Relationships between carbon turnover and bioavailable energy fluxes in two temperate forest soils

Recent research has shown that the broad empirical relationships used in many ecosystem models to predict carbon turnover and stabilization in soils can fail to capture differences across vegetation types or climates. Theoretically, because energy flow is fundamental to the function of decomposer organisms and ecosystems, energetics could provide complimentary fundamental constraints on soil C dynamics. Often, however, C is considered as a surrogate for energy in studies of detrital decay and C turnover in soil. Bomb calorimetry has long been used to measure stored energy in organic matter, but in detritus not all of the energy is bioavailable. Here I outline an approach to quantify the flux of bioavailable energy dissipated by resident heterotrophic communities in soil organic horizons in situ. I used the principle of energy balance together with a biogeochemical process model parameterized through calorimetric analysis of field samples. I also tested relationships between C and energy across samples of forest detritus (foliar and fine root litter, well‐decayed Oea material, and woody debris), across decay stages, and between a deciduous and coniferous forest at the Harvard Forest, MA, USA. As a first approximation, energy and C concentrations were closely related (within ca. 10%), as were ratios of heterotrophic energy dissipation to C mineralization across types of detritus (within 16%). Differences in energy content and energy : C ratios were measurable in forest detritus (particularly woody vs nonwoody), but did not vary reliably enough between forest types or through detrital stages to indicate that soil C models could be improved by including energetics. Model results indicated that there are strong similarities in energy flows and storage in the O horizons of the contrasting forest types studied at this location. Future research could focus on broader patterns across climates or biomes.     

Patterns of territory settlement and consequences for breeding success in the Northern Wheatear Oenanthe oenanthe

We examined the pattern of territory settlement and its consequences for breeding success in the Northern Wheatear Oenanthe oenanthe on Bardsey Island, Wales, during the breeding seasons of 1991-93. Males returned earlier than females, and older males returned earlier than first-year breeders. Although their boundaries shifted between years, the general location of territories was consistent during the three-year study. There was a high degree of fidelity to area and territory between years for both sexes. The order of territory settlement, from which a territory rank was calculated, was highly consistent for males between years irrespective of individual settlement patterns and territory fidelity. Patterns of territory settlement were less predictable for females, although there was a significant correlation between the mean territory ranks of paired males and females. There was a male-biased sex ratio in each year, and between 5% and 26% of males remained unpaired throughout the breeding season. Male mating status and breeding success were dependent on arrival date, territory rank and breeding density. Early-arriving, usually older, males were able to settle on territories first and were more likely to pair, while later-arriving individuals were more likely to remain unmated. These effects were consistent between years, and consequently territories could be classified as either preferred (accounting for proportionately more breeding attempts) or non-preferred. Territory quality as opposed to individual quality appeared to explain much of the variation in breeding success, and both sexes benefited by breeding on preferred territories through enhanced breeding success and an increased probability that their offspring would be recruited to the population.     

A tyrannosaur jaw bitten by a confamilial: scavenging or fatal agonism?

Bell, P.R. & Currie, P.J. 2009: A tyrannosaur jaw bitten by a confamilial: scavenging or fatal agonism?. Lethaia, Vol. 43, pp. 278–281. A partial dentary of an adult tyrannosaur from the Dinosaur Park Formation of Alberta, Canada, preserves the embedded tooth of another tyrannosaur within the bone. The specimen’s incompleteness precludes generic identification of either the jaw or the embedded tooth, although Gorgosaurus and/or Daspletosaurus are most likely given the stratigraphic position. The absence of healing around the lesion indicates the bite took place either post‐mortem or within weeks prior to the death of this animal. A post‐mortem bite can be explained by confamilial or cannibalistic scavenging. Alternatively, the bite would represent a perimortem instance of intrafamilial aggression that may have resulted in the death of that animal. An estimated 6053N of bite force was required to produce the bite mark. This specimen provides the best evidence for aggressive peri‐ or post‐mortem confamilial interaction among tyrannosaurs and corroborates previous studies based on inferred tooth marks. □Alberta, behaviour, Campanian, Cretaceous, Dinosaur Park Formation, Theropoda, Tyrannosauridae.     

An integrative phylogenetic and extrapolatory approach to the reconstruction of dromaeosaur (Theropoda: Eumaniraptora) shoulder musculature

Dromaeosauridae is the sister taxon of the Avialae; thus, an investigation of dromaeosaur shoulder girdle musculature and forelimb function provides substantial information regarding changes in the size and performance of the theropod shoulder girdle musculature leading to avian powered flight. Twenty-two shoulder girdle muscles were reconstructed for the dromaeosaurid shoulder apparatus, based on phylogenetic inference, which involves the comparison of lepidosaurian, crocodilian and avian musculature, and extrapolatory inference, which involves a secondary comparison with functional analogues of theropods. In addition to these comparative methodologies, osteological correlates of shoulder musculature preserved in eumaniraptorans are identified, and comparisons with those of extant archosaurs allow these muscles to be definitively inferred in dromaeosaurids. This muscle reconstruction provides a foundation for subsequent investigation of differences in muscular attachment and function, based on scapulocoracoid morphology, across the theropod lineage leading to birds.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 146 , 301–344.     

Motoneurone Dysfunction in Patients with Hemiplegie Atrophy

THE nature of the mechanism responsible for the wasting of muscles in patients after lesions of the upper moto-neurone has been the subject of many studies^1,2 and various possibilities are summarized in Fig. 1. The simplest mechanism would be disuse alone; but atrophy might also result from disturbed blood flow in muscles of paralysed limbs or from a secondary arthritis. Another possibility is that an upper moto-neurone lesion deprives muscle of a trophic influence which is normally exerted, through an unspecified route, by the pre-central or postcentral gyrus. Finally, the upper motoneurone lesion may cause secondary changes in lower motoneurones which, in turn, affect muscles. The most widely held opinion is that wasting results from disuse only³, but we have findings which demonstrate that this supposition is incorrect. Instead it seems probable that the most important single factor in the genesis of atrophy is denervation of muscle fibres secondary to disturbed lower motoneurone function.     

Habitat change and woodland birds in Britain: implications for management and future research

There is increasing evidence that changes in habitat structure in the form of reduced understorey and loss of open habitats, both probably a result of increases in shading and deer browsing, may be responsible for causing recent changes in the composition of breeding bird communities in many lowland British woods and forests. In contrast, management of upland coniferous forests may prevent the attainment of mature and old-growth structures which would benefit community development in these new ecosystems. We suggest that the key challenge for woodland conservation policy is to create larger areas of both young-growth and old-growth habitat. These objectives need not necessarily conflict with each other, or with other multipurpose forestry objectives, provided that they inform strategic plans and are targeted at appropriate locations and scales. In the lowlands, the current large stock of middle-aged, often unmanaged and species-poor woodland provides an opportunity to restore or create new woodland habitats of high biodiversity value. The development of woodfuel markets may effectively increase the amount of young-growth but it is unclear exactly what habitat structures might be created. In the uplands, allowing more natural development of native woodland in mosaics with other habitats may provide opportunities for both old- and young-growth species. For the foreseeable future, deer impacts will continue to be widespread and probably increasingly severe in many areas. In view of the uncertainty about the implications of climate change for woodland ecosystems, a strong case can be made for attempting to buffer valued wildlife communities against damaging effects by creating and maintaining high structural diversity at a range of scales and increasing the area of woodland.