Vegar Bakkestuen

Modelling the benefits of farmland restoration: methodology and application to butterfly movement

Abstract The overall quality of the landscape is important for conserving biodiversity. In a fragmented landscape, movement and dispersal capacity are important factors in determining which species are able to persist. To examine the role of landscape structure and pattern on movement, we developed a simple model to predict the “least-cost” pathway a species would take through an agricultural landscape matrix between habitat fragments by assigning friction values to different habitat types. Our model was validated by using empirical data on inter-patch movement for two butterfly species. As a measure of the ecological distance between habitat patches, the least-cost path model was a better predictor of butterfly movement than Euclidean distance. Ranking several hypothetical management scenarios, illustrated the potential of the model as a decision-support tool. Removal of all infrastructure from within arable fields would significantly reduce rates of inter-patch movement. However, if all boundaries between arable fields were restored to grassy banks this would significantly increase the connectivity between sub-populations. Planners widely recommend using corridors to connect fragments of remnant habitat despite relatively little empirical evidence to show that dispersal of individuals is enhanced by this practice. Our model showed that important aspects of species movement and, hence, survival can be expressed in models suitable for area planning and management.

Extrinsic and intrinsic controls of zooplankton diversity in lakes

Pelagic crustacean zooplankton were collected from 336 Norwegian lakes covering a wide range of latitude, altitude, lake area, mean depth, production (as chlorophyll a), and fish community structure. Mean zooplankton species richness during the ice-free season was generally low at high latitudes and altitudes. Further, lower species richness was recorded in western lakes, possibly reflecting constraints on migration and dispersal. However, despite obvious spatial limitations, geographic boundaries were only weak predictors of mean zooplankton richness. Similarly, lake surface area did not contribute positively to mean richness such as seen in other ecosystem surveys. Rather, intrinsic factors such as primary production and fish community (planktivore) structure were identified by regression analysis as the major predictors of zooplankton diversity, while a positive correlation was observed between species richness and total zooplankton biomass. However, in spite of a large number of variables included in this study, the predictive power of multiple regression models was modest (<50% variance explained), pointing to a major role for within-lake properties, as yet unidentified intrinsic forces, stochasticity, or dispersal as constraints on zooplankton diversity in these lakes.

Genetic roadmap of the Arctic: plant dispersal highways, traffic barriers and capitals of diversity

We provide the first comparative multispecies analysis of spatial genetic structure and diversity in the circumpolar Arctic using a common strategy for sampling and genetic analyses. We aimed to identify and explain potential general patterns of genetic discontinuity/connectivity and diversity, and to compare our findings with previously published hypotheses. We collected and analyzed 7707 samples of 17 widespread arctic-alpine plant species for amplified fragment length polymorphisms (AFLPs). Genetic structure, diversity and distinctiveness were analyzed for each species, and extrapolated to cover the geographic range of each species. The resulting maps were overlaid to produce metamaps. The Arctic and Atlantic Oceans, the Greenlandic ice cap, the Urals, and lowland areas between southern mountain ranges and the Arctic were the strongest barriers against gene flow. Diversity was highest in Beringia and gradually decreased into formerly glaciated areas. The highest degrees of distinctiveness were observed in Siberia. We conclude that large-scale general patterns exist in the Arctic, shaped by the Pleistocene glaciations combined with long-standing physical barriers against gene flow. Beringia served as both refugium and source for interglacial (re)colonization, whereas areas further west in Siberia served as refugia, but less as sources for (re)colonization.

Locating archaeological sites in the landscape: a hierarchical approach based on landscape indicators

Abstract Heritage conservation and management of landscapes is evident in many recent European policies and national reports on the state of the environment. To assist in the management of heritage resources, we present a landscape approach to the identification of localities with a high probability of possessing cultural heritage interests. The low proportion of sites registered in Norway (an estimated 20%) combined with current rates of damage gives the location of archaeological sites and their vulnerability to land use change high priority. To optimise use of the results for landscape planning, the study describes analysis at two hierarchical scales: (1) the regional level—where the aim was to locate combinations of environmental resources suitable for human use—for application in strategic planning; and (2) the landscape level—where identifying and delimiting cultural environments for local planning was the aim. This paper focuses on one type of archaeological site, Bronze and Iron Age grave mounds. The project used geographic information systems (GIS) for the analysis and mapping of landscape characteristics that indicate zones with a high probability of possessing cultural heritage interest. These zones covered ca. 12% of the forested areas of the region yet captured 94% of the registered grave mounds. New fieldwork confirmed the presence of new sites in the zones identified. Results have increased our understanding of archaeological site location in Norway and the close links between landscape ecology and archaeology.

Spatial and temporal variability in epilithic biofilm bacterial communities along an upland river gradient

Riverine biofilms remain one of the least-studied habitats despite the significant increase in the examination of aquatic microbial communities in recent years. In this study, the dynamics of epilithic biofilm communities native on rocks from a low-order upland stream were examined over a period of 3 years. Spatial and temporal variations in bacterial communities were assessed using terminal restriction fragment length polymorphism, based on analysis of the 16S rRNA gene. In total, 108 epilithic biofilm samples were analysed and 170 different ribotypes were detected. A strong temporal gradient in ribotype composition was noticed, especially between samples collected in 2001 and those collected in 2002 and 2003, most likely reflecting interannual differences in weather conditions, such as temperature. A spatial gradient in ribotype composition, from upstream sites to the low-lying sites, was also evident and interpreted as an environmental variation gradient along the river course. Distinct biofilm communities consistently occurred at the first site along the river, which was significantly correlated to low pH. Temporal factors explained the highest degree of variation within the epilithic biofilms. Recurrent blooms of certain bacteria were noted within the system. Phylogenetic relationships of bacteria at one point in the river were determined using a cloning and sequencing approach, with Alphaproteobacteria dominating the community, followed by Cyanobacteria, Bacteroidetes and Betaproteobacteria.

GIS Modeling of Wave Exposure at the Seabed: A Depth-attenuated Wave Exposure Model

Several studies have documented relationships between wave exposure and distribution, density, and size of marine species. Hence, this factor is at a high level in the hierarchical habitat classification system EUNIS and is one of the Water Framework Directive water typology criteria of coastal waters. Isæus (2004) has developed a continuous simplified wave model (SWM) that has been applied to several Nordic countries. Here we refine this model by introducing depth-attenuation, giving us the advantage of a model for wave exposure as it will actually work at the seabed. The values of the depth-attenuated model SWM(d) are approximately similar to the SWM model in shallow areas but noticeably lower in deep areas. The two models were compared in an analysis of the distribution of seabed substrate in the Stockholm archipelago. Using the depth-attenuated wave exposure instead of the SWM model as predictor in substrate modeling improved these models considerably.

A Landscape Ecological Approach to Coastal Zone Applications

Managing complex environments requires suitable tools to integrate data from a variety of sources and efficiently analyse and present them within a geographical context. Recently there has been a growing interest in the integration of geographical, environmental and behavioural data for use in coastal zone management and planning. Our study shows how easily accessible information on bathymetry, terrain variation and wind conditions may be integrated into a georeferenced model applied to the study of key species and ecosystems of the Norwegian coastal zone. Through case studies, we predicted kelp forest ( Laminaria hyperborea ) distribution and analysed harbour seal ( Phoca vitulina ) habitat selection. Combining information on depth and wind exposure derived from a digital terrain model was a suitable approach to predict kelp forest distribution, even though the prediction showed deviations from information provided by kelp harvesters. Including information on sea-bed sediment improved the predictive ability drastically, and more investigation is needed to continue this kind of modelling. This approach is relevant for making decisions concerning site selection of kelp forest harvesting and restoration. Integrating the kelp forest prediction model with information on depth and the presence of slopes, islands and georeferenced behavioural data, we developed a technique for classifying habitats and studying resource selection.

Impact of Scale and Quality of Digital Terrain Models on Predictability of Seabed Terrain Types

The local and regional distribution of seabed terrain types depends on factors such as slope and terrain ruggedness. Digital bathymetrical models (DBM) are therefore essential for mapping and predictive modeling of marine habitats. DBMs vary considerably with respect to scale and quality, and this variation is likely to influence the predictive ability of marine habitat models built with use of DBM-derived environmental predictor variables. We studied the interpretability of seabed terrain types from four different DBMs in two ways: by visual inspection of hillshade representation of the DBMs and by subjecting sets of variables derived from each of the four DBMs to maximum entropy (MaxEnt) predictive modeling of six seabed terrain types. Our results show that DBMs based on multibeam echo sounder data, resampled at resolutions up to 50 m, enable identification of concentrations of seabed terrain types characterized by moraine-ridge assemblies and plough-mark fields. Variables derived from models interpolated from contours of existing marine maps and bathymetric databases have strong limitations and merely enable separation of terrain dominated by rugged bedrock seabed from soft sediment flats. Interpolated DBMs are currently the only type of bathymetrical data that cover all Norwegian coastal waters. Their poor quality is an important obstacle to predictive modeling and classification of seabed habitats.

The ecological niches of Bythotrephes and Leptodora: lessons for predicting long-term effects of invasion

We here exploit two large datasets on zooplankton in Norwegian lakes, spanning a wide range of geographical, physical, chemical and biological properties, to assess the ecological niches and habitats of Bythotrephes longimanus and Leptodora kindtii. The species overlapped geographically, yet co-occurred only in a limited number of lakes. Bythotrephes inhabited virtually all types of lakes, except alpine localities and productive lakes dominated by cyprinid communities where the hyaline Leptodora was most abundant. The zooplankton communities also differed in Bythotrephes and Leptodora lakes, probably both reflecting different predatory regimes, but also water quality and other lake-specific properties. We found no evidence for species being excluded by the presence of Bythotrephes, rather the diversity in general was higher in lakes with these predators present compared with those without. We found, however, a very close association between Bythotrephes and Daphnia galeata and to some extent also between Bythotrephes and D. longispina, suggesting that these species also may benefit from Bythotrephes invasion. Both Bythotrephes and Leptodora species occur naturally in this region, and knowledge about the ecological preferences and the zooplankton community composition in Bythotrephes—and Leptodora lakes will provide valuable information about the long-term effects of Bythotrephes invasion and potential interaction with of Leptodora as top invertebrate predator.

DNA metabarcoding reveals diet overlap between the endangered walia ibex and domestic goats - Implications for conservation

Human population expansion and associated degradation of the habitat of many wildlife species cause loss of biodiversity and species extinctions. The small Simen Mountains National Park in Ethiopia is one of the last strongholds for the preservation of a number of afro-alpine mammals, plants and birds, and it is home to the rare endemic Walia ibex, Capra walie. The narrow distribution range of this species as well as potential competition for resources with livestock, especially with domestic goat, Capra hircus, may compromise its future survival. Based on a curated afro-alpine taxonomic reference library constructed for plant taxon identification, we investigated the diet of the Walia ibex and addressed the dietary overlap with domestic goat using DNA metabarcoding of faecal samples. Faeces of both species were collected from different localities in the National Park. We show that both species are browsers, with forbs, shrubs and trees comprising the largest proportion of their diet, supplemented by grasses. There was a considerable overlap in dietary preferences. Several of the preferred diet items of the Walia ibex (Alchemilla sp., Hypericum revolutum, Erica arborea and Rumex sp.) were also among the most preferred diet items of the domestic goat. These results indicate that there is potential for competition between the two species, especially during the dry season, when resources are limited. Our findings, in combination with the expected increase in domestic herbivores, suggest that management plans should consider the potential threat posed by domestic goats to ensure future survival of the endangered Walia ibex.