Oak Group Research Articles

Japanese Oak Wilt Disease decreased survival probability and mean lifetime of tree populations in a secondary natural forest

ABSTRACT The purpose of this study was to assess the effects of Japanese Oak Wilt Disease on mortality in a tree population. The study site was the permanent plot of 0.26 ha established in the secondary forest dominated by Abies firma, Tsuga sieboldii and Quercus serrata at the University of Tokyo Chiba Forest in the southeastern part of the Boso peninsula, Japan. We set the two observation periods of 1999–2008 and 2009–2021, and Japanese Oak Wilt Disease invaded the study site in the middle of the second period. We collected tree age data for both alive and dead trees in the two periods based on semi-nondestructive drilling measurements for trees using a RESISTOGRAPH. Survival analyses were conducted on the second-period data, and the demographic metrics such as mortality ratios and mean lifetimes were compared between the two periods. The results showed that: the mortality ratio of the tree population at old ages, where oaks (Quercus serrata) concentrated in their age distribution, significantly increased; the effect of the oak group was significant on mortality in the tree population; the hazard for the oak group was 24 times the hazard for the other tree species group; the survival curve reflected the mass mortality in oaks at old ages, which led to the decrease of mean lifetime less than half. Consequently, it was implied that the effects of Japanese Oak Wilt Disease impacted the demographic metrics of oak trees.

Divergence and reticulation in the Mexican white oaks: ecological and phylogenomic evidence on species limits and phylogenetic networks in the Quercus laeta complex (Fagaceae).

Introgressive hybridization poses a challenge to taxonomic and phylogenetic understanding of taxa, particularly when there are high numbers of co-occurring, intercrossable species. The genus Quercus exemplifies this situation. Oaks are highly diverse in sympatry and cross freely, creating syngameons of interfertile species. Although a well-resolved, dated phylogeny is available for the American oak clade, evolutionary relationships within many of the more recently derived clades remain to be defined, particularly for the young and exceptionally diverse Mexican white oak clade. Here, we adopted an approach bridging micro- and macroevolutionary scales to resolve evolutionary relationships in a rapidly diversifying clade endemic to Mexico. Ecological data and sequences of 155 low-copy nuclear genes were used to identify distinct lineages within the Quercus laeta complex. Concatenated and coalescent approaches were used to assess the phylogenetic placement of these lineages relative to the Mexican white oak clade. Phylogenetic network methods were applied to evaluate the timing and genomic significance of recent or historical introgression among lineages. The Q. laeta complex comprises six well-supported lineages, each restricted geographically and with mostly divergent climatic niches. Species trees corroborated that the different lineages are more closely related to other species of Mexican white oaks than to each other, suggesting that this complex is polyphyletic. Phylogenetic networks estimated events of ancient introgression that involved the ancestors of three present-day Q. laeta lineages. The Q. laeta complex is a morphologically and ecologically related group of species rather than a clade. Currently, oak phylogenetics is at a turning point, at which it is necessary to integrate phylogenetics and ecology in broad regional samples to figure out species boundaries. Our study illuminates one of the more complicated of the Mexican white oak groups and lays groundwork for further taxonomic study.

Waterlogged wood remains found in a Late Bronze Age settlement (İnönü Cave) on the Western Black Sea coast of Türkiye

The remains of wooden structures belonging to the Late Bronze Age were unearthed during the excavations carried out in the İnönü Cave, which is located approximately 25 km inside the Ereğli district of Zonguldak, on the western Black Sea coast of Türkiye. Thanks to the special conditions of the cave, the woods that makes up the structures that have survived until today has been examined within the scope of this study. All wood flooring elements examined in this study consist of water-filled wood, except for one example (NNDK-1), which has semi-water-filled properties. In the construction of the wooden floor, one oak species from the white oak group (probably Quercus petraea (Matt.) Liebl.) and one pine species from the Sylvestris group (probably Pinus nigra Arnold), Alnus glutinosa (L.) Gaertner and Acer L. sp. were used. In addition, the most used genus in its construction was oak (Quercus L., section Quercus). The inhabitants of İnönü cave in the Late Bronze Age must have met their wood needs from nearby local resources. Wood anatomical analysis pointed out the occurrence of riverine forests formed by Black alder along the streams and temperate broadleaf and mixed forests formed by Sessile oak, maple, and Black pine in İnönü cave and its vicinity. These, together with others like Fagus orientalis Lipsky, Carpinus betulus L., Carpinus orientalis Mill., Salix alba L., and Populus nigra L., are the genera/species present in the region today.

Rumen protozoa population and carbohydrate-digesting enzymes in sheep fed a diet supplemented with hydrolysable tannins

Abstract The aim of the study was to compare the effect of adding different sources of hydrolysable tannins to the sheep diet on protozoa population and carbohydrate digestion in the rumen. The study was performed in 3 Polish Lowland ewes fistulated to the rumen in a 3 × 3 Latin square design. Control sheep (CON) received (g/d): meadow hay (600), barley meal (300), soybean meal (100) and vitamin-mineral premix (20). Sheep from the experimental groups were additionally administered 12.6 g/kg DM oak bark extract (OAK) and 3.91 g/kg DM tannic acid (TAN ). The net consumption of tannins was approx. 0.4% DM for both additives. Regarding the count of protozoa, a significant interaction between diet and sampling time was documented for all ciliates (P<0.01), with a significant effect of both factors when considered separately. Experimental diets reduced the number of total protozoa and Entodinium spp. (before feeding, 2 and 4 h after feeding; P<0.01), while increasing the abundance of Isotricha spp. population (4 h after feeding; P<0.01) in the rumen. Interestingly, the count of Ophryoscolex spp. after feeding the TAN diet increased before feeding and 2 h after feeding in comparison to the CON and OAK groups, respectively, and subsequently decreased compared to the CON diet (4 and 8 h after feeding, P<0.01). A significant interaction between the diet and sampling time was observed for xylanolytic activity (P<0.01) in the rumen, with a significant effect of sampling time, which decreased its activity in CON (after feeding) and OAK sheep (2 h after feeding; P<0.01). For amylolytic activity (P<0.10), there was a trend towards a significant interaction between experimental factors, with a significant effect on both diet and sampling time. Detailed analysis showed that the TAN diet significantly reduced amylolytic activity 2 h after feeding compared to the CON group (P<0.05). In conclusion, the TAN diet significantly reduced the number of total protozoa and Entodinium spp., which consequently reduced amylolytic activity in the rumen, without any significant effect on pH and carbohydrate fermentation in the rumen.

Gallnut and its identification as a herb in traditional Chinese medicine

Gallnut (Mo Shi Zi), as one of the herbs popularly used in traditional Chinese medicine, came into China from Persia in the Northern Wei Dynasty. Gallnut was translated into different names from Persian into Chinese. This study attempted to identify its names, sources and nature by starting with Mo Shi Zi () and comparing with its relevant names Mo Shi Zi(),Ba Lv Zi () and Wu Bei Zi (). It was found that'', meaning black, in Mo Shi Zi () did not make sense because it neither matched the pronunciation in translation nor interpreted the medical meaning of Mo Shi Zi (). Mo Shi Zi () and Ba Lv Zi() were the same herb in traditional Chinese medicine. In Greek and Arabic classic books, Bullut referred to oak groups and their galls, but not Ba Lv Zi (). Ba Lv Zi () in these books referred to Omphacitis. Mo Shi Zi () referred to insect galls in the family of Quercus infectoriain Xi Yao Da Cheng, a book from overseas, and Wu Bei Zi ()appeared in the annotated text of Mo Shi Zi () as a similar herb. It was found that in traditional Chinese medicine, Mo Shi Zi () and Wu Bei Zi( ) were two different herbs, but could be interchanged in their medical nature.

Evaluating the impact of prescribed surface fire on seedlings in the Central Hardwood Region, USA

Abstract Oak (Quercus) is being successionally replaced by maple (Acer) across much of the eastern deciduous forest. Past research on the close relationship between oak and fire has led forest managers to use prescribed surface fires to deter this replacement. However, there has not been a comprehensive evaluation of the effectiveness of prescribed fire by managers, particularly in the Central Hardwood Region. For example, it is not known how many repeat applications of prescribed fire are needed to accumulate enough oak reproduction to successfully re-establish oak-dominated stands. Tree reproduction and midstory composition were systematically surveyed across 63 mature, oak-dominated stands ranging in prescribed fire histories and aspects on the Hoosier and Wayne National Forests in southern Indiana and Ohio, respectively. These stands represent the vast majority of stands burned to promote oak regeneration since 1990 in these two National Forests. Across all sites, seedlings in the white oak group (section Quercus) and red oak group (section Lobatae) comprised 47.8 ± 3.3 per cent and 8.2 ± 1.6 per cent (mean ± SE), respectively, of all seedlings. In comparison, common competing species (maples and American beech) comprised 5.4 ± 1.4 per cent of all seedlings. Mid- and overstory basal area, percent slope, years since last burn, and total number of burns significantly affected oak seedling density. Greater increases in taller, competitive oak seedling density occurred after sites had been burned three times and with high frequency (≤4 years between burns). However, results also suggest that if an established midstory already exists or fire has not been used on the landscape for almost a decade, repeat applications of prescribed fire will not likely increase oak regeneration in the short term without concurrent treatment of midstory stems.

Revue documentaire et nouvelles perspectives de l’anatomie du bois aidant à mieux comprendre et lutter contre le flétrissement du chêne

Oak wilt, which develops in the outer sapwood, is the most destructive disease of oaks in the United States. Species of red oaks are more susceptible to this disease than white oak species and are more likely to facilitate the spread of the pathogen Bretziella fagacearum. To prevent its establishment in new areas, phytosanitary certificates are mandatory for commercial trade, as is the inspection of logs to confirm identification. A literature survey and the results of our assays with seven oak species confirm that it is easy to identify wood of the red and white oak groups using anatomical features. Specifically, earlywood vessels are generally open in red oaks, while they appear occluded with tyloses in white oaks. Such plugs are the consequence of air embolism (cavitation) and not the cause of the wilting process. Although these wide vessels are efficient for water transport, they are vulnerable to cavitation that appears to favour the growth of the oak wilt pathogen. Compartmentalization of infected wood succeeds in restraining cavitation and pathogen spread, allowing some trees to recover from oak wilt.

Double Bark Thickness Estimation Models of Common European Broadleaved Species for Harvester Timber Volume Estimation in Czechia

The share of the annual volume of harvester-produced timber in Czech forest bioeconomy has increased in the last decades. To estimate under-bark timber volume, harvester systems allow choosing between two different bark deduction models – diameter band (DBM) and linear model. However, linear models were not calibrated for the conditions of Czech forestry. Therefore, the objective of this research was to develop, for local conditions in Czechia, linear functions for estimating the double bark thickness of two groups of broadleaved species (beech and oak) and to test their viability based on real harvest data. To create the linear functions, official Czech cubing tables were used. Data from real harvests were gathered from fifteen harvesters. A sample containing 4995 logs belonging to the beech group was analyzed using descriptive statistics and the Paired Wilcoxon tests. The mean double bark thickness for beech group was 15.1 mm (polynomial and linear model). For oak group, it was 15.48 mm (polynomial) or 15.49 mm (linear). The results of real harvests for beech group revealed that the mean double bark thickness estimated by the polynomial function was 7.08 mm. The linear function estimates were closer to the value estimated by the polynomial (6.84 mm) than DBM estimates (6.68 mm). Therefore, we can state that the newly developed linear models can be used in fully mechanized harvesting instead of manual bark deduction methods in Czechia.

Impacts of oak-focused silvicultural treatments on the regeneration layer nine years posttreatment in a productive mixed-oak southern Appalachian forest

Oaks (Quercus spp.) are foundational species in forests and woodlands in the eastern USA. An oak regeneration bottleneck has occurred throughout its range in recent decades, and refining silvicultural treatments to localized conditions has become a focus in addressing this problem. This study was developed to determine species regeneration dynamics among oak and oak competitors on productive sites in response to silvicultural treatments in oak-dominated southern Appalachian mountain forests. The treatments were: an oak shelterwood treatment (25–30% basal area [BA]) reduction through midstory removal with herbicides); a prescribed fire treatment (two, late-dormant season prescribed fires occurring over a 9-yr period); a shelterwood and burn treatment (one, late-dormant season prescribed fire 3–5 yr following 30–40% BA removal); and an unmanaged control. To determine treatment impacts on the regeneration layer, changes in relative and absolute importance values and stems ha-1 (germinants up to stems ≤ 4.9 cm diameter at breast height [DBH]) were calculated at the species group and individual species level 0 and 9 yr postinitial treatment. The greatest relative increases in importance values were 1,401% and 2,995% for the red oak group and yellow-poplar (Liriodendron tulipifera), respectively, in the shelterwood and burn (SWB). Changes in all species groups were predominantly influenced by the smallest size-class (< 0.6 m tall), with the exception of northern red oak (Q. rubra) and yellow-poplar in the SWB. The SWB significantly reduced importance values of all shade-tolerant species groups and was the only treatment to decrease red maple (Acer rubrum) importance value and density over the study duration. The prescribed fire (RXF) treatment increased the red oak group importance value, while simultaneously decreasing yellow-poplar's importance value and increasing red maple's importance value. Changes in the red oak group in the SWB and the RXF were driven by northern red oak. Treatments did not significantly change the importance value of the white oak group. The SWB was the only treatment to significantly decrease overstory BA. The RXF and SWB treatments improved the competitive status of only some oak species, but modifications to these treatments might result in better control of yellow-poplar and red maple competition, further improving oak's competitive status. Although the SWB resulted in modest recruitment of northern red oak saplings, all treatments appear in need of additional follow-up vegetation control to further improve the competitiveness and recruitment of oak into large size-classes.

Does the genetic diversity among pubescent white oaks in southern Italy, Sicily and Sardinia islands support the current taxonomic classification?

Molecular diversity analysis of deciduous pubescent oaks was conducted for populations from Calabria, Sicily and Sardinia. The aims of this study were twofold. First, to provide data on the genetic diversity of pubescent oaks from an understudied area which currently exhibits one of the highest concentrations of pubescent oak species in Europe. Second, to verify if these groups of oaks are genetically distinct and if their identification is in accordance with the current taxonomic classification. Molecular analyses of leaf material of 480 trees from seventeen populations belonging to putatively different pubescent oak species (Quercus amplifolia, Q. congesta, Q. dalechampii, Q. ichnusae, Q. leptobalanos, Q. virgiliana) were performed. Twelve gene-based Expressed Sequence Tag-Simple Sequence Repeat markers were selected, and genetic diversity and differentiation were calculated. The results showed relatively high values of allelic richness, heterozygosity and number of private alleles for the populations investigated. A weak but positive correlation between geographical and genetic distance was detected. Genetic assignment (STRUCTURE) and principle coordinate analyses exhibited a weak separation into two genetic groups which, however, did not correspond to the taxonomic, chorological and ecological features of the populations investigated. Sardinian populations formed one group which was separated from the Calabrian and Sicilian populations. In light of the results obtained, the taxonomic classification for the pubescent white oaks currently reported in the major Italian floras and checklists for the study area was not confirmed by molecular analyses.

Healing effect of Quercus persica and Lawsonia inermis ointment on episiotomy wounds in primiparous women

Background:Episiotomy is one of the most common surgical interventions performed to facilitate delivery. Anti-inflammatory and antibacterial effects of Persian oak (Quercus persica) and henna (Lawsonia inermis) have been proved in previous studies. The aim of this study is to evaluate the effect of Q. persica and L. inermis ointment on episiotomy wound healing in primiparous women and comparing it with placebo group.Materials and Methods:This was a double-blind clinical trial conducted on 160 primiparous women who underwent episiotomy. The cases were randomly selected and divided into four groups of forty patients including control, placebo, those who consume topical henna, and those who consume topical Persian oak ointment. Pain and recovery assessment was done at baseline and 7th, 10th, and 14th days after birth and measured by Redness, Edema, Ecchymosis, Discharge, and Approximation (REEDA scale) and patients’ pain intensity was also measured by a visual analog scale (VAS). The collected data were analyzed using Chi-square test, one-way ANOVA, and repeated measures ANOVA test by SPSS (version 22).Results:The results revealed that according to the reduced score of REEDA till the 14th day after the delivery, the wound healing in the henna group and the oak group (−2.58 ± 0.29 and − 2.04 ± 0.31, respectively) was higher than the control and placebo groups (−1.62 ± 0.34 and − 1.95 ± 0.32, respectively) (P < 0.05). Furthermore, on the 14th day, the mean VAS score was not significantly different between henna and oak groups (henna group: 2.58 ± 0.25 and oak group: 2.23 ± 0.18); however, both intervention groups had a significant difference with the placebo and control groups (P < 0.05).Conclusion:The findings showed that the use of henna and oak ointment improves episiotomy wound healing process, so it is recommended for primiparous women.

EVALUATION OF MEDICINAL PLANTS (ASTRAGALUS ERIOCEPHALUS AND QUERCUS INFECTORIA) AS FEED ADDITIVES IN AWASSI EWES’ RATION 2. SOME BLOOD BIOCHEMICAL, HORMOAL LEVELS AND MILK HYIGEN.

The aim of this study was to investigate the effect of addition two medical plants or their mixture on hematological, biochemical parameters, hormonal levels and milk microbiology of lactating Awassi ewes. Twenty-eight ewes at mid lactation were divided into four groups and fed rations containing 1% Gall oak, 2% Astragalus, 0.5 Gall oak + 1% Astragalus, and Control. At biweekly intervals, blood samples were withdrawn. A bulk milk samples was collected for microbiological test under sterilized conditions. Results revealed that medicinal plants significantly influenced Erythrocyte Sedimentation Rate being lowest in the Astragalus group. Ewes feed Mixture group had significantly higher blood glucose concentration. Cholesterol level was significantly lower in the blood of ewes fed Gall oak diet and was highest in ewes fed Astragalus diet. Animals fed diet supplemented with Gall oak had a significantly higher concentration of T3 hormone. Total viable bacterial and mold count was decreased in the milk of Astragalus and Gall oak group, respectively. It can be concluded that Astragalus eriocephalus and Quercus infectoria improved immunity, metabolism and milk hygiene of lactating Awassi ewes.

Effects of oak wilt (Bretziella fagacearum) on post harvest Quercus regeneration

Oak wilt is a serious disease affecting oaks, especially those in the red oak group. Despite concern around a lack of oak regeneration and increasing mortality from oak wilt, there has been little effort to connect the two in relation to common forest management practices to regenerate oak. Oak management commonly includes clearcut harvesting, particularly within lower quality sites where sprouting is a viable regeneration method, but also where oak wilt is most problematic. We found that clearcut harvesting that encompassed pockets of oak wilt infected trees did not facilitate expansion or long-term perpetuation of oak wilt, but rather could serve as a containment mechanism for oak wilt. We found that stumps around 30 cm produced the greatest number of sprouts and that relatively minor differences in stump size determined if a stump was initially viable or never produced sprouts. Strong effects of stump size, and sprouting ability, remained significant drivers of survival (and mortality) over an extended 10-year period. Forest practices for oak on poor sites, such as those we studied, tend to be managed on short rotations which is likely well suited to capturing the maximum sprouting ability and long-term survival of oaks to regenerate stands.

Pollen morphology of Quercus sect. Ilex and its relevance for fossil pollen identification in southwest China

Pollen grains of 16 modern species of Quercus were examined by scanning electron microscopy (SEM) and light microscopy (LM). The focus of this investigation was on a small group (c. eight species) of alpine, sclerophyllous oaks that may form a monophyletic group within sect. Ilex. The data were combined with published data for Polar axis (P) and Equatorial diameter (E) for more than 80 species. Based on pollen morphology Quercus pollen grains were divided into three types: (1) The Cyclobalanopsis type is smallest (generally < 23 μm) in size, with P/E ratios of approximately 1.08 and a psilate or fine-grained surface; (2) Quercus sect. Ilex type is 23–29 μm, the P/E ratio is approximately 1.24 (prolate) and it has a rugulate pollen surface; (3) the Quercus sect. Quercus type is generally > 29 μm in size, has a P/E ratio of approximately 1.04, and a clearly verrucate pollen surface. Based on a comparison with modern pollen size and ornamentation, fossil pollen grains of the Quaternary Qinghai Lake core can be assigned to the Chinese southwest mountain oak group of Quercus sect. Ilex (in particular Quercus semecarpifolia). In addition, we show that the pollen percentages of Quercus rapidly increased to the highest level during the glacial period. Using SEM for the identification of fossil Quercus pollen grains is essential to ensure the accuracy of differentiating evergreen Quercus types (sect. Ilex versus sect. Cyclobalanopsis) during the last glacial period in southwest China.

Growth, survival and sunfleck response of underplanted red oaks (Quercus spp., section Erythrobalanus) along a topographic gradient in southern New England

An understanding of the regeneration niche is critical to our ability to refine silvicultural approaches aimed at regenerating and maintaining diverse, mixed species stands. However, few studies have directly tested differences in habitat associations among closely related trees of the same genus, particularly to assess habitat partitioning at the regeneration stage. To evaluate differences in regeneration niche, we established a common garden experiment with five red oak species (Quercus spp., section Erythrobalanus) under-planted across a topographic gradient (valley, midslope and ridge positions) in mixed hardwood forests of Southern New England. Represented were three red oak species common to intermediate site conditions of southern New England (Q. rubra L, Q. velutina Lam., and Q. coccinea Münchh.), and two species commonly associated with more extreme site conditions - Q. ilicifolia Wangenh. (xeric, skeletal ridge tops) and Q. palustris Münchh. (river floodplains). Seedlings were caged to prevent deer browse, and seedling height and survival were measured annually for nine growing seasons. Response to sunflecks, a primary source of light for advance regeneration-dependent species that establish in the forest understory, was measured using a LiCor 6400 photosynthesis system. Overall, survival was highest for Q. rubra, followed by Q. velutina, Q. coccinea, Q. ilicifolia and finally Q. palustris. The pattern among species held for all topographic positions, with higher survival rates on the ridgetops, and lower survival in valley positions. Height development was highest in the valley, intermediate in the ridge, and lowest in the midslope positions. Survival patterns were positively correlated with light availability, and negatively correlated with site fertility. Based on net photosynthetic rates, Q. rubra, Q. velutina, and Q. coccinea were more responsive to sunflecks than Q. ilicifolia and Q. palustris, and maintained higher photosynthetic rates over the measurement period. Greater survival of all species in upper topographic position reflects in part adaptations of the red oak group in this region to higher light and lower soil fertility conditions. But sunflecks likely play a critical role as well, judging from the positive correlation of survival with understory light (43–80% of which occurs as sunflecks), the strong height development in the light-limited valleys (where sunflecks should be most critical), and the clear alignment of species sunfleck response with species survival patterns. Differences among the oaks in photosynthetic response to sunflecks may thus help explain their habitat associations and contribute to niche partitioning among these related species. These findings have important silvicultural implications, particularly for enrichment planting of different red oaks and the timing of overstory removal treatments to facilitate establishment of regeneration for growth into the canopy.

Acorn weight as determinant of germination in red and white oaks: evidences from a common-garden greenhouse experiment

In Mexican oaks, germination increases with acorn fresh weight across oak species. Within species, these relationships are stronger in red oaks than in white oaks. In both oak groups, fresh weight of acorns increases with their dry biomass. Mexican oaks are phylogenetically grouped in red and white oaks. White oaks produce heavier acorns than red ones, but no studies have assessed whether this leads to different germination patterns. This study was aimed to determine the influence of the fresh weight of acorns on their germination. Acorns of red and white oaks were hydrated, weighed, and sowed under greenhouse conditions to assess whether their fresh weight was related with germination. We also assessed whether fresh weight of acorns was related with their dry biomass and/or water accumulation capability. Hydrated acorns of white oaks were heavier and germinated faster than those of red oaks. Germination percentages increased with acorn fresh weight across oak species. Within species, germination probability increased with acorn fresh weight, but these relationships were more marked in red oaks. Germination speed decreased with acorn fresh weight in red oaks, but these relationships were not found in white oaks. Fresh weight was positively related with acorn dry biomass in all oak species, but it was not related with water content. Increasing acorn fresh weight enhances germination across oak species. Within species, however, this trait seems to have more influence in red than in white oaks.

ŠUMSKA VEGETACIJA TREŠNJIKA KOD BANJE LUKE

Rad obrađuje šumsku vegetaciju potencijalnog Natura 2000 područja „Trešnjik” na Starčevici kodBanje Luke. Iako područje leži nadomak glavnog grada Republike Srpske, šumska vegetacija do sadanije bila istraživana. Istraživanje je ukazalo na veliki diverzitet šumskih staništa na relativno malomprostoru. Utvrđeno je ukupno sedam stanišnih tipova, klasifikovanih u dvije ekološki i florističkijasno definisane grupe: (i) Grupa stanišnih tipova bukovih šuma: (1) stanišni tip Athyrium filix-femina-Fagus sylvatica (čiste šume bukve); (2) stanišni tip Fagus sylvatica-Tilia tomentosa (šume bukvei srebrnolisne lipe); (3) stanišni tip Quercus petraea-Tilia tomentosa (degradacija prethodnog tipa,sa dominacijom lipe); (ii) Grupa stanišnih tipova kitnjakovih šuma: (4) stanišni tip Carpinus betulus-Quercus petraea (klimatogena šuma kitnjaka i graba); (5) stanišni tip Vaccinium myrtillus-Quercuspetraea (acidofilna kitnjakova šuma); (6) stanišni tip Carpinus orientalis-Quercus petraea (termofilnekitnjakove šume); (7) stanišni tip Fraxinus ornus-Carpinus orientalis (šikare bjelograbića i crnogjasena).

How can prescribed burning and harvesting restore shortleaf pine-oak woodland at the landscape scale in central United States? Modeling joint effects of harvest and fire regimes

Abstract Historical fire regimes in the central United States maintained open-canopy shortleaf pine-oak woodlands on xeric sites. Following large-scale harvest and fire suppression, those woodlands grew denser with more continuous canopy cover, and they gained mesic species at the expense of shortleaf pine. There is high interest in restoring shortleaf pine-oak woodlands; most have been converted to other forest types but those that remain are valued for high stand-scale and landscape-scale diversity. Prior stand-scale studies suggest that prescribed burning and harvesting could be effective for restoring pine-oak woodlands. However, previous short-term, stand-scale studies provided little insight into long-term, landscape-scale outcomes. To estimate outcomes of alternative restoration treatments on future species composition and forest structure, we employed an integrated field and modeling approach to simulate effects of prescribed burning and harvesting on the restoration of shortleaf pine-oak woodland composition and structure in the Mark Twain National Forest for a 100-year period. Six scenarios were modeled: no management, burn only, harvest only, and a combination of harvest with burns treatments followed by fire-free intervals of differing starting times or durations to facilitate regeneration recruitment. Both no management and prescribed burn only scenarios cannot restore current forest to historical woodland condition (i.e., 40–80% percent canopy cover or less than 55% stocking); however, scenarios including harvest can restore current forest to woodland condition in late 2020s. Under a no management scenario, total basal area would increase to a maximum around 31 m 2 ha −1 , and white oak group remained the most dominant species group throughout the simulation. Under the burn only treatment, total basal area was not reduced substantially as compared to that under no management scenario, however, there were small increases in the basal area and density of shortleaf pine. All of the treatments that included a combination of burning and harvesting reduced total basal area, which fluctuated around 13 m 2 ha −1 throughout the simulation than those under no management and prescribed only scenarios. The simulations suggested that shortleaf pine would become the most dominant group, followed by white, red oak groups, and other species with combined prescribed burning and harvesting. When coupled with harvest, the prescribed burning regime affected species composition: increasing the number of burns increased the basal area and density of shortleaf pine and decreased the basal area and density of white oak group species.

Mortality, scarring, and growth in an oak woodland following prescribed fire and commercial thinning in the Ozark Highlands

Oak-dominated (Quercus Spp.) woodlands are commonly thinned and burned in the Ozark Highlands to prevent canopy closure and regenerate desired species, despite a lack of information regarding tree mortality, scarring, and growth in residual stands. Our study compared stand- and tree-level responses after two prescribed burns across four treatments: control, burn, thin, and thin+burn. Results showed that two prescribed fires led to 19% greater cumulative mortality than in unburned stands. In the burn treatment, 19.3% of residual live overstory trees were scarred, compared to 32.4% of trees in the thin+burn treatment. Analysis of scar area revealed that thinning before burning significantly increased the surface area (cm2) of fire scars. In general, trees in the red oak group (Erythrobalanus spp.) had the greatest percentage of scarred trees, followed by the white oak group (Leucobalanus spp.), hickories (Carya spp.), and shortleaf pines (Pinus echinata Mill.). Our data indicate that two fires did not significantly decrease the radial growth of white oaks, except in stands which were thinned prior to prescribed burns. Average percent change in ring-widths (mm) suggest a 1.9% growth decrease in control, 1.4% decrease in burn, 84% increase in thin, and a 35% increase in thin+burn. Covariates such as age, slope, surrounding basal area, canopy openness, and fire scars were analyzed, but tree diameter was the only significant predictor of growth response. Overall, results suggest that effects of prescribed burning are more pronounced in thinned stands as a function of increased fuel loads and fire intensity, causing greater mortality, fire scarring, and reductions in potential growth than fire or thinning alone. This study highlights important tradeoffs between prescribed fire and thinning in oak dominated ecosystems, especially where fire related damages are in potential conflict with other stand objectives.

Coexistence trend contingent to Mediterranean oaks with different leaf habits.

In a previous work we developed a mathematical model to explain the co‐occurrence of evergreen and deciduous oak groups in the Mediterranean region, regarded as one of the distinctive features of Mediterranean biodiversity. The mathematical analysis showed that a stabilizing mechanism resulting from niche difference (i.e. different water use and water stress tolerance) between groups allows their coexistence at intermediate values of suitable soil water content. A simple formal derivation of the model expresses this hypothesis in a testable form linked uniquely to the actual evapotranspiration of forests community. In the present work we ascertain whether this simplified conclusion possesses some degree of explanatory power by comparing available data on oaks distributions and remotely sensed evapotranspiration (MODIS product) in a large‐scale survey embracing the western Mediterranean area. Our findings confirmed the basic assumptions of model addressed on large scale, but also revealed asymmetric responses to water use and water stress tolerance between evergreen and deciduous oaks that should be taken into account to increase the understating of species interactions and, ultimately, improve the modeling capacity to explain co‐occurrence.