Restoration of rivers used for timber floating: effects on riparian plant diversity.

Fluvial processes such as flooding and sediment deposition play a crucial role in structuring riparian plant communities. In rivers throughout the world, these processes have been altered by channelization and other anthropogenic stresses. Yet despite increasing awareness of the need to restore natural flow regimes for the preservation of riparian biodiversity, few studies have examined the effects of river restoration on riparian ecosystems. In this study, we examined the effects of restoration in the Ume River system, northern Sweden, where tributaries were channelized to facilitate timber floating in the 19th and early 20th centuries. Restoration at these sites involved the use of heavy machinery to replace instream boulders and remove floatway structures that had previously lined stream banks and cut off secondary channels. We compared riparian plant communities along channelized stream reaches with those along reaches that had been restored 3-10 years prior to observation. Species richness and evenness were significantly increased at restored sites, as were floodplain inundation frequencies. These findings demonstrate how river restoration and associated changes in fluvial disturbance regimes can enhance riparian biodiversity. Given that riparian ecosystems tend to support a disproportionate share of regional species pools, these findings have potentially broad implications for biodiversity conservation at regional or landscape scales.     

Incest avoidance and bonding between siblings in gerbils

Summary Social and sexual preferences for siblings versus non-siblings have been investigated in Mongolian gerbils (Meriones unguiculatus) in a series of laboratory and outdoor enclosure (100 m²) studies. When first social contact took place at pairing in adulthood full siblings and nonsiblings did not differ with respect to onset of reproduction. Correspondingly, both siblings and non-siblings paired at weaning age had a delayed onset of reproduction. Thus, no effect could be established in either case, related to the individuals' relatedness, but the importance of social exposure was clear. Non-siblings paired when 2 months old had a delayed onset of reproduction, which did not differ statistically from the onset in siblings, raised together, and housed pairwise since the same age. When sexually mature animals were paired at 3 months of age, siblings were found to start reproducing later than non-siblings (Ågren 1981). Following an initial delay in both siblings and nonsiblings paired when 5 months old, all non-sibling pairs reproduced before any sibling pair. At pair formation, at least the females in both groups were known to be sexually immature. These results indicate that for sibling-bonding to occur social exposure may be delayed until the animals are old enough, or somatically developed, to mature sexually. Thus, social exposure before weaning age during the period for primary socialization seem not to be crucial, nor the actual maturational state, sexually, in older females. To study the stability of the social bonds between siblings and non-siblings, animals kept pairwise in the laboratory were released in large outdoor enclosures. Pairs brought together before the age of sexual maturity did not remain stable, whether or not the former cagemates were siblings. Non-sibling pairs formed after this age, which had also reproduced successfully in the laboratory, did remain stable. Social and sexual interactions were studied within and between two mixed-sex sibling groups of four. The sibling groups had the possibility to establish group territories before being exposed to each other. Although the sibling groups remained stable, the females still preferred non-sibling males as sexual partners. However, socially dominant brothers copulated more frequently than subordinant brothers. This rank difference was not evident in non-siblings.     

Urban Geochemistry: A Multimedia and Multielement Survey of a Small Town in Northern Europe

The concentrations and distributions of chemical elements (Ag, Al, As, Au, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Se, Sr, Te, Th, Ti, Tl, U, V, W and Zn) were studied in till, humus and urban soil in Jakobstad, a small town (20,000 inhabitants) in W. Finland. The analyses were performed with ICP-MS after aqua regia leaching of till (n = 37), urban topsoil (n = 32) and subsoil (n = 32), and HNO3 leaching of humus (n = 37). The till and humus samples, collected at the same sites, were divided into urban and rural samples. The urban till was not significantly enriched in metals. In contrast, a majority of the elements occurred in higher concentrations in the urban than the rural humus samples. Statistical and spatial interpretations of the humus data revealed that traffic (Pb, V and Ni), metal industry (Pb, Zn, Bi, Sb and Cr), an abandoned shooting range (Pb and Sb) and other sources contribute to higher metal levels in the urban humus. The urban soil samples were collected at parks, yards, abandoned industrial sites, roadsides, etc. The topsoil samples were enriched in most elements, also by elements not enriched in the urban humus (e.g. Cd). At several sites, the concentrations far exceeded the limit concentrations for contaminated soils in Finland. A large variety of sources were identified or indicated.     

Spermatozoan ultrastructure and spermatogenesis in aplousobranch ascidians,with some phylogenetic considerations

Spermatozoa and some stages of spermatogenesis were studied for four species of aplousobranch ascidians. Spermatozoa of Clavelina lepadiformis (Müller) (family Clavelinidae) are plesiomorphous in that they have apical acrosomal vesicles and a moderately elongated, cylindrical nucleus. The elongated mitochondrion is twisted ea. 11/2 times around the nucleus. In their ultrastructural morphology, C. lepadiformis sperm conform in some respects to the least-derived ascidian sperm, those of the phlebobranch ascidian Ciona intestinalis L.; however, the sperm of Clavelina lepadiformis have two apomorphies not shared with those of Ciona sp.: (1) the mitochondrion of Clavelina lepadiformis is long and spiralled along the entire nucleus rather than being comparatively compact and not at all helical; (2) the mitochondrial cristae are elongated parallel to the long axis of the nucleus, whereas in Ciona sp. sperm the cristae are unmodified. In Distaplia sp., Aplidium sp. and Synoicum pulmonaria (Ellis and Solander) the spermatozoa are more derived and consist of a proximal cylindrical and a distal corkscrew-like part. The mitochondrion in Distaplia sp. and Aplidium sp. contains electron-dense material and extends in a long thread around the nucleus. In S. pulmonaria the mitochondrion surrounds the anterior part of the nucleus in mature spermatozoa, and an elongated, dense structure displaying fine striation is enclosed in the mitochondrion in late spermatids. The sperm ultrastructural morphology observed in this study is consistent with the majority view that clavelinids are closest to the ancestral ascidian but is also consistent with other conclusions, particularly that the Cionidae are closest to the stem ascidian.     

No cost of male mating experience on female reproductive success in the almond moth, <Emphasis Type="BoldItalic">Cadra cautella</Emphasis> (Lepidoptera; Pyralidae)

Male copulation experience may have a profound impact on female reproductive success if male reproductive investment declines over consecutive copulations and if females are unlikely to re-mate. Male reproductive investment is particularly interesting in lepidopterans because males produce dimorphic sperm: a fertilizing (eupyrene) and a non-fertilising (apyrene) sperm. In two experiments, we explored the lifetime reproductive investment of male almond moths, Cadra cautella (also known as Ephestia cautella) and examined its influence on female reproductive success. In the almond moth, females re-mate infrequently and males transfer sperm in a spermatophore. Attached to the spermatophore is a large chitinous process, the function of which is unknown. One group of males were permitted consecutive copulations with virgin females and the amount of sperm and size of the spermatophore transferred were compared for all females. We found that the number of both eupyrene and apyrene sperm per ejaculate decreased with his increased mating frequency, while the size of the spermatophore process decreased dramatically after the male’s first copulation. In a second experiment, we allowed males to mate with females throughout their lives and then compared female fecundity and fertilisation success. We found no obvious decrease in female fecundity and fertilisation success with increased male copulation experience, despite the likely reduction in male gametic investment. We discuss potential explanations for the development of this enlarged and elaborate first spermatophore of male almond moths given that it confers no clear fitness advantage to females.     

Biliary secretion,retention and excretion of five 14C-labelled polychlorinated biphenyls in the rat

Five ¹⁴C-labelled polychlorinated biphenyls: 2,4′,5-trichlorobiphenyl, 2,2′,4,5′-tetrachlorobiphenyl, 2,2′,4,5,5′-pentachlorobiphenyl, 2,2′,3,4,4′-pentachlorobiphenyl and 2,2′,4,4′,5,5′-hexachlorobiphenyl were administered orally to bile-cannulated rats. The activity secreted in the bile, excreted in the feces and the urine was determined. Residues of radioactivity in certain tissues and the carcass were also measured.The trichlorobiphenyl showed the highest absorption (93.8%±5.4) from the gastrointestinal tract and biliary secretion of radioactivity (87.6%±6.1 of the dose). The hexachlorobiphenyl showed the lowest absorption and biliary secretion, 28.2%±1.4 and 18.6%±1.3, respectively. The urinary excretion was low and the radioactive residues in the eviscerated carcasses increased with the chlorine content of the biphenyls.     

In situ anion diffusion experiments using radiotracers

Diffusion experiments in compacted bentonite have been carried out in situ using the borehole laboratory CHEMLAB. The "ordinary" anion iodide and the redox-sensitive pertechnetate ion have been investigated. In spite of strongly reducing groundwater conditions, technetium was found to diffuse mostly unreduced as TcO4-, although in some spots in the compacted clay, the activity was significantly higher, which may be explained by reduction of some TcO4- by iron-containing minerals in the bentonite. The measured concentration profiles in the clay cannot be accommodated by assuming one single diffusion process. The experimental data are modeled assuming two diffusion paths, intralamellar diffusion and diffusion in external water. The apparent diffusivity for the intralamellar diffusion was found to be 8.6 x 10(-11) m2 s(-1) for iodide with a capacity factor of 0.1, while the apparent diffusivity for the diffusion in external water was found to be 5 x 10(-14) m2 s(-1) with alpha=2.26. The corresponding values for Tc were found to be Da= 6 x 10(-11) m2 s(-1), alpha=0.1 and Da= 1 x 10(-13) m2 s(-1), alpha=0.46, respectively. The diffusion constants and capacity factors obtained in this study are in accordance with data from laboratory experiments.