DOI: 10.5061/dryad.sj3tx96b8
title: Decoupling of nitrogen, phosphorus, and carbon release from fine and coarse roots during 7 years of decomposition

description: Belowground litter decomposition represents an important source of the
 limiting nutrients nitrogen (N) and phosphorus (P) to forest soils, but
 roots also immobilize these nutrients during the decomposition process.
 Despite clear implications for soil fertility, the rates and drivers of
 nutrient immobilization and release (as the percent of increase
 and decrease of the initial pool) from root litter remain poorly
 understood, especially in coarse roots (&gt; 2 mm diameter). To
 address this gap, we conducted a seven-year field decomposition experiment
 using roots from three species, across five diameter classes (&lt; 1
 mm, 1–2 mm, 2–5 mm, 5–10 mm, and 10–20 mm) in a temperate forest. Nitrogen
 dynamics were largely decoupled with P and carbon (C) over the course of
 the experiment, and both varied by species and root diameter.
 Roots released P to the surrounding soil within the first year of
 decomposition. In contrast, roots immobilized N for much longer, with the
 coarsest roots remaining a net N sink after 7 years. Long-term N release
 was jointly controlled by initial nutrient and C quality, whereas P
 release and decomposition rate were better predicted by initial C quality.
 Initial root nutrients well predicted the difference between long-term N
 versus P release. Synthesis. Our results highlight the fact that N and P
 dynamics should be considered separately when modelling nutrient release
 during root decomposition and suggest that the functional diversity of
 belowground biomass may have considerable afterlife effects on the
 relative availability of N and P in soil. We conclude that root litter,
 especially coarse root litter, represents an underappreciated N sink in
 forest soils.
description: Root material for incubation from three to five
 mature individuals of each species was excavated in late May 2012 from the
 0–20 cm soil layer, and immediately taken back to the lab for processing.
 The roots were cleaned with tap water, and dead roots were removed and
 then divided into five diameter classes: &lt; 1 mm, 1–2 mm, 2–5 mm,
 5–10 mm, 10–20 mm, and then mixed for each diameter class and each species
 to reduce the influence of intra-species variability of roots traits on
 decomposition. A sample of 2–5 g air-dried roots was placed into each 0.1
 mm mesh litter-bag, and the masses were later corrected to oven-dried
 (65°C) mass using species- and diameter-specific correction factors.
 The correction factor,
 i.e., the ratio of the oven-dried (65 °C) mass to the air-dried mass, was determined with
 another root sample of 5 g
 for each of the five diameters for the three species. Although the litter-bag method may not
 accurately estimate root decomposition rate by changing the relationships
 among root, soil and rhizosphere decomposer community as well as
 environmental aspects in the short-term, this method is helpful to study
 the decomposition rate and its relationship to traits by tree species or
 diameter, especially in natural forests. There were 720 bags in total: 60
 bags for each of the &lt; 1 mm, 1–2 mm, and 2–5 mm diameter classes,
 and 30 bags each of the 5–10 mm and 10–20 mm diameter classes in a
 species. Litter-bags by species and root diameters were buried on June
 3rd, 2012 to 10 cm depth underneath five replicate trees of each species,
 with species corresponding to the species of root contained in the
 litterbag. We did not incubate the
 roots underneath the same
 individual tree because that digging root introduced a large disturbance
 to the tree and the soil around the tree. After burying the
 bags, the litter layer was restored as much as possible to minimize
 disturbance. Litterbags were retrieved on eight occasions
 during the first two years of incubation to effectively capture dynamics
 during the early stages of decomposition. To characterize later stage
 dynamics, we retrieved one set of litterbags each in the 3rd, 5th and 7th
 years of incubation. This resulted in a total of 11 litterbag collections,
 representing incubation times of 1, 2, 3, 4, 5, 11, 13, 15, 27, 49, and 87
 months. In total, 666 of 720 litter bags were retrieved, and the rest were
 lost or destroyed by wild boar (Sus scrofa L.). Upon removal from the
 field, all roots were cleaned, oven-dried it at 65 °C, weighed, and
 analysed for C, N and P
 concentrations. Additional root samples of each species and
 diameter class were collected on May 29th, 2021 to measure the initial
 root quality (the same as the tree individuals for root material
 incubation). We characterized each sample for concentrations of C, N, P,
 Ca, Mg, Si, soluble sugars, starch, hemicellulose, cellulose, lignin, and
 total phenolics. Additional root samples of each species and diameter
 class were collected on May 29th, 2021 to measure the initial root quality
 (the same as the tree individuals for root material incubation). We
 characterized each sample for concentrations of C, N, P, Ca, Mg, Si,
 soluble sugars, starch, hemicellulose, cellulose, lignin, and total
 phenolics. 
description: # Decoupling of nitrogen, phosphorus, and carbon release from fine and
 coarse roots during 7 years of decomposition
 ## Description of the data
 and file structure 1. Root decomposition parameter and initial root
 quality These datasets contain root decomposition parameter and initial
 root quality from five root diameter classes of the three tree species *
 species, the tree species used in the study; * diameter, the root diameter
 used in the study (mm); * *k*<sub>LT</sub>, double exponential
 model long-term average decomposition rate; * *k*<sub>2</sub>,
 double exponential model decomposition rate for the slow pool; *
 *k*<sub>2</sub>s, single exponential model decomposition rate
 for the slow pool * *k*<sub>a</sub>, asymptotic model
 decomposition rate * LCR, long-term C release; * LNR, long-term N release;
 * LPR, long-term P release; * *k*<sub>1</sub>, double
 exponential model decomposition rate for the fast pool; *
 *k*<sub>1</sub>s, single exponential model decomposition rate
 for the fast pool; * SCR, short-term C release; * SNR, short-term N
 release; * SPR, short-term P release; * LNR-LPR, the difference from
 long-term N release and P release * SNR-SPR, the difference from
 short-term N release and P release * SS, soluble sugars; * Sta, starch; *
 NSC, non-structural carbohydrates (the total of soluble sugars and
 starch); * Hemi, hemicellulose; * DC, decomposable carbohydrates (the
 total of NSC and Hemi); * Cell, cellulose; * Lign, lignin; * SC,
 structural carbohydrates (the total of Cell and Lign); * Phe, phenolics; *
 RC, resistant carbohydrates (the total of Cell, Lign and Phe); * C,
 carbon; * N, nitrogen; * P, phosphorus; * Ca, calcium; * Mg, magnesium; *
 Si, silicon. * SC_NSC, the ratios of structural carbohydrates to
 non-structural carbohydrates; * C_N, the ratios of carbon to nitrogen; *
 N_P, the ratios of nitrogen to phosphorus; * C_P, the ratios of carbon to
 phosphorus; * NSC_N, the ratios of non-structural carbohydrates to
 nitrogen; * NSC_P, the ratios of non-structural carbohydrates to
 phosphorus; * C_NSC, the ratios of carbon to non-structural carbohydrates;
 * NSC_Phe, the ratios of non-structural carbohydrates to phenolics; *
 N_Phe, the ratios of nitrogen to phenolics; * C_Phe, the ratios of carbon
 to phenolics; * Cell_N, the ratios of cellulose to nitrogen; * Cell_Phe,
 the ratios of cellulose to phenolics; * Lign_N, the ratios of lignin to
 nitrogen; * Lign_P, the ratios of lignin to phosphorus; * RC_DC, the
 ratios of resistant carbohydrates to decomposable carbohydrates; * SS_Phe,
 the ratios of soluble sugars to phenolics; * SS_Lign, the ratios of
 soluble sugars to lignin; 2. Carbon, nitrogen, phosphorous concentrations
 and carbon, nitrogen, phosphorous remaining These datasets contain
 decomposition process data on carbon, nitrogen, phosphorous concentrations
 and carbon, nitrogen, phosphorous remaining from five root diameter
 classes of the three tree species. * species, the tree species used in the
 study; * decomposition time (year), The time of root decomposition; *
 &lt;1mm N concentration (mg/g), nitrogen concentration of root diameter
 &lt;1mm; * 1-2mm N concentration (mg/g), nitrogen concentration of root
 diameter 1-2mm; * 2-5mm N concentration (mg/g), nitrogen concentration of
 root diameter 2-5mm; * 5-10mm N concentration (mg/g), nitrogen
 concentration of root diameter 5-10mm; * 10-20mm N concentration (mg/g),
 nitrogen concentration of root diameter 10-20mm; * &lt;1mm P concentration
 (mg/g), phosphorus concentration of root diameter &lt;1mm; * 1-2mm P
 concentration (mg/g), phosphorus concentration of root diameter 1-2mm; *
 2-5mm P concentration (mg/g), phosphorus concentration of root diameter
 2-5mm; * 5-10mm P concentration (mg/g), phosphorus concentration of root
 diameter 5-10mm; * 10-20mm P concentration (mg/g), phosphorus
 concentration of root diameter 10-20mm; * &lt;1mm C concentration (mg/g),
 carbon concentration of root diameter &lt;1mm; * 1-2mm C concentration
 (mg/g), carbon concentration of root diameter 1-2mm; * 2-5mm C
 concentration (mg/g), carbon concentration of root diameter 2-5mm; *
 5-10mm C concentration (mg/g), carbon concentration of root diameter
 5-10mm; * 10-20mm C concentration (mg/g), carbon concentration of root
 diameter 10-20mm; * &lt;1mm N remaining, nitrogen remaining of root
 diameter &lt;1mm; * 1-2mm N remaining, nitrogen remaining of root diameter
 1-2mm; * 2-5mm N remaining, nitrogen remaining of root diameter 2-5mm; *
 5-10mm N remaining, nitrogen remaining of root diameter 5-10mm; * 10-20mm
 N remaining, nitrogen remaining of root diameter 10-20mm; * &lt;1mm P
 remaining, phosphorus remaining of root diameter &lt;1mm; * 1-2mm P
 remaining, phosphorus remaining of root diameter 1-2mm; * 2-5mm P
 remaining, phosphorus remaining of root diameter 2-5mm; * 5-10mm P
 remaining, phosphorus remaining of root diameter 5-10mm; * 10-20mm P
 remaining, phosphorus remaining of root diameter 10-20mm; * &lt;1mm C
 remaining, carbon remaining of root diameter &lt;1mm; * 1-2mm C remaining,
 carbon remaining of root diameter 1-2mm; * 2-5mm C remaining, carbon
 remaining of root diameter 2-5mm; * 5-10mm C remaining, carbon remaining
 of root diameter 5-10mm; * 10-20mm C remaining, carbon remaining of root
 diameter 10-20mm;   Missing values are denoted by NA.