Andmebaasi logo

Sirvi Autor "Tullus, Arvo (advisor)" järgi

Nüüd näidatakse 1 - 3 3
  • Pisipilt
    Kirje
    The effect of planting stock and soil scarification on forest regeneration
    (Eesti Maaülikool, 2018) Jäärats, Andres; Seemen, Heino (advisor); Sibul, Ivar (advisor); Tullus, Arvo (advisor); Witzell, Johanna (opponent)
    The objective of the Doctoral thesis was to study and evaluate the quality of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L.) planting stock grown with different technologies, determine their biometric indices and conformity with set quality standards, assess the survival and height growth formation of Scots pine and Norway spruce plantations established with different types of planting stock, and analyse the natural regeneration of coniferous and deciduous trees depending on soil scarification. Novel aspects of the thesis include the first detailed survey of the growth of container plants produced with modern technology in Estonia, long-term monitoring of post-planting growth of different planting stock in multiple sample plots, and identification of different parts of the microsites formed as a result of soil scarification. The analysed planting stock originated from nurseries of the State Forest Management Centre, post-planting growth in experimental plantations was analysed with repeated measurements up to the age of eight years and the emergence of natural regeneration was determined in commercial forests. The duration of different research stages was 12 years. The comparison of planting stock revealed that bare-root Norway spruce plants had significantly larger dimensions (height, root collar diameter, above- and below-ground biomasses) than container plants. Bare-root Scots pine plants had greater root collar diameter and above-ground biomass than container plants but slightly lower height and similar below-ground biomass. The survival and post-planting growth of Scots pine in forest stands did not depend on the initial height or stock type. Post-planting growth of Norway spruce was positively correlated with initial height. Initial height and stock type had no direct influence on the survival of Norway spruce trees in a forest. The height increment of Scots pine container plants was significantly greater during the first 2-3 years after planting, however this difference levelled out at older age and due to greater initial height of bare-root plants there was no difference in average height of the two stock types during eight growing seasons. The growth of Norway spruce container plants remained somewhat lower during the study period although the absolute height difference was small. Soil scarification had a positive effect on the emergence of both pine and spruce natural regeneration, whereas no effect on the abundance of deciduous trees was observed. To conclude, successful reforestation can be achieved with modern coniferous planting stock produced in Estonia with no major differences between the stock types, which gives an advantage to more easily produced and handled container plants. Soil scarification and favourable site conditions combined contribute to successful natural regeneration of conifers in suitable site types.
  • Pisipilt
    Kirje
    Growth development and ecology of midterm hybrid aspen and silver birch plantations on former agricultural lands
    (Eesti Maaülikool, 2017) Lutter, Reimo; Tullus, Hardi (advisor); Tullus, Arvo (advisor); 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.
  • Pisipilt
    Kirje
    Management of second-generation hybrid aspen stands and its environmental impact
    (Estonian University of Life Sciences, 2025) Hepner, Heiki; Lutter, Reimo (advisor); Tullus, Hardi (advisor); Tullus, Arvo (advisor); Institute of Forestry and Rural Engineering; Bergström, Dan (opponent)
    ABSTRACT. In short-rotation forestry in Northern Europe hybrid aspen is used as a preferred tree species. It is important to understand the effects of thinning on second-generation hybrid aspen stand growth, biomass production, soil fertility, nutrient accumulation in the above-ground parts of trees, carbon balance, and economic profitability. After the first growing season, the average stand density was 94,000 trees/ha. After five growing seasons, trees in the control area had produced an average of 31.4 t/ha of dry biomass, resulting in an average annual production of 6.3 t/ha. On the corridor and cross-corridor thinning areas, the total biomass after five years was lower compared to the control area, but when considering also the biomass harvested with thinning, there was no significant difference. The intensive pre-commercial thinning using the single-tree selection method can cause slower stand growth and further self-thinning. After five years, the change in carbon stock was positive in the control and corridor treatment areas, while it remained neutral in the cross-corridor treatment area. Carbon stock increased in the aboveground biomass but decreased in the soil. Soil fertility indicators showed varied changes. With very short coppice cycles, nutrients accumulated in biomass make up less than 10% of the total stock, except for potassium. In the case of a very short coppice cycle, the harvest should be done when the trees are dormant. When growing logs and pulpwood, the very intensive first thinning should be avoided. With low expected economic return (discount rate of 1%), the single-tree method proved most effective. Under moderate expectations (5% discount rate), the corridor method yielded the best outcome. For high and very high return expectations (10% or 20% discount rates), the focus should be only on energy wood. In summary, hybrid aspen regenerates vegetatively very well, and provides flexible management options and economic profit in Estonian conditions.