Dynamics of threatened goldenseal populations and implications for recovery

Goldenseal (Hydrastis canadensis) is a North American perennial clonal herb highly prized for its medicinal value. It is threatened at the northern range limit with only 20 populations known in Canada. To assist recovery planning, 13 populations were sampled to model dynamics. The fate of all ramets in one square-meter was monitored from 1998 to 2001. Transition matrices were built for 2000-2001, using three stage classes based on size and reproductive status. A six-stage pooled matrix, separating established ramets from newly produced ramets, was also constructed. Recruitment by seed was not observed and therefore excluded. The average population growth rate (λ) was 1.062 ± 0.053, which did not significantly differ from the equilibrium value (1.0) suggesting that the northern population is stationary. However, growth rates among population samples varied largely and had wide confidence intervals. Populations with λ-values less than or close to 1.0 require environmental change to increase. Recovery of goldenseal, and possibly other woodland perennials at risk, requires intervention aimed at population size augmentation, habitat optimization, and targeted dispersal.     

Comment on "A hydrogen-rich early Earth atmosphere"

Tian et al. (Reports, 13 May 2005, p. 1014) proposed a hydrogen-rich early atmosphere with slow hydrogen escape from a cold thermosphere. However, their model neglects the ultraviolet absorption of all gases other than H2. The model also neglects Earth's magnetic field, which affects the temperature and density of ions and promotes nonthermal escape of neutral hydrogen.     

Faunal use of bluegum ( Eucalyptus globulus ) plantations in southwestern Australia

We examined the faunal use of Eucalyptus globulus plantations in southern Western Australia, and compared use of remnant vegetation, agricultural land and plantations in different positions relative to large tracts of remnant vegetation. In general, faunal use of plantations is less than in comparison with adjacent remnant vegetation, but more than in open pasture. For all faunal groups there were almost twice as many species recorded in the native vegetation than in any site in the plantations or on agricultural land and they were in greater abundance. Faunal use of plantation edges and interiors did not show consistent patterns. Generally, edges next to remnants were most frequently used, but individual species showed a wide range of patterns of use across the various habitat types studied. More species of bird identified as being “at risk” were found in plantation edges than in interiors. Adjacency to remnant vegetation increased plantation use by some species, but the overall differences between isolated plantations and those adjacent to remnant vegetation were relatively small. We conclude that plantations provide some value in terms of habitat for some species, including some of conservation concern, but that this value is limited by the lack of habitat complexity in the intensively-managed plantations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Trends in the activity levels of forest-dwelling vertebrate fauna against a background of intensive baiting for foxes

The relative activity of ground-dwelling vertebrates was monitored using tracks in sand plots for 10 consecutive years across three nearby study areas in south-eastern mainland Australia. Two areas were subject to intensive 1080 poison baiting for foxes, while one unbaited area acted as a control. At the two 1080 baited sites there was a demonstrable decline in the reporting rate of fox tracks, while that of feral cats also declined concomitantly. In contrast, the reporting rate of wild dog tracks did not change. At the unbaited site the reporting rate of wild dog tracks increased slightly, while that of foxes remained stable and that of feral cats declined slightly. Prevailing ecological theory would suggest that in systems where larger predators are reduced in activity or abundance, smaller predators should increase. This was not the case in our work. Instead, while the larger sized fox has decreased at baited sites, the smaller sized cat has declined at a regional scale, in all likelihood against a backdrop of long-term drought and diminished prey resources. Among the native omnivorous mammals that ordinarily fall prey to foxes, bandicoots, brushtail possums and lyrebirds increased in activity against a background of diminishing fox activity, although these effects were not uniform at both baited sites. In contrast, at the study area where foxes were not baited, the activity of bandicoots, brushtail possums and lyrebirds either did not change or diminished. Trends in the activity levels of these animals, particularly bandicoots, may have been moderated in part by prevailing rainfall conditions. Otherwise, habitat complexity may also help regulate activity patterns. Land managers concerned with preserving and enhancing biodiversity need to not only focus on the baiting of introduced predators but also be mindful of habitat condition and the effects of climate.     

Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth

The low O2 content of the Archean atmosphere implies that methane should have been present at levels approximately 10(2) to 10(3) parts per million volume (ppmv) (compared with 1.7 ppmv today) given a plausible biogenic source. CH4 is favored as the greenhouse gas that countered the lower luminosity of the early Sun. But abundant CH4 implies that hydrogen escapes to space (upward arrow space) orders of magnitude faster than today. Such reductant loss oxidizes the Earth. Photosynthesis splits water into O2 and H, and methanogenesis transfers the H into CH4. Hydrogen escape after CH4 photolysis, therefore, causes a net gain of oxygen [CO2 + 2H2O --> CH4 + 2O2 --> CO2 + O2 + 4H(upward arrow space)]. Expected irreversible oxidation (approximately 10(12) to 10(13) moles oxygen per year) may help explain how Earth's surface environment became irreversibly oxidized.     

Pests of Deepwater Rice and their Management

Deepwater rice has a distinctive pest complex due to prolonged deep flooding, extended growth duration and a complex environment. Flooding smothers weeds, prevents population buildups of some pests and diseases, and stimulates new growth which may compensate for early damage. Major pests are adapted to these aquatic conditions and exploit the succulent growth and mild weather extremes of this period.In Asia, yellow stem borer causes widespread damage by producing a loss of bearing stems, and lighter or empty panicles. No appropriate measures are known and control of this major pest is a daunting challenge. Stem nematode severely damages rice in several areas but varietal resistance is effective. Rats and hispa beetle are also injurious and many lesser pests are known. In West Africa's smaller Deepwater rice area, stem borers, leafeaters, birds and rats are damaging but their effect on yield is obscure. Farmers commonly employ cultural control methods, and insecticides are used in some areas but diseases are not treated. Pesticide use is restricted by application difficulties, contamination concerns and the low value of the crop. In Asia and Africa wild rices, grasses and sedges compete fiercely with rice before flooding; herbicides are not generally used but many farmers hand weed though the extent of yield loss is poorly understood.Pest management research in deepwater rice is difficult because of the nature of the agroecosystem. Most research has been carried out in Asia but the volume has seriously declined over the last decade.     

Prediction of the spatial distribution and relative abundance of ground-dwelling mammals using remote sensing imagery and simulation models

We present an approach that allows current, retrospective and future relative abundances of mammal species to be predicted across landscapes. A spatial generalized regression model of species relative abundance based on habitat quality and time since disturbance was combined with coverages of the spatial distribution of habitat quality derived from a simulation model which predicts the historical and future spatial arrangement of forest habitat. The strength of this approach is that the input habitat data can be derived as part of a standard forest inventory mapping program with the addition of high spatial resolution remote sensing imagery. Furthermore, it operates at the scale used for wildlife management in Australia, which makes it widely applicable. To demonstrate the approach we use data collected over 20 years on the long-nosed potoroo (Potorous tridactylus) and the large wallabies (red-necked wallaby, Macropus rufogriseus, and swamp wallaby, Wallabia bicolor) and their habitats following wildfire. Results indicate the relative abundance of the potoroo has increased, from initially sparse numbers of less than 0.5 % of plot-night occurrences to close to 3% approximately twenty years after a major fire event. The large wallabies by contrast decreased in relative abundance from about 20% since the major fire event. Presently the relative abundance of large wallabies was modelled at 2% of plot-nights with tracks which was very low. Predictions of future relative abundance without additional disturbance were low, with the region likely to be unsuitable for the species in the next 5 years. These models offer tools for investigating the current and historical abundances of key species which can provide data to forest managers for wildlife management thereby translating current scientific understanding into tools suitable for every-day use by forest managers. This revised version was published online in July 2006 with corrections to the Cover Date.