Reconstruction of Holocene hydroclimatic variability in subarctic treeline lakes using lake sediment grain-size end-members

Current climate trends are expected to result in the northward expansion of the subarctic treeline leading to changes in vegetation cover and permafrost distribution, as they did during the Holocene Climate Optimum when the treeline was 150 km north of its current position. The impacts of these changes on the region’s hydrology are still poorly understood. The grain-size distributions of treeline lake sediments provide an important proxy related to spring melt conditions that can be used to reconstruct hydroclimatic variability. End-member mixing analysis was used to model depositional end-members in 55 modern lake sediment samples and two sediment cores spanning the mid- to late Holocene collected from above and below the treeline in the central Northwest Territories, Canada. Cold climatic intervals (e.g. ‘Dark Ages Cold Period’, ‘Little Ice Age’) were characterised by an increase in the very coarse silt and the fine sand end-members. This was interpreted to be a response to degradation of vegetation cover and/or permafrost development. We observed increases in fine and coarse silt end-members during warmer climatic intervals (e.g. Medieval Climate Anomaly) and over the past c. 300 yr BP. This pattern is probably the result of extended melt seasons, with greater losses to evaporation and increased infiltration. The most pronounced palaeo-hydroclimatological change over the past c. 8000 yr BP was the abrupt increase in a very coarse silt end-member (mode = 50–200 µm) at c. 6300 yr BP. We interpreted the sedimentological change as an increase in winter precipitation and more energetic spring melt conditions, leading to the spring melt becoming the dominant lacustrine sediment delivery mechanism. These results place modern hydrological changes in a millennial context and show that analysis of temporal changes in the hydroclimatological system can provide insight into the future states of these sensitive subarctic ecosystems

Impairment measures in rheumatic disorders for rehabilitation medicine and allied health care: a systematic review

The objective of this study is to provide a critical overview of available instruments to assess impairments in patients with rheumatic disorders, and to recommend reliable and valid instruments for use in allied health care and rehabilitation medicine. A computer-aided literature search (1982-2004) in several databases was performed to identify studies focusing on the clinimetric properties of instruments designed to assess impairments in function in patients with rheumatic disorders. Data on intra-rater reliability, inter-rater reliability and construct validity were extracted in a standardized way. Explicit criteria were applied for reliability and validity. Results: The search identified a total of 49 instruments to assess impairments in functions in patients with rheumatic disorders; 19 met the criteria for reliability, 22 met the criteria for validity, and 11 out of the 49 appeared to meet the criteria for both reliability and validity. In summary, evidence of both reliability and validity was only found for 11 out of 49 instruments for the assessment of impairments in patients with rheumatic disorders. Only a limited number of the identified instruments for the assessment of impairments is both reliable and valid. Allied health care professionals should be cautious in the selection of measurement instruments to assess their patient