The north‐west of the Iberian Peninsula is crucial for conservation of Margaritifera margaritifera (L.) in Europe

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水土保持径流小区监测方法探讨——以甘肃省定西市安家沟监测点为例

径流小区在水土保持监测工作中发挥着非常重要的作用,是其它方法所不能替代的.要保证小区资料的准确性和可靠性,选择正确的观测方法和数据处理方法是关键.在半干旱地区,降雨场次的划分是区分次降雨径流的主要依据,特别是在阴雨连绵的情况下,就更需要合理划分降雨径流的场次,以客观记录"次降雨径流"过程.本研究尝试用置换法处理水样,只需购置比重瓶即可进行测定,设备简单,快捷高效,既保证了数据质量,也能有效降低处理水样的经济成本.因而,建议在水土流失强度比较大的地区用置换法处理水样.同时,涉及径流小区的相关资料,也不能简单或盲目地直接引用,必须经过相应的修订和验证.     

Reliability of an expert-based runoff and erosion model: Application of STREAM to different environments

During the last decades, the European loess belt has been confronted with a significant increase in environmental problems due to erosion on agricultural land. Spatially distributed runoff and erosion models operating at the catchment scale are therefore needed to evaluate the impact of potential mitigation measures. Expert-based models offer an alternative solution to process-based and empirical models, but their decision rules are only valid for the local conditions for which they have been derived. The STREAM model, which was developed in Normandy (France), has been applied in two Belgian catchments having a similar soil texture, as well as in a catchment of southern France differing by soil, land use and climate characteristics. The performance of hydrological models can be assessed for instance by calculating the Nash–Sutcliffe efficiency criterion (E_NS). When applied to Belgium, the model results are satisfactory to good after an adaptation of the decision rules (0.90 < E_NS < 0.93 for runoff predictions and 0.85 < E_NS < 0.89 for erosion predictions). Given the important environmental differences between Normandy and southern France, the model rules were also adapted for application in the latter environment. Unfortunately, the quality of runoff predictions was insufficient to simulate erosion in southern France. In conclusion, STREAM is a reliable model providing satisfactory runoff and erosion predictions in the regions where hortonian overland flow dominates. Nevertheless, an adaptation of decision rules based on local multi-scale (plot, field, catchment) data is needed, before running the model. STREAM can then serve as a decision support tool to design for instance flood control measures.     

A bird's‐eye view of reservoirs in the Mississippi Basin tips a need for large‐scale coordination

Reservoirs are mostly managed at local scales as spatially independent units. A basin‐scale perspective may increase awareness at a broader scope and generate insight not evident at local scales. We examined the array of reservoir attributes and fisheries in the Mississippi Basin to identify management opportunities. The basin is the third largest in the world and includes over 1,700 reservoirs >100 ha, the most of any river basin. Our bird's‐eye view shows a piecemeal approach where reservoirs are mostly administered at the local level. Basin‐wide or catchment coordination to holistically address problems that recur across the basin is mostly lacking. A basin‐wide coordination arrangement could facilitate various facets of reservoir management. We reviewed governance arrangements in major river basins across the globe and concluded that the basin‐wide administrative layer we encourage for the Mississippi Basin may already exist in some basins but may not be directly applicable everywhere.     

The long-term effects of catchment liming and reduced sulphur deposition on forest soils and runoff chemistry in southwest Sweden

Whole catchment liming or forest liming has been proposed and implemented as a countermeasure to the effects of elevated sulphur deposition. Since the end of the 1980s the Swedish Forest Agency has undertaken experimental forest liming experiments in selected catchments in southern Sweden. These studies were with low doses (3 tonnes ha⁻¹) of lime (CaCO₃) and dolomite (CaMg(CO₃)₂). Data from both soil samples and stream water samples have been collected for the 16 years following treatment. The stream data has been complemented with data from untreated catchments, from the Swedish monitoring stream network. Significant differences due to treatment were seen for Ca, cation exchange capacity (CEC) and base saturation (BS) in the humus layer, none of these variables showed a statistically significant change in the mineral soil due to treatment alone. Soil samples from both the treated and untreated sites showed temporal changes in both the humus layer and the mineral soils with increases in pH, Ca and CEC and decreases in BS and Al which were independent of treatment. A combination of treatment and time, gave significant changes in BS and TA down to 10 cm in the mineral soil. In the stream water samples no statistically significant differences were observed between treated and untreated sites. Regardless of treatment, the streams exhibited a general pattern of declining concentrations of SO₄, Ca, sum of base cations (BC) and increasing acid neutralizing capacity (ANC). In summary, the application of a low dose of lime (3 tonnes ha⁻¹) did not result in significant changes in surface water chemistry in the study catchments and changes in soil chemistry were mainly restricted to the humus layer during the 16 years following treatment. The natural recovery, as a result of reductions in sulphur deposition, dominated the effects and was clearly seen in both the treated and untreated study sites. MAGIC simulations indicate that this recovery will continue in the coming decades.     

Naturally acidic waterways: conceptual food webs for better management and understanding of ecological functioning

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滇池柴河流域蔬菜地土壤施用控释尿素与普通尿素的氮损失比较

在滇池柴河流域,蔬菜地施用的氮肥通过径流、淋溶和氨挥发等途径向水体迁移,对周围水体质量有较大影响。通过盆栽试验比较了控释尿素（3个氮水平：0 mg N/kg土、280 mg N/kg土和320 mg N/kg土）与普通尿素（4个氮水平：0 mg N/kg土、280 mg N/kg土、320 mg N/kg土和400 mg N/kg土）施用在柴河流域土壤所表现出的肥料氨挥发和氮淋失特征。结果表明,两种氮肥所有施氮水平处理的氮淋溶量都显著大于氨挥发量。在两种施氮水平下（320 mg N/kg土和280 mg N/kg土）,施用普通尿素产生的氨挥发量分别占施氮量的3.64%和3.57%,而施用控释尿素产生的氨挥发量分别占施氮量的3.64%和2.78%;施用普通尿素产生的氮淋失量分别占施氮量的14.38%（其中硝态氮占85.34%）和14.46%（其中硝态氮占95.70%）,施用控释尿素产生的氮淋溶量分别占施氮量11.60%（其中硝态氮占91.05%）和8.37%（其中硝态氮占96.84%）。硝态氮淋溶可能是柴河流域蔬菜地肥料氮素向水体迁移的主要途径。随着施氮量的减少,控释尿素的氮淋失量显著下降,而普通尿素的氮淋失量差异不显著。相同施氮水平下,普通尿素氮淋失量显著大于控释尿素。由此可见,控释尿素主要通过减少氮淋溶途径来减少氮损失。减量施氮结合控释尿素的施用对控制该地区氮肥施用对水体污染具有实际的指导意义。     

气候变化及人为活动驱动下的西南喀斯特生态水文研究评述

喀斯特地区地表关键带结构十分复杂,土层浅薄且持水能力弱,地下裂隙多而渗透速率快,导致地表水分亏缺频繁、生态脆弱、污染物扩散快速等一系列生态环境问题。喀斯特地区的合理开发利用和生态环境保护,对深刻理解其生态水文过程有着极大的诉求。迄今为止,喀斯特生态水文学已经获得了重要进展,极大地提升了人们对植被水分来源与耗散机理、坡面水文快速过程、环境变化的生态水文效应等方面的认识,并构建了多种模型,为喀斯特地区生态治理、环境保护和水资源合理利用等提供了理论依据和技术支撑。但受限于喀斯特地表结构的复杂性,目前所获得的结论也存在很多不足和不确定性。本文从喀斯特生态水文过程与机理、喀斯特流域生态水文和喀斯特生态水文模型研究三个方面概述了喀斯特生态水文研究进展,介绍了课题组在相关方面的主要成果,并提出了未来研究中应进一步重视的问题。     

无定河流域植被恢复对土壤团聚体及碳固定的影响

对无定河流域坡耕地和4、5、10、30、50年植被恢复样地土壤水稳性团聚体含量,全土样及不同直径水稳性团聚体中的有机质、速效磷含量进行了测定分析,计算了土壤有机碳密度,旨在评价植被恢复对土壤结构、养分及土壤固定的影响。结果表明:各样地全土样有机质和速效磷含量分别介于6.73~31.83 g·kg-1和1.93~14.72 mg·kg-1之间,不同直径团聚体有机质和速效磷含量分别介于7.15~26.03 g·kg-1和3.71~16.64 mg·kg-1之间。相对农地,植被恢复能明显增加表层土壤有机质含量和有机碳密度,杜梨群落增加幅度最高,增加值分别为24.93 g·kg-1和91.98 mg·cm-2;水稳性团聚体以0.05 mm和0.05~0.1 mm为主,含量分别在37.06%~57.22%和21.71%~29.76%之间;不同直径水稳性团聚体中有机质含量表现为2 mm至0.2~0.5 mm之间,直径愈小,有机质含量愈高,0.2~0.5 mm至0.05 mm之间,粒径愈小,有机质含量愈低;除1~2 mm团聚体中的速效磷含量最高外,2 mm至0.05 mm团聚体之间,粒径愈小,速效磷含量愈低。土壤有机碳密度与植被恢复年限呈线性正相关关系。相对于土壤碳固定,土壤抵抗水力侵蚀的能力需更长时间才能显著提高。相对慢速湿润,快速湿润条件下各直径水稳性团聚体有机质含量均较高。研究区大雨或暴雨是造成该区域土壤结构恶化和有机碳损耗的主要原因。     

陇中半干旱区集雨限灌对马铃薯干物质积累和产量的影响

研究了大田条件下集雨有限补偿灌溉对旱区马铃薯干物质积累分配和产量的影响。结果表明:进行有限补充灌溉对旱作马铃薯有显著的增产效果,其经济系数也得到相应提高,与对照(不灌水)相比,补灌处理产量增幅在3.91%~21.21%之间,苗期补灌45 mm与90 mm对马铃薯产量的补偿效应显著;补灌马铃薯干物质积累量与对照相比无显著差异,但花后干物质的分配运转,苗期补灌处理比对照移动量大,转换率高,有利于花后薯块营养物质的积累;薯块膨大期补灌45 mm和90 mm,在干物质积累和花后干物质转化方面均低于对照,增产效果也并不显著。