Tree-Ring Research, Volume 75, Issue 2 (Aug 2019)

Two Reconstructions of August-July Precipitation for Central Northern Arizona from Tree Rings

Wed, 07 Aug 2019 00:00:00 GMT

Two Reconstructions of August-July Precipitation for Central Northern Arizona from Tree Rings Fletcher, Tamara; Touchan, Ramzi; Lepley, Kai; Rouini, Nesrine; Bloye, Robert; Tremarelli, Thomas S.; Pena, Kelly; Meko, David M. This study reports two multi-century regional reconstructions of annual precipitation based on Pinus ponderosa and P. edulis from four sites in central northern Arizona. It compares standard regional and time-nested methods to generate reconstructions from 1581-2016 C.E. and 1529-2016 C.E., respectively. The strongest climate relationship is a positive correlation between total ring width and 12-month total precipitation ending in July of the growth year. The chronologies account for 50% of the variance of observed annual precipitation in the regional model and 59%, 60%, and 47% and 35% in the nested models. The two reconstructions are highly correlated (Pearson's correlation r > 0.97, p < 0.001) demonstrating that the reconstructions are highly similar over the period common to both reconstructions, with the nested-model's advantage of extending the range of the reconstruction. The precipitation reconstructions are significantly correlated (r = 0.66, p < 0.001) with the North American Drought Atlas (NADA).

Tree-Ring Expeditions (Trex): Online Labs that Guide Undergrads to Think Like Scientists

Wed, 07 Aug 2019 00:00:00 GMT

Tree-Ring Expeditions (Trex): Online Labs that Guide Undergrads to Think Like Scientists Davi, Nicole; Pringle, Patrick; Lockwood, Jeff; Fiondella, Francesco; Oelkers, Rose Here we describe five publicly available online labs, geared to undergraduate students, which focus on foundational tree-ring research. Students are introduced to basic dendrochronological concepts and practices (Lab 1) while learning about research that has implications for human well-being. Students learn about the way scientists use tree-ring records to reconstruct drought in the Hudson Valley in New York (Lab 2), how tree-ring science began through its utility in putting exact calendar dates on ancestral pueblos (Lab 3), how tree-ring records can be used to put drought into a long-term context, reconstruct streamflow, and better manage water resources (I ab 4), and how tree rings have been used to reconstruct temperatures in the northern latitudes (Lab 5). These labs have the dual aim of guiding students to use many of the same tools as tree-ring scientists, while also giving them a sense of the nature-of-science and how scientists work. Throughout the labs, students are guided to explore virtual field sites, navigate public databanks, observe and measure tree-ring samples, and describe trends and extremes in paleoclimate records. Labs are designed for a 2 to 3-hour lab class and have been classroom-tested and assessed by faculty teams and students.

Towards a More Ecological Dendroecology

Wed, 07 Aug 2019 00:00:00 GMT

Towards a More Ecological Dendroecology Manzanedo, Ruben D.; Pederson, Neil The use of tree-ring methods to study ecological processes, known as dendroecology, has been booming over the last decade. We believe that the incredible methodological strides in this subdiscipline over the last half century will be further advanced by purposefully integrating with other ecological subdisciplines and broadening the scope of dendroecology both in terms of methods and theory. Simultaneously, these efforts will greatly benefit a broad range of ecological disciplines through the incorporation of one of the greatest strengths of dendrochronology: highly-resolved ecological data that spans from seasons to centuries. Because these data are still alarmingly scarce in ecology but are crucial to understand the ecology of long-living organisms, we believe better integrating dendroecology and mainstream ecology will benefit both disciplines. We discuss five actions that can be readily embraced by the dendrochronological community to further advance the field while also making it more open for non-dendroecologists. These actions include: (i) promoting diverse or multi-discipline scientific collaborations and partnerships, (ii) diversifying dendroecological data sources, (iii) incorporating inference-based and hierarchical models to the dendroecological toolbox, (iv) improving and updating the global tree-ring databases, and (v) increasing the focus on ecological and evolutionary mechanisms in tree-ringdriven papers. We believe these actions will help facilitate a broad discussion on how to better integrate tree-ring-based ecology within mainstream ecology. We believe this has the potential to trigger major advancements in dendroecology, help resolve long-standing ecological questions and, ultimately, bring a new perspective and scale to ecological theory.

Seasonal Precipitation Signal in Earlywood and Latewood Ring Width Chronologies of Pinus Roxburghii

Wed, 07 Aug 2019 00:00:00 GMT

Seasonal Precipitation Signal in Earlywood and Latewood Ring Width Chronologies of Pinus Roxburghii Nautiyal, A.; Rawat, G. S.; Ramesh, K.; Kannan, R.; Stephenson, S. L. The growth response of earlywood and latewood to precipitation in chir pine (Pinus roxburghii) was studied by examining a series of core samples from the Garhwal Himalaya, India. Earlywood and latewood were observed to contribute about equal proportions towards the total ring width. Comparison of tree-ring data with the CRU TS3.22 (land) precipitation dataset indicates that earlywood is positively correlated with spring and early summer precipitation, whereas latewood is negatively correlated with pre-monsoon and early monsoon precipitation. This seasonally-reversed climate signal is confirmed when regional weather station precipitation data were used. A similar seasonally reversed climate response was found in earlywood and latewood of two datasets obtained from core samples from two other sites located in Nepal and Bhutan. Because chir pine is a light-demanding species, light limitation during the monsoon season could be an important factor behind the negative correlation between latewood and precipitation. NOAA NCEP-NCAR low cloud data were used to test this hypothesis, and the preliminary results support the hypothesis; however, further analysis will be needed to fully validate this hypothesis.