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- Bergfur, J., et al.
(författare)
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Effects of nutrient enrichment on boreal streams : Invertebrates, fungi and leaf-litter breakdown
- 2007
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 52:8, s. 1618-1633
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Tidskriftsartikel (refereegranskat)abstract
- Summary 1. The effect of nutrient enrichment on structural (invertebrate indices) and functional (leaf-litter breakdown rates) characteristics of stream integrity was studied in nine boreal streams.2. The results showed predicted changes in biotic indices and leaf-litter breakdown along a complex (principal component) nutrient gradient. Biotic indices were better correlated with nutrient effects than leaf-litter breakdown.3. Fungal biomass and invertebrate densities in the litter bags were positively correlated with leaf-litter breakdown, and both were also positively related to the nutrient gradient.4. Invertebrate community composition influenced breakdown rate. High breakdown rates at one site were associated with the high abundance of the detritivore Asellus aquaticus. 5. This study lends support to the importance of invertebrate and fungi as mediators of leaf-litter decomposition. However, our study also shows that study design (length of incubation) can confound the interpretation of nutrient-induced effects on decomposition.
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| 2. |
- Bergfur, J, et al.
(författare)
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Phenological changes within a growth season in two semi-natural pastures in southern Sweden
- 2004
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Ingår i: Annales Botanici Fennici. - 0003-3847 .- 1797-2442. ; 41:1, s. 15-25
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Tidskriftsartikel (refereegranskat)abstract
- Phenological changes within a growth season were investigated in two grazed, semi-natural grasslands in southern Sweden. On four occasions during the growth season, two independent observers recorded plant frequency and percentage cover. The vegetation data sets were analysed with ordination methods. The temporal changes were highly significant, but accounted for only a small part of the total variation in the data. Most species had early maxima, regarding both cover and frequency. There were differences in temporal pattern between the two grasslands. In a xeric area, the vegetation underwent a major change sometime in August, between survey-visit three and four. In a mesic area, the vegetation changed throughout the study period but least so during August. Therefore, phenological changes can be manifested in different ways, even within the same geographic region. Species-wise ordination scores highlighted those species whose records might be most affected by phenological patterns, information which is valuable when evaluating data collected in Scandinavian grasslands.
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| 3. |
- Bergfur, Jenny, et al.
(författare)
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The Tarland Catchment Initiative and Its Effect on Stream Water Quality and Macroinvertebrate Indices
- 2012
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Ingår i: Journal of Environmental Quality. - : American society of Agronomy, Inc. - 0047-2425 .- 1537-2537. ; 41:2, s. 314-321
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Tidskriftsartikel (refereegranskat)abstract
- The Tarland Catchment Initiative is a partnership venture between researchers, land managers, regulators, and the local community. Its aims are to improve water quality, promote biodiversity, and increase awareness of catchment management. In this study, the effects of buffer strip installations and remediation of a large septic tank effluent were appraised by water physico-chemistry (suspended solids, NO3, NH4, soluble reactive P) and stream macroinvertebrate indices used by the Scottish Environmental Protection Agency. It was done during before and after interventions over an 8-yr period using a paired catchment approach. Because macroinvertebrate indices were previously shown to respond negatively to suspended solid concentrations in the study area, the installation of buffer strips along the headwaters was expected to improve macroinvertebrate scores. Although water quality (soluble reactive P, NH4) improved downstream of the septic tank effluent after remediation, there was no detectable change in macroinvertebrate scores. Buffer strip installations in the headwaters had no measurable effects (beyond possible weak trends) on water quality or macroinvertebrate scores. Either the buffer strips have so far been ineffective or ineffectiveness of assessment methods and sampling frequency and time lags in recovery prevent us detecting reliable effects. To explain and appreciate these constraints on measuring stream recovery, continuous capacity building with land managers and other stakeholders is essential; otherwise, the feasibility of undertaking sufficient management interventions is likely to be compromised and projects deemed unsuccessful.
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| 4. |
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| 5. |
- Fischer, Helmut, et al.
(författare)
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Microbial leaf degraders in boreal streams : bringing together stochastic and deterministic regulators of community composition
- 2009
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 54:11, s. 2276-2289
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Tidskriftsartikel (refereegranskat)abstract
- Leaves that fall into the water represent a new habitat for microorganisms to colonise in streams, providing an opportunity to study colonisation and the subsequent regulation of community structure. We explored community composition of bacteria and fungi on decomposing alder leaves in nine streams in central Sweden, and describe their relationship with environmental variables. Succession of the microbial community was studied in one of the streams for 118 days. Microbial community composition was examined by denaturing gradient gel electrophoresis on replicate samples of leaves from each stream. 2. During succession in one stream, maximum taxon richness was reached after 34 days for bacteria and 20 days for fungi respectively. Replicate samples within this stream differed between each other earlier in colonisation, while subsequently such variation among replicate communities was low and remained stable for several weeks. Replicate samples taken from all the nine streams after 34 days of succession showed striking similarities in microbial communities within-streams, although communities differed more strongly between streams. 3. Canonical analysis of microbial communities and environmental variables revealed that water chemistry had a significant influence on community composition. This influence was superimposed on a statistical relationship between the properties of stream catchments and microbial community composition. 4. The catchment regulates microbial communities in two different ways. It harbours the species pool from which the in-stream microbial community is drawn and it governs stream chemistry and the composition of organic substrates that further shape the communities. We suggest that there is a random element to colonisation early in succession, whereas other factors such as species interactions, stream chemistry and organic substrate properties, result in a more deterministic regulation of communities during later stages.
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