Uncertainties in climate change prediction and modelling

As models become increasingly complex and integrated, uncertainty among model parameters, variables and processes become critical for evaluating model outcomes and predictions. A framework for understanding uncertainty in climate modelling has been developed by the IPCC and EEA which provides a framework for discussion of uncertainty in models in general. Here we report on a review of this framework along with the results of a survey of sources of uncertainty in livestock and grassland models. Along with the identification of key sources of uncertainty in livestock and grassland modelling, the survey highlighted the need for a development of a common typology for uncertainty. When collaborating across traditionally separate research fields, or when communicating with stakeholders, differences in understanding, interpretation or emphasis can cause confusion. Further work in MACSUR should focus on improving model intercomparison methods to better understand model uncertainties, and improve availability of high quality datasets which can reduce model uncertainties

The effect of ungulate grazing on a small mammal community in southeastern Botswana

Ungulates can reduce the quantity of food available for other herbivores in general or reduce the available cover for small mammals in particular. On the other hand, browsing and grazing may facilitate foraging by other mammals if the quality and palatability of young re-sprouting tissue is high. An exclosure experiment was set up in Mokolodi Nature Reserve, Botswana, to study ecological effects of large herbivores on the small mammal community. Specifically, we attempted to answer the following questions: 1) are population sizes and community composition of small rodents affected by the exclusion of large herbivores?; 2) if so, what changes in the environment caused by the exclusion of large herbivores are related to changes in small mammal populations?; 3) in what way do such changes in the environment affect small mammals? The populations were significantly larger in the exclosures than in the control areas. A higher number of species was also found in the exclosures. It seems that the smaller populations of small mammals in areas with large herbivores are a result of a reduction in vegetation cover. In general, the exclosures had a higher grass cover than their paired controls. This same relation also held for percentage cover of litter and dead grass.Keywords: plant-herbivore interactions, exclosures, mark–recapture, grazing impact

Temporal and spatial influences incur reconfiguration of Arctic heathland soil bacterial community structure

Microbial responses to Arctic climate change could radically alter the stability of major stores of soil carbon. However, the sensitivity of plot-scale experiments simulating climate change effects on Arctic heathland soils to potential confounding effects of spatial and temporal changes in soil microbial communities is unknown. Here, the variation in heathland soil bacterial communities at two survey sites in Sweden between spring and summer 2013 and at scales between 0–1 m and, 1–100 m and between sites (> 100 m) were investigated in parallel using 16S rRNA gene T-RFLP and amplicon sequencing. T-RFLP did not reveal spatial structuring of communities at scales < 100 m in any site or season. However, temporal changes were striking. Amplicon sequencing corroborated shifts from r- to K-selected taxon-dominated communities, influencing in silico predictions of functional potential. Network analyses reveal temporal keystone taxa, with a spring betaproteobacterial sub-network centred upon a Burkholderia operational taxonomic unit (OTU) and a reconfiguration to a summer sub-network centred upon an alphaproteobacterial OTU. Although spatial structuring effects may not confound comparison between plot-scale treatments, temporal change is a significant influence. Moreover, the prominence of two temporally exclusive keystone taxa suggests that the stability of Arctic heathland soil bacterial communities could be disproportionally influenced by seasonal perturbations affecting individual taxa