Litter decomposition of six tree species on indigenous agroforestry farms in south-eastern Ethiopia in relation to litterfall carbon inputs and modelled soil respiration

The indigenous agroforestry systems practised by smallholders in south-eastern Ethiopia have high biodiversity and productivity. However, little is known about their carbon (C) inputs and outputs. We carried out a 1-year litterbag study to determine leaf litter decomposition k constants for six woody species common to these agroforestry systems. The k values were then used to calculate the decomposition C losses from measured litterfall C fluxes and the results compared to modelled soil respiration (Rs) C losses. Litterbag weight loss at the end of the year was 100% or nearly so, k values 2.582-6.108 (yr(-1)) and half-life 41-112 days. k values were significantly (p = 0.023) correlated with litter N contents, nearly so with C/N ratios (p = 0.053), but not with other nutrients (Ca, Mg and K), and negatively correlated with temperature (p = 0.080). Using species, farm elevation, temperature and litter quality as predictors, partial least squares regression explained 48% of the variation in k. Depending on species, estimated decomposition C losses from litterfall were 18 to 58% lower than annual litterfall C inputs. Using a heterotrophic respiration (Rh) to Rs ratio of 0.5, modelled Rh C losses were 89 to 238% of litterfall decomposition C losses estimated using k values. However, using an Rh/Rs ratio of 0.27, which is appropriate for tropical humid forests, Rh C losses were 11 to 138% of estimated litterfall decomposition C losses. Our decomposition and soil respiration estimates indicate that litterfall is sufficient to maintain soil organic C contents and thereby the soil fertility of these unique agroforestry systems.Peer reviewe

AquaCrop-Simulated Response of Sorghum Biomass and Grain Yield to Biochar Amendment in South Sudan

The dependency on rainfed agriculture and weak adaptability of the agricultural sector to climate change threaten food security in Sub-Saharan Africa (SSA). Biochar has widely been touted as a relatively easy means of increasing the soil water storage capacity of soils and thereby improving or maintaining crop yields. In this study we simulated the effect of biochar amendment on sorghum aboveground biomass and grain yield at a site in South Sudan. We used the model AquaCrop parameterized using site, soil, and cropping management data from a field experiment carried out at the site in 2011 and 2012, which were both wet years. Changes in soil hydraulic properties due to biochar were based on a published meta-analysis study. In order to investigate whether the response to biochar differed in dry years, simulations were also carried out for 1990, which was the driest year during the period 1979–2014. Measured and modelled biomass and yields with and without biochar for 2011 and 2012 were compared. Simulated and measured yields depended on growing season rainfall and distribution. The simulations showed that biochar amendment had an effect on rooting zone soil water content and sorghum biomass and grain yield in 1990, but not in 2011 and 2012. In view of expected climate change, the results have important implications for sorghum production and the potential use of biochar in SSA. Given the limited response of grain yield to biochar shown in our simulations, careful selection of sorghum variety and cultivar and consideration of planting date may be a more effective means of improving yields than applying biochar

Whedon’s great glass elevator: space, liminality and intertext in The Cabin in the Woods

This paper,published in the January 2014 edition of Slayage: The Journal of the Whedon Studies Association [36], explores Joss Whedon and Drew Goddard’s 2012 meta-horror film The Cabin in the Woods in terms of conceptions of space and intertextuality. The film has been consciously positioned by its authors as a critical evaluation with a distinct purpose; more than passive commentary or criticism, Whedon maintains that it is an attempt to “revitalize the horror movie genre” which has suffered a “devolution . . . into torture porn and into a long series of sadistic comeuppances” (Utichi n.pag). Congruent to this, The Cabin in the Woods not only provides points of reference for a myriad of supernaturally based horror movies, but in the process attempts an evisceration (in both diegetic and metaphorical terms) of said cinematic universes. In this regard, theoretical approaches of Foucault and Kristeva are used to conceptualise how the liminal spaces of the film function to explicate representations of horror via Whedon’s “signature intertextuality” (Lavery & Burkhead ix), which serve to reveal “layers of meaning or relationships to a large number of fragmentary possible worlds ... that are juxtaposed or superimposed upon each other and contain undesirable bodies” (Genocchio 1995). It is hence shown that, when read in spatial terms, the intertexts within The Cabin in the Woods become “monstrous hybrids that resist containment”, which literally make the text a “living hell on earth” (Kristeva Desire 66). Ultimately, by conceptualizing the processes that inform Whedon and Goddard’s critique, this reading informs as to whether The Cabin in the Woods succeeds in its stated ambitions of the reinvention and re-invigoration of the horror genre

Whedon’s great glass elevator: space and intertextuality in The Cabin in the Woods

This paper explores Joss Whedon’s 2012 'meta-horror' The Cabin in the Woods in terms of conceptions of space. Via the theoretical approaches of Foucault and Kristeva, the film’s elevator sequence, and the multitude of monsters from the horror pantheon contained within, is used to conceptualise how the liminal spaces of the film function in explicating representations of horror and Whedon's 'signature intertextuality'

Risk Factors for Cryptococcus gattii Infection, British Columbia, Canada

To determine whether particular environmental, medical, or behavioral risk factors existed among Cryptcoccus gattii–infected persons compared with the general population, we conducted a sex-matched case−control study on a subset of case-patients in British Columbia (1999–2001). Exposures and underlying medical conditions among all case-patients (1999–2007) were also compared with results of provincial population–based surveys and studies. In case−control analyses, oral steroids (matched odds ratio [MOR] 8.11, 95% confidence interval [CI] 1.74–37.80), pneumonia (MOR 2.71, 95% CI 1.05–6.98), and other lung conditions (MOR 3.21, 95% CI 1.08–9.52) were associated with infection. In population comparisons, case-patients were more likely to be >50 years of age (p<0.001), current smokers (p<0.001), infected with HIV (p<0.001), or have a history of invasive cancer (p<0.001). Although C. gattii is commonly believed to infect persons with apparently healthy immune systems, several immunosuppressive and pulmonary conditions seem to be risk factors

Response of Soil Surface Respiration to Storm and Ips typographus (L.) Disturbance in Boreal Norway Spruce Stands

Disturbances such as storm events and bark beetle outbreaks can have a major influence on forest soil carbon (C) cycling. Both autotrophic and heterotrophic soil respiration may be affected by the increase in tree mortality. We studied the effect of a storm in 2010 followed by an outbreak of the European spruce bark beetle (Ips typographus L.) on the soil surface respiration (respiration by soil and ground vegetation) at two Norway spruce (Picea abies L.) dominated sites in southeastern Finland. Soil surface respiration, soil temperature, and soil moisture were measured in three types of plots—living trees (undisturbed), storm-felled trees, and standing dead trees killed by I. typographus—during the summer–autumn period for three years (2015–2017). Measurements at storm-felled tree plots were separated into dead tree detritus-covered (under storm-felled trees) and open-vegetated (on open areas) microsites. The soil surface total respiration for 2017 was separated into its autotrophic and heterotrophic components using trenching. The soil surface total respiration rates at the disturbed plots were 64%–82% of those at the living tree plots at one site and were due to a decrease in autotrophic respiration, but there was no clear difference in soil surface total respiration between the plots at the other site, due to shifts in either autotrophic or heterotrophic respiration. The soil surface respiration rates were related to plot basal area (living and all trees), as well as to soil temperature and soil moisture. As storm and bark beetle disturbances are predicted to become more common in the future, their effects on forest ecosystem C cycling and CO2 fluxes will therefore become increasingly important