Floodplain Forest Seedling Survival through Dormant Season Flooding: A Controlled Experiment

These data are associated with a controlled experiment that subjected approximately seven-month-old seedlings of <i>Nyssa aquatica</i>, <i>Nyssa ogeche</i>, <i>Fraxinus caroliniana</i>, <i>Carya aquatica</i>, and <i>Quercus lyrata </i>to treatments ranging between one and four months of complete submergence in water. The treatments and timing of the experiment simulate winter flooding commonly experienced in the Apalachicola River floodplain of Florida, USA where these species dominate neighboring forest types (swamp and low bottomland) whose distributions compete due to climatic and anthropogenic influences on hydrologic regimes. Following prior experimentation in 2022 that aimed to investigate differences in first-year seedling performance of swamp and low bottomland hardwood species from the Apalachicola floodplain under varying moisture regimes, we utilized the remaining approximately seven-month-old seedlings from a low-stress treatment. All seedlings were grown from seeds collected directly from the floodplain except for <i>Nyssa aquatica</i>, whose seeds were purchased from the Louisiana Forest Seed Company. One-gallon GroPro® black plastic grow bags were used to contain the seedlings. The soil column for each bag consisted of 7.5 cm of commercially available peaty topsoil in the top half and another 7.5 cm of commercially available loamy mix topsoil in the bottom half of the column. See the "Prior Seedling Experiment Data" file to view seedling heights above the root collar before experimentation. Treatments occurred in a single circular Intex 28131EH plastic/PVC above-ground pool measuring 3.65 m in diameter and 76.2 cm in height with a capacity of 5,621 liters. The pool was filled with local untreated well water and monitored four times periodically for pH, dissolved oxygen concentration (mg/L), and turbidity (NTU) using an Aqua TROLL 500. See the "Water Quality Monitoring" file for observations over the experiment period. The experiment occurred in an open environment where ambient temperatures and precipitation could influence the treatments. See the "PNS_airport_weather" file for local weather data. The experiment involved three replicates of four test treatments and two replicates of a control treatment. The control treatments were only used to check for unexpected mortality during the experiment, and analysis was only performed on the four test treatments resulting in a randomized complete block design. Each species had varying sample sizes (n) in each treatment and block due to a lack of seedling availability. Only general observations were made for <i>Nyssa ogeche</i> in all treatments and <i>Nyssa aquatica</i> in treatments two and three. Any seedlings whose terminal buds could not be covered during test treatments were also omitted from the analysis. See the "Dormant Season Flooding_Seedling Data" file for all seedling observations throughout the experiment. The total survival of each species in each treatment and block was calculated at the end of the experiment. A pairwise Fisher exact test was then performed to identify significant differences among the average survival of each species and each treatment at the end of the experiment. The cumulative number of individuals flushing leaves was tallied each week after treatments and until the end of the experiment to identify potential signs of stress or delayed flushing due to the treatments. To compare the effect of treatments on the timing and rate of leaf-flushing individuals among species, multiple dose-response curve models were constructed to find the best fit to the data. Models were ranked using Akaike's information criterion and once the best-fit model was selected, a likelihood ratio test was used to assess the effect of treatment on cumulative flushing individuals. If a significant p-value was returned, then pairwise comparisons of species using the Tukey adjustment for multiple comparisons were constructed. The hill slope parameter was used for comparisons of leaf flushing rates and the half-maximal effective concentration, or EC50 parameter, was used for comparisons of timing to reach 50% of total flushing individuals. All analyses were performed in R. See the "Dormant Season Flooding_Seedling Experiment" R file for analyses using the data files.These files are associated with a manuscript prepared for submission to a peer-reviewed journal.

本数据集关联一项受控实验，该实验对约7月龄的<i>Nyssa aquatica</i>（美国水紫树）、<i>Nyssa ogeche</i>（奥基乔比水紫树）、<i>Fraxinus caroliniana</i>（卡罗莱纳白蜡）、<i>Carya aquatica</i>（水生山核桃）及<i>Quercus lyrata</i>（琴叶栎）幼苗施以时长1至4个月的完全水淹处理。本次实验的处理方式与时间设置，模拟了美国佛罗里达州阿巴拉契科拉河泛滥平原常见的冬季洪水情境；该区域内上述物种是邻近森林群落（沼泽与低地河漫滩林）的优势种，而这些群落的分布范围因气候与人类活动对水文格局的影响而相互竞争。本实验基于2022年的先期实验开展，该先期实验旨在探究阿巴拉契科拉河泛滥平原的沼泽与低地河漫滩硬木树种一年生幼苗在不同水分条件下的生长表现差异。本次实验使用了先期实验中低胁迫处理组剩余的约7月龄幼苗。所有幼苗均由直接采自泛滥平原的种子培育而来，仅<i>Nyssa aquatica</i>的种子购自路易斯安那林业种子公司（Louisiana Forest Seed Company）。实验采用1加仑容量的GroPro®黑色塑料种植袋培育幼苗。每个种植袋的土壤柱分为上下两层：上层为7.5 cm市售泥炭质表层土，下层为7.5 cm市售壤土混合表层土。可查阅"Prior Seedling Experiment Data"文件，获取实验前幼苗根颈以上的株高数据。所有水淹处理均在单个圆形Intex 28131EH型塑料/PVC地上水池中开展，该水池直径3.65 m，高76.2 cm，容积为5621升。水池注入当地未经处理的井水，并使用Aqua TROLL 500型设备定期四次监测水体pH值、溶解氧浓度（mg/L）与浊度（NTU）。实验期间的水质监测数据可查阅"Water Quality Monitoring"文件。实验置于开放环境中开展，环境温度与降水可能对处理组产生影响。当地气象数据可查阅"PNS_airport_weather"文件。实验包含4种处理组，每组设置3次重复；另设置2次重复的对照组。对照组仅用于监测实验期间的非预期死亡率，后续分析仅针对4种处理组展开，实验设计为随机完全区组设计。由于幼苗资源有限，各物种在各处理组与区组中的样本量（n）存在差异。仅对所有处理组中的<i>Nyssa ogeche</i>，以及处理组2与3中的<i>Nyssa aquatica</i>进行了一般性观测。在处理过程中顶芽无法被覆盖的幼苗，也被排除在分析之外。实验期间所有幼苗的观测数据可查阅"Dormant Season Flooding_Seedling Data"文件。实验结束时，计算各物种在各处理组与区组中的总存活率。随后采用两两Fisher精确检验，识别各物种与各处理组平均存活率间的显著差异。自处理实施后至实验结束，每周统计展叶个体的累计数量，以判断是否存在由水淹处理引发的胁迫或展叶延迟现象。为比较不同处理对各物种展叶时间与展叶速率的影响，本研究构建了多种剂量-响应曲线模型，以筛选与数据拟合度最优的模型。模型的优劣通过赤池信息准则（Akaike's Information Criterion, AIC）进行排序。选定最优拟合模型后，采用似然比检验评估处理对累计展叶个体数的影响。若检验得到显著p值，则使用Tukey多重比较校正法开展物种间的两两比较。本研究以希尔斜率参数（hill slope parameter）比较展叶速率，以半最大效应浓度（half-maximal effective concentration, EC50）参数比较达到50%总展叶个体的时间。所有分析均在R语言环境中完成。使用数据集开展的分析代码可查阅"Dormant Season Flooding_Seedling Experiment" R文件。本数据集关联一篇拟投送至同行评议期刊的研究论文。