Hannu Ilvesniemi

Advances in understanding the podzolization process resulting from a multidisciplinary study of three coniferous forest soils in the Nordic Countries

Advances in understanding the podzolisation process resulting from a multidisciplinary study at three coniferous forest soils in the Nordic countries

Effect of thinning on surface fluxes in a boreal forest

[1] Thinning is a routine forest management operation that changes tree spacing, number, and size distribution and affects the material flows between vegetation and the atmosphere. Here, using direct micrometeorological ecosystem-scale measurements, we show that in a boreal pine forest, thinning decreases the deposition velocities of fine particles as expected but does not reduce the carbon sink, water vapor flux, or ozone deposition. The thinning decreased the all-sided leaf area index from 8 to 6, and we suggest that the redistribution of sources and sinks within the ecosystem compensated for this reduction in foliage area. In the case of water vapor and O 3 , changes in light penetration and among-tree competition seem to increase individual transpiration rates and lead to larger stomatal apertures, thus enhancing also O 3 deposition. In the case of CO 2 , increased ground vegetation assimilation and decreased autotrophic respiration seem to cancel out opposite changes in canopy assimilation and heterotrophic respiration. Current soil-vegetation-atmosphere transfer models should be able to reproduce these observations.

Distribution and mobilization of Al, Fe and Si in three podzolic soil profiles in relation to the humus layer.

Distribution and mobilization of Al, Fe and Si in three podzolic soil profiles in relation to the humus layer

Gas concentration driven fluxes of nitrous oxide and carbon dioxide in boreal forest soil

Nitrous oxide (N2O) and carbon dioxide (CO2) fluxes were measured in a boreal forest during two growing seasons with soil gradient and chamber methods. N2O fluxes obtained by these two techniques varied from small emission to small uptake. N2O fluxes were of the same order of magnitude, however, the fluxes measured by the soil gradient method were higher and more variable than the fluxes measured with chambers. The highest soil gradient N2O fluxes were measured in the late summer and the lowest in the autumn and spring. In the autumn, litter fall induced a peak in N2O concentration in the organic O-horizon, whereas in the spring N2O was consumed in the O-horizon. Overall, the uppermost soil layer was responsible for most of the N2O production and consumption. Soil gradient and chamber methods agreed well with CO2 fluxes. Due to the very small N2O fluxes and the sensitivity of the flux to small concentration difference between the soil and the ambient air, the flux calculations from the O-horizon to the atmosphere were considered unreliable. N2O fluxes calculated between the soil A- and O-horizons agreed relatively well with the chamber measurements.

General description of the sampling techniques and the sites investigated in the Fennoscandinavian podzolization project

A 3-year project focusing on the fundamental processes of podzolization was carried out on three sampling sites in northern Fennoscandinavia. The soils were selected based on the previous information of the soil properties to represent typical soils in the area. In this article, the post-glacial history of the sites, site vegetation and general properties of the soils, as well as the methods used are presented. Two of the sites were classified as Typic Haplocryods and one as an Entic Haplocryod. The post-glacial age of the sites was between 9000 and 9500 years BP and the parent material was glacial till in one of the sites and glaciofluvial material in two of them.

Recovery of galactoglucomannan from wood hydrolysate using regenerated cellulose ultrafiltration membranes.

Hemicelluloses show promise as a renewable source of raw material for various industrial processes. In this study, galactoglucomannan was recovered from pressurized hot water extract of spruce-sawdust in two steps using hydrophilic regenerated cellulose ultrafiltration membranes having different molecular weight cut-off values. The first step was concentration of galactoglucomannan (GGM) by ultrafiltration using a flat sheet unit and the second step was purification of the retained galactoglucomannan by diafiltration using reverse osmosis filtered water. The highest GGM retention (88%), purity (63%) and recovery (70%) were achieved with the UC005 membrane (cut-off value 5-kDa) at a volume reduction (VR%) of 86%. The UC010 and UC030 membranes (cut-off values 10- and 30-kDa, respectively) partly separated xylan from GGM. Generally, diafiltration did not improve the purity of the GGM due to overlapping of the GGM and lignin molar mass distributions and the fact that most of free low molar mass lignin had already been removed in the concentration filtration step. However, by diafiltration, partial removal of xylan and complete removal of monosaccharides from the GGM rich concentrate was achieved.

An open chamber system for measuring soil surface CO2 efflux: Analysis of error sources related to the chamber system

An open dynamic chamber is a widely used method for soil CO2 efflux measurements. However, any uncontrolled air flow between the inside and outside of the chamber that is created by differences between the inflow and outflow rates can cause errors in soil CO2 efflux measurements. Estimates of these errors are reported here. A system was constructed in which compensation air of known CO2 concentration was introduced into the chamber and the CO2 concentration was measured in the outflow. The flows of air into and out of the chamber were controlled by two separate mass flow controllers, and the pressure difference between the chamber and the ambient air was measured. When the inflow was larger than the outflow, the measured efflux decreased, whereas when the inflow was smaller than the outflow, the efflux increased. With low fluxes this error was statistically significant when the difference between the flow rates was >30%. The difference between flow rates had a larger effect on efflux rates during high efflux than during low efflux. The effect of air mixing inside the chamber on the reliability of the efflux measurement was tested. Without sufficient mixing it was not possible to get stable efflux readings with this type of chamber technique. The open chamber measurements described here were also compared to closed static measurements based on syringe samples taken manually from the chamber. On average the CO2 efflux values measured with closed static technique were 11% lower than those measured with open dynamic method.

Response of fine roots to an experimental gap in a boreal Picea abies forest

We examined the initial response of the quantity and distribution of fine roots to the creation of an experimental canopy gap with a diameter of 50 m in a mature managed Norway spruce forest. Under the canopy, the fine root length densities of trees, shrubs, and grasses and herbs were 3207, 707 and 2738 m m−2, respectively. The fine root biomass of trees, shrubs, and grasses and herbs were 182, 47 and 52 g m−2, respectively. Two growing seasons after gap creation hardly any fine tree roots were found in the middle part of the gap. The living tree roots in the gap edge zone were mainly located within a 5-m distance from the standing edge trees. The indices developed here to show the influence of trees on fine root lenght density clearly revealed the effect of the vicinity of living trees on fine root lenght density. The root densities of grasses, herbs and dwarf shrubs did not show a clear response to gap creation despite the increase of their foliage. Our results suggest that in boreal spruce forests a gap disturbance creates a distinct tree root gap and that the gap edge trees do not extend their root systems rapidly into the formed root gap.

Near-saturated Hydraulic Conductivity and Water Retention in Coarse Podzol Profiles

There is little information available about the hydraulic conductivity of coarse podzol profiles where the vertical variation of the structure is considerable. The near - saturated conductivity of two coarse podzol profiles was measured by tension infiltrometer. The extrapolated saturated conductivity was 106.9 cm h- 1 in the very coarse sand and 16.7 cm h- 1 in the medium coarse sand parent soil, and decreased steadily upward, being between 0.7 and 1.3 cm h-1 in the two top horizons of these profiles. The unsaturated conductivities measured by the instantaneous profile method were in good accordance with the results of the tension infiltrometer, but the measurement range of the instantaneous profile method was rather narrow. The near - saturated hydraulic conductivity and water retention changed in both profiles in a systematic way, which agrees with the differences in matrix scale of structure as reflected in the measured soil textural and pedogenic properties.

The effects of soil and air temperature on CO2 exchange and net biomass accumulation in Norway spruce, Scots pine and silver birch seedlings

Soil temperature is proposed to affect the photosynthetic rate and carbon allocation in boreal trees through sink limitation. The aim of this study was to investigate the effect of temperature on CO(2) exchange, biomass partitioning and ectomycorrhizal (ECM) fungi of boreal tree species. We measured carbon allocation, above- and below-ground CO(2) exchange and the species composition of associated ECM fungi in the rhizosphere of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies K.) and silver birch (Betula pendula Roth) seedlings grown in soil maintained at 7-12, 12-15 and 16-22 °C. We found increased root biomass and photosynthetic rate at higher soil temperatures, but simultaneously with photosynthesis rate, higher temperature generally increased soil respiration as well as shoot, and root and rhizosphere respiration. The net CO(2) exchange and seedling biomass did not increase significantly with increasing temperature due to a concomitant increase in carbon assimilation and respiration rates. The 2-month-long growth period in different soil temperatures did not alter the ECM fungi species composition and the below-ground carbon sink strength did not seem to be directly related to ECM biomass and species composition in any of the tree species. Ectomycorrhizal species composition and number of mycorrhiza did not explain the CO(2) exchange results at different temperatures.