The positive net radiative greenhouse gas forcing of increasing methane emissions from a thawing boreal forest‐wetland landscape

At the southern margin of permafrost in North America, climate change causes widespread permafrost thaw. In boreal lowlands, thawing forested permafrost peat plateaus (‘forest’) lead to expansion of permafrost‐free wetlands (‘wetland’). Expanding wetland area with saturated and warmer organic soils is expected to increase landscape methane (CH₄) emissions. Here, we quantify the thaw‐induced increase in CH₄ emissions for a boreal forest‐wetland landscape in the southern Taiga Plains, Canada, and evaluate its impact on net radiative forcing relative to potential long‐term net carbon dioxide (CO₂) exchange. Using nested wetland and landscape eddy covariance net CH₄ flux measurements in combination with flux footprint modeling, we find that landscape CH₄ emissions increase with increasing wetland‐to‐forest ratio. Landscape CH₄ emissions are most sensitive to this ratio during peak emission periods, when wetland soils are up to 10 °C warmer than forest soils. The cumulative growing season (May–October) wetland CH₄ emission of ~13 g CH₄ m^?2 is the dominating contribution to the landscape CH₄ emission of ~7 g CH₄ m^?2. In contrast, forest contributions to landscape CH₄ emissions appear to be negligible. The rapid wetland expansion of 0.26 ± 0.05% yr^?1 in this region causes an estimated growing season increase of 0.034 ± 0.007 g CH₄ m^?2 yr^?1 in landscape CH₄ emissions. A long‐term net CO₂ uptake of >200 g CO₂ m^?2 yr^?1 is required to offset the positive radiative forcing of increasing CH₄ emissions until the end of the 21st century as indicated by an atmospheric CH₄ and CO₂ concentration model. However, long‐term apparent carbon accumulation rates in similar boreal forest‐wetland landscapes and eddy covariance landscape net CO₂ flux measurements suggest a long‐term net CO₂ uptake between 49 and 157 g CO₂ m^?2 yr^?1. Thus, thaw‐induced CH₄ emission increases likely exert a positive net radiative greenhouse gas forcing through the 21st century.     

Subtractive hybridization magnetic bead capture: a new technique for the recovery of full-length ORFs from the metagenome

A new method for the recovery of full-length open reading frames from metagenomic nucleic acid samples is reported. This technique, based on subtractive hybridization magnetic bead capture technology, has the potential to access multiple gene variants from a single amplification reaction. It is now widely accepted that classical microbiological methods provide only limited access to the true microbial biodiversity (less than 1%). The desire to access a higher proportion of the metagenome has led to the development of efficient environmental nucleic acid extraction technologies and to a range of sequence-dependent and sequence-independent gene discovery techniques. These methods avoid many of the limitations of culture-dependent gene targeting.     

Movement,activity and hunting behaviour of leopards in the Cederberg mountains,South Africa

Few data are available on the behaviour of leopards in the absence of competing large predators and human impact, both of which are believed to influence leopard activity and movements. Remote camera traps and global positioning system (GPS) collars were used to quantify leopard activity in the Cederberg Mountains, seasonal and sexual differences in their movements, and determine whether nocturnal hunting success was related to lunar activity. Seventy‐seven per cent of camera‐trap photographs were at night, with a strong male bias (69%) in captures. Daily displacement using one location per day suggested that males moved significantly further than females. However, multiple locations (≥6 per day) showed no difference because males moved in a more linear fashion, but not further each day, than females. In the Cederberg Mountains, an open rocky habitat with low human impact and no competing predators, leopards were predominantly nocturnal, mainly hunting diurnal prey species. Hunting success was low: leopards travelled long distances between kills, with nocturnal hunting success higher on darker nights.