Ivar Gjerde
Research Professor
Authors
Eivind Handegard Ivar Gjerde Rune Halvorsen Robert John Lewis Ken Olaf Storaunet Magne Sætersdal Olav SkarpaasAbstract
Multiple ecological drivers, along with forest age, determine the species composition of boreal forest ecosystems. However, the role of age in successional changes in forests cannot be understood without taking site conditions, the disturbance regime and forest structure into account. In this study, we ask two research questions: 1. What is the relationship between forest age and overall species composition in older near-natural spruce forests, i.e. forests of age beyond harvest maturity? 2. Do species associated with different forest habitats respond similarly to variation in forest age? Data were collected in 257 Norway spruce dominated 0.25 ha plots from three study areas in Southeastern and Central Norway. Species inventories were conducted for lichens and bryophytes on trees and rocks, vascular plants on the forest floor, and for deadwood-associated bryophytes and polypore fungi. Although NMDS ordination analyses of the total species composition identified a main axis related to the age of the oldest trees in two of the study areas, variation partitioning analyses showed that age explained a small fraction of variation of the species composition compared to site conditions, logging history, forest structure, and differences between the sites in all habitats. The unique variation explained by forest age species was, however, significant for all habitats. The fraction of variation in species composition explained by forest age was the largest for lichens and bryophytes on trees, and for deadwood-associated bryophytes and polypore fungi. Our results suggest that practical mapping of near-natural forests for management purposes inventories should include site conditions, forest structure and between site differences in addition to forest age.
Authors
Roberto Guidetti Łukasz Kaczmarek Milena Roszkowska Terje Meier Tommy Prestø K. Ingemar Jönsson James David Mervyn Speed Elisabeth Stur Ivar Gjerde Lasse Topstad Kristian Hassel Torbjørn EkremAbstract
Background: Tardigrades are common in most habitats, however few studies have focusedon large faunistic survey, specifically on tardigrade diversity in forests. Up to now, only 61 species have been recorded in different types of forest in Norway with an additional 25 found in limnic environments in forests. Although little is known about the ecological preferences of many species, previous studies have found that tardigrade diversity and community composition are significantly affected by ecological variables. In this study we associate georeferenced tardigrade species records with forest type, substrate type and substrate composition in order to see if tardigrade diversity and species communities can be associated with ecological characteristics of Norwegian forests. Methods: In total 390 moss, lichen and litter samples were collected from 12 forests in central and southern Norway in the summers of 2017 and 2018 and later stored in paper envelopes. For the identification modern literature and keys for specific genera and groups of species were used. For statistical analyses, moss and lichen substrate of each sample was classified according to the main species, life form, growth forms and habitat of substrate and associated with each tardigrade identification and sample metadata. Results: A total of 17 407 specimens were identified, encompassing in total 132 species (including some new species). Species richness increases with precipitation, but does not change with temperature or precipitation seasonality. The distribution of species richness between life forms and forest types showed considerable variation within and among the variables. Disregarding variables with low sample numbers, among life forms only acrocarpous moss samples appeared to deviate with respect to species richness, containing less species than substrates with other life forms. Conclusions: Tardigrades in Norwegian forest are extremely abundant, frequent and diverse. Moreover, it appears that that certain species and/or entire communities prefer specific microhabitats.
Abstract
Old trees are important for biodiversity, and the process of their identification is a critical process in their conservation. However, determining the tree age by core extraction, ring counts, and eventually, cross-dating by means of dendrochronology is labor-intensive and expensive. Here we examine the alternative method of estimating determining tree age by visual characteristics for old Norway spruce and Scots pine trees. We used forest stands previously identified as “Old tree habitats” by visual criteria in Norwegian boreal forests. The efficiency of this method was tested using pairwise comparison of the age of core samples from trees within these sites, and within neighboring sites. Age regression models were constructed from morphological traits and site variables to investigate how accurately old trees can be detected. Cored trees in the Old-tree habitats were on average 41.9 years older than compared to a similar selection of trees from nearby mature forests. Several characteristics such as bark structure, stem taper and visible growth eccentricities can be used to identify old Norway spruce and Scots pine trees. Old trees were often found on less productive sites. Due to the wide range of environments included in the study, we suggest that these findings can be generalized to other parts of the boreal zone.