uid=HFR,o=lter,dc=ecoinformatics,dc=org all public read doi:10.6073/pasta/85dfebad7fa2ec496e81aed3f453bc7d Rose Abramoff https://orcid.org/0000-0002-3393-3064 Adrien Finzi https://orcid.org/0000-0003-2220-4533 2023 English

The objective of this study is to estimate the phenology and partitioning of C allocated belowground across the growing season at Harvard Forest in two hardwood stands dominated by Quercus rubra and Fraxinus americana, respectively, and one conifer stand dominated by Tsuga canadensis. The phenology of fine root production was characterized by multiple flushes of growth and mortality, especially in the red oak (Q. rubra) stand. Root exudation rate did not have a clear seasonal signal. The deciduous hardwood stands allocated C belowground earlier in the season compared to the conifer-dominated stand. Deciduous stands also allocated a greater proportion of total belowground C flux (TBCF) to root growth compared to the conifer-dominated hemlock (T. canadensis) stand. Of the three stands, red oak partitioned the greatest proportion of TBCF (~50%) to root growth, while hemlock partitioned the least.

biomass carbohydrates carbon hemlock nitrogen oak phenology respiration roots LTER controlled vocabulary primary production organic matter LTER core area Harvard Forest HFR LTER USA HFR default

This dataset is released to the public under Creative Commons CC0 1.0 (No Rights Reserved). Please keep the dataset creators informed of any plans to use the dataset. Consultation with the original investigators is strongly encouraged. Publications and data products that make use of the dataset should include proper acknowledgement.

Creative Commons Zero v1.0 Universal https://spdx.org/licenses/CC0-1.0.html CC0-1.0 https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf278 Prospect Hill Tract (Harvard Forest). Coordinates based on WGS84 datum. -72.199898 -72.17676733 +42.54379083 +42.504361 2011 2013 genus Fraxinus species americana white ash genus Quercus species rubra red oak genus Tsuga species canadensis eastern hemlock complete Information Manager Harvard Forest

324 North Main Street Petersham MA 01366 USA

(978) 724-3302 hf-im@lists.fas.harvard.edu Harvard Forest

324 North Main Street Petersham MA 01366 USA

(978) 724-3302 (978) 724-3595 https://harvardforest.fas.harvard.edu

Plots were established in three mono-dominant stands: white ash, red oak, and eastern hemlock. We established 6 biometry plots per stand (N = 18) and 10 minirhizotron tube plots per stand (N = 30). The basal area in each 8-m-radius biometry plot is composed of 80% dominant tree species, with the inner 5-m area containing only the dominant species.

Root production and turnover were measured using a BTC-100x high magnification minirhizotron camera system (Bartz Technology Company, Carpenteria, CA). The camera system was inserted into cellulose acetate butyrate tubes installed at a 45° angle to a vertical soil depth of 40 cm. Thirteen tubes were installed in the center of each minirhizotron tube plot at Harvard Forest 10+ years ago (n = 4 in red oak, n = 9 in eastern hemlock). Seventeen tubes were installed in November 2012 (n = 6 in red oak, n = 1 in eastern hemlock, and n = 10 in white ash) for a sample size of n = 10 for each stand in 2013 and 2014. Minirhizotron tubes installed in November 2012 likely severed existing roots during placement and may have increased root growth rates in the following seasons. We detected a measurable but transient effect of tube installation on root production in red oak. There was no detectable installation effect on red oak root mortality or on the single hemlock tube installed. All white ash tubes were newly installed in November 2012 so it was not possible to establish an effect of installation on white ash root production. The minirhizotron camera captures thirty-nine sequential images that are 13.5 x 17 mm in size along the upper axis of each tube at each sampling interval. The resulting images were processed using the open source imaging software Rootfly (Rootfly Development Team, Version 2.0.2, GNU General Public License). Root length and diameter were scaled to mass using a site-specific relationship based on n = 20 fine root (diameter less than 2 mm) segments per species. Root biomass was estimated from the images using the method of Taylor et al. (2014).

Each month, we collected three 10 x 10 cm samples of the organic horizon and three 4.7 cm diameter mineral soil samples to a depth of 15 cm in each plot. Roots were removed and sorted into fine (less than 2 mm), coarse (greater than 2 mm), live and dead pools. Sorted roots were dried and weighed to obtain standing biomass. Subsamples of roots from monthly soil coring were assayed for carbon and nitrogen content using an elemental analyzer (model NC2500; CE Instruments, Milan, Italy). Fine root standing biomass for the organic horizon down to a depth of 15 cm in the mineral soil was scaled up to g C m-2 by adjusting for the horizontal area of the soil core, the carbon content of roots in each stand, and rock content.

We collected three ~1–2 g fine root samples from each biometry plot. Roots were excavated, washed, and frozen in liquid nitrogen until analysis. Sugars were extracted from dried and finely ground root tissue using a 12:5:3 methanol:chloroform:water solution before being developed with 2% phenol and concentrated sulfuric acid. Absorbance was measured at 490 nm using a digital spectrophotometer (Spectronic 20D+, Thermo Scientific). Starch was extracted using a 0.005 N sulfuric acid solution at 95ºC and developed as described above.

Root exudates were collected from six fine root systems per stand in June and August 2012, and April, May, July and October 2013 following the method of Phillips et al. (2008, 2011). In brief, roots were excavated 48 hours prior to collection, washed, and incubated in a moist soil-sand mixture. Roots were placed into cuvettes with glass beads and a C-free nutrient solution 24 hours prior to collection. At the time of collection, exudate-containing nutrient solution was extracted with two additional flushes of C-free nutrient solution to ensure that exudates adhering to glass beads were flushed into solution. Samples were transported back to the lab on ice and analyzed for non-purgeable organic carbon content using an elemental analyzer (Shimadzu TOC-VCSH analyzer, New Haven, CT).

CO2 efflux was measured directly on recently severed fine roots, in the field at ambient temperature, using an infrared gas analyzer (LI6400; LiCor Biosciences). We compared respiration measurements of an attached and severed root system for each stand on three separate days and confirmed that respiration rates were similar between the two types of roots (correlation coefficient = 0.78) and stable up to approximately 7 hours.

Phillips, R. P., Y. Erlitz, R. Bier, and E. S. Bernhardt. 2008. New approach for capturing soluble root exudates in forest soils. Functional Ecology 22:990–999. Phillips, R. P., A. C. Finzi, and E. S. Bernhardt. 2011. Enhanced root exudation induces microbial feedbacks to N cycling in a pine forest under long-term CO2 fumigation. Ecology letters 14:187–94. Taylor, B. N., K. V. Beidler, A. E. Strand, and S. G. Pritchard. 2014. Improved scaling of minirhizotron data using an empirically-derived depth of field and correcting for the underestimation of root diameters. Plant and Soil 374:941–948.

Harvard Forest

324 North Main Street Petersham MA 01366 USA

(978) 724-3302 (978) 724-3595 https://harvardforest.fas.harvard.edu https://ror.org/059cpzx98 pointOfContact The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts. National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210. hf278-01-root-biomass-cores.csv root biomass - soil cores hf278-01-root-biomass-cores.csv 48789 2bcdb4b9fbef8cb2bd06e27766b2589a 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p27/hf278/hf278-01-root-biomass-cores.csv date sampling date YYYY-MM-DD 1 day NA missing value species dominant tree species where the sample was collected FRAM Fraxinus americana QURU Quercus rubra TSCA Tsuga canadensis NA missing value plot plot number plot number NA missing value ld whether roots were live or dead live live dead dead NA missing value fc whether roots were fine or coarse fine diameter < 2mm coarse diameter > 2mm NA missing value om whether organic horizon or mineral soil organic organic horizon mineral mineral soil NA missing value biomass dry mass of roots, total mass of 3 combined cores gram 0.01 real NA missing value biomass.g.m2 mass of roots per surface area, down to 15 cm depth gramsPerSquareMeter 0.000000001 real NA missing value 952 hf278-02-root-biomass-minirhiz.csv root biomass - minirhizotrons hf278-02-root-biomass-minirhiz.csv 22119 dbc0837f13541af7fe63524fb0900c15 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p27/hf278/hf278-02-root-biomass-minirhiz.csv date date of image collection YYYY-MM-DD 1 day NA missing value species dominant tree species where the minirizhotron tube is located FRAM Fraxinus americana QURU Quercus rubra TSCA Tsuga canadensis NA missing value tube minirizhotron tube number minirizhotron tube number NA missing value biomass mass of roots visible per tube, down to 15 cm depth gram 0.000000001 real NA missing value biomass.g.m2 mass of roots per surface area, down to 15 cm depth gramsPerSquareMeter 0.000000001 real NA missing value 510 hf278-03-root-exudates.csv root exudation hf278-03-root-exudates.csv 6581 ce661a61acb97df74722f6529dccf5ee 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p27/hf278/hf278-03-root-exudates.csv species dominant tree species where the sample was collected FRAM Fraxinus americana QURU Quercus rubra TSCA Tsuga canadensis NA missing value plot plot number plot number NA missing value date sampling date YYYY-MM-DD 1 day NA missing value mean.conc.mg.l mean DOC concentration milligramsPerLiter 0.001 real NA missing value cv.conc coefficient of variation of the concentration trials (usually 3) dimensionless 0.01 real NA missing value vol.ml volume of exudate sample milliliter 0.1 real NA missing value dw.g dry weight of the root sample gram 0.01 real NA missing value adj.conc.mg.l adjusted DOC concentration (control DOC concentration substracted) milligramsPerLiter 0.0001 real NA missing value gcgr mass of carbon exuded by root mass gram 0.000000000000001 real NA missing value 112 hf278-04-root-carbon-nitrogen.csv root carbon and nitrogen content hf278-04-root-carbon-nitrogen.csv 13126 06e3fbecc920c3db5c4a90643947a72a 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p27/hf278/hf278-04-root-carbon-nitrogen.csv species dominant tree species where the sample was collected FRAM Fraxinus americana QURU Quercus rubra TSCA Tsuga canadensis NA missing value plot plot number plot number NA missing value month month of sample collection month NA missing value ld whether roots were live or dead L live D dead NA missing value fc whether roots were fine or coarse F diameter < 2mm C diameter > 2mm NA missing value n.per root nitrogen content (%N) dimensionless 0.000000001 real NA missing value c.per root carbon content (%C) dimensionless 0.000000001 real NA missing value c.n carbon to nitrogen ratio dimensionless 0.000000001 real NA missing value 261 hf278-05-root-nonstruct-carbs.csv nonstructural carbohydrates hf278-05-root-nonstruct-carbs.csv 3074 ba96e88ae06500f27a3aba7eb43f54df 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p27/hf278/hf278-05-root-nonstruct-carbs.csv date sampling date YYYY-MM-DD 1 day NA missing value species dominant tree species where the sample was collected FRAM Fraxinus americana QURU Quercus rubra TSCA Tsuga canadensis NA missing value su.st whether sugars or starch sample starch starch sugar sugar NA missing value n number of plots measured number 1 natural NA missing value mean fraction of root dry weight, averaged per species and sampling date (g nonstructural carbohydrates/g dry roots) gramsPerGram 0.000000001 real NA missing value se standard error dimensionless 0.000000001 real NA missing value 62 hf278-06-root-resp.csv root respiration hf278-06-root-resp.csv 1916 9df5fd5c826ca441f34ee4784875caf1 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p27/hf278/hf278-06-root-resp.csv date sampling date YYYY-MM-DD 1 day NA missing value species dominant tree species where the sample was collected FRAM Fraxinus americana QURU Quercus rubra TSCA Tsuga canadensis NA missing value efflux.umol.co2.g.s mass-specific root respiration (μmol CO2 g-1 s-1) micromolePerGramPerSecond 0.000000000000000001 real NA missing value 67 soil short-term measurement