3. Doktoritööd
Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/7081
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Sirvi 3. Doktoritööd Autor "Bauhus, Jürgen (opponent)" järgi
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Kirje Growth development and ecology of midterm hybrid aspen and silver birch plantations on former agricultural lands(Eesti Maaülikool, 2017) Lutter, Reimo; Tullus, Hardi; Tullus, Arvo; Bauhus, Jürgen (opponent)During the recent decades, a novel land-use system called “short-rotation plantation forestry” has steadily expanded from southern regions to northern Europe. This tendency is mainly driven by the increasing demand for renewable energy resources like woody biomass and the pressure to reduce harvest in natural forests. Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) and silver birch (Betula pendula Roth) have proved to be among the most promising tree species for the intensive plantation forestry in Baltic Sea region on former arable lands. The current thesis makes a novel contribution to the long-term research and monitoring study about suitability of hybrid aspen and silver birch for the afforestation of former agricultural lands in Estonian conditions. Repeated-measurements of tree growth and physico-chemical soil characteristics were conducted in permanent sample plots in hybrid aspen (n = 51) and silver birch plantations (n = 11). Hybrid aspen and silver birch plantations height growth and stemwood production were two times greater than same-aged forestland birch and European aspen stands. The most suitable site types for both species were fertile Oxalis, Oxalis-Myrtillus and Aegopodium site types. Hepatica site type was less productive for both species. 15 years since afforestation, soil reaction decreased in A-horizon for both tree species, but generally fast-growing silver birch and hybrid aspen plantations have not depleted soil primary macronutrients. Soil available P and available water content were the main factors that had a growth-controlling effect on both tree species. Hybrid aspen plantations are C-sequestrating ecosystems already 15 years since afforestation of former arable lands. The main C sequestration in midterm hybrid aspen plantations was to above-ground biomass of trees. SOC pool changes in A-horizon depended from former land-use type, where SOC decreased in former grasslands, and remained unchanged in former cultivated cropland soils. The establishment of silver birch and hybrid aspen plantations offers a promising implementation for abandoned agricultural lands in terms of raw material production for the industry and climate change mitigation.