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Smith Lab News

July 22, 2022: The first in-person LEMONTREE meeting in Reading!

Nick joined others from the LEMONTREE group for their first in-person meeting of the project in Reading, UK. The project meeting brought together individuals from the various groups working on the project. We hashed out ideas and plans for the second year of the 5-year project. Look out for more from us soon!

July 20, 2022: Nick presents at the 2022 MMEE meeting in Reading

Nick presented some of the lab's work on plant-nitrogen interactions at the 2022 Mathematical Models in Ecology and Evolution (MMEE) meeting in Reading, UK. If you are interested in Nick's presentation, you can find it here.

July 15, 2022: RMBL A/Ci curves

Brad, Zinny, and Nick deployed to the Rocky Mountain Biological Lab (RMBL) for 10 days of intense plant physiology sampling. The crew, in conjunction with folks from U. Arizona, Oklahoma U., and U. Michigan recorded CO2 responses curves of photosynthesis at 8 sites along an elevational gradient. Brad will be leading an analysis of the data to examine how plants adjust to the changes along the gradient within and across species.

In addition, we are collaborating with Rose Brinkhoff (postdoc at U. Michigan), who is examining similar responses along the gradient and within open-top warming chambers at high and low elevations.

This work is being done in support of (and with support from) the LEMONTREE project.

June 25, 2022: Trillium Trail greenhouse experiment begins!

We received rhizomes of Arisaema triphyllum (Jack in the pulpit), Maianthemum racemosum (false Salomon's seal), and Trillium erectum (red trillium) from Trillium Trail in Pennsylvannia. We are growing them in the greenhouse here in Texas as part of a new project examining the mutualistic relationship between these species and arbuscular mycorrhizal fungi.

Look out for more on this collaborative project with Susan Kaliz (UTK), Stephanie Kivlin (UTK), and Lalasia Bialic-Murphy (ETH) soon!

June 23, 2022: Evan receives a research award!

Evan won a Botanical Society of America Bill Dahl Graduate Student Research Award (GSRA) to support isotopic analyses on his ongoing growth chamber study. Congrats Evan!

More information on the GSRA can be found here.

June 14, 2022: NutNet physiology add-on kicks off in Temple, TX

Jeff and Nick traveled to Temple, TX to measure photosynthetic processes at the Nutrient Network (nutnet.org) site there. This is part of an add-on project, where we already have contribution commitments from many sites to help us better understand photosynthetic responses to nutrient addition.

One of the best parts of the Temple trip was getting to meet and do field work with Erika Hersch-Green and Hailee Petosky from Michigan Tech, Tilak Chaudhary from Texas State, and Eve Gray and Phil Fay from the USDA ARS in Temple.

May 26, 2022: Nick presents at EGU

Nick presented modeling work examining the impact of CO2 acclimation on modeled future carbon-nitrogen dynamics. The full presentation can be found here.

Exploring Vienna and meeting LEMONTREE collaborators was a ton of fun. Special thanks to companions to tourism companions Jan Lankhorst and Astrid Ode.

May 17, 2022: A field campaign to the Guadalupe Mountains National Park

Nick, Brad, and Christine joined a group of faculty, postdocs, graduate students, and undergraduate students on week-long field campaign to the Guadalupe Mountains National Park (GUMO). The team intensively sampled McKittrick Canyon for plant traits and herbarium specimens. This included some photosynthesis measurements (A/Ci curves)!

The mountains provided a beautiful backdrop for botanizing!

May 13, 2022: New paper on tree growth published in Global Change Biology

In a paper led by Wenjing Tao and Kangshan Mao (Sichuan University) and co-authored by Nick, we used tree ring data to show that daytime warming has resulted in a negative impact on tree growth across the Northern Hemisphere. The results suggest that this was due to a positive relationship between daytime warming and drought stress.

The full paper can be found here in Global Change Biology.

Effects of temperatures, precipitation, and drought on radial growth in warm and cold regions. (a) Mean annual daytime temperature (MADT, °C) and mean annual nighttime temperature (MANT, °C), (b) mean annual precipitation (MAP, mm) and mean annual 12-month standardized precipitation-evapotranspiration index (SPEI), (c) mean daytime temperature of the warmest quarter (DTWQ, °C), and mean nighttime temperature of the warmest quarter (NTWQ, °C), and (d) mean daytime temperature of the coldest quarter (DTCQ, °C) and mean nighttime temperature of the coldest quarter (NTCQ, °C).

April 13, 2022: Ricky's paper on low temperature acclimation is published in Plant Biology!

Ricky Kong, a former research exchange student in the lab from the University of Western Ontario published his findings on low temperature acclimation in Plant Biology. Using growth chambers, we acclimated Populus balsamifera seedlings to 6 °C and 10 °C. The temperature treatments were crossed with two levels of nitrogen fertilization.

Interestingly, the instantaneous temperature responses of photosynthetic and respiratory biochemistry were similar for all treatments, suggesting little acclimation of biochemical properties. However, stomatal conductance rates led to increases in photosynthesis at high temperature in the 10 °C grown regardless of nitrogen fertilization level.

The full paper can be found at the journal's website.

Instantaneous biochemical temperature responses of seedlings grown under different temperature and nitrogen conditions.

April 12, 2022: The lab gets an award!

Following a nomination by Lizz and Evan, Nick was named as an ESA Early Career Fellow.

From ESA: "Early Career Fellows are members within eight years of completing their doctoral training (or other terminal degree) who have advanced ecological knowledge and applications and show promise of continuing to make outstanding contributions to a wide range of fields served by ESA. They are elected for five years."

Although Nick's name is on the award, this is really a testament to all the awesome students, postdocs, and collaborators the lab has had throughout the years. The network of colleagues we have built are strong, supportive, and inclusive and we plan to keep it that way for years to come.

April 4, 2022: Morgan and Joseph present their research at the 2022 TTU Undergraduate Research Conference

Morgan and Joseph each presented their undergradaute research projects that they started in Fall 2021 at the 2022 TTU Undergraduate Research Conference (URC).

Morgan spent the Fall measuring litter decomposition and soil respiration at the Lubbock Nutrient Network site. She found that litter decomposed faster in their home plots than it did in different treatment plots, regardless of whether litter was moved from fertilized to control plots or from control to fertilized plots. Interestingly, however, the treatments did not impact decomposition or soil respiration rates. These are cool findings that deserve further investigation!

Joseph examined carbon costs of nitrogen acquisition in soybean using a factorial soil nitrogen by nitrogen fixing bacteria inoculation experiment. He found that inoculation reduced carbon costs of nitrogen acquisition in the low soil nitrogen treatments, but not in the high soil nitrogen treatments. This work furthers our understanding of how symbioses with nitrogen fixing bacteria influences plant functioning. Joseph won 2nd place in the Agriculture and Environment category for his poster!

This work was part of a Coure-based Undergraduate Research Experience (CURE), generously funded by an NSF CAREER award, the TTU Center for Transformative Undergraduate Experiences (TrUE), and the TTU Honors College.

Great job Morgan and Joseph!!

February 17, 2022: Helen's model of C4 photosynthetic acclimation published in JAMES!

Former Masters student, Helen Scott, and Nick published a model of C4 photosynthetic acclimation in Journal of Advances in Modeling Earth Systems (JAMES). The paper can be found at this link. The model code can be found at this link. The functions are also incorporated into the model of photosynthetic acclimation that is maintained by the lab and can be called using a C4 option. This model code can be found at this link.

The paper introduces a new model of acclimation of C4 photosynthetic traits based on photosynthetic least cost theory. The model is based on the optimality principle that plants should set up their photosynthetic traits such that carbon assimilation is maximized at the lowest resource use. The model predicts many traits including the ratio of intercellular to atmospheric CO2 (χ), the maximum rate of Rubisco carboxylation (Vcmax), the maximum rate of PEP carboxylation (Vpmax), and the maximum rate of electron transport (Jmax), as well as gross carbon assimilation.

The model corroborates previous studies and shows that C4 photosynthesis is most beneficial under hot, dry, low CO2 conditions. Comparisons to remotely sensed C4 cover showed that C4 presence is predictable from these responses. The model is suitable for incorporation into land surface and Earth system models and folks are encouraged to contact Nick if they would like to discuss this further.

Zinny, Jeff, and others in the lab will be following up on this work using a combination of modeling, field, and controlled environment experiments to better understand photosynthetic acclimation in a changing world.

Figure 1 from the paper ("Pacman figure") showing the cellular arrangement of C4 species and the key equations to simulate acclimation of C4 processes.