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Decadal fine root decomposition and its responses to a long-term litter and nitrogen additions in northern Michigan

Terrestrial
Vegetation
Project Abstract: 
Fine roots (< 2-mm diameter) are major suppliers of carbon (C) and nitrogen (N) to forest soils, yet there is little understanding of how long-term plant and N inputs affect fine root decomposition rates and the amount of root derived organic matter (OM) stabilized in forest soils. However, most decomposition studies are short-term, limiting our understanding of the biotic and abiotic mechanisms driving long-term root stabilization in soil. To address this limitation in research, we propose to quantify the amount of fine root C and N stabilized in soil after 12 years of decomposition in the DIRT plots at the University of Michigan Biological Station (UMBS) and examine whether long-term plant and N inputs influenced affected this stabilization. This work will build upon a study established in 2010 by Fernanda Santos in the DIRT plots, where, in collaboration with Knute Nadelhoffer and Jeffrey Bird, examined the first two years of root decomposition and found that roots decomposed rapidly (Santos et al. 2016). The major goal of this proposed research project is to collect the remaining 12 mesocosms (PVC, 0-20 cm tall) and 12 soil samples in the UMBS DIRT plots. To accomplish this goal, this proposal seeks funds to cover travel, research, housing, and dinning fees for F. Santos at the UMBS during July 31 and August 5, 2022. The findings of this 12-year study will provide unique, long-term root decomposition data needed to improve to our limited understanding of the role of fine roots in belowground C and N storage in coarse-textured temperate forests soils that lack effective OM stabilization mechanisms.
Investigators: 
aclassen
knute
jdenuyl
Status of Research Project: 
Active
Related publications: 
Rapid fine root C and N mineralization in a northern temperate forest soil
Years Active: 
2022 to 2024
Research sites: 
UMBS DIRT Plots
Methods: 
1.2. Methods 1.2.1. DIRT plots To test the effects of N addition and litter inputs on Acer fine root degradation, a field experiment was initiated in Fall 2010 within an existing and well-monitored northern temperate forest ecosystem experiment called Detritus Input and Removal Treatments (DIRT). 1.2.2. Root decomposition study To examine the influence of long-term aboveground and/or belowground litter and inorganic N additions on mineralization of fine root-derived C and N, in late summer 2010, 13C and 15N-enriched (4.5 atom% 13C, 11.5 atom% 15N) red maple (Acer rubrum) fine root litter was added at a rate of 147 g m-2 to the top 2-5 cm of soils within mesocosms (10-cm diameter PVC core) installed in the top 20 cm of soil in DIRT experimental treatments that: (1) received high levels of N as fertilizer; (2) have no belowground litter inputs, (3) no aboveground and belowground litter inputs, and (4) control – no removal of litter or additional N added. Each DIRT treatment had 3 replicates. 1.2.3. Planned activities at the UMBS (from July 31 to August 5, 2022) Activities will involve (1) collecting the last replicates of intact soil mesocosms (PVC, 0-20 cm tall) containing dual-labeled (13C and 15N) roots that have been decomposing in the DIRT plots for the past 12 years (n = 12) and (2) sampling unlabeled soils (0-20cm, n =12) next to each mesocosm using an auger, totaling 24 samples. Each individual mesocosm will be wrapped in aluminum foil and stored inside a Ziploc bag. Each soil sample collected with an auger will be stored inside a Ziploc bag. All samples will be stored at 4oC before leaving the UMBS. Due to time constraints, sample processing and analyses will take place in TN.