Johan Temnerud

Landscape‐scale variability of acidity and dissolved organic carbon during spring flood in a boreal stream network

Landscape-scale variability of acidity and dissolved organic carbon during spring flood in a boreal stream network

Specific discharge variability in a boreal landscape

Specific discharge variations within a mesoscale catchment were studied on the basis of three synoptic sampling campaigns. These were conducted during stable flow conditions within the Krycklan cat ...

Riparian Zone Influence on Stream Water Dissolved Organic Carbon Concentrations at the Swedish Integrated Monitoring Sites

Short-term variability in stream water dissolved organic carbon (DOC) concentrations is controlled by hydrology, climate and atmospheric deposition. Using the Riparian flow-concentration Integration Model (RIM), we evaluated factors controlling stream water DOC in the Swedish Integrated Monitoring (IM) catchments by separating out hydrological effects on stream DOC dynamics. Model residuals were correlated with climate and deposition-related drivers. DOC was most strongly correlated to water flow in the northern catchment (Gammtratten). The southern Aneboda and Kindla catchments had pronounced seasonal DOC signals, which correlated weakly to flow. DOC concentrations at Gårdsjön increased, potentially in response to declining acid deposition. Soil temperature correlated strongly with model residuals at all sites. Incorporating soil temperature in RIM improved model performance substantially (20–62% lower median absolute error). According to the simulations, the RIM conceptualization of riparian processes explains between 36% (Kindla) and 61% (Aneboda) of the DOC dynamics at the IM sites.

Catchment land cover as a proxy for macroinvertebrate assemblage structure in Carpathian Mountain streams

We compared land cover, riparian vegetation, and instream habitat characteristics with stream macroinvertebrate assemblages in 25 catchments in the Carpathian Mountains in Central Europe. This study area was particularly selected because of its diverse history of forest and agricultural ecosystems linked to geopolitical dynamic, which provide a suite of unique landscape scale, land cover settings in one ecoregion. Canonical Correspondence Analysis (CCA) showed that variation in composition and structure of macroinvertebrate assemblages was primarily related to four land cover types, and not to riparian or instream habitat. These were the portions in the catchment areas of (1) broadleaved forest, (2) fine-grained agricultural landscape mosaic with scattered trees (e.g., pre-industrial cultural landscape), (3) mixed forest, and (4) natural grassland without trees. Principal Component Analysis (PCA) suggested that land cover types and stream channel substrates co-varied. The PCA also showed that chemical variables, including organic carbon, had higher values in the agricultural landscape compared to natural forests. The major source of variation among taxa in streams was higher abundance of Diptera in agricultural landscapes and of Plecoptera, Coleoptera, Trichoptera, and Amphipoda in forests. Gastropoda and Oligochaeta were more abundant in open, fine-grained agricultural landscape mosaics with scattered trees. Ephemeroptera taxa were quite indifferent to these gradients in catchment land cover, but showed a tendency of being more abundant in the pre-industrial cultural landscape. Our findings suggest that land cover can be used as a proxy of the composition and structure of macroinvertebrate assemblages. This means that land use management at the catchment scale is needed for efficient conservation and recovery of stream invertebrate communities.

Patterns and predictability in the intra-annual organic carbon variability across the boreal and hemiboreal landscape.

Factors affecting total organic carbon (TOC) concentrations in 215 watercourses across Sweden were investigated using parameter parsimonious regression approaches to explain spatial and temporal variabilities of the TOC water quality responses. We systematically quantified the effects of discharge, seasonality, and long-term trend as factors controlling intra-annual (among year) and inter-annual (within year) variabilities of TOC by evaluating the spatial variability in model coefficients and catchment characteristics (e.g. land cover, retention time, soil type). Catchment area (0.18-47,000 km2) and land cover types (forests, agriculture and alpine terrain) are typical for the boreal and hemiboreal zones across Fennoscandia. Watercourses had at least 6 years of monthly water quality observations between 1990 and 2010. Statistically significant models (p<0.05) describing variation of TOC in streamflow were identified in 209 of 215 watercourses with a mean Nash-Sutcliffe efficiency index of 0.44. Increasing long-term trends were observed in 149 (70%) of the watercourses, and intra-annual variation in TOC far exceeded inter-annual variation. The average influences of the discharge and seasonality terms on intra-annual variations in daily TOC concentration were 1.4 and 1.3 mg l(-1) (13 and 12% of the mean annual TOC), respectively. The average increase in TOC was 0.17 mg l(-1)year(-1) (1.6% year(-1)). Multivariate regression with over 90 different catchment characteristics explained 21% of the spatial variation in the linear trend coefficient, less than 20% of the variation in the discharge coefficient and 73% of the spatial variation in mean TOC. Specific discharge, water residence time, the variance of daily precipitation, and lake area, explained 45% of the spatial variation in the amplitude of the TOC seasonality. Because the main drivers of temporal variability in TOC are seasonality and discharge, first-order estimates of the influences of climatic variability and change on TOC concentration should be predictable if the studied catchments continue to respond similarly.

Headwater biodiversity among different levels of stream habitat hierarchy

With the current loss of biodiversity and threats to freshwater ecosystems, it is crucial to identify hot-spots of biodiversity and on which spatial scale they can be resolved. Conservation and management of these important ecosystems needs insight into whether most of the regional biodiversity (i.e. γ-diversity) can be found locally (i.e. high α-diversity) or whether it is distributed across the region (i.e. high β-diversity). Biodiversity patterns of benthic macroinvertebrates and diatoms were studied in 30 headwater streams in five Swedish catchments by comparing the relative contribution of α- and β-diversity to γ-diversity between two levels of stream habitat hierarchy (catchment and region level). The relationship between species community structure and local environmental factors was also assessed. Our results show that both α- and β-diversity made a significant contribution to γ-diversity. β-diversity remained relatively constant between the two levels of habitat hierarchy even though local environmental control of the biota decreased from the catchment to the region level. To capture most of headwater γ-diversity, management should therefore target sites that are locally diverse, but at the same time select sites so that β-diversity is maximized. As environmental control of the biota peaked at the catchment level, the conservation of headwater stream diversity is likely to be most effective when management targets environmental conditions across multiple local sites within relatively small catchments.

Nitrogen and carbon interactions between boreal soils and lakes

In this study, we used a large data set on nitrogen (N) and carbon (C) from Swedish boreal soils and lake waters to investigate N and C interactions between soils and lake waters. To link thousands ...