Drivers of twoneedle pinyon (Pinus edulis) cone productivity: implication for wildlife

Data pertaining to Chapter 2 "Drivers of twoneedle pinyon (Pinus edulis) cone productivity: implication for wildlife" of a New Mexico State University (Las Cruces) Master's thesis by Clare O'Connell titled: THE OSCURA MOUNTAINS COLORADO CHIPMUNK: EVALUATION OF MICROHABITAT SELECTION AND ECOLOGICAL DRIVERS IN PINYON-JUNIPER WOODLAND.

Abstract: Seeds of twoneedle pinyon (Pinus edulis) serve as a nutritionally dense food resource for myriad of wildlife. Pinyons exhibit synchronist masting with high cone production occurring every 4-7 years. Per-tree cone production may be influenced by tree-level and site-level features. Our goal was to identify features that influence pinyon cone abundance and determine how cone production relates to microhabitat selection by the Oscura Mountains Colorado chipmunk (Neotamias quadrivittatus oscuraensis), an old growth pinyon-juniper specialist and seed-caching rodent. We hypothesized increased cone abundance would be exhibited by older trees and at sites with increased water availability. We hypothesized that the chipmunk would select stands exhibiting increased cone production. We used double observer abscission scar counts on five branches per tree averaged between observers to estimate tree cone abundance for the most recent eight years. We used linear modeling to determine tree- and site-level features influencing per tree cone abundance, incorporating site as a random-intercept for tree-level models. The most influential tree-level feature was diameter, with larger diameter trees having greatest cone abundance. Percent defoliation in the living tree canopy exhibited an inverse relationship with cone abundance. Water availability of a site was represented by reproductive tree density and heat load, both of which inversely influenced per-tree cone abundance. However, reproductive tree density exhibited a positive relationship with cone production across a stand. Estimated stand cone production did not influence microhabitat selection by the chipmunk. We encourage management of pinyon-juniper woodlands to consider drivers of pinyon cone productivity and influence of cone production on wildlife. We urge the protection of old growth stands to support wildlife, as older trees are the most influential determinant of cone abundance and concurrently provide structural complexity important for wildlife. Lastly, our study indicates thinning of pinyon-juniper woodlands as unwarranted for the goal of increasing cone production. Maximizing pinyon cone production would be best met by maintaining dense old growth stands.

本数据集关联新墨西哥州立大学（拉斯克鲁塞斯分校）克莱尔·奥康奈尔（Clare O'Connell）题为《奥库拉山科罗拉多花鼠：杜松-松林地微生境选择及生态驱动因子评估》的硕士论文第2章“二针松（Pinus edulis）球果产量驱动因子：对野生动物的意义”。

摘要：二针松（Pinus edulis）的种子是众多野生动物营养丰富的食物资源。松类植物存在同步结实现象，每4至7年会出现一次高球果产量周期。单株树的球果产量可能受树木自身特征及立地特征的影响。本研究旨在识别影响松类球果丰度的因子，并明确球果产量与奥库拉山科罗拉多花鼠（Neotamias quadrivittatus oscuraensis）——一种老龄杜松-松林特化种及贮食啮齿类——的微生境选择之间的关联。我们提出两项假说：其一，老龄树木及水分可利用性更高的立地，其球果丰度更高；其二，花鼠会选择球果产量更高的林分。本研究通过对每株树的5根枝条进行双观察者脱落痕计数，取两位观察者的平均值，以此估算过去8年的单株球果丰度。我们采用线性建模分析影响单株球果丰度的树木及立地特征，其中树木水平模型将立地设为随机截距项。影响力最强的树木特征为胸径，胸径更大的树木球果丰度最高。活冠层的落叶率与球果丰度呈负相关。立地的水分可利用性以结实树木密度与热负荷表征，二者均与单株球果丰度呈负相关，但就林分整体而言，结实树木密度与球果产量呈正相关。估算的林分球果产量并未对花鼠的微生境选择产生影响。我们建议杜松-松林地的管理工作应考虑松类球果产量的驱动因子，以及球果产量对野生动物的影响。我们呼吁对老龄林分进行保护以支持野生动物种群，因为老龄树木既是球果丰度最关键的决定因子，同时也能为野生动物提供重要的结构复杂性栖息地。最后，本研究表明，以提升球果产量为目标而对杜松-松林地进行疏伐是不必要的。若要最大化二针松的球果产量，最佳策略是维持高密度的老龄林分。