Oak Forests Research Articles

Reconstructing the oaks’ growth patterns in Greece with the use of historical timber: Case studies from Western Peloponnese

Southern Greece is a region where available oak reference chronologies are still missing, making dendroarchaeology and dating of historical buildings rather challenging, if not impossible. In the current study we performed wood identification and dendroarchaeological analysis on timber from three historical buildings: the castles of Androusa and Koroni and the Church of Agios Dimitrios, in Western Peloponnese. The three monuments represent buildings of different uses covering different periods, but also sharing a common characteristic: oak was the only timber used in their construction, while the number of preserved timber elements is very limited. A dendroarchaeological examination of these three historical buildings, together with radiocarbon and wiggle-matching analysis, provided valuable chronological information for the local archaeologists, historians, and other scientists. Application of dendrochronological techniques has helped place the three buildings under study into the Ottoman period. Our results also show that timber was acquired most probably from local non-managed forests, which suggests that oak forests were present in the broader area at least from the late 15th to the first half of the 18th centuries. The discordance between dendrochronological and radiocarbon dates in one of the three cases highlights the need for further exploration of the study area through a combined implementation of both dendrochronological and radiocarbon dating analyses in order to develop well-replicated local oak chronologies. Our study also shows that dendroarchaeology can contribute significantly to the cultural and landscape history of Western Peloponnese even with an examination of limited number of preserved timber elements from historical buildings.

Stand structural diversity and elevation rather than functional diversity drive aboveground biomass in historically disturbed semiarid oak forests

Forests provide biodiversity reservoirs and multiples ecosystem services such as global aboveground biomass dynamics and stock. Ecosystem functions varied according to biotic and abiotic factors, however, the effects of abiotic factors (e.g. elevation) on this relationship was rarely investigated, especially in areas impacted by human activities. We explored the relationships between aboveground biomass (AGB), a key proxy of ecosystem functioning, and plant species diversity in semiarid forests of western Iran submitted to a long history of past disturbances. Forty forest patches were sampled according to an elevation gradient (1700–2100 m) and to two types of forest cover: open cover indicating an intense past use or closed cover for more preserved forests. For each patch, the composition of woody species was recorded and woody species diversity indices (richness, Simpson, Shannon and Evenness) were calculated. We also estimated AGB and computed a wide set of community-weighted mean or functional divergence of ecological traits for woody species. We found that AGB sharply decreased with elevation (from 105.68 ± 10.29 ton/ha at 1700 m to 36.18 ± 6.43ton/ha at 2100 m) for the closed cover but variations were much less pronounced for the open cover (16.32 ± 2.97 ton/ha to 30.83 ± 1.96 ton/ha, respectively). Diversity indices (richness, Simpson, Shannon) increased with elevation for the closed cover and the other traits exhibited strong variations with elevation (either positive or negative) whereas no clear trend was visible in the open cover. Similar results were found when computing the linear relationships between AGB and the different diversity indices which were highly significant in the closed cover only. Surprisingly, the relationships were negative between AGB and most diversity indices (e.g., richness, Shannon, Simpson, Evenness). The dominant Persian oak was in fact the main contributor to AGB which was reduced in stands with a higher tree mixture, a result in line with the mass ratio hypothesis. Our results also illustrate the long-lasting effects of past conservation management on the forest cover and in shaping the relationships between forest ecosystem functions (AGB production) and biodiversity in semiarid areas.

Microbial community assembly and its influencing factors of secondary forests in Qinling Mountains

Forest soil microbial community is easily modified by changes in plant composition. Therefore, differences in the assembly of soil microbial community within different forest types should be evaluated to gain a deeper understanding of microbial biodiversity and forest system functioning. In the present study, pine, oak, and pine-oak mixed forests at different developmental stages (young, immature, and mature forests) were evaluated to explore the assembly, co-occurrence network, and influencing factors of bacterial and fungal community. The assembly of bacterial community was dominated by deterministic processes (homogeneous selection), whereas the assembly of fungal community was dominated by stochastic processes (dispersion limited). At the young forest stage, the proportion of deterministic processes in bacterial community assembly among the three forest types differed less. In contrast, the proportion of deterministic processes at the immature and mature forest stages in the bacterial community assembly in the pine-oak mixed forest was larger than that in the pure forests. The proportion of stochastic processes in the assembly of fungal community in the pine-oak mixed forest was greater than that in the pure forests and was observed at all forest stages. Network analysis showed that the links and average degree of bacteria in the pine-oak mixed forest were lower than that of the pure forests, whereas the network topological features of fungi in the pine-oak mixed forest were higher than that of the pure forests. The stochastic processes increased microbial co-occurrence. The results of the random forest indicated that Pielou's evenness index (E) of plant was the most important predictor of fungal community assembly, and Shannon's diversity index (H) of plant also was the critical factor influencing bacterial community assembly. Our study demonstrated the importance of plant diversity in the assembly of forest soil microbial community.

On epigeic spider assemblages (Arachnida: Aranei) of oak forests in the Leopard Land National Park and the Kedrovaya Pad’ Reserve, Maritime Territory, the Russian Far East

On epigeic spider assemblages (Arachnida: Aranei) of oak forests in the Leopard Land National Park and the Kedrovaya Pad’ Reserve, Maritime Territory, the Russian Far East

Snow damage in a Himalayan forest maintains the dominance of evergreen oaks

AbstractExtreme climate events are increasing due to climate change. Heavy snowfall in a Himalayan evergreen oak forest damaged 21% trees and created large treefall gaps. Such occasional events may help define the upper altitudinal boundary of certain species. Oak trees with branches lopped by local communities showed lower damage.

Vertical temperature and air humidity gradients in beech and oak forests, and the forest interior climate created by beech

Forests dominated by European beech are characterized by a humid and relatively cool forest interior climate with low light intensities on the forest floor, which harbors an adapted herb layer vegetation. With the aim to quantify the air temperature and humidity (RH) conditions in the beech forest interior in direct comparison to the conditions in thermophilic oak forests at the drought-induced range limit of beech, we conducted air temperature and RH measurements in mid-summer at three height levels (7 m, 2 m, and 0.5 m above ground) in 12 forest stands in the natural beech-oak ecotone in Western Romania. On cloudless mid-summer days, the shade canopy layer of the oak forests (7 m) was at noon usually up to 3 °C warmer than the beech shade canopy; the daily maxima differed even by up to 6 °C (extremes: 32.1 °C and 27.5 °C in the beech and oak shade canopies, respectively). RH reached by about 4 percentage points lower values in the shade canopy of the oak forests than in the beech forests; the RH minima differed by up to 9 percentage points (28.2 vs. 37.4%). Vapor pressure deficit (VPD) was between noon and midnight by 2–6 hPa higher in the oak than in the beech shade canopy; even more differed the VPD maxima (38.7 vs. 22.6 hPa). We conclude that closed beech forest canopies have a considerable microclimatic buffering capacity that can reduce the severity of climate warming impacts on the vitality of the herb layer and the beech shade crown.

Small-fragment, high turnover: soil microenvironment fluctuation effect on tree diversity in a Neotropical montane oak forest.

Soil microenvironmental variables showed an important key in α and β-tree diversity in Neotropical montane oak forest. Thus, understanding the microenvironment fluctuation at small-fragment effects on tree diversity is crucial in maintaining the montane oak ecosystems. In this study, we hypothesized that within a relatively small-fragment (151.63 ha), tree α and β-diversity fluctuate and specific soil microenvironmental factors could influence tree species diversity to answer three questions: Do tree α and β-diversity differ among transects, even in a short-distance between them? Do microenvironmental variables influence tree diversity composition that occurs within a relict Neotropical montane oak forest? Is there a particular microenvironmental variable influencing tree species-specific? We established four permanent transects during a year in a relict Neotropical montane oak forest, we assessed tree diversity and specific microenvironmental variables (soil moisture, soil temperature, pH, depth litterfall and light incidence). This allowed us to evaluate how microenvironmental variables at small-fragment influence α and β-tree diversity and tree species-specific. Our results showed that α-diversity was not different among transects; however, β-diversity of tree species was mostly explained by turnover and soil moisture, soil temperature, and light incidence were the microenvironmental variables that triggered the replacement (i.e., one species by another). Those variables also had effect on tree species-specific: Mexican beech (Fagus mexicana), Quebracho (Quercus delgadoana), Pezma (Cyathea fulva), Aguacatillo (Beilschmiedia mexicana), Pezma (Dicksonia sellowiana var. arachneosa), and Mountain magnolia (Magnolia schiedeana). Our results confirm our hypothesis related to β-diversity but not with α-diversity; however, the tree community structure of the diversity was similar among transects. Our study represents the first effort to evaluate and link the soil microenvironmental effect on tree α and β-diversity, finding a high replacement in a small-fragment of Neotropical montane oak forest from eastern Mexico.

Close-to-Nature Silviculture to Maintain a Relict Population of White Oak on Etna Volcano (Sicily, Italy): Preliminary Results of a Peculiar Case Study.

Habitat loss is a potential long-term effect of projected climate change for Mediterranean forest ecosystems. Here, we investigated the effectiveness of a close-to-nature silvicultural practice to conserve an old-growth white oak forest patch in Sicily (Italy) and promote regeneration dynamics. The study area, although small, is distinctive for its isolation, position and environmental characteristics. We conducted a Before-After Control-Impact (BACI) study to analyse the responses of different taxonomic groups (vascular plants and birds) to silvicultural treatments (selection thinning, no thinning), and to determine whether close-to-nature silviculture practices may cause significant shifts in the investigated communities. Specifically, we assessed the responses of (1) vascular plants by means of species diversity and taxonomic distinctness indices and (2) birds in terms of diversity, abundance and forest specialisation. Preliminary results suggest that cautious close-to-nature silviculture practice could-by mimicking natural gap dynamics-contribute to maintaining old-growth forest patches and promote oak seedling emergence without short-term detrimental impacts on biodiversity. Although the monitoring has to be repeated over the long-term, the multi-taxon approach and indices incorporating information on taxonomic relationships into diversity measures were demonstrated to be valuable tools for interpreting biotic community structure and dynamics.

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.

TBE in Tunisia

Ixodes ricinus is principally located in oak forests, in humid to semi-humid microclimatic zones in Northwestern Tunisia. While I. ricinus is considered the main vector of tick-borne encephalitis virus (TBEV) in Europe, no reports concerning this arbovirus have been reported from North African countries. To date no human cases of tick-borne encephalitis (TBE) have been reported in Tunisia.

A Contingent Valuation-Based Method to Valuate Ecosystem Services for a Proactive Planning and Management of Cork Oak Forests in Sardinia (Italy)

The paper develops a model through a contingent valuation approach to support public authorities in the exploration and assessment of ecosystem services (ESs) generated by forest and woodlands (FOWLs). This approach is employed to the cork oak forests of the Sardinia region (Italy) due to their ability in the provision and regulation of cultural and recreational values to society. The paper describes the economic valuation of cultural ESs through the contingent valuation method (CVM) with the purpose to explore residents and tourists’ willingness to pay (WTP) preferences towards conservation, valorisation, and the management of Goceano’s cork oak forests in Sardinia. The approach may help retain suitable support for DMs, planners, technicians, and operators for a better understanding of the ESs’ role in policy decisions, leading FOWLs towards a learning process between the environment, human beings, and landscape to promote and develop a proactive landscape and forest planning and management within the region.

The Habitat Network for Butterfly Communities of the Alta Murgia National Park (Apulia, Italy)

Habitat networks can help to make habitats more resilient and assist species survival in a fragmented landscape and changing climate. Butterflies are one of the main indicators of diversity due to their high sensitivity to environmental changes. In the context of sudden and unpredictable environmental changes, protection strategies for butterflies at risk of extinction should consider the exact distribution of these species, as well as the various threats to which each of them is subjected. About 290 species of butterflies are reported in Italian fauna, and 120 of them are recorded in Apulia (Southern Italy). In the Alta Murgia National Park (AMNP) (Apulia Region, Italy), screening was performed to study the relationships between area/landscape composition and diurnal butterfly community structure. Representative semi-natural habitats of Alta Murgia buffering productive crops were selected to set up transects/paths along dry grasslands, oak forests and pine forests. Monthly samplings were performed for one year. During the survey, 909 specimens from 53 species were collected. The highest values of butterfly’s abundance and richness were recorded in dry grasslands. A strong positive correlation between butterfly abundance and air temperature was registered (Pearson correlation: r = 0.8; p < 0.001). Melanargia arge, endemic in central-southern Italy and considered threatened in Europe (Annexes II and IV—Habitats Directive), was registered in each habitat. The biodiversity indices (Chao 1, Shannon and Simpson) for each habitat were high and similar to those in protected areas of Sicily. The connected landscape is important for generalist or open-habitat specialists, and large remnants are key for disturbance-sensitive and threatened taxa. The presented evidence can provide useful information on butterfly conservation in the AMNP and for the management and conservation of characteristic landscapes of Alta Murgia.

Outcomes of a comparison between pastoral and silvopastoral management on beef cattle productivity, animal welfare and pasture depletion in a Mediterranean extensive farm

In spring 2021, 50 growing steers and heifers of the Maremmana breed (average age 321 d and weight 287 kg) were rotationally stocked under two different treatments (silvopastoral and pastoral). The aim was to evaluate the influence of grazing system on cattle growth and welfare, and pasture depletion. The experiment was carried out on a real Mediterranean agrosilvopastoral farm, located in central Italy. To implement rotational grazing, 3.69 ha of temporary grassland were split into six paddocks, three for each treatment. Cattle grazed for one week in one paddock and then were moved to the next one for a total of six weeks corresponding to six grazing periods. The group maintained on the silvopastoral system were allowed to access 3.31 ha of a Turkey oak (Quercus cerris L.) forest. Regarding the average daily gain, a significant interaction was found between the treatment and time. The average daily gain of the animals grazing in the open pasture was 1.20 kg d−1, while that of the cattle grazing in the silvopastoral system was 1.02 kg d−1. Despite the rate of growth being within the expected range for the Maremmana breed, the average daily gain of cattle in the silvopastoral system was significantly lower. One of the possible causes of this difference could be the higher energy requirements of the animals due to the different activity levels. The different management did not affect animal welfare indicators. Indeed, the serum cortisol concentration did not vary between treatments and among sampling times, while the hair cortisol concentration decreased significantly during the experiment for both groups. Regarding pasture health, allowing cattle to graze in the forest reduced pasture depletion because of the lower stocking rate and grazing pressure. Further studies are necessary to increase the knowledge of the role of forests and grazing management in other seasons than spring in extensive agrosilvopastoral systems.

A Metabolome Analysis and the Immunity of Phlomis purpurea against Phytophthora cinnamomi.

Phlomis purpurea grows spontaneously in the southern Iberian Peninsula, namely in cork oak (Quercus suber) forests. In a previous transcriptome analysis, we reported on its immunity against Phytophthora cinnamomi. However, little is known about the involvement of secondary metabolites in the P. purpurea defense response. It is known, though, that root exudates are toxic to this pathogen. To understand the involvement of secondary metabolites in the defense of P. purpurea, a metabolome analysis was performed using the leaves and roots of plants challenged with the pathogen for over 72 h. The putatively identified compounds were constitutively produced. Alkaloids, fatty acids, flavonoids, glucosinolates, polyketides, prenol lipids, phenylpropanoids, sterols, and terpenoids were differentially produced in these leaves and roots along the experiment timescale. It must be emphasized that the constitutive production of taurine in leaves and its increase soon after challenging suggests its role in P. purpurea immunity against the stress imposed by the oomycete. The rapid increase in secondary metabolite production by this plant species accounts for a concerted action of multiple compounds and genes on the innate protection of Phlomis purpurea against Phytophthora cinnamomi. The combination of the metabolome with the transcriptome data previously disclosed confirms the mentioned innate immunity of this plant against a devastating pathogen. It suggests its potential as an antagonist in phytopathogens' biological control. Its application in green forestry/agriculture is therefore possible.

Windstorm disturbance sets off plant species invasion, microbiota shift, and soilborne pathogens spread in an urban Mediterranean forest

We investigated the effects of a severe windstorm on vegetation, soil chemistry, understory microclimate, and soil microbiota in a Mediterranean holm oak forest. Plant species composition remained almost unchanged in the undisturbed area, whereas highly diverse plant communities were found in the disturbed area (e.g. gap area). Specifically, 11 invasive plant species were detected in 2015, but four years after, five disappeared and another five decreased, with only Ailanthus altissima increasing. Soil in disturbed areas has higher pH, Na, P, K, Ca, Cu, and Mn, but lower total limestone, organic carbon, total nitrogen, Mg, Fe, and standing litter compared to undisturbed areas. Disturbed areas had higher light availability at the ground and large variations in soil and air temperature and air relative humidity compared to undisturbed areas. The storm disturbance increased soil bacterial and fungal species richness and diversity. Moreover, the microbial co-occurrence network in the undisturbed area was more heterogeneous and complex, while modularity and number of positive correlations were higher in the disturbed area, which suggests that the structural composition of microbial communities and their co-occurrence patterns have been altered by windstorm disturbance. In the gaps, soil microbial community composition indicated a shift toward an opportunistic microbiota dominated by fast-growing but less competitive species. In addition, we found a large increase in putative plant pathogens but a decrease in simbiotrophic and ectomycorrhizal fungi in the gaps. The present work demonstrate the multiple effects of storm damage on the above- and belowground structure and diversity of forest ecosystems.

Fungal communities mediate but do not control leaf litter chemical transformation in a temperate oak forest

Fungal communities mediate but do not control leaf litter chemical transformation in a temperate oak forest

Long‐term hydrological and biogeochemical datasets from a Mediterranean forest site (Montseny, NE Spain)

AbstractWe present here, and make freely available, two long‐term datasets on the hydrology and hydrochemistry of two small catchments totally or partially covered by holm oak (Quercus ilex) forests. Data have been collected over four decades of research on the ecology of Mediterranean evergreen forests. The datasets contain data on water fluxes in precipitation and runoff, and on the ion concentrations and fluxes in precipitation, throughfall and streamwater. Among other applications, these data have been used to obtain catchment budgets of water and elements, to document decadal changes in atmospheric deposition and streamwater chemistry, to assess the role of Saharo‐Sahelian dust on forest nutrient cycling, and to model habitat suitability for an endangered amphibian under future climates. To encourage their further use by the scientific community, in this paper we summarize the data context and methods, and give a nutshell of obtained results. We provide the links to these datasets on the Zenodo platform.

Glebowy bank nasion zbiorowisk leśnych Wielkopolskiego Parku Narodowego – badania wstępne

The aim of this study is to examine the soil seed banks of the following plant communities: the complex of lakeside plant communities (Carici elongate-Alnetum, Fraxino-Alnetum); the Central European oak-hornbeam forest (Galio sylvatici-Carpinetum); the thermophilous oak forest (Potentillo albae-Quercetum), in the course of transformation into the oak-hornbeam forest; the fresh coniferous mixed forest (Querco roboris-Pinetum) and the subcontinental pine forest (Leucobryo-Pinetum). All of these plant communities are located in protected areas of the Wielkopolska National Park. The soil seed banks of an individual communities are compared according to the species richness and species diversity as well as species similarity between the herb-layer and the seed bank. The soil seed banks are mainly composed of autochthonous species. The studied communities differ in size and species richness of the soil seed bank as well as in its species diversity. The indicated parameters decrease along with the decrease in the fertility and humidity of the communities. A statistically significant, moderate, positive correlation of species richness between the herb layer and the soil seed bank is observed. Nevertheless, the species similarity between the herb layer and the seed bank is relatively low, which can be attributed to the following: 1) the dominance of single species is greater in soil seed banks than in herb layer; 2) woody species whose seedlings were not recorded in the herb layer or were recorded very rarely, have a large share in seed banks; 3) seeds of some clonal plants were not recorded in seed banks as these species invest only small resources in generative reproduction.

Monitoring land cover changes and droughts using statistical analysis and multi-sensor remote sensing data

Climate change is of paramount importance for ecosystems, especially in arid and semi-arid areas. The major aim of the current study is to monitor vegetation and land use changes, and run drought assessment using field and satellite data. The main precipitation proportions in the studied region are influenced by the Westerlies, meaning that any variations in these precipitation systems significantly impact the region. The utilized data entailed MODIS images for 16- and 8-day intervals between 2000 and 2013, TM and OLI sensor images recorded in 1985 and 2013, precipitation network data of TRMM satellite between 2000 and 2013, and synoptic data 32-year period. The Mann-Kendall (MK) test was used to monitor temporal changes in meteorological station data in annual and seasonal scales. The results indicated that there was a downward trend in 50% of the meteorological stations in the annual scale. This falling trend was statistically significant at the level of 95%. At the end, drought was assessed using PCI, APCI, VSWI, and NVSWI. The results showed that vegetation, forest, pasture, and agriculture areas recorded the strongest correlations with initial precipitation at the beginning of the study. Based on interactions among various factors influencing vegetation indices, reduction in green vegetation, especially the area of oak forests in the studied period, is around 95,744 hectares, which is attributed to lower precipitation rate. Increasing of agricultural land and water zones during the studied years is the result of human management and depends on how surface and underground water resources are exploited.

Analysis of cork quality and cork tree health in stands of western Spain

Good knowledge of the factors that influence cork quality and the health of forests is essential when making decisions regarding the management of productive cork oak forests. The quality of cork planks depends on: plank thickness, plank porosity and the presence of anomalies. So far, no studies have evaluated cork quality based on cork anomalies, partly due to the difficulty of obtaining adequate data. In 1985, it was developed the first Cork Quality Field Assessment Plan (CQFAP) to provide information about the quality of harvested cork by collecting data of very high quality. This work analyzes the anomalies present in 2049 cork sampling units collected from ten stands under the CQFAP for the period 1986–2012 in three consecutive cork stripping cycles. Data on diseases, pests and stripping damages are also analyzed in the 654 trees where cork sampling units were collected in the third stripping cycle. Additionally, mean monthly temperature and precipitation values for the 35 years covering the three stripping periods were calculated. A progressive deterioration of cork quality was observed in the sampled cork oak stands. It was found a positive relationship between cork thickness and temperature indicating that the cork growing period could be extended when temperatures are moderate. Sampled cork oaks were more affected by Cerambycidae attacks and Coraebus undatus indicating their prevalent nature. The presence of Coraebus undatus were higher in stands with good health status. The studied diseases were Biscogniauxia mediterranea, Phytophthora sp. and fungi of the family Botryosphaeriaceae, finding a not previously reported correlation between the presence of Crematogaster scutellaris and the three studied diseases. Stripping damages increase with smaller cork thickness but climate is not a decisive factor for a proper stripping. Although having room for improvement, the CQFAP is proving to be an effective tool for assessing the quality of cork, the health status of cork oak forests and the evolution of these forests over time. The information provided could be also used to identify places worthy of further studying. The main recommendation for improving the CQFAP would be to monitor the same trees in each consecutive sampling for properly monitoring cork thickness and the presence of defects to be used as a proxy for tree health. Regarding forest management, the main recommendations would be to extend the length of stripping cycles to enhance cork production, and to use the new tools and systems for cork stripping to reduce damage.