Inter-specific variation in foliar nutritional responses to disturbance by small coupe harvesting varies with landscape position

The effects of small coupe harvesting on the foliar nutritional characteristics of four indigenous plant species were investigated in a New Zealand Nothofagus truncata forest. The coupes were established in 1994, and installed in replicated logged and unlogged pairs of plots on the ridge line, face and gully of a valley, allowing variation with landscape position to be assessed. Foliar sampling occurred in March 2006. Logging significantly increased foliar nitrogen and phosphorous concentrations. Logging increased foliar δ15nitrogen, attributed to increased rates of mineralisation and nitrification, and decreased nutrient demand. Foliar calcium, magnesium and strontium concentrations were significantly decreased by logging, and this was considered the result of increased leaching in the logged coupes. The effect of the harvest treatment varied considerably with plant species, and it was determined that the examination of multiple plant species is critical to accurately assessing the effect of logging on nutrient availability. Foliar nitrogen, calcium and strontium concentrations decreased significantly from ridge line to gully coupes, and this was attributed to water movement. The effect of logging on foliar calcium and strontium concentrations also varied significantly with landscape position. It was concluded that small coupe harvesting in N. truncata forests causes substantial long term disturbances to nutrient dynamics, which may alter the relative diversity of the regenerating plants in the coupes.