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61.
Milica Jaimovi Mirjana Lenhardt Jasmina Krpo‐etkovi Ivan Jari Zoran Ga
i Aleksandar Hegedi 《Fisheries Management and Ecology》2019,26(2):153-164
The life‐history traits and population dynamics of the black bullhead Ameiurus melas (Rafinesque) were studied monthly from August 2009 to December 2012 in Lake Sava in Belgrade (Serbia). This period included a mass mortality event in May 2011 and subsequent population recovery during 2012. Available evidence suggests the mass mortality was caused by European catfish virus that only affected the black bullhead. Changes in key life‐history traits and the recovery potential (increase in catch‐per‐unit‐effort, doubling of young‐of‐the‐year to adult ratio, earlier maturation and increased fecundity) following the mass mortality event suggest population resilience typical of a recurring boom‐bust pattern and demonstrate the species’ capacity to recover rapidly and re‐establish following disturbance. Repeated systematic mass removals of both juveniles and adults (using fyke nets) will be required if future fishery management measures aimed at limiting the population size are to be effective. 相似文献
62.
基于次降雨小流域侵蚀产沙过程的复杂性、非线性,利用支持向量机回归和主成分分析方法,确定了影响次降雨小流域侵蚀产沙量的关键因子,包括浑水径流深、洪峰最大流量、降雨量和30min最大降雨强度。建立了向量机回归支持下的次降雨小流域侵蚀产沙预测模型。利用60次侵蚀产沙实测资料,对模型预报精度进行了分析,结果表明,基于支持向量回归的次降雨流域侵蚀产沙预报模型具有较好的预测精度,预测精度平均为在86%。该研究为揭示次降雨小流域土壤侵蚀规律提供了新的途径和方法。 相似文献
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64.
根据Climate Research Unite(CRU) 1901-2013年最新0.5.×0.5.网格点的逐月潜在蒸散量和降水数据,.运用趋势分析法、Mann-Kendall非参数检验法和小波分析法,探究了塔吉克斯坦过去113 a极端降水事件的特征及其区域差异.结果表明:①过去113 a,塔吉克斯坦年、春季、秋季和冬季的极端降水事件都呈增加趋势,其增势分别为:0.33次·(10a)-1、0.15次·(10a)-1、0.07次·(10a)-1和0.20次·(10a)-1,而夏季呈轻微的减少趋势;年和四季都发生了明显突变,且存在变化周期.②东部的戈尔诺-巴达赫尚自治州年、春季、秋季和冬季的极端降水事件发生频次相对较高,哈特隆州西南部和索格特州西北地区极端降水事件发生频次相对较低;而夏季极端降水事件在戈尔诺-巴达赫尚自治州西部、索格特州的北部地区和哈特隆州的东部发生频次较高,在塔吉克斯坦最西部和东部则发生频次较低.在塔吉克斯坦的哈特隆州和中央直属区的东部,以及戈尔诺-巴达赫尚自治州的极端降水事件增势最为明显. 相似文献
65.
As the increases of climatic aridity and grazing intensity,shrubs play an increasingly important role in grassland ecosystem in arid and semi-arid regions,and its abundance also generally increases.However,the effects of climatic aridity and grazing intensity on sexual reproduction of shrubs in grassland remain largely unclear.In order to understand the effects of grazing intensity and climatic drought stress,and their interaction on seed production of shrub species,we examined the seed number,seed weight and seed yield of Caragana stenophylla under three grazing intensities(fenced,mild grazing and severe grazing) across a climatic aridity gradient(semi-arid,arid,very arid and intensively arid zones) in the Inner Mongolia Steppe,northern China during 2012–2013.The seed number,seed weight and seed yield gradually increased from the semi-arid to the very arid zones,but decreased from the very arid to the intensively arid zones in fenced plots.The seed number and seed yield decreased from the semi-arid to the intensively arid zones in mild and severe grazing treatment plots,therefore,grazing enhanced the suppression effect of climatic aridity on seed production of C.stenophylla.The seed number and seed yield gradually decreased as grazing intensity increased.The seed weight was highest in severe grazing plots,followed by the mild grazing plots and then the fenced plots.Precipitation varied interannually during the study period.We observed that the seed number,seed weight and seed yield were lower in the low precipitation year(2013) than in the high precipitation year(2012).As climatic drought stress increased,the negative effects of grazing on seed production of C.stenophylla also gradually increased.Our results indicated that climatic drought stress may contribute to the encroachment of C.stenophylla shrub in arid zones by promoting its seed production.However,grazing had negative effects on sexual reproduction of C.stenophylla,and the combined effects of drought stress and grazing seriously suppressed sexual reproduction of C.stenophylla in the intensively arid zone. 相似文献
66.
研究旨在应用衢州市1972—2015年气象观测资料、衢州市历年水稻产量、NCEP/NCAR再分析资料和东京气候中心海温资料,采用统计分析方法确定7月异常低温年出现的规律、对水稻产生的影响与前期海温的相关性,采用用天气学方法分析大气环流特征。结果表明,7月异常低温对水稻减产具有明显作用;7月异常低温年仅出现在多雨年内,与前期4—7月太平洋相关海域海温存在明显负相关,根据前期海温特征可提前1~3个月对7月异常低温进行预测,环流具有亚洲区极涡偏强,南亚高压偏弱,西太平洋副热带高压脊线偏南、西伸脊点偏东,东亚夏季风偏弱,在高度距平场上表现为新地岛至长江中下游地区“- -”分布等特征。 相似文献
67.
基于数据世系管理的精准农业不确定性复杂事件处理 总被引:1,自引:0,他引:1
伴随物联网采集数据流的增加和对复杂事件匹配的准确性、可靠性要求的提高,不确定性复杂事件处理的研究得到广泛的关注。精准农业中存在大量的RFID及传感器监测数据,但是监测硬件和无线通信技术不能保证100%的可信数据,因此需要一个能应用在精准农业中处理不确定事件的流处理引擎。本文在现有流处理引擎SASE基础上,加入概率流理论和数据世系管理理论,提出一种新型的复杂事件处理引擎PUCEP,可以计算输出复杂事件的概率,同时提高不确定性复杂事件的匹配效率,从而减少计算资源消耗和反应时间,提高整个系统的实时性。实验使用温室传感器采集数据,结果表明所提方法对处理概率事件流的复杂事件是有效的。 相似文献
68.
XU Wenxuan 《干旱区科学》2015,7(6):852-859
Great gerbil(Rhombomys opimus) colonies, with bare soil and herbaceous plants, are conspicuous to the background environment throughout their range area. In order to quantify the engineer role of great gerbils, we investigated the plant communities of 20 active colonies in the Junggar Basin, Xinjiang, China. In areas without disturbance, desert plant communities were dominated by the shrubs with low level species richness. In burrow areas and surrounding intermediate areas, which were disturbed by great gerbils, the shrubs were suppressed with the decrease of vegetation cover and aboveground biomass. As a result, "niche gaps" were created in disturbed areas and worked as a refuge for herbaceous annuals and perennials. So the existence of great gerbils increased the overall species richness of the desert. Furthermore, herbaceous annuals and perennials are the major food source for great gerbils in spring, indicating that great gerbils have a mutually beneficial relationship with herbaceous plants. 相似文献
69.
70.
对于林火预报工作中一些不能准确预测未来或尚未发生的事件,我们可以对火灾历史资料进行统计分析,找出林火发生发展规律,应用小概率事件原理,对林火发生的可能性进行预估假设检验,从而解决问题。本文将通过实例应用来说明。 相似文献