Performance of grass and rainforest riparian buffers in the wet tropics, Far North Queensland. 2. Water quality

摘要: Riparian lands have the potential to buffer streams from hillslope sediment and nutrient transport. Most research on buffers has been conducted under laboratory or manipulated field experimental conditions. Few quantitative data exist performance natural This study reports measured soil loss evaluates effectiveness of riparian planar convergent slopes hydrological conditions in Far North Queensland. The are extreme for testing as land is steep, intensely cropped receives high intensity rainfall. Hillslopes with bananas were monitored using paired flumes. Runoff, bedload, suspended loads leaving crop (upper sites) (lower sites). Highly variable losses 70 t/ha per wet season recorded. High rates areas steep gradient little ground cover experiencing rainfall intensity. On slopes, even loss, grass strips able trap >80% incoming bedload. Total N (TN), total P (TP) (SS) reduced between 25 65% by slope within first 15 m moderately buffer. Loads often higher than those delivered crop, due seepage after prolonged frequency Under these buffer's main function prevent erosion rather nutrients. Results a highly 5-ha hillslope, suggest that be more effective such topography, they should also placed at end rows, where contributing smaller. Flow was concentrate least one occasion scour 30-cm-wide channel through entire width releasing previously trapped material making ineffective. A remnant rainforest buffer, receiving runoff slope, acted temporary store nutrients reworked during subsequent events. demonstrates both need managed sloping tropical identifies limitations their effectiveness.