https://doi.org/10.5061/dryad.jh9w0vtj1

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 < 3);
  • soil, bulk soil;
  • SOM, soil organic matter;
  • POM, POM, particulate organic matter (particle size > 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 < 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 > 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.