Formation and Dynamics of the Biotope of Pine Plantations on Peat Soils after Irrigation Improvement

Abstract

Wetlands in the Russian Forest Fund occupy more than 12 % of the country’s territory exceeding 100 mln ha. These are primarily afforested swamps with low-quality forest stands. A significant part of raised bogs is generally forestless. Meanwhile, about 60 % of the eutrophic and mesotrophic swamps are potentially rich. Here, only excess of water interferes with successful forest growth. The world forestry has accumulated wide experience in regulation of soil water retention through irrigation improvement and drainage. In Russia there are classic examples when stands of the 1st quality class grew in the large (several thousands of hectares) areas after irrigation improvement. One such case is the Kheynovskoye swamp with an area of over 2 ths. ha located in the Lisino training and experimental forest of the Saint-Petersburg State Forest Technical University and drained in 1847. However,  there are enough cases of unsuccessful drainage. The better half of the drained swamps before drainage were grown over with forests. Irrigation improvement has turned around the growth conditions of all stands existed before drainage, but in poor eutrophic swamps forest growth is insufficient. The research purpose was to study brand new stands in the drained territory taking into account the whole formation cycle of the biotope and its change with time. In order to get that done, a pilot plot was laid out on a eutrophic-mesotrophic treeless peat, where drainage was carried out using a frequent network of small grooves (furrows). They were dug with the help of a double moldboard (trench digger) and directed into the channels of the drainage network, thus providing for constant water drainage. Forest plantations were laid out on the layers formed along the furrows with the participation of the author. We had been assessing changes in the stand condition each 5–10 years for almost 60 years. The studies have shown that in the first years after removal of excess water and better soil warming, sedimentation and depletion of peat occurred. At a depth of 0.4–0.5 m in 20 years after planting the trees, the depth of peat decreased by almost 2 times. The living ground cover has changed under the influence of drainage and the developed stand. The initial (swamp) type of soil formation was replaced with soddy soil. High-quality heavyproducing plantation was formed. When comparing the parameters of the created artificial plantation with the stands of natural origin according to the growth course tables, it was found that the stock of the created stands at the age of 50 is almost twice higher than the stock of natural stands. It can be assumed that when growing wood pulp for its intended purposes in 100 years two yields can be harvested. Changes in peat soil have taken place during the last 50 years. The carbon (C) content decreased and the total nitrogen (N) content increased due to the intensive decomposition of peat, as evidenced by the decrease in the ratio of C:N. Structure developed in peat soil. The beginning of podzol-forming is noticed. Probably, the actual and hydrolytic acidity have increased due to the needle litter.
For citation: Babikov B.V., Subota M.B. Formation and Dynamics of the Biotope of Pine Plantations on Peat Soils after Irrigation Improvement. Lesnoy Zhurnal [Russian Forestry ournal], 2020, no. 4, pp. 27–39. DOI: 10.37482/0536-1036-2020-4-27-39