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901.
902.
Estimates of soil N2O and NOemissions at regional and country scales arehighly uncertain, because the most widely usedmethodologies are based on few data, they do notinclude all sources and do not account forspatial and seasonal variability. To improveunderstanding of the spatial distribution of soilNO and N2O emissions we have developedsimple multi-linear regression models based onpublished field studies from temperate climates.The models were applied to create spatialinventories at the 5 km2 scale of soil NOand N2O emissions for Great Britain. The N2O regression model described soilN2O emissions as a function of soil N input,soil water content, soil temperature and land useand provided an annual N2O emission of 128 kt N2O-N yr-1. Emission rates largerthan 12 kg N2O-N ha-1 yr-1 werecalculated for the high rainfall grassland areasin the west of Great Britain.Soil NO emissions were calculated using tworegression models, which described NO emissionsas a function of soil N input with and without afunction for the water filled pore space. Thetotal annual emissions from both methods, 66 and7 kt NO-N yr-1, respectively, span the rangeof previous estimates for Great Britain. 相似文献
903.
904.
905.
Comparing environmental influences on coral bleaching across and within species using clustered binomial regression 总被引:1,自引:0,他引:1
Differential susceptibility among reef-building coral species can lead to community shifts and loss of diversity as a result of temperature-induced mass bleaching events. We evaluate environmental influences on coral colony bleaching over an 8-year period in the Florida Keys, USA. Clustered binomial regression is used to develop models incorporating taxon-specific responses to the environment in order to identify conditions and species for which bleaching is likely to be severe. By building three separate models incorporating environment, community composition, and taxon-specific responses to environment, we show observed prevalence of bleaching reflects an interaction between community composition and local environmental conditions. Environmental variables, including elevated sea temperature, solar radiation, and reef depth, explained 90% and 78% of variability in colony bleaching across space and time, respectively. The effects of environmental variables were only partially explained (33% of variability) by corresponding differences in community composition. Taxon-specific models indicated individual coral species responded differently to local environmental conditions and had different sensitivities to temperature-induced bleaching. For many coral species, but not all, bleaching was exacerbated by high solar radiation. A 25% reduction in the probability of bleaching in shallow locations for one species may reflect an ability to acclimatize to local conditions. Overall, model results indicate predictions of coral bleaching require knowledge of not just the environmental conditions or community composition, but the responses of individual species to the environment. Model development provides a useful tool for coral reef management by quantifying the influence of the local environment on individual species bleaching sensitivities, identifying susceptible species, and predicting the likelihood of mass bleaching events with changing environmental conditions. 相似文献
906.
Insect larvae increase in size with several orders of magnitude throughout development making them more conspicuous to visually
hunting predators. This change in predation pressure is likely to impose selection on larval anti-predator behaviour and since
the risk of detection is likely to decrease in darkness, the night may offer safer foraging opportunities to large individuals.
However, forsaking day foraging reduces development rate and could be extra costly if prey are subjected to seasonal time
stress. Here we test if size-dependent risk and time constraints on feeding affect the foraging–predation risk trade-off expressed
by the use of the diurnal–nocturnal period. We exposed larvae of one seasonal and one non-seasonal butterfly to different
levels of seasonal time stress and time for diurnal–nocturnal feeding by rearing them in two photoperiods. In both species,
diurnal foraging ceased at large sizes while nocturnal foraging remained constant or increased, thus larvae showed ontogenetic
shifts in behaviour. Short night lengths forced small individuals to take higher risks and forage more during daytime, postponing
the shift to strict night foraging to later on in development. In the non-seasonal species, seasonal time stress had a small
effect on development and the diurnal–nocturnal foraging mode. In contrast, in the seasonal species, time for pupation and
the timing of the foraging shift were strongly affected. We argue that a large part of the observed variation in larval diurnal–nocturnal
activity and resulting growth rates is explained by changes in the cost/benefit ratio of foraging mediated by size-dependent
predation and time stress. 相似文献
907.
Although assortative mating is widespread among long-lived monogamous birds, the underlying mechanisms still remain unclear
in many species. In this study, we analysed assortative mating by age and body mass in the common tern Sterna hirundo with special regard to mate choice decisions of newly paired birds. To assess whether assortative mating by age is an active
decision involving either homotypic or directional preferences or rather a passive process due to restricted availability
of potential mates, we analysed the influence of age-dependent arrival date and cohort size. Furthermore, we looked for direct
benefits in terms of reproductive success. Common terns mated assortatively by age and arrival date but not by body mass at
arrival. Assortative mating by age was age dependent and was detected mainly in younger birds, whereas birds older than 8 years
rather re-paired with younger ones. The availability of same-aged mates was restricted by cohort size and arrival date. We
found no general evidence for better reproductive performance of same-aged pairs. Instead, relative reproductive success was
related to own age and the relative age of mate: It should be advantageous for any bird to acquire an old mate; hence, assortative
mating by age seems to be beneficial only for old terns but not for young ones. Age-assortative mating in common terns occurred
by both passive and active processes, which are not mutually exclusive. Our results do not indicate a homotypic but a directional
preference and support the theory that high-quality (older/experienced) individuals tend to mate assortatively if same-aged
mates are available, which leaves low-quality (young/inexperienced) individuals to mate among themselves. 相似文献
908.
温度对奶牛粪便温室气体排放的影响 总被引:3,自引:0,他引:3
采用封闭罐-气相色谱法对4种不同温度处理下奶牛粪便温室气体排放速率进行测定.结果表明,温度是影响奶牛粪便温室气体排放的主要因子,温度较低时奶牛粪便温室气体排放速率低,而且随着奶牛粪便处理温度升高而增大.在5、15、25和35℃4个处理中,奶牛粪便CO2排放速率两两之间差异显著;CH4排放速率除了5和15℃处理差异不显著之外,其他两两处理之间差异显著;35℃处理时N2O排放速率与其他温度的排放速率差异均显著,其他两两处理之间差异不显著. 相似文献
909.
910.
城市污泥堆肥过程中气温对堆体温度影响的模拟 总被引:8,自引:1,他引:7
在静态垛堆肥过程中,气温的变化会对堆体温度造成影响,这对堆肥过程中的堆体温度控制具有重要意义.但迄今为止,对此问题仍缺乏研究.本文引入小波分析方法对气温和堆体温度数据进行去噪和压缩处理,提取出气温波动引起的堆体温度波动信号,然后对气温波动信号和堆体温度波动信号进行分周期拟合,获得一一对应的振幅和相位差.结果表明,对于强制通风静态垛堆肥,气温波动对堆体下层(75cm)的影响最大,最大值为0.186℃,最小值为0.132℃,平均值为0.159℃;对中层(50cm)的影响最小,但随着堆肥进程的持续有增大的趋势;对上层(25cm)影响的最大值为0.105℃,最小值为0.065℃,平均值为0.085℃.从相位差上看,堆体中层(50cm)的相位差始终最大,在堆肥的降温期呈现明显减小的趋势;上层(25cm)的相位差随着堆肥进程的持续有明显增大的趋势;下层(75cm)的相位差在整个堆肥进程中呈缓慢升高的趋势.通过影响强度和相位差综合分析发现,堆体上层物料和下层物料在热量散失过程中可能存在两种不同的热交换机制,即上层物料以稳态热传导和自然对流为主,而下层物料则以非稳态热对流为主. 相似文献