NOAA/WDS Paleoclimatology - DeRose - Card Canyon - JUOS - ITRDB UT542

Utah juniper was a foundational species for the discipline of dendrochronology, having been used in the early 20th Century investigations of Mesa Verde, but has been largely ignored by dendrochronologists since. Here we present dendrochronological investigations of Utah juniper core and cross-sectional samples from four sites in northern Utah. We demonstrate that, contrary to the general opinion among many dendrochronologists, Utah juniper exhibits excellent crossdating that is reflective of its sensitivity to climate — a desirable characteristic for dendroclimate reconstruction. Across all four sites the dominant signal for annual ring-width increment occurred during the growing season and was positive for precipitation and negative for temperature. This corroborates ecophysiological studies that highlight Utah juniper’s aggressive water-use behavior and desiccation tolerance that together enable survival at extremely negative soil water potentials. This behavior differs from co-occurring Pinus spp. (i.e. P. edulis and P. monophylla) that avoid cavitation at the cost of carbon starvation. We determine that the annual radial increment of Utah juniper rings is particularly responsive to soil moisture availability, and is in fact a useful proxy for hydroclimatic variables such as precipitation, drought, and streamflow. Its geographic distribution spans a large swath of the Interior West, including areas where other more commonly sought-after species for dendrochronology do not occur, and ought to be considered crucial for complementing the rich network of tree-ring chronologies in the western U.S.

犹他杜松（Utah juniper）曾是树木年代学（dendrochronology）的核心研究物种，早在20世纪初期便被应用于梅萨维德（Mesa Verde）的相关考察，但此后却长期被树木年代学家们所忽视。本研究针对犹他州北部4个采样点的犹他杜松钻芯与横截样本开展树木年代学研究。研究结果显示，与多数树木年代学家的普遍观点相悖，犹他杜松具备优异的交叉定年（crossdating）能力，该特性反映出其对气候的敏感性——而这正是树木气候重建（dendroclimate reconstruction）所需的理想特征。在全部4个采样点中，年轮宽度增量的主导气候信号均出现在生长季，且与降水量呈正相关、与气温呈负相关。这一结果印证了生理生态学研究的结论：此类研究揭示了犹他杜松高效的水分利用策略与脱水耐受（desiccation tolerance）能力，二者共同使其能够在极低土壤水势下存活。该生存策略与同域分布的松属（Pinus）物种（即二针松P. edulis与单叶松P. monophylla）截然不同，后者以碳饥饿为代价避免木质部空穴化（cavitation）。本研究证实，犹他杜松的年轮径向年增量对土壤水分可利用性尤为敏感，实际上可作为降水、干旱与径流等水文气候变量的有效代用指标（proxy）。犹他杜松的地理分布范围覆盖美国内陆西部大片区域，其中包含了其他常用于树木年代学研究的树种无法生长的地带，因此该物种应被视为补充美国西部丰富树轮年代序列网络的关键研究资源。