DOI: 10.5061/dryad.jh9w0vtj1
title: Nitrogen redistribution and seasonal trait fluctuation facilitate plant N conservation and ecosystem N retention

description: Low available soil nitrogen (N) limits plant productivity in alpine
 regions, and alpine plants thus resorb and reallocate N from senescing
 tissues to conserve this limited N during the nongrowing season. However,
 the destination and extent of N redistribution during plant senescence
 among above- and below-ground organs, let alone other processes of
 translocation outside of plants and into the soil components, remain
 poorly understood. Utilizing the 15N stable isotope as a tracer, we
 quantified N redistribution among above- and below-ground plant organs and
 different soil components during senescence in an alpine meadow ecosystem,
 and explored the relationship between 15N among plant-soil N
 pools with seasonal fluctuations of plant functional traits. We found a
 substantial depletion of 15N in fine roots (-40% ± 2.8%) and aboveground
 tissues (-51% ± 5.1%), and an enhanced 15N storage primarily in coarse
 roots (+79% ± 27%) and soil organic matter (+37% ± 10%) during plant
 senescence. In parallel, we observed a temporal variation in plant
 functional traits, representing a shift from more acquisitive to more
 conservative strategies as the growing season ends, such as higher coarse
 root N and coarse root to fine root ratio. The seasonal trait variations
 were highly correlated with the 15N retention in coarse roots and soil
 organic matter. Particularly, 15N retention in particulate and
 mineral-associated organic matter increased by 30% ± 12% and 24% ± 9%,
 respectively, suggesting a potential pathway through which fine root and
 microbial mortality contribute to 15N redistribution into soil N pools
 during senescence. Synthesis. N redistribution and seasonal plant trait
 fluctuation facilitate plant N conservation and ecosystem N retention in
 the alpine system. This study suggests a coupled aboveground-belowground N
 conserving strategy that may optimize the temporal coupling between plant
 N demand and ecosystem N supply in N-limited alpine ecosystems.
description: # Nitrogen redistribution and seasonal trait fluctuation facilitate plant
 N conservation and ecosystem N retention
 **Abstract** 1.  Low
 available soil nitrogen (N) limits plant productivity in alpine regions,
 and alpine plants thus resorb and reallocate N from senescing tissues to
 conserve this limited N during the nongrowing season. However, the
 destination and extent of N redistribution during plant senescence among
 above- and below-ground organs, let alone other processes of translocation
 outside of plants and into the soil components, remain poorly understood.
 2.  Utilizing 15N stable isotope as a tracer, we quantified N
 redistribution among above- and below-ground plant organs and different
 soil components during senescence in an alpine meadow ecosystem, and
 explored the relationship between 15N partitioning among plant-soil N
 pools with seasonal fluctuations of plant functional traits. 3.  We found
 a substantial depletion of 15N in fine roots (-40% ± 2.8%) and aboveground
 tissues (-51% ± 5.1%), and an enhanced 15N storage primarily in coarse
 roots (+79% ± 27%) and soil organic matter (+37% ± 10%) during plant
 senescence. In parallel, we observed a temporal variation in plant
 functional traits, representing a shift from more acquisitive to more
 conservative strategies as the growing season ends, such as higher coarse
 root N and coarse root to fine root ratio. The seasonal trait variations
 were highly correlated with the 15N retention in coarse roots and soil
 organic matter. Particularly, 15N retention in particulate and
 mineral-associated organic matter increased by 30% ± 12% and 24% ± 9%,
 respectively, suggesting a potential pathway through which fine root and
 microbial mortality contribute to 15N redistribution into soil N pools
 during senescence. 4.  *Synthesis*. N redistribution and seasonal plant
 trait fluctuation facilitate plant N conservation and ecosystem N
 retention in the alpine system. This study suggests a coupled
 aboveground-belowground N conserving strategy that may optimize the
 temporal coupling between plant N demand and ecosystem N supply in
 N-limited alpine ecosystems. **Description of the data and file
 structure** ***In the "15N recovery" sheet:*** * stage, the
 plant growing stage: M, Mature stage (the peak of plant growing stage) or
 S, Senescent stage (the end of growing season); * plot, Field experimental
 plot ID; * label2, sample ID for each stage; * group, parameter group
 (15N:15N recovery data); * variables, plant and soil N pools and their
 components; * plant, the entire plant including above- and below-ground
 plant tissues; * shoot, above-ground plant tissues; * root, below-ground
 plant tissues; * CR, coarse root (transportive roots and rhizomes, root
 order ≥ 3); * FR, fine roots (absorptive roots, root order &lt; 3); *
 soil, bulk soil; * SOM, soil organic matter; * POM, POM, particulate
 organic matter (particle size &gt; 53 μm); * MAOM, MAOM,
 mineral-associated organic matter (particle size ≤ 53 μm); * Extractable
 N, K2SO4 extractable N; * MBN, microbial biomass N; * NEOM,
 non-extractable soil organic matter; * value, the 15N recovery rate ***In
 the "plant traits" sheet:*** * stage, the plant growing stage:
 M, Mature stage (the peak of plant growing stage) or S, Senescent stage
 (the end of growing season); * plot, Field experimental plot ID; * label2,
 sample ID for each stage; * group, parameter group; * plant: plant
 functional traits; * root scan, root morphological traits; * diversity,
 diversity indices of plant communities; * variables, above- and
 below-ground plant traits and community indices; * CR, coarse root
 (transportive roots and rhizomes, root order ≥ 3); * FR, fine roots
 (absorptive roots, root order &lt; 3);RD, root diameter; * RD, root
 diameter (mm); * SRL, specific root length (m/g); * SRA, specific root
 area(cm2/g); * RTD, root tissue density (g/cm3); * C, carbon concentration
 (mg/g); * N, nitrogen concentration(mg/g); * C:N, the ratio of C to N
 concentrations; * Root mass fraction, the percentage of root biomass to
 entire plant biomass; * FR mass fraction, the percentage of fine root
 biomass to entire plant biomass; * CR mass fraction, the percentage of
 coarse root biomass to entire plant biomass; * Root: Shoot, biomass ratio
 of all below- to above-ground organs; * CR:FR, the ratio of CR to FR
 biomass; * value, the value of above- and below-ground plant traits and
 community indices; ***In the "soil properties" sheet:*** *
 stage, the plant growing stage: M, Mature stage (the peak of plant growing
 stage) or S, Senescent stage (the end of growing season); * plot, Field
 experimental plot ID; * label2, sample ID for each stage; * group,
 parameter group; * variables, soil and microbial properties; * NH4+, soil
 ammonium concentration; * NO3-, soil nitrate concentration, * IN,
 inorganic form of soil N concentration; * AP, available soil phosphorus; *
 DOC, dissolved organic C; * DON, dissolved organic N; * pH: soil pH; *
 MBC, soil microbial biomass C; * MBN, microbial biomass N; * POM,
 particulate organic matter (particle size &gt; 53 μm); * MAOM,
 mineral-associated organic matter (particle size ≤ 53 μm); * TC, total
 soil carbon concentration; * TN, total soil nitrogen concentration; * C:N,
 the ratio of C to N concentrations; * value, the value of soil and
 microbial properties.