Heathland Seedbanks under BrackenPteridium aquilinum(L.) Kuhn and their Importance for Re-vegetation after Bracken Control

In Great Britain, the regeneration of heathland and moorland plant communities after bracken control is slow and variable. Successful restoration depends on the availability of seed and the provision of suitable regeneration niches, as well as on the expansion of the plants previously present underneath the bracken canopy. This study investigates the availability of the seed resource of heathland species and its distribution, both in relation to increasing time since bracken invasion and with respect to its presence in litter or mineral soil.Calluna vulgariswas found to be the predominant species that germinated from the soil and litter beneath bracken at the sites studied. It appeared in greatest numbers from samples taken outside and at the edge of the bracken patch; numbers decreased deeper into the patch. Land which has been under bracken for a considerable period (>50 years) is likely to have a very reduced seedbank so that some form of propagule introduction, as well as litter disturbance, may be needed to speed up regeneration. On sites which have been invaded by bracken more recently, it is likely that litter incorporation into the soil would conserve the seed resource, whereas burning or litter removal would remove a significant proportion of that seed resource.     

COVERING BOTTOM SEDIMENTS AS A LAKE RESTORATION TECHNIQUE1

ABSTRACT: Sediment covering to control macrophytes and sediment nutrient release is reviewed. It is concluded that fly ash application to control sediment phosphorus release presents more dangers to the lake than benefits and should not be used. Polyethylene sheeting has not had long term effectiveness due to macrophyte regrowth on its surface. PVC-coated fiberglass screen is expensive but nontoxic and appears to give long term macrophyte control. Similar results may be obtained with spun-bonded polypropylene. Sand, clay, and sheeting to retard nutrient release have received insufficient attention.     

Stakeholder Willingness to Pay for Watershed Restoration in Rural Bolivia1

Abstract: Two CVM surveys were administered to 211 urban households and 188 rural farmer‐irrigators in the Comarapa watershed in Bolivia, South America, to estimate stakeholder willingness to pay (WTP) for a proposed upper watershed restoration program. Mean monthly household WTP to improve drinking water was $1.95 (65% of current charges), while mean annual WTP among farmer‐irrigators to improve irrigation water was $17 per hectare (34% of current costs). Aggregated to the entire population of households and farmer‐irrigators total WTP is $77,400 per year, which is 77% of the minimum cost to implement a watershed restoration program.     

Lateral Hyporheic Zone Chemistry in an Artificially Constructed Gravel Bar and a Re‐Meandered Stream Channel,Southern Ontario,Canada1

Abstract: The effect of stream restoration on hyporheic functions has been neglected, although channel rehabilitation projects have a potential to alter stream‐ground‐water interactions. The present study examined the effect of an artificially constructed gravel bar and re‐meandered stream channel on lateral hyporheic exchange flow and chemistry in two lowland N‐rich streams in southern Ontario, Canada. Nitrate concentrations were relatively high, ranging from 0.5 to 1.3 mg N/l in both streams during spring through fall months. However, nitrate concentrations showed a steep decline as stream water entered the gravel bar and the meander bends. Differences between observed and predicted nitrate concentrations based on conservative ion concentration patterns indicated that 40‐100 and 68‐98% of the nitrate entering the hyporheic zone was removed in the gravel bar and meanders, respectively. Rapid depletion of dissolved oxygen concentrations along lateral hyporheic flow paths and denitrifying potentials assayed by the acetylene block technique in hyporheic sediments suggests that denitrification was an important mechanism of nitrate depletion. Despite the high rate of nitrate removal, the flux of stream water laterally entering the constructed gravel bar and meander bends was very small, and hyporheic nitrate removal was <0.015% of the daily stream load during base‐flow periods in summer and fall. The effects of restoration projects on hyporheic zone dynamics are often limited in lowland streams by low channel gradients and fine floodplain sediments with low interstitial flows that restrict the magnitude of the stream‐hyporheic connection.     

Sustainability: Key to West China Development

The initiative of" West China Development(WCD) " ,launched by the Central Government,is ofgreat importance:to realizing the enormous resource and market potentials of the region,topromoting balanced development of the national economy,to improving the living standards ofpeople in the western areas,to achieving the goal of" common richness" set up by former stateleader H.E.Mr.DENG Xiaoping,as well as to consolidating solidarity of the nation,socialsecurity and border safety in the west.It…     

生态恢复背景下喀斯特地区植被覆盖的时空变化——以黔中地区为例

为了揭示退耕还林(草)、封山育林和石漠化综合治理等生态恢复工程驱动下喀斯特地区的植被覆盖度的时空变化情况,以黔中为研究区,利用2000年、2005年和2010年三期的MODIS影像数据,通过NDVI像元二分模型法,对研究区植被覆盖进行了动态变化评估。结果表明:2000年到2010年,极高植被覆盖度面积持续增长,高植被覆盖度面积持续减少,极低植被覆盖度、低植被覆盖度和中等植被覆盖度面积先增后减,植被覆盖总体呈现转好趋势;此外,植被覆盖景观斑块数减小,平均斑块面积增大,香农多样性指数减小,表明这一时期内植被覆盖景观的破碎化程度逐渐降低,生态恢复工程取得良好实效。     

典型出境河流生态修复区沉积物重金属污染特征及生态风险评估

为综合评价河流沉积物中重金属对周围环境的生态风险及为治理重金属污染河流提供参考依据,以云南省文山州内跨境河流小白河生态修复区为研究对象,分析不同形态重金属在生态修复区沉积物中的空间分布规律,并采用潜在生态风险指数法和风险评估指数法(RAC),评价沉积物中重金属污染状况和生态风险.结果表明:① 生态修复区内沉积物中五种重金属空间分布规律存在差异,w(As)、w(Co)、w(Cu)、w(Pb)、w(Zn)的平均值分别为937.64、16.72、156.23、73.47、1 117.47 mg/kg,并且w(As)、w(Cu)和w(Zn)沿水流方向逐渐降低,到生态修复区出口又呈明显增加的分布规律,而w(Pb)和w(Co)呈逐渐增加的分布规律. ② 生态修复区中重金属主要赋存形态以残余态为主,稳定性大小依次为As>Pb>Cu>Co>Zn. ③ 根据风险评估指数法,表层沉积物中重金属对环境构成的风险依次为Zn>Co>Pb>Cu>As;根据潜在生态风险指数,As是主要的生态风险贡献因子,贡献率大于80%,具有较高的生态风险,其余重金属具有较低的生态风险.因此,在环境治理时既要考虑富集程度较严重的重金属元素,也不可忽视有效态含量较高的重金属元素给环境带来的生态风险.      

立体式生态浮床在喀斯特环境水体净化中的效果研究

为了研究植物生态浮床在喀斯特水体环境中富营养物质的去除效果及生态浮床中植物的选取组合,将富贵竹和鸢尾通过单一、组合形式构建生态浮床,模拟喀斯特环境水体进行生态修复实验。结果表明,富贵竹、鸢尾、富贵竹+鸢尾不同的植物组合生态浮床对COD、TN、NH~+_4-N、NO~-_3-N、TP都有较好的去除效果,去除率依次为61.63%、44.38%、94.01%、13.35%、76.48%;28.33%、51.18%、88.11%、26.29%、55.25%;33.97%、49.56%、89.73%、22.25%、49.81%。鸢尾对TN、NO~-_3-N的去除率最好,富贵竹对NH~+_4-N、TP的去除中效果最佳,富贵竹+鸢尾组合处于中间状态,可见植物组合会使去除效果产生协同效应。通过实验组植物的生长状况和去除能力分析,单一植物组比混合组去除能力更强,但考虑综合去除效果还需要应用组合型生态浮床。     

镜泊湖富营养化评价及防治对策研究

镜泊湖富营养化的主要原因为营养物质的过量输入,其次是温度、光照、水动力条件等物理因素,第三为生态失衡.通过对其水质系统分析与评价,得出镜泊湖水质初期的处理措施合理,并逐年变好趋于稳定,水体处于中营养状态.为进一步改善镜泊湖水质,共提出三大措施,一为建立污水处理厂,二为充分利用水生植物、生态浮床措施,三为辅助人工湿地、生物操纵等生态修复方式,减少二次污染,使镜泊湖水体恢复到原来的状态.     

农业面源污染防治措施进展研究

随着城市生活污水和工业废水等点源污染 得到控制,农业面源污染的危害日益凸显.将对目前的农业面源污染防治技术以及未来的发展进行阐述,将从源头减量、传输过程的阻断与拦截、养分的回收利用以及水体的生态修复面源污染物传输四个环节分别论述.源头控制主要采用减少化肥的施用量和水土流失等实现,传输过程的阻断与拦截以及养分的回收利用主要通过将径流引入人工或自然湿地等实现,水体的生态修复主要通过生态浮床技术等暂时强化技术与植物修复技术等长效修复技术相结合的方式实现.