Table 7. Summary of each column included in the soil dataset, including column number, column name, data format, units, range of values, and a short description.

Col.	Col. name	Format	Units	Range	Description
1	PROJECT	categorical	—	—	Project name
2	YEAR	numerical	year	2001–2007	Sampling year
3	MONTH	numerical	month	6–10	Sampling month
4	DAY	numerical	day	1–31	Sampling day
5	ECOREGION	categorical	—	—	EPA Level III Ecoregion
6	CLUSTER	categorical	—	—	General sampling area
7	PLOT_ID	numerical	—	1–948	Plot identification number
8	PLOT_ID_ALT	numerical	—	—	Alternative PLOT_ID is previously sampled
9	PLOT_ID_AMERIFLUX	categorical	—	—	AmeriFlux identification
10	LATITUDE	numerical	decimal degree	37.784–45.948	Plot latitude (WGS84)
11	LONGITUDE	numerical	decimal degree	−123.904–−117.1309	Plot longitude (WGS84)
12	ELEVATION	numerical	m	138–2758	Elevation above sea level
13	MAT	numerical	°C	2.43–13.53	Mean annual temperature (1984–2013)
14	MAP	numerical	mm yr−1	414–2,839	Mean annual precipitation (1984–2013)
15	SOIL_DEPTH	numerical	cm	21–100	Total soil depth
16	SOIL_LAYER	categorical	—	top/mid/bottom	Soil layer sampled
17	UPPER_DEPTH_OF_SOIL_LAYER	numerical	cm	0–50	Upper depth of the soil layer
18	LOWER_DEPTH_OF_SOIL_LAYER	numerical	cm	3–103	Lower depth of the soil layer
19	BULK_DENSITY_OF_SOIL_LAYER	numerical	kg m−2	2–884	Bulk density of the soil layer
20	CARBON_CONTENT_OF_SOIL_LAYEL	numerical	g C m−2	10–24,480	Carbon content of the soil layer
21	NITROGEN_CONTENT_OF_SOIL_LAYER	numerical	g N m−2	0–1330	Nitrogen content of the soil layer
22	PH_OF_SOIL_LAYER	numerical	—	3.87–7.45	pH of the soil layer
23	VOLUME_FRACTION_OF_SAND_IN_SOIL_LAYER	numerical	%	17–86	Volume fraction of sand in the soil layer
24	VOLUME_FRACTION_OF_SILT_IN_SOIL_LAYER	numerical	%	11–66	Volume fraction of silt in the soil layer
25	VOLUME_FRACTION_OF_CLAY_IN_SOIL_LAYER	numerical	%	1–50	Volume fraction of clay in the soil layer