Stream water quality and its influencing factor in lower order streams in upriver sections of Ashihe River     

GUO Bao-qin WANG Qing-cheng YU Hong-li Paul E Mou 《林业研究》2005,16(3):181-186

For understanding the reasons that caused the degradation of water quality in lower order streams, systematic sampling was conducted at different spatial locations aiong the low order streams （1 st-5th） of Ashihe River continuum in Maoershan Experimental Forest of Northeast Forestry University, Sharlgzhi City, Heilongjiang Province, China. The indexes of stream water quality, i.e., the pH, dissolved oxygen（DO）, turbidity, temperature, PO43-P, NO3-N and NH4^＋-N concentrations, total dissolved inorganic nitrogen （TDIN-N, including concentrations of NO3^＋-N and NH4^＋-N）, and total phosphorus （inorganic and organic phosphorous, TP） were measured and analyzed. The stream order, related environmental settings and land-use type were recorded for each sampling location. The indexes of stream water quality at different locations with different stream orders and land use types were compared by ANOVA analysis. The indexes of stream water quality at different sampling locations were analyzed by Hierarchical cluster analysis. Result showed that water quality had significant difference in different stream orders and land use types; some locations with different stream features （stream order and land use type） were grouped into same clusters, indicating that random disturbances produced the variations in water quality, which made the spatial variances of stream water quality inconsistent with the general rules.  相似文献   

Seasonal and land use impacts on the nitrate budget and export of a mesoscale catchment in Southern Portugal     

Mariela A. Yevenes  Chris M. Mannaerts 《Agricultural Water Management》2011,102(1):54

Stream nitrate nitrogen exports are an important indicator of agricultural impacts on aquatic health in catchments. Quantitative assessment of factors and processes affecting stream nitrate loadings is complex because of the large number of causal factors and processes, such as weather and rainfall, catchment hydrological behavior, soils, land use practices and biogeochemical processes. An eco-hydrological catchment modeling approach, using the SWAT model driven by detailed field data, was used to analyze the nitrate export and the components of the nitrogen budget of the 352 km² upper Roxo river catchment in Southern Portugal. A detailed eight-year record (2001–2008) of the monitoring of weather, reservoir inflow, stream biogeochemistry, soils, in-stream and groundwater quality, and fertilizer application was used to calibrate and validate the streamflow and nitrate loadings obtained by the model. Results indicated a strong seasonal variation in nitrate exports, closely related to temperature and rainfall. Monthly nitrate loadings varied from 0.02 to 2.48 kg N ha⁻¹ during summer and between 0.03 and 14 kg N ha⁻¹ during late autumn and winter. Stream nitrate values, ranging from 1.5 to 16.5 mg N L⁻¹, were strongly related to extreme rainfall occurrences and wet periods. Detailed analysis of nitrate budget components at the sub-catchment level enabled evaluation of the impacts of the various processes affecting the nitrate nitrogen pool of the catchment. Besides high fertilizer inputs for annual crops, it was shown that biological nitrogen fixation and wet deposition by rainfall should be accounted for in input balances. Where denitrification naturally reduces nitrate levels in soils, streams and the reservoir, the largest contribution to stream nitrate originates from leached soil nitrate reappearing in groundwater baseflow, compared with less than 2% from direct surface runoff during high rainfall events. A fertilizer reduction scenario was effectively implemented to evaluate remedial nitrate control policies in accordance with the European Nitrate and Water Framework Directives. Agricultural practices and seasonal weather fluctuations were the main reasons for temporal variations in nitrate export via small streams to the main reservoir.  相似文献   

广西北部湾经济区农业非均衡发展比较研究     

张经阳 《安徽农业科学》2017,45(12)

在广西自治区北部湾经济区基本情况的基础上,对农业经济、农业生产、农民生活等农业发展总体情况进行了分析;利用广西自治区、南宁市、防城港市、钦州市、北海市面板数据,借鉴国内学者的研究成果和经济非均衡增长理论,从该区域第一产业人均增加值、粮经比、农产品产出、人均农产品占有量4个方面对该区域存在的非均衡发展现象进行比较分析。基于经济、产业、条件等基础层面分析非均衡发展现象的成因,并提出了强化北部湾农业产业分工与协同、强化北部湾农村改革试验的集成研究、强化北部湾农业产业升级与转型发展的对策建议。  相似文献   

广西北部湾方格星虫氨基酸组成与营养价值评价     

刘永强  黄岛平  陈建红  林葵  黄艳  陈秋虹  李扬华 《安徽农业科学》2012,(27):13401-13402,13521

[目的]测定广西北部湾方格星虫的氨基酸,进行营养价值分析评价,为进一步开发利用提供理论依据。[方法]用全自动氨基酸分析仪测定广西北部湾方格星虫的氨基酸含量,利用荧光法测定色氨酸含量,并根据FAO/WHO的氨基酸评分标准模式进行氨基酸营养价值评价。[结果]共测定18种氨基酸,总量为(73.93±2.80)%;鲜味氨基酸为(30.60±1.05)%,占氨基酸总量的41.39%;必需氨基酸为(26.22±1.01)%,占氨基酸总量的35.47%;非必需氨基酸含量为(39.12±1.43)%,必需氨基酸与非必需氨基酸的比例为67.05%,符合FAO/WHO标准。[结论]广西北部湾方格星虫营养价值较高、品质优良,具有较高保健价值和药用价值,值得进一步开发。  相似文献   

Subsystems,flowpaths, and the spatial variability of nitrogen in a fluvial ecosystem     

David Bruce Lewis  Nancy B. Grimm  Tamara K. Harms  John D. Schade 《Landscape Ecology》2007,22(6):911-924

Nutrient dynamics in rivers affect biogeochemical fluxes from land to oceans and the atmosphere. Fluvial ecosystems are thus important environments for understanding spatial variability in nutrient concentrations. At the San Pedro River in semi-arid Arizona, USA, we investigated how variability in dissolved inorganic nitrogen (DIN) was regulated by subsystem type and hydrological flowpaths. The three subsystems we compared were the riparian zone, parafluvial (gravel bar) zone, and surface stream. DIN concentration was greater in the riparian zone than in the surface stream, suggesting that the riparian zone retains DIN and is a source of N for the surface stream. Parafluvial zones were too variable to generalize how they regulate DIN. Our hypothesis that subsystem type regulates DIN oxidation was too simple. The riparian and parafluvial zones host a mosaic of oxidizing and reducing conditions, as they exhibited highly variable ammonium to nitrate (NH₄⁺:NO₃⁻) ratios. Surface stream DIN was dominated by NO₃⁻. Along a subsurface flowpath in the riparian zone, we did not observe spatial covariation among the N forms and transformations involved in mineralization. We also compared spatial variability in solute concentrations between flowpaths and non-flowpath reference areas. Our mixed results suggest that spatial variability is regulated in part by flowpaths, but also by solute-specific processing length along a flowpath. To understand the distribution of N in fluvial ecosystems, subsystem type and flowpaths are readily discernable guides, but they should be coupled with other mechanistic factors such as biota and soil type.  相似文献   

Eutrophication and Recreational Fishing on the Finnish Coast of the Gulf of Finland: A Mail Survey     

A. Lappalainen  J. Pönni 《Fisheries Management and Ecology》2000,7(4):323-335

The Gulf of Finland is one of the most eutrophic areas in the Baltic Sea and is also the main fishing area for more than 150 000 recreational fishermen in Finland. The findings of a mail survey showed that the most important species for the recreational fishery is perch, Perca fluviatilis L. There is no clear evidence that eutrophication has had a harmful effect on the stocks of perch and other species considered important. Heavy fouling of gear, particularly gill nets, is the most acute problem caused by eutrophication to the local recreational fishery. The rapid fouling of passive gear was experienced by 67–86% of all fishermen in the three study areas. A general deterioration in water quality was perceived because only 2–14% of fishermen rated the water quality as excellent. However, a minority of recreational fishermen seem to have adapted or grown accustomed to the deterioration in water quality. Even in the two most eutrophic study areas, 23–31% of recreational fishermen considered that an improvement in local water quality would not benefit their own fishing in any way.  相似文献   

Trends in coho marine survival in relation to the regime concept   总被引：2，自引：0，他引：2  

Beamish  Noakes  Mcfarlane  Pinnix  Sweeting  & King 《Fisheries Oceanography》2000,9(1):114-119

There was a synchronous and significant decrease in marine survival of coho salmon in the Strait of Georgia, Puget Sound, and off the coast from California to Washington after 1989. This large-scale, synchronous change indicates that trends in coho marine survivals were linked over the southern area of their distribution in the north-east Pacific, and that these linkages were associated with a common event. Indicators of large-scale climate change (the Aleutian Low Pressure Index) and of recent regional climate change (the April flows from the Fraser River) also changed abruptly about the same time. The synchrony of trends in marine survival of aggregates of coho stocks from three distinct marine areas and trends in climate indices implies that climate/ocean changes can have profound impacts on the population dynamics of coho salmon. The trend towards low marine survival may persist as long as the trends in the climate indicators do not change.  相似文献   

基于Goldstein模型的农村人力资源培训需求研究——以广西北部湾为例     

胡建平 《安徽农业科学》2011,39(1):554-555,559

采用Goldstein模型,从组织、任务、人员3个方面对广西北部湾农村人力资源培训需求进行研究,结果表明,培训内容应包括激发参加培训的积极性、提高文化素质、提高科技素质、培养经营能力。  相似文献   

城中村公共空间景观规划设计策略探讨     

刘国维  韦晓娟 《绿色科技》2015,(3):82-84

指出了城中村问题的解决依赖于新型城镇化城乡一体化的发展趋势,其公共空间的景观发展方向也根源于此。分析了新型城镇化对城乡景观一体化的要求,探讨了典型城乡结合部———城中村的规划设计原则与策略,为桂林灵剑溪流域城中村的景观规划设计提供理论参考。  相似文献   

基于SPOT-VEGETATION的北部湾经济区植被变化特征     

田义超  梁铭忠 《农业现代化研究》2014,35(4):465-471

以2000-2011年423景SPOT-VEGETATION逐旬NDVI数据为基础,采用MVC、标准差、线性趋势分析和HURST指数等数理统计方法对北部湾经济区植被覆被时空变化特征及未来趋势进行定量分析。结果表明,2000-2011年北部湾经济区NDVI值呈波动上升趋势,快于广西区年NDVI平均增长速率。NDVI均值存在着明显的分段特征,且转折点出现在2006年,2006年以前研究区植被覆盖呈现下降趋势,2006年以后呈现显著增加趋势。NDVI均值在空间上呈现出西北和西南植被覆被低、东南植被覆被高的态势,NDVI均值纬向分布呈现出北高南低,经向分布线性倾向率比较小,仅为0.5952/1N°。NDVI标准差的变幅较大,表现为波动小主要分布在NDVI均值的两个极端,波动较小与波动较大并存,波动较大分布比较零散的空间格局。NDVI的Hurst指数反持续(10.03%)持续性序列(89.97%),说明经济区植被的变化趋势处于持续性改善的趋势。  相似文献