According to a Swedish study, the nutrient content of the water and the amount of greenhouse gas emissions from the forest ecosystem increased after the ditches were closed. However, after cleaning the ditches, one might find the opposite.
Researchers at the Swedish University of Agriculture, led by Hjalmar Laudon, studied the short-term effects of closing ditches and cleaning them on soil water levels, soil water quality and ditch water quality leaving areas and on carbon sequestration in the soil. forest. For comparison, they used ditches in the same area that had not been closed or cleaned, writes Estonian University of Life Sciences researcher Jürgen Aosaar.
As an expected result, the water level in the soil increased after the ditches were closed and decreased after the ditches were cleaned. Compared to areas where the ditches were left intact, levels of dissolved organic carbon, nitrogen, phosphorus and mercury in the water increased after the ditches were closed. However, after cleaning the ditches, the same indicators decreased.
The changes in the nutrient content of the water were statistically reliable. However, it should be kept in mind that they show short-term effects and that long-term trends require continuous observation. The amount of suspended matter in the water was not changed by closing the ditches or cleaning them.
Drained peaty soil in Estonia, the fertility of which is demonstrated by the growth of nettle and other plant species requiring nutrients. Water shimmers at the bottom of the hole, which without the ditch would be much closer to the ground. Author: J. Aosaar
Laudon and his colleagues also learned that the drained areas were sinks of carbon dioxide and methane. However, areas where the ditches were closed became emitters of such greenhouse gases the following year. However, the authors of the work point out that such changes could be short-term and the situation could reverse after a few years. The results may also have been influenced by the fact that in the areas where the ditches were closed and cleaned, deforestation was carried out, after which the roots of the trees in the ground began to rot.
Around a million kilometers of ditches have been dug in Swedish forests and, according to the working group, a comprehensive approach will be necessary for their future management. Laudon and his colleagues point out that when changing the existing situation, i.e. closing ditches and changing the hydrological state of the area, one must remember why the drainage system was built in the first place. This was done to drain excess water from the soil and improve forest growth.
According to the researchers, therefore, it is necessary to acquire more knowledge in this regard before making high-impact management decisions, i.e. closing the ditches. There is currently a lot of ignorance on this topic, Laudon and his colleagues admit.
The custard apple, productive for about 40 years, grows on peaty soil, whose water from the upper layers has been drained via ditches. This is how the swamp became a desolate swamp, which accounts for almost 16% of Estonian forests. When the ditches are closed, the water level in the ground rises and the trees growing in them die Author/source: Jürgen Aosaar
Since the study area was measured only one year after the trenches were closed and cleaned, the current results reflect the short-term effects of the works. Areas need to be monitored further to understand long-term effects. The authors of the work also say that in long-term drained areas, ecosystems may have changed to such an extent that it is impossible to return them to their previous state.
A group of researchers led by Hjalmar Laudon conducted the study at the Trollberget test site, which is located near the city of Umeå in the northern part of Sweden. In the studied area, ditches were built at the beginning of the last century and in the 1930s.
In the studied area there are nutrient-poor open peat bogs, as well as spruce and pine trees growing on loess, loess and peat soils. The depth of the ditches in the area was on average half a meter and the width in the upper part was almost one metre. The trenches were filled with peat taken from the site and trees cut from the same area.
The study was published in the journal Scientific Reports.
2023-12-19 09:42:00
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