Quantity and quality of bracken throughfall, stemflow and litterflow in a Dartmoor catchment.
Abstract
The quantity and quality of throughfall, stemflow and litterflow under typical bracken(Pteridium aquilinum)-infested Agrostis/Festuca pastures in an upland catchment on south-west Dartmoor, Devon, England, over a period of one year were studied.newline˜Interception of incident rainfall over the 5-month bracken growth period and over 1 year was 48.7% and 20%, respectively. Throughfall and stemflow chemistry under bracken was significantly different from that of precipitation above the bracken canopy. Potassium comprised 40% of total base cations in summer. Particularly high levels of potassium release were recorded in October during senescence and following the death of bracken fronds. Quantity and quality of litterflow were also measured. Most litterflow was locally derived and only travelled laterally through the litter layer for a few metres before passing into the soil to join the soil water. The chemical composition of litterflow was very different to that of throughfall and stemflow and there was a sixfold increase in potassium concentration in litterflow compared to throughfall and stemflow. Potassium release from bracken into litterflow was greatest in October. Mechanisms for the possible release of cations from bracken during its growth cycle are suggested. The implications of these results for the upland catchments of Britain, where bracken invasion is occurring, are discussed.