The role of seed limitation and resource availability in the recruitment of native perennial grasses and exotics in a South Australian grassland

Abstract We investigated what factors lead to invasion of exotics or re‐colonization of native perennial grasses in the South Australian mid‐north grasslands. We manipulated 160 experimental quadrats by clipping, irrigation and seed addition and assessed recruitment by exotics in an area dominated by perennial grasses and perennial grass recruitment in an area dominated by exotics. Treatment effects differed with season for exotics: their biomass increased with irrigation in autumn and seed addition in winter. However, in both periods other factors, probably soil properties, also had a strong effect. We detected no perennial grass seedlings in the quadrats over 1 year, possibly due to unsuitable environmental conditions or persistent high competition levels. Under controlled conditions the presence of the invasive annual Avena barbata had a strong negative effect on the recruitment of the native perennial Austrodanthonia caespitosa at any moisture and nutrient availability. Avena also germinated faster and more frequently than Austrodanthonia, especially at low soil moisture. During an imposed drought Austrodanthonia seedlings survived longer in the absence of Avena. The results suggest that annual exotics are highly responsive to resources and can quickly invade areas, while the re‐colonization of invaded areas by native grasses requires a complex (and less likely) rainfall regime.     

Latex content and biomass increase in mycorrhizal guayule (Partheniurn argentatum) under field conditions*

Guayule seedlings were inoculated with two Glomus species in pasteurised soil and grown in the glasshouse without added fertiliser for 8 wk prior to transplanting to the field. The survival rate of transplanted guayule seedlings was increased by inoculation with vesicular arbuscular mycorrhizal fungi compared with uninoculated controls. Inoculated guayule had greater concentrations of Ca, Fe, Mg and Mn at six months of age, and greater concentrations of Ca, Mg, and Zn at 12 months of age than did uninoculated plants. The latex content of both roots and shoots of guayule was greater in inoculated than in uninoculated guayule plants at 12 and 18 months of age. The resin content remained unchanged between treatments irrespective of sampling date.     

The Holy Spirit in the Household: Pentecostalism, Gender, and Neoliberalism in Mozambique

The recent expansion of Pentecostalism and independent churches in Africa has generated growing interest among social scientists. This attention parallels a renewed interest among Africanists on witchcraft and occult activities, also believed by many to be increasing. Some suggest the two trends may be related, but it remains unclear how and why. Drawing on a study of Pentecostalism and health in the city of Chimoio, Mozambique, in 2002–03 that focused on attitudes toward recent social change, we argue that structural adjustment economic reforms have deepened economic inequality and exacerbated household stresses that affect men and women differently. Women increasingly seek spiritual help for reproductive health problems from Pentecostal churches, whereas men disproportionately pay traditional healers to engage "occult" practices to manage misfortune related to employment. The increased resort to both spiritual resources reveals social distress caused by economic adjustment, with important implications for health programs.     

Methanogenic activity and biomass in Holocene permafrost deposits of the Lena Delta, Siberian Arctic and its implication for the global methane budget

Permafrost environments within the Siberian Arctic are natural sources of the climate relevant trace gas methane. In order to improve our understanding of the present and future carbon dynamics in high latitudes, we studied the methane concentration, the quantity and quality of organic matter, and the activity and biomass of the methanogenic community in permafrost deposits. For these investigations a permafrost core of Holocene age was drilled in the Lena Delta (72°22′N, 126°28′E). The organic carbon of the permafrost sediments varied between 0.6% and 4.9% and was characterized by an increasing humification index with permafrost depth. A high CH₄ concentration was found in the upper 4 m of the deposits, which correlates well with the methanogenic activity and archaeal biomass (expressed as PLEL concentration). Even the incubation of core material at −3 and −6°C with and without substrates showed a significant CH₄ production (range: 0.04–0.78 nmol CH₄ h⁻¹ g⁻¹). The results indicated that the methane in Holocene permafrost deposits of the Lena Delta originated from modern methanogenesis by cold‐adapted methanogenic archaea. Microbial generated methane in permafrost sediments is so far an underestimated factor for the future climate development.