Decaying wood plays an important role in forest biodiversity, nutrient cycling and carbon balance. Community structure of wood-inhabiting fungi changes with mass loss of wood, but the relationship between substrate quality and decomposers is poorly understood. This limits the extent to which these ecosystem services can be effectively managed. We studied the fungal community and physico-chemical quality (stage of decay, dimensions, density, moisture, C : N ratio, lignin and water or ethanol extractives) of 543 Norway spruce logs in five unmanaged boreal forest sites of southern Finland. Fungi were identified using denaturing gradient gel electrophoresis and sequencing of DNA extracted directly from wood samples. Macroscopic fruiting bodies were also recorded. Results showed a fungal community succession with decreasing wood density and C : N ratio, and increasing moisture and lignin content. Fungal diversity peaked in the most decayed substrates. Ascomycetes typically colonized recently fallen wood. Brown-rot fungi preferred the intermediate decay stages. White-rot fungi represented approximately one-fifth of sequenced species in all decay phases excluding the final phase, where ectomycorrhizal (ECM) fungi became dominant. Lignin content of logs with white-rot fungi was low, and ECM fungi were associated with substrates containing abundant nitrogen. Macroscopic fruiting bodies were observed for only a small number of species detected with molecular techniques.

Forest biomass and its change over time have been measured at both local and large scales, an example for the latter being forest greenhouse gas inventories. Currently used methodologies to obtain stock change estimates for large forest areas are mostly based on forest inventory information as well as various factors, referred to as biomass factors, or biomass equations, which transform diameter, height or volume data into biomass estimates. However, while forest inventories usually apply statistically sound sampling and can provide representative estimates for large forest areas, the biomass factors or equations used are, in most cases, not representative, because they are based on local studies. Moreover, their application is controversial due to the inconsistent or inappropriate use of definitions involved. There is no standardized terminology of the various factors, and the use of terms and definitions is often confusing. The present contribution aims at systematically summarizing the main types of biomass factors (BF) and biomass equations (BE) and providing guidance on how to proceed when selecting, developing and applying proper factors or equations to be used in forest biomass estimation. The contribution builds on the guidance given by the IPCC (Good practice guidance for land use, land-use change and forestry, 2003) and suggests that proper application and reporting of biomass factors and equations and transparent and consistent reporting of forest carbon inventories are needed in both scientific literature and the greenhouse gas inventory reports of countries.

No abstract

No abstract

Forest soils store a substantial amount of carbon, often more than the forest vegetation does. Estimates of the amount of soil carbon, and in particular estimates of changes in these amounts are still inaccurate. Measuring soil carbon is laborious, and measurements taken at a few statistically unrepresentative sites are difficult to scale to larger areas.We combined a simple dynamic model of soil carbon with litter production estimated on the basis of stand parameters, models of tree allometry and biomass turnover rates of different biomass components. This integrated method was used to simulate soil carbon as forest stands develop. The results were compared with measurements of soil carbon from 64 forest sites in southern Finland.Measured carbon stocks in the organic soil layer increased by an average of 4.7 AE 1.4 g m À2 a À1 with increasing stand age and no significant changes were measured in the amount of carbon in mineral soil. Our integrated method indicated that soil carbon stocks declined to a minimum 20 years after clear-cutting and the subsequent increase in the soil carbon stock (F/H À 1 m) was 5.8 AE 1.0 g m À2 a À1 averaged over the period to next harvesting ( $ 125 years). Simulated soil carbon accumulation slowed down considerably in stands older than 50 years. The carbon stock measured (F/H À 1 m) for the study area averaged 6.8 AE 2.5 kg m À2 . The simulated carbon stock in soil was 7.0 AE 0.6 kg m À2 on average.These tests of the validity of the integrated model suggest that this method is suitable for estimating the amount of carbon in soil and its changes on regional scales.