Tree-Ring Talks and Tours Day

Wednesday, April 1, 2015

11:00–12:00 Docent-led tours of the Tree-Ring building

12:00–12:30 Tree-ring lab potluck lunch

12:30–1:15 Short Talk Session I

1. On the importance of the monsoon rainfall for Ponderosa pine growth throughout the US Southwest. Paul Szejner

Monsoon rainfall plays an important role sustaining different types of ecosystems in the Southwestern US. The arrival of the monsoon breaks the early summer hyper-arid period in the region providing unique seasonal conditions for these ecosystems to thrive. It is unknown to what extent monsoon rainfall is used by Ponderosa pine forests, which occupy many mountain ecosystems in the Western US. While these forests clearly rely on winter snowpack to drive much of their annual net primary productivity, the extent to which they supplement winter moisture, with summer monsoon moisture needs to be clarified. Furthermore, it is likely that there are north-to-south gradients in forests reliance on monsoon moisture, as the summer monsoon system tends to become diminished in the region between Tucson and Salt Lake City. We addressed these gaps in our knowledge about the monsoon by studying carbon and oxygen stable isotopes in the earlywood and latewood from cores taken from trees in ten sites along a latitudinal gradient in Arizona, New Mexico and Utah. Here we show evidence that Ponderosa trees from these sites use monsoon water to support growth during the late summer. And the use of monsoon precipitation was strongest in the southernmost sites. This study provides new insight on the influence of the North American monsoon and winter precipitation on Ponderosa growth. Suggesting that differences in water sourcing between southern and northern Ponderosa forest might have strong implications on the forest response under climate change projections.

2. North Pacific jet stream climatology. Soumaya Belmecheri

Jet streams, narrow bands of strong winds are important modulators of long term climate trends (regional scale climate patterns) and extreme weather (short term meteorology) in the northern hemisphere mid-latitudes. The position and strength of jet streams are used for short-term weather forecast. However, on longer-time scales, uncertainty about their climatology hinders their use for longer-term climate projections. In the present study, we aim at establishing the climatology of the North pacific Jet stream (NPJ) which strongly modulates hydroclimatology in North America. We will investigate the instrumental period using Twentieth Century Re-analysis data covering a period from 1930–2012 at 2×2 degree spatial resolution to identify homogeneous NPJ regions. The mean position and strength at seasonal scale will then be used to examine spatio-temporal (intermediate-scale) NPJ characteristics.

3. Dendroclimatology and wheat production in Algeria. Ramzi Touchan

Drought in North Africa and specifically in Algeria is a recurring phenomenon. Prolonged drought in this arid to semi-arid region could be one of the main natural factors in causing a decline in tree-growth and agricultural crops in Algeria. The presentation will addresses the variability of growing conditions for wheat in Algeria with climatic data and a tree-ring reconstruction of January–June precipitation from ten Pinus halepensis tree-ring chronologies.

4. The Central American Dendroecological Fieldweek, Sierra de los Cuchumatanes, Guatemala. Becky Brice

The first Central American Dendroecological Fieldweek (CADEF) met in March of this year in the Cuchumatanes Mountains of central Guatemala. The fieldweek is a unique combination of hands-on education in the context of NSF funded research projects and intended to bring together Central American and North American scientists, students, and natural resources managers interested in dendrochronology. CADEF is co-organized by Woods Hole Oceanographic Institute, the University of Denver, and the Center for Environmental Studies and Biodiversity at the Universidad del Valle, Guatemala, and is supported by a grant from the National Science Foundation. For students in particular, CADEF is an opportunity to network and get international research experience. Results and experiences from this week-long intensive study will be presented.

5. Can money grow on trees? Exploring access and governance in Guatemala's forestry incentive programs. Niki VonHedemann

Payments for Ecosystem Services (PES) programs are an emergent form of environmental governance that aim to provide motivation for environmental protection and, often, funds for local development. Many of these programs, which incentivize conservation activities through payments to those who own or manage land, focus on forested areas. State-run Guatemalan forestry incentive programs are rapidly expanding as landowners’ interest increases and forest growth and conservation are sought by the Guatemalan government. Participants in the Western Highlands of Guatemala have often worked on forest conservation for decades, seizing the opportunity to receive payments for their efforts and mobilizing community organization to enroll. However, tensions remain between state-dictated forest conservation techniques coupled to payments and traditions of volunteerism surrounding forest governance. This study investigates the social impacts of receiving economic incentives for conservation on access, management, and governance of forests in the Western Highlands of Guatemala. These compensations for landowners providing essential ecosystem services are growing at the same time that Guatemala is also introducing Reducing Emissions from Deforestation and Forest Degradation (REDD+) initiatives, which seek to provide international funds for forest carbon sequestration across the globe.

6. The influence of drought on fire severity. Emma Williams

Increasing mortality rates and rapid forest die back, measured in western conifer forests during the past several decades, is of major land management concern. These trends have been largely attributed to climatic warming and limited precipitation. The National Park Service fire effects monitoring program provides an opportunity to study the response of trees to prescribed fire following intermediate term drought. Pre and post burn tree data, along with growth trend analysis, may provide evidence of how drought influences fire sensitivities in southwest conifers.

7. How to win friends and influence enemies while analyzing your fire history FHX data in R. Steven Brewster Malevich

Fire history data can be complex and cumbersome, requiring manual parsing and preening to create the most basic plots and analysis. This talk will describe an ongoing effort to make fire history data accessible to the increasingly popular R statistical programming language. The talk will cover basic input-output, concatenation, and plotting of FHX data in R. After you watch this talk, your friends and family will be amazed at your ability to script cutting-edge fire-history workflows with the R language.

1:15–1:25 Cookie break

1:25–3:00 Short Talk Session II

8. Secrets of the Extreme Events Lab. Katie Hirschboeck

What goes on in the mysterious Extreme Events Lab on the Third Floor of the Bannister Tree-Ring Building? This short talk will present a brief overview of the diverse activities going on “behind the glass windows” by those affiliated with the Extreme Events Lab. You’ll hear about research on floods, atmospheric rivers, snow, and more! The Extreme Events Lab’s Arizona Flood Project will be unveiled and there will also be a preview of the soon-to-be-launched SWANN Project (Snow-Water Artificial Neural Network). An update on past activities related to frost rings and extreme streamflow variations will also be given.

9. Secrets of the Extreme Events Lab II: Relevance of flood hydroclimatology in Arizona. Diana Zamora-Reyes

In the United States, the flood frequency analysis guidelines described in Bulletin 17B are followed to provide reliable flood discharge magnitude estimates. The statistical analysis in Bulletin 17B has various assumptions, including that floods are generated by the same type of atmospheric mechanism (flood homogeneity). However, these assumptions should be carefully assessed before proceeding since they might not always be valid and could increase the potential for flood risk. This short talk will present a brief overview on flood frequency analysis from the perspective of flood heterogeneity, the hydrometeorological genesis of each flood event, and how such analysis can help produce the most accurate discharge estimates possible.

10. Breaking the low-frequency ceiling in tree-ring reconstruction of streamflow with riparian trees. David Meko

Tree-ring reconstructions from ring widths of upland trees are a longstanding source of information on variability of streamflow. Such trees sense variations in net precipitation in runoff-producing parts of a watershed. Such reconstruction can explain much of the variance of annual and seasonal-total streamflow series, but low-frequency signal may be missing or distorted due to detrending operations in standardizing the ring widths. Large stands of riparian trees may in some settings may offer the chance to circumvent this limitation. Ring widths of more than 300 plains cottonwood (Populus deltoides, ssp. monilifera) trees in the North Unit of Theodore Roosevelt National Park, North Dakota, are applied to illustrate this idea in a study of streamflow along the Little Missouri River, North Dakota, USA.

11. Where does the carbon go? Insights into carbon allocation from tree rings. M. Ross Alexander

The movement of carbon dioxide between the atmosphere and the biosphere is measured by eddy-covariance systems. These measurement systems are well suited for measuring carbon transport at hourly to daily timescales but less accurately capture annual accumulation. In contrast, trees produce annual rings, composed of carbon, that act as a record of environmental over the growing season, and store this information for decades or even centuries. Reconstructions of biomass from these tree rings provide information of annual aboveground carbon storage over long time periods for which there are no eddy-covariance measurements. Therefore, we have reconstructed the aboveground biomass in a Midwest temperate deciduous forest and compared tree-ring-derived estimates of aboveground biomass with the net ecosystem productivity (NEP) measured by an eddy-covariance tower. On average, 70% of the NEP measured by eddy-covariance towers was stored in aboveground biomass, but interannual carbon storage varied greatly (49% – 90%) over the length of the tower flux record. We determined the influence of climate over annual growth by correlating tree-ring data with a long-term climate data and found that growth correlated positively with summer (June, July, August) precipitation and negatively with summer incoming shortwave radiation. These results indicate that growth in this forest is controlled by summer precipitation, as incoming shortwave radiation is reduced by cloud cover during precipitation events. This forest receives almost 111cm of rain annually and is not thought to be precipitation-limited, therefore we would expect temperature or ecological competition to be the primary driver of growth. However, no significant relationship was found with either temperature or relative humidity. Our results suggest that we could see eastern deciduous forests becoming more productive by the end of the century under the hotter and wetter conditions predicted by climate models for the eastern United States.

12. Diameter corrections for 13 important forest species in the Madrean Archipelago and southwestern US. Jesse Minor

Diameter corrections are provided for 13 forest and woodland tree species common across higher elevations of the Southwestern United States and the Sierra Madre. Standardized measurement is crucial to many forest analyses, but prior natural and anthropogenic disturbance frequently leave legacy wood that cannot be measured at nominal breast height. Correction factors based on linear regression are provided for conversion of stump height and root crown diameter measurements into diameter breast height for 13 commonly encountered species drawn from six genera. Using these correction factors, diameter measurements taken at standard stump height and root crown height can be corrected to diameter at breast height. Species considered in this analysis are Abies concolor (White Fir), Juniperus deppeana (Alligator Bark Juniper), Pinus ponderosa var. arizonica (Arizona Pine), Pinus discolor (Border Pinyon), Pinus engelmannii (Apache Pine), Pinus leophylla (Chihuahua Pine), Pinus ponderosa (Ponderosa Pine), Pinus stobiformus (Southwestern White Pine), Populus tremuloides (Quaking Aspen), Pseudotsuga menziesii (Douglas-Fir), Quercus arizonica (Arizona White Oak), Quercus gambelii (Gambel Oak), and Quercus hypoleucoides (Silverleaf Oak). In addition, correction factors based on linear regressions are provided for the six combined Pinus and the three combined Quercus species.

13. Wood anatomy, dendrochronological applications, and carbon allocation in velvet mesquite (Prosopis velutina Woot.). Rob Shepard

Velvet mesquite is one of the main trees that inhabit the Sonoran Desert Ecosystem. By using wood anatomical features to describe growth rings, we begin to explore its use in dendrochronological applications. Wood anatomy study showed that the growth ring shows many characteristics of a tree that puts in annual rings. Cross-dating shows some datability and the relationship of ring size to environmental stimuli needs to be explored. This tree could be the key to a new chapter of southwestern dendrochronoloy.

14. Detecting false latewood bands from reflected blue light measurements. Flurin Babst

Radial tree growth in arid environments tends to slow down or even temporarily cease under strong drought conditions resulting in characteristic wood anatomical features called “false latewood bands” (FLB) in conifers. In the US Southwest, FLBs can occur almost every year in trees growing at stressed sites and this layer of thick-walled cells is usually associated with a pre-summer drought period that precedes the onset of the summer monsoon. While FLBs have often been used as a time marker in this context, the exact environmental conditions shaping them are poorly understood. This is because traditional dendrochronological measures such as early- and latewood width or density do not explicitly isolate them. As FLBs are essentially wood density fluctuations, high-resolution density profiles should allow detecting and characterizing them. To do this, we used the reflected blue light method that provides a surrogate measure of wood density from high-resolution optical scans of the wood surface. We analyzed the pseudo-density profiles of each ring over the 1985–2014 period from twenty Pinus ponderosa trees growing at two sites in the Santa Catalina and the Pinaleño Mountains. The position, height, and width of the FLBs — identified as the second highest density peak after the real latewood — were assessed and compared to several climate variables measured at local meteorological stations. This approach helps to better understand the environmental drivers of FLB formation in Pinus ponderosa and extends current knowledge of seasonal water use strategies of forests in arid environments.

15. Dendroarchaeology of the Otero Cabin, Valles Caldera National Preserve, New Mexico. Rebecca Renteria

The Valles Caldera National Preserve in northern New Mexico has been the site of many culture group activities from prehistoric to present times due to its exceptionally resource-rich environment. During the early 20th century, profit-driven ventures left the landscape that we see today, and a few families during this period were critical participants in the development of the VCNP environment. The earliest of these families was the Oteros who used land in the VCNP primarily for grazing horses, cattle, and sheep. As part of this land use, the Oteros built cabins to serve as housing for family and workers, corrals, and other outbuildings. One such structure, the Otero Cabin, is said to have been constructed in 1908, and based on historical records, is one of the oldest Euroamerican structures in the VCNP. Dendroarchaeological samples from the Otero Cabin were collected during our 2014 field season and the results are presented here. These data and resulting interpretations will provide the VCNP staff with the most recent and accurate data to be presented through interpretative tours while also informing the public about dendroarchaeological methods.