Data_Sheet_1_Variation in Bark Allocation and Rugosity Across Seven Co-occurring Southeastern US Tree Species.xlsx

Bark is a complex multifunctional structure of woody plants that varies widely among species. Thick bark is a primary trait that can protect trees from heat generated in surface fires. Outer bark on species that allocate resources to thick bark also tends to be rugose, with bark being thickest at the ridges and thinnest in the furrows. Tree diameter or wood diameter is often used as a predictor for bark thickness but little attention has been made on other factors that might affect bark development and allocation. Here we test multiple mixed effect models to evaluate additional factors (height growth rate, measure height) that correlate with bark allocation and present a method to quantify bark rugosity. We focused on seven co-occurring native tree species in the Tallahatchie Experimental Forest in north Mississippi. Approximately ten saplings of Carya tomentosa, Nyssa sylvatica, Prunus serotina, Pinus echinata, Pinus taeda, Quercus marilandica, and Quercus falcata were destructively sampled for stem analyses. Outer bark thickness (OBT) ranged from 0.01 to 0.77 cm with the thickest maximum outer bark occurring on P. taeda (0.77 cm) and the thinnest maximum outer bark occurring on P. serotina (0.17 cm). Our outer bark allocation models suggest that some individuals with rapid height growth allocate less to outer bark in C. tomentosa, N. sylvatica, P. taeda, and P. serotina, but not for P. echinata or either oak species. All species except for C. tomentosa and N. sylvatica showed evidence for outer bark taper, allocating more outer bark at the base of the bole. Inner bark also was tapered in Carya and the oaks. Bark rugosity varied among species from 0.00 (very smooth) to 0.17 (very rugose) with P. Serotina and C. tomentosa having the smoothest bark. OBT was the best fixed effect for all species. Aside from providing data for several important yet understudied species, our rugosity measures offer promise for incorporating into fluid dynamics fire behavior models.

树皮（Bark）是木本植物的复杂多功能结构，在不同物种间差异显著。厚树皮是保护树木免受地表火产生的热量侵害的核心性状。将资源分配至厚树皮的物种，其外树皮通常呈褶皱状，脊部树皮最厚，沟谷处最薄。树木直径或木质部直径常被用作预测树皮厚度的指标，但针对其他可能影响树皮发育与资源分配的因素的研究却相对匮乏。本研究构建了多个混合效应模型，以评估与树皮资源分配相关的额外因素（高生长速率、测量树高），并提出了一种量化树皮褶皱程度的方法。研究聚焦于密西西比州北部塔拉哈奇实验林（Tallahatchie Experimental Forest）中7种同期共存的本土树种：毛山核桃（Carya tomentosa）、多花紫树（Nyssa sylvatica）、野樱桃（Prunus serotina）、短叶松（Pinus echinata）、火炬松（Pinus taeda）、马里兰栎（Quercus marilandica）以及垂枝栎（Quercus falcata）。我们对每个物种的约10株幼树进行了破坏性采样以开展茎干分析。外树皮厚度（outer bark thickness, OBT）的范围为0.01~0.77 cm，其中最大外树皮厚度最厚的为火炬松（0.77 cm），最薄的为野樱桃（0.17 cm）。我们的外树皮分配模型显示，在毛山核桃、多花紫树、火炬松以及野樱桃中，部分高生长速率较快的个体对外树皮的资源分配更少，但这一规律并不适用于短叶松或两种栎属树种。除毛山核桃和多花紫树外，其余所有物种均表现出外树皮厚度呈梯度变化的特征，即在树干基部分配更多外树皮。山核桃属和栎属树种的内树皮同样存在沿树干的厚度梯度变化。树皮褶皱程度在不同物种间的取值范围为0.00（极光滑）至0.17（极褶皱），野樱桃与毛山核桃的树皮最为光滑。外树皮厚度是所有物种拟合模型中最优的固定效应因子。本研究不仅为多个重要但尚未得到充分研究的树种提供了基础数据，其提出的树皮褶皱程度量化方法也有望被纳入流体动力学火行为模型之中。