Mixed Oak Research Articles

White Oak (Quercus alba) Response to Thinning and Prescribed Fire in Northcentral Alabama Mixed Pine–Hardwood Forests

AbstractStrong white oak sawtimber markets, partially attributed to the stave and cooperage industries, are encouraging forest managers to re-examine silvicultural practices for white oak (Quercus alba). We examined recruitment and retention of white oak in mixed oak–pine stands on the William B. Bankhead National Forest in northcentral Alabama. Stands were subjected to three thinning levels (residual basal areas of 75 ft2/ac, 50 ft2/ac, and no thinning) and three fire frequencies (dormant season burns of none, one, three fires) in a factorial design. Both thinning treatments reduced overstory white oak tree densities, and fire had no effect on densities. For all reproduction height classes, regardless of thinning treatment, three prescribed burns increased white oak densities; thinned and burned stands had larger white oak seedling sprouts than those thinned with no burn. However, white oak reproduction height was primarily less than 2 ft tall, and seedlings larger than 4 ft tall were reduced. Thinning with one fire resulted in the highest densities of large white oak reproduction (4 ft tall up to 1.5 in. dbh). Red maple reproduction was the dominant competitor in all treatments and is positioned to dominate the reproduction cohort without additional tending treatments.

Retaining unlogged patches in Mediterranean oak forests may preserve threatened forest macrolichens

Abstract: Forest management practices may heavily impact epiphytic (tree inhabiting) organisms. Retaining tree patches and buffer strips in logged stands may contribute to preserve ecosystem functioning and the vitality of epiphytic organisms in managed forests. To test these statements, the threatened forest macrolichen Lobaria pulmonaria (L.) Hoffm. was used as a model species, since it is a “flag” indicator species of forest ecosystems with long ecological continuity. To this purpose, photosynthetic performances, thallus anatomy and water holding capacity (WHC) of samples of L. pulmonaria were investigated in a logged mixed oak forest (Tuscany, Italy), confronting lichen thalli from retained-forest patches and retained-isolated trees, 18 months after logging. Compared with those of retained-forest patches, thalli on the trunks of retained-isolated trees were thinner and showed lower vitality (as indicated by the potential quantum yield of primary photochemistry - FV/FM and the index of overall photosynthetic performance - PIABS), as well as lower water holding capacity. In contrast, thalli from forest patches had performances comparable to those of healthy samples from unlogged forests.

Tree species diversity impacts average radial growth of beech and oak trees in Belgium, not their long-term growth trend

BackgroundEnvironmental change has resulted in changes in forest growth in Europe during the last century. This has consequences for the products and services delivered by forest. Mixing tree species is often proposed as a strategy to deal with the consequences of climate change. Diversifying forests is believed to result in higher productivity and increased growth stability. Tree species diversity is therefore expected to affect long-term trends in tree radial growth. However, this has not yet been studied. In this paper we study the effect of diversity on the radial growth and its long-term trends for beech and oak trees growing along a gradient of tree species diversity in the loamy region of central Belgium (from monocultures to mixed forests patches up to three species).ResultsWe found that beech trees have a higher radial growth whereas oak trees have a lower one when growing in mixtures. The contrasting diversity-productivity relationship observed for beech and oak is in agreement with their ranking in shade tolerance, where oaks suffer increased competition in mixed oak patches. Overall, in monocultures and mixtures, an increasing radial growth trend of + 2% for the period 1927–2015 and 21% for the period 1899–2015 was found for beech and oak, respectively. Tree species diversity did not alter the shape of this detected long-term radial growth trend. Nevertheless, for oak a lower year-to-year variability in radial growth is found in mixtures indicating a higher resilience.ConclusionWe conclude that diversity impacts the average radial growth and its variability (only in the case of oak) but not the shape of the long-term trend in radial growth of beech and oak trees growing in the loamy region of central Belgium.

Climatic drivers of pinyon mouse Peromyscus truei population dynamics in a resource‐restricted environment

AbstractHighly variable patterns in temperature and rainfall events can have pronounced consequences for small mammals in resource‐restricted environments. Climatic factors can therefore play a crucial role in determining the fates of small mammal populations. We applied Pradel's temporal symmetry model to a 21‐year capture–recapture dataset to study population dynamics of the pinyon mouse (Peromyscus truei) in a semi‐arid mixed oak woodland in California, USA. We examined time‐, season‐ and sex‐specific variation in realized population growth rate (λ) and its constituent vital rates, apparent survival and recruitment. We also tested the influence of climatic factors on these rates. Overall monthly apparent survival was 0.81 ± 0.004 (estimate ± SE). Survival was generally higher during wetter months (October–May) but varied over time. Monthly recruitment rate was 0.18 ± 0.01, ranging from 0.07 ± 0.01 to 0.63 ± 0.07. Although population growth rate (λ) was highly variable, overall monthly growth rate was close to 1.0, indicating a stable population during the study period (λ ± SE = 0.99 ± 0.01). Average temperature and its variability negatively affected survival, whereas rainfall positively influenced survival and recruitment rates, and thus the population growth rate. Our results suggest that seasonal rainfall and variation in temperature at the local scale, rather than regional climatic patterns, more strongly affected vital rates in this population. Discerning such linkages between species' population dynamics and environmental variability are critical for understanding local and regional impacts of global climate change, and for gauging viability and resilience of populations in resource‐restricted environments.

Demography of evergreen and deciduous oaks in a mixed oak savanna: insights from a long‐term experiment

AbstractThe co‐existence of evergreen and deciduous oaks in Mediterranean‐climate savannas has motivated comparative studies on species’ physiological adaptations to light and drought, establishment niche differences in acorn production, dispersal and seedling herbivory, and differential sapling tolerance of ungulate browsing. Understanding how species’ differences collectively affect co‐occurrence or segregation requires long‐term studies that consider multiple life stages. We compare survival, height growth, and modeled population growth rate of the evergreen sclerophyll, Quercus agrifolia, to those of the winter‐deciduous, broadleaved Q. lobata in southern California savanna sites where the species naturally co‐occur. We evaluate species’ performances after 8.7 yr for four cohorts sown as acorns in 1997, 1998, 2000, and 2001 under four different levels of protection from cattle, deer, and rodents. Survival curves for the two species were closely similar, with large differences between cohorts associated with precipitation in the year acorns were sown. Survival and growth rates of Q. agrifolia seedlings and saplings were slightly lower, and were more reduced by ungulates and rodents, than those of Q. lobata. No Q. agrifolia plants (0/1431) exposed to ungulates (cattle and/or deer) and rodents survived to the end of the experiment. Of 1421 Q. lobata acorns planted in these treatments, only 19 plants (1.3%) survived 8.7 yr and none of these plants progressed out of the ungulate browse layer. However, when protected from both ungulates and rodents, survival rates increased significantly for both species, and Q. agrifolia increased height faster than Q. lobata. Simulated population growth rates increased slightly for plants protected from ungulates, and 95% confidence intervals spanned the stable population growth rate of 1. With exclusion of ungulates and rodents, sapling and small tree recruitment rates for both species far exceeded those needed to offset the rate of recent adult mortality, with modeled population growth rates of 1.07–1.11. Our results underscore the essential role of occasional high rainfall years for initial establishment, plus the key role of consumers in limiting early survival and growth of both evergreen and deciduous oaks in mixed oak savannas.

Характеристика дубових деревостанів у природному заповіднику "Медобори"

Встановлено, що в природному заповіднику "Медобори" насадження з участю дуба звичайного (від трьох одиниць і більше) є панівним типом деревостанів і займають 43,96 % лісових площ, переважно створені штучно за типом корінних. Проаналізовано основні таксаційні показники деревостанів дуба звичайного з поквартальних підсумків Таксаційного опису природного заповідника "Медобори". Проведено віковий аналіз досліджуваних деревостанів: частка молодняків становить 9,64 %, середньовікових – 83,13 %, пристигаючих – 0,24 %. Визначено, що деревостани з участю дуба звичайного зростають у чотирьох типах лісорослинних умов: вологій грабово-буковій діброві (11,13 %), вологій грабовій діброві (13,65 %), свіжій грабово-буковій діброві (27,85 %), свіжій грабовій діброві (48,21 %). За ярусністю дубові деревостани переважно є простими. Встановлено, що дубняки характеризуються високою продуктивністю – 89,9 % ростуть за першим і вище першого бонітетом. 68,6 % насаджень – високоповнотні, а низькоповнотних є вкрай мало. Математичному аналізу підлягали компоненти: вік, діаметр, повнота, запас деревостану. За розрахунковим значенням стандартного відхилення та коефіцієнта варіації можна стверджувати, що розмах варіації показника "повнота" характеризується середнім значенням мінливості ознаки. Інші показники мають широкий діапазон розсіювання у досліджених сукупностях.

Characterization of ozone deposition to a mixed oak–hornbeam forest – flux measurements at five levels above and inside the canopy and their interactions with nitric oxide

Abstract. A 1-month field campaign of ozone (O3) flux measurements along a five-level vertical profile above, inside and below the canopy was run in a mature broadleaf forest of the Po Valley, northern Italy. The study aimed to characterize O3 flux dynamics and their interactions with nitrogen oxides (NOx) fluxes from the forest soil and the atmosphere above the canopy. Ozone fluxes measured at the levels above the canopy were in good agreement, thus confirming the validity of the constant flux hypothesis, while below-canopy O3 fluxes were lower than above. However, at the upper canopy edge O3 fluxes were surprisingly higher than above during the morning hours. This was attributed to a chemical O3 sink due to a reaction with the nitric oxide (NO) emitted from soil and deposited from the atmosphere, thus converging at the top of the canopy. Moreover, this mechanism was favored by the morning coupling between the forest and the atmosphere, while in the afternoon the fluxes at the upper canopy edge became similar to those of the levels above as a consequence of the in-canopy stratification. Nearly 80 % of the O3 deposited to the forest ecosystem was removed by the canopy by stomatal deposition, dry deposition on physical surfaces and by ambient chemistry reactions (33.3 % by the upper canopy layer and 46.3 % by the lower canopy layer). Only a minor part of O3 was removed by the understorey vegetation and the soil surface (2 %), while the remaining 18.2 % was consumed by chemical reaction with NO emitted from soil. The collected data could be used to improve the O3 risk assessment for forests and to test the predicting capability of O3 deposition models. Moreover, these data could help multilayer canopy models to separate the influence of ambient chemistry vs. O3 dry deposition on the observed fluxes.

Micobiota de la ZEC Gándaras de Budiño (Pontevedra, N.O. Península Ibérica)

La Zona de Especial Conservación (ZEC) Gándaras de Budiño está situada en el suroeste de la provincia de Pontevedra (Galicia, Península Ibérica). A pesar de las agresiones sufridas a lo largo de la historia, aún se conservan zonas muy representativas de esta con fauna y flora propia de estos lugares y poco frecuente en el resto del N.O. peninsular. Ocupa una extensión de aproximadamente 800 ha, en las que destacan un amplio complejo de humedales, conformados por turberas, brañas, bosques aluviales y lagunas, así como brezales atlánticos, bosques de ribera y amplias extensiones más secas, constituidas básicamente por bosques mixtos de robles y pinos. En este espacio se realiza un estudio micológico con recolecciones periódicas durante 4 años, de las cuales resulta un catálogo con 359 taxa, con una aportación al catálogo gallego de 62 especies. Entre ellas destaca Chaetotyphula actinipes, que se menciona por primera vez para Europa, además de Arnium olerum, Byssosphaeria schiedermayeriana, Conocybe brachypodii, Cordyceps polyarthra, Hemimycena angustispora, Inocybe salicis, Laccaria impolita, Mollisia olivascens, Mycena atrovinosa, Mycena mucor, Oligoporus alni, Russula sphagnophila y Trichoderma piluliferum, no mencionados anteriormente para la Península Ibérica. Desde el punto de vista de la estrategia trófica destacan las especies entomapatógenas: Beauveria bassiana, Cordyceps polyarthra, Gibellula pulchra, Isaria farinosa y Torrubiella arachnophila. De las restantes 125 son micorrícicas, 211 son saprotróficas y 38 necrotróficas, en ambos casos, mayoritariamente lignícolas, justificado porque las ¾ partes del material ha sido recolectado en formaciones arbóreas de Alnus glutinosa y Salix atrocinerea. Además, se analiza la autoecología de las especies, los patrones de fructificación y su aportación corológica, tanto ibérica como mundial.

Differences in soil moisture in two Middle Eastern oak forests: Comparing the effects of trees and soil composition

The incidence of large rain events in Mediterranean ecosystems vary among years. Summer aridity is interpreted as a resetting event, eliminating previous soil‐moisture dynamics. The dynamics of soil moisture and retention are critical to tree survival, particularly in dry regions. This study examines the long‐term soil water content (θV) dynamics in two distinct locations within the forest, under the canopy and forest clearing, within two diverse oak forests: subhumid mixed oak forests (MG) and semiarid monospecific oak woodlands (YE). Plots were established at small‐scale catchments and soil water contents were measured during 2010–2013, at three depths in the two different locations. Cumulative rainfall was used as an independent proxy for θV analysis. A novel bell‐bilogistic mathematical model of wetting, saturation, and drying arms was developed. We aimed to study the θV distribution differences between soil profiles giving the large climatic gradient between the two forested sub basins, the differences in vegetation traits along with soil attributes. We further aimed at determining the role of an individual tree in regulating soil‐moisture dynamics. We hypothesized the occurrence of distinct responses between sites in all soil‐moisture indices with higher θV at the wetter site. We tested the hypothesis that seasonal cumulative rainfall dictates the variations in soil‐moisture regimes throughout contiguous years. Annual rainfall was higher than long‐term average throughout the study. Soil profiles under the canopies at both sites were consistently wetter. Infiltration and depletion constants were higher at MG whereas maximum soil moisture was higher at YE. Homogenous recharge patterns were seen at MG although YE evinced more variation. Oaks had no effect on recharge at MG compared with the forest clearing. Soil properties primarily affected the wetting arm whereas vegetation composition regulated the drying arm. Mixed‐stands characterized by ever‐green and deciduous species may maintain favourable soil‐moisture conditions, in comparison with other mixed stand morphologies. The increasing role of slacking forces in infiltration process may alter the interaction between trees and herbaceous vegetation.

How long do seeds of the invasive tree, Ailanthus altissima remain viable?

The non-native invasive tree, Ailanthus altissima is an increasing threat to the diversity and health of temperate forests. Female trees are prolific producers of wind-dispersed seeds. It is not known if Ailanthus seeds remain viable in natural growing conditions beyond two years. We collected Ailanthus seeds from eleven sources in fall 2010 and incubated outdoors in either mixed oak leaf litter or mineral soil (10 cm depth) for five years to assess seed viability. Each May sets of seeds were retrieved, counted and sown in a greenhouse to measure germination. Initially germination rates averaged 87%, however in year 5 (2016), germination rates of seeds incubated outdoors in oak leaf litter, fell to 1.9%, while those incubated in mineral soil averaged 75%. Germination rates of soil-incubated seeds ranged from 48 to 95% among the eleven seed sources after five years. These findings demonstrate that the common practice to eliminate Ailanthus seed sources two years prior to a timber harvest is insufficient to deplete its seed bank. We propose that managers remove seed sources at minimum of six years in advance of a scheduled timber harvest. Ideally, it would be most advantageous to incorporate removal of females Ailanthus as a routine management practice.

Development of Target Sequence Capture and Estimation of Genomic Relatedness in a Mixed Oak Stand.

Anticipating the evolutionary responses of long-lived organisms, such as trees, to environmental changes, requires the assessment of genetic variation of adaptive traits in natural populations. To this end, high-density markers are needed to calculate genomic relatedness between individuals allowing to estimate the genetic variance of traits in wild populations. We designed a targeted capture-based, next-generation sequencing assay based on the highly heterozygous pedunculate oak (Quercus robur) reference genome, for the sequencing of 3 Mb of genic and intergenic regions. Using a mixed stand of 293 Q. robur and Q. petraea genotypes we successfully captured over 97% of the target sequences, corresponding to 0.39% of the oak genome, with sufficient depth (97×) for the detection of about 190,000 SNPs evenly spread over the targeted regions. We validated the technique by evaluating its reproducibility, and comparing the genomic relatedness of trees with their known pedigree relationship. We explored the use of the technique on other related species and highlighted the advantages and limitations of this approach. We found that 92.07% of target sequences in Q. suber and 70.36% of sequences in Fagus sylvatica were captured. We used this SNP resource to estimate genetic relatedness in the mixed oak stand. Mean pairwise genetic relatedness was low within each species with a few values exceeding 0.25 (half-sibs) or 0.5 (full-sibs). Finally, we applied the technique to a long-standing issue in population genetics of trees regarding the relationship between inbreeding and components of fitness. We found very weak signals for inbreeding depression for reproductive success and no signal for growth within both species.

Use of Sentinel-2 for forest classification in Mediterranean environments

Spatially-explicit information on forest composition provides valuable information to fulfil scientific, ecological and management objectives and to monitor multiple changes in forest ecosystems. The recently developed Sentinel-2 (S2) satellite imagery holds great potential for improving the classification of forest types at medium-large scales due to the concurrent availability of multispectral bands with high spatial resolution and quick revisit time. In this study, we tested the ability of S2 for forest type mapping in a Mediterranean environment. Three operational S2 images covering different phenological periods (winter, spring, summer) were processed and analyzed. Ten 10 m and 20 m bands available from S2 and four vegetation indices (VIs) were used to evaluate the ability of S2 to discriminate forest categories (conifer, broadleaved and mixed forests) and four forest types (beech forests; mixed spruce-fir forests; chestnut forests; mixed oak forests). We found that a single S2 image acquired in summer cannot discriminate neither the considered forest categories nor the forest types and therefore multitemporal images collected at different phenological periods are required. The best configuration yielded an accuracy > 83% in all considered forest types. We conclude that S2 can represent an effective option for repeated forest monitoring and mapping.

Effects of the overstory on the diversity of the herb and shrub layers of Anatolian black pine forests

Understory plants are important components of forests because they are responsible for the majority of the vascular plant diversity of forest ecosystems. The richness and composition of understory communities are closely related to the tree layer diversity, structure and composition. The aim of this study was to examine the understory diversity of Anatolian black pine (Pinus nigra Arnold subsp. pallasiana (Lamb.) Holmboe)-dominated forests on the Kazdagi Mountains of West Turkey. To describe the overstory structure and composition in a numerically and quantitatively well-defined manner, cumulative abundance profiles (CAPs) of the tree species were used. The resemblance of the sampling plots was classified into five stand types assessing the CAP through the Fuzzy C-Means clustering method. A permutational multivariate analysis of variance (PERMANOVA) was performed to test the variance of the community ecological distance between the five stand types, and the results showed significant differences in these clusters. Many shade-tolerant plants were associated with the mixed stands of Anatolian black pine–Kazdagi fir. The composition of the herb and shrub layer could not be explained by the environmental variables but by differences in the overstory structure of the stands. Pure or nearly pure Anatolian Black pine stands were more diverse than mixed oak–Anatolian black pine and Kazdagi fir–Anatolian black pine stands. However, although dense and young pure Anatolian black pine stands had the most diverse plant species in the shrub layer, they were ranked third in terms of the herb layer diversity. The Anatolian black pine–Kazdagi fir mixed stands had the lowest herb and shrub layer diversity. These results allow us to comprehend the relationship between the overstory structure and composition, and the understory diversity. Understanding this relationship is important for the conservation of understory plant diversity in the management of forest ecosystems.

Fine Scale Determinants of Soil Litter Fauna on a Mediterranean Mixed Oak Forest Invaded by the Exotic Soil-Borne Pathogen Phytophthora cinnamomi

There is growing recognition of the importance of soil fauna for modulating nutrient cycling processes such as litter decomposition. However, little is known about the drivers promoting changes in soil fauna abundance on a local scale. We explored this gap of knowledge in a mixed oak forest of Southern Spain, which is under decline due to the invasion of the exotic soil-borne pathogen Phytophthora cinnamomi. Meso-invertebrate abundance found in soil litter was estimated at the suborder level. We then explored their statistical correlations with respect to light availability, tree and litter characteristics, and P. cinnamomi abundance. Oribatida and Entomobryomporpha were the most abundant groups of Acari and Collembola, respectively. According to their trophic level, predator and detritivore abundances were positively correlated while detritivores were, in turn, positively correlated with pathogen abundance and negatively influenced by light availability and tree defoliation. These overall trends differed between groups. Among detritivores, Diplopoda preferred highly decomposed litter while Oribatida and Psocoptera preferred darker environments and Poduromorpha were selected for environments with lower tree defoliation. Our results show the predominant role of light availability in influencing litter fauna abundances at local scales and suggest that the invasive soil-borne pathogen P. cinnamomi is integrated in these complex relationships.

ВПЛИВ МЕТОДУ СТВОРЕННЯ НАСАДЖЕНЬ ДУБА ЗВИЧАЙНОГО (QUERCUS ROBUR L.) НА ЇХНЮ ПРОДУКТИВНІСТЬ В УМОВАХ СВІЖОЇ ГРАБОВОЇ ДІБРОВИ ПРАВОБЕРЕЖНОГО ЛІСОСТЕПУ УКРАЇНИ

Досліджено продуктивність штучних дубових насаджень свіжих грабових дібров залежно від методу їхнього створення. За даними пробних площ у віці 10–68 років визначено основні лісівничо-таксаційні показники культур дуба звичайного (Quercus robur L.). Виявлено їхню залежність від методу створення і відмінність у продуктивності культур, які створені садінням сіянців і висівом жолудів на свіжих зрубах. Встановлено, що, починаючи з 10-річного віку, середні висоти культур дуба істотно залежать від методу створення культур. Висоти культур дуба, створеного висівом жолудів, у віці молодняка на 6–9 % більші, ніж за умови створення культур садінням сіянців. З часом ця різниця за висотами збільшується і в VІІ класі становить 11–19 %. Оцінено вплив методу створення на середні діаметри дерев дуба. Доведено, що до 40 років середній діаметр дерев дуба більший за умови створення насадження садінням, але з часом діаметри вирівнюються. Виявлено певну послідовність у збереженні чисельності дуба. За умови висівання кількість збережених дерев на 1 га в 10-річному віці на 37,5 % більша, але з часом різниця зменшується і в 68 років становить 17,3 %. Встановлено вплив методу створення на запас дерев дуба. За умови створення культур висівом, залежно від віку насадження, запас дерев дуба на 1 га збільшується в середньому до 40 %. Встановлено вплив методу створення культур на загальну продуктивність змішаних дубових деревостанів. З'ясовано, що за умови створення культур методом висіву жолудів, запаси насаджень на 1 га більші в середньому на 17 %. Культури дуба, створені висівом, мають краще очищення стовбурів від гілля і сучків, а стовбури є більш повнодеревними.

Vegetation dynamics associated with changes in atmospheric nitrogen deposition and climate in hardwood forests of Shenandoah and Great Smoky Mountains National Parks, USA

Ecological effects of atmospheric nitrogen (N) and sulfur (S) deposition on two hardwood forest sites in the eastern United States were simulated in the context of a changing climate using the dynamic coupled biogeochemical/ecological model chain ForSAFE-Veg. The sites are a mixed oak forest in Shenandoah National Park, Virginia (Piney River) and a mixed oak-sugar maple forest in Great Smoky Mountains National Park, Tennessee (Cosby Creek). The sites have received relatively high levels of both S and N deposition and the climate has warmed over the past half century or longer. The model was used to evaluate the composition of the understory plant communities, the alignment between plant species niche preferences and ambient conditions, and estimate changes in relative species abundances as reflected by plant cover under various scenarios of future atmospheric N and S deposition and climate change. The main driver of ecological effects was soil solution N concentration. Results of this research suggested that future climate change might compromise the capacity for the forests to sustain habitat suitability. However, vegetation results should be considered preliminary until further model validation can be performed. With expected future climate change, preliminary estimates suggest that sustained future N deposition above 7.4 and 5.0 kg N/ha/yr is expected to decrease contemporary habitat suitability for indicator plant species located at Piney River and Cosby Creek, respectively.

Experimental Evaluation of Several Key Factors Affecting Root Biomass Estimation by 1500 MHz Ground-Penetrating Radar

Accurate quantification of coarse roots without disturbance represents a gap in our understanding of belowground ecology. Ground penetrating radar (GPR) has shown significant promise for coarse root detection and measurement, however root orientation relative to scanning transect direction, the difficulty identifying dead root mass, and the effects of root shadowing are all key factors affecting biomass estimation that require additional research. Specifically, many aspects of GPR applicability for coarse root measurement have not been tested with a full range of antenna frequencies. We tested the effects of multiple scanning directions, root crossover, and root versus soil moisture content in a sand-hill mixed oak community using a 1500 MHz antenna, which provides higher resolution than the oft used 900 MHz antenna. Combining four scanning directions produced a significant relationship between GPR signal reflectance and coarse root biomass (R2 = 0.75) (p < 0.01) and reduced variability encountered when fewer scanning directions were used. Additionally, significantly fewer roots were correctly identified when their moisture content was allowed to equalize with the surrounding soil (p < 0.01), providing evidence to support assertions that GPR cannot reliably identify dead root mass. The 1500 MHz antenna was able to identify roots in close proximity of each other as well as roots shadowed beneath shallower roots, providing higher precision than a 900 MHz antenna. As expected, using a 1500 MHz antenna eliminates some of the deficiency in precision observed in studies that utilized lower frequency antennas.

Ecological Mapping for the Preventive Conservation of Prehistoric Mural Paintings in Rock Habitats: the Site of Filiano (Basilicata, Italy)

Biodeterioration phenomena are of great relevance in rock settlements, due to favourable environmental conditions, such as the infiltration of rainwaters, condensation phenomena and abundance of salts and organic nutrients. Rinaldi’s rock shelter in Filiano, which is located in a natural forest of mixed oaks is of great value due to the important traces of prehistoric paintings. It is an emblematic case of the delicate balance, achieved throughout the centuries, between the environment and artwork. During the plurimillenarian history of the site, a portion of the ceiling that covered the shelter collapsed, leaving signs that are still visible today, together with traces of blackening left by the fires of ancient settlements. Several of the biodeteriogens typical of rocky habitats have already been detected and include algae, cyanobacteria, mosses, lichens, vascular plants and fungi, which form macroscopic communities. Each community has an ecological preference and the mapping of their distribution is a suitable tool for understanding variations in the environmental factors that most affect them. Relating ecological data to the taxonomical characterization of the species and to the spatial distribution of each community, a site map of the humidity and of the nutrients was obtained. Among the various communities, microcolonial fungi (MCF), which appear as little black spots, here, represent the most critical risk factor, due to their low water needs. An evaluation of the biological risk for the possible future attack of such a biological community was made, suggesting indirect mitigation measures, through modification of the microclimatic and local ventilation conditions.

Fine-scale species distribution changes in a mixed oak stand over two successive generations.

Large-scale tree distribution changes have received considerable attention but underlying demo-genetic mechanisms are less well documented. We used a diachronic approach to track species shifts in a mixed oak stand (Quercus petraea-Quercusrobur) at a fine spatiotemporal scale. Species assignment was made using single nucleotide polymorphism (SNP) fingerprints employing clustering and parentage analysis. Mating patterns and reproductive success were assessed by parentage analysis. Plot-based inventories of soil parameters and sapling densities provided ecological and demographic information, respectively. Sapling density and reproductive success was higher in Q.petraea than in Q.robur, and were correlated with a spatial expansion of Q.petraea (50% to 67% of the area). Admixed trees resulting from hybridization and backcrossing between the two species were more frequent under the Q.robur canopy. We suspect that species' differential responses to ongoing environmental changes and interspecific competition are the predominant factors accounting for the recruitment success of Q.petraea, while human interference, differential reproduction and hybridization (and backcrossings) are probably of more limited importance. We anticipate in mixed Q.petraea-Q.robur stands, under current ongoing environmental change, that these processes will be enhanced, at least in the western part of the distribution of the two species.

Terrestrial and aquatic ecosystem responses to early Holocene rapid climate change (RCC) events in the South Carpathian Mountains, Romania

As demonstrated by an increasing number of palaeoclimatic and palaeoecological studies, rapid climate change events (RCCs) occurred frequently in the Holocene and their timing correlates well in the European records. Changes in vegetation composition and environmental conditions were significant during these RCC events. In this study we use high resolution pollen, stomata, micro- and macrocharcoal, macrofossil, siliceous algae, biogenic silica and organic content analyses from two alpine lake sediments (Lake Brazi, 1740 m a.s.l.; Lake Gales, 1990 m a.s.l.) in the Retezat Mts, South Carpathian Mountains, Romania. Our aim is to study ecosystem responses to RCCs between 12,000 and 7000 cal yr BP using high-resolution proxy analyses of the relevant sediment sections. We detected several significant changes in the terrestrial vegetation composition and aquatic ecosystems in case of both lakes. Complex ecosystem responses were found in connection with the early Holocene RCC intervals. Most prominently, the 10.2 ka climatic change likely fostered the extinction of Larix decidua from the shore of Lake Brazi, while climatic change during the 8.2 ka event facilitated the establishment of Carpinus betulus in the lower deciduous mixed oak forests, due to decreasing growing season temperatures, frequent summer droughts and associated recurrent fire events. Taken together, most of the significant pollen compositional changes reflected the periodic spread of pioneer deciduous tree taxa (mainly Fraxinus excelsior and Corylus avellana) during the early Holocene RCCs. In all cases, this change was connectable to increased regional fire activity and the temporary increase of herbs. The most significant change in the lake-ecosystems was often the short-lived spread of various planktonic diatom species, mainly the members of genus Aulacoseira. Sudden appearance and large-scale percentage increase of these taxa suggested higher water-depth and/or intensified water turbulence.