Major Tree Research Articles

Region-wide assessment of fine-scale associations between invasive plants and forest regeneration

Invasive plants are widely spread throughout the forests of the southern United States (US) and are expected to rapidly increase their distributional ranges over the next few decades. Multiple studies have shown that invasive plants pose great challenges to forest regeneration at local spatial scales; however, little is known about how those local-scale impacts of invasive plants may collectively influence forest regeneration at a regional scale. In this study, we hypothesized that invasive plants influence forest regeneration across southern US forests by altering tree seedling and sapling abundance and diversity. We used a total of 52,690 southern US forestland plots surveyed between 2015 and 2019 by the Forest Inventory and Analysis (FIA) program of the US Department of Agriculture Forest Service. We compiled presence/absence data from 16 major invasive plant taxa and calculated the number, richness, and diversity of seedlings and saplings for all major tree species present in the dataset. We used Generalized Linear Models to examine the relationship of the selected invasive plants to tree seedlings and saplings. We then used principal component analysis to evaluate whether negative relationships appeared to be related to niche differences. We found that the presence of invasive plants generally was negatively associated with tree seedling and sapling abundance, and that these negative interactions appeared to be independent of niche associations. Moreover, fast-growing hardwood tree species had the fewest negative species-wise associations with invasive plants, which suggests that the influence of plant invasions on forest regeneration may be partly mediated by the functional traits of regenerating tree species. We also found that the invasive plants evaluated in this study differentially influenced seedling versus sapling abundance and diversity, which could have complex implications for decision-making related to forest management strategies. Ultimately, the potential impact of these invasive plants on tree regeneration is likely to hamper the sustainable management of southern US forests (natural and managed) by the reduction of extant biodiversity. Thus, invasive plants should be incorporated into management strategies to help ensure the persistence of native forest communities and the ecological services they provide.

Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA

Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments of pollen deposition processes be quantitatively linked to spatially-explicit measures of plant abundance. Our study addressed these methodological challenges. Modern PAR and vegetation data were obtained from seven lakes in the western Klamath Mountains, California. To determine how to best calibrate our PAR-biomass model, we first calculated the spatial area of vegetation where vegetation composition and patterning is recorded by changes in the pollen signal using two metrics. These metrics were an assemblage-level relevant source area of pollen (aRSAP) derived from extended R-value analysis ( sensu Sugita, 1993) and a taxon-specific relevant source area of pollen (tRSAP) derived from PAR regression ( sensu Jackson, 1990). To the best of our knowledge, aRSAP and tRSAP have not been directly compared. We found that the tRSAP estimated a smaller area for some taxa (e.g. a circular area with a 225 m radius for Pinus) than the aRSAP (a circular area with a 625 m radius). We fit linear models to relate PAR values from modern lake sediments with empirical, distance-weighted estimates of aboveground live biomass (AGLdw) for both the aRSAP and tRSAP distances. In both cases, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and TCT (Taxodiaceae, Cupressaceae, and Taxaceae families) – were statistically significant and reasonably precise estimators of contemporary AGLdw. However, predictions weighted by the distance defined by aRSAP tended to be more precise. The relative root-mean squared error for the aRSAP biomass estimates was 9% compared to 12% for tRSAP. Our results demonstrate that calibrated PAR-biomass relationships provide a robust method to infer changes in past plant biomass.

Intra- and inter-species variations in carbon content of 14 major tree species in Northeast China

Reducing greenhouse gas emissions is one of the major challenges in combating global warming. Carbon, including in the form of carbon dioxide (CO2), is considered an essential greenhouse gas under human control to demonstrate success in emission reductions. However, many carbon stock quantifications in forest ecosystems still rely on the estimated 50% carbon content instead of more precise species-, tissue- and site-specific values. Thus, this study aimed to thoroughly measure and analyze the carbon content and variability using the 14 major tree species in Northeast China. Over 600 trees were destructively sampled from three different major mountainous regions (i.e., the Changbai, Daxing’an, and Xiaoxing’an mountains), and the carbon contents of each species were precisely measured to the sub-tissue level. Carbon contents varied significantly between species, with foliage carbon mostly found to be the highest, while root carbon contents were the lowest. Average carbon contents can be ranked as: Ulmus laciniata (43.4%) < Phellodendron amurense (43.5%) < Acer mono (43.8%) < Tilia amurensis (44.2%) < Populus davidiana (44.5%) < Fraxinus mandshurica (44.7%) < Juglans mandshurica (44.9%) < Quercus mongolica (45.3%) < Betulla davurica (45.8%) < Betulla platyphylla (46.7%) < Picea koreansis (46.9%) < Larix gmelinii (47.4%) < Pinus koreansis (48.3%) < Abies nephrolepis (48.3%). Carbon contents were higher in conifers (47.7%) compared to broadleaf species (44.9%). In addition, both tree tissues and growing sites also had a significant effect on carbon content. At the sub-tissue level, only stem’s sub-tissues (i.e., bark, heartwood, and sapwood) carbon contents showed significant variations. The results suggest that bark should be separated from other stem sub-tissues and considered separately when determining carbon stocks. This research contributes to improving estimates of terrestrial carbon quantifications, and in particular, the values obtained can be used in China’s National Forest Inventory.

兰州市南山和北山3种乔木叶片生态化学计量特征的对比研究

叶片生态化学计量是了解生物地球化学循环的窗口，也是认识植物的生长状况及生态适应性的关键，研究人工林叶片生态化学计量特征对进一步优化生态工程建设具有重要意义。为揭示兰州市南北两山主要绿化树种侧柏、圆柏和云杉环境适应性的异同，对其叶片生态化学计量特征进行了对比研究。结果显示：云杉、圆柏叶片C含量（496.02、497.64 g/kg）显著高于侧柏叶片（484.12 g/kg），侧柏叶片N、P含量（17.70、1.66 g/kg）均显著高于圆柏（14.04、1.42 g/kg）和云杉（15.62、1.40 g/kg）。C、N、P的变异系数均为圆柏 < 侧柏 < 云杉；云杉、圆柏叶片C ∶ N （33.32、35.42）、C ∶ P （389.57、360.52）显著高于侧柏叶片（28.17、306.07），云杉叶片N ∶ P （11.88）显著高于圆柏叶片（10.20）和侧柏叶片（10.98）。C ∶ N、C ∶ P、N ∶ P的变异系数均为圆柏 < 侧柏 < 云杉；侧柏和云杉叶片N含量与P含量正相关、与C ∶ N、C ∶ P负相关，而3种乔木叶片P含量与C ∶ P、N ∶ P负相关（且C ∶ P与N ∶ P正相关）。圆柏叶片C含量与N含量正相关，侧柏叶片C含量与N含量负相关但与叶片C ∶ N、C ∶ P正相关，侧柏和云杉叶片C ∶ N与C ∶ P正相关。冗余分析表明，SOC ∶ STN是影响3种乔木叶片化学计量的主导因子，圆柏叶片C、侧柏叶片P与SOC正相关，3种乔木叶片N都与SOC、SOC ∶ STN和SOC ∶ STP正相关；云杉叶片N，侧柏、云杉叶片P和STP负相关，而STP与侧柏叶片C ∶ P、N ∶ P及云杉叶片C ∶ N正相关；3种乔木叶片C ∶ N与SOC ∶ STN、SOC ∶ STP负相关。研究结果表明：面对养分贫瘠的土壤环境，3种乔木叶片生态化学计量的适应策略有所不同，其中云杉和圆柏采取防御策略，而侧柏采取竞争倾向策略。虽然云杉是兰州市较适宜的造林树种，但其生长与其他两种乔木一样，都受N元素的限制。;Foliar stoichiometry is a window to understand the biogeochemical cycle, as well as understand plant growth and ecological adaptability. Studying the foliar stoichiometry of artificial forests is of great significance for further optimizing ecological projects. In order to reveal the similarities and differences of the main greening species (Sabina chinensis, platycladus orientalis, Picea asperata) to environmental adaptability in the north and south mountains of Lanzhou City, the foliar stoichiometry traits of three trees were compared. The results showed that the foliar C contents of Picea asperata and Sabina chinensis (497.64 g/kg, and 496.02 g/kg, respectively) was significantly higher than that of platycladus orientalis (484.12 g/kg). The foliar N content of platycladus orientalis (17.70 g/kg) was significantly higher than that of Sabina chinensis and Picea asperata (14.04 g/kg,15.62 g/kg, respectively), and this trend was also found for foliar P content, with the former being 1.66 g/kg, and the latter two being 1.42 g/kg and 1.40 g/kg, respectively. The order of variation coefficients of C, N, and P were Sabina chinensis < platycladus orientalis < Picea asperata. The foliar C ∶ N and C ∶ P of Sabina chinensis (35.42 and 360.52, respectively) and Picea asperata (33.32 and 389.57, respectively) were both significantly higher than the C ∶ N (28.17) and C ∶ P (306.07) of platycladus orientalis. The foliar N ∶ P (11.88) of Picea asperata was significantly higher than that of Sabina chinensis (10.20) and platycladus orientalis (10.98). The order of variation coefficients of C ∶ N, C ∶ P, and N ∶ P were Sabina chinensis < platycladus orientalis < Picea asperata. The foliar N contents of platycladus orientalis and Picea asperata were positively related to the foliar P content, but were negatively related to the foliar C ∶ N and C ∶ P. The foliar P contents of the three trees were negatively related to the foliar C ∶ P and N ∶ P, with being positive correlation with each other. The foliar C content of Sabina chinensis was positively related to the foliar N content, yet for platycladus orientalis it was negatively related to the foliar N content, but positively related to the foliar C ∶ N and C ∶ P. The redundant analysis showed that foliar stoichiometry traits were mainly influenced by soil organic carbon (SOC): soil total nitrogen (STN), with the foliar C content of Sabina chinensis being positively correlated with SOC, SOC ∶ STN, and soil pH; the foliar N content of the three trees were all positively correlated with SOC, SOC ∶ STN, and SOC ∶ STP. The foliar N content of Picea asperata, and the foliar P content of platycladus orientalis and Picea asperata were negatively correlated with soil total phosphorus (STP), while the STP was positively correlated with the foliar C ∶ P and N ∶ P of platycladus orientalis and foliar C ∶ N of Picea asperata, respectively. The foliar C ∶ N values of the three trees were negatively correlated with SOC ∶ STN and SOC ∶ STP. The results suggest that three major trees have different adaptation strategies under poor nutrient habitat, with a defensive strategy for Sabina chinensis and Picea asperata, and a competitive strategy for platycladus orientalis. Though Picea asperata may be the most suitable species that were planted in north and south mountains of Lanzhou City, the growth of the three trees were all limited by STN.

Demystifying the age of old olive trees

Iconic to the Mediterranean landscape, the age of monumental olive trees with large trunks and unique silhouettes is often considered several centuries to millennia. Here we combine tree-ring and radiocarbon dating to show that most monumental olive trees may have maximum ages between 300 and 500 years. Our example helps disentangling the tree size-longevity conundrum in a major Mediterranean cultivated tree species and important cultural heritage.

Emissions of gaseous formic and acetic acids from major tree species in Japan

Gaseous formic and acetic acids are directly emitted from vegetation and produced by the photooxidation of biogenic volatile organic compounds in the atmosphere. Gaseous formic and acetic acid emissions from trees have not been well studied in Japan and the Asian region, and to gain further knowledge in this respect, we measured the emissions of formic and acetic acid emissions together with isoprene and monoterpene emissions from 10 major forest tree species and 10 major road tree species. All of the measured trees were found to emit gaseous formic and acetic acids from their leaves, but not all species emitted isoprene or monoterpene. The emission rates of formic (0.05–1.3 μg gDW−1 h−1) and acetic (0.10–1.43 μg gDW−1 h−1) acids were similar to those of some trees in Europe but higher than those of tropical tree species. No monthly variations were found in the emission rates of formic and acetic acids, but the emission rates of isoprene and monoterpene showed clear monthly variations. We calculated the ratio of direct emissions to direct plus secondary production derived by the photooxidation of formic and acetic acids by isoprene and monoterpene (direct/total emission ratio) relating to major forest and road tree species in Japan. For isoprene and monoterpene emitters, the average values of the direct/total emission ratio of formic and acetic acids in August were 62% (range: 9.0–88%) and 64% (range: 6.2–90%), respectively. The contribution degree of the direct/total emission ratio differed depending on the isoprene and monoterpene emission rates. The findings are suggestive of the importance of both direct emissions of gaseous formic and acetic acids from trees and the secondary formation of these acids via isoprene and monoterpene photooxidation. The present study may be useful for improving the estimation accuracy of formic and acetic acid emissions from vegetation in future climate change and air quality studies.

Identification of key flowering-related genes and their seasonal expression in Populus tomentosa reproductive buds suggests dual roles in floral development and dormancy

Populus is a major industrial tree species used for bioenergy, timber and pulp manufacturing, which requires an appropriate growth regulation mechanism for long-term survival in response to seasonal climatic changes. As two key processes during life cycle both controlled by photoperiod and temperature, flowering and dormancy have been suggested to share a common regulatory mechanism. In the present study, 31 flowering-related genes in several floral pathways in P. tomentosa were identified. The expression level of these genes was determined using reverse transcription quantitative real-time polymerase chain reaction in female and male buds during the eight stages across the flower bud development. Seasonal expression profiles indicated that 31 flowering-related genes showed different and specific expression trends individually during floral development and dormancy transition. Among these genes, the expression trends for the majority were different between sexes, and the expression abundance of some genes exhibited sex differences. Furthermore, co-expression networks were constructed using 31 flowering-related genes in female and male flower buds, respectively. Many modules of co-expressed genes and hub genes were identified, such as FRIGIDA in female and APETALA1 in male. The results suggested these flowering-related genes play potential dual roles both in floral development and dormancy. This is the first investigation of the expression patterns of flowering-related genes during dormancy transition in P. tomentosa reproductive buds at molecular level. This work would provide important insights to explore connections between floral development and dormancy in perennial trees, and make it possible to enhance vegetative growth and further increase woody biomass accumulation in poplar by regulating key candidate genes using biotechnology.

Assessing the influence of climate on the growth rate of boreal tree species in northeastern Canada through long-term permanent sample plot data sets

Climate has a considerable influence on tree growth. Forest managers benefit from the empirical study of the historic relationship between climatic variables and tree growth to support forest management frameworks that are to be applied under scenarios of climate change. Through this research, we have utilized long-term permanent sample plot records, historic climate data sets, and linear mixed modelling techniques to evaluate the historic influence of climatic variables on the growth rates of major boreal tree species in Newfoundland and Labrador, Canada. For the commercially significant spruce and fir forests of the province, we found growing degree-days (GDD) to negatively correlate with tree productivity in warmer regions, such as much of Newfoundland (±1350 GDD), but positively correlate with growth in cooler regions, such as those in Labrador (±750 GDD). With respect to precipitation, environmental moisture was not on average a limiting factor to species productivity in the province. These dynamics have implications for the productivity of the spruce–fir forests of the study area when considered alongside contemporary climate projections for the region, which generally entail both a warmer and wetter growing environment.

DIVERSITY, DISTRIBUTION AND ECOLOGY OF BOLETOID MUSHROOMS FROM GARHWAL HIMALAYA, UTTARAKHAND

The present investigation was carried out in different mixed broadleaf and coniferous forests of Garhwal Himalaya. Major associates trees are Quercus, Rhododendron, Betula, Pinus, Cedrus and Cupressus in the explored forest. The specimens were collected from these forests between July 2000 to September 2004, in the elevation range of 1600–3000 m above sea level from districts Chamoli, Pauri, Rudraprayag and Tehri. As a result of an extensive field survey and microscopic study in laboratory, 7 genera spread over into 35 taxa belonging to 3 families (Boletaceae, Gyroporaceae and Suillaceae) were identified. Of these, 7 taxa were known to be edible and consumed in various parts of Garhwal region.

Climate‐induced variation in the demography of 14 tree species is not sufficient to explain their distribution in eastern North America

AbstractAimDynamic range models are proposed to investigate species distributions and to project range shifts under climate change. They are based upon the Hutchinsonian niche theory, specifying that the occurrence of a species in an environmental space should be limited to positions where the intrinsic growth rate is positive. Evaluating population growth rate is, however, difficult for physiologically structured populations, such as forest stands, owing to size‐induced individual variation in performance. Therefore, we still have a limited understanding of which aspect of tree demography contributes the most to their geographical range limit. We develop an index of demographic performance for size‐structured populations and study its variation across a climatic gradient. We then investigate the relationship between the demographic performance index and species distribution.LocationNorth America (57–124° W, 26–52° N).Time period1963–2010.Major taxa studiedFourteen tree species.MethodsWe represent forest dynamics with a size‐structured population model and neighbourhood competition with the perfect plasticity approximation. We then derive the lifetime reproduction per individual, , in the absence of density dependence. Using forest inventory data, we assess how tree demography for each species varies with climate. We test the model by comparing and the probability of occurrence within species ranges.ResultsWe find that both growth and mortality rates vary across species distributions, but climate explains little of the observed variation. Individual size and neighbourhood competition are the primary explanatory variables of tree demography. Finally, we find that relates weakly to the probability of occurrence, with no systematic decline in population growth rates towards the range limits.Main conclusionsSpatial and size‐induced variation in tree growth and mortality do not explain range limits and are insufficient to enable an understanding of tree dynamics. We propose that phenomena perceived mostly at the metapopulation scale should also be considered.

Potential distribution of Abies, Picea, and Juniperus species in the sub-alpine forest of Minjiang headwater region under current and future climate scenarios and its implications on ecosystem services supply

Mountain forest ecosystems provide us with life-supporting ecosystem services that are valuable for local, regional, and global communities. Ecological niche-based models have been used extensively, with remarkable success, in understanding the influence of climate change on potential distribution of species. In this study, we used maximum entropy (MaxEnt) modelling to predict the potential distribution of ecologically important tree species, Abies, Picea, and Juniperus, at the eastern edge of the Tibetan Plateau in China. The potential distribution of tree species was modelled and predicted on genus level for current and three representative concentration pathway (RCPs) based future (2050s and 2070s) climate conditions. The model performed well and gave reliable results for current and potential species’ distribution. Precipitation of wettest month was the most important environmental variable for determining the habitat suitability of all tree species, with 30.3% (Abies), 51.2% (Picea), and 57% (Juniperus) contribution to model output, respectively. Temperature seasonality, temperature annual range, and soil type also made the most significant contribution to model outputs. Model projections under current climate highlight that the total suitable habitats, which included regions with different probability of species occurrence, for Abies (3234.2 km2) was much higher than Picea (2003.7 km2) and Juniperus (1784.8 km2). However, projections of habitat suitability under current climate scenario projected onto future climate change scenarios for all concentration pathways in 2050s and 2070s, showed a clear decline in potentially suitable habitats for all three species. The shifts in geographic distributions under future climate scenarios showed an unusual pattern, with slight downward shift of the mean elevation with high habitat suitability for the occurrence of tree species in most RCPs, accompanied by a decrease in the elevational range of suitable habitats. The results of this study highlight the urgent need for forest management strategies to conserve the habitats of these species. Our study offers base-line information on the impact of climate-change on major tree species which can aid in guiding adaptation strategies for forest conservation and management in order to sustain the delivery of ecosystem services in the future.

Ninety-five years of observed disturbance-based tree mortality modeled with climate-sensitive accelerated failure time models

Modeling disturbance-based tree mortality is becoming increasingly important in the discussion of how to adapt forests to climate change and to preserve their ecosystem services and mitigate the risk of economic losses. In this study, we fitted species-specific interval-censored Accelerated Failure Time models for five major tree species to derive the influence of climate, soil, silvicultural measures, stand and tree characteristics on survival times. We coded all disturbance-based mortality causes as events and analyzed 473,501 individual trees distributed across 2248 long-term (1929–2014) forest growth and yield plots in southwestern Germany. We observed different survival probabilities among tree species with Douglas-fir having the lowest survival probability at age 100 years, followed by Norway spruce and Silver fir. Contrastingly, beech and oak had survival probabilities above 0.98 at age 100 years. Most important factor influencing these survival times was climate. Higher summer temperature shortens the survival time of beech, Silver fir and oak, while Norway spruce suffers more from warmer and wetter winters. Beside climatic factors, base saturation showed a significant positive relationship to survival time for all investigated tree species, except for Norway spruce, which had shorter survival times with increasing cation exchange capacity of the soil. Additionally, short-term effects of destabilization after thinning were found. In conclusion, favoring broadleaved tree species, avoiding heavy thinning in older stands and limiting tree age reduce the probability of disturbance-based tree mortality. However, some of the effects found that cause-unspecific mortality modeling has limited potential to describe the mortality–climate change relation.

Estimating economic benefits of urban conifers in terms of abatement of ultrafine dust (PM2.5)

PurposeThis study aimed to estimate the economic benefits of PM2.5 emission abatement by Red Pine, Pinus Koraiensis and Quercus, using a metering model analyzing the amount of PM2.5 absorption in Korea.Design/methodology/approachTo estimate the economic effects of PM2.5 adsorptions by trees, the frequency of hospital visits resulting from respiratory and circulatory diseases was estimated using a Probit model based on the data from National Health and Nutrition Survey.FindingsThe results show that Quercus and Pinus Koraiensis absorb and eliminate the largest amount of PM2.5. Reducing 1 ton of PM2.5 emission through the planting of trees leads to lower incidences of respiratory and circulatory diseases equivalent to the amount of 95 million won. When the trees planted are 2-year-old Red Pine, Pinus Koraiensis and Quercus, the resulting economic benefits of the PM2.5 abatement would amount to 481 million won, 173 million won and 1,027 million won, respectively. If the trees are 80 years old, the economic benefits are estimated to be 73 billion won for Red Pine, 103 billion won for Pinus Koraiensis and 38 billion won for Quercus.Research limitations/implicationsOne limitation of this study is that the weight of PM2.5 adsorbed by each leaf area entirely depended on the experimental results from a prior study and the values are likely to be different from those actually absorbed in natural surroundings. In addition, because of the lack of data from a domestic survey on the surface of leaf area or the reload flow rate of PM2.5, this study referred to data from foreign research. Unfortunately, this specific data may not reflect climatic and terrain characteristics specific to the target country. We used the annual wind speed to calculate the reload flow rate and elimination volume; however, the figures could be more accurate with hourly or daily climate variations. When estimating the health benefits of changes in PM2.5 emissions on respiratory and circulatory diseases, more segmented access to patients' hospital visits and hospital admissions are desirable. Finally, the study focused on the three major tree species of Korea, however, a more detailed study of PM2.5 reduction by various tree types is needed in the future.Originality/valueThis paper quantitatively assessed the amount of PM2.5 adsorption by each of the three tree species. Then, the economic benefits were calculated in terms of how much money would be saved on hospital visits thanks to the reduced PM2.5 levels and lower incidences of respiratory and circulatory system diseases. The net contribution of this study was to prove the trees' function of reducing PM2.5 as it relates to human health. We focused on the most common trees in Korea and compared them to provide new information on the species.

Dynamic top height models for several major forest tree species in Great Britain

Abstract In this paper, we present new dynamic top height models for 10 major species in Great Britain. These models for pure, even-aged stands replace the current, static top height-age curves published in the 1980s, which are no longer reliable in the light of the new data that have been added over the past decades. We followed the generalized algebraic difference approach (GADA) to build the new models and specifically focused on models derived from the Hessfeld IV and Chapman–Richards height-age base equations. We selected a multi-asymptote and polymorphic GADA version of the Chapman–Richards equation for all the species, with the anamorphic functional form as a special case derived from the non-significance of one of the global parameters. The new models are dynamic, accurate and robust, which will permit unbiased yield predictions from current top height-dependent yield simulators in Great Britain.

Classification Binary Trees with SSR Allelic Sizes: Combining Regression Trees with Genetic Molecular Data in Order to Characterize Genetic Diversity between Cultivars of Olea europaea L.

During recent centuries, cultivated olive has evolved to one of the major tree crops in the Mediterranean Basin and lately expanded to America, Australia, and Asia producing an estimated global average value of over USD 18 billion. A long-term research effort has been established with the long-term goal to preserve biodiversity, characterize agronomic behavior, and ultimately utilize genotypes suitable for cultivation in areas of unfavorable environmental conditions. In the present study, a combination of 10 simple sequence repeat (SSR) markers with the classification binary tree (CBT) analysis was evaluated as a method for discriminating genotypes within cultivated olive trees, while Olea europaea subsp. cuspidata was also used as an outgroup. The 10 SSR loci employed in this study, were highly polymorphic and gave reproducible amplification patterns for all accessions analyzed. Genetic analysis indicated that the group of SSR loci employed was highly informative. A further analysis revealed that two sub populations and pairwise relatedness gave insight about synonymies. In conclusion, the CBT method which employed SSR allelic sizes proved to be a valuable tool in order to distinguish olive cultivars over the traditional unweighted pair group method with the arithmetic mean (UPGMA) algorithm. Further research which will combine phenotyping characterization of olive germplasm will have the potential to enable the utilization of existing, and breeding of new, superior cultivars.

Relationships between tree height and tree species richness at small scales

Tree height and tree species richness are both essential to characterize forest structure. Previous research showed that maximum tree height is a strong predictor of tree species richness at forests on a large scale. However, it is unknown whether this relationship exists in a forest at small scales. Here the intensively surveyed data from 1 ha of forest plot in northern Alabama was used to exam this relationship at small scales (e.g., 1 m × 1 m, 2 m × 2 m, …, and 50 m × 50 m). The results indicated that there was no significant correlation between the maximum tree height and tree species richness across small scales. Majority trees with the highest tree height at the small scales were oaks and hickories, which are dominant trees in this forest community through succession. A weak negative spatial autocorrelation existed in tree heights. Tree height distribution across the small scales followed power-laws but with varied scaling exponents. These scaling exponents were significantly correlated with tree species richness when the scales were no less than 1000 m2, which was equivalent to have about 15 tree species in the study area. The results may explain the complicated relationship between tree species diversity and tree height. This study may provide implications for forest structure management and conservation.

Mitigation of bark stripping on spruce: the need for red deer population control

Norway spruce (Picea abies (L.) Karst.) is a major production tree species for the European wood industry. However, it is highly sensitive to bark stripping (BS) by red deer (Cervus elaphus L.), which causes large timber losses. Because the red deer population has increased over the last decades, a better understanding of the underlying causes driving BS is urgently needed. BS outbreaks are multifactorial: winter food shortage, local and regional deer abundance and stand properties (thermal and visual cover, and scarcity of herbaceous layers) have been found to drive BS rates. Although the influence of each of these factors is well studied, there is still no consensus on their relative contributions to BS or what mitigation strategy is best. In this study, we made use of a long-term, large-scale BS inventory (13 years over 2570 km2) to fill these gaps. We modeled winter and summer BS rates in response to the most explanatory variables, selected from a large set of environmental variables. Our results highlight the prevalence of deer abundance combined with high sensitivity of coniferous thickets and pronounced habitat selection by deer for these stands. Our findings show that the control of red deer populations is a key measure for reducing BS in Norway spruce stands.

Tree Allergen Pollen-Related Content as Pollution Source in the City of Ourense (NW Spain)

Allergies became a major public health problem, identified as an important global pandemic with a considerable impact on the worldwide economy. In addition, a higher prevalence of pollen Type I sensitization cases in urban environments in comparison with the rural territories was detected. Our survey sought to assess the main biological pollution episodes caused by the aeroallergens of the major allergenic tree species in urban environments. A Hirst-type volumetric device was used for pollen sampling and a Burkard Cyclone sampler for the detection of tree atmospheric allergens over two years. The main allergens of Alnus, Fraxinus, Betula, Platanus and Olea, were detected in the atmosphere. Three peaks of important pollen concentrations were recorded throughout the year. The developed regression equations between pollen counts and allergen proteins registered great R2 values. The number of days with probability of allergenic symptoms was higher when the pollen and allergen data were assessed altogether. Fraxinus allergens in the atmosphere were detected using Ole e 1 antibodies and the Aln g 1 allergens with Bet v 1 antibodies, demonstrating the cross-reaction processes between the principal allergenic proteins of the Oleaceae and Betulaceae families. Long Distance Transport processes (LDT) showed that pollen from Betula populations located in mountainous areas increased the secondary peaks of pollen and allergen concentrations, and air masses from extensive olive orchards of North-Eastern Portugal triggered the highest concentrations in the atmosphere of Olea pollen and Ole e 1 allergens.

Vertical distribution of radiocesium concentrations among crown positions and year-to-year variation in four major tree species after the Fukushima Daiichi Nuclear Power Plant accident

To evaluate the distribution of radiocesium (137Cs) among crown positions in trees after the Fukushima Daiichi Nuclear Power Plant accident, we collected foliage and branch samples from different crown positions of four major tree species (Chamaecyparis obtusa, Cryptomeria japonica, Pinus densiflora, and Quercus serrata) from 2011 to 2019 in northeast Japan. We divided the samples into current-year and more than 1-year-old groups (called old foliage and old branches), which sometimes included directly contaminated parts. The 137Cs activity concentration in dry foliage and branches was measured using a germanium semiconductor detector. There were complex differences in the relative 137Cs activity concentration among species and organ types (i.e., foliage and branches) among crown positions. The relative 137Cs activity concentration in current-year foliage was higher in the upper crowns of C. obtusa, but higher in lower crown positions in C. japonica. No differences among crown positions were observed in P. densiflora and Q. serrata. In current-year branches, the relative 137Cs concentration in Q. serrata was similar among crown positions but higher in the upper crown in P. densiflora. The concentrations in old foliage and old branches in all species tended to be higher in the lower crown. The factors causing these interspecific and organ type differences among crown positions may be related to the organ turnover rate, dilution effect due to different growth rates, and potassium distribution within the crown. No year-to-year variation was observed in most foliage and branches in all species, except for current-year branches of Q. serrata, old foliage in C. japonica and P. densiflora, and old branches in P. densiflora. Our long-term data on the interspecific and inter-organ patterns of contamination, focusing on variation among crown positions and year-to-year trends, might help to improve the estimation of 137Cs deposition and dynamics in polluted forest ecosystems.

Identification of fungi in Tunisian olive orchards: characterization and biological control potential

BackgroundOlive production is the main agricultural activity in Tunisia. The diversity of fungi was explored in two different olive groves located in two distant geographical zones in Sfax (Tunisia) with different management practices.ResultsFungal isolation was made from soil and the major olive tree pests, namely the Olive fly, Bactrocera oleae Gmelin (Diptera: Tephritidae), and the Olive psyllid, Euphyllura olivina Costa (Homoptera: Psyllidae). A total of 34 fungal isolates were identified according to their phenotypic, genotypic, biochemical and biological activities. Twenty fungal species were identified belonging to six different genera (Alternaria, Aspergillus, Cladosporium, Fusarium, Lecanicillium and Penicillium) by the analysis of their ITS1–5.8S–ITS2 ribosomal DNA region. Different bioassays performed in this work revealed that 25/34 (73.5%) of the identified fungal isolates showed an entomopathogenic and/or antagonistic activity, 9/34 (26.5%) of them displayed phytopathogenic features.ConclusionsFungal species that showed entomopathogenic and/or antagonistic potentialities and that are non-phytopathogenic, (17/34; 50%) of our fungal isolates, could be explored for olive protection against fungal diseases and pests, and might have a future application as biocontrol agents.