Mixed Oak Forest Research Articles

Response of parasitoid communities to insecticide application during a Lymantria dispar outbreak in mixed oak forests

Abstract In the temperate mixed oak forests of Central Europe, outbreaks of insects such as the spongy moth, Lymantria dispar, can cause severe defoliation and insecticide is sometimes applied for their control. Parasitoids, mainly Hymenoptera and Diptera, are among the most diverse and important natural enemies of caterpillars in these forests. However, due to their cryptic lifestyle and taxonomic difficulties, we lack knowledge on the impact of insecticide applications on complex host‐parasitoid networks. In a large‐scale field experiment, we tested the effect of spraying the lepidopteran‐specific insecticide Mimic (tebufenozide) on the abundance and community composition of both adult and larval parasitoids. We combined morphological identification, DNA barcoding and metabarcoding to identify parasitoids adult or inside caterpillars, both sampled by canopy fogging during an outbreak and two subsequent years. We analysed the abundance of parasitoids, community composition and network specialisation using statistical methods that account for sample incompleteness in host‐parasitoid data. For adult parasitoid assemblages, we found strong annual effects on abundance, with highest numbers of adult parasitoids occurring in the outbreak year, as well as on annual changes in community composition, but no effect linked to insecticide application. However, the abundance and species number of immature parasitoids revealed negative effects of insecticide application, while community composition was only affected by annual variation. Coverage‐based network analyses showed a reduction of taxonomic network diversity and network specialisation associated with insecticide application in the first 2 years. Synthesis and applications: This real‐world experiment shows that parasitoid populations respond immediately to large‐scale outbreaks but only limited to local disturbances. Results indicate that this group of natural enemies exhibits high mobility, enabling them to track host populations across large spatial scales. However, our observation of reduced network specialisation after insecticide application is a warning signal that ecosystem function, and consequently natural pest control services, may be impaired by human interference at the local stand scale.

Paleoclimate changes and ecosystem responses of the Bulgarian Black Sea zone during the last 26000 years

Multi-proxy analysis (spore-pollen, dinoflagellate cysts, other non-pollen palynomorphs (NPPs), radiocarbon dating and lithology) was performed on marine sediments from three new cores retrieved during the two cruise expeditions on board the Research Vessel “Akademik” in 2009 and 2011. The Varna transect comprises three cores extending from the outer shelf, continental slope and deep-water zone. The record spans the last 26000 years (all ages obtained in this study are given in calendar years BP (cal. yrs BP)). The pollen record reveals the spreading of steppe vegetation dominated by Artemisia and Chenopodiaceae, suggesting cold and dry environments during the Late Pleniglacial – Oldest Dryas (25903–15612 cal. yrs BP). Stands of Pinus and Quercus reflect warming/humidity increase during the melting pulses (19.2–14.5 cal. ka BP) and the Late Glacial interstadials Bølling and Allerød. The Younger Dryas (13257–11788 cal. yrs BP) coldest and driest environments are clearly demonstrated by the maximum relative abundance of Artemisia and Chenopodiaceae. During the Early Holocene (Preboreal and Boreal chronozones, 11788–8004 cal. yrs BP), Quercus appeared as a pioneer species and, along with other temperate deciduous arboreal taxa, formed open deciduous forests as a response to the increased temperature. The rapid expansion of these taxa indicates that they survived in Glacial refugia in the coastal mountains. During the Atlantic chronozone (8004–5483 cal. yrs BP), optimal climate conditions (high humidity and increased mean annual temperatures) stimulated the establishment of species-rich mixed temperate deciduous forests. During the Subboreal chronozone (5483–2837 cal. yrs BP), Carpinus betulus and Fagus expanded simultaneously and became more important components of mixed oak forests and probably also formed separate communities. During the Subatlantic chronozone (2837 cal. yrs BP to pre-industrial time), climate-driven changes (an increase of humidity and a cooling of the climate) appear to be the main drivers of the specific vegetation succession expressed by increased abundance of Alnus, Fraxinus excelsior and Salix along with lianas, suggesting formation of flooded riparian forests (so called ‘Longoz’) lining the river valleys along the Black Sea coast. The first indicators of farming and other human activities have been recorded since 7074 cal. yrs BP. The dinoflagellate cyst (dinocyst) assemblages have been analysed to assess the changes in the Black Sea environment over the last 26000 years in terms of fluctuation in paleoproduction and surface water conditions related to changes in climate, freshwater input and Mediterranean water intrusion. Two major dinocyst assemblages were distinguished: one dominated by stenohaline freshwater/brackish-water species and a successive one dominated by euryhaline marine species. The changes in the composition of the assemblages occurred at 7668 cal. yrs BP. The abrupt decrease of stenohaline freshwater/brackish-water species Pyxidinopsis psilata and Spiniferites cruciformis was followed upwards by a gradual increase in euryhaline marine species, such as Lingulodinium machaerophorum, Spiniferites belerius, S. bentorii and acritarch Cymatiosphaera globulosa. The first occurrence of euryhaline marine species took place synchronously with the onset of sapropel deposition. Modern marine conditions were established after 6417 cal yrs BP when an abundance of Mediterranean-related species, such as Operculodinium centrocarpum and Spiniferites mirabilis, along with other heterotrophic species, occurred. After the stable cold and dry environment during the Last Glacial Maximum, the phytoplankton record of core AKAD 11-17 shows that Pediastrum boryanum var. boryanum has a cyclical abundance associated with the deposition of four red-brown clay layers between 19.2 and 14.5 cal. ka BP. This event is associated with the major melting phase of European Ice drained by the Danube and Dnieper Rivers in response to climate warming observed after the end of the Last Glacial Maximum. During the Early Holocene, P. psilata, characterised by a preference to warmer temperatures, demonstrates its ecological optimum for growth concerning SST reaching maximum relative abundance of 94% between 11072 and 8638 cal. yrs BP. This maximum was interrupted by an abrupt significant short-term decrease in the relative abundance of P. psilata centred between 8500 and 8300 cal. yrs BP reflecting cold conditions similar to those of Younger Dryas. This finding, also confirmed by the rapid significant decrease of arboreal pollen, particularly of Quercus in the same studied core, is considered a regional expression of the well-known ‘8.2 ka cold event’ which is commonly linked to a meltwater-related perturbation of the Atlantic Meridional Overturning Circulation (AMOC) and associated collapse of oceanic northward heat transport. Our fossil pollen and dinocyst data confirm that the high amplitude temperature anomaly associated with ‘the 8.2 ka cold event’ may have also occurred in south-eastern Europe, at lower latitudes of the western Black Sea coastal area, most probably due to atmospheric transition and/or river discharge.

Temporal changes in species richness, composition and diversity of the forest stands over 36-year period, Western Himalaya, India

This study investigates the temporal changes in species richness, composition, and diversity in forest stands spanning a 36-year period in the Western Himalaya. Four forest stands (subtropical Sal-forest, subtropical Chir-pine forest, temperate Banj-oak forest, and temperate Mixed-oak Forest) studied in 1980–1981 were resurveyed using similar methods. Over the past 36 years, 19 new species have been recorded in the four stands; eight species planted and eleven species naturally introduced. Dominant species continue to dominate in the forest stands. However, their contribution to the total tree density has decreased over the year. Species diversity, richness, and evenness increased in all forests except the Sal stand. Three species were newly introduced in the Sal stand, seven in the Chir-pine stand, eight in the Banj-oak stand, and seven in the Mixed-oak stand. The highest similarity in species composition was observed in the Sal stand (59 %), followed by the mixed-oak stand (57 %), Chir-pine stand (50 %), and Banj-oak stand (47 %). The results indicate an increase in tree density across all sites, with the Mixed-oak forest exhibiting the highest increase in tree density due to least biotic pressure. The findings of this study, based on two-time composition datasets, provide valuable insights into forest dynamics, supporting biodiversity conservation and management planning.

Structural and Successional Dynamics of Old-Growth Mixed Oak Forests in the West Qinling Mountains

Understanding the composition and structure of forest trees is crucial to comprehending the properties and functions of forests. It also helps in implementing effective management strategies for sustainable resource utilization. Our study analyzed the structural dynamics of the old-growth mixed oak forests in the Xiaolongshan Forest region, focusing on three long-term monitoring plots (A, B, C). We examined the tree species composition, diameter distribution, mortality, and recruitment dynamics of different successional species groups, as well as the spatial distribution patterns of living and dead trees, with surveys conducted every five years. The findings indicate: (1) Plot A experienced a decline in stand density and species diversity during the survey period, with the Importance Value Index (IVI) of pioneer successional species continually decreasing in plots B and C. (2) The tree diameter distribution structure in plot A significantly differed from other plots, showing notable change between 2007 and 2012. (3) All plots exhibited lower, well-balanced community-level demographic parameters based on stem number, but a higher recruitment rate for later successional species groups based on basal area. (4) Dead individuals in plot A had a slight clustering distribution, while the other plots showed a random distribution. We conclude that the individual growth rate significantly impacts the dynamics of the natural Quercus aliena var. acuteserrata forest, with pioneer species groups being gradually replaced by early or late-successional species groups in the succession process.

Spatial Distribution and Ecological Determinants of Coexisting Hybrid Oak Species: A Study in Yushan's Mixed Forest.

Ecological niche partitioning is crucial in reducing interspecific competition, fostering species coexistence, and preserving biodiversity. Our research, conducted in a hybrid mixed oak forest in Yushan, Jiangsu, China, focuses on Quercus acutissima, Q. variabilis, Q. fabri, and Q. serrata var. brevipetiolata. Using Point Pattern Analysis, we investigated the spatial relationships and ecological trait autocorrelation, including total carbon (TC), nitrogen (TN), phosphorus (TP), potassium (TK), and breast height diameter (DBH). Our findings show aggregated distribution patterns within the oak populations. The Inhomogeneous Poisson Point model highlights the impact of environmental heterogeneity on Q. variabilis, leading to distinct distribution patterns, while other species showed wider dispersion. This study reveals aggregated interspecific interactions, with a notable dispersal pattern between Q. acutissima and Q. variabilis. We observed significant variability in nutrient elements, indicating distinct nutrient dynamics and uptake processes. The variations in total carbon (TC), nitrogen (TN), phosphorus (TP), and potassium (TK) suggest distinct nutrient dynamics, with TK showing the highest variability. Despite variations in TC, TK, and TP, the species did not form distinct classes, suggesting overlapping nutritional strategies and environmental adaptations. Furthermore, spatial autocorrelation analysis indicates strong positive correlations for DBH, TC, and TP, whereas TK and TN correlations are non-significant. The results suggest habitat filtering as a key driver in intraspecific relationships, with a finer spatial scale of ecological niche division through TC and TP, which is crucial for maintaining coexistence among these oak species.

Seasonal and long-term changes in litterfall production and litter decomposition in the dominant forest communities of Western Himalaya

Understanding changes in litter fall is paramount for effective management, as it directly impacts ecosystem health, nutrient cycling, and overall biodiversity. It informs strategies for conservation, land use planning, and mitigating ecological disruptions. Therefore, present study investigates the seasonal and long-term changes in litterfall dynamics within the dominant forest communities of Western Himalaya. A total four distinct forest ecosystems, including Sal, (Shorea. robusta) Chir-pine (Pinus roxburghii), Banj-oak (Quercus leucotrichophora), and Mixed-oak (Q. leucotrichophora, Q. floribunda and Q. lanuginosa) forests were selected for the study. The total annual litter production across the forest stands varied from 741.59 to 841.22 g−2, with the highest recorded in the Banj-oak stand (841.22 g−2) and the lowest in the Sal stand (741.59 g−2). Leaf fall reported for the highest proportion of total litterfall (64.88% to 71%) across the forest stands, and peak litterfall was observed during the summer months in all forest sites. The leaf litter decomposition rate of selected species shows significant variation (F5, 10 = 3.41, p < 0.05) between species. Interestingly, litterfall production increased in all forest sites from 1980 to 82 to 2017–19. However, no significant changes were observed in the decomposition rate. The findings reveal significant variations in litterfall dynamics across different forest ecosystems, with leaf fall contributing substantially to total litter production. The observed increase in litterfall production over the studied period highlights the need for continued monitoring and adaptive management strategies to address potential ecological implications. These insights are invaluable for informing conservation efforts, land use planning, and mitigation strategies aimed at preserving ecosystem health, sustaining biodiversity, and ensuring the long-term resilience of Western Himalayan forests in the face of environmental change.

The vegetation history of Lake Mert and its surroundings for the last 6600 years (Kırklareli, NW Türkiye)

The primary aim of this study is to determine the Middle-Late Holocene vegetation history of the İğneada Longoz (Floodplain) Forests around Lake Mert, located in Kırklareli, using high-resolution palynological analysis conducted on the MRT-04 core. Pollen analyses was performed on sediment samples collected from 67 different levels within the core. Pollen counting and identification were performed using a Leica DM750 light microscope, with a minimum of 500 terrestrial pollen grains counted per sample. The age of the lake was determined to be 6600 years old through radiocarbon dating of the core. According to the findings from the pollen analysis, deciduous mixed oak forests have dominated the region in and around Lake Mert for the past 6600 years. Within these mixed oak forests, Quercus cerris type (deciduous oaks) is predominant, with notable contributions from Fagus, Carpinus, Corylus, and Tilia. This forest composition has displayed a consistent pattern, except for changes attributed to the expansion of temperate species and human influences. The distribution of mixed oak forests began to decline around 1360 BP, coinciding with a significant increase in the presence of Alnus, Fraxinus, and Ulmus. These trees are characteristic species of floodplain forest and indicate the initiation of the formation of the İğneada Longoz Forests after 1360 BP. Furthermore, around 420 BP, there was a substantial decrease in the pollen percentages of Quercus and Fagus. During this period of declining mixed oak forests, Plantago and Ambrosia appeared for the first time in the pollen diagram. The reduction in arboreal plant taxa and the rise of herbaceous taxa such as Plantago, Ambrosia, and Poaceae, which serve as indicators of human impact, signify the conversion of forested areas into agricultural and pasture lands.

Changes of the composition of the Noctuoidea fauna along a geographical gradient in the northeastern part of the Carpathian Lowland

The northeastern part of the Carpathian Lowland is one of the most species-rich parts of the region, despite the long-term and sometimes extreme changes in land use. The fragmented remains of formerly contiguous forests maintain a significant part of the wildlife living in different oak, mixed oak, and gallery forest, and even faunas of connected grassland habitats. To reveal how the parallel Carpathian and Pannonian effects form the local insect fauna, the Noctuoidea assemblages of eight forest patches were assessed and compared, based on the distribution data of 479 species. Three types of assemblages were designated, with similar diversity but different compositions. The most unique and valuable ones can be found in the colline area of Transcarpathia, where the high habitat diversity supported by the topography promotes the coexistence of the species of humid forest fauna and many steppic and southern elements. The protection and planned management of these remained forest patches and their network in international cooperation can maintain a significant part of the fauna of the affected regions.

Evidence for antagonistic effects of climate change and exotic pathogens on regeneration of Mediterranean forests

Abstract Understanding the interactive effects of global change drivers on tree demography is fundamental for realistic predictions of future forest dynamics. Multiple studies have shown increasing drought and exotic pathogens to severely threaten forest persistence by increasing mortality and decreasing growth of adult trees. However, much less is known about their effects on regeneration, and how they might affect seedling performance in additive and non‐additive (synergistic or antagonistic) ways. Here we aimed to fill this gap by experimentally exploring the effects of increasing drought and soil‐borne pathogens on tree regeneration in two types of mixed oak forests (Quercus suber‐Q. canariensis and Q. suber‐Olea europaea) invaded by the exotic soil‐borne oomycete Phytophthora cinnamomi, one of the most aggressive plant pathogens on earth. We conducted a seed sowing experiment with oomycete‐specific fungicide taking advantage of rainfall exclusion infrastructures that excluded 30% of the annual rainfall, simulating predictions of climate change models for Mediterranean systems. Seedling emergence, survival and growth of the three tree species were followed during 3 years. We found that neutral or positive drought effects on regeneration dominated over negative effects in the tree community. Moreover, most positive drought effects on the dominant species (Q. suber) were not direct, but indirectly mediated by soil‐borne pathogens. This was shown by the fact that positive drought effects disappeared with fungicide application. Synthesis: Overall, our results suggest that rainfall reductions predicted by climate change models for the Mediterranean region might have minor direct negative effects on early regeneration of tree species, but could play a major indirect role by limiting the negative effects of exotic pathogens on highly susceptible tree species. These findings highlight that antagonisms among global change drivers should be recognized as important forces that might slow down the current loss of tree health.

Tardigrade diversity and community composition across Norwegian boreal forests

Abstract Tardigrades are common in many terrestrial environments and habitats. Although little is known on their ecological preferences, previous studies found diversity and community composition significantly affected by various variables. This study associated tardigrade species’ records with climatic variables, forest type, and substrate categories exploring tardigrade diversity and species communities to find associations with ecological characteristics of Norwegian forests. A total of 17 473 specimens were identified, encompassing 131 species (including putatively new species) from 305 samples of different substrates (leaf litter, bryophytes, and lichens). Bryophytes and lichens of samples were classified according to the main species, and growth form, and associated with tardigrade species and sample metadata. Tardigrade species’ richness was related to climatic variables and forest type, increased with precipitation, decreased with summer temperature, and not varied with precipitation seasonality. Although there was an unbalanced representation of substrate categories in the different forest types, some tendencies were detectable. Mixed oak and birch forests reached the highest species’ richness. Tardigrade community composition varied between substrate categories and, to a lesser degree, between forest types, but not with climatic variables. Our study highlights the importance of large-scale variables on tardigrade diversity, and substrate categories for tardigrade community composition.

Predator odor can reduce acorn removal by granivorous rodents in mixed oak forest stands

Developing better practices for rodent pest control is of high importance to reduce damage during forest restoration and in crop production. For example, during direct seeding with large and highly attractive seeds such as acorns, most seeds will disappear due to consumption or dispersal if not protected. An unexplored concept in reducing rodent damage is the use of repellents derived from predators. We tested the efficiency of three volatile compounds (2-propylthietane, 2-phenylethylamine and indole) associated with predators as rodent repellent candidates and scored the reduction of acorn (Quercus petraea) removal at two field sites in southern Sweden. We further investigated at what distance (5 cm, 10 cm, and 15 cm) from the odor source the odors were efficient in lowering the removal of acorns. Removal was lowest with 2-propylthietane (25–45 % of acorn removal), followed by 2-phenylethylamine (75–95% acorn removal) at 5 cm. Indole failed to decrease acorn removal and did not differ significantly from the control treatments. In the control treatments, almost all acorns (95–100%) were removed from the plots during the 48-hour sessions at both sites, and the acorns were removed faster than in the other treatments. Removal increased with distance from the 2-propylthietane odor dispenser at both field sites. Here, the lowest acorn removal occurred at 5 cm from the odor disperser. Our short time experiment shows for the first time the potential of using 2-propylthietane for short-term protection of acorns from foraging by granivorous rodents in oak woodlands. To help increase the reliability of direct seeding as a method for regenerating and restoring forests, future studies should investigate whether the range and longevity in the field of predator odor formulations can be improved.

Effects of Wildland Fuel Composition on Fire Intensity

Assessing the characteristics of fuel flammability during fire is of major significance regarding fire intensity and fire spread control. Under the background of shifting forest composition from heliophytic to mesophytic species in mixed-oak forests, our objective is to determine the impacts of species-driven changes in fuel flammability characteristics and the specific relationships between fuel ignition variations at the species level. Oak and maple fuels were collected from ninety-four plots established in Zaleski State Forest, Ohio. A total of 30 combustion samples were separated (15 oak samples and 15 maple samples), with each combustion sample weighing 20 g to ignite under a laboratory fume hood. Our results determined that oak fuel showed significantly higher flame temperatures than maple fuel, and the fuel consumption and combustion duration time both varied between oak and maple fuel. These findings indicated that the shift from oak forest to mesophytic species could change a fire’s behavior. Combined with the cooler, moister, and less-flammable forest conditions generated by these mesophytic species, fires may not be able to reach their historical fire intensities, suggesting that updated data and new insights are needed for fire management.

Spatial decision-making in acorn dispersal by Eurasian jays around the forest edge: Insights into oak forest regeneration mechanisms

Seed dispersal is key to forest regeneration and often depends on the behavior of seed scatter-hoarding animals. However, our understanding of the decision-making of scatter-hoarders and how vegetation structure at different spatial scales affects dispersal patterns remains limited. We studied seed dispersal at the forest edge across multiple spatial scales (habitat, sub-habitat, microsites) between and within habitats with distinct vegetation structure. Our model system is a mixed-oak forest dominated by holm oak (Quercus ilex) and an adjacent shrubland dominated by the shrub Retama sphaerocarpa. For three years, we tracked the movement of acorns by a keystone scatter-hoarder, the Eurasian jay (Garrulus glandarius). At the coarse scale, jays did not show a preference for caching acorns either in the forest or in the shrubland when the source tree was within the forest. However, when the source tree was on the forest edge or was an isolated oak tree in the shrubland at < 200 m from the forest, jays showed a preference for caching in the forest. Conversely, when isolated oak trees were > 200 m from the forest, all acorns were dispersed in the shrubland. Dispersal distances were shorter within the forest than within the shrubland. At an intermediate scale, within the shrubland jays preferred to cache acorns under large retamas while avoiding gaps. In the forest, jays also avoided gaps and preferred certain woody species and vertical vegetation structures, although these preferences varied across feeders. At the finest scale, jays selected stones as cache microsites. Thus, the selection of acorn caching sites followed a hierarchical and selective top-down process across different spatial scales. The position of the source trees in the landscape determined habitat preference and dispersal distance. We detected different preferences in response to similar vegetation structure and composition, indicating that the decision-making process is flexible at an intermediate scale that generates diverse spatial patterns of dispersal. This study sheds light on the intricate decision-making process of seed caching by scatter-hoarders, and the consequences for the spatial patterns of seed dispersal as well as the expansion and regeneration of oak forests.

Environment and Plant Use at La Tourasse (South-West France) at the Late Glacial–Holocene Transition

Abstract The aim of this study is to present new data on vegetation dynamics and plant collecting practices during the Late Glacial and the Early Holocene in southwestern France. La Tourasse cave is located in the Pyrenean piedmont plain, where the Azilian cultural complex was initially defined. The last excavations of the site took place in the 1980s and 1990s and the recovered materials are currently being studied or revisited from a multidisciplinary perspective. We present here the results of the charcoal analysis performed on La Tourasse’s Azilian (ca. 13000–11500 cal. BP) and Mesolithic (ca. 10500–9000 cal. BP) levels, complemented by the study of a small seed assemblage. Our results document the shift from an open landscape towards a forested environment, with the gradual passage from open vegetation dominated by shrubs of the Rose family (Prunus spp.) to the mixed oak forest, which speaks in favor of the biochronological coherence of this sequence. However, marked differences in taxonomic richness and state of the wood from one level to another, unrelated to the prevailing environmental conditions, suggest variable behavior of humans toward wood that could be the result of differing mobility strategies, hearth functionalities, or taxonomic preferences.

Corticolous lichen communities in Algerian climax forests

AbstractThe great extension of forests in the Djebel El Ghorra massif of El Kala National Park (north‐eastern Algeria) allowed us to recognise three distinct forest formations: cork oak stands (Quercus suber), zeen oak stands (Quercus canariensis) and mixed oak (Quercus suber and Quercus canariensis) forest. Their peculiarities showed ideal ecological characteristics for the colonisation of corticolous lichens the two phorophytes. The three forest formations were sampled between 2017 and 2022. The identification of the taxa is based on stereo‐microscopic examinations and usual chemical tests. Systematic surveys were conductedand allowed us to establish a list of 141 lichen taxa divided into 30 families.

Spatially explicit modeling of disease surveillance in mixed oak-hardwood forests based on machine-learning algorithms

Incidences of disease, dieback, decline or mortality, some of which induced or enhanced by climate change, threaten the sustainability of forest stands in many ecosystems. Spatially explicit prediction of disease onset remains challenging, however, due to the involvement of several causative agents. In this paper, we developed a generic framework based on machine-learning algorithms and spatial analyses for landscape-level prediction of oak disease outbreaks caused by the charcoal fungus Biscogniauxia mediterranea in a mixed-oak forest of Mediterranean climate. For prediction, we used a set of fifteen causative factors as a cross-function of soil, site and stand-related predictors. A total of 80 sample plots, including 1134 affected trees, were surveyed and used for the modeling process at the 5600-ha landscape level of the southern Zagros, Iran, where the disease occurs in roughly 25% of forest lands. Ten machine learning algorithms were explored and the performance of each algorithm to predict oak disease outbreak was evaluated. The modeling framework used maximum entropy to remove the least influential variables and build the status-quo management scenario to which the results of the prediction models were compared. Results showed that the random forests algorithm (AUC = 0.96: Precision = 0.71: Accuracy = 0.90: F-Measure = 0.70) achieved significantly better results than the status-quo management (Precision = 0.13: Accuracy = 0.67: F-Measure = 0.12) and any other algorithm. Soil chemical properties (NPK, organic carbon and EC) and landform predictors (slope, distance to roads, and TWI) were major forecasters of oak disease outbreak identified by the random forest algorithm. Geostatistical analysis enabled the creation of a map that identified sites at higher risk of infestation, allowing epidemiologists and forest managers to find sites likely to be infested. Consequently, financial resources can be allocated and management practices such as sanitation felling treatments applied across large forest landscapes to minimize the risk of spread and severity to uninfested high-value trees on nearby or adjacent land zones that are in the early stage of epidemics.

Effects of Oak Processionary Moth (Thaumetopoea processionea L.) Outbreaks on the Leaf Performance and Health of Urban and Forest Oak Trees (Quercus robur L.) in Brandenburg, Germany

Forest insects are among the most important factors of disturbance in European forests. The increase in and duration of drought stress events due to climate change not only increase the vulnerability of rural and urban forests but also predispose weakened stands to insect pest calamities. In this context, many German and European forest research institutes and environmental institutions report an increase in the densities and calamity developments of the oak processionary moth (Thaumetopoea processionea L.) not only in oak and mixed-oak forests but also in smaller areas where oak trees regularly occur, e.g., parklands, urban areas, copses, avenues, recreational forests, etc. It is expected that the oak processionary moth (OPM) will benefit from the overall weakened vitality of both individual oaks and oak stands in the future and that mass outbreaks will occur at an increased frequency. This paper reports on the effects that the OPM can have on tree performance for rural forest and urban oak trees by applying the chlorophyll fluorescence non-destructive diagnostic method for the identification and quantification of damage to oak leaves. The aim of the study was to investigate the effects of OPM frass activity on tree leaf health using chlorophyll fluorescence measurements, comparing infested host oaks with non-infested oaks in urban and forest environs. The study assessed: 1. the quantum efficiency of photosystem II (PS II), which counts as an indicator for leaf conditions, 2. the performance index, which indicates the efficiency of the photosynthetic light reaction, 3. the energy loss of the photosynthetic reaction, which is an indicator for cell damage, and 4. the degree of open reaction centers in PS II, which indicates how well light energy can be absorbed for photosynthesis. Infested urban and rural oaks showed a significantly reduced quantum yield of PS II by up to 10% compared to non-infested oak leaves. The leaf performance was significantly reduced by up to 35% for infested urban oaks and by up to 60% for infested forest oaks, respectively. The energy losses were two times higher for infested urban and forest oaks. However, OPM infestation led to a higher reduction in the photosynthetic performance in the leaves of forest oaks compared to that of urban oaks. In order to avoid permanent damage, suitable countermeasures must be taken quickly, as, immediately after pest infestation, the performance decreases significantly. A lower performance means a significant loss in biomass production as well as in tree vitality.

BRYOCRUMIA VIVICOLOR, A RHEOPHYTIC, HYPNACEOUS MOSS, NEW TO THE WESTERN HIMALAYAS, INDIA

The Indian Himalayan sector is well known to support the diversified bryophyte species and communities due to varied phytoclimatical conditions met within different dissected topographical zones. Many potential wilderness areas are still waiting to be explored in terms of their exuberant bryodiversity. During a bryoexploratory survey of an unexplored high-altitude area in the Garhwal Himalayan region, we came across an interesting rheophytic moss Bryocrumia L. E. Anderson. The genus Bryocrumia is represented in India by two species, viz. B. vivicolor (Broth. et Dixon) W. R. Buck and B. malabarica Manju, Prajitha, Prakashkumar et W. Z. Ma. Both of these pleurocarpous species are known to be confined in the southern part of the country. From the Indian Himalayan sector, this moss genus has never been documented earlier. Recently, B. vivicolor has been reported for the first time from the Tungnath area (2,100–3,000 m above sea level) in the Garhwal region of Uttarakhand state as a new addition to the Western Himalayan moss flora, indicating its new distributional range. This hypnaceous moss was found colonising the slopy, wet, submerged rock surfaces along small streams and seepages in mixed oak forests on way to Tungnath. The key characteristics include its rheophilic habit, stem lacking central strand, variable leaf forms, indistinct double costa and round to obtuse leaf apex with prorate tip cells. The present paper provides taxonomic details of this rare moss, representing its wide geographical distribution in India.

Seeing past the green: Structure, composition, and biomass differences in high graded and silviculture-managed forests of similar stand density

Forests of the eastern United States (US) mostly comprise a mix of stands managed following silvicultural principles and stands managed with exploitative timber harvesting practices. These stands can have similar stand densities (e.g., basal area per hectare) but vary vastly in structure, composition, and biomass and carbon storage. High grading, a prevalent exploitative timber harvesting practice in the eastern US, is of particular concern because it can negatively affect future forest health and productivity. This study quantifies differences in forest structure, composition, and biomass and carbon storage between high graded stands and stands that received a seed/establishment cut of a uniform shelterwood regeneration sequence treatment, which is a comparable and well-established silvicultural method used to regenerate mixed-oak forests. It focuses on mixed-oak forests (mixed-Quercus), where the effects of high grading have been understudied, and uses a sample with broader spatial coverage than previous studies. The sample comprised nine stands that were known to have been high graded 8–15 years ago and nine stands that received the seed/establishment cut of a uniform shelterwood regeneration sequence. Stand were systematically sampled using fixed-area plots. Field measurements were collected and used to calculate metrics describing forest structure and function. The structure of high graded stands was characterized by a higher proportion of trees with poor health and/or form compared to shelterwood stands, with 18.3 % less acceptable growing stock and trees with lower crown compaction. Diameter distributions of high graded stands were characterized by numerous small trees and few large-diameter trees. Spatial variability of overstory trees was contingent on the tree size range evaluated, with a larger variability of sawtimber-sized trees (trees ≥ 29.2 cm in diameter at breast height) in high graded stands. High graded stands also had 2.2 times fewer oak trees (Quercus spp.) in the overstory canopy, 17,897 fewer seedlings per hectare (ha), and 45 Mg/ha less biomass than shelterwood stands. These results indicate that high grading generally degrades mixed-oak forests and impairs their long-term capacity to supply vital ecosystem services such as habitat for specific wildlife species, carbon storage, and high-quality wood products.

Estimating the self-thinning boundary line for oak mixed forests in central China by using stochastic frontier analysis and a proposed variable density model.

A suitable self‐thinning model is fundamental to effective density control and management. Using data from 265 plot measurements in oak mixed forests in central China, we demonstrated how to estimate a suitable self‐thinning line for oak mixed forests from three aspects, i.e., self‐thinning models (Reineke's model and the variable density model), statistical methods (quantile regression and stochastic frontier analysis), and the variables affecting stands (topography and stand structure factors). The proposed variable density model, which is based on the quadratic mean diameter and dominant height, exhibited a better goodness of fit and biological relevance than Reineke's model for modeling the self‐thinning line for mixed oak forests. In addition, the normal‐truncated normal stochastic frontier model was superior to quantile regression for modeling the self‐thinning line. The altitude, Simpson index, and dominant height–diameter ratio (Hd/D) also had significant effects on the density of mixed forests. Overall, a variable density self‐thinning model may be constructed using stochastic frontier analysis for oak mixed forests while considering the effects of site quality and stand structure on density. The findings may contribute to a more accurate density management map for mixed forests.