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 (&lt;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.本因子显著性综述共纳入94项研究。该综述补充了此前定量综述所用的75项记录污染物负荷削减量的研究，并以差异化视角重新审视了其研究结论。沉积物、硝酸盐、溶解态磷（dissolved P）与总磷（total P）均得到充分研究（每项指标对应≥35项研究），总氮（total N）与径流量的研究程度中等（每项对应≥19项研究），而农药、铵态氮与大肠菌群的研究最为有限（每项对应<19项研究），仅1项研究涉及胶体磷。研究证据主要来源于暖温带气候区，雪带气候区的相关证据较少，干旱区与热带地区的证据则最为匮乏。相关研究主要针对模拟环境（即脱离景观背景的样地或土壤柱体）与人工构建的RBZ（在真实环境背景下设置的缓冲带）中的效应展开，对半自然河岸带的相关研究较少。降雨设置涵盖模拟降雨与天然降雨两种类型；仅沉积物截留的相关证据大量采用人工样地及/或模拟降雨试验的研究结果。研究采用的时间尺度各不相同：人工样地研究的持续时间通常较短，仅涉及少量单次降雨事件，而在景观背景下开展的缓冲带研究则往往时长超过一年。研究的空间尺度以样地尺度为主，河段至流域尺度的相关研究相对较少。