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Monson, Russell K.

Publications and source records attributed to Monson, Russell K..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Heterogeneous isotope effects decouple conifer leaf and branch sugar δ 18 O and δ 13 C

Isotope ratios of tree-ring cellulose are a prominent tool to reconstruct paleoclimate and plant responses to environmental variation. Current models for cellulose isotope ratios assume a transfer of the environmental signals recorded in bulk leaf water to carbohydrates and ultimately into stem cellulose. However, the isotopic signal of carbohydrates exported from leaf to branch may deviate from mean leaf values if spatial heterogeneity in isotope ratios exists in the leaf. We tested whether the isotopic heterogeneity previously observed along the length of a ponderosa pine (Pinus ponderosa) leaf water was preserved in photosynthetic products. We observed an increase in both sugar and bulk tissue δ 18 O values along the needle, but the increase in carbohydrate δ 18 O values was dampened relative to the trend observed in leaf water. In contrast, δ 13 C values of both sugar and bulk organic matter were invariant along the needle. Additionally, phloem-exported sugar measured in the branch below the needles did not match whole-needle values of δ 18 O or δ 13 C. Instead, there was a near-constant offset observed between the branch and needle sugar δ 13 C values, while branch δ 18 O values were most similar to δ 18 O values observed for sugar at the base of the needle. The observed offset between the branch and needle sugar δ 18 O values likely arises from partial isotope oxygen exchange between sugars and water during phloem loading and transport. An improved understanding of the conditions producing differential δ 13 C and δ 18 O isotope effects between branch phloem and needle sugars could improve tree-ring-based climate reconstructions.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Coordinated resource allocation to plant growth–defense tradeoffs

Summary Plant resource allocation patterns often reveal tradeoffs that favor growth (G) over defense (D), or vice versa. Ecologists most often explain G–D tradeoffs through principles of economic optimality, in which negative trait correlations are attributed to the reconciliation of fitness costs. Recently, researchers in molecular biology have developed ‘big data’ resources including multi‐omic (e.g. transcriptomic, proteomic and metabolomic) studies that describe the cellular processes controlling gene expression in model species. In this synthesis, we bridge ecological theory with discoveries in multi‐omics biology to better understand how selection has shaped the mechanisms of G–D tradeoffs. Multi‐omic studies reveal strategically coordinated patterns in resource allocation that are enabled by phytohormone crosstalk and transcriptional signal cascades. Coordinated resource allocation justifies the framework of optimality theory, while providing mechanistic insight into the feedbacks and control hubs that calibrate G–D tradeoff commitments. We use the existing literature to describe the coordinated resource allocation hypothesis (CoRAH) that accounts for balanced cellular controls during the expression of G–D tradeoffs, while sustaining stored resource pools to buffer the impacts of future stresses. The integrative mechanisms of the CoRAH unify the supply‐ and demand‐side perspectives of previous G–D tradeoff theories.

Monson, Russell K.↗
DOE OSTI2020

Data, Photographs, Videos, and Information for the Niwot Ridge Subalpine Forest (US-NR1) AmeriFlux site

This data package contains data and information about the operation of the Niwot Ridge Subalpine Forest AmeriFlux site (US-NR1) between Nov 1998 to the present (2020). This data archive supplements the primary 30-min data storage for the US-NR1 data (i.e., https://doi.org/10.17190/AMF/1246088) by providing the following: (i) five-minute statistics (means, variances, covariances) of all data measured by the data system between Nov 1998 and September 2020 in netCDF format, (ii) CSV data files saved within the memory of the CR23X data loggers (as well as an archive of the data logger programs), (iii) an archive of previous 30-min ASCII data versions of the US-NR1 AmeriFlux data and information related to each data release (a replica of what can be found at http://urquell.colorado.edu/data_ameriflux/), (iv) a web calendar (in HTML format) documenting activity at the site (a replica of http://urquell.colorado.edu/calendar/), (v) photos (over 15,000) and video taken at the site between years 2001 and present day (2020), and (vi) several auxiliary datasets, primary related to trees near the site, soil moisture and soil temperature, and subcanopy radiation data. The data package is setup so that the web calendar, photos, and electronic logbook can be easily accessed on a local computer using a web browser. The provided data files are in either netCDF, CSV, ASCII, or MATLAB format. To obtain a better understanding about the archive, please start by reading the PDF: README_ESS_DIVE_USNR1_readme_first.pdf.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2016

Interactions Between Temperature and Intercellular CO2 Concentration in Controlling Leaf Isoprene Emission Rates

Plant isoprene emissions have been linked to several reaction pathways involved in atmospheric photochemistry. Evidence exists from a limited set of past observations that isoprene emission rate (I(sub s)) decreases as a function of increasing atmospheric CO2 concentration, and that increased temperature suppresses the CO2 effect. We studied interactions between intercellular CO2 concentration (C(sub I)) and temperature as they affect I(sub s) in field-grown hybrid poplar trees in one of the warmest climates on earth - the Sonoran Desert of the southwestern United States. We observed an unexpected midsummer down regulation of I(sub s) despite the persistence of relatively high temperatures. High temperature suppression of the I(sub s):C(sub I) relation occurred at all times during the growing season, but sensitivity of I(sub s) to increased C(sub I) was greatest during the midsummer period when I(subs) was lowest. We interpret the seasonal down regulation of I(sub s) and increased sensitivity of I(sub s) to C(sub I) as being caused by weather changes associated with the onset of a regional monsoon system. Our observations on the temperature suppression of the I(sub s):C(sub I) relation are best explained by the existence of a small pool of chloroplastic inorganic phosphate, balanced by several large, connected metabolic fluxes, which together, determine the C(sub I) and temperature dependencies of phosphoenolpyruvate import into the chloroplast.

Monson, Russell K.↗