Pekka Tamminen

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.

Whole-tree harvesting at clear-felling: Impact on soil chemistry, needle nutrient concentrations and growth of Scots pine

Abstract The effects of logging residue removal on soil chemical properties and the needle nutrient concentrations and growth of Scots pine (Pinus sylvestris L.) were studied after clear-felling on two sites of different fertility in eastern Finland. Harvesting was carried out either conventionally, i.e. harvesting only the stems [conventional harvesting (CH)], or totally, i.e. harvesting all of the above-ground tree biomass [whole-tree harvesting (WTH)]. The seedlings were planted in ploughing tilts on 50×50 m sample plots. The number of replications was 24 on the more fertile site and 12 on the less fertile site. Compared with CH, WTH had no effects on either the survival or growth of Scots pine trees during the first 22 years. Apart from the statistically significant increase in needle nitrogen concentration in the WTH treatment on the less fertile site, the needle concentrations were not affected by the harvesting intensity. On the more fertile site, the total amounts of carbon, nitrogen and calcium, as well as exchangeable calcium and extractable phosphorus in the organic layer, were significantly lower on the WTH than on the CH plots. Although the pH remained unchanged, the exchangeable aluminium concentrations increased on the more fertile site, and on both sites the calcium/aluminium ratio was significantly lower on the WTH plots than on the CH plots.

Logging residue removal after thinning in boreal forests: long-term impact on the nutrient status of Norway spruce and Scots pine needles.

The aim of this study was to compare how conventional stem harvesting (CH) and whole-tree harvesting (WTH) in the first, and in some cases also in the second, thinning affect the needle nutrient status of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) stands in Finland. A series of 12 long-term field experiments was studied. The experiments were established during 1978-86. The effects of logging residue removal after thinnings on the needle nutrient concentrations were generally minor and without any overall trends, but there were differences between experiments. Trees tend to maintain their current needle nutrient concentrations at the same level by re-utilizing the nutrients stored in the older tissues and by changing C allocation in the whole tree. Thus, needle analysis should be combined with stem growth data in order to achieve a more comprehensive understanding of the effects of WTH on the nutrient status of trees.

Long-term effects of stump harvesting on soil properties and tree growth in Scots pine and Norway spruce stands

Abstract Effects of stump harvesting on the properties of surface soil and on the density, structure and growth of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) stands were estimated in a field trial in western Finland. The experiment was established in 1977 and measured in 2010. Stems and logging residues were harvested after clear-cutting, and stumps were lifted and removed from half of the experimental area. Sixteen plots were planted with pine seedlings and 16 with spruce. The main effects of stump harvesting were improved survival of planted trees and an increase in natural regeneration. No clearly negative effects were noted in the stand development. Stump harvesting had no or minimal effects on the properties of the organic layer and those of the 0- to 10-cm mineral-soil layer. Soil properties did not differ between tree species. Pine production was higher on plots with stump removal compared to plots without soil treatment.

Effects of whole-tree harvesting on growth of pine and spruce seedlings in southern Finland

Abstract The effects of harvesting logging residue on the survival and growth of planted Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst) seedlings and on number and growth of natural seedlings were studied at five sites in southern Finland. Trees were harvested either conventionally, i.e. harvesting only the stems, or harvesting all the aboveground tree biomass (WTH). One of the experiments had been planted with pine and four experiments with spruce 10 years ago. When the spruce experiments were analysed together, WTH had significantly increased the average number of planted seedlings, but had not affected basal area, stem volume or biomass of the planted seedlings. When both planted and natural seedlings were studied together, WTH significantly increased the average number of seedlings and the average total biomass of all tree species. In the pine experiment, WTH had no effect on stand or tree characteristics. In this study, within the first 10 years after reforestation, WTH did not have any negative effect in stand or tree characteristics that could be explained by nutrients removed with logging residue.

Tree Nutrient Status

A shortage of plant-available nitrogen is the most common factor restricting tree growth on mineral soils in the boreal forest zone (Kukkola and Saramaki 1983, Tamm 1991). The trees growing on mineral soils usually have a sufficient supply of other nutrients, apart from some localised exceptions. The assimilating tissues of trees are normally able to regulate their nutrient concentrations and to maintain a satisfactory balance between other nutrients and nitrogen by utilising the nutrients stored in the tissues (Linder 1995). However, a state of deficiency can be caused by a number of factors, the deficiency being either primary or secondary (Raitio 1991). A primary deficiency occurs when the substrate contains insufficient nutrients. A secondary deficiency takes place when there are sufficient nutrients in the substrate, but either nutrient uptake or transport is disturbed, e.g. as a result of structural damage caused by insects or frost (Raitio 1993).

Sampling and Laboratory Errors in Forest Soil Analysis

In connection with the soil survey of the national forest inventory plots in 1986–89, two sets of independent samples were collected on 14 sample plots in different parts of Finland. The organic and mineral soil (0–5, 5–20, and 20–40 cm) layers were sampled. All the samples were analyzed twice in the laboratory for exchangeable cations (BaCl2 extraction) and total nitrogen, and total elemental concentrations of the organic layer by dry digestion (550°C). The relative error tended to increase as the concentrations decreased, especially when the concentrations were close to the detection limit of the analytical equipment. High relative errors at low concentrations led to error distributions skewed to the right, justifying the use of a median instead of an arithmetic mean of these errors. The precision of the laboratory analyses appeared to be better than that of the field sampling, especially in the case of the mineral soil layers. On average, the relative errors in both the laboratory and the field tended to increase towards deeper soil layers.

Forest Condition in Relation to Environmental Factors

A decrease in forest vitality was observed over large areas in Central Europe in the late 1970’s. The deterioration in tree condition not only occurred in highly polluted areas close to industrial regions, but also in areas located at considerable distances from emission sources. The hypotheses put forward to explain the phenomenon claimed that the causal agents were either acidic deposition and the dissolution of soil aluminium (Ulrich et al 1979, Sverdrup et al 1994), gaseous pollutants (Krause et al 1986, Prinz et al 1985), nitrogen deposition (Nihlgard 1985) or nutrient deficiencies (Schulze 1988). It has subsequently been accepted that forest damage is a highly complex phenomenon, the effects of pollutants being connected to climatic factors, local growth conditions, selection of provenances, abiotic and biotic damage or to the history of forest use (Fuhrer 1990, Innes 1993, Landman and Bonneau 1995). According to one point of view, the direct effects of pollutants on forest condition can only be demonstrated in the environments of industrial areas (Skelly and Innes 1994, Kandier and Innes 1995).