uid=HFR,o=lter,dc=ecoinformatics,dc=org all public read doi:10.6073/pasta/e5467ed3c413cadea98b24e9120a038f Richard Bowden Serita Frey https://orcid.org/0000-0002-9221-5919 Knute Nadelhoffer https://orcid.org/0000-0001-9775-894X Researcher 2023 English

Forests typically respond to nitrogen additions with increased productivity, hence a long-held paradigm was that chronic additions of anthropogenically-derived atmospheric deposition would have positive ecosystem effects. However, twenty years of work at the Harvard Forest Chronic N Deposition plots, and in other forest ecosystems as well, has shown that that this simplistic view is incomplete. For example, enhanced ammonium uptake increases soil acidity, leading to mobilization of aluminum, and loss of nutrient cations (e.g. Mg2+, Ca2+, and K+ ) all of which influence root mass, turnover, and activity. To address long-term impacts of N additions on forest root mass, we removed O-horizon (forest floor) samples from the Chronic N hardwood and red pine stands to quantify the total mass of roots. We found that long term N additions had contrasting results in the two forests. In the hardwood plots, total root mass (less than 2mm) increased from 0.167 + 0.026 (S.E.) kg m-2 in the control plot to 0.434 + 0.170 kg m-2 in the high N plots. In contrast, in the red pine stand, roots declined from 0.074 + 0.011 (S.E.) kg m-2 in the control plot to 0.031 + 0.016 kg m-2 in the high N plots. These data are in agreement with data for aboveground productivity at the Chronic N plots, which show stimulated growth in the hardwoods and severe growth declines and enhanced mortality in the pine stand.

biomass nitrogen roots LTER controlled vocabulary organic matter disturbance 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=hf166 Prospect Hill Tract (Harvard Forest). Coordinates based on WGS84 datum. -72.1813 -72.1813 +42.5425 +42.5425 406 406 meter 2008 2008 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

In 2008, we collected three to six 20x20cm O horizon samples each of each of the Control, Low N, and High N plots, in both the hardwood and red pine stands. Samples were frozen immediately after collection, and returned to Allegheny College for analysis. Samples were thawed just prior to collection, and those roots systems that were most intact were removed initially to maintain as complete a root system as the sample size would allow. These roots were kept for a related study on root order and C and N uptake activity and refrozen; these roots were later surface dried briefly to remove surface water, and weighed so that, after obtaining air-dry:oven-dry conversions, the mass of this root material could be added into the total mass for each sample. All remaining roots were extracted manually from each sample, washed, and divided into the following diameter classes: greater than 2 mm, between 1 and 2 mm, and less than 1mm. Roots were kept moist during the sorting process, and then refrozen when sorting was complete. Roots later were subsequently dried at 105C for 48 hours, mass was determined, and samples were ground in a Wiley Mill to pass through a no. 20 mesh sieve for later C and N analysis.

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. hf166-01-root-mass.csv root mass hf166-01-root-mass.csv 1719 e79d06795b9c37eb2149ca75f8caacee 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p16/hf166/hf166-01-root-mass.csv stand stand Hardwood Chronic N Hardwood stand Pine Chronic N Red Pine stand treatment annual N addition Control 0 kg N/ha/y 50 50 kg N/ha/y 150 150 kg N/ha/y replicate forest floor sample in each stand & treatment (1-6) replicate (1-6) sample.id unique name of subplot from which each forest floor sample was obtained unique name of subplot from which each forest floor sample was obtained percent.0 percentage of total roots less than or equal to 1mm diameter dimensionless 0.01 real NA missing value percent.1 percentage of total roots greater than 1 mm and less than 2mm diameter dimensionless 0.01 real NA missing value percent.2 percentage of total roots greater than 2mm diameter dimensionless 0.01 real NA missing value mass.0 oven dry biomass of roots less than or equal to 1mm diameter gram 0.001 real NA missing value mass.1 oven dry biomass of roots greater than 1 mm and less than 2mm diameter gram 0.001 real NA missing value mass.2 oven dry biomass of roots greater than 2mm diameter gram 0.001 real NA missing value 30 plot soil short-term measurement https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf008