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981.
Ying Hu Liu De Li Liu Min An Yin Lian Fu Ren Sen Zeng Shi Ming Luo Hanwen Wu Jim Pratley 《Ecological modelling》2009
Many plant species defend themselves against herbivorous insects indirectly by producing and releasing induced volatiles to attract natural enemies of the herbivores. In this paper, we consider the recruitment of natural enemies attracted by plant-induced volatiles and introduce the An–Liu–Johnson–Lovett model into the Lotka–Volterra model in an attempt to add this missing vital link in tritrophic interaction. Increase in attraction strength of plant-induced volatiles to the natural enemy leads to high fluctuation amplitude of plant biomass and herbivore population. When the attack strength of natural enemies reaches a certain level, fluctuation amplitude of plant biomass and herbivore population will decrease and plant biomass will approach to its environmental carrying capacity. The simulation demonstrates that plant volatile compounds induced by insects have led to the introduction of a third tritrophic level, e.g., natural enemies, into the plant–herbivore system, resulting in the coexistence of plants, insects, and natural enemies during the evolution process. 相似文献
982.
研究建设用地空间错配特征及内在机制,对纠正土地资源错配、优化土地资源配置机制具有现实意义。基于资源错配理论对土地资源错配理论开展梳理,提出建设用地错配机制假说,运用边际分析法和计量方法构建建设用地空间错配测度模型及机制检验模型,并以湖北省为例进行实证研究。结果表明:①1996—2017年湖北省建设用地过度错配与短缺错配并存,空间错配程度总体上有所改善,但局部地区错配程度加剧。②土地负外部性扩散、非均衡发展、非市场化供应、土地财政依赖等加剧了建设用地空间错配,优化产业结构、减少政府腐败、发展多元所有制等有利于降低建设用地空间错配程度。③1996—2017年湖北省建设用地空间错配效率损失由6.92%下降到3.84%,年均减少2.03%,效率损失得到缓解。④从损失值看,湖北省建设用地空间错配效率损失严重,1996—2017年累计经济损失达3.90×10^4亿元。主要结论:建设用地空间错配测度模型兼顾了土地配置的效率与公平,可以作为建设用地空间错配程度衡量的有效方法;建设用地空间错配已经成为阻碍经济增长的重要因素之一,纠正建设用地空间错配,能有效促进区域经济增长;土地市场配置和政府主导配置均会带来建设用地空间错配,建设用地配置中一个“有效的市场”与“有为的政府”结合十分必要且迫切。 相似文献
983.
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985.
Predators can have significant nonlethal effects on prey by modifying prey behaviour through chemically mediated interactions.
We examined behavioural responses of wood frog (Ranasylvatica) and American toad (Bufoamericanus) tadpoles to both direct and indirect chemical signals associated with a predatory odonate (Anaxjunius). In laboratory trials, tadpoles of both species responded strongly to water conditioned with Anax nymphs by decreasing foraging rates, becoming immobile, and moving away from the stimulus. The responses to water conditioned
with starved Anax versus Anax that fed on conspecific tadpoles did not differ significantly; these results suggest that tadpoles rely primarily on direct
signals to detect odonates. Rana did not respond to water conditioned with conspecific tissue extracts, while Bufo responded with behaviours that were indistinguishable from those of tadpoles exposed to Anax chemicals. In a field experiment, the responses of R. sylvatica tadpoles to Anax chemicals were similar to those of tadpoles observed in the laboratory. Collectively, our data indicate that tadpoles of
both species use chemical cues to assess predation risk from other community members. Tadpoles can selectively distinguish
members who pose a threat, and only evacuate food patches or reduce foraging rates when in danger. These behaviours appear
to be adaptive and are consistent with the predictions of optimality theory.
Received: 1 August 1997 / Accepted after revision: 22 November 1997 相似文献
986.
Abalos M Parera J Estévez A Solé M Fabregat MC Piña B Navarro A Abad E 《Chemosphere》2011,82(1):64-71
Aquacultured fish gilthead seabream (Sparusaurata), previously exposed to low levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) trough the diet for a 13 months period, were fed on a clean feed for another 22 months. Gilthead seabream is a protandrous hermaphrodite species and this “decontamination” period coincided with the stages of sex differentiation, maturity and reproduction of the fish. PCDD/F levels in the fish tissues (i.e. muscle, liver, perivisceral fat and gonads), expressed in pg WHO-TEQ g−1 fresh weight, showed a general decreasing trend during the “decontamination” period. However, this general trend varied among tissues and was also dependent on sex and lipid contents. Toxicological effects affecting fish behaviour and hepatic marker responses were also evaluated. The results pointed out that exposure to PCDD/Fs did not have an impact on fish development and reproduction, since the proportion of sexes found after the sex reversal process was within the normal range described for this species. In addition, long-term exposure to low PCDD/F levels did not significantly affect the response of most of the biochemical markers considered. On the contrary, some of them (e.g. EROD activity) showed variations in their responses during the sex differentiation process and onwards. Finally, the hepatic AhR mRNA levels increased during dioxin exposure but they returned to values typical for non-exposed fish after the “decontamination” period. 相似文献
987.
Chemical oxidation of cable insulating oil contaminated soil 总被引:2,自引:0,他引:2
Leaking cable insulating oil is a common source of soil contamination of high-voltage underground electricity cables in many European countries. In situ remediation of these contaminations is very difficult, due to the nature of the contamination and the high concentrations present. Chemical oxidation leads to partial removal of highly contaminated soil, therefore chemical oxidation was investigated and optimized aiming at a subsequent bioremediation treatment. Chemical oxidation of cable oil was studied with liquid H2O2 and solid CaO2 as well as permanganate at pH 1.8, 3.0 and 7.5. Liquid H2O2 most effectively removed cable oil at pH 7.5 (24%). At pH 7.5 poor oil removal of below 5% was observed with solid CaO2 and permanganate within 2 d contact time, whereas 18% and 29% was removed at pH 1.8, respectively. A prolonged contact time of 7 d showed an increased oil removal for permanganate to 19%, such improvement was not observed for CaO2.Liquid H2O2 treatment at pH 7.5 was most effective with a low acid use and was best fit to a subsequent bioremediation treatment. To further optimize in situ chemical oxidation with subsequent bioremediation the effect of the addition of the iron catalyst and a stepwise liquid H2O2 addition was performed. Optimization led to a maximum of 46% cable oil removal with 1469 mM of H2O2, and 6.98 mM Fe(II) chelated with citric acid (H2O2:FeSO4 = 210:1 (mol mol−1). The optimum delivery method was a one step addition of the iron catalyst followed by step wise addition of H2O2. 相似文献
988.
989.
990.
我国纺织噪声暴露现状及听力损失情况预测 总被引:1,自引:0,他引:1
通过对国内纺织业从业人员数量、工龄的统计和企业实地噪声情况的调查,借鉴ISO1999—1975(E)和其它相关方法预测我国纺织行业噪声暴露情况和从业人员的听力损失情况。经过预测,结果显示纺织从业人员暴露于85dB以下噪声的约有289.3万人,85~95dB约有381.2万人,高于95dB约有329.5万人;对于听力损失的预测,采用悲观和乐观法分别进行预测,结果表明约有100.57万人和21.61万人患有听力损失;结合实际调研情况对预测数据进行修正,结果表明目前我国纺织行业约有70.96万人患有听力损失。 相似文献