Analysing detection bands of two-spectral reflection method to identify forest species composition

The optical reflection method is considered for detection of the forest areas where coniferous or broadleaved trees are dominant. Statistical modelling of correct detection and false alarm probabilities for identifying dominant (coniferous or broadleaved) tree species by the two-spectral reflection method has been conducted. It has been shown that monitoring enables us to identify dominant (coniferous or broadleaved) tree species with correct detection probability close to 1 and false alarms probability ~ second decimal places for the temperate climate zone at the wavelengths of 532 and 1540 nm or 532 and 1480 nm. As to the subtropical climate zone, due to a great variety of reflection spectra of vegetation, a selection of the spectral detection bands for reliable identification of dominant coniferous or broadleaved tree species is possible only for specific forestlands where the number of evergreen broadleaved and coniferous tree species is relatively small.

Plant and Wood Area Index of Solitary Trees for Urban Contexts in Nordic Cities

Background: We present the plant area index (PAI) measurements taken for 63 deciduous broadleaved tree species and 1 deciduous conifer tree species suitable for urban areas in Nordic cities. The aim was to evaluate PAI and wood area index (WAI) of solitary-grown broadleaved tree species and cultivars of the same age in order to present a data resource of individual tree characteristics viewed in summer (PAI) and in winter (WAI). Methods: All trees were planted as individuals in 2001 at the Hørsholm Arboretum in Denmark. The field method included a Digital Plant Canopy Imager where each scan and contrast values were set to consistent values. Results: The results illustrate that solitary trees differ widely in their WAI and PAI and reflect the integrated effects of leaf material and the woody component of tree crowns. The indications also show highly significant (P < 0.001) differences between species and genotypes. The WAI had an overall mean of 0.91 (± 0.03), ranging from Tilia platyphyllos ‘Orebro’ with a WAI of 0.32 (± 0.04) to Carpinus betulus ‘Fastigiata’ with a WAI of 1.94 (± 0.09). The lowest mean PAI in the dataset was Fraxinus angustifolia ‘Raywood’ with a PAI of 1.93 (± 0.05), whereas Acer campestre ‘Kuglennar’ represents the cultivar with the largest PAI of 8.15 (± 0.14). Conclusions: Understanding how this variation in crown architectural structure changes over the year can be applied to climate responsive design and microclimate modeling where plant and wood area index of solitary-grown trees in urban contexts are of interest.

Loss in macronutrient pools in bilberry and lingonberry in mesic Scots pine forests after Northern red oak introduction

Forest transformation from coniferous monocultures to mixed stands is being promoted worldwide, including the introduction of fast-growing broadleaved tree species within native stands. Here, we studied how enrichment of temperate European Scots pine (Pinus sylvestris) forest by North-American northern red oak Quercus rubra impacted macronutrient concentrations in two long-lived and dominant components of the forest understory: bilberry Vaccinium myrtillus and lingonberry V. vitis-idaea. Study sites were located in forest complexes (central Poland) which occupy continuously reforested lands (hereafter ancient forests) as well as post-agricultural lands (recent forests), all suitable for mesic pine forests. Samples of bilberry and lingonberry leaves, stems, and fruits were collected in pine stands and in adjacent Scots pine-red oak stands, in both ancient and recent forests. Concentrations of macronutrients (C, N, P, K, Ca, S, and Mg) in aboveground biomass components were analysed using standardized chemical procedures. The study revealed intra- and interspecific (bilberry vs. lingonberry) differences in concentrations of all nutrients in leaves, stems, and fruits, except for invariable C concentrations. Macronutrient accumulations in plants were decreased by land-use discontinuity and favoured by enrichment of tree stands by Q. rubra. The estimated macronutrient pools were much higher for V. myrtillus than V. vitis-idaea in all forest types studied. They were lower in forests enriched with Q. rubra, both ancient (up to 25.5% for bilberry and 99.9% for lingonberry) and recent (46.9% and 99.9%, respectively), as well as in recent pine forest (46.6% and 81.1%, respectively) than in ancient pine forest. Higher K and S pools (39.3% and 6.5%, respectively) noted for bilberry in an ancient forest with Q. rubra were exceptions. Despite more effective accumulations of elements at the species level, macronutrient pools of Vaccinium myrtillus and V. vitis-idaea decreased significantly in the presence of introduced Q. rubra due to negative impacts of this broadleaved tree on bilberry and lingonberry cover and biomass. Therefore, the limitation of alien Q. rubra planting in sites of mesic pine forest with the abundant occurrence of V. myrtillus and/or V. vitis-idaea is recommended. Graphic abstract

Patterns of Leaf Morphological Traits of Beech (Fagus sylvatica L.) along an Altitudinal Gradient

Broadleaved tree species in mountainous populations usually demonstrate high levels of diversity in leaf morphology among individuals, as a response to a variety of environmental conditions associated with changes in altitude. We investigated the parameters shaping leaf morphological diversity in 80 beech individuals (Fagus sylvatica L.), in light and shade leaves, growing along an elevational gradient and under different habitat types on Mt. Paggeo in northeastern Greece. A clear altitudinal pattern was observed in the morphological leaf traits expressing lamina size and shape; with increasing altitude, trees had leaves with smaller laminas, less elongated outlines, and fewer pairs of secondary veins. However, this altitudinal trend in leaf morphology was varied in different habitat types. Furthermore, the shade leaves and light leaves showed differences in their altitudinal trend. Traits expressing lamina shape in shade leaves were more related to altitude, while leaf size appeared to be more influenced by habitat type. While the altitudinal trend in leaf morphology has been well documented for numerous broadleaved tree species, in a small spatial scale, different patterns emerged across different habitat types. This morphological variability among trees growing in a mountainous population indicates a high potential for adaptation to environmental extremes.

State of in situ forest genetic resources of broadleaved tree species in the Right-Bank Forest-Steppe of Ukraine

Forest genetic resources (FGRs) are an important source of biodiversity conservation and forest restoration. Today, more than 600 genetic reserves (GRs) of more than 30 main forest tree species have been allocated in Ukraine. The main aim of the work is to reveal the features of the distribution, environmental condition and the trends of state of in situ gene sources of broadleaved tree species in the Right-Bank Forest-Steppe of Ukraine. Based on the research results, it has been established that the share of FGR in situ is only 0.3–0.5% of the total forest area of the region. The predominant species of forest stands of the region are English oak (Quercus robur L.) – 37.7%, European beach (Fagus sylvatica L.) – 26.8% and Common ash (Fraxinus excelsior L.) – 7.6%. The in situ locations of Black alder (Alnus incana L.), Sessile oak (Quercus petraea (Matt.) Liebl.), English oak and Common ash are characterized by the highest average annual temperature (8.1–8.2°С), the accumulated temperatures for the growing season (3111.9–3237.1°С). Stands with the European beech predominance are allocated in better moisture conditions by the precipitation-temperatures ratio (Selianinov Hydrothermal Index (HTI) – 1.769–1.802; climatic index by Vorobyov – 2.707–2.951). The in situ gene pool conservation units are defined by 12 soil types that are included in the 7 main groups according to the FAO international classification. The largest number of sites, 67 (56.8%), is concentrated on grey and dark-grey forest soils (Haplic Greyzems) (47%). According to the research results, GRs are not evenly distributed, they do not fully reflect the environmental diversity, and their area is negligible. We indicated the unsatisfactory condition of most genetic reserves. It was caused by reducing the share of main tree species, decrease in relative stocking density of stands and tree-breeding structure and deterioration of tree stands condition. This requires the development and implementation of an integration strategy based on the established concept of developing a national ecological network on both national and pan-European levels.

A comparison of ground-based count methods for quantifying seed production in temperate broadleaved tree species

• Key message Litter trap is considered the most effective method to quantify seed production, but it is expensive and time-consuming. Counting fallen seeds using a quadrat placed on the ground yields comparable estimates to the litter traps. Ground quadrat estimates derived from either visual counting in the field or image counting from quadrat photographs are comparable, with the latter being also robust in terms of user sensitivity. • Context Accurate estimates of forest seed production are central for a wide range of ecological studies. As reference methods such as litter traps (LT) are cost- and time-consuming, there is a need of fast, reliable, and low-cost tools to quantify this variable in the field. • Aims To test two indirect methods, which consist of counting the seeds fallen in quadrats. • Methods The trial was performed in three broadleaved (beech, chestnut, and Turkey oak) tree species. Seeds are either manually counted in quadrats placed at the ground (GQ) or from images acquired in the same quadrats (IQ) and then compared against LT measurements. • Results GQ and IQ provide fast and reliable estimates of seeds in both oak and chestnut. In particular, IQ is robust in terms of user sensitivity and potentially enables automation in the process of seed monitoring. A null-mast year in beech hindered validation of quadrats in beech. • Conclusion Quadrat counting is a powerful tool to estimate forest seed production. We recommend using quadrats and LT to cross-calibrate the two methods in case of estimating seed biomass. Quadrats could then be used more routinely on account of their faster and simpler procedure to obtain measurements at more spatially extensive scales.

BROADLEAVED TREE TRUNKS CHARRING DURING FOREST FIRES WITHIN THE UKRAINIAN ROZTOCHYA

Introduction. On the territory of Ukrainian Roztochya and Male Polissya (Zhovkva part of Roztochya included) fires often occur in natural ecosystems – forest fires, meadow vegetation burning, stubble, landfills, and peatlands. Such fires, in addition to the destruction of property, cause significant emissions of incomplete combustion products and smoke into the air. Charring of broadleaved species, along with conifers, needs more detailed research, as the territory of the Ukrainian Roztochya is dominated by hornbeam-oak-pine, mixed oak, and beech forests.Aim. The object of the paper is to investigate the degree of tree trunks charring of the main forest-forming species in the Ukrainian Roztochya during forest fires based on experimental data.Research methods. Freshly cut trees were exposed to heating for 10 minutes, at periods of 1 minute, 3, and 5 minutes, checking the degree of damage to the trunk (charring, mm). Repeatability of the experiment – three times. Basing on received data the charring of broadleaved tree trunks in the Ukrainian Roztocze was determined. The flame temperature was measured by a GM1150A non-contact pyrometer. The level of burnout was measured by a ruler made following GOST 17435-72. A stopwatch was used to record the time of burning. Results and discussion. The experiments were performed in the fresh air under close-to-natural conditions. The fire source was an artificial open flame. Freshly cut tree trunks were installed vertically, right in the burning zone. Cutting residues, fallen dry leaves, straw, dry grass was used as flammable material. It was found that the lowest degree of charring is inherent to oak, which has burned by 38 mm during 10 minutes (with log thickness of 124 mm). Species such as hornbeam and maple completely burned out in 10 minutes (in diameters of 129 mm and 140 mm).Conclusions. Investigations of temperature effects on the main forest-forming species of the region have shown that they all differ in charring during forest fires. Three species grown in Ukrainian Roztochya were selected – hornbeam (Carpinus betulus), oak (Quercus robur), and maple (Acer platanoides). To prevent fires in forests, fire lanes should be planned with oak plantations on the edge of the forest.

Accuracy of Photo-Optical Measurement of Wood Piles

The accurate estimation of timber volume is of the utmost importance. For industrial timber, the volume is often estimated as stacked cubic meters. In addition to manual measurements, volume estimation is possible with photo-optical systems. Over 100 piles of industrial timber of broadleaved tree species were analyzed. In the study, a standard manual measurement method for the estimation of wood pile volumes was compared with a smartphone based photo-optical application for the determination of woodpile volume. Mean gross volume of the piles was approximately 56 m3 and mean width of piles was 9.43 m. A strong correlation was found between the manual measurements and the photo-optical measurement. However, volume estimation of large volume piles seems to perform better in comparison to piles with small volumes. Further research is needed to determine the effects of variables such as log quality or quality of pile on volume estimation accuracy.

Harvester Productivity in Inclined Terrain with Extended Machine Operating Trail Intervals: A German Case Study Comparison of Standing and Bunched Trees

The complexity of highly structured forests with multiple tree species, especially when coniferous and broadleaved tree species are mixed, as well as stands with extended machine operating trail spacing and inclined terrain, create challenging operational conditions for mechanized timber harvesting and extraction. Motor-manually felling trees within the midfield and bunching them at the machine operating trails, prior to the arrival of a harvester-forwarder system, is a complex operation. The aim of this study was to assess and compare tethered harvester productivities of a thinning operation, for felling and processing standing trees and for processing bunched trees, through a time study in forest stands with 40-m distances between machine operating trails. Total operational costs of the analyzed thinning operation were 69 €/m3o.b., including extraction using a multiple forwarder approach. Tree species, merchantable timber volume, and whether the trees were standing or presented as bunched logs all had a significant effect on the harvester time consumption. Moreover, harvester positioning time was significantly shorter when trees were already bunched at the machine operating trail. While the productivity of standing or bunched spruce trees did not differ significantly between the cases (approximately 18 m3o.b./productive machine hours excluding all delays (PMH0)), the productivity of standing broadleaved tree species (8.3 m3o.b./PMH0) was much lower than that of bunched trees (15.5 m3o.b./PMH0). Thus, the described timber harvesting and extraction system may be a valuable option for forest stands with high proportion of broadleaved trees.

Mixed Broadleaved Tree Species Increases Soil Phosphorus Availability but Decreases the Coniferous Tree Nutrient Concentration in Subtropical China

Phosphorus (P) is a key limiting nutrient in subtropical forests and mixed forests with broadleaved species have been expected to stimulate P cycling, compared to pure conifer plantations. However, the mixture effect of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and broadleaved species on rhizosphere soil and coniferous tree P dynamics is unclear. In our study, eight plots of a single species of a Chinese fir plantation (pure plantation, PP) and eight mixed plantations (mixed plantation, MP) with broadleaved tree species (Michelia macclurei Dandy in Hunan Province or Schima superba Gardn. et Champ. in Fujian Province) were selected in subtropical China. Six P fractions in the rhizosphere and bulk soils were analyzed by a modified Hedley P fractionation method. Phosphorus fractions and nitrogen (N) concentrations in different root orders, different age fresh needles and twigs, and needle and twig litter of Chinese fir were measured. Our results showed that available P, slowly released P, occluded P, and the total extractable P in rhizosphere soil were significantly higher in MP than PP (p < 0.05). In contrast, P and N concentrations in the transportive roots and two-year old needles were generally higher in PP than MP. Meanwhile, the slowly released P, occluded P, total extractable P, and residual P in rhizosphere soil were negatively correlated with P concentrations in young (absorptive and transportive roots, one- and two-year old needles) but not old tissues (storative roots, three-year old needles and litters). In conclusion, mixture may increase soil P availability through the rhizosphere effect, but can decrease P and N concentration of Chinese fir tissues by competition between Chinese fir and broadleaved species. Clearly, the mixture effect may differ in soil and plant nutrients, and this issue needs be taken into consideration when converting a pure conifer plantation into a mixed-species forest.