Scale-dependent habitat use in three species of prairie wetland birds

We evaluated the influence of scale on habitat use for three wetland-obligate bird species with divergent life history characteristics and possible scale-dependent criteria for nesting and foraging in South Dakota, USA. A stratified, two-stage cluster sample was used to randomly select survey wetlands within strata defined by region, wetland density, and wetland surface area. We used 18-m (0.1 ha) fixed radius circular-plots to survey birds in 412 semipermanent wetlands during the summers of 1995 and 1996. Variation in habitat use by pied-billed grebes (Podilymbus podiceps) and yellow-headed blackbirds (Xanthocephalus xanthocephalus), two sedentary species that rarely exploit resources outside the vicinity of nest wetlands, was explained solely by within-patch variation. Yellow-headed blackbirds were a cosmopolitan species that commonly nested in small wetlands, whereas pied-billed grebes were an area-sensitive species that used larger wetlands regardless of landscape pattern. Area requirements for black terns (Chlidonias niger), a vagile species that typically forages up to 4 km away from the nest wetland, fluctuated in response to landscape structure. Black tern area requirements were small (6.5 ha) in heterogeneous landscapes compared to those in homogeneous landscapes (15.4–32.6 ha). Low wetland density landscapes composed of small wetlands, where few nesting wetlands occurred and potential food sources were spread over large distances, were not widely used by black terns. Landscape-level measurements related to black tern occurrence extended past relationships between wetlands into the surrounding matrix. Black terns were more likely to occur in landscapes where grasslands had not been tilled for agricultural production. Our findings represent empirical evidence that characteristics of entire landscapes, rather than individual patches, must be quantified to assess habitat suitability for wide-ranging species that use resources over large areas.     

关于农田尺度下土壤有机质的空间变异研究

本文将空间分析技术与地统计学方法相结合,以某流域的土壤白土及乌栅土的各三层 土壤样本开展了数据处理及系统化分析,深入探讨了土壤有机质含量所存在的空间变异特征, 望能为此领域研究有所帮助。     

近43年黄河上游来水来沙变化特点

选取黄河头道拐站实测水沙序列(1960-2002年)资料,对水沙序列进行了多时间尺度和趋势识别的小波分析。结果表明:①黄河上游来水来沙量汛期所占比例减少,而非汛期所占比例增加;在年际变化上,水沙量逐年减少;同时,水沙相关关系具有一定的变化;②黄河上游水沙序列具有相同的多时间尺度(准周期)变化,但同一尺度下,水沙所处的丰枯变化并不一致;③年水沙序列趋势变化基本一致,20世纪80年代以来,两者存在明显减少趋势;但在非汛期,两者的趋势变化有较大区别。     

不同防治对策对柑桔糠片蚧种群的影响

1984—1987年在湖南桔园进行了综防对策、化防对策和自控(不采取任何人为的防治措施)等处理对柑桔主要害虫——糠片蚧种群影响的比较研究。综防区采用综合措施,刷洗主干,释放部分天敌,剪去蚧虫为害严重的枝条,冬季和夏季分别施用一次松脂合剂和矿油乳剂;化防区按常规每年喷药5—6次;结果表明:综防区全年虫口密度与化防区相近,两者均显著低于自控区;综防区糠片蚧蚜小蜂等寄生性天敌未受到明显的损害,捕食性蓟马、钝绥螨等捕食性天敌明显多于自控区;其它非生物致死因子对幼蚧的作用大于化防区,果实出口率自1986年起亦较化防区显著上升。自控区糠片蚧未得到控制,果实出口率较化防区降低13.3%—29.8%。化防区各种天敌的作用均显著下降,农药残留亦高。除自控区和化防区柑桔全爪螨为害较重外,其它害虫在各区的为害均处于较低的水平。文章还评价了在三种处理区致死因子对糠片蚧种群趋势指数的作用。     

Testing the spatial significance of weed patterns in arable land using Mead's test

There is a need in weed science for statistical tests for patchiness and spatial pattern. The objective of this study was to investigate the performance of Mead’s test for detecting patterns in synthetic data and in real weed counts made in maize, and making a first assessment of its applicability in ecological studies on weeds. In an extension to Mead’s test, made here for the first time, we merge original quadrat count data into rectangular cells of m by n quadrats. Care was taken to rule out the effect of starting point on the test result. Using the synthetic data, we demonstrate the ability of the test to detect both patchiness and homogeneity as deviations from randomness. The first deviation results in right‐sided significance, and the second in left‐sided significance of the test. Analysis of the real weed patterns demonstrated patchiness at many scales for five of the six investigated species and lack of any deviation from randomness in the sixth: Taraxacum officinale. The latter was the only wind dispersing species in the dataset. No deviation towards homogeneity was found in any of the real weed species at any scale. All patchy patterns showed anisotropy, being elongated in the direction of field traffic. As it turns out, Mead’s test is well suited to detect departures from randomness in observed weed patterns and enhances the suite of diagnostic tools that can be employed by weed ecologists.     

乡村生态学研究的尺度与等级特征

乡村生态学 ( Village ecology)的尺度和等级特征依赖一定空间区域 ,不同尺度所研究村落的特征也不尽相同 ,空间尺度的大小很大程度上决定于所研究村落的复杂性、稳定性及特征。在特定的空间尺度下 ,乡村的组成要素随着时间尺度的变化而变化 ,但变化速率受空间尺度大小的制约。乡村生态学研究具有等级结构 ,空间尺度决定所研究单元的等级位置。行政村 (中心村 )和自然村 (自然屯 )是乡村生态学研究的基本尺度     

宁夏固原市草畜产业发展运行机制探讨

草畜业生产方式的转变,是一项系统工程,具有复杂性和前瞻性,涉及到农、林等相关行业,与环境保护、城镇建设密切相关。本文根据当地草畜业生产实际,提出了固原市草畜业生产发展机制方面的一些创新思路。     

雌雄蛹自动分选机的研制

雌雄蚕蛹分选是制造优质蚕种的重要环节。依据雌雄蛹体重量和体形大小存在明显差异的特点 ,研制成功三段式雌雄分选机。经生产测试 ,每小时可分选 135 96kg茧的蚕蛹 ,分选雌雄蛹的误鉴率平均为 3 18% ,比人工分选的准确率高 ;通过调节分选孔的大小 ,准确率可达 99 5 %以上 ;在复眼着黑后分选对蛹体无损伤。机械操作简易 ,符合生产要求     

规模养蚕新技术的研究Ⅰ.大棚养蚕温湿度对蚕茧产质量的影响

试验调查了大棚养蚕春、夏大蚕期与蔟中的温湿度变化,以探索有利于大棚养蚕的饲养技术与小气候调节技术.棚内温湿度变化对蚕茧产质量的影响比较分析表明,春期5龄后期和上蔟初期,35～38.8℃的高温对蚕茧产质量有较大影响;夏蚕期棚内温度明显高于春蚕期,最高超过40℃,连续高温持续时间长,昼夜温差大.根据春、夏期不同的气候特点,春期大棚上蔟初期要重点进行降温排湿,夏期重点进行降温.     

家蚕雌蛾交配时间早迟与产卵的关系调查

为了解家蚕雌蛾交配时间早迟与产卵的关系,对家蚕雌蛾羽化后1～5h交配对产卵速度、产卵量和卵质的影响进行了研究,结果表明:雌蛾羽化后4～5h交配的雌蛾产卵速度快、产卵量最多、不良卵最少。