Michael Starr

Decomposition and nutrient release from logging residues after clear-cutting of mixed boreal forest

Elevated dissolved carbon (C), nitrogen (N) and phosphorus (P) concentrations are frequently observed in surface water soon after clear-cutting of boreal coniferous forests. It has been suggested that they originate from the fine logging residues whose decomposition may be accelerated as a result of changes in soil temperature and moisture conditions. In the present study, the decomposition rate and release of C, N, and P from Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies Karsten) and silver birch (Betula pendula Roth.) logging residues (fine roots ∅≤2xa0mm, branches ∅≤10xa0mm and foliage) were investigated during three years with the litterbag method in a clear-cut area and in an adjacent Norway spruce dominated, mixed boreal forest in eastern Finland (63°51′xa0N, 28°58′xa0E, 220xa0m asl). The mass loss of the logging residues decreased in the order: foliage > roots > branches. Birch leaves were the only fraction that showed significantly higher losses of mass and C at the clear-cut plot than at the forest plot; otherwise there was no tendency for accelerated decomposition or mineralization at the clear-cut plot. After three years the initial C pool in the logging residues had declined by 33% and that of P by 49% but there was no net release of N as more N accumulated in roots and branches than was released from foliage. The results indicate that 1)xa0logging residues release relatively large and rapid fluxes of CO2 to the atmosphere 2)xa0are potential source of elevated P in surface waters soon after clear-cutting 3)xa0are not a net source of N immediately after clear-cutting.

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

Carbon and nitrogen pools in an old-growth, Norway spruce mixed forest in eastern Finland and changes associated with clear-cutting

Abstract The amount of carbon (C) and nitrogen (N) removed in stems after clear-cutting a forest in eastern Finland is compared with ecosystem pools (above- and below-ground tree and understorey vegetation biomass + organic layer +0–60 xa0cm mineral soil layer) and fluxes before clear-cutting. The tree stand was an old-growth mixed coniferous forest dominated by Norway spruce. The ecosystem pools of C and N before clear-cutting were 175xa0536 and 2848xa0kgxa0ha −1 , respectively. Most (62%) of the C was in living vegetation, mainly trees (60%), whereas most of the N pool was in the soil (80%). C and N pools in understorey vegetation were small ( −1 and that of N was 16.1xa0kgxa0ha −1 . The annual return to the forest floor as aboveground litterfall was 958xa0kgxa0ha −1 of C and 12xa0kgxa0ha −1 of N, corresponding to 48 and 75% of annual net uptake, respectively. During clear-cutting, some 239xa0m 3 xa0ha −1 of stemwood (overbark) were removed from the site, corresponding to 32% (C) and 3.0% (N) of the pre-harvest ecosystem pools; branches and foliage were left on site. The pool of C in living vegetation was reduced by 89% and that of N by 81% while the C pool in dead vegetation increased fourfold and that of N somewhat less. Our results indicate that clear-cutting will affect the C and N pools and fluxes of forest ecosystems significantly, even though some living trees are left on site.

Effects of forest clear-cutting on the carbon and nitrogen fluxes through podzolic soil horizons

Effects of clear-cutting on the dissolved fluxes of organic C (DOC), organic N (DON), NO3− and NH4+ through surface soil horizons were studied in a Norway spruce dominated mixed boreal forest in eastern Finland. Bulk deposition, total throughfall and soil water from below the organic (including understorey vegetation and, after clear-cutting, also logging residues), eluvial and illuvial horizons were sampled weekly from 1993 to 1999. Clear-cutting was carried out in September 1996. The removal of the tree canopy decreased the deposition of DOC and DON to the forest floor and increased that of NH4+ and NO3− but did not affect the deposition of total N (DTN, <3 kg ha−1 a−1). The leaching of DOC and DON from the organic horizon increased over twofold after clear-cutting (fluxes were on an average 168 kg C and 3.3 kg N ha−1 a−1), but the increased outputs were effectively retained in the surface mineral soil horizons. Inorganic N deposition was mainly retained by the logging residues and organic horizon indicating microbial immobilization. Increased NO3− formation reflected as elevated concentrations in the percolate from below the mineral soil horizons were observed especially in the third year after clear-cutting. However, the changes were small and the increased leaching of DTN from below the illuvial horizon remained small (<0.4 kg ha−1 a−1) and mainly DON. Effects of clear-cutting on the transport of C and N to surface waters will probably be negligible.

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

Canopy and Soil Retention of Nitrogen Deposition in a Mixed Boreal Forest in Eastern Finland

Nitrogen deposition, leaching, and retention were monitored in a mature spruce (Picea abies Karsten) dominated mixed boreal forest in eastern Finland. Bulk precipitation, throughfall, stemflow, and percolation through the podzolic soil profile were monitored from 1993 to 1996. Mean annual bulk deposition of total N was 3.83 kg ha-1, of which 33% was NH4+, 26% was NO3- , and 41% was organic N. Throughfall+stemflow flux of total N was 2.93 kg ha-1 yr-1. Sixty-four % of NH4+ and 38% of NO3- in bulk precipitation was retained by tre three canopy. Organic N was released (0.27 kg ha-1 yr-1) from the tree canopy. Nitrate-N was retained and organic N was leached as the water passed through the ground vegetation and soil O-horizon. Ammonium-N and organic N were retained mainly in the E-horizon. The output of total N from the E-horizon was only 5% of the total N deposition in the forest stand during the study period and it was mainly as organic N. The output of inorganic N forms from under B-horizon was seasonal and occurred mainly at spring snowmelt.

A Survey of Forest Soil Properties Related to Soil Acidification in Southern Finland

Parameters describing forest soil acidification status at 65 sites in southern Finland (61–63°N) are presented. pHaq ranges were: 3.6–5.5 (humus), 3.6–5.4 (0–5 cm), and 4.9–7.4 (60–70 cm). Exchange acidity and total acidity in the humus layer averaged 7.0 and 65.6 me 100 g−1, respectively. Corresponding values were 2.9 and 9.9 for the 0–5 cm layer, and 0.3 and 2.1 for the 60–70 cm layer. Aluminium (0.1 M BaCl2) accounted for 32, 81, and 61% of exchange acidity in the humus, 0–5 cm and 60–70 cm layers, respectively. For the same layers, average BaCl2 extractable Ca/Al molar ratios were 38, 1.5 and 11. Effective cation exchange capacity (BaCl2) averaged 27.8 me 100 g−1 in the humus layer and decreased from 3.8 to 0.6 me 100 g−1 down the mineral soil profile. Corresponding base saturation values were 77%, and 21 to 42%. Different types of soil with respect to acidification could be distinguished.

Responses of ground vegetation species to clear-cutting in a boreal forest: aboveground biomass and nutrient contents during the first 7 years

Rapid growth of ground vegetation following clear-cutting is important to site productivity because vegetation retains nutrients in the ecosystem and can decrease nutrient leaching prior to stand re-establishment. Aboveground biomass, nutrient contents (N, P, K and Ca) and species composition of ground vegetation were determined 1xa0year before and for 7xa0years after clear-cutting of a mixed forest dominated by Norway spruce [Picea abies (L.) H. Karst.] in eastern Finland. The biomass of the feather mosses [Pleurozium schreberi Brid. and Hylocomium splendens (Hedw.) B. S.& G.] and the dwarf shrubs (Vaccinium myrtillus L. and V. vitis-idaea L.), which had dominated the ground vegetation in the mature forest, significantly decreased after clear-cutting. However, with the exception of H. splendens, these species had recovered within 3–5xa0years. The biomass of Deschampsia flexuosa (L.) Trin. considerably increased soon after clear-cutting, and Epilobium angustifolium L. appeared 3–5xa0years after cutting. These species contributed to the retention of nutrients not simply because of their biomass but also because of higher nutrient concentrations in their tissues. Total biomass and nutrient contents of the ground vegetation exceeded those of the pre-cutting levels. The proportion of ground vegetation biomass and nutrient contents represented by mosses decreased after cutting, while V. myrtillus, although reduced after cutting, remained a marked nutrient sink. The results suggest that H. splendens is the most sensitive species to cutting, but the biomass of P. schreberi, V. myrtillus and V. vitis-idaea return to initial levels soon after clear-cutting as do the nutrient contents of ground vegetation.

Release of potassium, calcium, iron and aluminium from Norway spruce, Scots pine and silver birch logging residues

Potassium (K), calcium (Ca), iron (Fe) and aluminium (Al) release from Norway spruce (Picea abies Karsten), Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth.) logging residues (fine roots, foliage and small branches) were studied by means of litterbags over a period of three years in clear-cut area and adjacent uncut Norway spruce dominated mixed boreal forest in eastern Finland (63°51′xa0N, 28°58′xa0E, 220xa0m a.s.l) to determine the amounts and rates of release for these elements and to evaluate whether clear-cutting accelerates mineralization. Almost all K was released from logging residues already during the first year. Calcium was released from foliage and roots but accumulated in branches. Most of the roots Fe and Al content were released during three years while the absolute amounts of Fe and Al in branches and foliage generally increased with decomposition. The results indicate that mineralization is slightly accelerated as a result of clear-cutting since K from foliage and branches of all studied tree species and Ca from pine and spruce roots was released significantly faster at the clear-cut plot than at the forest plot. In three years the initial K pool in the logging residues declined by 90%, Ca by 8%, Fe by 55% and Al by 61% in the clear-cut area. These results indicate that Ca is retained a long time; but Fe, Al and in particular, K are soon released from logging residues. Fine roots of the logged trees release large amounts of Fe and Al and can significantly affect Fe and Al fluxes.

Heavy metal budgets for two headwater forested catchments in background areas of Finland

Mean annual (1994-1996) budgets for Cd, Cu, Ni, Pb and Zn at two background, forested catchments, VK and HJ, in Finland are presented. Budgets for plots (VK3, HJ1 and HJ4) included throughfall (TF), litterfall (LF) and soil leaching fluxes, and for catchments terrestrial retention and leaching and lake sedimentation fluxes. Total deposition (TD) loads were relatively low (Cd < 0.1, Cu < 2, Ni < 1, Pb < 3 and Zn < 5 mg m-2 year-1) and that even in these areas almost half of the TD was in the form of dry deposition. Retention of TD within catchments was > or = 77% for all metals, except for Ni at VK (54%). For Cu and Pb, the retention was 94-97%. Most of the retention (74-97%) took place in the terrestrial part of the catchment, lake sedimentation accounting for the remainder. Plot-scale soil leaching fluxes at 40 cm of Cd, Cu (VK3) and Ni (VK3) were greater (> or = 100%) than TD inputs. Most of the catchment retention must therefore have taken place either deeper in the soil or in the lowland peatland areas. The humus layer was particularly effective in retaining Cu and Cd (65-81% and 51-78% of total inputs to the forest floor (TF + LF)). The retention of Pb by the humus layer was less than expected (26-54% of TF + LF). Litterfall was a particularly important internal flux for Zn.