factors such as mean annual temperature and/or precipitation. The approach used to collect green and fallen leaf samples was through a community science project where participants sent leaves to our lab at Boston University for analysis. In the spring/summer of 2019 plant and naturalist organizations throughout the range of red maple in the United States were contacted to request information about this project be sent to their members regarding the collection of red maple leaves for the study. Interested parties were prompted to complete a google form that included basic contact information. Each participant was then sent a sampling kit which included gloves, sampling protocols, and data sheets. For each set of leaves collected from a single tree they were assigned the following identification “tasper-###” where the numbers were uniquely assigned. Green and fallen leaves were assigned different “tasper-###” numbers. Within a single identification (e.g., tasper-120) each leaf was individually assigned a letter a-n, where n corresponds to the letter of how many leaves were sent from that tree. For most samples a-j was obtained because we asked participants to collect 10 leaves. Individual leaves were scanned for area analysis using a flatbed scanner at 300 dpi and weighed. For C&N analysis each leaf blade from a set of green or fallen leaves from a single tree was hole-punched and the samples were combined yielding one C and N concentration per tree for both each green and fallen leaves. Punches were ground and homogenized to a powder using a mortar and pestle. Approximately 3 mg of dried sample was analyzed for C and N concentration using a NC2500 elemental analyzer (CE Elantech, Lakewood, NJ, USA). NIST Apple Leaves were used as standard reference material.

项目概述
本项目的核心目标为探究红花槭（Acer rubrum，俗称红枫）的叶氮回收种内变异规律，重点考察叶片养分回收与年平均气温、降水量等气候因子的相关性。
本研究通过公民科学项目采集鲜叶与落叶样本，参与者需将采集的叶片寄送至波士顿大学实验室开展分析。2019年春夏两季，研究团队联系了美国境内红花槭分布范围内的所有植物与博物学爱好者组织，请求将本研究的红花槭叶片采集相关信息传达至其成员。有意愿参与的人员需填写谷歌表单以提供基础联系方式。随后，每位参与者将收到一套采样工具包，内含手套、采样规程与数据记录表。
针对从单棵树木采集的一组叶片，将为其分配格式为"tasper-###"的唯一标识，其中数字部分为专属编号。鲜叶与落叶将被分配不同的"tasper-###"编号。在同一标识（如tasper-120）下，每一片叶片将被单独分配a至n的字母编号，n的取值对应该树木寄送的叶片总数。由于研究要求参与者采集10片叶片，多数样本仅使用a-j共10个字母编号。
研究人员使用平板扫描仪以300dpi的分辨率对单叶进行扫描，用于叶面积分析，并称量单叶重量。针对碳（C）与氮（N）含量分析，研究人员将从单棵树木的鲜叶组或落叶组中，取下每片叶的叶肉打孔样本，将同组样本混合后，得到该树木鲜叶与落叶各自的碳、氮浓度数据。打孔样本经研磨后，使用研钵与研杵均质为粉末状。称取约3毫克干燥后的样本，使用NC2500元素分析仪（CE Elantech公司，美国新泽西州莱克伍德市）进行碳、氮浓度检测。实验采用美国国家标准与技术研究院（NIST）的苹果叶作为标准参考物质。