Nitrogen enrichment promotes isopods through reduced carbon and nitrogen stoichiometric mismatch with understory plants

As key detritivores and fungal grazers, terrestrial isopods (Isopoda: Oniscidea) play crucial roles in mediating ecosystem processes. Although nitrogen enrichment represents a major global change driver known to modify soil food webs, its long-term effects on the abundance of these keystone detritivore remain largely unknown. For this study, we conducted a 10-year nitrogen enrichment experiment to monitor the active density and biomass of terrestrial isopods across eight seasons over two years during 2020 to 2022 in 13- and 17-year-old poplar plantations, respectively. Our results revealed that nitrogen enrichment increased the abundance and biomass of terrestrial isopods. For nitrogen enrichment levels of 5, 10, 15, and 30 g N m⁻² yr⁻¹, the corresponding increases in isopods active density were estimated to be 11.6%, 24.5%, 38.9%, and 92.9 % higher, respectively, relative to the ambient N level. Furthermore, nitrogen enrichment did not alter the carbon to nitrogen ratio (C:N) of the bo..., This dataset originates from a long‐term nitrogen (N) enrichment experiment conducted in coastal poplar (Populus deltoides cv. “I-35”) plantations at the Dongtai Forest Farm, Jiangsu Province, eastern China (32°52′ N, 120°49′ E). The region has a temperate monsoon climate with a mean annual temperature of 14.9 °C and precipitation of ~1,050 mm.
The experiment was established in May 2012 in two stand ages (13- and 17-year-old plantations at the start of the experiment). A randomized block design included five N enrichment levels (0, 5, 10, 15, and 30 g N m⁻² yr⁻¹ as NH₄NO₃) with four replicate blocks per level. Each treatment subplot measured 25 × 30 m with 10 m buffers, and blocks were separated by ≥500 m. Nitrogen solutions were applied six times annually during the growing season (May–October) to simulate chronic atmospheric deposition; control plots received equal volumes of water only.
Isopod sampling was conducted across eight seasonal time points from August 2020 to June 2022 usin..., ---

# Nitrogen Enrichment and Isopods: Open Source Data

---

We provide the raw data (**eN_Isopod.csv**), isopod tissue stoichiometry data (**eN_Isopod_Stoichiometry.csv**), and the R analysis scripts used in the study *Nitrogen enrichment promotes terrestrial isopods through reduced carbon and nitrogen stoichiometric mismatch with understory plants* (Ni et al., 2025).
These datasets come from a 10-year nitrogen enrichment experiment in poplar plantations (Dongtai Forest Farm, Jiangsu, China) and include repeated measurements of isopod abundance/biomass, plant community composition, and C:N stoichiometry across eight seasonal sampling events (2020–2022).

## Descriptions

The data (.csv) and code (.R) are provided in `csv-data-r-code.zip`, hosted on Dryad.

### **eN_Isopod.csv**

* *TimeLine*: Sampling date (MM/DD/YYYY)
* *Year*: Sampling year
* *Month*: Sampling month
* *Season*: Sampling season (Summer, Autumn, Winter, Spring)
* *Age*: Stand age of poplar plantation (“13a” = 13-year...,