Hans Göransson

Bacterial, Archaeal and Fungal Succession in the Forefield of a Receding Glacier

Glacier forefield chronosequences, initially composed of barren substrate after glacier retreat, are ideal locations to study primary microbial colonization and succession in a natural environment. We characterized the structure and composition of bacterial, archaeal and fungal communities in exposed rock substrates along the Damma glacier forefield in central Switzerland. Soil samples were taken along the forefield from sites ranging from fine granite sand devoid of vegetation near the glacier terminus to well-developed soils covered with vegetation. The microbial communities were studied with genetic profiling (T-RFLP) and sequencing of clone libraries. According to the T-RFLP profiles, bacteria showed a high Shannon diversity index (H) (ranging from 2.3 to 3.4) with no trend along the forefield. The major bacterial lineages were Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes and Cyanobacteria. An interesting finding was that Euryarchaeota were predominantly colonizing young soils and Crenarchaeota mainly mature soils. Fungi shifted from an Ascomycota-dominated community in young soils to a more Basidiomycota-dominated community in old soils. Redundancy analysis indicated that base saturation, pH, soil C and N contents and plant coverage, all related to soil age, correlated with the microbial succession along the forefield.

Functional Biodiversity Aspects on the Nutrient Sustainability in Forests–: Importance of Root Distribution

Abstract Nutrient availability is of major importance for plant productivity. When estimating long-term sustainability from a nutrient perspective it is therefore interesting to focus on long-term changes in the soil nutrient pools when comparing different forest types. Here, we have highlighted some factors of importance for long term nutrient sustainability (e.g., several forest rotations) and pointed out some important features that differ between forest tree species and also between monocultures and mixed species stands. Using computer models like PROFILE reveals tree rooting depth to be a crucial factor when assessing long-term nutrient sustainability. Literature studies show that soil type and other soil conditions have a strong effect on root distribution. However, Norway spruce is generally a very shallow rooted species, with approximately 80% of it fine roots in the top 20–25 cm, whereas for pendiculate oak, generally 80% of the roots are found down to 60 cm soil depth. Rooting depth of Scots pine and beech seem to be intermediate with 80% of the roots down to approximately 25–30 cm and 30–35 cm, respectively. Importance of mycorrhiza for nutrient uptake in a sustainability perspective is discussed in the paper.

Changes in land use alter soil quality and aggregate stability in the highlands of northern Ethiopia

Land use change alters biodiversity and soil quality and thus affects ecosystem functions. This study investigated the effects of changes in land use on major soil quality indicators. Soil samples were taken from a depth of 0–10 cm (top soil) under four major land uses (cropland, grassland, area exclosure, eucalyptus plantation) with similar land use change histories for analysis, and soil from a nearby natural forest was used as a reference. Land use change from natural forest to cropland and grassland significantly decreased major soil quality indicators such as soil organic C (SOC), total soil N (TSN), molybdate-reactive bicarbonate-extractable P, and arbuscular mycorrhizal fungi (AMF) spore density, but compared to the cropland, change to area exclosure and eucalyptus plantation significantly improved SOC, TSN and soil aggregate stability (SAS). In addition, we assessed the correlation among indicators and found that SOC, TSN and SAS significantly correlate with many other soil quality indicators. The study highlights that the conversion of natural forest to cropland results in decline of soil quality and aggregate stability. However, compared to cropland, application of area exclosure and afforestation on degraded lands restores soil quality and aggregate stability.

Overyielding of temperate deciduous tree mixtures is maintained under throughfall reduction

Background and aimsA changing climate in the future with more severe drought events will affect the conditions for forest growth and vitality. Most knowledge on tree species response to drought is based on monocultures, even though many of the forests in the world consist of mixed stands. We aimed to investigate how trees respond to summer drought when grown in a three species mixture.MethodsFor two subsequent summers canopy throughfall, and subsequently soil water potential, was reduced using sub-canopy roofs in monocultures and mixtures of Betula pendula, Alnus glutinosa and Fagus sylvatica,.ResultsThe overyielding of the mixed stand was not affected by the drought using either above or below ground production, standing fine root biomass or soil respiration as parameters. However, Alnus glutinosa was the most negatively affected when growing in monoculture, whereas this species was less affected when growing in mixture. In contrast, Betula pendula was most negatively affected when growing in mixture. Fagus sylvatica was least affected by the drought and maintained growth over the two years.ConclusionsA water demanding species as Alnus glutinosa can perform well in a mixture during drought and not be outcompeted. This is opposite to what is assumed in most models of forest responses to climate change.