Biology subjects

Halvorsen, R.

Publications and source records attributed to Halvorsen, R..

3 recordsLinked to original sources

bioRxiv2026

Long-term shift in community composition of deadwood fungi after clear-cutting

O_LIRising anthropogenic pressures in the 20th century have caused extensive habitat loss and fragmentation, threatening biodiversity across ecosystems worldwide. In the boreal forest of Fennoscandia, clear-cut forestry has been a major driver of these changes, resulting in a fragmented landscape of even-aged forest stands. Several studies in recent years have investigated the effect of habitat fragmentation and loss on fungal communities associated with deadwood, but these have mainly focused on visible sporocarps and mushrooms. The effects of forestry on the whole fungal community within deadwood have not been explored as extensively, and especially not in the context of long-term effects. C_LIO_LIWe investigated the effects of clear-cutting on deadwood-inhabiting fungi in boreal Picea abies forests in Norway using ITS2 metabarcoding of sawdust samples collected from 459 logs distributed across 24 paired near-natural and previously clear-cut plots harvested 50 to 90 years ago. C_LIO_LIWhile the overall fungal richness associated with deadwood was similar between the two management types, community composition differed markedly. Plot-scale fungal diversity was linked to deadwood heterogeneity, and composition of the common species was additionally affected by the living tree structure. Nearly all red-listed species were exclusively found in the near-natural forest plots. These findings demonstrate that clear-cut forestry shifts fungal community structure rather than reducing the total number of species and that rare and common species are structured by different environmental drivers but respond in similar ways to large scale disturbance. C_LIO_LISynthesis: Our results highlight the importance of maintaining structural complexity of deadwood in boreal forests for fungal conservation. We found a consistent relationship between deadwood volumes and heterogeneity, and community diversity and species richness. This relationship was consistent even for previously clear-cut forests, showing that retaining structural heterogeneity in managed ecosystems has a positive impact on species diversity. C_LI

ecology↗

bioRxiv2020

Diversity and distribution of landscape types in Norway

Norwegian landscapes are changing at an increasingly rapid rate, and systematically structured information about observable landscape variation is required for knowledge-based management of landscape diversity. Here we present the first version of a complete, area-covering, evidence-based landscape-type map of Norway, simultaneously addressing geo-ecological, bio-ecological and land-use related variation at the landscape level. We do so by applying map algebra operations on publicly available geographical data sets with full areal coverage for Norway. The type system used in the mapping is supported by systematically structured empirical evidence. We present the results of the mapping procedure, including the geographical distribution and descriptive statistics (abundance and areal coverage) for each of the identified landscape types. We identify nine major landscape types based on coarse-scale landform variation and, within the six inland and coastal major types, 284 minor landscape types are defined based on the composition of geo-ecological, bio-ecological, and land use-related landscape properties. The results provide new insights into the geography of Norwegian marine, coastal and inland landscapes. We discuss potential errors, uncertainties and limitations of the landscape-type maps, and address the potential value of this new tool for research, management and planning purposes.

ecology↗

bioRxiv2020

Gradient analysis of landscape variation in Norway

A multitude of landscape characterisation and mapping methods exist, but few methods take into account that landscapes properties vary in a gradual, continuous manner along multiple directions of variation. In this study, we used gradient analytic methods, rooted in ecological continuum theory, to analyse landscape variation throughout Norway. The aim is to explain differences in landscape properties in the simplest possible way, by identifying complex landscape gradients (CLGs), i.e. composite gradients of co-occurring landscape elements and properties. We collected data by stratified sampling of 100 test areas (20x20 km), in which we delineated a total of 3966 observation units (landscape polygons 4-30 km{superscript 2}) based on geomorphological criteria. For each observation unit, 85 landscape variables were recorded. We identified patterns of variation in landscape element composition by parallel use of two multivariate statistical methods, detrended correspondence analysis (DCA) and global nonmetric multidimensional scaling (GNMDS). The analyses revealed that the most important properties explaining differences in total landscape elements composition was location of the landscape relative to the coastline and coarse-scale landform variation. Most landscape elements had distinct optima within specific segments along broad-scale complex-gradients in landscape properties. A tentative landscape-type hierarchy was built by an iterative procedure by which the amount of compositional turnover in landscape-element composition between adjacent types was standardised. Six major landscape types were identified based on geomorphological criteria. Within each major type, we identified a unique set of 2-5 important CLGs, representing geo-ecological, bio-ecological, and land use-related landscape variation. Minor landscape types were obtained by combining segments along two or more CLGs. The study shows that geological diversity, biological diversity and human land-use are tightly intertwined at the landscape level of ecological complexity, and that predominantly abiotic processes control and constrain both biotic processes and human land use.

ecology↗