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41.
Michela Marchi Sven Erik JørgensenEloy Bécares Ilaria CorsiNadia Marchettini Simone Bastianoni 《Ecological modelling》2011,222(16):2992-3001
Using a dynamic model of Lake Chozas developed by Marchi et al. (2011), we tested three hypotheses about recovery of the indigenous community and water quality after radical changes caused by introduction of an invasive allochthonous crayfish, Procambarus clarkii:
- 1.
- Can the lake resist the pressure of an invasive species, like P. clarkii, by adaptation?
- 2.
- Can the ecosystem recover when all the crayfish are removed and low phosphorus concentrations persist in inflow water?
- 3.
- Does the simulated recovery of submerged vegetation occur at a total phosphorus concentration below 100 mg TP m−3, as estimated by Scheffer et al. (1993), Scheffer (1997), Jeppesen et al. (1998) and Zhang et al. (2003)?
- 1.
- Lake Chozas can at least partly resist by adaptation. A combination of possible parameter changes could lead to a significant increase in eco-exergy.
- 2.
- Removal of the phosphorus represented by crayfish (by harvesting) implies complete recovery of the lake and its eco-exergy, albeit not necessarily with the same organisms having the same properties.
- 3.
- The expected hysteresis created by introduction and harvesting of crayfish is observed under the following conditions: phytoplankton dominance at total phosphorus ≥ about 200-250 mg TP m−3 and submerged vegetation returns at total phosphorus < 100 mg TP m−3.
42.
Ecosystem constraints are both ontic and epistemic. They limit activity, and as problems to be solved they drive organization, which is our hypothesis:
The driver of organization is constraint.Solutions proliferate further constraints in an unending spiral of problem (constraint) generation and solution. As constraints proliferate, behavior narrows, and species diversify to compensate (paradox of constraint). Resource enrichment reduces constraints, releases behavior, and reduction of challenges decreases diversity (paradox of enrichment)—high diversity is expressed in low-resource environments and low diversity in high-resource environments. A three-part model of constraints is formulated for non-living systems, and also for goal-directed, problem-solving biota. Mode 1: dynamical means behavior is co-determined by internal states and external inputs. Mode 2: cybernetic employs negative feedback to keep dynamics within goal-oriented operating limits. Mode 3: model-making entails ability to represent (model) physical reality and respond to both phenomenal (modeled) and physical inputs; this property distinguishes living from nonliving systems. Principal sections of the paper elaborate dynamical constraints (three classes), boundary constraints (expressed in edge effects and trophic dynamics), physical constraints (space, time, temperature), chemical constraints (environment fitness, ecological stoichiometry, chemical evolution, limiting factors), coding constraints (environmental vs. genetic coding), network and pathway constraints (connectivity), and natural selection constraints (fitting to the biosphere). Consideration of how the world would look without constraints suggests how fundamental these are in ecosystem emergence, and how the next property in this series, differentiation, would be unmotivated without them. We conclude that constraints as a category are under-studied in ecology, poorly understood in ecological phenomenology, and (our hypothesis) comprise a ubiquitous organizing force in nature. 相似文献
43.
Danika Hill Matthew J. Morr Thibault Stalder Sven Jechalke Eva Top Anne T. Pollar Inna Popova 《环境科学学报(英文版)》2021,33(2):117-130
Although animal manure is applied to agricultural fields for its nutrient value, it may also contain potential contaminants. To determine the variability in such contaminants as well as in valuable nutrients, nine uncomposted manure samples from Idaho dairies collected during 2.5 years were analyzed for macro- and micro-nutrients, hormones, phytoestrogens, antibiotics, veterinary drugs, antibiotic resistance genes, and genetic elements involved in the spread of antibiotic resistance. Total N ranged from 6.8 to 30.7 (C:N of 10 to 21), P from 2.4 to 9.0, and K from 10.2 to 47.7 g/kg manure. Zn (103 – 348 mg/kg) was more abundant than Cu (56 – 127 mg/kg) in all samples. Phytoestrogens were the most prevalent contaminants detected, with concentrations fluctuating over time, reflecting animal diets. This is the first study to document the presence of flunixin, a non-steroidal anti-inflammatory drug, in solid stacked manure from regular dairy operations. Monensin was the most frequently detected antibiotic. Progesterones and sulfonamides were regularly detected. We also investigated the relative abundance of several types of plasmids involved in the spread of antibiotic resistance in clinical settings. Plasmids belonging to the IncI, IncP, and IncQ1 incompatibility groups were found in almost all manure samples. IncQ1 plasmids, class 1 integrons, and sulfonamide resistance genes were the most widespread and abundant genetic element surveyed, emphasizing their potential role in the spread of antibiotic resistance. The benefits associated with amending agricultural soils with dairy manure must be carefully weighed against the potential negative consequences of any manure contaminants. 相似文献
44.
Temporal changes in hydrography affect suspended particulate matter (SPM) composition and distribution in coastal systems,
potentially influencing the diets of suspension feeders. Temporal variation in SPM and in the diet of the mussel Perna perna, were investigated using stable isotope analysis. The δ13C and δ15 N ratios of SPM, mussels and macroalgae were determined monthly, with SPM samples collected along a 10 km onshore–offshore
transect, over 14 months at Kenton-on-Sea, on the south coast of South Africa. Clear nearshore (0 km) to offshore (10 km)
carbon depletion gradients were seen in SPM during all months and extended for 50 km offshore on one occasion. Carbon enrichment
of coastal SPM in winter (June–August 2004 and May 2005) indicated temporal changes in the nearshore detrital pool, presumably
reflecting changes in macroalgal detritus, linked to local changes in coastal hydrography and algal seasonality. Nitrogen
patterns were less clear, with SPM enrichment seen between July and October 2004 from 0 to 10 km. Nearshore SPM demonstrated
cyclical patterns in carbon over 24-h periods that correlated closely with tidal cycles and mussel carbon signatures, sampled
monthly, demonstrated fluctuations that could not be correlated to seasonal or monthly changes in SPM. Macroalgae showed extreme
variability in isotopic signatures, with no discernable patterns. IsoSource mixing models indicated over 50% reliance of mussel
tissue on nearshore carbon, highlighting the importance of nearshore SPM in mussel diet. Overall, carbon variation in SPM
at both large and small temporal scales can be related to hydrographic processes, but is masked in mussels by long-term isotope
integration. 相似文献
45.
Christer Wiklund Adrian Vallin Magne Friberg Sven Jakobsson 《Behavioral ecology and sociobiology》2008,62(3):379-389
Insects that hibernate as adults have a life span of almost a whole year. Hence, they must have extraordinary adaptations
for adult survival. In this paper, we study winter survival in two butterflies that hibernate as adults and have multimodal
anti-predator defences—the peacock, Inachis io, which has intimidating eyespots that are effective against bird predation, and the small tortoiseshell, Aglais urticae, which does not have an effective secondary defence against birds. We assessed predation on wild butterflies hibernating
in the attic of an unheated house, as well as survival of individually marked butterflies placed by hand on different sites
in the attic. Our objectives were to assess (1) the number of butterflies that were killed during hibernation, (2) whether
survival differed between butterfly species, and (3) how predation was related to hibernation site and the identity of the
predator. There was a strong pulse of predation during the first 2 weeks of hibernation: 58% of A. urticae and 53% of I. io were killed during this period. Thereafter, predation decreased and butterfly survival equalled 98% during the final 16 weeks
of hibernation. There was no difference in survival between the two butterfly species, but predation was site-specific and
more pronounced under light conditions in locations accessible to a climbing rodent, such as the common yellow-necked mouse,
Apodemus flavicollis. We contend that small rodents are likely important predators on overwintering butterflies, both because rodents are active
throughout winter when butterflies are torpid and because they occur at similar sites. 相似文献
46.
An assertion deeply rooted in the ornithological literature holds that sex-specific mortality causes a sex ratio disparity
(SRD) between complete and incomplete broods. Complete broods are thought to reflect the primary sex ratio before any bias
introduced by developmental mortality. Contrary to this view, however, complete and incomplete broods should exhibit identical
sex ratio distributions even when the sexes experience differential mortality, as shown in the classic paper of Fiala (Am
Nat 115: 442–444, 1980). Therefore, in partially unsexed samples, primary sex ratio biases cannot be distinguished from biases
caused by differential mortality. In addition, complete broods do not represent primary sex ratio more accurately than incomplete
ones and might even be misleading. Despite Fiala’s prediction, SRD does occur in some empirical studies. We show that this
pattern could arise if (1) primary sex ratio affects chick mortality rates independently of sex (direct effect), (2) primary
sex ratio covaries with a variable that also affects mortality rate, or (3) sex differential mortality covaries with overall
mortality rate (indirect effects). Direct effects may cause stronger SRD than indirect ones with a smaller and opposite bias
in the overall sex ratio and could also lead to highly inconsistent covariate effects on brood sex ratios. These features
may help differentiate direct from indirect effects. Most interestingly, differences in covariate effects between complete
and incomplete broods imply that influential variables are missing from the analysis. 相似文献
47.
48.
Terry V.Callaghan Lars Olof Bjrn Yuri Chernov Terry Chapin Torben R.Christensen Brian Huntley Rolf A.Ims Margareta Johansson Dyanna Jolly Sven Jonasson Nadya Matveyeva Nicolai Panikov Walter Oechel Gus Shaver Sibyll Schaphoff Stephen Sitch Christoph Zckler 《Ambio-人类环境杂志》2004,33(7):362-368
引言
北极已成为对当前气候波动和预计的全球变暖增强的影响进行评估的重要地区.原因有以下几个方面:①在过去几十年中北极经历了大幅度的变暖过程(温度平均升高3℃,而在许多地区温度升高了4~5℃);②气候预测表明气候呈现持续变暖趋势,在2080年之前年平均气温升高4~5℃;③近期的气候变暖正在影响北极的环境和经济,这些影响还会加大,并对生活方式、文化及生态系统造成影响;④北极的变化可能会影响到地球上的其它地区. 相似文献
49.
Terry V.Callaghan Lars Olof Bjrn Yuri Chernov Terry Chapin Torben R.Christensen Brain Huntley Rolf A.Ims Margareta Johansson Dyanna Jolly Sven Jonasson Nadya Matveyeva Nicolai Panikov Walter Oechel Gus Shaver Sibyll Schaphoff Stephen Sitch 《Ambio-人类环境杂志》2004,33(7):435-444
北极生态系统的生物和物理过程会在不同的时间、空间尺度上对地球生态系统产生反馈作用,并与之相互影响.气候变化对北极地区的影响及其对全球气候系统的反馈主要存在着四种潜在机制反照率改变、生态系统对温室气体的排放或吸收、甲烷类温室气体的排放、影响海洋暖流淡水量的增长.这些反馈机制在某种程度上是由生态系统的分布和特征,尤其是大规模植被区域变化来控制的.通过少量全年的CO2通量测量表明,目前在地理分布上碳源区要比碳汇区要多.根据目前现有的关于CH4排放源地信息表明,景观规模上的CH4排放量对北极地区的温室效应平衡至关重要.北极地区的能量和水量平衡在变化的气候下,也是一个很重要的反馈机制.植被密度以及分布范围的增加会导致反射率的下降,因而会使地表吸收更多的能量.其效果可能会抵消由于极地沙漠地带向极地苔原带的的转化,或极地苔原带向极地森林带的转化,而造成的植被总净初级生产力碳沉降能力的提高而引起的负反馈.永久冻土带的退化对示踪气体动力学有着很复杂的影响.在不连续的永久冻土带地区,升温将会导致其完全消失.依赖于当地水文条件,温室气体排放可能由于气候环境变的干燥或湿润而使得其通量有所变化.总的来说,影响反馈的各种过程复杂的相互作用,以及这些过程随着时间地点的变化,加之数据的缺乏,又会在陆地生态系统气候变化对气候系统产生反馈作用的净效应估计上,产生许多的不确定性,这种不确定性将会影响到一些反馈的大小和方向. 相似文献
50.
Adrian Vallin Sven Jakobsson Johan Lind Christer Wiklund 《Behavioral ecology and sociobiology》2006,59(3):455-459
Butterflies that hibernate exhibit particularly efficient defence against predation. A first line of defence is crypsis, and
most hibernating butterflies are leaf mimics. When discovered, some species have a second line of defence; the peacock, I. io, when attacked by a predator flicks its wings open exposing large eyespots and performs an intimidating threat display. Here
we test the hypothesis that butterflies relying solely on leaf mimicking and butterflies with an intimidating wing pattern,
when attacked, exhibit different behavioural suites—because leaf mimicking is best implemented by immobility, whereas intimidating
coloration is best implemented by intimidating behaviour. In laboratory experiments blue tits, Parus caeruleus, were allowed 40 min to attack single individuals of three species of butterfly: one relying solely on crypsis, the comma,
Polygonia c-album; one relying on intimidating wing pattern in addition to crypsis, the peacock; and one intermediate species, the small tortoiseshell
Aglais urticae. The results are in accordance with expectations and demonstrate that: (1) birds take longer to discover the leaf mimicking
species, the comma, than the tortoiseshell and the peacock; (2) the comma remained motionless throughout experimental trials
but small tortoiseshells and peacocks flicked their wings when attacked; (3) the most intimidating butterfly, the peacock,
started flicking its wings at a greater distance from the attacking bird than the small tortoiseshell; and (4) the intimidating
pattern and behaviour of peacocks was effective—when discovered, all peacocks survived interactions with blue tits, whereas
only 22% of commas and 8% of small tortoiseshells survived. 相似文献