Drivers of carbon stocks in forest soils at varying elevations in the northwest Andes of Colombia

Soil represents the most important terrestrial carbon sink on Earth. Using data from 9 forest sites located across an elevational gradient (range: 167–2928 m a.s.l.) in northwestern Colombia, which spans a wide range of climate, forest, and soil types, we aim to answer the following research questions: (i) How do SOC stocks change along the elevational gradient or between lowlands and highlands? (ii) What are the main drivers of SOC stocks along elevational gradients? Using structural equation modeling (SEM), we found that climate and soil fertility explained 67% of the variation in SOC stocks across the entire dataset, with SOC stocks declining under warmer and wetter conditions, but increasing with higher soil N:P ratios. Because soil mineralogy was closely correlated with elevation (all lowland were kaolinites while all highland sites were allophanes), SEM models for lowland and highland forests were also run separately. Lowland forests were dominated by trees associated with ar..., In each of the 9 study sites, a 100 m × 100 m (1-ha) plot was established in areas covered by natural forests. Each plot was divided into 25 contiguous subplots of 20 m × 20 m (0.04 ha). To assess soil organic carbon (SOC) in each 1-ha plot, we used a systematic sampling design that selected 15 subplots distributed in three transects of 20 m × 100 m each, separated by 20 m between them (Figure S1). In each subplot, we took a sample centrally located with a soil auger. For each soil core, we removed the organic litter layer and extracted a soil sample centered around 10 cm depth, which represents the first 20 cm of soil. Soil samples were taken using a 4 cm wide and 5 cm long (62.83 cm3) cylinder. The samples were preserved in paper bags and returned to the laboratory. One sample from one plot was missed, meaning that only 134 samples were used for the analyses.
Soil cores were oven-dried at 105 °C to a constant weight. The samples were then crushed and sieved to 2 mm to remove all root..., # Data from: Drivers of carbon stocks in forest soils at varying elevations in the northwest Andes of Colombia

Dataset DOI: [10.5061/dryad.f7m0cfz8t](https://doi.org/10.5061/dryad.f7m0cfz8t)

## Description of the data and file structure

Data employed to run the analyses. We assessed the effect of temperature, precipitation, soil phosphorous/nitrogen contents, clay mineralogy, and root symbiont association (measured as the proportion of trees associated with ectomycorrhizas, arbuscular mycorrhizas, or nitrogen-fixing bacteria) on soil organic carbon (SOC) in 9 permanent plots located along an elevational gradient ranging from 167 and 2928 m asl in northwestern Colombia.

### Files and variables

#### File: Calderon_et_al_SOC_data_rev.xlsx

**Description:** Data used to run the analyses. See second tab for units of measure.

##### Variables

| elev | Elevation |
| :------------ | :----------------------..., ,