Bristlecone Pine Maximum Latewood Density from the California White Mountains and March-to-September Temperature Reconstruction for American Southwest

Bristlecone pine (Pinus longaeva) (PILO) trees have an exceptional longevity. Their tree-ring width (TRW) series offer valuable insights into climatic variability. Maximum latewood density (MXD) typically correlates better with temperature variations than TRW, yet PILO MXD records are non-existent due to methodological challenges related to their tree-ring structure. Here, we used an X-ray Computed Tomography (X-ray CT) toolchain on 51 PILO cores from the California White Mountains to build a chronology that correlates significantly (r=0.66, p&lt;0.01) with warm-season (March-September) temperature over a large spatial extent. This led to the first X-ray CT-based temperature reconstruction (1625 – 2005 CE). Good reconstruction skill (RE=0.51, CE=0.32) shows that extending MXD records across the full length of the PILO archive could yield a robust warm-season temperature proxy for the American Southwest over millennia. This breakthrough opens avenues for measuring MXD in other challenging conifers, increasing our understanding of past climate further, particularly into the lower latitudes.<br>MAMJJAS_Tmean_reconstruction.txt - March-to-September mean temperature reconstruction for American Southwest (35° - 38° N; 119° - 115° W) based on the maximum latewood density of bristlecone pines from the California White MountainsPILO_MXD_RAW.rwl - raw measurements of the maximum latewood density of bristlecone pines from the California White Mountains derived from X-ray Computed TomographyPILO_MXD_chronology.txt - standardized chronology for maximum latewood density of bristlecone pines from the California White Mountains derived from X-ray Computed Tomography Matlab scripts folder contains scripts and related files to generate figures 2a,b,c, 3, 4 of the paper

大盆地狐尾松（Pinus longaeva，PILO）拥有极长的寿命，其树轮宽度（tree-ring width, TRW）序列可为气候变率研究提供极具价值的视角。相较于TRW，最大晚材密度（maximum latewood density, MXD）通常与温度变化的相关性更强，但受限于狐尾松树轮结构相关的方法学难题，目前尚无PILO的MXD相关记录。本研究针对采自加利福尼亚怀特山脉的51个PILO树芯，采用X射线计算机断层扫描（X-ray Computed Tomography, X-ray CT）技术流程，构建了一条在大空间尺度上与暖季（3月至9月）温度呈显著相关的年表（相关系数r=0.66，p<0.01）。借此，我们完成了首项基于X射线CT的温度重建（公元1625年—2005年）。重建结果展现出优异的性能（RE=0.51，CE=0.32），表明若能完整获取PILO档案中的MXD记录，即可构建出可用于追溯数千年来美国西南部暖季温度的可靠代用指标。这一突破为在其他具有研究挑战的针叶树种中开展MXD测量开辟了新路径，有助于进一步深化我们对过去气候的认知，尤其是在低纬度区域。
MAMJJAS_Tmean_reconstruction.txt —— 基于加利福尼亚怀特山脉狐尾松最大晚材密度的美国西南部（北纬35°—38°；西经119°—115°）3月至9月平均温度重建数据文件
PILO_MXD_RAW.rwl —— 经X射线计算机断层扫描获取的加利福尼亚怀特山脉狐尾松最大晚材密度原始测量数据文件
PILO_MXD_chronology.txt —— 经X射线计算机断层扫描获取的加利福尼亚怀特山脉狐尾松最大晚材密度标准化年表文件
Matlab脚本文件夹包含用于生成论文中图2a、2b、2c、3、4的脚本及相关配套文件