太湖流域水环境演变与人类活动耦合关系

太湖流域水环境与人类活动之间存在相互制约、相互作用的关系。从 2 0世纪 6 0年代起 ,随着经济的发展、工业化与城市化进程的加速 ,流域水环境不断恶化 ,具有表征意义的太湖水体的TP ,TN ,COD浓度不断上升。本文把环境演变的人文驱动因素归纳为人口发展、经济发展、城市化、土地利用等 ,将其与太湖流域水环境耦合 ,得出探讨性结论 :太湖流域人类活动与水环境之间的互动关系大致经历了干预、干预—弱制约、干预—制约、干预—强制约四个阶段 ,每个阶段对应着不同的人类活动特征。流域水环境恶化经历了几十年 ,而水环境修复则需要人类更长时期的共同努力     

The Brown Trout Population at Loch Fleet Eight Years After Liming

At the start of the Loch Fleet Project in 1984, the Loch and the upper 7 km of its efferent stream were found to be devoid of trout (Salmo trutta) as a result of acidification. Following the liming treatments applied to the catchment, from 1986 the formerly toxic water quality conditions (pH ∼ 4.5, calcium ∼ 1 mgl^-1, elevated aluminium and heavy metal levels) were eliminated, and trout were reintroduced on two occasions, in 1987 and 1988. A total of 520 fish were stocked, at a combined density equivalent to 5.5 kg ha^-1. Surveys of the loch and stream populations were carried out annually until 1993 to monitor their development, using a range of techniques, including electrofishing, gill-netting, seine-netting, spawner trapping and mark-release recapture methods. Length and scale- analysis were used to investigate fish growth.

The trout population in Loch Fleet expanded rapidly as a result of natural spawning in the loch's main feeder stream, augmented by the use of an artificial spawning bed which was constructed at the loch outlet in 1990. in mid-1983 the stock density, estimated by mark-recapture census methods, had increased to 24.9 kg ha^-1. Poor recruitment in the years 1991-93, however, reduced the rate of expansion and resulted in a population comprising mainly older individuals. the poor recruitment in these years was not fully explained but was not caused by water quality and was most likely a result of fry washout by spring spates.

Fish growth rates were high initially and were estimated on the basis of the Elliott trout growth model to be optimal for the prevailing water temperature regime of the loch. By 1991, growth rates had fallen, probably as a result of competition for food, but showed signs of recovery towards the end of the study period in 1993, following the period of lower population densities of young fish.

Trout rapidly repopulated the loch's outlet stream after 1987 but have remained sparse and have shown no signs of spawning within most of the stream. Water analyses have shown that the liming of the Loch Fleet catchment has minimal impact on downstream waters when flows are high, so that potentially toxic acid episodes have not been prevented.     

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…     

贺兰山露天煤矿生态修复前后植物群落差异及地境结构研究

为探究贺兰山露天煤矿生态修复后植被恢复情况,依据生态地质学的相关理论和方法,通过野外植物群落特征和植物根群结构调查,以及植被地下生境土壤肥分养分取样与测试,对背景区与恢复区植物群落结构和物种多样性差异进行了对比分析,确定了不同植物群落的地下生境范围,并进一步探究了影响植被恢复的土壤因子.结果 表明:①贺兰山自然保护区主...     

Phosphorus release： A biogeochemical insight from a restored lakeside wetland in the Yangtze-Huaihe region, China

The heavy intensification of agriculture in East China since the 1980s caused the decrease of lake area and water storage capacity with impediment of regulation, lake eutrophication and frequent floods. Many restoration projects have been conducted. However, the knowledge of biogeochemical factors that drive nutrient cycles during the early stage of restoration is still limited. We studied the effect of the remediation of a patch of near-shore shallow wetland on the northern bank of Chaohu Lake in the Yangtze-Huaihe region, China, which was used as rice paddy for many years, on the behavior of phosphorus. Redox potential (ORP), temperature and dissolved oxygen were monitored in situ from May 2006 to November 2007. Samples of soil pore water were collected during this time for the determination of different forms of iron and phosphorus. ORP showed a clear transition of the wetland soil from an oxidized state in winter to a reduced state in summer. The decrease of ORP correlated with the release of large amounts of Fe and P. The maxima of total dissolved Fe and total dissolved P in the summer of the second year were (13.8 ± 6.8) mg/L and (0.88 ± 0.27) mg/L, respectively. It is worth noticing that P concentration far exceeded the critical value of lake eutrophication (0.02 mg/L). The pressure of P release to the adjacent lake during the first two years of wetland restoration from rice fields should be taken into account by environmental policy makers.     

Plant colonization of ex-arable fields from adjacent species-rich grasslands: The importance of dispersal vs. recruitment ability

Species-rich semi-natural grasslands have declined drastically in Europe over the last century and occur in modern landscapes as small and isolated fragments. Recreation of these species-rich plant communities and increasing connectivity of remaining grasslands are important goals for nature conservation. Ex-arable fields located adjacent to species-rich grasslands have been suggested as targets for such recreation, but we still lack knowledge about the processes determining colonization from grasslands to ex-arable fields. We examined transects from species-rich semi-natural grasslands to ex-arable fields in a nature reserve located in southeast Sweden, and analysed relationships between observed colonization of ex-arable fields and two characteristics of species: dispersal ability and recruitment ability. Colonization of ex-arable fields was not related to dispersal ability, assessed as adhesive potential to animal coat, wind dispersal potential and seed mass (related to seed production), but was positively related to recruitment ability, assessed by sowing experiment. The same relationships appeared when using a performance index from sowing experiments conducted in the UK. We conclude that recruitment ability is a key factor for colonization of ex-arable fields. In our study, around 50% of semi-natural grassland species were able to colonize adjacent ex-arable field margins spontaneously within a time window of less than 50 years. Seed sowing is however needed to increase the speed of the colonization process, because increasing seed density promotes colonization of species with poor recruitment in ex-arable fields. Actions to increase area and connectivity of species-rich grasslands should consider incorporating ex-arable fields.