H. Wayne Polley, Harold P. Collins, Lara G. Reichmann, and Philip A. Fay

CO2 and soil water potential as regulators of the growth and N fraction derived from fixation of a legume in tallgrass prairie communities

Plant and Soil

USDA–Agricultural Research Service, Grassland, Soil & Water Research Laboratory, Temple, Texas, 76502, USA

Author for correspondence: Wayne Polley [email protected] Online Resource 1 Management regime and initial vegetation for sites at which each of the three soil types used in the LYCOG experiment was collected. Note that the legume Desmanthus, which is characteristic of native tallgrass prairie vegetation, was not present in vegetation at sites from which soils were collected.

Collection Site Initial Dominant Soil type Soil series location management vegetation legume silty clay Austin Temple, recently forbs and Medicago mollisol (Udorthentic Texas, USA grazed pasture perennial C4 lupulina L. Haplustol) grasses [e.g., Bothriochloa ischaemum (L.) Keng] sandy loam Bastsil (Udic Morgan’s wildlife forbs and Vicia sativa alfisol Paleustalf) Point, Texas, management perennial C4 L. USA area grasses [e.g., Sorghum halepense (L.) Pers.] clay vertisol Houston Riesel, actively forbs and Medicago Black (Udic Texas, USA grazed pasture perennial C4 lupulina L. Haplustert) grasses [e.g., Buchloe dactyloides (Nutt.) Engelm.] Online Resource 2 Depth profiles of soil properties (SE) for each of the soil types used in the LYCOG experiment. Data are from Fay et al. (2009).

Soil type/ Sand (%) Silt (%) Clay (%) Total C Organic C Total N pH Depth (%) (%) (%) (cm) silty clay 0-10 12.2 45.9 41.9 8.55 1.98 0.15 8.04 (0.4) (0.7) (0.6) (0.08) (0.04) (0.010) 30-50 11.9 46.3 41.8 8.69 0.69 0.05 8.10 (0.8) (1.1) (1.1) (0.11) (0.03) (0.002) 50-100 11.7 48.4 39.9 8.66 0.41 0.03 8.03 (0.7) (1.3) (1.6) (0.09) (0.03) (0.002) sandy loam 0-10 72.8 19.7 7.5 0.77 0.71 0.08 8.06 (0.6) (0.4) (0.4) (0.06) (0.06) (0.006) 30-50 60.2 25.7 14.0 0.17 0.18 0.03 7.83 (2.8) (0.7) (3.3) (0.01) (0.02) (0.007) 50-100 48.2 25.7 26.1 0.21 0.21 0.04 7.17 (0.9) (1.8) (2.3) (0.01) (0.02) (0.004) clay 0-10 11.2 39.5 49.2 5.05 2.38 0.21 7.60 (0.5) (1.0) (1.2) (0.16) (0.07) (0.009) 30-50 9.5 35.5 54.9 4.09 1.32 0.08 7.83 (0.1) (0.9) (0.9) (0.05) (0.05) (0.004)

50-100 8.8 35.7 55.4 3.98 0.99 0.05 7.91 (1.0) (0.8) (0.7) (0.05) (0.08) (0.004) Online Resource 3 Leaf concentrations of Ca and Mg in Desmanthus leaves were negative functions of CO2 treatment for both the clay and silty clay soils. Linear regressions were derived from a mixed-model repeated measures analysis of variance of data from 4 years (3 years for [Ca] for the clay; many data points for the 4th year were missing) [P = 0.002, 0.012, 0.0004,

0.005 for [Ca] and [Mg] for the clay and silty clay, respectively]. Year x CO2 interactions were not significant. Online Resource 4 Seasonal averages (SE) per soil type of soil solution levels of selected elements as collected on resin probes inserted vertically into the upper 15 cm of soil (μg/10 cm2 ion-exchange surface area/month). Values represent averages across CO2 concentrations of monthly samples collected during the third growing season of CO2 treatment.

Element Soil silt clay sandy loam clay Nitrogen 7.9 7.1 7.9 (0.4) (0.5) (0.5) Phosphorus 1.7 4.4 2.2 (0.1) (0.3) (0.2) Iron 29.3 10.8 8.5 (5.0) (3.2) (2.5) Calcium 22.9 x 102 14.3 x 102 18.8 x 102 (39.8) (46.6) (55.2) Magnesium 96.0 154.3 85.2 (1.7) (4.4) (1.7) Potassium 55.5 140.9 49.8 (2.2) (7.8) (2.1) Manganese 5.2 4.5 2.1 (0.7) (0.9) (0.4) Zinc 1.3 1.26 1.0 (0.1) (0.1) (0.1)