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A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Ecophysiology and Biology".

Deadline for manuscript submissions: closed (11 November 2021) | Viewed by 27665

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Special Issue Editors

Dr. Helena Ribeiro

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Guest Editor

Department of Geosciences, Environment and Spatial Plannings, University of Porto Pole, Porto, Portugal
Interests: aerobiology; phenology; crop forecasting; pollen biology

Dr. Maria Fernández-González

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Guest Editor

Sciences Faculty, University of Vigo, 32004 Ourense, Spain
Interests: aerobiology; phenology; agronomy; phytopathology; climate change; ecology; epidemiology; human health; allergy; allergens; pollen; spores; meteorology; prediction models

Special Issue Information

Dear Colleagues,

We are kindly inviting you to submit original research or review articles to a Special Issue of Forests focused on Tree pollen and Floral Biology.

Pollen and floral biology studies are important for tree crop management, breeding programs, gene flow monitoring, and for developing strategies aiming at forest sustainability management and adaptation. Additionally, environmental challenges caused by biotic and abiotic stress factors such as climate warming, pollution, drought, pests, and pathogens, among others, have an impact on floral development, pollen traits, pollination, and other aspects related to tree reproduction. To cope with these challenges and understand how they influence forests and forest ecosystems, we need to assemble the current state of knowledge and progress on this particularly relevant research field.

This Special Issue seeks experimental and field studies or modeling approaches of any aspect related to tree pollen and floral biology. Relevant topics include: aeropalynological monitoring, modeling, and trends; growth and yield modeling based on pollen and floral phenology; remote sensing studies for mapping and predicting flower phenology; effects of abiotic or biotic factors such as climate change and pollution on pollen and floral development, including inter- and intraspecific variation; floral bud induction, floral development, and its regulators; pollen–styles interaction and male sterility; physiological, biochemical, genetic, and metabolic studies; pollen formation, production, morphology, fertility, allergenicity, and chemical composition.

Dr. Helena Ribeiro
Prof. Maria Fernández-González
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Forests is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

Aeropalynology
Phenology
Remote sensing
Monitoring and modeling
Floral development
Functional biology
Climate change
Pollution

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Published Papers (9 papers)

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Research

13 pages, 2745 KiB

Open AccessArticle

Microsporogenesis, Pollen Ornamentation, Viability of Stored Taxodium distichum var. distichum Pollen and Its Feasibility for Cross Breeding

by Ziyang Wang, Ming Yin, David L. Creech and Chaoguang Yu

Forests 2022, 13(5), 694; https://doi.org/10.3390/f13050694 - 29 Apr 2022

Cited by 5 | Viewed by 2195

Abstract

Taxodium Rich is well known for its flooding tolerance and has great ecological and economic potential. A comprehensive understanding of pollen characteristics and storage capacity is important for breeding and genetic resource conservation of the genus. In this study, we observed the microsporogenesis and pollen ornamentation, studied the conditions of in vitro pollen germination, compared the difference in pollen viability of T. distichum var. distichum measured by in vitro germination and TTC staining, analyzed the change in pollen viability after different storage times and the feasibility of using stored pollen for cross breeding. Results indicated that the pollen mother cells of T. distichum var. distichum begin to enter the meiosis stage one month before the male strobilus disperse, reach metaphase 10 days after meiosis and form pollen grains three to five days after tetrad development. Pollen germination rate topped in the culture medium of 0.012% boric acid under 30 °C after 48 h, reaching 66.81%. The TTC staining demonstrated that the pollen viability of T. distichum var. distichum TD-4 and TD-5 were 97.78% and 80.54%, 98.96% and 91.67%, and 83.67% and 21.75% after one-, two- and three-year storage at −20 °C, which is significantly higher than (p < 0.05) that of 17.02 and 27.04%, 2.77% and 12.82%, and 0 determined by the in vitro cultivation. It is feasible to use pollen of T. distichum var. distichum TD-4 and TD-5 stored at −20 °C for one year for artificial hybridization, and the fruit setting rate and seed germination rate were 10.94 and 36.79%, and 11.47 and 65.76%, respectively. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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20 pages, 3216 KiB

Open AccessArticle

Data Mining Methods to Detect Airborne Pollen of Spring Flowering Arboreal Taxa

by Estefanía González-Fernández, Sabela Álvarez-López, Alba Piña-Rey, María Fernández-González and Francisco Javier Rodríguez-Rajo

Forests 2021, 12(12), 1801; https://doi.org/10.3390/f12121801 - 18 Dec 2021

Cited by 1 | Viewed by 2669

Abstract

Variations in the airborne pollen load are among the current and expected impacts on plant pollination driven by climate change. Due to the potential risk for pollen-allergy sufferers, this study aimed to analyze the trends of the three most abundant spring-tree pollen types, Pinus, Platanus and Quercus, and to evaluate the possible influence of meteorological conditions. An aerobiological study was performed during the 1993–2020 period in the Ourense city (NW Spain) by means of a Hirst-type volumetric sampler. Meteorological data were obtained from the ‘Ourense’ meteorological station of METEOGALICIA. We found statistically significant trends for the Total Pollen in all cases. The positive slope values indicated an increase in pollen grains over the pollen season along the studied years, ranging from an increase of 107 to 442 pollen grains. The resulting C5.0 Decision Trees and Rule-Based Models coincided with the Spearman’s correlations since both statistical analyses showed a strong and positive influence of temperature and sunlight on pollen release and dispersal, as well as a negative influence of rainfall due to washout processes. Specifically, we found that slight rainfall and moderate temperatures promote the presence of Pinus pollen in the atmosphere and a marked effect of the daily thermal amplitude on the presence of high Platanus pollen levels. The percentage of successful predictions of the C5.0 models ranged between 62.23–74.28%. The analysis of long-term datasets of pollen and meteorological information provides valuable models that can be used as an indicator of potential allergy risk in the short term by feeding the obtained models with weather prognostics. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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17 pages, 1848 KiB

Open AccessArticle

Pinus Pollen Emission Patterns in Different Bioclimatic Areas of the Iberian Peninsula

by María Fernández-González, Beatriz Lara, Estefanía González-Fernández, Jesús Rojo, Rosa Pérez-Badia and Fco. Javier Rodríguez-Rajo

Forests 2021, 12(6), 688; https://doi.org/10.3390/f12060688 - 27 May 2021

Cited by 4 | Viewed by 3037

Abstract

Background: In the Northern Hemisphere, pine forests predominate due to their natural distribution and silvicultural importance. Pinus tree species are large pollen producers. Nowadays, the context of climate change influences their distribution, abundance, growth and productivity. The objectives of the study were to assess the patterns of the Pinus flowering behavior regarding their pollen presence in the atmosphere and intensity in different bioclimatic areas of the Iberian Peninsula during recent years. Methods: The survey was carried out in three different biogeographic zones of Spain: Vigo (Eurosiberian region) and Ourense (transition area between the Eurosiberian and Mediterranean areas) located in northwest Spain and Toledo (Mediterranean area) placed in the center of the Iberian Peninsula. Airborne pollen was collected with volumetric traps in each study area from 1995 to 2019. Results: Pinus pollen showed a marked single pollination period during late March in the Eurosiberian region and April in the transition zone between the Eurosiberian and the Mediterranean area. Two different peaks with lower pollen intensity were detected during the pollen season in Toledo (Mediterranean area), the first during late March and the second from the end of May to the beginning of June. The trends detected revealed changes in the timing of the phenological cycle, such us longer pollen seasons and later end dates of the Main Pollen Season (MPS) in some cases. The mean Annual Pollen Integral (API) in the Eurosiberian area (Vigo) and transition zone (Ourense) was similar, with about 4400 pollen grains. In the Mediterranean area (Toledo), a lower API amount of 1618 pollen grains was recorded. A trend towards an increase of 126 and 80 pollen grains per year in the airborne pine load was detected in the transition and Mediterranean areas studied, respectively. Conclusions: The rates of the annual integral Pinus pollen percentage with respect to the total pollen of forest species in the atmosphere of the areas studied showed a decreasing percentage trend during the last years. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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16 pages, 4551 KiB

Open AccessArticle

Reproductive Biology of Olive Trees (Arbequina cultivar) at the Northern Limit of Their Distribution Areas

by Alejandro Garrido, María Fernández-González, Rosa A. Vázquez-Ruiz, F. Javier Rodríguez-Rajo and María J. Aira

Forests 2021, 12(2), 204; https://doi.org/10.3390/f12020204 - 10 Feb 2021

Cited by 8 | Viewed by 3586

Abstract

In recent years, North-western Spain has experienced an increase in the cultivated area of olive trees. The main propitious areas for olive groves are the Miño and Sil basins, as a consequence of their Oceanic climate with Mediterranean influence. The objective of this study is to determine the characteristics of reproductive biology, phenological and aerobiological behaviour of olive trees in the most northerly new plantation areas of the Iberian Peninsula. The study was carried out in an olive grove growing Olea europaea L. cv. ‘Arbequina’ located in Quiroga (Lugo) from 2016 to 2018. The phenological observations were based upon the main growth stages following the Biologische Bundesanstalt Bundessortenamt and Chemical industry (BBCH) scale. To predict the onset of flowering, a thermal time model was used in order to quantify the chill requirements, and growing degree-days were applied to determine the heat requirement. The production, viability and germination rates of Olea pollen were evaluated from samples selected in nine individual trees for the phenological survey. The aerobiological study was conducted by means of a Hirst-type pollen trap located in the centre of the olive grove. The vegetative period of the olive tree in the study area lasted an average of 259 days. The important phenological stage 6 (flowering) was the shortest stage. An average of 704 Chilling Hours (CH) with a threshold of 2.5 °C was required to overcome the chilling period, 1139 Growing Degree Days (GDD) for the beginning of flowering, and 4463 GDD for harvest. The pollen production per anther was 82589 grains (± 14084 pollen grains), with a rate of 81% viability and 12% pollen tube germination. The main pollen season started on average on May 20th and ended on June 16th with an average duration of 27 days and an annual pollen integral of 833 pollen grains. The low pollen concentrations could be a consequence of the Northern location of the forest, in a bioclimatic transition zone between the Eurosiberian and the Mediterranean areas, at the limit of olive tree distribution. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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16 pages, 1814 KiB

Open AccessArticle

The Strong and the Stronger: The Effects of Increasing Ozone and Nitrogen Dioxide Concentrations in Pollen of Different Forest Species

by Sónia Pereira, Maria Fernández-González, Alexandra Guedes, Ilda Abreu and Helena Ribeiro

Forests 2021, 12(1), 88; https://doi.org/10.3390/f12010088 - 15 Jan 2021

Cited by 11 | Viewed by 3322

Abstract

The knowledge of pollen sensitivity and tolerance to stress factors such as air pollution is important for forest sustainability, ensuring the most efficient production with the highest benefits and lowest resource losses. This study intended to evaluate the influence of common air pollutants in four forest trees species, Betula pendula Roth, Corylus avellana L., Acer negundo L. and Quercus robur L., through a comparative analysis at the same experimental conditions. We aimed to investigate the effect that may occur in pollen fertility, protein content, oxidative stress and wall composition after exposure in vitro to ozone and nitrogen dioxide at concentration levels for vegetation protection in Europe. Our results suggest changes in pollen viability, protein content and differential sensitivity related to ROS synthesis, NADPH oxidase activity, as well as in wall composition. The results indicate that NO₂ exposure affected more the pollen species studied mostly at the highest concentration exposure. As for ozone, there were less significant differences between samples; however, a different behavior occurs in O₃ expositions, where the most influence happens at the legal limit for vegetation protection in Europe. Our study showed that significant pollen functions could be compromised even at common air pollutant’s concentrations. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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31 pages, 3991 KiB

Open AccessArticle

Pollen Morphology and Variability of Abies alba Mill. Genotypes from South-Western Poland

by Dorota Wrońska-Pilarek, Monika Dering, Jan Bocianowski, Kacper Lechowicz, Wojciech Kowalkowski, Władysław Barzdajn and Maria Hauke-Kowalska

Forests 2020, 11(11), 1125; https://doi.org/10.3390/f11111125 - 22 Oct 2020

Cited by 10 | Viewed by 2943

Abstract

The objective of this study was to investigate pollen morphology and ranges of intraspecific variability of Abies alba Mill. Pollen grains were collected from nine clonal seed orchards of A. alba in the Sudety Mountains, (South-Western Poland). At each seed orchard, 4–6 grafts were selected. Each individual (graft) was represented by 30 pollen grains and 1440 pollen grains were measured totally. Eight quantitative and four qualitative features of pollen grains were analysed. The diagnostic features of pollen grains for the studied species were: Exine surface of pollen corpus (cappa and leptoma) and sacci, the length of the polar axis (P), pollen shape (P/E ratio), and a new trait—saccus shape (A/B ratio — saccus width (A) to his length (B)). Pollen features made possible to differentiate seven individual genotypes (samples). To our knowledge, this is the first time that the intraspecific and interindividual variability of pollen grains of A. alba were investigated. The most different were the pollen grains from samples—genotypes 13 (Bystrzyca Kłodzka) and 18 (Jugów), and also (although to a lesser extent) genotypes—11 (Kamienna Góra), 30, 31 (Jugów), and 44 (Szklarska Poręba). No significant relationships were observed between the pollen grain traits and the geographical location of the collection sites. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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16 pages, 3499 KiB

Open AccessArticle

Atmospheric Pathways and Distance Range Analysis of Castanea Pollen Transport in Southern Spain

by Rocío López-Orozco, Miguel Ángel Hernández-Ceballos, Carmen Galán and Herminia García-Mozo

Forests 2020, 11(10), 1092; https://doi.org/10.3390/f11101092 - 14 Oct 2020

Cited by 8 | Viewed by 2171

Abstract

The sweet chestnut (Castanea sativa Mill.) is the only native species of this genus in Europe, where it faces various threats that are causing a severe decrease in populations, with the resulting loss of genetic diversity. In the Iberian Peninsula, it is of high economic and ecological importance, being well represented, especially in northern areas, whilst it is limited to isolated populations in medium-range mountains in southern Spain (Andalusia region). Taking advantage of this fragmented distribution, this study analyzes the dynamics of atmospheric transport of Castanea pollen through Andalusia region in order to obtain a better understanding of the pollination pathways as a key aspect of the floral biology of this partially anemophilous species. The aerobiological characteristics of this species are also of special interest since its pollen has been recognized as allergenic. Pollen transport pathways were studied by applying back-trajectories analysis together with aerobiological, phenological, land cover, and meteorological data. The results reveal that airborne Castanea pollen concentrations recorded in the city of Cordoba, in the center of Andalusia region, reach medium- and even long-range distances. The backward-trajectory analysis indicates that most of the pollen data detected outside the Castanea flowering season were related to westerly slow and easterly airflows. Furthermore, some of the case studies analyzed indicate the presence of southerly airflow patterns, which could influence medium- and long-range transport events from chestnut populations further south, even from those located in north African mountains. The integrated analysis of the results offers us better knowledge of the cross-pollination pathways of this endangered species, which help us to understand its genetic flows, as a basis for designing conservation strategies for this highly fragmented species in southern Spain. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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18 pages, 2185 KiB

Open AccessArticle

Pollen Production of Quercus in the North-Western Iberian Peninsula and Airborne Pollen Concentration Trends during the Last 27 Years

by María Fernández-González, Estefanía González-Fernández, Helena Ribeiro, Ilda Abreu and F. Javier Rodríguez-Rajo

Forests 2020, 11(6), 702; https://doi.org/10.3390/f11060702 - 24 Jun 2020

Cited by 18 | Viewed by 3009

Abstract

Natural forests are considered a reservoir of great biological diversity constituting one of the most important ecosystems in Europe. Quercus study is essential to assess ecological conservation of forests, and also of economic importance for different industries. In addition, oak pollen can cause high sensitization rates of respiratory allergies in pollen-allergy sufferers. This study sought to know the pollen production of six oak species in the transitional area between the Eurosiberian and Mediterranean Bioclimatic Regions, and to assess the impact of climate change on airborne oak pollen concentrations. The study was conducted in Ourense (NW Spain) over the 1993–2019 period. A Lanzoni VPPS 2000 volumetric trap monitored airborne pollen. A pollen production study was carried out in ten trees randomly selected in several Quercus forest around the Ourense city. Oak pollen represented around 14% of annual total pollen registered in the atmosphere of Ourense, showing an increasing trend during the last decade. Pollen production of the six studied oak species follow the proportions 1:1:2:5:90:276 for Q. ilex, Q. faginea, Q. rubra, Q. suber, Q. pyrenaica, and Q. robur respectively. We detected a significant trend to the increase of the annual maximum temperature, whereas a decrease of the maximum and mean temperatures during three previous months to oak flowering. This could be related with the detected trend to a delay of the oak Main Pollen Season onset of 0.47 days per year. We also found significant trends to an increase of the annual pollen integral of 7.9% pollen grains per year, and the pollen peak concentration of 7.5% pollen grains per year. Quercus airborne pollen monitoring as well as the knowledge of the reproductive behavior of the main oak species, bring us an important support tool offering a promising bio-indicator to detect ecological variations induced by climate change. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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14 pages, 4093 KiB

Open AccessArticle

Flowering Phenology and Characteristics of Pollen Aeroparticles of Quercus Species in Korea

by Iereh Kim, Myeong Ja Kwak, Jong Kyu Lee, Yeaji Lim, Sanghee Park, Handong Kim, Keum-Ah Lee and Su Young Woo

Forests 2020, 11(2), 232; https://doi.org/10.3390/f11020232 - 20 Feb 2020

Cited by 5 | Viewed by 3475

Abstract

In recent decades, airborne allergens for allergic respiratory diseases have been found to increase significantly by a process of converting coniferous forests into broad-leaved forests in Korea. This study was conducted to evaluate factors, including airborne pollen counts, micromorphology, and flowering phenology, that can affect oak pollen-related allergic symptoms. The catkin of Mongolian oak (Quercus mongolica Fisch. ex Ledeb.) showed the most rapidly blooming catkin on Julian day 104 in flower development. Among six species, the last flowering was observed on Julian day 119 in Korean oak (Quercus dentata Thunb.). The pollen dispersal was persisted for about 32 days from Julian day 104 to Julian day 136. Airborne pollen was observed about 2 weeks after flowering phase H, the senescence phase. Pollen size varied by species, with the largest from Q. mongolica (polar axis length, PL = 31.72 µm, equatorial axis length, EL = 39.05 µm) and the smallest from Jolcham oak (Quercus serrata Murray) (PL = 26.47 µm, EL = 32.32 µm). Regarding pollen wall structure, endexine of Q. dentata was coarsely laminated or fragmented. The endexine thicknesses of Sawtooth oak (Quercus acutissima Carruth.) and Q. serrata were thick and stable, whereas Galcham oak (Quercus aliena Blume), Q. mongolica, and Oriental cork oak (Quercus variabilis Blume) had thinner endexines. The area occupied by pollenkitt of Q. variabilis was significantly larger than that of Q. acutissima. Importantly, Q. variabilis had a distinctly thick 17 kDa protein band, a presumed major allergen. Oak species differ in pollen protein composition, and thus there is a possibility that the allergenic activity of pollen proteins vary depending on oak species. This study highlights the fact that native oak species in Korea differ in flowering pattern of male flowers, pollen morphology, and pollen chemical constituents. These discrepancies in flowering and pollen properties imply variable allergic responses to oak pollen from different species. Full article

(This article belongs to the Special Issue Tree Pollen and Floral Biology)

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