Christian Pedersen

Research Scientist

(+47) 974 34 123
christian.pedersen@nibio.no

Place
Ås R9

Visiting address
Raveien 9, 1430 Ås

To document

Abstract

Aim Species–area relationships (SARs) are fundamental scaling laws in ecology although their shape is still disputed. At larger areas, power laws best represent SARs. Yet, it remains unclear whether SARs follow other shapes at finer spatial grains in continuous vegetation. We asked which function describes SARs best at small grains and explored how sampling methodology or the environment influence SAR shape. Location Palaearctic grasslands and other non‐forested habitats. Taxa Vascular plants, bryophytes and lichens. Methods We used the GrassPlot database, containing standardized vegetation‐plot data from vascular plants, bryophytes and lichens spanning a wide range of grassland types throughout the Palaearctic and including 2,057 nested‐plot series with at least seven grain sizes ranging from 1 cm2 to 1,024 m2. Using nonlinear regression, we assessed the appropriateness of different SAR functions (power, power quadratic, power breakpoint, logarithmic, Michaelis–Menten). Based on AICc, we tested whether the ranking of functions differed among taxonomic groups, methodological settings, biomes or vegetation types. Results The power function was the most suitable function across the studied taxonomic groups. The superiority of this function increased from lichens to bryophytes to vascular plants to all three taxonomic groups together. The sampling method was highly influential as rooted presence sampling decreased the performance of the power function. By contrast, biome and vegetation type had practically no influence on the superiority of the power law. Main conclusions We conclude that SARs of sessile organisms at smaller spatial grains are best approximated by a power function. This coincides with several other comprehensive studies of SARs at different grain sizes and for different taxa, thus supporting the general appropriateness of the power function for modelling species diversity over a wide range of grain sizes. The poor performance of the Michaelis–Menten function demonstrates that richness within plant communities generally does not approach any saturation, thus calling into question the concept of minimal area.

To document

Abstract

We report an observation of a flightless fledgling Lapland longspur (Calcarius lapponicus (Linnaeus, 1758)) at a long-term study site near Kangerlussuaq, Greenland, in late July 2018. Based on our observations of longspur nests at the site dating back to 1993, we estimate that the fledgling observed in 2018 may have originated from a nest initiated 12–37 d later than nesting in previous years. Onset of spring in 2018 was late, but comparable with other years in which longspur nests were observed a full calendar month earlier than in 2018. An analysis including multiple candidate predictor variables revealed a strong negative association between estimated longspur nest initiation dates and mean May temperature, as well as a weaker association with the length of the annual period of vegetation green up at the site. Given the limitations of our data, however, we are unable to assign causality to the 2018 observation, and cannot rule out other possibilities, such as that it may have resulted from a second clutch.

Abstract

The decline in farmland birds observed throughout Europe during recent decades has attracted much attention. Agricultural intensification or land abandonment are commonly forwarded as key drivers. Several countries have established agri-environmental schemes (AES) to counter these negative trends among farmland birds. This paper reports a study of the relationship between land use and bird species in the agricultural landscape of Norway. The main objective was to investigate the effect of spatial heterogeneity and diversity of land use on total richness and abundance of farmland birds at a national level. Monitoring the distribution and abundance of birds is part of the Norwegian monitoring programme for agricultural landscapes. The monitoring programme is based on mapping of 1 × 1 km squares distributed across the entire agricultural landscape. Within these squares permanent observation points are established for bird monitoring. Detailed interpretation of aerial photographs provides the land classification. We tested the relationship between landscape metrics at different levels of land type detail and species richness and abundance of farmland and non-farmland birds. There was a positive relationship between species richness and abundance of farmland birds and agricultural area. For non-farmland birds the relationship was negative. Spatial heterogeneity of land use was a significant positive factor for both farmland and non-farmland species. High land type diversity was positive for farmland bird richness, but negative for abundance. Non-farmland bird richness was not affected by land type diversity, but abundance had a negative response. The results presented in this paper highlight the importance of a spatial heterogeneous landscape. However, we also found that land type diversity could negatively affect the abundance of both farmland and non-farmland birds. Our findings suggest a need for different management approaches depending on whether the aim is increased species richness or abundance. Achieving both aims with the same means might be difficult. We thus suggest a need for land use analyses before proper management strategies can be implemented.

Abstract

Background & Aim: Land-use regimes and their changes, as well as landscape heterogeneity are key determinants of the distribution and composition of species in cultural landscapes. In European agricultural landscapes, habitat loss due to both abandonment and intensification of agriculture fields are major causes for the decline of species diversity. Landscapes that are diverse in habitats and species are important to maintain basic ecosystem functions and services as, for instance, pollination or habitat preservation. In Norway, semi-natural species-rich habitats, such as agricultural grasslands, often occur in mosaics with forests and crop fields. This research studies key information for design of conservation plans focused on these habitats, addressing how landscape structure and land-use history affect the distribution, richness and composition of species in species-rich grasslands across geographical regions. Material & Methods: We recorded vegetation (species occurrence and cover) in agricultural grasslands with varying intensity and type of use from 569 plots of 8 x 8 m size systematically distributed throughout Norway (from 64 to 78 °N latitude). To identify the most important driving factors of species diversity and composition we explored the combined effects of historic and current land-use and the spatial landscape configuration of nearby land cover types (e.g. minimum distance to or area of neighbouring wetland, forest, cultivated land) taking into account the effects of grazing, elevation, and moisture conditions. Non-metrical multidimensional scaling (NMDS) was applied to identify the most important drivers of species composition. We used Generalized Additive Mixed Models to test the relationship of these drivers with patterns in species richness. Main results & Interpretations: NMDS revealed species composition to be explained most by the distance to surface cultivated land and transportation corridors (r=0.905, p<0.001 and r=-0.982, p<0.001; 1. NMDS axis) as well as shape of the patch in which the vegetation plot is embedded (patch shape) and grazing intensity (r=0.988, p<0.001 and r=-0.952, p<0.001; 2. NMDS axis). Observed patterns in species richness were statistically significantly linked to the combined effects of elevation, grazing intensity, historical land-use, patch shape, distance to transportation corridors and forest, and area of nearest wetland. Our results demonstrate the importance of a variety of factors influencing the species composition and richness in Norwegian grasslands. We found that both the landscape element harbouring the observed plot and also the surrounding landscape structure and intensity of land-use are important determinants of species diversity. The fact that distance to more intensively managed agricultural land is one of the strongest explanatory facts signals how effects of agricultural management practices reaches outside the field itself and into adjacent landscape elements. This suggests that the entire landscape needs to be taken into consideration when management of a particular habitat patch is planned.

To document

Abstract

Interspecific interaction among sympatric ungulates is important in management and conservation. We investigated behavioral interference between sympatric wild or semidomestic reindeer (Rangifer tarandus tarandus) and sheep (Ovis aries) in two field studies and one enclosure experiment. For free-ranging wild and semidomestic reindeer, interference between the two species increased with decreasing distances, occurring only at less than 200 m and 30 m, for wild and semidomestic reindeer, respectively, and neither species consistently dominated the other. In a controlled, duplicated experiment we tested interference and confrontations at the feeding patch level among semidomestic reindeer and sheep within 40 × 50 m enclosures. When new reindeer or sheep were introduced into enclosures already occupied by reindeer, new reindeer resulted in significantly more interference and confrontations among individuals compared to new sheep; i.e., intraspecific interference was more prevalent than interspecific interference at equal densities. For all study areas, confrontations decreased with time after “first encounter,” indicating cohabituation. A sympatric use of pastures was not visually disruptive for recorded grazing behavior for either species.

Abstract

As in many countries throughout Europe, there has been a polarisation within the agricultural landscape of Norway during the last decades. On the one hand there is an increasing trend of intensified use of favourable areas, while on the otherhand there is an increase in the amount of land abandonment of extensively managed or marginal areas (Fjellstad Dramstad 1999, Robinson Sutherland 2002, Haines-Younget al. 2003). Among the main impact factors for biodiversity in agricultural landscapes are increased amount of built-up areas, intensification of agriculture and land abandonment. But different land use practices has been shown to have differential effects on biodiversity (Haines-Young 2009). Finding the relationships between land use practices and effects on biodiversity are fundamental to understand the links between people and their environment and development of sustainable agriculture ....