Research Highlights: Studies on tree canopy dwelling species often require simple proxies of tree canopy volume estimated at a stand level. These include allometrically related tree crown parameters such as crown area and basal area, and canopy cover. Background and Objectives: In monoculture Scot’s pine and mixed pine/Norway spruce forest, we aimed to test the relationships between tree diameter at breast height (DBH) and tree crown volume at a tree level and between densitometer canopy closure estimates and tree crown volume at a stand level. Materials and Methods: The study was carried out in eastern Latvia (hemiboreal zone) in monoculture pine and mixed coniferous stands. On a subset of trees in 22 forest stands (88 100 m² plots), we determined the best regression model that described the relationship between tree DBH and crown volume for spruce and pine. Tree crown volume at a stand level was determined from the individual tree volume estimates calculated from these regression models. On a stand level, we also calculated regression models for densitometer closure estimates versus total crown volume for pine and mixed stands. Results: Linear mixed effects models showed significant relationships between DBH and crown volume for pine (R² = 0.63) and spruce (R² = 0.40), indicating that basal area could be used as a predictor of crown volume at a stand level. Variance explained by a regression model of canopy closure versus tree crown volume at a stand level was R² = 0.52. Conclusions: Tree basal area and crown closure can be used as proxies of tree crown volume at a stand scale in monoculture stands. In mixed stands estimates of crown volume based on basal area need to be calculated separately for each tree species, while canopy closure will provide an estimate of total crown volume.

Tree rings are one of the most important indicators for reconstructing past history of climate variability as well as anthropogenic and ecological processes. The climatic signal for the past centuries recorded on tree rings is well known in regions of Europe for Scots pine growing in dry conditions, but little knowledge is available regarding pines growing on peatlands. Extreme changes of environmental conditions limit the radial increment of trees and influence the formation of very wide or very thin tree rings. Usually, these extreme events (pointer years) are best explained by climatic factors. The study was carried out on five bogs with variable evidence of past human disturbance. A large number of pointer years common between study sites were identified (positive 1913, 1916, 1917, 1934–1939, 1957, 1967, 1968, 1972 and negative 1865–1867, 1926, 1928–1931, 1947–1949, 1951, 1990, 2000, 2002). Correlation analysis between climatic variables (maximal, minimal, and mean air temperature and precipitation sum) and pointer years indicated that the response to precipitation sum was mainly local and low compared to the response to air temperature. The main climatic variables influencing the development of pointer years were the mean air temperature in the growing season (May–September) and minimal air temperature in February, as well as the precipitation sum in February (positive response) and in the growing season (negative response). However, pointer year development of Scots pine on bogs is mainly determined by local factors.

Global climate change impact has increased in recent decades and put urgency on implementing effective climate change mitigation (CCM) activities. Rewetting of drained peatlands is an acknowledged measure to reduce GHG emissions from organic soils in the agriculture and land use sectors. Under waterlogged conditions, decomposition of organic matter in peat decreases, and emissions of CO₂ are reduced. Thus, the soil carbon stock is saved, and wet management of the site reactivates carbon sequestration. To reach CCM targets, the first rewetting and paludiculture trials have been implemented in Latvia. In this article, we review the current status of paludiculture in Latvia and evaluate the pros and cons of their wider implementation. The majority of paludiculture projects and pilot studies in Latvia have not been published so far and are reported here for the first time. Our assessment of paludiculture shows that trails on Alnus, Phalaris, Phragmites, Sphagnum, and Typha installed by the private enterprises have promising results for upcoming large-scale implementation. There are available areas for paludiculture in Latvia, but the current legislation and national framework policies (environment, agriculture, forest, and climate) do not fully support such activities yet and must be adapted.

Tree-ring width chronologies provide a retrospective record of the past tree growth, which allows scientists to infer the past history of environmental change. These types of studies have already been conducted throughout Europe for Scots pine (Pinus sylvestris L.) growing in dry conditions, but there is little knowledge about pine growth on organic soils. Scots pines were cored on dry and wet soils near Lake Engure to obtain tree-ring widths and to determine climate–growth relationships. Scots pine growth response to precipitation differed between the wet soil and dry soil sites. On the wet soil Scots pine was more sensitive to precipitation in the previous year and in October while yearly precipitation (previous-year October to present-year September) and growing-period precipitation (April–September) positively influenced pines growing on the dry soil. Yearly temperature and dormant-period temperature (January–March) showed a positive influence on tree growth on both sites. The explained variation of tree-ring width was very low: 5.9% for the dry site and 14.8% for the wet site. Therefore, unknown other abiotic and also biotic factors (e.g. competition) may have had a strong influence on the radial growth of the trees in this study.

Fire is a common disturbance in boreal forests causing changes in biological diversity at various spatial scales. In the past 100 years, forest management has limited fire outbreaks, but in the future, the fire-affected forest area is expected to increase in many regions due to climate change. Burned forests are typically salvage-logged, but the effect of this type of management versus natural regeneration on biological diversity is not well understood, particularly the mid-term effect to tree establishment and understory vegetation composition and diversity. Various management methods were used after a large fire in 1992 in a peatland-forest complex and neighbouring managed forests, which created an experimental setup for study of the effect of management after fire in the Sliteres National park, northwestern Latvia. Understory vegetation was described in plots using a design of four forest and three management types: natural regeneration (unmanaged) and managed sites with salvage logging followed by no further human intervention and salvage logging with planting. Post-fire management had different effect in each forest type. Species richness was higher in forest types with salvage logging than in natural regenerated sites on rich wet and rich dry forest types, but not for the poor forest types. Tree regeneration was generally greater in salvage-logged stands, but differed between forest types. Species composition was related to tree regeneration and canopy openness. In contrast to other studies, salvage logging had a positive mid-term effect to ground vegetation diversity and tree establishment in the studied stands, implying potential for concomitant management and conservation of ground cover vegetation in semi-natural stands.

Blood parasites are considered to have strong negative effects on host fitness. Negative fitness consequences may be associated with proximity to areas where blood parasite vectors reproduce. This study tested for relationships between haemosporidian infection prevalence, parasitemia, and fitness parameters of breeding Pied Flycatchers (Ficedula hypoleuca) at different distances from forest water bodies. Prevalence and parasitemias (the intensity of infection) of haemosporidians and vector abundance generally decreased with increasing distance from forest lakes, streams, and bogs. Fledgling numbers were lower, and their condition was worse in the vicinity of water bodies, compared with those located one kilometer away from lakes and streams. At the beginning of the breeding season, adult body mass was not related to distance to the nearest water body, whereas at the end of the breeding season body mass was significantly lower closer to water bodies. Forest areas around water bodies may represent ecological traps for Pied Flycatchers. Installing nest boxes in the vicinity of forest water bodies creates unintended ecological traps that may have conservation implications.