Wildfires produce a charcoal layer, which has an adsorbing capacity resembling activated carbon. After the fire a new litter layer starts to accumulate on top of the charcoal layer, which liberates water-soluble compounds that percolate through the charcoal and the unburned humus layer. We first hypothesized that since charcoal has the capacity to adsorb organic compounds it may form a new habitat for microbes, which decompose the adsorbed compounds. Secondly, we hypothesized that the charcoal may cause depletion of decomposable organic carbon in the underlying humus and thus reduce the microbial biomass. To test our hypotheses we prepared microcosms, where we placed non-heated humus and on top one of the adsorbents: non-adsorptive pumice (Pum), charcoal from Empetrum nigrum (EmpCh), charcoal from humus (HuCh) or activated carbon (ActC). We watered them with birch leaf litter extract. The adsorbing capacity increased in the order Pum<HuCh<EmpCh<ActC, the adsorbents being capable of removing 0%, 26%, 42% and 51% of the dissolved Corg in the litter extract, respectively. After one month, all adsorbents harboured microbes, but their amount and basal respiration was largest in EmpCh and HuCh, and smallest in Pum. In addition, different kinds of microbial communities with respect to their phospholipid fatty acid and substrate utilization patterns were formed in the adsorbents. The amount of microbial biomass and number of bacteria did not differ between humus under different adsorbents, although different microbial communities developed in humus under EmpCh compared with Pum, which is obviously related to the increased pH of the humus under EmpCh, and also ActC. We suggest that charcoal from burning can support microbial communities, which are small in size but have a higher specific growth rate than those of the humus. Although the charcoal layer induces changes in the microbial community of the humus, it does not reduce the amount of humus microbes.

Charcoal as a habitat for microbes and its effect on the microbial community of the underlying humus

The effects of nitrogen (N) deposition on plant litter and soil organic matter decomposition differ depending on the stage of decomposition (early, late, and final stages). The effects can be divid...

Effect of N deposition on decomposition of plant litter and soil organic matter in forest systems

Different conceptual and simulation models of soil organic matter (SOM) have been developed during the last 20 yr. Jenkinson and Rayners (1977) developed the first widely used SOM model. This model divided soil C into active, slow and passive pools that have different turnover times (1 yr, 30 yr, and 1500 yr, respectively). This conceptual framework has been used in many of the recently developed SOM models (van Veen & Paul, 1981; Parton et aI., 1987; Jenkinson, 1990). van Veen and Paul (1981) improved on Jenkinson and Rayners (1977) model by including concepts of physical and chemical protection, and factors such as soil erosion and soil cultivation. Parton et al. (1987) added the impact of soil texture on SOM dynamics and developed generalized nutrient cycling submodels which simultaneously simulate soil C and inorganic and organic N, P and S dynamics (Parton et aI., 1988). Jenkinson's most recent model (Jenkinson, 1990) also includes soil physical protection by clay. Many of the concepts used in the different SOM models have been incorporated into the nutrient cycling models that are linked to crop plant production models [Erosion-Productivity Impact Calculator (EPIC), Williams et aI., 1985; Nitrogen-Tillage-Residue Management (NTRM), Shaffer, 1985; DeNitrification and DeComposition Model (DNDC), Li

A general model for soil organic matter dynamics: sensitivity to litter chemistry, texture and management.

In northern coniferous forests nutrient release from litter occurs primarily in late stages of decomposition when mainly extensively lignified parts remain An important regulating factor in these 

Nutrient release from litter and humus in coniferous forest soils—a mini review

Advances in our understanding of the decomposition processes in forest ecosystems over the past three decades have demonstrated the importance of lignin as a regulating factor in the decomposition of leaf litter. Consequently, increasingly more attention is being focused on the ecology of fungi associated with lignin decomposition. The aim of this review is to provide a critical summary of the ecology of ligninolytic fungi inhabiting leaf litter and forest floor materials. The review focuses on the following aspects of ligninolytic fungi: the taxonomic and functional diversity of ligninolytic fungi, the outcomes of interactions between ligninolytic fungi and other organisms, the activity and abundance of ligninolytic fungi measured by the production of bleached leaves and humus, the activity of ligninolytic enzymes in soil environments, the substratum and seral succession, spatial and temporal patterns in both mycelial abundance and species distribution, and the effect of environmental factors such as nitrogen deposition and global environmental changes on ligninolytic fungi. This review integrates the ecology, diversity, and activity of ligninolytic fungi into the context of an ecosystem in order to provide an understanding of the roles of ligninolytic fungi in decomposition processes.

B. Berg

Papers

Changes in organic-chemical components and ingrowth of fungal mycelium in decomposing birch leaf litter as compared to pine needles