Canopy and understory nitrogen additions differently affect soil microbial residual carbon in a temperate forest

Atmospheric nitrogen (N) deposition in forests can affect soil microbial growth and turnover directly through increasing N availability and indirectly through altering plant-derived carbon (C) availability for microbes. This impacts microbial residues (i.e., amino sugars), a major component of soil organic C (SOC). Previous studies in forests have so far focused on the impact of understory N addition on microbes and microbial residues, but the effect of N deposition through the plant canopy, the major pathway of N deposition in nature, has not been explicitly explored. In this study, we investigated whether and how the quantities (25 and 50 kg N ha-1 yr-1) and modes (canopy and understory) of N addition affect soil microbial residues in a temperate broadleaf forest under 10-yr N additions. Our results showed that N addition enhanced the concentrations of soil amino sugars and microbial residual C (MRC) but not their relative contributions to SOC, and this effect on amino sugars and MRC ..., Soil physicochemical properties Soil pH was measured in a slurry (soil: water = 1: 2.5, w/v) with a pH meter (FiveEasy PlusTM FE28, Mettler Toledo). SOC, soil total nitrogen (TN), and total phosphorus (TP) concentrations were determined by the concentrated sulfuric acid-potassium dichromate external heating method, the concentrated sulfuric acid digestion-phenol blue colorimetric method, and the concentrated sulfuric acid digestion-molybdenum antimony anti-colorimetric method, respectively (Lu, 1999).
Soil microbial PLFAs The Soil microbial community was characterized by the phospholipid fatty acids (PLFAs) method (Bossio & Scow 1998). The concentration of each PLFA was calculated based on the 19:0 internal standard concentration. The PLFAs i14:0, i15:0, a15:0, i16:0, a16:0, i17:0, a17:0, a18:0, i18:0, a19:0, 16:1ω7c, 16:1ω9c, 17:1ω8c, 18:1ω7, cy17:0, and cy19:0 were used to indicate bacterial biomarkers. The PLFAs 18:1ω9c, 18:2ω6,9c, and 18:3ω6,9,12c were applied to denote fungal b..., , # Canopy and understory nitrogen additions differently affect soil microbial residual carbon in a temperate forest

[https://doi.org/10.5061/dryad.xksn02vqh](https://doi.org/10.5061/dryad.xksn02vqh)

## Description of the data and file structure

The data from 20 experimental plots including five treatments of control (without N addition, CT), canopy low-N addition ((25 kg N ha-1 yr-1, CN25), canopy high-N addition (50 kg N ha-1 yr-1, CN50), understory low-N addition (25 kg N ha-1 yr-1, UN25), and understory high-N addition (50 kg N ha-1 yr-1, UN50), four replicated plots for each treatment, were collected. The data include soil physiochemical properties (soil pH, soil organic carbon (SOC), soil total nitrogen (TN), soil total phosphorus (TP) in 0-10 and 10-20 cm layers), soil microbial biomass ( represented by phospholipid fatty acids, PLFAs), microbial activities (determined by microbial respiration under incubation), soil amino sugar concentration, the relative contribution of tota...