Cation Exchange Capacity and Base Saturation Variation among Alberta, Canada, Moss Peats

Abstract

Variations in moss peat cation exchange capacity (CEC) and base saturation (BS) can result in inconsistent initial pH in moss peat-based substrates created using standard formulas for limestone additions and can lead to subsequent drift from the initial pH in those substrates. This study was conducted to determine the extent of such variation. CEC and BS were measured in three replications on 64 moss peat samples that were selected from three mires across Alberta, Canada, to represent maximum gradients in plant species composition within six degrees of decomposition acceptable for professional peat-based substrates. CEC ranged from 108 to 162 cmolÁkg -1 (meqÁ100 g). Averaged overall samples, BS ranged from 15% to 71% of CEC and calcium accounted for 68%, magnesium for 25%, sodium for 5%, and potassium for 1.4% of BS. CEC was positively correlated to the amount of Sphagnum fuscum (Schimp.) Klingrr. in the sample (r = 0.22). BS was positively correlated to the amount of sedge (r = 0.28). Neither CEC nor BS was influenced by degree of decomposition (r = 0.002 and r = 0.08, respectively). Moss peats with high CEC have a greater buffering capacity than those with low CEC, resulting in less pH drift. Moss peats with high BS should have a low neutralization requirement to achieve a target pH. Understanding the species composition in peat-based substrates can alleviate problems of inconsistent initial pH and subsequent pH drift.

Similar cation exchange capacities among bryophyte species refute a presumed mechanism of peatland acidification

“…The overall lower amount of free protons found in the throughfall water of the F þ R acidification treatment is probably due to the high acid neutralizing capacity of the Ca-rich (see Appendix) fen water. The confidence in our results is strengthened by the fact that after recalculations to correct for differences in methods and data presentation, our actual CEC values broadly correspond to those reported earlier for mosses in those investigations applying similar nondestructive methods (Clymo 1963, Bates 1982, Buscher et al 1990, Rippy and Nelson 2007 and for AC of a few specific Sphagnum and brown mosses (Glime et al 1982, Kooijman and Bakker 1994, Rippy and Nelson 2007. Several studies, where CEC measurement methods involved destruction of plant tissues (e.g., Knight et al 1961, Richter and Dainty 1989, Tipping et al 2008, report CEC values that are 100-500% higher than ours.…”

“…The confidence in our results is strengthened by the fact that after recalculations to correct for differences in methods and data presentation, our actual CEC values broadly correspond to those reported earlier for mosses in those investigations applying similar nondestructive methods (Clymo 1963, Bates 1982, Buscher et al 1990, Rippy and Nelson 2007 and for AC of a few specific Sphagnum and brown mosses (Glime et al 1982, Kooijman and Bakker 1994, Rippy and Nelson 2007. The overall lower amount of free protons found in the throughfall water of the F þ R acidification treatment is probably due to the high acid neutralizing capacity of the Ca-rich (see Appendix) fen water.…”

Influence of physical and chemical properties on the low‐frequency complex conductivity of peat

“…For higher degrees of humification, openings in the cell membranes of leaves and stems become larger as membranes decompose and eventually disappear, leaving an open framework structure (Landva and Pheeney 1980), reducing the polarizability. The lack of correlation between decomposition and CEC can be explained by the different botanical composition of the tested peat, as CEC depends on species distribution (Rippy and Nelson 2007). A significant correlation between CEC and low‐frequency polarization of peat was not found, in agreement with results of a previous study on clay‐rocks (Cosenza et al .…”

“…The total amount of cations absorbed by the negatively charged surface of peat is called cation exchange capacity (CEC). Very diverse values of peat CEC are found in literature, because CEC varies with species composition (Rippy and Nelson 2007). Thorpe (1973) reported a range of values from humus (65 cmol/kg) to sphagnum moss peat (122 cmol/kg), which has a much higher CEC than other plants (Moore and Bellamy 1974), whereas a much lower value (10.6 cmol/kg) was found for fen peat (Gogo and Pearce 2009).…”

Limestone Particle Size and Residual Lime Concentration Affect Ph Buffering in Container Substrates

“…These differences in buffering capacity, which occur over the pH range in which most horticultural crops are grown, could contribute to problems of rapid substrate-pH changes during the course of crop production. Major substrate properties that contribute to the buffering capacity of peat are cation exchange capacity (CEC) and base saturation (BS) [fractional calcium (Ca 2+ ), magnesium (Mg 2+ ), potassium (K + ), and sodium (Na + )] (Rippy and Nelson, 2007).…”