Soil organic carbon data from: Soil organic carbon and root distribution in a temperate arable agroforestry system

These data describe organic carbon content and soil bulk density measurements taken at a site in Bedfordshire, England in 2011, described in: Upson, M.A. & Burgess, P.J., 2013. Soil organic carbon and root distribution in a temperate arable agroforestry system. Plant and Soil, 373(1-2), pp.43–58. The samples were collected by Matthew Upson as part of an MSc by research at Cranfield University in 2010-2011. The field site was Olney field, Silsoe, Bedfordshire (N52°0'8.06" W0°25'46.80": http://g.co/maps/5bnxx) at the Cranfield experimental farm. Samples were taken from an agroforestry experiment described in: Burgess PJ, Incoll LD, Corry DT, Beaton A, Hart BJ (2005) Poplar (Populus spp) growth and crop yields in a silvoarable experiment at three lowland sites in England. Agrofor Syst 63:157–169 Burgess, P.J. et al., 2003. The Impact of Silvoarable Agroforestry with Poplar on Farm Profitability and Biological Diversity Final Report to DEFRA, Silsoe: Institute of Water and Environment, Cranfield University. The data comprise 10 columns describing 216 measurements of soil organic carbon content, and associated bulk density measurements. Organic carbon was measured using a modified Walkley-Black method. Two methods of presenting soil organic carbon stock measurements are presented: the first using the 'fixed depth' method of bulk density x organic carbon content; then second, using the Equivalent Soil Mass (ESM) technique explained in: Ellert, B.H. and Bettany, J.R. (1995) ‘Calculation of organic matter and nutrients stored in soils under contrasting management regimes’, Canadian Journal of Soil Science, 75(4), pp. 529–538. We used a baseline bulk density of 1 g cm-3, following: Bambrick, A.D., Whalen, J.K., Bradley, R.L., Cogliastro, A., Gordon, A.M., Olivier, A. and Thevathasan, N. V. (2010) ‘Spatial heterogeneity of soil organic carbon in tree-based intercropping systems in Quebec and Ontario, Canada’, Agroforestry Systems, 79(3), pp. 343–353. This differs slightly from the iruginal paper, in which only the fixed-depth calculation method was used. See citation for details. year: Single integer 2011 ID: Code indentifying individual trees in the experiment closest to the soil carbon measurements. e.g.: 1CB4: Block one, Cropped treatment, Beaupre hybrid, tree 4. See Upson & Burgess (2013). block: Following the original experimental design, there are three replicate blocks (B1:B3). ctrltmt: This column describes whether the sample was taken from the silvoarable agroforestry experiment (tmt), or from surrounding arable controls (ctrl). treat: Cropping treatment. Either C for continuously cropped, or F for continously Fallow. dist_m: Distance of sample from sample tree in metres. depth_cm: Depth from which the sample was taken in cm: 5, 16, 30, 50, 83, 128. di_cm: Depth of assumed sampling increment centred on the sampling depth. OCC_g_100g: Uncorrected organic carbon content as determined by a modified Walkley Black dichromate digest. Presented as grams per 100 grams. BD_g_cm3: Soil bulk density, in grams per centimetre cubed. measured using the ring method described by Klute, A. (1986) Methods of Soil Analysis: Part 1 - Physical and Mineralogical Methods. 2nd edn. Wisconsin: American Society of Agronomy. mEquiv: Assumed mass of each soil layer sampled. In this case 1 gm cm-3 * di_cm * 10^4. mMeas: Actual measured mass from measured bulk density, i.e.: BD_g_cm3 * di_cm. tC: Depth adjusted required to reach mEquiv. Calculated from ((mEquiv - mMeas) * 10-4) / BD_g_cm3 SOC_ESM_Mg_ha2: Soil organic carbon stock (Mg ha-1) calculated from the equivalent soil mass technique by: (OCC_g_100g * 0.1) * BD_g_cm3 * tC * 10^4 * 10^-3. SOC_Mg_ha2: Soil organic carbon stock (Mg ha-1) caclulated using the fixed depth method: OCC_g_100g * BD_g_cm3 di_cm.