Table 1.
A summary of site characteristics and soil chemical and physical properties along the elevation gradient.
| Total phosphorus (mg per gram) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Total nitroge n (%) | Leaf litter C:N | |||||||||||
| Vegetation type | Elevation (m asl) | Mean annual air temp (°C) | Mean annual precipitation (mm per year) | Soil organic horizon depth (cm) | Mean (M) | Standard error (SE) | M | SE | Soil pH | M | SE | Relative recalcitrance of soil C |
| Lowland rainforest | 194 | 26.4 | 2730 | 1 | 0.35 | 0.03 | 0.49 | 0.07 | 3.7 | NA | 0.91 | |
| 210 | 26.4 | 3199 | 2 | 0.23 | 0.03 | 0.18 | 0.03 | 4.0 | 29.9 | 7.7 | NA | |
| Premontane rainforest | 1000 | 20.7 | 3087 | 4 | 1.34 | 0.12 | 0.73 | 0.05 | 4.7 | 23.7 | 1.9 | 0.53 |
| Lower montane cloud-forest | 1500 | 17.4 | 2631 | 16 | 0.91 | 0.12 | 1.36 | 0.37 | 3.5 | 29.1 | 5.3 | 0.58 |
| 1750 | 15.8 | 2631 | 10 | 1.56 | 0.50 | 1.44 | 0.09 | 3.6 | NA | NA | ||
| 1850 | 16.0 | 2472 | 16 | 1.86 | 0.24 | 0.76 | 0.06 | 3.5 | NA | NA | ||
| 2020 | 14.9 | 1827 | 17 | 2.00 | 0.24 | 0.71 | 0.10 | 3.4 | NA | NA | ||
| Upper montane cloud-forest | 2520 | 12.1 | NA | 14 | 1.73 | 0.34 | 0.98 | 0.14 | 3.7 | NA | NA | |
| 2720 | 11.1 | 2318 | 21 | 1.64 | 0.25 | 0.87 | 0.19 | 3.6 | 39.6 | 2.3 | NA | |
| 3020 | 9.5 | 1776 | 17 | 1.57 | 0.21 | 0.92 | 0.13 | 3.4 | NA | NA | ||
| 3025 | 11.1 | 1706 | 23 | 2.39 | 0.12 | 1.09 | 0.08 | 3.5 | 71.5 | 19.2 | 0.52 | |
| 3200 | 8.9 | NA | 12 | 2.42 | 0.20 | 0.91 | 0.02 | 3.5 | NA | NA | ||
| 3400 | 7.7 | 2555 | 14 | 2.49 | 0.17 | 1.09 | 0.09 | 3.4 | NA | NA | ||
| Grassland | 3644 | 6.5 | NA | 4 | 1.44 | 0.07 | 0.92 | 0.13 | 3.4 | NA | NA |
Note: Leaf-litter carbon-to-nitrogen ratios (C:N) are the average of three dominant species for respective plots (Salinas et al. 2011). Total nitrogen and phosphorus were determined for surface soil (0–10 centimeters, cm, in depth). Soil pH was measured in water. The relative recalcitrance of soil carbon is the ratio of the proportion of total soil carbon in recalcitrant carbon divided by the proportion in recent plant-derived carbon within surface mineral soils as determined by nuclear magnetic resonance (percentage of carbon in groups: alkyl/O-alkyl; Zimmermann et al. 2012). n = 5. Abbreviations: °C, degrees Celsius; cm, centimeters; m asl, meters above sea level; mg, milligrams; mm, millimeters; NA, data not available (Girardin et al. 2010, Rapp and Silman 2012, Whitaker et al. 2014b).