Viktorija Vendiņa

This review evaluates the current state of knowledge on the use of wood fibres and related woody materials as partial substitutes for peat in substrates used for forest nursery production, with particular emphasis on container seedlings. The review was prepared as a structured narrative synthesis of the available literature, focusing on substrate composition, physical and chemical properties, tree seedling growth, root development, water regime, fertilisation, operational handling, economic aspects and remaining research needs. The available evidence shows that wood fibres are technically promising components of peat-reduced growing media, but their performance depends strongly on the raw-material origin, processing method, substrate proportion, tree species, and cultivation management. The most reliable results have been obtained with partial substitution systems, whereas peat-free solutions remain species-specific and require careful optimisation of irrigation, nitrogen supply, pH control, and substrate quality. Although wood-based materials may improve resource efficiency and, under favourable local conditions, reduce substrate costs, wider implementation is constrained by variable material quality, limited standardisation and insufficient operational-scale validation. The main remaining research need is to define species-specific application thresholds and management protocols and to link nursery performance with outplanting success and full production economics under commercial conditions.

Sand extraction drastically alters ecosystem structure and initiates conditions for primary succession development. Forest stands aged 9, 16, 19, and 28 years were surveyed to assess understory vegetation and epiphytic lichen communities in post-mining sand and gravel quarries in eastern Latvia. Community structure and functional traits were analyzed. Younger stands (9–19 years) exhibited the highest understory species diversity, dominated by hemicryptophytes, open-habitat grasses, and low-to-moderate ecological value lichens, while older stands (28 years) supported high-value epiphytic lichens and understory species typical of oligotrophic boreal forests. In 9-year-old stands, high-value epiphytic lichens comprised, on average, 5.7% (SE = 1.6) total lichen cover, while in 28-year-old stands it was 24.8% (SE = 1.9). Species with animal-mediated seed dispersal were more prevalent in younger stands, reflecting indications of animal presence based on vegetation composition and observed animal damage on trees. No invasive species were recorded, likely due to quarry isolation (≥1 km closest edge of the forest ecosystem) and proximity to mature forest margins. Our results highlight the multidimensionality of biodiversity by integrating two taxonomic groups and indicate high potential for passive natural regeneration toward Western Taiga 9010 habitat conditions under an oligotrophic environment.

The conversion of livestock manure and peat into value-added fertilizers provides an environmentally sustainable approach to nutrient recycling and waste management. In this study, organic fertilizers were formulated from poultry, pig, and cattle manure mixed with peat and wood ash, with or without inoculation of the phosphate-solubilizing bacterium Priestia megaterium. Their efficiency was evaluated through plant growth and soil microbiological experiments involving conifer seedlings, herbaceous crops, and ornamental plants. Germination and growth trials with Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) revealed clear species-specific responses: spruce seedlings performed best in substrates containing poultry or cattle manure, while pine showed enhanced growth with pig manure combined with bacterial inoculant. In pansies (Viola × wittrockiana), growth responses varied by cultivar; cattle manure enriched with bacteria increased leaf projection area, whereas poultry manure markedly suppressed growth. For cucumbers, basil, barley, radish, and garden beans, yields were lower than with mineral fertilizers, yet bacterial inoculation significantly influenced soil microbial activity by modifying respiration rates and hydrolytic enzyme intensity in plant- and manure-specific ways. The results demonstrate that microbial supplementation can alter soil biological processes and nutrient turnover, though its effects on plant productivity remain inconsistent. Further research is required to assess long-term performance under field conditions, as practical application will depend on achieving stable and reproducible results.

This study examines the spatial root development patterns of bareroot, containerized, and plug plus (plug+) saplings in hemiboreal forests of Latvia, focusing on the effects of two common soil preparation methods: mounding and disc trenching. In northern Europe, forest regeneration after clearcutting often involves planting, with soil preparation aimed at enhancing sapling survival and productivity. This study included four tree species: Pinus sylvestris, Picea abies, Betula pendula, and Alnus glutinosa. The results reveal that saplings planted in mounded sites developed more radially symmetrical root systems, while roots in trenched sites predominantly grew parallel to the furrow. This spatial root distribution was consistent across all forest types and did not show significant variation between stock types (containerized, bareroot, or plug+) or treatments (control or fertilized). Additionally, the number of main roots did not differ significantly between the soil preparation methods. These findings align with previous research and raise important questions regarding the impact of early root architecture on stand resilience at a mature stage, particularly in relation to windthrow, heavy snowfall, drought, and flooding resistance. The study underscores the need to consider root system development as a key factor in forest management practices aimed at ensuring long-term forest stability.

Short-rotation forest plantations on former agricultural land capture CO₂, provide bioeconomic materials, and mitigate climate change. This study aimed to enhance our understanding of the long-term effects of wood ash and wastewater sludge fertilization on various tree species (birch, hybrid aspen, grey alder, black alder, and hybrid alder) in short-rotation forestry plantations on abandoned agricultural land where tree growth measurements were taken over an 11-year period. After 11 years, the highest aboveground biomass (AGB) was observed for hybrid aspen clone No. 4 under wastewater sludge treatment (109.0 t ha⁻¹), birch under wood ash treatment (34.3 t ha⁻¹), black alder under wastewater sludge treatment (33.6 t ha⁻¹), grey alder under wastewater sludge treatment (40.9 t ha⁻¹), hybrid alder under control conditions (36.2 t ha⁻¹), and hybrid aspen clone No. 28 under wood ash treatment (37.2 t ha⁻¹). The average survival rate was 73% in control plots, 81% under wastewater sludge treatment, and 78% under wood ash treatment. Short-term positive impacts on tree growth were observed, effects that were not consistent over the long term. The impact of these treatments on tree growth varied between species, and the effects tended to diminish over time, which must be considered before fertilization.

Forests in Latvia are crucial, covering over half of the country’s territory and expanding continuously through afforestation and natural growth

In the context of climate change, it is necessary to establish forest management by balancing more products, using less area, and minimizing environmental impacts. The use of different industrial bio-based by-products as soil conditioners in the last few decades has gain more interest, because it leads to an extended use time of these products and supports the circular economy. The aim of this study was to determine the effect of fertiliser made from cattle and pig manure biogas fermentation digestate and wood ash from two cogeneration plants, applied in different mixture ratios, to test its suitability for fertilisation of deciduous trees, using the physiological, morphological, and chemical parameters of the leaves as an indicator. We selected two poplar clones: foreign ‘OP42’ (syn. Hybrid 275) and local ‘AUCE’ annual shoot stem cuttings as planting materials. A negative control group with acidic forest mineral soil as substrate and four fertilised groups with different applied digestate and wood ash ratio mixtures to forest soil was established (ash:digestate 0:0 (Control), 1:1, 2:1, 3:1, 4:1). Mixture application improved growing conditions because all fertilised group poplars had longer growth periods and photosynthetic rates in August than the control group. Both local and foreign clones showed a good response to fertilisation in terms of leaf parameters. Poplar is a suitable culture to fertilise with bio-waste biogenic products, because of its capacity to absorb nutrients and fast response to fertilisation.

The selection of most suitable propagation material, as well as the adjustment of existing seedling management practices, are gaining increasing importance to ensure the best outcomes under the long-term setting of climate change. One of the factors to consider is a predicted increase in the frequency and duration of high-temperature periods. Since heat often coincides with drought, these factors are typically assessed together, yet heat stress on its own has received less attention. In this study, we examined the effect of supra-optimal ambient temperature on nine Salix alba clone cuttings wilting under greenhouse conditions and sufficient moisture levels. Most plants are especially vulnerable to extreme conditions in early stages of development. Response to heat varied between clones but, overall, shoots that were taller than 350 mm were more sensitive to heat stress. The pruning of excess lateral shoots did not show significant improvement in heat tolerance. In total, 96% of the wilted cuttings proceeded to produce lateral shoots after the cessation of heat stress. It should be studied further if similar patterns are evident in field conditions and if earlier outplanting has a positive effect on cutting vitality.