Spruce Forest Research Articles

Seasonal dynamics of canopy interception loss within a deciduous and a coniferous forest

AbstractCanopy interception loss is a key process in forest hydrology and the role of interception loss in relation to the forest water budgets and future impact of afforestation on water resources is important to quantify. Based on high frequency in situ monitoring, the effect of species‐ and leaf‐cover‐specific canopy structure metrics for interception loss estimation is examined at the two most typical forest types in Denmark. First, interception loss is estimated from precipitation and throughfall data collected in two even‐aged (40–60 years) temperate oak (deciduous) and Norway spruce (coniferous) forests over 13 and 11 months, respectively. Second, based on these observations we estimated canopy structure parameters relevant for interception loss; direct throughfall (ρ), the precipitation necessary to saturate the canopy (P'), the canopy evaporation as a fraction of precipitation (EC/P) and canopy storage capacity (S). Third, we compare observation‐based interception loss with predictions obtained by the analytical Gash interception model using the derived canopy structure parameters. Lastly, the effect of species‐ and leaf‐cover on the interception loss is quantified by applying the canopy structure parameters of the deciduous and coniferous forest on the same daily precipitation data set of approximately 1 year in the Gash model. We found that the derived canopy structure parameters reflect the seasonal change in the leaf cover of the deciduous forest and different parameters are identified for the two forest types. In the deciduous forest, improved agreement between observation‐based and predicted interception loss is obtained using canopy structure parameters for the leafless and full‐foliage periods instead of annual average values. The share of throughfall and interception loss to precipitation (total sum of precipitation = 526 mm) is 65% (340 mm) and 35% (186 mm) for the deciduous forest, respectively, and 49% (260 mm) and 51% (266 mm) for the coniferous forest, respectively. A seasonal variation of interception loss is observed in the deciduous forest where the share of interception loss to precipitation is 40% during the period with leaves on the trees (June to November) and 22% for the leafless periods (December to May). Thus, species‐ and leaf‐cover‐specific canopy structure metrics enhance model performance of throughfall and interception loss dynamics in forests.

Restoration of Vegetation Greenness and Possible Changes in Mature Forest Communities in Two Forests Damaged by the Vaia Storm in Northern Italy.

Windstorms are rare in the Southern Alps, but their frequency is increasing due to climate change. This research analyzed the vegetation of two spruce forests in Camonica Valley (Northern Italy) destroyed by the Vaia storm to evaluate the vegetation responses to blowdown damage. In each study area, the normalized difference vegetation index (NDVI) was used to evaluate the change in plant cover and greenness from 2018 (before the Vaia storm) to 2021. Furthermore, floristic-vegetation data were analyzed to identify current plant communities and develop models of plant succession. The results showed that the two areas, although located in different altitudinal vegetation belts, are undergoing the same ecological processes. NDVI is increasing in both areas, and pre-disturbance values (~0.8) should be reached in less than ten years. Nevertheless, the spontaneous restoration of pre-disturbance forest communities (Calamagrostio arundinaceae-Piceetum) should not occur in both study areas. In fact, the two plant succession trends are characterized by pioneer and intermediate stages with young trees of Quercus petraea and Abies alba, typical of more thermophilic mature forest communities compared to pre-disturbance ones. These results could reinforce the trend of the upward shift in forest plant species and plant communities in response to environmental changes in mountain areas.

Subarctic Vegetation under the Mixed Warming and Air Pollution Influence

In the Siberian Arctic, worldwide largest forest mortality was caused by chronical (since the 1940s) influence of SO2 emissions on the larch-dominant communities. We hypothesized that warming might mitigate SO2 influence by increasing trees’ vigor and growth. We studied trees (larch, Larix sibirica; spruce, Picea obovate; birch, Betula pendula) and bushes (willow, Salix sp., alder, Duschekia fruticosa) growth dependence on SO2, air temperature, soil temperature and moisture, and precipitation. We sampled woods in severely damaged larch and moderately damaged mixed larch, spruce and birch forests. We generated tree ring chronologies and growth indices (GI). We used Terra/MODIS satellite data for mapping trends of vegetation (NDVI) and productivity (GPP, NPP) indexes. In the larch forest, we found a strong decrease in GI and tree mortality, which lasted until the end of 1990s. In the mixed forest, larch and birch were more resistant to SO2 influence compared to spruce. SO2, air and soil temperatures were mediators of all woody species growth. Winter precipitation stimulated trees growth by mitigating spring water stress. Warming onset in the 2000s led to a pronounced increase of all woody species growth. June–July air and soil temperatures, together with a moderate decrease in SO2 emissions, were the primary drivers of that phenomenon. Increasing trends of GPP, NPP, and NDVI were observed within the large part of earlier damaged forests, which was attributed to trees GI increase together with the expansion of SO2-resistant grasses and bushes.

Multi-Proxy Paleoecological Reconstruction of Peatland Initiation, Development and Restoration in an Urban Area (Moscow, Russia)

Peatlands play an important role in the global carbon cycle but have been exploited over many centuries, which reduces their carbon storage capacity. To investigate peatland development during the late Holocene and their restoration after peat extraction, we applied a multi-proxy paleoecological (pollen, plant macrofossils, testate amoebae, loss on ignition, peat humification, etc.) approach to undisturbed and floating vegetation mat deposits of the Gorenki peatland (Meshchera Lowlands, East European Plain). Peatland development started around 2550 before the common era (BCE) as a waterlogged eutrophic birch forest (terrestrial paludification) surrounded by a broadleaf forest. Around 2400 BCE, the peatland turned into an open mire with Sphagnum mosses, sedges, and willows. During 900–800 BCE, the mire transformed into a wet mesotrophic peatland surrounded by a spruce forest. The first human settlements and deforestation around 300–400 CE coincided with oligotrophization of the mire. The growth of the Slavic population in the region in 14th century CE caused transformation of indigenous spruce–broadleaf forests into croplands, and the mire became drier and forested. Since peat extraction was abandoned in the beginning of 20th century CE, the mire has undergone self-restoration starting with the formation of a Sphagnum cuspidatum/obtusum quagmire on the floating peat remains. The Sphagnum mat stabilized during 1960–2000 CE. During the last twenty years, agricultural activity decreased and pine forests were restored in the adjacent area; the floating mat became drier and more oligotrophic, which can lead to the formation of a bog in the absence of considerable anthropogenic impact.

Ongoing climatic change increases the risk of wildfires. Case study: Carpathian spruce forests

The challenge to the sustainable development of forestry in the Eurasian temperate - boreal zone is the increase in the frequency and severity of natural disturbances due to global climate change. In this study, a mathematical model for predicting the risk of wildfires in spruce stands growing in the territory of Slovak Paradise National Park under climate change has been proposed and tested. Wildfire risk is described in terms of the observed probabilities of the destruction of spruce stands in relation to their age for a period of 10 years. As the indicators of assumed climate change, the time series of daily values of four fire weather indices (Angstrőm, Nesterov, Baumgartner, and the Meteorological Forest Fire Risk Index) for the period 1951–2019 have been analysed. The results obtained indicated the significant dependence of the observed increasing annual population proportions of burnt areas on the gradually increasing annual population proportions of risky days recorded and evaluated by using the common scales of risk classification. We found that ongoing climate change has a significant impact on increasing the risk of fires. The Meteorological Forest Fire Risk Index has proven to be the most suitable measure for predicting the probability of fire occurrence under the climate conditions in the experimental territory. The indicated risk of fire occurrence in spruce stands under the assumption of a climatic change is substantially higher than in the case when this assumption is neglected. This information can also serve as a basis for the formulation of efficient landscape fire protection measures focused on building the infrastructure to support the efficient retardation of propagation, including the quick suppression of this detrimental natural hazard.

Age matters: Life-stage, tissue, and sex-specific gene expression dynamics in Ips typographus (Coleoptera: Curculionidae: Scolytinae)

The Eurasian spruce bark beetle (ESBB), Ips typographus, has recently caused catastrophic damage to Norway spruce (Picea abies) forests in Europe, resulting in the loss of more than 100 million cubic meters of wood. Traditional forest management strategies have failed to constrain the growing infestation rate; hence, novel measures must be deployed. A better understanding of ESBB physiology and adaptation to host allelochemicals may provide a platform for future management strategies using molecular tools such as RNA interference. To understand ESBB physiology and adaptation, the current study unraveled the gene expression dynamics of ESBB in different life stages and tissues. We obtained ESBB transcriptomes for different life stages [larvae (L1, L2, and L3), pupa, callow, and sclerotized adult] and male/female tissues (gut, fat body, and head) from callow and sclerotized adult beetles. Differential gene expression analysis (DGE) identified multiple gene families related to detoxification, digestion, resistance, and transport in different life stages and tissues of the beetle. Gene Ontology (GO) enrichment revealed 61 critical metabolic pathways enriched across all DGE comparisons. DGE analysis further pinpointed the differential expression of essential genes involved in detoxification, digestion, transport, and defense in various tissues and life stages. RT-qPCR experiments and enzymatic assays corroborated the findings further. The catalogue of differentially expressed genes identified in ESBB could aid better understanding of ESBB physiology and adaptation to hosts and serve as targets for future RNAi-based ESBB management.

Elucidating the composition of organic matter in water-repellent forest soils using analytical pyrolysis combined with gas chromatography–mass spectrometry (Py-GC–MS)

Soil water repellency (SWR) is an inability of soil to spontaneously absorb water. It affects the spatial distribution of soil moisture, may cause formation of preferential flow, increase surface runoff and the risk of water erosion, or affect nutrient availability for crops. Although there is a general agreement among published data that SWR is caused by hydrophobic components of soil organic matter (SOM), more comprehensive information is needed. Additionally, the link between SWR occurrence and SOM genesis has not been studied sufficiently. In this work, we analyzed SOM in water-repellent soils by pyrolysis combined with gas chromatography and mass spectrometry (Py-GC–MS). The samples were taken from two forest ecosystems in Slovakia: relatively dry pine–oak forest, located in the Záhorská nížina lowland (Záhorie), and spruce forest in the High Tatras with a colder and more humid climate. The results showed that the composition of SOM at both sites is dominated by partially decomposed residues of plant biomass. Whereas most compounds detected in the Záhorie samples were identified as pyrolysis products of lignin, the pyrolysates of the High Tatras soils originated mainly from polysaccharide-like substances. Although lauric (12:0), myristic (14:0) and palmitic (16:0) fatty acids were detected in pyrograms of water-repellent samples, the results suggest that the residues of lignin decomposition may contribute to SWR as well. Pyrolysates such as methylguaiacol, vinylguaiacol, dimethylphenol, or the methyl ester of vanillic acid are examples of less polar lignin-like moieties. Py-GC–MS data, as well as other soil properties, suggest that SWR at both sites is associated with the accumulation of certain SOM components in the topsoil. Acidic pH, higher C/N ratio and coarse soil texture prevent organic carbon stabilization in the studied soils. As a result, SOM is in great part composed of accumulated particulate residues with lignin-like origin and lipidic coatings, which contribute to SWR development during drier conditions.

Forests Attenuate Temperature and Air Pollution Discomfort in Montane Tourist Areas

Forests deliver many ecosystem services, from provisioning to regulating and cultural services. We aimed at demonstrating microclimatic regulation and pollutant removal as especially relevant ecosystem services when considering the tourism vocation of the Alpine regions. A study was realized along an altitudinal gradient (900–1600 m a.s.l.) in Trentino, northern Italy, an area with high touristic presence (ca. 9.3 million overnight stays in summer 2021). Nitrogen dioxide (NO2, µg m−3), ozone (O3, µg m−3) concentrations, air temperature (T, °C), and relative humidity (RH, %) were simultaneously measured in three open-field sites (OF) and below-canopy Norway spruce forest stands (FO) during the period 23 May–7 August 2013. The temperature–humidity index (THI) was calculated. We found a distinct mitigating effect of forest on T, with lower maximum (−30.6%) and higher minimum values (+6.3%) in FO than in OF. THI supported a higher comfort sensation in FO than in OF, especially in the central part of the day. NO2 concentrations did not differ between OF and FO; ozone concentrations were lower in FO than OF. This study confirms the role of forests in providing several ecosystem services beneficial for forest users, especially relevant for promoting nature-based tourism in the Alpine region.

Local variability of a taiga snow cover due to vegetation and microtopography

ABSTRACT The taiga snow cover accumulates in relatively stable and windless weather. This should produce a uniform snow cover with continuous, laterally homogeneous stratigraphy and snow properties when the snow is deposited on a level, smooth substrate. However, such substrates are rare, and local variations in vegetation and ground surface topography alter the structure of the snow cover and produce irregular snow layers. In this study, we investigated the effects of vegetation, microtopography, and microclimatic variability on the taiga snow near Fairbanks, Alaska. Through the winter of 2019–2020, in situ measurements were made at three locations with distinctly different local microtopographic features and radically different (but typical) vegetation. One site was an open grassy field, the second a mature spruce forest, and the third a birch forest located on thermokarst terrain with steep microrelief where ice wedges had degraded. Widely different canopy interception processes proved to have the strongest impact on the resulting snow cover heterogeneity by altering the initial deposition, with surface microtopography having the second strongest influence through postdepositional processes. In this article, we suggest a conceptual framework for understanding and modeling taiga snow variability in terms of the vegetation and microtopography that created it.

Norway spruce sapling plasticity in their responses of architecture and growth to light gradient decreases with altitude in subalpine stands

In their natural environments, trees are able to act adaptively by changing their morphology, functional traits and growth while facing different factors and stimuli. Yet, there is insufficient information on how intraspecific growth and architectural properties vary along elevation gradients, especially for young saplings of tree species regarded as highly important in forestry. We measured the height, diameter, crown growth and several architectural properties of Norway spruce (Picea abies (L.) H. Karst.) saplings along the light gradient in three elevational transects encompassing natural distributions of subalpine spruce forest in two different locations over a 3-year span. We employed generalized linear and mixed models to determine intraspecific differences in spruce architecture and growth responses to light at different elevations. Light was a better predictor of sapling growth compared to architecture properties. At higher altitudes, we observed limited abilities in the spruce saplings to change their crown architecture and enhance their height, crown length and crown width growth with the improvement in light conditions. However, the response of diameter growth to light was well pronounced in all elevational transects. Our results suggested that spruce sapling plasticity in shaping their crown morphology and growth decreased with altitude. Yet, we reported a similar improvement in diameter growth with an improvement in light conditions regardless of altitude. These results raised the question, to what extent do current climatic conditions at upper elevations inhibit Norway spruce diameter growth. We recommend that forest managers increase their efforts to obtain a desirable stem quality and crown shape by regulating light conditions mainly in the middle and lower parts of subalpine forests rather than at the elevational limit of this species.

The effects of mixed-species root zones on the resistance of soil bacteria and fungi to long-term experimental and natural reductions in soil moisture

Mixed forest stands tend to be more resistant to drought than species-specific stands partially due to complementarity in root ecology and physiology. We asked whether complementary differences in the drought resistance of soil microbiomes might contribute to this phenomenon. We experimented on the effects of reduced soil moisture on bacterial and fungal community composition in species-specific (single species) and mixed-species root zones of Norway spruce and European beech forests in a 5-year-old throughfall-exclusion experiment and across seasonal (spring-summer-fall) and latitudinal moisture gradients. Bacteria were most responsive to changes in soil moisture, especially members of Rhizobiales, while fungi were largely unaffected, including ectomycorrhizal fungi (EMF). Community resistance was higher in spruce relative to beech root zones, corresponding with the proportions of drought-favored (more in spruce) and drought-sensitive bacterial taxa (more in beech). The spruce soil microbiome also exhibited greater resistance to seasonal changes between spring (wettest) and fall (driest). Mixed-species root zones contained a hybrid of beech- and spruce-associated microbiomes. Several bacterial populations exhibited either enhanced resistance or greater susceptibility to drought in mixed root zones. Overall, patterns in the relative abundances of soil bacteria closely tracked moisture in seasonal and latitudinal precipitation gradients and were more predictive of soil water content than other environmental variables. We conclude that complementary differences in the drought resistance of soil microbiomes can occur and the likeliest form of complementarity in mixed-root zones coincides with the enrichment of drought-tolerant bacteria associated with spruce and the sustenance of EMF by beech.

Interannual variability in the ecosystem CO2fluxes at a paludified spruce forest and ombrotrophic bog in the southern taiga

Abstract. Climate warming in high latitudes impacts CO2 sequestration of the northern peatlands through the changes in production and decomposition processes. The response of the net CO2 fluxes between ecosystems and the atmosphere to climate change and weather anomalies can vary across forest and non-forest peatlands. To better understand the differences in CO2 dynamics at forest and non-forest boreal peatlands induced by changes in environmental conditions, the estimates of interannual variability in the net ecosystem exchange (NEE), total ecosystem respiration (TER), and gross primary production (GPP) was obtained at two widespread peatland ecosystems – paludified spruce forest and the adjacent ombrotrophic bog in the southern taiga of west Russia using 6 years of paired eddy covariance flux measurements. Both positive and negative annual and growing season air temperature and precipitation anomalies were observed in the period of measurement (2015–2020). Flux measurements showed that, in spite of the lower growing season TER (332±17 … 339±15 gC m−2) and GPP (442±13 … 464± 11 gC m−2) rates, the bog had a higher CO2 uptake rates (NEE was -132±11 … -108±6) than the forest, except for the warmest and the wettest year of the period (2020), and was an atmospheric CO2 sink in the selected years, while the forest was a CO2 sink or source, depending on the environmental conditions. Growing season NEE at the forest site was between -142±48 and 28±40 gC m−2, TER between 1135±64 and 1366±58 gC m−2, and GPP between 1207±66 and 1462±107 gC m−2. Annual NEE at the forest was between -62±49 and 145±41 gC m−2, TER between 1429±87 and 1652±44 C m−2, and GPP between 1345±89 and 1566±41 gC m−2, respectively. Under the anomalously warm winter conditions with sparse and thin snow cover (2019/2020), the increased daily GPP, TER, and net CO2 uptake at the forest was observed, while at the bog, the changes in CO2 fluxes between the warm and cold winters were not significant. This study suggests that the warming in winter can increase the CO2 uptake of the paludified spruce forests of the southern taiga in non-growing seasons.

Importance of conserving large and old trees to continuity of tree-related microhabitats.

Protecting structural features, such as tree-related microhabitats (TreMs), is a cost-effective tool crucial for biodiversity conservation applicable to large forested landscapes. Although the development of TreMs is influenced by tree diameter, species, and vitality, the relationships between tree age and TreM profile remain poorly understood. Using a tree-ring-based approach and a large data set of 8038 trees, we modeled the effects of tree age, diameter, and site characteristics on TreM richness and occurrence across some of the most intact primary temperate forests in Europe, including mixed beech and spruce forests. We observed an overall increase in TreM richness on old and large trees in both forest types. The occurrence of specific TreM groups was variably related to tree age and diameter, but some TreM groups (e.g., epiphytes) had a stronger positive relationship with tree species and elevation. Although many TreM groups were positively associated with tree age and diameter, only two TreM groups in spruce stands reacted exclusively to tree age (insect galleries and exposed sapwood) without responding to diameter. Thus, the retention of trees for conservation purposes based on tree diameter appears to be a generally feasible approach with a rather low risk of underrepresentation of TreMs. Because greater tree age and diameter positively affected TreM development, placing a greater emphasis on conserving large trees and allowing them to reach older ages, for example, through the establishment of conservation reserves, would better maintain the continuity of TreM resource and associated biodiversity. However, this approach may be difficult due to the widespread intensification of forest management and global climate change.

Mountain recreation impact on changes in soil penetration resistance of spruce forests

The uniqueness of the Carpathian Mountain Forest ecosystems, a large part of which belongs to nature conservation areas, attracts a significant number of visitors annually. Intensive tourist flow on popular hiking trails leads to recreational digression, topsoil compaction, development of erosion processes and deterioration of forests. The research aims to determine the impact of recreation as an external mechanical impact on soil compaction by determining the soil penetration resistance under the canopy of predominant spruce stands. For this purpose, soil penetration resistance was measured with a penetrometer along two hiking trails within the root layer of the soil at four measuring sites at different distances from the hiking trail. In general, under the canopy of a forest stand, the soil cover is not homogeneous and the obtained penetration resistance values are characterised by considerable variability. It was revealed that for the “Zelene village – Uhorski skeli rocks” hiking trail in the areas close to the path (up to 20 m) there is a significant increase in soil penetration resistance compared to remote areas: at a depth of 10 cm it doubles, at a depth of 20 cm – by 20-40%, but with further deepening, the penetration resistance level off. At the same time, for the more popular “To Mount Pip Ivan Chornohirskyi” hiking trail, in the area adjacent to the trailbed, the penetration resistance reaches 19.6 kg·cm-2 in the upper 10 cm layer, and at a depth of 30 cm, it peaks at 37.8 kg·cm-2 (over 3 MPa), which affects the root spatial distribution of spruce forests. Intensive erosion processes due to soil compaction with an increase in soil penetration resistance above 60 kg·cm-2 (~6 MPa) are observed on the trailbed. The practical significance of the results obtained, and the established patterns is to complement existing methods for assessing the degree of recreational digression in mountainous conditions and can be the basis for designing measures to regulate tourist flows and restore affected areas

Site properties, species identity, and species mixture affect fine root production, mortality, and turnover rate in pure and mixed forests of European Beech, Norway spruce, and Douglas-fir

It is already well known that the effects of tree diversity on aboveground wood productivity depend on tree species identity and site conditions and thus can vary among different tree mixtures and forest sites. The effects of species diversity, specifically on belowground productivity and dynamics, have rarely been studied, so potential interactions with species identity and/or site conditions are largely unknown.Sequential soil coring was applied in mature pure and mixed stands of European beech, Norway spruce, and Douglas-fir in two regions of northern Germany to investigate the potential site, species, and mixing effects on fine root productivity, mortality, and turnover rates. In these ecologically and economically important species mixtures, a strong effect of site conditions on all fine root variables was found. In particular, more fine root growth was observed at the less favorable site conditions than at the more favorable ones. Species identity and interaction between site conditions and species identity were additional explanatory factors, whereat beech showed the strongest effect by site conditions. No overyielding was observed when fine root productivity was plotted against area potentially available (APA), nor were mortality or turnover. However, at specific soil depths, a mixing effect, caused mainly by beech, was observed for all variables and for both species mixtures.This study suggests that site conditions and species identity rather than species mixture are essential in explaining fine root dynamics and that increasing tree species diversity may not guarantee higher belowground productivity. However, in the face of climate change and the demand for wood as a natural and renewable resource, an admixture of Douglas-fir to pure European beech stands seems to be a reasonable alternative to an admixture of spruce, a species that is already seriously suffering by drought and bark beetle attacks.

Response of moth communities (Lepidoptera) to forest management strategies after disturbance

Spruce forests face many threats such as climate change and bark beetle outbreaks. Yet, bark beetle dynamics have a long co-evolutionary history strongly linked to spruce forest structural dynamics. Disturbed spruce forest sites resulting from bark beetle outbreaks therefore should not be regarded as degraded land, but as early successional stages following natural forest dynamics. Three post-bark-beetle disturbance sites and one closed-canopy site in the Bavarian Forest and Ĺ umava National Parks were investigated with the focus on moth communities. The three disturbed sites had undergone different post-disturbance management regimes, with one being treated by salvage logging, while at the other two forest sites deadwood was kept in the forest. To avoid the spread of bark beetles, however, the bark of dead trees was either gouged or removed. The aim was to determine how many moths can be found at the undisturbed and disturbed forest sites and if differences in community composition can be explained by different management regimes. The results highlight that natural forest disturbance can increase moth diversity, especially by favouring species that are associated with open and shrub habitats. Many rare and endangered species benefit from bark beetle outbreaks, indicating that accepting natural forest dynamics is an important part of conservation management. Post-bark beetle management seems to have a minor effect on moth communities.

Assessing the detectability of European spruce bark beetle green attack in multispectral drone images with high spatial- and temporal resolutions

Detecting disease- or insect-infested forests as early as possible is a classic application of remote sensing. Under conditions of climate change and global warming, outbreaks of the European spruce bark beetle (Ips typographus, L.) are threatening spruce forests and the related timber industry across Europe, and early detection of infestations is important for damage control. Infested trees without visible discoloration (green attack) have been identified using multispectral images, but how early green attacks can be detected is still unknown. This study aimed to determine when infested trees start to show an abnormal spectral response compared with healthy trees, and to quantify the detectability of infested trees during the infestation process. Pheromone bags were used to attract bark beetles in a controlled experiment, and subsequent infestations were assessed in the field on a weekly basis. In total, 977 trees were monitored, including 208 attacked trees. Multispectral drone images were obtained before and during the insect attacks, representing different periods of infestation. Individual tree crowns (ITC) were delineated by marker-controlled watershed segmentation, and the average reflectance of ITCs was analyzed based on the duration of infestation. The detectability of green attacks and driving factors were examined. We propose new Multiple Ratio Disease–Water Stress Indices (MR-DSWIs) as vegetation indices (VI) for detecting infestations. We defined a VI range of 5–95% as a healthy tree, and a VI value outside that range as an infested tree. Detection rates using multispectral images were always higher than discoloration rates observed in the field, and the newly proposed MR-DSWIs detected more infested trees than the established VIs. Infestations were detectable at 5 and 10 weeks after an attack at a rate of 15% and 90%, respectively, from the multispectral drone images. Weeks 5–10 of infestation therefore represent a suitable period for using the proposed methodology to map infestation at an early stage.

Санитарное состояние коренных ельников тайги Европейской России

The materials of studies carried out in the primary uneven-aged spruce forests of the taiga within European Russia are presented, in the northern taiga spruce forests are studied in the territories of the Arkhangelsk region and the Paanajarvi National Park in the Karelia Republic; in the middle taiga spruce forests are studied in the reserve «Vepssky forest» in the Leningrad region and Andomsky forestry of the Vologda region; in the southern taiga spruce forests of the Central Forest State Biosphere Reserve in the Tver Region are studied. The age and volume of trees growing on permanent test plots were determined, age series of forest stands were modelled, dynamic characteristics were established, estimates of the sanitary condition of trees and stands were made, the infestation of the biotrophic complex with wood-destroying fungi and calculations of the tree waste volume by stages of decomposition were made. A close relationship between the increase in tree damage values and the increase in the age of generations in the age series was revealed, which is interpreted as a pattern: r = 0,98 with mr = 0,05 and t = 140. The dynamics of the formation of age generations in spruce forest stands proceeds much more slowly from 4 to 6 times than the dynamics of wood debris decomposition. The characteristics of the sanitary state of native spruce stands are in the range between weakened and severely weakened communities, with high rates of rotten faults of trees in age generations and stands and significant amounts of tree waste. High rates of rot damage to trees ensure the balance of reproducible and degradable biomass in the dynamics of spruce forests. This balance is formed by differences in the time periods of biomass accumulation and the rate of decomposition of wood waste.

Environmental Drivers of Gross Primary Productivity and Light Use Efficiency of a Temperate Spruce Forest

AbstractVarious environmental variables drive gross primary productivity (GPP) and light use efficiency (LUE) of forest ecosystems. However, due to their intertwined nature and the complexity of measuring absorbed photosynthetically active radiation (APAR) of forest canopies, the assessment of LUE and the importance of its environmental drivers are difficult. Here, we present a unique combination of measurements during the 2021 growing season including eddy covariance derived GPP, sap flow, Sentinel‐2 derived canopy chlorophyll content and in situ measured APAR. The importance of environmental variables for GPP models is quantified with state‐of‐the‐art machine learning techniques. A special focus is put on photosynthesis‐limiting conditions, which are identified by a comparison of GPP and sap flow hysteretic responses to Vapor pressure deficit (VPD) and APAR. Results demonstrate that (a) LUE of the canopy's green part was on average 4.0% ± 2.3%, (b) canopy chlorophyll content as a seasonal variable for photosynthetic capacity was important for GPP predictions, and (c) on days with high VPD, tree‐scale sap flow and ecosystem‐scale GPP both shift to a clockwise hysteretic response to APAR. We demonstrate that the onset of such a clockwise hysteretic pattern of sap flow to APAR is a good indicator of stomatal closure related to water‐limiting conditions at the ecosystem‐scale.

Variation of soil-plant-atmosphere continuum stable isotope and water source in Qinghai spruce forest of the eastern Qilian Mountains

Variation of soil-plant-atmosphere continuum stable isotope and water source in Qinghai spruce forest of the eastern Qilian Mountains