Table 2 in Temperate grassy wetlands of South Africa: Description, classification and explanatory environmental factors

Table 2 Environmental variables and their measurement or assessment that have been included in the National Wetland Vegetation database. The variables indicated with an asterisk were not available for all sample plots, only for those plots where a soil sample was taken for analysis.
VariableType of variableMethod of measurementMethod of assessmentUnitsTransfor-mationAbbreviations or categories used in ordination diagramHGM_typeNominalLevel 4 of SAWCS classification system (Ollis et al. 2013), Depression, Floodplain, Valley bottom, Valley bottom with channel, Seepage, Channeln.a.Depression, Fldplain, VB, VB-wc, Seepage, ChannelSoil depthNominalSoil augering, subdividing into two categories: deep soils (>50 cm), shallow soils (<50 cm)n.a.Soil_dp, Soil_shWetnessIndexAssessment of soil hydromorphic features following Kotze et al. (1996). Index: 1 = no wetland, 2 = temporary, 3 = temporary/seasonal, 4 = seasonal, 5 = semi-permanent, 6 = permanentn.a.WetnessSoil texture (1)NominalFeel of soil by touchn.a.Peat, Sand, Loam, Clay, Silt, GravelSoil texture (2)Ratio*Sieving and subdividing into three fractions Clay (<0.002 mm), Silt (0.002–0.05 mm), Sand (0.05–2 mm)mass %log%Sand, %Clay, %SiltSoil organic matter (1)IndexChecking colour of soil: mineral soils = 1, dark or humic soils = 2, peaty soils = 3n.a.OrganicSoil organic matter (2)Ratio*Walkley-Black methodmass %log%CarbonpHOrdinal*Water extraction of soil, using pH meter.n.a.*PHInundationRatioAssessed in field from standing watercmInundationAltitudeRatiousing GPSFinding locality in Google EarthmAltitudeSlopeRatioAssessed in fielddegreesSlopeElectrical conductivityRatio*Water extraction of soil, using conductivity metermS/cmlogECNitrogenRatio*Sums of measured concentrations of ammonium, nitrite and nitrate, converted towards mol N, converted back into mass Nmg/kglogNitrogenPhosphorusRatio*Bray I methodmg/kglogPhosphorusMajor CationsRatio*Using 1:10 water extraction of soilmg/kgStandardized, then logNa, Ca, K, Mg