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  • 1. Mårell, A
    et al.
    Hofgaard, A
    Danell, K
    Nutrient dynamics of reindeer forage species along snowmelt gradients at different ecological scales2006In: Basic and Applied Ecology, ISSN 1439-1791, E-ISSN 1618-0089, Vol. 7, no 1, 13-30 p.Article in journal (Refereed)
    Abstract [en]

    Growing season nutrient dynamics of four reindeer forage species (Betula nana, Eriophorum angustifolium, Rumex acetosa and Vaccinium myrtillus) were studied in a mountainous sub-arctic landscape in N Sweden. Changes in nitrogen (N), phosphorus (P) and fibre (ADF) concentrations in [eaves and shoots were analysed (from a reindeer foraging perspective) along four ecological gradients significant to regional and local snowmelt regimes: season, oceanicity, attitude, and snow-patch retreat. N and P concentrations showed marked seasonal variations with peaks occurring from the middle of June to the end of July depending on species and snowmelt progression. The seasonal pattern for ADF concentrations, as well as differences between snowmelt regimes, were less consistent and showed large differences between species. N concentrations increased along snowmelt gradients at small (within snow-patches) and medium (along attitude gradients) spatial scales. Furthermore, variations in N concentrations were temporally and spatially scale-dependent, which underlines the importance of scale for understanding plant nutrient dynamics in sub-arctic and alpine systems, as well for plant-animal interactions. The greatest temporal and spatial differences in nutrient quality were observed early in the season, i.e., at the time of highest nutrient requirements for reindeer. Climate-induced changes of the start and the progress of the growing season may result in significant consequences to the development of calves and subsequently to the population demography of reindeer, mediated through spatial and temporal changes in the distribution of high quality food. These results provide basic knowledge for reindeer management in the tight of the ongoing global warming. (C) 2005 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

  • 2. Stolter, C
    et al.
    Julkunen-Tiitto, R
    Ganzhorn, J U
    Application of near infrared reflectance spectroscopy (NIRS) to assess some properties of a sub-arctic ecosystem2006In: Basic and Applied Ecology, ISSN 1439-1791, E-ISSN 1618-0089, Vol. 7, no 2, 167-187 p.Article in journal (Refereed)
    Abstract [en]

    Investigations of temporal and spatial variation of chemical properties of ecosystem components on a landscape level are hampered by the need to analyze large numbers of samples. Near infrared reflectance spectroscopy (NIRS) might provide a useful tool. to overcome this problem. Here we investigated the possibilities and Limitations to quantify the chemical composition of different plant parts and ecological. properties with the help of NIRS. For this, we addressed the following questions: (1) Can NIRS-models be used to quantify different primary compounds (nitrogen, fibre), groups of secondary compounds (condensed tannins, total phenotics) as well as specific phenolic components (e.g., salicin) in leaves, twigs and titter of Salix phylicifolia? (2) Can NIRS be used to predict ecological. properties such as moose browsing on willow or the decomposition rate of Leaf titter? NIRS predicted the different primary compounds and grouped secondary compounds in different plant material with high accuracy. Results were inconsistent for specific phenolics. For ecological, properties (moose browsing, titter decomposition rate) NIRS-models had high coefficients of determination. But tests of the models with a second independent set of samples (independent-data-set-test: IDS-test) showed that the predicted values were too tow even though they were ranked correctly. Based on these results, the application of a second independent test is recommended. In the present study this second validation indicated inconsistencies in the NIRS-models that had not been revealed by the conventional validation procedures used to develop the models (test-set and cross-validation). According to the present results NIRS represents a suitable and cost-effective tool. to measure primary and groups of secondary components of plant material. Application to specific phenolic compounds requires more elaborate testing. The successful reconstruction of moose browsing and the prediction of litter decomposition rate show that NIRS offers new possibilities for ecological applications. (c) 2005 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

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