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PAPEĻU (POPULUS SPP.)STADĪJUMU IERĪKOŠANA UN APSAIMNIEKOŠANA

Šēnhofa; S.; Lazdiņa; D.; Jansons; A.

Application of renewable materials such as wood in construction, production of furniture, and for other purposes including energetics is a crucial tool for mitigation of climatic changes and reduction of air pollution. In this respect, plantations of poplar with rotation period of 15–20 years for timber and 5 years for woodchip production, are boosting the volume of renewable resources in Europe. Such plantations can also have significant effect in balancing of flow of conventional (forestry) wood resources, which are affected by socioeconomic and environmental factors. Under Latvian climate, rotation period shorter than 20 years can be achieved only by Populus (poplar and aspen) hybrids. The establishment of such short rotation plantations becomes more popular also as the frequency of various natural disturbances, such as wind, increases. The increasing application of poplars can also be related to the desire of landowners to get profit from investments in tree plantation during their life.The first poplar plantations in Latvia were established at the beginning of the 20th century. However, since the middle of the 20th century interest in them has almost disappeared. Research in this area was resumed only in the 21st century. This monograph summarizes the results obtained in the second decade of 21st century in Latvia and provides practical recommendations for establishment of poplar plantations. Specifics of establishment and management of poplar plantations, quality and potential productivity of the reproductive material, as well as the main environmental interactions are presented. New data on the height increment of cuttings of different length during the first growing seasons are presented, concluding that longer cuttings are favourable for areas with higher risk of overgrowth by competing vegetation. Analysis of radial increment showed that the maximum width of annual rings was reached at the age 10–15 years, rapidly decreasing after the age of 20 years, thus suggesting final harvest age of the plantations. The monograph presents information on the long-term (65 years old trees) effect of climatic factors on radial increment of poplar hybrids. The set of climatic factors affecting increment of poplars differs from that affecting growth of native tree species (Norway spruce, silver birch). Poplars are susceptible to moisture deficit at the end summer, especially in combination with high temperature, which affect increment (ring width) in both the current and the following year. Narrower annual rings are caused also by the fluctuations of air temperature in late summer (August–September), likely indicating frost damage. The growth rate for poplars in September is only slightly lower than in the June–August period (10–15 mm per day). Rapid drop in temperature immediately after mid-September, especially in frost prone areas (like relief depression), leads to frost damages of shoots of the fast-growing poplar clones. Cumulative effect of the growing conditions determines the biomass of trees. Biomass allocation differs regionally, therefore local above-ground biomass equation are important. Such equations for poplars in Latvia are presented in this monograph. Compared to aspen, poplar allocates relatively small proportion of biomass to branches (ca. 10%), thus aiding for higher volume of more valuable sentiments (e.g., saw logs) and higher yields. Overall, the results confirm increasing potential for a wide application of poplar hybrids for establishment of plantations, both on lands unsuitable for agriculture, as well as on forest lands.

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