Notes on tenuipalpid mites associated with Quercus pubescens in southern Italy

During a survey of the flat mites (Tenuipalpidae) on forest trees and agricultural crops in five different sites of the Apulian territories (Southern Italy) in 2019, Brevipalpus recki (Livschitz and Mitrofanov) and Cenopalpus longirostris (Livschitz and Mitrofanov) were collected on Quercus pubescens (Willdenow) (Fagaceae). The authors give an account of the new record of C. longirostris, which was not listed in the previous Italian fauna, and of the finding of B. recki in southern Italy, since it was only mentioned from the northern region of the country so far. In addition, the paper lists Q. pubescens as a new host plant for C. longirostris.

Оценка экологического режима местообитаний растений в условиях изменения климата

Приводятся результаты исследования климатогенных изменений экологического режима местообитаний Quercus pubescens Willd. на высотном профиле в условиях Южного берега Крыма. В результате современного потепления климата ЮБК в начале XXI века факторы термо- и омброрежима для дуба пушистого на высотах 100-200 м над уровнем моря сместились в зону пессимума, что может послужить отправной точкой для сукцессионных изменений на этих высотах. Произошел сдвиг зоны оптимума климатических факторов на высоты 400 м над уровнем моря. При сохранении тенденции роста температур к концу XXI века на ЮБК ожидается смещение климатических оптимумов произрастания Q. pubescens на высоты до 600 м над уровнем моря. Данный подход может быть использован при анализе вероятных изменений экологических условий местообитаний для конкретных видов растений при прогнозируемых изменениях климата, разработке мероприятий по оптимизации ландшафтов.

Фенологическая реакция Quercus pubescens Willd. на климатические изменения в условиях сухих субтропиков

Протестированы три фенологические модели для прогнозирования сроков развертывания листьев, начала цветения и оценки возможных сдвигов весеннего развития Quercus pubescens Willd. в связи с изменением климата. Модель (М1) основана на методе накопления только тепловых единиц (F). Комбинированные модели (M2 и M3) – на последовательном накоплении охлаждающих и тепловых единиц (CF), причем модифицированная модель М3 также учитывает влияние фотопериода на растение. На основе данных наблюдений оптимизированы дата начала накопления тепловых единиц после завершения периода покоя, их необходимая сумма для начала фенофаз и пороговая температура. Начальной датой для накопления единиц охлаждения было выбрано 1 ноября. Для параметризации моделей использованы фенологические наблюдения и суточные данные температуры воздуха за период с 1936 по 2017 гг. Тестирование показало высокую степень адекватности при прогнозировании дат развертывания листьев и начала цветения Q. pubescens модели М3, учитывающей влияние фотопериода. Простая тепловая модель и последовательные модели накопления охлаждающих и тепловых единиц совместно с метеорологическими прогнозами, основанными на трех сценариях изменения климата проекта CMIP5 (RCP2.6, RCP4.5 и RCP8.5) были использованы для оценки сроков развертывания листьев и начала цветения Q. pubescens в течение 21-го столетия. Расчеты показали, что при развитии сценария RCP8.5 потепление может оказать значительное воздействие на выход почек из органического покоя, и как следствие – на сроки весеннего развития.

Mediterranean trees vulnerability to climate change will not be minimized through hydraulic safety traits adjustments.

<p><span>Climate change in the Mediterranean region leads to an intensification of summer droughts. These episodes of extreme water stress threaten the survival of tree species and, by the same token, would affect the structure and ecosystem services of woodlands. Indeed, in conditions of prolonged and intense drought, one of the major risks for trees is the hydraulic failure due to high embolism level. Xylem embolism risk depends essentially on various leaf and hydraulic traits including (i) the vulnerability of their xylem to cavitation, (ii) the turgor loss point (a surrogate for stomatal control) and (iii) their cuticular transpiration (gmin). The two former traits can be used to compute hydraulic safety margins (HSM). </span></p><p><span>In order to assess whether trees will survive future climatic conditions, it is necessary to quantify and assess the plasticity of these traits to intensified drought. In this study, we used three rainfall exclusion experiments established in mature forests in south-eastern France (Font-blanche, Puéchabon and O3HP experimental sites) to measure these traits and evaluate their ability to adjust to aggravated drought conditions for three Mediterranean widespread species: </span><span><em>Quercus ilex</em></span><span>, </span><span><em>Quercus Pubescens</em></span><span>, and </span><span><em>Pinus halepensis</em></span><span>. We performed pressure-volume curves of trees from rainfall exclusion and control plots to see if adjustments of gmin and leaf hydraulic traits involved in stomatal regulation occurred in these three species. Using the optical method and cavitron, we also quantified the plasticity of xylem vulnerability to cavitation by comparing the values of water potential leading to a 50% reduction in plant hydraulic conductance (P50). </span></p><p><span>Our results show that </span><span><em>Quercus pubescens</em></span><span> has the lowest HSM while </span><span><em>Quercus ilex</em></span><span> has the highest. In addition, gmin is higher for </span><span><em>Quercus pubescens</em></span><span> than for the other two species. All together these results suggest that </span><span><em>Quercus pubescens</em></span><span> is the most vulnerable to drought among the three studied. Globally, for most traits and species no significant difference was found between treatments. The only exception was for </span><span><em>Quercus ilex</em></span><span> that exhibited lower turgor loss point (Ψtlp) in the dry treatment. Drought acclimation for these species may rather depend on other traits, such as leaf area reduction or rooting depth. To integrate the role of these traits to estimate the historic and future mortality risk for these species, the use of hydraulic based models will be of interest. </span></p>

Extramatrical Mycelium and Ectomycorrhizal Community Composition of Quercus pubescens in a Sub-Mediterranean Stress-Prone Environment

Temporal studies that would offer insight into resilience of ectomycorrhizal (ECM) communities in stress prone climates are scarce despite their role in tree nutrition and water supply. Our study characterized the vitality, community composition, diversity, and function of Quercus pubescens Willd. ECM fungi in the Sub-Mediterranean stress-prone environment for 2 consecutive years (June 2016–May 2018) and related the investigated measures to environmental parameters. ECM community was assessed for species actively associating with root tips and exploring the soil volume through the assessment of mycelial ingrowth into sand-filled mesh bags. The investigated period was characterized by a drier than average summer combined with wildfire in 2016 followed by another dry summer in 2017. The vital to non-vital ECM root tip ratio decreased below one in August 2016 and remained low until January 2018. This was ascribed to a series of stress events that occurred at the site including sequential droughts and wildfire. The most abundant ECM lineages on root tips were Tomentella and other Thelephoraceae, Sebacina, and Cenococcum while in mesh bags the most abundant were Tomentella, Sebacina, Pseudotomentella, Pyronemataceae, Inocybe, Cortinarius, Agaricales, and Boletales lineages. High intra-site variability was observed, with ECM communities directly associated with root tips and exploring the soil volume varying significantly among the plots. Community composition was stable over time, while species richness varied with mean air and soil temperature, relative air humidity, and solar radiation. The most abundant exploration type observed at this site was short distance, which was associated with precipitation along with long distance exploration type. The medium distance exploration type was temporally variable and responded to soil temperature and relative air humidity reflecting seasonality at the site. The presented results indicate complex relationships between environmental parameters, abiotic stress, and ECM fungi.

Halophytophthora fluviatilis Pathogenicity and Distribution along a Mediterranean-Subalpine Gradient

Halophytophthora species have been traditionally regarded as brackish water oomycetes; however, recent reports in inland freshwater call for a better understanding of their ecology and possible pathogenicity. We studied the distribution of Halophytophthora fluviatilis in 117 forest streams by metabarcoding river filtrates taken in spring and autumn and by direct isolation from floating leaves. Pathogenicity on six Fagaceae species and Alnus glutinosa was assessed by stem inoculations. The distribution of H. fluviatilis was correlated with high mean annual temperatures (>93.5% of reports in Ta > 12.2 °C) and low precipitation records. H. fluviatilis was therefore widely distributed in forest streams in a warm–dry climate, but it was mostly absent in subalpine streams. H. fluviatilis was primarily detected in autumn with few findings in spring (28.4% vs. 2.7% of streams). H. fluviatilis was able to cause small lesions on some tree species such as Quercus pubescens, Q. suber and A. glutinosa. Our findings suggest that H. fluviatilis may be adapted to warm and dry conditions, and that it does not pose a significant threat to the most common Mediterranean broadleaved trees.

Investigation of the material resistance and moisture performance of pubescent oak (Quercus pubescens)

Forests are under great pressure due to climate changes. It is forecast that the importance of Mediterranean type forests will significantly increase. Among various types of oak species, pubescent oak (Quercus pubescens) will likely gain ecological and economic importance in the region south of Alps. Although this wood species is well known, there are not much data available about chemical properties and durability. A comprehensive analysis of extractives and durability against wood decay fungi was therefore performed. The results of the chemical analysis revealed that heartwood contains up to 20% of the extractives, with considerable amounts of phenols, including a fairly high concentration of Gallic acid (GAc). Anatomical structure, with high frequency of tylosis, resulted in good water exclusion efficacy. The presence of biologically active extractives and superior water exclusion efficacy resulted in good durability, as shown by basidiomycetes tests. Based on the laboratory data, factors that determine the service life of wood were calculated. Data indicate superior performance in above-ground applications.

Features Of Photosynthesis And Water Regime Of Quercus Pubescens Willd. Under The Conditions Of Autumn Drought Of The Southern Coast Of The Crimea

The objective of the research is to determine the optimal zones and thresholds of soil moisture, temperature, illumination, limiting photosynthesis and transpiration of Quércus pubéscens Willd. and allowing the introduction of the species to other regions. The dependences of the net photosynthesis rate (Pn) and the transpiration rate (E) on stomatal conductivity (gs), leaf temperature (Tl), and soil moisture (Ws) are shown. The ratio of the processes of photosynthesis and respiration, under the influence of soil drought, allowed us to define their optimal values: Ws = 26 – 28%, Pn = 16 –18 μmol/m2c, Rt = 2 – 4 μmol/m2c. The relationship between the net photosynthesis rate, total respiration, and leaf temperature allowed us to determine the temperature maximum of net photosynthesis (the thermal compensation point): Pn = Rt = 2.0 μmol/m2c at Tl = 37ºC. It was found that in the absence of soil drought, the proportion of respiratory costs (Rt/Pg) from true photosynthesis is 20 – 23%, and with soil moisture of 8 – 10% increases to 55 – 58%.