Eva Ring

Short-term Effects of Clear-cutting on the Water Chemistry of Two Boreal Streams in Northern Sweden: A Paired Catchment Study

Abstract The effects of clear-cutting on stream-water chemistry in northern Sweden remain largely unexplored. Here we report data collected during a reference period and the first two years after logging in two typical partially harvested northern catchments; the objective was to compare water chemistry along the stream with and without a forest buffer. Two typical uncut reference catchments are included for comparison. Runoff was measured at the outlet of each catchment, and water samples were generally taken every second week and analyzed for 20 constituents. Logging resulted in increased runoff and increased concentrations of sodium, potassium, chloride, total nitrogen, total phosphorus, and suspended material from both catchments. Nitrate (NO3−) leaching increased only from the catchment without a forest buffer. It has not yet been possible to evaluate fully the effects of the forest buffer on the NO3− leaching because the uphill clear-cut area leached minimal amounts of NO3−.

Forest Harvest Increases Runoff Most during Low Flows in Two Boreal Streams

Abstract To understand how forest harvest influences the aquatic environment, it is essential to determine the changes in the flow regime. This paper presents changes in the hydrological regime during the first 2 y after harvest in two catchments of the Balsjö Catchment Study in Sweden. The changes were judged relative to a reference catchment, calibrated during an 18-mo pretreatment period starting in September 2004. From August 2006 through March 2008, there was an average of 35% more runoff from the harvested catchments relative to the reference. The flow increased most during the growing seasons and at base flows (<1 mm d−1; 58–99% increase), followed by dormant season and intermediate flows (30–43%). No significant changes were observed during the highest flows (over 5 mm d−1), except for the spring flood a few weeks after harvest, which was delayed and attenuated. Large relative changes in low flow may influence the ecosystem by altering the aquatic habitat.

Nitrogen losses and soil water acidity after clear-felling of fertilized experimental plots in a Pinus sylvestris stand

Abstract Studies of losses of nitrogen to water and air (denitrification) were performed during 3 years following a clearcut of a previously heavily fertilized Pinus sylvestris stand. During a 20-year period prior to the harvest, plots had been fertilized three times with different doses of ammonium nitrate (0–600 kg N ha−1 each time). Soil studies conducted during the last summer before clearcutting showed that the soil nitrogen pool had almost doubled in some plots. Organic nitrogen was the dominant nitrogen fraction in the soil water in most plots. This fraction was independent of the fertilizer dose. Before harvesting and during two subsequent years, nitrate only occurred at the plots which had received the maximum dose (3 × 600 kg N ha−1). The concentrations of the different nitrogen fractions in soil water tended to decrease on all plots from pre-clearcut conditions during the first 2 years. During the third year, which had normal precipitation, increases in nitrate were recorded at the plots with the three highest doses. This was the case especially for the highest dose, for which the concentration rose from 0.24 mg nitrate-N l−1 in the previous year to 2.2 mg l−1. The results as regards the effect of the clearcut on soil water pH were somewhat contradictory, but a minor pH increase was indicated. Before clear-felling there was no correlation between pH of soil water and fertilizer dose. During the years following the clearcut, pH was negatively correlated with dose. The reason for these changes could not be explained solely by nitrification. Losses of N2O-N were estimated to be less than 0.1 kg ha−1 year−1 during the first 2 years after clearcut. Denitrification measured with the acetylene block technique revealed no higher values, pointing to an insignificant N2 loss. The losses were independent of the previous fertilizer dose. Despite a huge build-up of the nitrogen storage from previous fertilizations, nitrogen losses to water and air were insignificant during the first 2 years after the harvest. During the third year, which was wetter than the two previous years, increased nitrate concentrations were recorded for the highest dose for the first time. Owing to the cold site and the low precipitation for 2 years after the clearcut, further measurements will be necessary before more definite conclusions can be made.

Is the Water Footprint an Appropriate Tool for Forestry and Forest Products: The Fennoscandian Case

The water footprint by the Water Footprint Network (WF) is an ambitious tool for measuring human appropriation and promoting sustainable use of fresh water. Using recent case studies and examples from water-abundant Fennoscandia, we consider whether it is an appropriate tool for evaluating the water use of forestry and forest-based products. We show that aggregating catchment level water consumption over a product life cycle does not consider fresh water as a renewable resource and is inconsistent with the principles of the hydrologic cycle. Currently, the WF assumes that all evapotranspiration (ET) from forests is a human appropriation of water although ET from managed forests in Fennoscandia is indistinguishable from that of unmanaged forests. We suggest that ET should not be included in the water footprint of rain-fed forestry and forest-based products. Tools for sustainable water management should always contextualize water use and water impacts with local water availability and environmental sensitivity.

Nitrogen leaching before and after clear-felling of fertilised experimental plots in a Pinus sylvestris stand in central Sweden

Abstract Nitrogen leaching before and after clear-felling of experimental plots in a previously nitrogen fertilised Pinus sylvestris stand in central Sweden was estimated by two methods. The main difference between the methods was the estimation of the water flow, which was either simulated by a physically based computer model, SOIL, or calculated from runoff measurements performed by the Swedish Meteorological and Hydrological Institute in the Ljusnan River. Nitrogen leaching was calculated either from the nitrogen concentration in the soil water at 50 cm depth and the simulated vertical water flow, or by multiplying the annual mean nitrogen concentration in the soil water with the annual runoff in the Ljusnan River. Both methods produced similar results. Leaching was estimated from plots treated with ammonium nitrate over a 20 year period at a total rate ranging from 360 to 1800 kg N ha−1, from control plots and from forested reference plots in the adjacent stand. In the year before clear-felling, nitrogen leaching was only enhanced in the 1800 kg N ha−1 treatment, from which the leaching was 3–5 kg N ha−1 compared with about 1 kg N ha−1 from the forested reference and control plots. In the second year after clear-felling leaching was about a third of that before clear-felling, owing to low precipitation and, hence, runoff. Leaching was still only enhanced at the highest fertiliser rate. In the fifth year after clear-felling, leaching tended to increase in all treatments including the control. The additional nitrogen leaching was mainly made up of nitrate. The accumulated nitrogen leaching during the first 5 years following clear-felling was roughly estimated at 2–3 kg N ha−1 for the forested reference plots, the clear-cut control and the 360 kg N ha−1 treatment, 4–5 kg N ha−1 for the 720 and 1080 kg N ha−1 treatments, 14 kg N ha−1 for the 1440 kg N ha−1 treatment and 37 kg N ha−1 for the 1800 kg N ha−1 treatment.

Effects of previous N fertilizations on soil‐water pH and N concentrations after clear‐felling and soil scarification at a Pinus sylvestris site

The study describes effects of clear‐felling and soil scarification on the N concentration and pH of soil water in experimental plots previously supplied with different doses of N. The experiment is situated in central Sweden in a former Pinus sylvestris L. stand. Over a 20‐yr period, plots were fertilized three times with ammonium nitrate, resulting in total doses of 360, 720, 1080, 1440 and 1800 kg N ha‐1. Soil water was sampled at a depth of 40–50 cm using suction lysimeters, and analysed for N and pH. The study covers one growing season before clear‐felling and six and four growing seasons after clear‐felling and soil scarification, respectively. Statistically significant (p < 0.05) elevations in total N and nitrate‐N concentrations were noted in the fourth to the sixth growing seasons after clear‐felling in the plots that had received 1800 kg N ha‐1, and in the fifth and sixth seasons in the plots that had received 1440 kg N ha‐1. Ammonium‐N concentrations were not significantly affected. After clear...

The distribution of logging residues and its impact on seedling establishment and early plant growth in two Norway spruce stands

ABSTRACT In Fennoscandia, logging residues (LR) are increasingly being harvested to provide fuel for renewable energy. However, the removal of LR is thought to lead to decreased growth in the next generation of trees. The effect on tree growth has generally been obtained by comparing the total removal of residues with retained residues spread evenly on the ground. With current clear-cutting practices, residues can be left with different spatial distributions, confounding the effects of residue removal. Field experiments were, therefore, established at two Norway spruce sites, comprising six treatments with varying distributions and volumes of residues. Before planting seedlings, the sites were disc-trenched. At one of the sites, seedling survival was significantly lower when all residues were removed immediately. At both sites, after 10 years there were statistically significant growth losses after removal of residues. There were no differences in plant growth if the residues were concentrated in small heaps and strings, simulating the normal distribution of LR following stem-only harvesting, compared with residues left evenly spread on the ground. To determine the duration of the observed growth effects, these study sites must be monitored more long term.

Water chemistry following wood-ash application to a Scots pine stand on a drained peatland in Sweden

Abstract The availability of phosphorus and potassium often limit growth of trees on well drained peatlands in the boreal region. Wood ash, which contains phosphorus and potassium, can be used for forest fertilization on peatlands or for nutrient compensation following intensive harvesting. This study was performed in order to investigate the effects on water chemistry of applying wood ash to a Pinus sylvestris L. stand on a drained peatland in southern Sweden. Runoff chemistry was monitored in the main ditch for one year before and three years after the application of self-hardened and crushed wood ash, applied at an average rate of 3.1×103 kg per hectare. In addition, groundwater was collected from the ash-treated peatland and from an adjacent reference peatland and chemically analysed. Shortly after woodash application, the concentrations of boron, calcium, potassium, lithium, magnesium, manganese and sulphate in the ditch water, and the electrical conductivity, all increased. Some variables showed elevated concentrations for a few months only, while pH and the concentrations of boron, potassium, lithium, magnesium, manganese, total phosphorus and silica were significantly (p < 0.05) elevated over the last one and a half or two years of the study, compared to the reference period. The concentrations of iron, total sulphur and sulphate were lower during the last one and a half or two study years than in the reference period. Several trace metals and anions did not appear to be affected. In general, the effects detected in groundwater were consistent with those found in ditch water. Groundwater flow through superficial soil layers seems to have facilitated leaching

Impacts of off-road traffic on soil physical properties of forest clear-cuts: X-ray and laboratory analysis

ABSTRACT Due to the great year-round demand for forest products, off-road forestry traffic occurs even when the ground is susceptible to soil compaction and rutting. We investigated the impacts of repeated passes with a laden forwarder (34 Mg) on the soil physical properties of two clear-cuts on stony till soils in northern Sweden. Core samples (n = 71) were collected from the top 5 cm of mineral soil in and beside wheel tracks, after six passes with the forwarder. Soil physical properties were quantified using classical soil physical analyses and X-ray tomography. The hydraulic conductivity was 70% lower in the wheel tracks than in the soil beside. The X-ray image analysis indicated that this was due to the smaller total volume and lower connectivity of structural pores (φ > 60 µm). Total porosity was 24% and 12% lower in the tracks at the two sites respectively, and mean bulk density was 1.39 g cm−3 in the tracks, compared to 1.13 g cm−3 beside them. To conclude, traffic changed the soil physical properties in a way that may lead to longer periods of high water content in the wheel tracks, increased risk of surface runoff and insufficient aeration for optimal seedling growth. GRAPHICAL ABSTRACT

Soil and soil-solution chemistry after burning a clear-felled area in boreal Sweden

Abstract In Scandinavian forestry, prescribed burning is carried out to promote biodiversity. This study was initiated to examine how burning of a clear-felled area affected the soil and soil-solution chemistry in a nitrogen-limited coniferous forest in boreal Sweden. The stand was clear-felled and the logging residues were left on site. The harvested area was divided into two parts: one part was burnt within three months after clear-felling while the other part was left as a control. Soil and soil-solution samples were collected before and after felling and burning. In the FH layer, pH and the concentration of K and P tended to increase immediately after burning. Six years later, only small effects on soil chemistry were indicated, but the N concentration in the FH layer appeared lower in the burnt area even after 11 years. In the deep soil solution, the total organic carbon concentration was lower in the burnt area than in the unburnt area. The -N concentration in the burnt area peaked at 0.50 mg l−1 and the mean concentration during the first seven seasons was 0.13 mg l−1. In the unburnt area, the -N concentration peaked at 3.1 mg l−1 and the corresponding mean concentration was 1.0 mg l−1. Although the general level of -N was low in this study, burning largely counteracted the increase in -N concentration that usually follows final felling.