不同类型植被河岸缓冲带对模拟径流及总磷的消减研究

在九龙江上游北溪流域,选择杂交狼尾草(Pennisetum americanum×P.purpureum)、红花檵木(Loropetalum chinense var.rubrum)、红叶石楠(Photinia fraseri)3种植物及原生撂荒杂草地,构建对照(A)、草本(B)、灌草(C)和灌木(D)4种不同处理的植被缓冲带,通过模拟不同浓度面源污染下的农田径流,探讨不同植被组合对径流量及总磷的消减效果.结果表明:各缓冲带不同植被对径流量及总磷的消减效果均表现为草本灌草灌木,其中,草本缓冲带对径流量的消减率最高,达到86.93%,在高、低浓度进水时对总磷浓度的消减分别为95.20%、80.69%;4种不同植被缓冲带对总磷浓度的消减效果随缓冲带宽度的增加均出现上升的趋势,其中,前半段消减效果最佳,后半段消减趋势减缓;高浓度污染进水条件下缓冲带对总磷的消减效率高于低浓度进水;4种缓冲带对磷总量的消减量分别为27.70、28.02、28.06和26.94 g.研究成果可为九龙江上游河岸缓冲带建设及流域氮磷污染率治理和生态评价提供科学示范及理论依据.     

水库出流对水库环境容量的影响研究

水库的出流是影响水库流场的重要因素,也是影响水库水环境容量的重要因素。文章以某水库为例,利用计算流体力学及水质计算软件计算了水库在不同泄流宽度下出流的流量,并根据不同泄流宽度下水库的流场和浓度场计算了对应的水库环境容量值,分析了出流宽度、出流流量和水环境容量三者之间的关系。     

东江干流河岸带植物群落类型分布格局研究

对东江干流河滨带植物群落类型进行详细调查,并对其空间分异情况进行了系统研究。根据野外调查所获90个样地数据资料,结合应用了TWINSPAN、DCA、CCA等数量分析方法。调查中共发现样内植物56科187属271种;TWINSPAN分类将该90个样地归并划分为15个群丛;DCA排序的第一轴的累积变异量为9.3%,前两轴的累积变异量为15.8%;CCA排序前两轴对物种-环境关系的解释量为62.6%;DCA、CCA排序分析揭示了群落在上、中、下游的分布情况,以及这些群落的分布格局与温度、人类干扰强度、土壤含水量等因子之间的相互关系。     

Physical and Chemical Connectivity of Streams and Riparian Wetlands to Downstream Waters: A Synthesis

Streams, riparian areas, floodplains, alluvial aquifers, and downstream waters (e.g., large rivers, lakes, and oceans) are interconnected by longitudinal, lateral, and vertical fluxes of water, other materials, and energy. Collectively, these interconnected waters are called fluvial hydrosystems. Physical and chemical connectivity within fluvial hydrosystems is created by the transport of nonliving materials (e.g., water, sediment, nutrients, and contaminants) which either do or do not chemically change (chemical and physical connections, respectively). A substantial body of evidence unequivocally demonstrates physical and chemical connectivity between streams and riparian wetlands and downstream waters. Streams and riparian wetlands are structurally connected to downstream waters through the network of continuous channels and floodplain form that make these systems physically contiguous, and the very existence of these structures provides strong geomorphologic evidence for connectivity. Functional connections between streams and riparian wetlands and their downstream waters vary geographically and over time, based on proximity, relative size, environmental setting, material disparity, and intervening units. Because of the complexity and dynamic nature of connections among fluvial hydrosystem units, a complete accounting of the physical and chemical connections and their consequences to downstream waters should aggregate over multiple years to decades.     

河岸带地下水营养元素和有机质变化及与洪水的响应关系研究

河岸带地下水和河水存在复杂的交互作用,地下水和地表水存在明显的补排关系,洪水事件是影响河岸带地下水水质波动的重要水文过程. 以黄河湿地国家级自然保护区孟津湿地为研究对象,通过河岸带地下水营养元素指标(特别是小浪底水库调水调沙期间)野外定位观测,深入分析了河岸带地下水水质变化及其与洪水的响应关系. 结果表明,河岸滩区的农业开发存在明显的氮、磷下渗流失风险. 临近河岸的农耕旱作区,是河流与人工湿地之间一个特殊的氮污染物控制单元,对地下水和河流之间的氮迁移隔离起着极为重要的作用. 在人工湿地,农家粪作为底肥加入可能是磷下渗流失的重要源头,进入地下水中的磷顺着水力坡度还发生着显著的横向迁移,尤其在调水期横向迁移更加明显. 河岸滩区的开发类型及其耕作制度对地下水的硝氮含量产生重要的影响. 在鱼塘区,常年的土壤厌氧环境加重了氮的下渗迁移和积累;在荷塘区,春夏季节,土壤淹没呈厌氧环境,氮迁移和硝化作用显著,在秋冬季节,土壤呈好氧环境,氮硝化作用显著发生,全年氮达到相对平衡的状态;距离河岸50～200 m之间氮的硝化-反硝化作用强烈,是一个高效的微生物氮净化单元. 人工湿地施用的农家粪是有机物流失的重要源头,河岸滩区土壤质地呈沙性,渗透能力强,土壤保水保肥能力差,在此区进行农业活动,尤其是人工湿地开发中大量施用肥料,容易造成土壤表层有机质和氮磷养分因灌溉而导致的下渗流失,进而污染地下水与河水,较由降雨引起的地表径流流失显得更为突出. 距离河道50～200 m的范围是重要的污染净化单元,为典型的滩区地下水-河流的水陆交错带. 该区域的合理保护,对于保护河流水质和地下水水质十分重要.     

赤泥强化型河岸带模拟系统对再生水中磷去除效果的研究

为了探讨不同比例赤泥施入量对再生水磷去除效果的影响以及植物在再生水净化过程的作用,利用赤泥中富含钙、铁、铝等金属氧化物对磷具有较强吸附性能的特点,构建了室内赤泥强化型河岸带模拟系统.结果表明,赤泥最适施入质量分数为2.5%～5.0%,此时TP去除率为82%～76%,出水磷浓度约为0.22～0.29 mg/L,SRP/TP比值为74%～75%.当赤泥施入量为2.5%时,相比无植物系统,有植物系统的磷净化效率提高了4%,约为86%,出水磷浓度为0.17mg/L.这些结果表明赤泥可以适当比例直接掺混于河岸带的土壤中,这为其提高对再生水中磷的去除能力提供了一种新途径.     

LANDSCAPE‐SCALE ANALYSIS AND MANAGEMENT OF CUMULATIVE IMPACTS TO RIPARIAN ECOSYSTEMS: PAST,PRESENT, AND FUTURE1

ABSTRACT: Analyses of cumulative impacts to riparian systems is an important yet elusive goal. Previous analyses have focused on comparing the number of hectares impacted to the number of hectares restored, without addressing the loss of riparian function or the effect of the spatial distribution of impacts. This paper presents an analysis of the spatial distribution of development‐related impacts to riparian ecosystems, that were authorized under Section 404 of the Clean Water Act. Impacts on habitat structure, contiguity, and landscape context were evaluated using functional indices scaled to regional reference sites. Impact sites were mapped using GIS and analyzed for spatial associations. Positive spatial autocorrelation (i.e. clustering of impact sites) resulted from the piecemeal approach to impact assessment, which failed to prevent cumulative impacts. Numerous small projects in close proximity have resulted in adverse impacts to entire stream reaches or have fragmented the aquatic resources to a point where overall functional capacity is impaired. Additionally, the ecological functions of unaffected areas have been diminished due to their proximity to degraded areas. A proactive approach to managing cumulative impacts is currently being used in Orange County, California as part of a Corps of Engineers sponsored Special Area Management Plan (SAMP). The SAMP process is evaluating the ecological conditions and physical processes of the study watersheds and attempting to plan future development in a manner that will guard against cumulative impacts.     

水位波动和植被恢复对三峡水库消落带土壤原核微生物群落结构的交互影响

水库消落带是典型的生态脆弱敏感区.水位波动是影响消落带土壤环境的主要因素,植被恢复是消落带土壤保育的重要手段.然而,在水库消落带中,水位波动和植被恢复对土壤微生物群落结构的交互影响尚不清楚.为此,选取三峡水库消落带中不同水位高程的撂荒草地和人工林地为研究对象,利用16S rRNA高通量测序技术探究土壤原核微生物群落组成和多样性,并探讨驱动土壤原核微生物群落结构的主要环境因子.结果表明,消落带的低水位高程中土壤原核微生物α多样性最高,其中163 m高程的Pielou_e指数、Shannon指数和Simpson指数显著高于168 m高程,Chao1指数和Shannon指数显著高于173 m高程.但撂荒草地和人工林地的土壤菌群α多样性并无显著差异.同时,水位波动和植被恢复均对土壤原核微生物的群落组成产生显著影响,不同样地中生物标志物类别具有明显差异.值得注意的是,植被恢复模式差异对土壤原核微生物群落结构的影响强于水位波动.此外,层次分割结果显示土壤pH是三峡水库消落带土壤原核微生物群落结构变化的主要驱动因子.以上结果可深化对水库消落带土壤微生物群落结构的认识,并为水库消落带生态系统的恢复重建提供科学参考.     

不同河岸带修复策略对氮磷非点源污染的净化作用

选择北江的重要支流流溪河流域为研究对象,基于现有河岸带对非点源污染削减作用的模拟结果,采用情景分析法,预测不同河岸带修复策略对非点源污染的削减作用,使用效益-成本指数表征TN和TP削减率提高幅度与增加河岸带面积的关系,比较不同河岸带修复策略的效率.结果表明:河岸带对TN和TP的削减能力具有较大的空间差异性.各修复情景都在不同程度上提高了河岸带对TN和TP的削减率(TN:23.36%~30.72%;TP:27.19%~39.86%),河岸带增加总面积与削减率呈现对数增长关系(P<0.05).选择综合考虑了流域非点源负荷量以及河岸带状况的优先修复子流域进行河岸带修复时,效益-成本指数达最高为1.19%.     

Applicability of Montreal Process Criterion 4 — soil and water conservation — to rangeland sustainability

SUMMARY

Criterion 4 of the Montreal Process addresses the conservation of soil and water resources as a way to assess the sustainability of a nation's forests. For the most part, the indicators under this criterion are relevant to rangelands. The area and percent of rangeland with significant soil erosion apply equally well to both biomes. Percent of streams with flow rates and timing outside its range of historical variation is also equally important, although a measure of proper functioning and condition may provide a better measure of the indicator. The area and percent of rangeland with diminished soil productive capability because of a loss of reduced organic matter or changed physical characteristics can be useful indicators locally and regionally.