基于组合可拓综合分析法的鄱阳湖流域水质富营养化评价

长期跟踪定位评价湖泊的水质营养化程度,对于实现地区水功能具有重要意义。针对评价方法中指标选取的可行性、单一性、权重赋值的主观随意性以及水质变化的模糊性、随机性、动态性和生物指示性等特点,采用了可拓综合评价法和浮游生物调查与室内测定法相结合,构建了组合可拓综合分析法,一方面利用可拓综合分析法对鄱阳湖流域5个代表性观测站点的10年的年均（每2年）观测数据进行评价;另一方面通过浮游生物指示法对该5个站点的水质进行富营养化评价,以生物指示评价法所得等级与可拓综合分析法评定等级吻合的最多次数所对应等级作为组合可拓综合评价法的评价等级。结果表明：（1）自2006年以来鄱阳湖流域水体富营养化水平较为平稳,总体呈好转势态。2010年有4个观测点的水体达到富营养化程度,而在2014年湖区的蛤蟆石和鄱阳水质略有所改善,达到轻富营养化程度,都昌、康山、星子站点的水体为中营养化,改善幅度较大,水质较好;（2）从湖区的地理区位看,鄱阳湖湖区的南部和西部的水质富营养化程度总体上要好于北部、东部和中部湖区,水质富营养化程度表现为区域的不均匀性。     

基于减量精细采样法估算小麦叶片氮积累量的最佳归一化光谱指数

基于6个小麦品种、5个施氮水平、4年田间试验条件下不同生育时期的小麦叶片高光谱反射率和相应的氮含量及生物量,采用减量精细采样法,系统构建了350～2500 nm范围内所有两两波段组成的归一化光谱指数［NDSI（i, j）］,综合分析了小麦叶片氮积累量(LNA, g N·m^-2)与NDSI（i, j）的定量关系,确定了估算叶片氮积累量的新高光谱特征波段和光谱指数,进而建立了小麦叶片氮积累量监测模型.结果表明：估算小麦叶片氮积累量的敏感波段主要存在于可见光区和近红外区,最佳特征波段组合为720 nm和860 nm;基于NDSI(860,720)的叶片氮积累量监测模型为LNA=26.34×［NDSI(860,720)］^1.887（R²=0.900,SE=1.327）.利用独立试验资料的检验结果表明,基于NDSI(860,720)建立的回归模型对小麦叶片氮积累量的估测精度为0.823,RMSE为0.991 g N·m^-2,模型预测值与观察值之间的符合度较高.可利用新的归一化高光谱参数NDSI(860,720)来估算小麦叶片氮积累量.     

Morphological diversity of cultured cold-active lytic bacteriophages isolated from the Napahai plateau wetland in China

<正>Dear Editor,Viruses are the most abundant,diverse,and ubiquitous entities(approximately 1031)on Earth.They play major roles in horizontal gene transfer,the regulation of bacterial community structures,as well as nutrient and energy cycles of marine ecosystems(Danovaro et al.,2008).In particular,lytic bacteriophages(phages)can infect and kill bacteria without harming human or animal     

春季和夏季巢湖浮游生物群落组成及其动态分析

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洱海蓝藻水华暴发期浮游植物群落变化及影响因素

对洱海水质和浮游植物进行了调查, 分析了洱海藻类水华暴发季节水质营养水平及浮游植物多样性, 并探讨了洱海浮游植物种群演替的环境机制. 研究结果表明, 洱海蓝藻水华在6-10月份大量暴发, 蓝藻数量高达107 cells/L, 水华种类为微囊藻(Microcystis)属的一些种, 微囊藻在6-10月份占绝对优势, 最高可达90%以上. 分析5-11月洱海营养水平, 其中7月营养水平最高, 浮游植物生物量10月份最大(以叶绿素a表示). 使用SPSS里的pearson分析了浮游植物和各理化因子的关系, 结果表明相对于其他浮游植物种类, 总磷(TP)对微囊藻的影响比较大.       

新疆艾比湖湿地自然保护区胡杨根系水分再分配的估算

根据对新疆艾比湖湿地自然保护区荒漠河岸林的主要建群种胡杨(Populus euphratica)的根系分布特征, 林冠下土壤的饱和容积含水量、最大导水率和根系最大导水率的试验观测数据, 以及对其林冠下5层不同深度土壤容积含水量、土壤水势的动态监测数据, 构建了胡杨根系水分再分配量估算的Ryel模型, 并对胡杨不同季节的水分再分配过程进行了短期模拟。结果表明: (1)胡杨根系水分再分配过程的水分再分配量的最大值出现在艾比湖地方时间凌晨2:30。(2)随着生长季节的变化, 胡杨根系水分再分配的作用逐渐减弱, 并表现出向土壤下层迁移的现象。6月份, 水分再分配过程主要发生在0-40 cm土层, 最大分配量为0.022 0 cm, 夜间总分配量为0.111 0 cm; 8月份水分再分配过程主要发生在10-70 cm土层, 最大分配量为0.006 5 cm, 夜间总分配量为0.018 4 cm; 10月份水分再分配过程主要发生在70-100 cm土层, 最大分配量为0.003 9 cm, 夜间总分配量为0.008 6 cm。     

Fish abundance and trophic structure from the commercial catch in Lake Patzcuaro, Mexico

The composition, abundance and trophic structure of the fish community in Lake Patzcuaro is analyzed, using data from eight samples taken from the commercial fishery acquired between August 1990 and April 1991. A total of 65 767 individuals, caught with gillnets selective to all fish and size, were analyzed. Eleven species (8 native and 3 exotic) were recorded during the study. Zooplanktivorous were the most representative species, amounting to 91% of the total number. Also, they were the most characteristic species (36.4%) when feeding habits were considered, followed by carnivore and omnivore (27.3% each), and herbivore (9.1%). Three species groups and three time-associated groups were detected by means of classification methods. Lake Patzcuaro's ichthyofauna is to be considered as a transitional community that has not reached equilibrium, particularly after the introduction of exotic species and local extinction of native species. However, Lake Patzcuaro has the greatest fishery production of all tropical lakes in the Central Plain of Mexico and it is mainly sustained by native species. The differential use of feeding resources by the fish species and the diversity in their habits must be taken into account to design strategies to maintain the fish structure (avoiding new introduction of exotic species) and the fish production in Lake Patzcuaro.     

Stocking piscivores to improve fishing and water clarity: a synthesis of the Lake Mendota biomanipulation project

SUMMARYY 1. A total of 2.7 × 10⁶ walleye fingerlings and 1.7 × 10⁵ northern pike fingerlings were stocked during 1987–99 in eutrophic Lake Mendota. The objectives of the biomanipulation were to improve sport fishing and to increase piscivory to levels that would reduce planktivore biomass, increase Daphnia grazing and ultimately reduce algal densities in the lake. The combined biomass of the two piscivore species in the lake increased rapidly from < 1 kg ha^?1 and stabilised at 4–6 kg ha^?1 throughout the evaluation period. 2. Restrictive harvest regulations (i.e. increase in minimum size limit and reduction in bag limit) were implemented in 1988 to protect the stocked piscivores. Further restrictions were added in 1991 and 1996 for walleye and northern pike, respectively. These restrictions were essential because fishing pressure on both species (especially walleye) increased dramatically during biomanipulation. 3. Commencing in 1987 with a massive natural die‐off of cisco and declining yellow perch populations, total planktivore biomass dropped from about 300–600 kg ha^?1 prior to the die‐off and the fish stocking, to about 20–40 kg ha^?1 in subsequent years. These low planktivore biomasses lasted until a resurgence in the perch population in 1999. 4. During the period prior to biomanipulation when cisco were very abundant, the dominant Daphnia species was the smaller‐bodied D. galeata mendotae, which usually reached a biomass maximum in June and then crashed shortly thereafter. Beginning in 1988, the larger‐bodied D. pulicaria dominated, with relatively high biomasses occurring earlier in the spring and lasting well past mid‐summer of many years. 5. In many years dominated by D. pulicaria, Secchi disc readings were greater during the spring and summer months when compared with years dominated by D. galeata mendotae. During the biomanipulation evaluation period, phosphorus (P) levels also changed dramatically thus complicating our analysis. Earlier research on Lake Mendota had shown that Daphnia grazing increased summer Secchi disc readings, but P concentrations linked to agricultural and urban runoff and to climate‐controlled internal mixing processes were also important factors affecting summer readings. 6. The Lake Mendota biomanipulation project has been a success given that high densities of the large‐bodied D. pulicaria have continued to dominate for over a decade, and the diversity of fishing opportunities have improved for walleye, northern pike and, more recently, yellow perch. 7. Massive stocking coupled with very restrictive fishing regulations produced moderate increases in piscivore densities. Larger increases could be realised by more drastic restrictions on sport fishing, but these regulations would be very controversial to anglers. 8. If the lake's food web remains in a favourable biomanipulation state (i.e. high herbivory), further improvements in water clarity are possible with future reductions in P loadings from a recently initiated non‐point pollution abatement programme in the lake's drainage basin.     

环青海湖地区草地生境的蝗虫潜在发生可能性评价

环青海湖地区是青海省草地蝗虫最集中的区域,主要有10种,它们对草地造成了很大危害,草地蝗虫的发生与由植被、地形、土壤等组成的生境类型存在密切的关系。论述了草地蝗虫生境类型划分的原因,并提出了生境分类方案,在此基础上,提出了各类生境针对草地蝗虫潜在发生可能性的评价原理,方法和评价指标体系,并据其对野外实地调查样点进行了评价,结果表明,草地蝗虫潜在发生可能性指数与草地蝗虫密度间的相关系数高达0．90,研究区受草地蝗虫严重危害或较严重危害的生境类型是芨芨草草原,克氏针茅草原及紫花针草原,高寒草甸属一般危害,高寒灌丛草甸则不发生危害。     

洞庭湖渔业资源现状及其变化

1990－1999年资源监测表明,洞庭湖鱼的种类与70年代基本相同,但其组成结构发生较大变化,明显以鲤,鲫,鲶,黄颡鱼等湖泊定居性鱼类为主,最高达86．1％,“四大家鱼”在渔获物中所占比较不足10％,刀鲚等洄游性鱼类已极为罕见;90年代渔获量平均为3．97万t,渔业产量增加,但多以1－2龄鱼为主,补充群体严重不足,水利工程的兴建,泥沙淤积,围垦,污染加剧以及过度捕捞是造成洞庭湖渔业资源衰退的主要原因。