Qualitative Database on Buffer Factors

The factor significance review comprised 94 studies. This brought additional studies to those used earlier in the quantitative review (limited to 75 studies documenting mass load reductions) and queried the findings differently. Sediment, nitrate, dissolved and total P were well-studied (≥35 each), total N and runoff volume moderately studied (≥19 studies each) and pesticides, ammonium and coliforms least studied (<19 studies each), with only one study dealing with colloidal P. Evidence comes primarily from warm temperate climate zones, less from snow zone climates and most limited from arid and tropical regions. Studies described effects dominantly in simulated (ie a plot or soil monolith isolated from its landscape context) and created RBZ (a land change to a buffer in a realistic environmental context), with fewer studies in semi-natural riparian zones. There was a mixture of simulated or natural rainfall; only sediment retention evidence draws heavily on studies using artificial plots and/or simulated rain applications. A mixture of temporal scales was used; artificial plot studies tended to be of shorter duration with few isolated rain events, whereas studies of buffers in their landscape context tended to exceed one year. Study spatial scale was dominated more by plot scale investigations with fewer at reach to catchment scales.