Effects of ozone on inter- and intra-species competition and photosynthesis in mesocosms of Lolium perenne and Trifolium repens

Trifolium repens and Lolium perenne were exposed as both monocultures and two-species mixtures to an episodic rural ozone regime in large, well-watered containers within solardomes for 12 weeks. There were reductions in biomass for T. repens, but not L. perenne, and the proportion of T. repens decreased in ozone-exposed mixtures compared to the control. In addition, leaf biomass of T. repens was maintained at the expense of biomass partitioning to the stolons. The decreased growth corresponded with decreased photosynthetic capacity for T. repens, however, by the end of the exposure there was also decreased photosynthetic capacity of L. perenne, a species previously considered insensitive to ozone. The observed decreases in photosynthetic efficiency and capacity in elevated ozone indicate that the ability of such ubiquitous vegetation to act as a sink for atmospheric carbon may be reduced in future climates.     

Assessment of Cs and Sr accumulation in two epiphytic species of Tillandsia (Bromeliaceae) in vitro

Multiple nuclides commonly occur together and exert toxicity simultaneously, but the difference between single and combined effects of the nuclides is rarely investigated. Epiphytic Tillandsia species are efficient air pollution biomonitors, but rarely used to monitor nuclide contamination. Two Tillandsia species, that is, T. brachycaulos and T. stricta, were chosen to test their capacity to accumulate Cs and Sr. Most plants were able to endure Cs and Sr stress for a long period, which suggested these species could resist toxic elements physiologically and metabolically. With the increasing Cs or Sr concentrations, nuclide contents in both species increased significantly, indicating the potential of Tillandsia species in monitoring nuclide pollutants. However, when the plants were treated with combined nuclides, the content of each ion decreased distinctly compared to those treated with single ion, which suggested Cs and Sr influenced and inhibited each other. In addition, T. brachycaulos seemed more efficient in the uptake of Sr, while T. stricta was more efficient for Cs. Both species accumulated more Sr than Cs at low concentrations, while more Cs than Sr at high concentrations. These results indicated that the uptake of Cs and Sr was related to both the concentrations of the nuclides and the plant species exposed.     

Ecological and social determinants of spacing behaviour in desert baboon groups

This paper investigates the determinants of individual spacing behaviour in a desert baboon population (Papio cynocephalus ursinus). Patterns of neighbour proximity and neighbour density were examined among adults in four groups under different ecological and social conditions (through instantaneous sampling during focal follows). Initial analysis of these data shows that (1) the use of vertical substrates (refuges such as tall trees and cliff faces) can confound patterns of spacing, and (2) individual differences in spacing can depend on the spatial scale over which it is measured. To minimise these substrate and scale effects, this analysis focuses on animals which are off refuges and examines spacing behaviour through its underlying statistical `dimensions' (identified through factor analysis). Analysis of these dimensions indicates that sex, group size, activity-habitat and female reproductive state can all have independent effects on spacing: (1) males are more dispersed than females in smaller groups, (2) male and female dispersion increases with time spent in foraging habitats, and (3) female dispersion is reduced during lactation. According to the hypotheses tested, these results indicate that feeding competition only affects spacing behaviour during foraging while predation risk plays little or no role in spacing. Most aspects of spacing behaviour are best explained by male reproductive strategies and their social repercussions. Received: 25 May 1998 / Accepted after revision: 18 July 1998     

Spermatophore characteristics in bushcrickets vary with parasitism and remating interval

Male bushcrickets provide females with a nuptial gift, a spermatophore, which is transferred to females at mating. The spermatophore consists of a gelatinous mass, the spermatophylax, and the sperm-containing ampulla. Male spermatophore size is positively correlated with insemination rate and female refractory period and therefore with male reproductive success. In this study, we examined spermatophylax weight, ampulla weight and sperm number in males of Poecilimon mariannae parasitized by the acoustically orienting fly Therobia leonidei. We show that in parasitized males, spermatophylax weight decreases with the level of parasitism. In line with the hypothesis that parasitism is a cost to reproduction, we found that spermatophylax weight was reduced at remating. In contrast, the replenishment of the spermatophylax in unparasitized males was complete after 2 days and was increased no further after 3 days. Both sperm number and ampulla weight showed an increase over time since last mating and sperm production was estimated at a constant rate of 500,000 per day in all individuals, regardless of parasitism. The allocation of investment in components of the spermatophore varies greatly with parasitism and remating. Both factors had rather independent effects on spermatophore constitution, revealing functional constraints acting on spermatophore characteristics in bushcrickets, which are important for understanding the selection pressures working on its components. Received: 13 September 1999 / Received in revised form: 4 February 2000 / Accepted: 13 March 2000     

大力发展循环经济 抢占国际竞争高地

中国在后国际金融危机时代要保持国民经济持续稳定快速增长,必须大力发展循环经济,全面提升国际竞争力。中国经济所处的发展阶段决定了不仅要在包括战略性新兴产业的高新技术领域抢占国际竞争的制高点,更要在国内市场需求快速增长的传统产业领域,通过自主创新抢占国际竞争的制高点。     

土木建筑施工安全生产聚集性活动的安全专项管理

土木建筑安全生产形势严峻,重特大事故时有发生,因此控制工程建设过程的安全生产事故意义重大。基于作业条件危险性评价原理和安全生产责任与事故管理机制,提出土木建筑施工作业活动聚集性安全生产专项管理创新方法。基于国内相关研究成果,建议了土木建筑施工活动聚集性程度的分类标准、分级管理模式,以及聚集性活动安全专项管理计划。     

厌氧氨氧化菌与其他细菌之间的协同竞争关系

随着污水脱氮行业的蓬勃发展,各种新工艺、新理论层出不穷.厌氧氨氧化(Anammox)工艺以其独特的优点脱颖而出,成为最具应用前景的新工艺.厌氧氨氧化菌作为该过程的执行者目前已发现5属17种,本文主要对5属17种的厌氧氨氧化菌进行总结,并对厌氧氨氧化菌种内关系中的群体感应系统进行详细介绍,此外还介绍了厌氧氨氧化菌与硝化菌、反硝化菌以及厌氧甲烷氧化菌之间的协同与竞争关系.最后给出常见竞争因素对厌氧氨氧化种群结构的影响,通过控制竞争因素来实现对厌氧氨氧化种群结构的调节.本文将厌氧氨氧化菌微生物生态学与厌氧氨氧化污水处理工艺相结合,为厌氧氨氧化工艺在污水生物处理中的应用提供理论依据.     

Mate replacement in experimentally widowed collared flycatchers (Ficedula albicollis): determinants and outcomes

There is increasing evidence that sexual selection may be intense even in socially monogamous birds, resulting from both mate choice and sperm competition. We studied these two modes of sexual selection experimentally by removing paired male collared flycatchers, Ficedula albicollis, from their mates for 2 days and investigating the factors that influenced the likelihood of a replacement male appearing and how the removals influenced paternity. Replacement males (usually neighbouring males) appeared at 81% (n = 37) of nests where males were removed. The likelihood of this appearance was unaffected by the probable reproductive value of the female's clutch to the replacing male. A replacement was, however, less likely when the original male had a large forehead patch, a trait previously shown to be subject to sexual selection in this population. Experimental removal of males increased the level of sperm competition: 74% of experimental broods were multiply sired, compared to 29% of unmanipulated broods in a previous study. Only two factors predicted how paternity was shared between males: removed males fathered more young if removed closer to laying, and if they had larger forehead patches. The former result is consistent with last-male sperm precedence determining paternity, whereas the latter adds to other evidence that forehead patch size is the target of female preference in this species. Our results suggest that females exert some control over male replacement, and also that they may influence the fertilisation success of males by behavioural means. Received: 15 July 1998 / Received in revised form: 16 March 1999 / Accepted: 28 March 1999     

When females should contest for food – testing hypotheses about resource density, distribution, size, and quality with Hanuman langurs (Presbytis entellus)

Predictions of ecological models on female social relationships (van Schaik 1989) and their links with food distribution and the potential competitive regime are used to analyze the feeding and spatial behavior, and resource density, size, distribution, and quality in a forest population of Hanuman langurs (Presbytis entellus). In contrast to other populations, and assumptions on folivorous primates, the females of this population exhibit a linear dominance hierarchy. The langurs concentrated their feeding on three key resources with a low density and clumped distribution. Two out of the three key resources contained significantly higher levels of extractable protein and soluble sugar than other food plants, indicating high spatial variability of food quality. Even the mature leaves of the most preferred food plant were about twice as nutritious as those from other food plants. Group spread was small and only a single high-quality resource was used at a time. Finally, even rich resources could accommodate only a subset of a group. These findings fit predictions made for the prevalence of within-group contest competition. Given the observed food distribution and phytochemical heterogeneity of mature foliage, even females of folivorous species should contest for food. The effect of female dominance rank on size and composition of feeding parties also agrees with this prediction. A comparison with data from another forest population, where female dominance relations are weakly developed, revealed a clear-cut difference in the use and abundance of resources. It is argued that between-population differences in female social relationships within a species may be viewed as adaptive responses to local habitat conditions. Received: 1 August 1997 / Accepted after revision: 7 December 1997     

Sperm allocation in an uncertain world

Models of optimal sperm allocation are constructed using stochastic dynamic programming techniques, yielding predictions about sperm allocation when males mate sequentially, breeding time is finite, sperm stores are limited and females vary in quality. The models suggest that uncertainty of future reproductive opportunities should favour withholding of sperm, so that males tend to allocate less (for a given level of stored sperm) earlier in the breeding season. This effect is more pronounced the greater the variance in female quality. We also show that while allocation will be influenced by mate value, it is not necessarily optimal to allocate preferentially to high-quality females, since the benefits of a higher-quality mate may be offset by increased risk of rejection of sperm or higher sperm competition. The relationship between mate quality and level of allocation will depend strongly on the amount of remaining stored sperm, with males whose supplies are depleted being more likely to favour lower-quality partners. Received: 12 September 1997 / Accepted after revision: 28 June 1998