In Finland, there is a desire to extend the planting season from spring and early summer to autumn, and to use the closed cardboard box storage method for both dormant and non-dormant seedlings. This thesis examined the effects of planting practices and the growing environment on the early performance of boreal container seedlings, and specifically: i) What are safe durations for the field storage of non-dormant Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) seedlings in closed cardboard boxes and open tray storage for different planting seasons (I); ii) How planting success differs in one-year-old spring, summer, and autumn plantings of Norway spruce and Scots pine in practical forestry (II); iii) How the planting depth and/or planting season affect the early field performance of small-sized silver birch (Betula pendula Roth) and Scots pine container seedlings (III) and iv) How warmer growing conditions affect the growth and emissions of biogenic volatile organic compounds in boreal seedlings in a controlled field experiment (IV). Non-dormant conifer seedlings can be stored in closed boxes for three days in August and a week in May, September, and October, whereas for open-stored seedlings the duration is a couple of days longer (I). Norway spruce plantings can be successful from spring to autumn if seedling storage, duration, and planting instructions are followed carefully. In Scots pine, it is still recommended to plant seedlings only in spring and early summer due to the higher failure risk (II). Deeper planting (60-80 % of shoot underground) may also enhance the early field performance of small-sized seedlings (III). Silver birch might benefit more from climate warming compared to conifer seedlings (IV). To ensure forest regeneration success with boreal tree species, recommendations for seedling materials, storage, and planting practices in different planting seasons should be carefully followed.
Tropical peatlands of South East Asia are major hotspots of biodiversity and great carbon stores. The main peat forming ecosystem is tropical peat swamp forest (TPSF) growing on top of meters deep peat. Forest degradation by vast scale land conversions and consequent pernicious impacts on the environment have raised an urgent need for conservation and restoration. This dissertation concentrates firstly on the peat soil properties, ground surface microtopograhy and vegetation patterns of the natural TPSF, and secondly on the vegetation restoration, i.e. reforestation of degraded tropical peatland.
In the studied natural TPSF type, the forest floor can be characterized as an irregular continuum of less common hummocks and more abundant flat low-lying surface where most of the peat surface is not inundated for most of the year. Unlike in the boreal and temperate peatlands, the ground surface microtopography had no regular patterning. The surface peat structure and chemistry had differences in relation to the surface microtopography. Higher surfaces had higher nutrient concentrations and saplings and trees were concentrated on higher surfaces whereas seedlings emerge in all ground surface elevations.
In the open degraded former TPSF area we tested 21 native tree species for their potential for reforestation in a planting experiment. We increased the knowledge on the species’ early stages flood and drought tolerances, species’ suitability for different conditions in reforestation areas and suitable species-specific seedling height for planting. For five species with known potential for reforestation purposes we tested the impact of three site preparation treatments, weeding, fertilizing and mounding, on the seedling performance. We analyzed also the effects of wildfires which caught the study area two years after planting.
With increased knowledge on both natural TPSF ecology and the seedling experiments on degraded areas, we could specify environmental condition requirements for several tree species for reforestation.
The demand for mechanized tree planting is expected to increase in the future. This dissertation assessed mechanized tree planting in Finland and suggests ways to improve its current productivity. The work on which this thesis is based was described in five peer-reviewed articles (I–V) addressing four specific research questions (SQs) that focus on productivity and cost-competitiveness, automation, capacity utilization, and the quality of planting work.
While productivity of mechanized planting is higher than manual methods, it is not yet cost-competitive. However, increasing efficiency by skilled operators and worksite selection make it possible for mechanized planting costs to remain lower than those of excavator spot mounding followed by manual planting. Increasing productivity and reducing operating costs are possible with an effective automatic seedling feeding system, although the Risutec APC is not yet sufficiently developed to reach that goal. Planting machine capacity is underutilized and could be utilized more effective to enhance productivity and cost-efficiency. Technical availability of planting machines in Finland is good, and the quality of mechanized planting work is high. Optimization and integration of the entire mechanized planting chain from the nursery to outplanting is important to minimize total cost.
In summary, for mechanized planting to be effective the following criteria must be satisfied: machine reliability; highly-skilled machine operator; suitable worksite; seedling quality, availability, and supply to worksite. In the future, it is important to continue developing new and existing machines to enhance productivity, e.g., by continuously working planting machines.