Partitioning of rainfall in a eucalypt forest and pine plantation in southeastern australia: II stemflow and factors affecting stemflow in a dry sclerophyll eucalypt forest and a pinus radiata plantation

Stemflow of a dry sclerophyll eucalypt forest and a nearby Pinus radiata plantation was studied on a rainfall event basis. The stemflow yields of the forests are quantified, compared, and presented on an annual basis for four years. Yields of the individual eucalypt species are compared and the tree characteristics responsible for the yield differences are discussed. The influence of event size, type, and season on stemflow are also shown. Rainfall angle is shown to have a significant effect on stemflow yield.     

An electrically powered binary star?

We propose a model for stellar binary systems consisting of a magnetic and a non-magnetic white dwarf pair which is powered principally by electrical energy. In our model the luminosity is caused by resistive heating of the stellar atmospheres arising from induced currents driven within the binary. This process is reminiscent of the Jupiter–Io system, but greatly increased in power because of the larger companion and stronger magnetic field of the primary. Electrical power is an alternative stellar luminosity source, following on from nuclear fusion and accretion. We find that this source of heating is sufficient to account for the observed X-ray luminosity of the 9.5-min binary RX J1914+24, and provides an explanation for its puzzling characteristics.     

Relationship between dynamics of litterfall and riparian plant species in a tropical stream

We investigated the dynamics of organic matter and type of detritus in a riparian zone of the Atlantic Rain Forest domain, and specifically determined the inputs and stock of detritus contributed by plant species, and their relationship to temperature and precipitation. Our hypotheses tested were: (1) the species composition of riparian vegetation influences the amount and type of detritus delivered to a stream in an Atlantic Rain Forest, and (2) the dynamics of litterfall in the riparian zone is influenced by climate factors. The plant community was formed principally by pioneer and early successional species such as Apuleia leiocarpa, Erytrina velutina, Erytrina verna, Eucalyptus torelliana, Ficus glabra, Ficus insipida, Guarea guidonea, Guarea guidonia, Maprounea guianensis and Psidium guajava. There was a large number of G. guidonea (318 individuals/ha), followed by Cupania oblongifolia (91), Trichilia pallida (52), Piptadenia gonoacantha (26) and E. torelliana (14). G. guidonea contributed >50% of the total litterfall; however, some species which were present in high density in the plant community and did not yield significant biomass, indicating that detritus production was based on the contribution of a few species. We found 697, 856 and 804 g/m²/year from vertical, terrestrial, and lateral inputs, respectively, whereas to the annual benthic standing stock was 3257 g/m². Detritus was formed by leaves (60%), branches (32%), reproductive parts (3%), and unidentifiable fragments of organic-matter (5%). Inputs and benthic stock were markedly seasonal, with an increase of leaf litter during the dry season. Our results indicate that litterfall dynamics is basically composed of a few species that contribute with higher values of biomass. Moreover, ecological characteristics together with environmental factors can be viewed as the principal factors determining the energy balance of riparian ecosystems. The biological implications of the dynamics of organic matter have high importance for the maintenance and restoration of riparian zones. However, the amount of litterfall required to maintain the balance of the riparian community remains unclear in the tropical zone.