Integrating effects of hunting policy, catastrophic events, and inbreeding depression, in PVA simulation: the Scandinavian wolf population as an example     

Torbjörn Nilsson 《Biological conservation》2004,115(2):227-239

Focusing on the wolf Canis lupus in Scandinavia as an example, criteria are proposed and an analysis performed to assess the effect on extinction risk of various control policies, while accounting simultaneously for effects of inbreeding depression and potential catastrophic events. Each control policy is characterized by a hunting pressure (the increase caused by hunting of annual mortality rates) combined with a hunting threshold (the population size below which hunting is not permitted). Catastrophes are taken into account by including the persistence of a severe catastrophe in the criterion for population viability. Based on these criteria, the results suggest that only a very limited amount of hunting should be permitted at low population sizes. The results also illustrate the importance of including a long-term perspective in modelling threatened populations.  相似文献   

Surface ozone concentrations and exposures during growing season at the Lithuanian rural site     

R. Girgzdiene 《Water, air, and soil pollution》1995,85(3):1509-1514

The surface ozone (O₃) data show an increase by 2.6 % per year during the period 1982–1994 at the rural site of Lithuania. WHO (World Health Organization), UN-ECE (United Nations Economic Commission for Europe), CES (Commission of the European Communities) guideline values for the protection of vegetation from adverse effects are exceeded during the growing season at the Preila coastal station. Ozone exposures for different concentration threshold are estimated during daylight hours in April-September. These values above 60 g/m³ varied between 10 000 and 43 000 (g/m³) ·h, above 80 g/m³ — between 1700 and 15 000 (g/m³) ·h, above 100 g/m³ — between 130 and 3700 (g/m³) ·h during separate years. Maximum hourly ozone values were observed from 116 to 228 g/m³ during this period.  相似文献   

二化螟发育历期和积温效应研究     

汪信庚  程家安  何俊华 《浙江大学学报(农业与生命科学版)》1993,(4)

在15,17,21,25,29,33,35℃七种恒温下测定了二化螟各虫期的发育历期,并据此推算其发育起点和有效积温。结果为:卵11.8℃和83.5日·度;1龄幼虫11.6℃和71.7日·度;2龄幼虫10.9℃和92.4日·度,3龄幼虫11.6℃和74.1日·度;4龄幼虫11.3℃和77.2日·度;5龄幼虫10.7℃和86.6日·度,6龄幼虫10.5℃和79.5日·度;全幼虫期9.8℃和567.6日·度;预蛹12.8℃和50.7日·度;蛹10.9℃和118.9日·度;成虫产卵前期14.6℃和30.1日·度;全世代(雌)10.7℃和811.5日·度;利用Weibull函数拟合二化螟种群内幼虫个体间发育历期分布,当常态历期为x时,完成发育个体占总个体的比例F(x)可以下式表达: F(x)=1-Exp{-[(x-0.6546)/0.3795]~(3.8526)}  相似文献   

柑桔臀纹粉蚧的研究     

唐尚杰  泰汉忠  王建明  顾萍 《上海交通大学学报(农业科学版)》1992,(1)

柑桔臀纹粉蚧在上海地区常规栽培管理的十字景天上一年发生3代,以受精雌成虫或产卵雌成虫越冬。本文报导了此虫的年生活史及各虫态的生活习性、发育进程与历期,并测得其卵的发育起点温度为11.49±0.53℃;有效积温为73.11±3.39日度。以15%铁灭克颗粒剂根施;40%氧化乐果10O倍液浇灌,防治效果在97%以上.  相似文献   

生物多样性评判林分抗虫性研究方法   总被引：4，自引：0，他引：4  

王鸿哲  李孟楼  张学武 《西北农林科技大学学报(自然科学版)》2004,32(7):123-127

为建立相关模型,实现利用生物多样性指数评判林分抗虫性的目的,研究了林内昆虫的丰富度指数、物种多样性指数及均匀度指数等与林分害虫危害程度、林分结构变化之间的关系。阐述了评判林分抗虫性的常用物种多样性指数(Shannon-Wiener指数、Simpson指数、McIntoch指数)和均匀度指数(Pielou指数、Alatalo指数)及其应用中应注意的问题,论述了利用生物多样性评判林分抗虫性研究的基本内容与方法,讨论了林分抗虫性的多样性阈值研究方法。  相似文献   

Threshold criteria for heavy metals in the soils of hazard-free dry fruit production regions of China     

Jianguang Zhang  Yufang Liu  Junyi Zhou  Suping Guo  Baoguo Li  Wenjiang Wang 《Frontiers of Agriculture in China》2007,1(2):193-196

Determination of proper threshold criteria for heavy metals in soils is an important basis for hazard-free dry fruit production in China. Based on the detection of heavy metal contents in soils in this study, it is initially concluded that the soils for dry fruit production in China are suitable for hazard-free growing. Moreover, the soil safety qualification for dry fruit production is much better than that in some developed countries or regions, which might help our production have a competitive advantage on the international market. However, soil Cr contents in the country are slightly higher, so that it is necessary to take steps to control any contamination during the whole chain of production. The following threshold criteria for heavy metals in soils is suggested according to physical, ecological and economical considerations: Hg 0.15 mg/kg; As 20 mg/kg; Pb 50 mg/kg; Cd 0.30 mg/kg and Gr 200 mg/kg. Translated from Acta Pedologica Sinica, 2005, 42(1): 153–155 [译自: 土壤学报]  相似文献   

枸杞瘿螨的生物学特性及其有效积温的研究   总被引：2，自引：0，他引：2  

徐林波  段立清 《内蒙古农业大学学报(自然科学版)》2005,26(2):55-57

室内恒温条件下测定了枸杞瘿螨Aceria pallida Keifer的发育起点温度和有效积温。枸杞瘿螨产卵前期的发育起点温度和有效积温分别为7．23℃和50．99日度；卵和幼若螨期发育起点温度和有效积温分别为5．51℃和167．68日度；全世代的发育起点温度和有效积温分别为6．08℃和217．05日度。发育进度有效积温模型分别为4N4卵前=50．99／[T-7．23]；4N4卵幼=167．68／[T-5．51]和4N4世代=217．05／[T-6．08]。在15℃～35℃恒温条件下发育历期与温度呈负相关，其中在25℃～30℃之间时枸杞瘿螨发育快，数量多，该温度范围是枸杞瘿螨生长发育的最适温度。根据呼和浩特地区气象资料，枸杞瘿螨在呼和浩特地区1a发生的理论代数为10代～12代。  相似文献   

沙地毛白杨速生丰产林节水灌溉的研究   总被引：1，自引：0，他引：1  

王文全  李秀江  贾玉彬  张振江  华章保  刘素萍 《河北农业大学学报》2001,24(1):33-37

以提高灌溉水利用为核心，以植物生理学和生态学以及树木生长为依据，连续８年对毛白杨速生丰产林节水灌溉的理论与技术进行了较为系统的，结果表明，利用科学的灌溉阈值，抓住关键的灌溉时期，确定有效的灌溉范围和经济的灌溉量，就可以较少的水分投入获取较高的林木生长量，在春夏干旱季节（０５－０６月），以田间持水量的５０％作为阈值实施灌水，具有极显著的近期和后期水分补偿效应，与较高灌溉水平（阈值为７０％）相比，灌溉水利用率提高４６．８０％，灌水量减少２２．８１％，材积生长量增加１３．３０％，经济效益提高３１．２８％。  相似文献   

小波变换用于抑制干扰信号几种方法的比较研究     

杨春玲  戴景民  刘超 《湖南农业大学学报(自然科学版)》2002,29(6)

对小波变换抑制干扰信号提取真实信号的3种方法，即小波滤波器消噪法；软、硬阈值消噪法；基于模极大值的小波去噪方法，进行了比较研究。给出了每种方法的适用范围及具体的算法、仿真结果，对于选用小波变换工具进行信号处理具有一定的理论意义和实用价值。  相似文献   

青杨叶锈病防治指标的研究   总被引：4，自引：0，他引：4  

孟繁荣  白纯杰 《东北林业大学学报》1997,25(3):18-21

在东北地区青杨叶锈病严重发生地区，对小里杨１．２．３年生苗木。分别按病情等级对苗木的生长量，损失率进行测定。确定经济阈值和防治指标：插条苗经济阈值的病情指数为１４。防指标的产现情 指数１５－１６时为重点防治。大于１８时应全面防治；平茬苗经济阈值的病情指数为２１。  相似文献