Dry Summer Period Research Articles

Computer simulation of the soil water regime under an apple orchard in a mountainous area (using the example of the leached chernozem of the experimental agricultural station Gorno-Altaiskoe)

Relevance. Progressive degradation of farmland soils – erosion, salinization, desertification. Aim. To establish features of water-physical properties of leached chernozem under an apple orchard and associated patterns of soil profile moisture distribution in summer period when precipitation deficiency observed. Methods. Moisture content in soil horizons was determined by the gravimetric method. To determine the granulometric composition of soils, the pipette method was used. The soil bulk density was determined by the cutting ring method. For solid phase density determination the pycnometric method was used. The method of graphic interpolation was used for transition the soil texture classification from Russian to international one. Water infiltration modeling into the soil profile was carried out using the HYDRUS-1D program. The parameters of approximating of the water retention curve of soils by the Van Genuchten equation were obtained by the calculation method of pedotransfer functions «Rosetta Lite» of the RETC program, using data on soil density and soil texture. Results. It has been established that the upper well-structured horizons of leached chernozem under an apple orchard have a greater water-holding capacity; their water-retention curves are more flattened. The water retention curve of the more structureless B2k horizon, the soil texture of which is dominated by sandy fractions, is shifted towards lower humidity. During hot and dry summer period the moisture deficiency in the soil was noted only in the upper twenty-centimeter soil column (14 mm). The moisture of the lower horizons, where the bulk of tree roots are concentrated, is satisfactory. The model demonstrates the smallest discrepancies with the moisture values measured during the soil reclamation experiment one day after the start. The downward moisture penetration into the lower soil layers is prevented by low pressure in the clayey A and AB horizons. Selection of input parameters and debugging of the model based on experimental data allows it to be used to simulate further processes occurring in the soil. It was revealed that the formation of positive (upward) water flows, which ensure the “pull-up” of salts and substances from the lower part of the profile to the upper layers during dry periods of the year, has a significant impact on moisture distribution in the chernozem under the apple orchard.

Morphodynamics of ecological scours as deep pool habitats

Climate change leads among other consequences to extreme hot and dry periods in summer with extremely low water depths which impose an increasing threat to fish populations in river systems. For example, in south-western Germany severe fish mortality was observed in the extreme summer of 2018 which could be justified by a lack of deep pool habitats providing enough water depth and cold-water refuges. This study aims to provide engineering measures to create local scours that should fulfil the function of sustainable deep pool habitats. In this research, six different prototypes common in-stream measures are tested experimentally under clear-water scour conditions, to quantify their ability to create local scours and based on that to evaluate habitat suitability as deep pool habitats but also to asses potential increase of flood risk in the areas of intervention. The results show that all investigated measures were able to meet the target values of the necessary water depth and area requirements recommended from fish biological studies. The backwater rise and associated increase of flood risk due to the in-stream measures were also quantified showing that these need to be considered in the planning of river restoration projects.

Assessing Nitrate Leaching During Drought and Extreme Precipitation: Exploring Deep Vadose‐Zone Monitoring, Groundwater Observations, and Field Mass Balance

AbstractThe increasing concern over agricultural practices' impact on groundwater quality necessitates comprehensive studies to evaluate and compare monitoring strategies for nitrate leaching. This work addresses this imperative by examining three methodologies: deep vadose‐zone monitoring, shallow groundwater intensive monitoring, and field‐level mass balance. The primary objective of the study was to assess nitrate leaching from an intensively cropped processing tomato rotation field using three different methods. Additionally, this study focuses on contrasting conditions between the growing season (characterized by drought in some years) and the winter/rainy season (characterized by extreme precipitation in some years). Results indicate varying degrees of nitrate leaching across methods, with all approaches detecting leaching events during the growing season and off‐season precipitation. Despite uncertainties inherent in field‐level mass balance estimates, they align reasonably with intensive in‐situ monitoring results using the deep Vadose Monitoring System (VMS). Throughout two growing seasons and corresponding fall‐winter rainy periods, the VMS effectively tracked seasonal nitrogen leaching below the root zone, correlating with observed groundwater nitrate concentrations increases following extreme precipitation events. Nitrate leaching increased during heavy rainfall in the winter following dry summer periods observed across the deep vadose zone using two VMS systems. This underscores the importance of continuous monitoring and assessment in understanding nitrate dynamics and groundwater contamination risks. In conclusion, this study contributes to knowledge and ongoing research by providing insights into effective monitoring strategies for nitrate leaching into groundwater from intensive cropping systems.

Seasonal Variability and Hydrological Patterns Influence the Long-Term Trends of Nutrient Loads in the River Po

This study investigates the long-term trends (1992–2022) of nitrogen and phosphorus loadings exported by the River Po to the Adriatic Sea, to better analyse how changes in hydrology are affecting the timing and magnitude of river nutrient loads. We used 30 years of monitoring data in order to (a) identify the main temporal patterns and their interactions at a decadal, annual and seasonal scale, (b) estimate precipitation effects on load formation and evaluate whether and to which extent the hydrological regime affects nutrient export across the years and (c) analyse the nutrient export regime at a monthly scale and the main transport dynamic of N and P chemical species (hydrological vs. biogeochemical control). The long-term analysis shows a general decrease of both P and N loadings, but the trends are different between the elements and their chemical species, as well as undergoing different seasonal variations. We found a statistically significant relationships between precipitation and loads, which demonstrates that precipitation patterns drive the exported load at the intra- and interannual time scales considered in this study. Precipitation-induced load trends trigger seasonal changes in nutrient deliveries to the sea, peaking in spring and autumn. The nitrogen decrease is mainly concentrated in the summer dry period, while total phosphorus diminishes mainly in spring and autumn. This mismatch of N and P results in variable molar N:P ratios within the year. The effects of extreme drought and flood events, along with the progressive decrease in the snowmelt contribution to water fluxes, are expected to exacerbate the variability in the N and P loadings, which in turn is expected to perturbate the biodiversity, food webs and trophic state of the Northern Adriatic Sea.

Reconstruction of July-September Standardized Precipitation-Evapotranspiration Index (SPEI) for the Hindu Kush region of Northern Pakistan

Abstract The Prolonged drought resulting from global warming is considered an important factor affecting the Asia's socioeconomic growth of West Asia, with a significant impact on the dynamic forecasting of water supply and forest ecosystems. In such a scenario, Understanding future long-term drought (SPEI) changes is crucial for accurately forecasting regional drought shifts in the Hindukush region. In this study, a 517-year (1506-2022 CE) long tree-ring width chronology of the Himalayan Cedar (Cedrus deodara D. Don) from the eastern Hindukush has been developed. The July-September SPEI has revealed a positive and significant relationship (r = 0.633, p < 0.001) with tree growth, which leads to SPEI reconstruction from AD 1626 in the Hindu Kush Region. Our reconstruction model has explained 40.01% of the climate variance during the instrumental period from AD 1965 to 2018. Fourteen wet periods (≥ 3 years) were observed before the instrumental period, specifically in C.E. 1629–1635, 1638–1658, 1666–1674, 1680–1701, 1715–1724, 1770–1776, 1794–1797, 1802–1810, 1822–1846, 1850–1857, 1872–1881, 1883–1890, 1906–1914, and 1921–1937. Similarly, twelve dry summer periods were also observed in the past 339 years, such as C.E. 1659–1665, 1675–1679, 1702–1714, 1725–1769, 1777–1793, 1798–1801, 1811–1821, 1847–1849, 1858–1871, 1891–1905, 1915–1920, and 1938–1963. Nevertheless, AD 1663 was individually the wettest (with a value of 2.13), while AD 1754 was the driest (-0.99) year. The spatial correlation analysis and its comparisons with Karakoram-Himalayan drought and precipitation reconstructions have convincingly confirmed the reliability of our SPEI reconstruction. Consequently, this reconstruction can effectively serve as a proxy for large-scale drought variability in the Hindu Kush region of northern Pakistan. Our findings strongly suggest the considerable dendrochronological potential for further climatological studies in the western Hindu Kush Mountains System.

Eco-physiological behaviors of some apple genotypes (Malus x domestica Borkh.) in the hot-and-dry climate of an inner area of Southern Italy

The Italian internal areas are distant from the main trade flows and service centers, but have important environmental and cultural resources. The Italian “National Strategy for Inner Areas” represents a novel policy aimed at contrast the abandon of these territories by supporting multiple activities aimed at stimulating economic development and promoting territorial cohesion. The condition of marginality offers the chance to pursue economic development according to the principles of sustainability. These internal areas are often distinguished by a purely rural vocation. Genotypes of fruit crops traditionally grown in inland areas cope often with difficult climatic conditions and low-input farming techniques, showing generally a good tolerance to abiotic tresses. Exploring their eco-physiological behaviors in response to the agri-environmental context is useful for identifying crops capable of stimulating the recovery and expansion of a sustainable agriculture system in inland areas. The present work reports some results of a research conducted on three traditional local apple genotypes grown in an internal hot-arid summer area of Southern Italy, evaluating their water status and the intensity of leaf gas exchange compared to those of a well-known “standard” cultivar, in a hot, dry summer period. The local genotypes tested in this case study proved to be more eco-physiologically performing. The experiment allowed to estimate their probable relative eco-physiological advantages compared to the “standard” apple genotype taken as reference.

Does lower water availability limit stem CO2 efflux of oak and hornbeam coppices?

Recent changes in water availability can be crucial for the development, growth and carbon budget of forests. Therefore, our aim was to determine the effect of reduced throughfall and severe summer drought on stem CO2 efflux as a function of temperature and stem increment. Stem CO2 efflux was measured using the chamber method on oak and hornbeam under four treatments: coppice, thinned coppice, and both coppice and thinned coppice with 30 %-reduced throughfall. The first year of the experiment had favourable soil water availability and the second year was characterized by a dry summer. While reduced throughfall had no effect on stem CO2 efflux, the summer drought decreased efflux by 43-81 % during July and August. The stem CO2 efflux was reduced less severely (by 13-40 %) in September when the drought persisted but the stem increment was already negligible. The stem increment was also strongly affected by the drought, which was reflected in its paired relationship with stem CO2 efflux over the two experimental years. The study showed that summer dry periods significantly and rapidly reduce stem CO2 efflux, whereas a constant 30 % rainfall reduction needs probably a longer time to affect stem properties, and indirectly stem CO2 efflux.

Factors influencing migration of short-finned eels (Anguilla australis) over 3 years from a wetland system, Lake Condah, south-east Australia, downstream to the sea.

Anguillid eel populations are under threat globally. A particularly vulnerable life-cycle stage is the migration of mature adult eels downstream from freshwater habitats through estuaries into the sea to spawn. This study investigated the factors associated with downstream migration of the short-finned eel Anguilla australis (Richardson 1841) from a coastal wetland (Lake Condah) in south-east Australia, using acoustic telemetry. Migration was associated with time of the year, higher water level and river flows, decreasing water temperature, and darker moon phases. Larger individuals and those in better condition were more likely to migrate from the wetland. Downstream migration peaked in spring, in contrast to the typical autumn migration period for other temperate anguillids. Variable responses, in comparison to other studies, highlight how migration cues may not be universal. In south-east Australia, short-finned eels may have evolved to migrate in multiple phases by first migrating to the estuary during typical seasonal spring flow pulses (e.g., to avoid being stranded in upland reaches during dry summer periods) and then migrating into the ocean in autumn. More research is needed to unravel these processes and causes, especially considering that the relationship between migration and hydrology may be complex and confounded (e.g., by human-induced disruptions to migratory pathways).

Microbial and thermal indices of organic matter stability in lowland soils with variable texture

Soil organic carbon (SOC) stabilization and turnover are important processes of global carbon cycle. This study evaluates microbial activity and thermal stability of soil organic matter (SOM) in lowland soils of central Europe during relatively dry summer period. We observed that the intensity of soil respiration and substrate availability are positively affected by soil moisture. Soil water availability was correlated with clay content that supported water retention and capillary elevation from the subsurface. Besides moisture, soil respiration was partially controlled also by nutrient availability (Ca, Mg, K, P). Microbial C content was not correlated with any of the properties that were measured. To assess SOM stability, we used thermogravimetry combined with differential scanning calorimetry (TG-DSC). Correlations between TG-DSC data and soil respiration indicate that heterotrophic microorganisms degrade SOM without significant preference for either labile, intermediate, or stable organic fraction. The heat released per mass unit of labile SOM correlated positively with the ratio of microbial vs. total organic C in the sample. This suggests that the energy density of labile OM affects positively the C amount that is converted to microbial biomass. More heat was released per mass of labile OM from the samples that showed higher SOC/SOM ratio and organic C/O value. This indicates that higher portion of C bound in SOM affects positively the energy density of labile fraction. The samples with higher clay content released relatively more heat at higher temperatures in comparison to more coarse-textured soils. Considering the effect of clay on SOC stabilization, the findings of this study pointed on the two contradicting aspects. Although the results suggest that interaction of OM with inorganic clay components results in formation of stable C fraction, fine-textured soils showed higher respiration rate, during the drier period, due to the higher water availability.

Legume yield and persistence when sown in grass and herb pasture mixes in Lees Valley, South Island High Country

Four experiments were established to identify suitable companion species for legumes grown in the intermontane Basin of the Lees Valley, North Canterbury (400 m a.s.l.). This location experiences long cold winters, has soils of low pH and high aluminium, with low water holding capacity and severe summer soil moisture deficits.
 In Year 1, the ryegrass mixtures yielded 4550±290 kg DM/ha more (P<0.05) than the timothy mixtures (3440 kg DM/ha) and the dryland mixture total yield was 4370 kg. The average white clover yield of 1800±210 kg DM/ha was not different among all treatments and represented 43% of total DM, compared with only 8% for sub clover.
 Total yield in Year 2 was higher (P<0.05) in the dryland- and ryegrass-based mixtures (~4400±330 kg DM/ha) than timothy (2650 kg). White clover yield across the mixtures was 930±90 kg DM/ha and 29% of the total DM. Sub clover did not re-establish.
 White clover yields peaked in October-November of both years with growth rates of ~16 kg DM/ha/d. The start of the summer dry period, from late September onwards, resulted in a decline in white clover spring growth rates and lower yields.
 In the Caucasian-herbs experiment, yield in Years 1 and 2 were 2700±250 and 2830±230 kg DM/ha/yr respectively. In both years Caucasian clover yields were lower when grown in herb-based mixtures compared with a monoculture (Year 1: ~400 versus 1800±270 kg DM/ha, Year 2: 920 versus 1750±210 kg DM/ha). The herb content of the mixtures declined over time.

A Large-Diameter Earth–Air Heat Exchanger (EAHX) Built for Standalone Office Room Cooling: Monitoring Results for Hot and Dry Summer Conditions

Earth–air heat exchangers (EAHX) use the soil thermal capacity to dampen the amplitude of outdoor air temperature oscillations. This effect can be used in hot and dry climates for room cooling, and depending on the EAHX design, this cooling can be achieved with very few resources other than those used during EAHX construction. This is an obvious advantage compared to the significant energy consumption and operational costs of refrigeration machines traditionally used in room cooling. Despite the large number of papers on EAHXs available in the scientific literature, very few deal with large-diameter EAHXs (with pipe diameters larger than 0.30 m), and even fewer present monitoring data gathered from a built and functional large-diameter EAHX. The present paper uses monitoring data and provides a detailed quantitative analysis of the performance of a large-diameter EAHX built for standalone cooling of an existing office building. The field monitoring was carried out during a characteristic hot and dry summer period of the south of Portugal. Results show that outdoor air to EAHX exit air temperature gradients reach 9 K and cooling capacities exceed 27 kW. Moreover, the studied EAHX is capable of standalone cooling for outdoor air temperatures up to 33 °C and meets more than 50% of the room design cooling demand for outdoor air temperatures as high as 37 °C. This evidences that large-diameter EAHXs have the potential to achieve significant reductions in CO2 emissions and in energy consumption associated with building cooling in hot and dry climates.

Estimation of Heterotrophic Soil Respiration Response to the Summer Precipitation Regime and Different Depths of Snow Cover in a Temperate Continental Climate

Regime of precipitation and temperature conditions are key factors that regulate the rate of decomposition of soil organic matter in terrestrial ecosystems. The aim of this work was to assess the effect of the duration of dry periods in summer and different depths of snow cover in winter on heterotrophic soil respiration. The studies were carried out as part of a 2–year field manipulation experiment organized on gray soil (Haplic Luvisol) in the temperate continental climate conditions (southern Moscow region). Three variants were organized: (1) simulation of mild weather with uniform watering of the soil in summer and the absence of freezing in winter, (2) simulating two summer dry periods lasting 1–2 months with natural winter snow cover, (3) simulation of extreme weather with one long (~3 months) dry period in summer and complete removal of snow cover in winter. Heterotrophic soil respiration was measured by the closed chamber method on bare fallow during 2 years of continuous experiment and 1 more year after its completion. Medians of heterotrophic soil respiration for the entire period of the experiment in the three above–mentioned variants of the experiment were 38, 27 and 19 mg C/(m2 h), respectively. Two short dry periods led to an increase in heterotrophic soil respiration by 7–10%, which is associated both with the drying and rewetting cycles of the soil and with an increase in the average summer temperature of a 20–cm soil profile by 1.5°C. The prolonged dry period caused a decrease in heterotrophic soil respiration by 12–16% as a result of low soil moisture. Soil freezing led to a strong decrease in winter CO2 emission from soil, which reached 34–55% in the control variant and 57–72% when the snow cover was removed. The frost period (November–March) contributed from 25–34% without of soil freezing to 14–19% when its presence to the annual CO2 flux. We conclude that the change in the winter temperature regime of the soil due to manipulations with the snow depth led to a more significant change in the annual heterotrophic soil respiration than the lack of precipitations in the summer season.

Assessing carbon and water fluxes in a mixed Mediterranean protected forest under climate change: An integrated bottom – up and top – down approach

This paper proposes a framework based on the integration of bottom-up and top-down approaches to assess and quantify the effect of local climate change on carbon and water fluxes in a protected Mediterranean mixed forest. The forest, with an extent of 50 ha, is in a coastal zone and is in decline because of severe summer drought stress. Since 2018, it has been involved in the LIFE PRIMED ecological restoration project.The bottom-up approach used gas exchange measurements and the MOCA model (MOdelling for Carbon Assessment) to quantify photosynthesis and transpiration of the main species in the forest (P. latifolia, P. lentiscus, Q. cerris, and F. angustifolia sub. oxycarpa). The top-down approach used the satellite models C-fix and NDVI-CWS, to quantify and spatialise gross primary production (GPP), net primary production (NPP), and evapotranspiration (ETA) at the forest stand scale. The up-scaling process from leaf to forest stand was made possible by calibrating two key parameters: light use efficiency (ε) and vegetation transpiration coefficient (Kcveg).The results indicate a decline in GPP, NPP, and ETA during the study period (2018–2022) due to the summer drought conditions caused by rising temperatures (16.60 °C in 2018 vs. 16.98 °C in 2022), increased vapor pressure deficit, reduced soil water content, and rainfall (1328 mm in 2018 vs. 468 mm in 2022). In 2018, the annual GPP was 1186.83 ± 351.40 gC/m2y, which decreased to 1128.67 ± 331.21 gC/m2y in 2022. During the dry summer period, GPP ranged from 401.76 ± 119.54 gC/m2y in 2018 to 347.39 ± 101.62 gC/m2y in 2022. Annual ETA rates varied between 1184.86 ± 351.86 mmH₂O/m2y (2018) and 1304.92 ± 384.07 mmH₂O/m2y (2022). The summer ETA rates were significantly influenced by drought conditions, decreasing from 638.73 ± 190.67 mmH₂O/m2y in 2018 to 390.35 ± 108.83 mmH₂O/m2y in 2022.Based on the observed trend in other Mediterranean areas, species-specific responsiveness to local climate change suggests that P. latifolia and P. lentiscus, which are better adapted to water-limited environments, could gradually replace Q. cerris and F. angustifolia subs. oxycarpa.This study provides useful quantitative indications for the management and restoration goals of the area and suggests a methodology that can be applicable in several management practices, particularly for small heterogeneous and fragmented forested areas such as the Mediterranean ones.

Floral Aroma and Pollinator Relationships in Two Sympatric Late-Summer-Flowering Mediterranean Asparagus Species.

This research delves into plant-pollinator relationships within the Mediterranean region, focusing on two synchronous and sympatric asparagus species: A. acutifolius and A. albus. For the first time, the floral scents of the genus Asparagus are reported. We investigate the volatile organic compounds (VOCs) present in their floral scents and their impact on pollinator attraction. Captured flower-emitted VOCs underwent solid-phase microextraction of headspace (SPME-HS) and gas chromatography and mass spectrometry (GC-MS) analysis. The investigation confirms distinctive aroma profiles for each species. A. albus predominantly emits benzene derivatives and sesquiterpenes, while A. acutifolius is characterized by carotenoid derivatives, monoterpenes, and sesquiterpenes. The only shared compounds between the two species are the sesquiterpenes (Z,E)-α-farnesene and (E,E)-α-farnesene. A positive correlation links peak floral aroma intensity (benzenoids in A. albus and ionones in A. acutifolius) with a higher pollinator visit frequency, emphasizing the critical role of intense floral scents in pollinator attraction. The study of reproductive aspects reveals almost complete gynodioecy in A. acutifolius, influencing unique dynamics for the two species. These adaptations hold significant importance within the Mediterranean ecosystem, particularly during the late dry summer period, when a limited number of plant species vie for a shared primary pollinator.

Soil Erosion in Extensive versus Intensive Land Uses in Areas Sensitive to Desertification: A Case Study in Beira Baixa, Portugal

The occurrence of long periods of drought followed by extreme episodes of rainfall and ineffective soil conservation practices are the main causes of soil erosion in the Mediterranean region. The objective of this paper is to assess and compare the hydrological and erosional responses related to land use changes in agricultural landscapes that are sensitive to erosion and that are a result of the significant replacement of traditional land uses. Such changes are characterized by the replacement of extensive olive groves associated with pastureland by intensive almond production, where deep plowing and heavy machinery are required. In each sampling site, runoff initiation, runoff coefficient, and soil loss were evaluated under simulated rainfall (55 mm h−1), at plot scale (0.25 m2), at the end of the hot and dry summer period. Slope gradient, soil texture, bulk density, soil organic matter content, soil water content, and plant cover were also determined. The results showed the impact of recently planted intensive almond orchards (IAOs) on accelerating soil erosion risk compared with the extensive traditional olive groves (EOGs), although runoff initiation and discharge are very similar between the studied land uses. The mean values recorded for soil loss and sediment concentration were 118 g m−2 h−1 and 12 g m−2 h−1 and 3.1 g L−1 and 0.7 g L−1, respectively, for IAOs and EOGs. Our results also demonstrated that maintaining a vegetation cover is a determining factor for the prevention and control of soil erosion, especially in IAOs, where retaining high percentages of natural plant-residue mulch layers (>70%) reduced soil loss by about 70% in this study.

Изменчивость биохимических признаков Pinus sylvestris (Pinaceae) при адаптации форм в условиях избыточного увлажнения

Conifers are characterized by a certain degree of individual variability in the content of stress metabolites, which can be caused by genotypic variations or divergence in the growth conditions of individual trees. The purpose of the study is to evaluate the variation of biochemical traits of Scots pine, which are different in the color of male strobilus, during adaptation to the conditions of constant excessive moisture in the soil of the northern taiga. The dynamics of metabolic parameters of Pinus sylvestris L. were investigated in shrubsphagnum pine stands on marshy upland soils at the mouth of the Northern Dvina River (northern taiga subzone). From July to November 2018, needle samples from shoots were collected from 10 pine trees of each of the male strobilus types, differentiated by color. The contents of photosynthetic pigments, anthocyanins, ascorbic acid, proline, water-soluble proteins, and pH were measured under laboratory conditions. The synthesis of chlorophyll in the needles in the current year of formation decreased in trees of both forms during the dry summer period. A favorable temperature in the autumn period could promote an extension of photosynthetic pigment accumulation, which might negatively affect tree preparation for overwintering. There were no significant differences between f. erythranthera Sanio and f. sulfuranthera Kozubow in the needle content of chlorophyll and carotenoids, anthocyanins, ascorbic acid, free proline, water-soluble proteins, or pH. The similarities in the adaptation of the trees to the constant excessive soil moisture in northern taiga conditions were revealed. The seasonal factor had a considerable impact on the dynamics of biochemical parameters. Ascorbic acid, proline, and anthocyanin were more actively accumulated in the needles throughout the summer due to the high air temperature, resulting in an increase in antioxidant activity and the development of protective mechanisms aimed at reducing oxidative stress. The increase in water-soluble protein content in needles from October to November is one of the cryoprotective mechanisms of the trees for the winter period. Individual differences in ascorbic acid and proline contents in yellow microspore-bearing pine needles at the establishment of minus temperatures in November were considerably higher than in red microspore-bearing pine needles. This is regarded as the norm of the reaction for different types of trees to the influence of negative temperatures. For citation: Tarkhanov S.N., Pinaevskaya E.A., Aganina Y.E., Pakhov A.S. Variability of Biochemical Properties During Adaptation of Pinus sylvestris (Pinaceae) Forms to Excessive Moisture Conditions. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 58–75. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-58-75

Meteorological Drought Characterization in the Calabria Region (Southern Italy)

Due to the important role of water resources in the growth of the world’s economy, drought causes global concern for its severe worldwide implications on different sectors, such as biodiversity, farming, public water supply, energy, tourism, human health, and ecosystem services. In particular, drought events can have strong environmental and socioeconomic impacts in countries depending on rain-fed agriculture such as the ones in the Mediterranean region, which, due to a detected increase in warming and precipitation decrease, is considered a climate change hotspot. In this context, in this paper, meteorological drought in the Calabria region (southern Italy) has been characterized considering the Standardized Precipitation Index (SPI) evaluated at different timescales. First, the temporal distribution of the most severe dry episodes has been evaluated. Then, a trend analysis has been conducted considering the different seasons, the wet (autumn and winter) and dry (spring and summer) periods, and the annual scale. Finally, the relationship between drought and some teleconnection patterns (the North Atlantic Oscillation—NAO, the El Niño–Southern Oscillation—ENSO, and the Mediterranean Oscillation—MO) has been investigated. Results show that the majority of the severe/extreme drought events have been observed between 1985 and 2008. Moreover, a decrease in SPI values has been observed in winter and spring, in both the wet and dry periods, and upon the annual scale considering the 12-month SPI and the 24-month SPI. Finally, a link between the drought episodes in the Calabria region and the NAO phases and the MO has been identified. Since drought episodes can severely impact water resources and their uses, the findings presented in this work can be useful to plan and manage the water supply for household, farming, and industrial uses.

Urbanization-Induced Diurnal Variation in Short-Duration Rainfall Events in Wuhan, China

Increasing of evidence suggests that rapid urbanization modifies precipitation and increases atmospheric instability in urban areas mainly due to urban heat island (UHI)-induced thermal effects and urban building-induced dynamic effects. However, few studies focus on the impact of urbanization on the diurnal variations in urban rainfall in terms of initiating time, frequency, amount, and intensity. Here, six years of hourly data from a relatively dense meteorological observation network in the Wuhan area in central China are used to quantify the issue of urbanization-induced diurnal variations in hourly rainfall and short-duration rainfall (SDR) events by comparing urban and surrounding rural stations during the summer dry period (13 July to 4 August), corresponding to hot weather with little rainfall and high evaporation. The results indicate that: (i) A higher frequency of hourly rainfall appears during night-time and afternoon over urban areas as compared to rural areas. The urban rainfall is more concentrated during the night-time; (ii) More and stronger urban SDR events are triggered during the night-time over urban areas, especially in terms of amount and intensity of rainfall events. A greater diurnal urban–rural difference in SDR events is detected than that in hourly mean rainfall; (iii) There is an enhancement in the night-time and afternoon urban SDR events when UHI intensity increases before they are initiated, and this is detectable in the frequency, amount, and intensity of SDR events. It is also found that the UHI-induced thermal effects are the main reason for the stronger nocturnal SDR events in Wuhan during the summer dry period, which is caused by increases in the convection current and water vapor flux convergence in the urban areas.

Influence of Critical Zone Architecture and Snowpack on Streamflow Generation Processes: A Mountain‐Meadow Headwater System in a Mediterranean Climate

AbstractObservations from a granitic watershed within a Mediterranean climate reveal the hydrologic and critical zone functioning of a perennial stream headwater and its upslope contributing area within a meadow system in the Sierra Nevada, California. Chemical analysis (diagnostic tools of mixing models, end member mixing analysis, tritium, etc.) and physical data (stream stage, piezometers, soil water, snowpack, etc.) indicate there are two primary pathways of water input into a headwater stream sourced from a mountain meadow. One input is a shallower and younger subsurface pathway with water that resembles snowpack chemistry, and the other a deeper and older subsurface pathway with water that reflects the chemistry of the groundwater derived from the contributing hillslopes. Multi‐year observations reveal that regardless of snowpack amount, during the period of peak hillslope infiltration, shallow and deep pathways in the hillslope behave similarly to initiate headwater streams. However, during summer dry periods, similarities in active pathways within the meadow center are not maintained between high and low snowpack years. With less snow, perennial groundwater discharge within the meadow center is eliminated, becoming only a seasonal source at the meadow's outlet. At the meadow's edge, geophysically observed downslope thinning in saprolite thickness creates reduced lateral transmissivity and initiation points for headwater streams via enhanced groundwater discharge of upslope water. Combined, these findings suggest how loss of snowpack and critical zone structure can together mediate hydrologic function in a wet meadow system in a Mediterranean climate. Creating new understanding about the stability of hydraulic functioning in headwater wet‐meadow systems under a changing climate.

Microclimatic buffering in forest, agricultural, and urban landscapes through the lens of a grass‐feeding insect

AbstractFor small ectotherm species, dealing with microclimatic variation during sensitive stages of their development is a critical component of their ecological interactions within and among different landscape settings. However, it is often unknown whether the use of habitats in different landscape settings may affect microclimatic conditions at the level of microhabitats (e.g., at host plants for herbivorous insects). As opposed to standard ecological monitoring experiments, we aim to identify the microclimatic variables that accurately represent the environment in which a small arthropod spends most of its life. As a case study, we selected grassy sites that corresponded to the microhabitat of grass‐feeding insects in general, and larvae of the butterfly Pararge aegeria in particular, as this insect recently expanded its habitat use from forest (edges) to agricultural and urban environments. We tested the extent to which local microclimates and microclimatic buffering capacity differed between tufts of grass in forest and in two anthropogenic (i.e., agricultural and urban) landscape settings by measuring microclimatic variables with sensors at the level of the grasses. We compared temperature, relative humidity, and vapor pressure deficit (VPD) during an exceptionally warm and dry summer period with parallel data from weather stations and tested for differences between microclimatic profiles among the three landscape settings. Microclimatic conditions correspond only partly to variables based on weather station data. Differences are particularly significant for relative humidity and VPD, but not for day and night temperatures. Effects of canopy openness on the variability of microclimatic variables are landscape‐specific. Host plants in agricultural settings experience strong microclimatic fluctuations and low short‐term variability in VPD. In urban settings, urban heat island effects increase night temperature but also show microclimatic buffering effects similar to the ones in forest settings. Our findings stress the functional implications of landscape‐specific microclimatic profiles at the appropriate organism‐centered scale. We discuss the significance of such microclimatic profiles for ecological studies dealing with ectotherms under climate and land use change.