Current issue: 56(2)
Under compilation: 56(3)
Stand precipitation and stemflow studies became necessary in connection with hydrologic studies, for instance, to explain the deviations resulting from rains in the ratios between the water content of peat and the groundwater level, throughfall during rains of variable heaviness, and effect of stand treatment on soil moisture level. In this project the distribution of rainfall in stands differing in species composition and density was studied in Central Finland in 1963–1965 in fifteen stand precipitation sample plots. In addition, rain gauges were situated under individual Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.) and birch (Betula sp.) trees.
The average precipitation in the open was 4.8 mm, the corresponding precipitation in the stand was 77% for birch, 71% for pine and 62% for spruce. Measurements of stemflow from individual sample trees showed that less than ¼ mm (about 1.5%) during a 15 mm rain in a pine stand. In the spruce stands stemflow is negligible. A part of the sample plots was in drained peatlands with a dense vegetation of small shrubs. The shrub layer retention was about 10% even during heavy rain. In a small forest clearing, the bordering effect of the forest was seen up to the distance of 5 metres from the edge of the forest. During the period of study, on an average 3% more precipitation was recorded in the clearing than in the open, the difference being probably due to the stronger wind effect in the open.
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The aim of the study was to assess the contents and quantities of macronutrients reaching the ground with precipitation, stemflow and throughfall in Scots pine (Pinus sylvestris L.) stands growing on drained peatland, one of which was unfertilized and two of which had been fertilized three growing seasons before the measurements were carried out.
According to the results, the quantities of nutrients reaching the ground with precipitation were relatively large as compared, for example, with those removed with the stem wood carried away from the forest in logging. The nutrient most exposed to leaching from the canopy is potassium. Both the content of potassium in rainwater penetrating the canopy and the quantities reaching the ground are highest in stemflow, decreasing when moving from under the tree crowns toward the edge of the crown projection and into openings in the canopy. The results for phosphorus were similar, although not as clear as for potassium.
The contents of NO3-N were smaller in stemflow than in precipitation. The results did not support assumptions according to which nitrate nitrogen is leached from the canopy or is taken up by the canopy from precipitation. In the case both of precipitation and of throughfall and stemflow, the quantities of nitrite nitrogen recorded were smaller than the degree of precision applied in the determinations carried out (0.01 mg/1). The contents of NH4-N were on average higher in stemflow and throughfall than in precipitation.
Fertilizer application (600 kg/ha of N-P2O5-K2O, 14-18-10) increased the contents of potassium in stemflow and throughfall. A slight increase in phosphorus was also observed. Leaching of inorganic nitrogen was not affected by fertilization.
The PDF includes a summary in Finnish.