Temperature and moisture trends in non‐sorted earth hummocks and stripes on the Old Man Range, New Zealand: implications for mechanisms of maintenance

The mechanisms of maintenance of earth hummocks and non‐sorted stripes in seasonally frozen ground on the Old Man Range, Otago, New Zealand were investigated. These landforms are hypothesised to be active periglacial landforms maintained by seasonal movement of moisture down an energy gradient. We tested three hypotheses: 1) freezing should occur predominantly in the crests of the stripes and hummocks; 2) differential freezing patterns should be consistent between years; and 3) in the presence of a temperature gradient (i.e. in winter), soil moisture content should be greater in crests than in furrows. An array of 39 thermistors at each of two sites was used to monitor soil temperature gradients during three winters, and replicate soil cores were taken in autumn and winter to determine soil moisture gradients. Freezing occurred mainly in the crests and sides (heavily influenced by aspect), and patterns of freezing showed strong interannual consistency, supporting our first two hypotheses. Soil in crests had a higher moisture content in both freezing and thawed seasons, which was inconclusive relative to the expected water gradient. Copyright © 2008 John Wiley & Sons, Ltd.