July Temperature Research Articles

Influence of terrain and atmospheric boundary layer on the ventilation and thermal comfort performance of windcatchers

Windcatchers are a promising natural ventilation alternative to conventional ventilation systems. In recent years, many studies attempted to address the different gaps in the field but the impact of terrain type on the performance of windcatchers is still an unexplored topic. Therefore, this paper investigates how the windcatcher's ventilation performance and thermal comfort are affected by different types of terrain and atmospheric boundary layer (ABL) profiles. To reach this goal, numerical simulations were employed and validated against experimental data. The performance was assessed in four terrain types (open, rough, suburban and urban) and two thermal scenarios (outdoor temperatures of 21.5 °C as the Nottingham's average maximum daily temperature for July and 26 °C as the summer design temperature). As the terrain changes from a more uniform open countryside to a less uniform urban region, the induced flow rate decreases from 1040 L/s to 690 L/s, which still surpasses the values of 160 L/s and 94 L/s recommended by the CIBSE and ASHRAE 62.1 standards. The maximum mean age of air (MAA) at the breathing height of a seated person reaches the value of 173 s and 190 s for suburban and urban regions while it does not exceed 140 s for open and rough country. Thermal comfort was assessed based on PMV and the adaptive model. The results showed that in the 1st thermal scenario (at an outdoor temperature of 21.5 °C), all terrains are within the adaptive comfort band. However, PMV was out of the comfort range in nearly 50% of the seated head height plane. However, in 2nd scenario (outdoor temperature of 26 °C), all terrains failed to provide comfort. Furthermore, the urban cases showed higher temperatures and PMV in both scenarios.

Macroinvertebrate assemblages downstream of dams show no sign of impairment despite flow regulation and thermal alteration

Flow regulation by dams produced downstream effects, including geomorphological, hydrological and thermal alterations. We aimed to analyse the alterations of the thermal regime caused by hypolimnetic releases of regulated flow compared to the unregulated thermal regime, and the effects of both thermal and flow regime alterations on macroinvertebrate communities. Stream temperature was monitored over three-years in three rivers with contrasting flow regimes, all located in the Mediterranean ecoregion. Results show that regulated rivers present an inverted flow regime with high discharges in summer, colder water from February to September arising maximum differences of 7.4 °C in July and presenting a delayed thermal maximum of 2 to 2.5 months compared with the unregulated river. Given the relevant hydrological and thermal alterations found in both regulated rivers, unexpectedly no differences were found between regulated and unregulated rivers when analysing macroinvertebrate richness and diversity indexes. The taxonomic response is significantly different among the three rivers in summer and was mostly explained by summer indicators, with the maximum water temperature of July being present in all models. An indirect driver that exacerbates the thermal differences found between regulated and unregulated rivers would be the geomorphological configuration of the rivers reciprocally interacting with the riparian vegetation. The monitoring of stream temperature is a crucial activity needed to implement since this parameter together with water flow shapes the distribution of aquatic biota in river ecosystems.

Resiliency of Apache Trout habitats in a warmer and drier climate future

AbstractObjectiveThe Southwest has the hottest and driest climate in the United States, and projections show that it will only get hotter and drier into the 2100s. The Apache Trout Oncorhynchus apache is native to the Southwest and is currently listed as threatened under the U.S. Endangered Species Act. Our goals were to understand how climate factors influence the distribution of juvenile Apache Trout (<125 mm TL) and how climate change will influence the suitability of Apache Trout habitat into the 2080s.MethodsWe used a species distribution model to evaluate how climatic and other factors influence the distribution of juvenile Apache Trout. We used predictions from the model to evaluate how climate change might impact the suitability of streams designated for recovery of the species into the 2080s.ResultJuvenile Apache Trout occurrence was predicted well by mean July stream temperature (°C), mean annual precipitation (dm), stream slope (%), and the presence of nonnative trout (area under the receiver operating characteristic curve = 0.85). Standardized parameter estimates showed that Rainbow Trout O. mykiss presence and annual precipitation influenced occupancy the most. Model predictions for the 2080s showed suitable habitat (occurrence probability ≥ 0.25) to increase for 11 (of 45) Apache Trout streams in the increased temperature (+3°C) only scenario (scenario 1), as headwater reaches that are currently too cold warmed to become more suitable. When we also included projected declines in annual precipitation (−5%) for the 2080s (scenario 2), the amount of suitable habitat decreased for eight Apache Trout streams and remained unchanged in all other streams.ConclusionMost Apache Trout populations are isolated upstream of barriers to nonnative trout in stream reaches that are currently thermally suitable with respect to mean July temperatures and would remain suitable into the 2080s. Cold headwater reaches are projected to warm, becoming more suitable in the 2080s. Thus, intentional isolation and the resultant truncated downstream distributions of Apache Trout populations in headwater streams explain the nominal effect of projected temperature increases due to climate change on this cold‐adapted salmonid. Standardized model parameters suggest that future declines in precipitation, manifested through reduced snowpack and its influence on streamflows, will play a larger role than temperature in the suitability—and, thus, resiliency—of Apache Trout habitats at least into the 2080s.

Reconstructed Malacothermometer July Paleotemperatures from the Last Nine Glacials over the South-Eastern Carpathian Basin (Serbia)

In this study, the compiled malacological record of the two most important loess–palaeosol sequences (LPS) in Serbia was used to reconstruct the Malacothermometer July Paleotemperature (MTJP) of the last nine glacials. The sieved loess samples yielded shells of 11 terrestrial gastropod species that were used to estimate the MTJP. Veliki Surduk (covering the last three glacial cycles) and Stari Slankamen (covering the last fourth to ninth glacial cycle) LPSs previously lacked the malacological investigations. After the sieving, a total of 66,871 shells were found, from which 48,459 shells were used for the estimation of the MTJP. Through the studied period, the reconstructed MTJP was ranging from 14.4 °C to 21.5 °C. The lowest temperature was recorded during the formation of the loess unit L5, equivalent to the Marine Isotope Stage (MIS) 12. The second-coldest summers were occurring during the MIS 16 glacial. Although the warmest glacial was L8 (MIS 20) according to MTJP, these July temperatures might be overestimated due to only two samples from the poorly preserved L8 unit. The malacological material derived from the loess units at Veliki Surduk and Stari Slankamen LPSs showed great potential for July temperature reconstruction, as the comparison with other regional records showed similar climate changes. Further work is necessary to validate the age scale of the oldest samples, and a higher resolution sampling could lead to more detailed July temperature fluctuations, as was shown for the youngest glacial in this study. Likewise, estimating the July temperature using different proxies (e.g., pollen) from the same LPSs could be used to confirm the observed climate trends.

Preboreal oscillation in the light of multiproxy analyses—Early Holocene in Lake Jelonek (North Poland)

In this work, we studied the course of climatic fluctuations at the beginning of the Preboreal period using multiproxy analyses (Chironomidae, pollen, diatoms, Cladocera, stable isotopes, macrocharcoal, microlithofacial) combined with varve chronology of sediments. The results showed a decrease in the mean July temperature and stronger continentalism followed by climate wetting at the start of the Preboreal period. This was reflected in the remodeling of the vegetation cover from birch forests to more open spaces with grass vegetation dominance, as well as that of the species composition of Cladocera and diatoms, and the high variability of isotopic composition. In addition, the results showed the impact of local conditions (fires and relict permafrost) on the amplification of environmental responses due to climate cooling. The environmental transformations presented here correspond temporally to the changes that are well documented in other parts of Europe as the Preboreal Oscillation.

ИЗМЕНЕНИЕ ТЕРМИЧЕСКИХ РЕСУРСОВ ВЕГЕТАЦИОННОГО ПЕРИОДА И УРОЖАЙНОСТЬ ЯРОВОЙ ПШЕНИЦЫ В УСЛОВИЯХ СРЕДНЕГО ПОВОЛЖЬЯ

The article presents the results of long-term studies (1982-2018) on the assessment of changes in thermal resources during the growing season and the indication of their impact on the yield of spring wheat. The work was carried out in the conditions of the northern part of the Middle Volga region on gray forest soils. The soil of the experimental site is gray forest medium loamy, the content of humus (according to Tyurin) is 2.8...3.2%, mobile phosphorus and potassium (according to Kirsanov) - 105...184 and 79...149 mg /100 g of soil, respectively, pH- 5.6...5.8. During the observation period, the highest temperature increase was recorded in July (2.4°C) and May (2.2°C), and the lowest in June (1.0°C). The sum of effective temperatures over 10°C increased by 500°C during the study period. The yield of spring wheat grown without fertilizers varied greatly in different years, ranging from 0.99 to 2.97 t/ha. The highest value of this indicator was observed at an average monthly air temperature of about 13 0C in May, 17 0C in June, 18 0c in July, and the sum of active temperatures was 1800 0c. The studied thermal resources, in accordance with the significance of the impact on the yield of spring wheat, can be arranged in the following descending order: average air temperature in June > average air temperature in July > the sum of effective temperatures above 10 °C > average air temperature in May. To describe the dependence of the yield of spring wheat grain on thermal resources, in three cases out of four, a polynomial equation of the second degree was better suited, and in one case, an exponential equation.

Explanatory models for tick-borne disease incidence (Astrakhan rickettsial fever and Crimean-Congo hemorrhagic fever)

Introduction. The study focuses on methods providing mathematical substantiation of discrepancies between actual incidence rates of Astrakhan rickettsial fever (ARF) and Crimean-Congo hemorrhagic fever (CCHF) and predicted rates due to the indirect impact of weather conditions during the current epidemic season.
 The purpose of the study was to develop explanatory models for ARF and CCHF incidence using satellite monitoring (remote sensing) data and to present the results of their practical evaluation in the Stavropol Territory and Astrakhan Region.
 Materials and methods. The materials included climate data provided by the Space Research Institute of the Russian Academy of Sciences as well as epidemiological data on CCHF and ARF incidence from 2005 to 2021. The explanatory models incorporated the Bayes theorem and Wald sequential analysis. All the calculations were completed using the Microsoft Excel 2010-based program developed by the authors.
 Results. It has been found that the greatest indirect effect on development of the CCHF epidemiological situation is produced by the normalized difference vegetation index and relative air humidity in June-July in the Stavropol Territory and by the maximum, minimum and average air temperature in October as well as the minimum air temperature in July in the Astrakhan Region. ARF incidence rates depend on the indirect effect of the annual average and average annual maximum temperature, maximum temperature and the normalized difference vegetation index in April-July. The match between explanatory model-based results and prediction model-based results ranged within 46.2-100%.
 Discussion. In addition to projecting incidence rates, which could be reached with the observed values of climatic factors in the current year, the explanatory models can be used for indirect verification of prediction models and for identification of factors causing differences in results.
 Conclusion. The practical evaluation of explanatory models confirms the prospects and benefits of the study that should be continued, involving other regions highly endemic for tick-borne infections.

Climate response of Picea schrenkiana based on tree-ring width and maximum density

The effect of global warming on alpine forests is complex. It is crucial, therefore, to investigate the effects of climate change on the radial growth of trees at different altitudes. The tree growth–climate relationship remains poorly understood at large spatial scales in the Tianshan Mountains, China. Schrenk spruce (P. schrenkiana) is a unique tree species to this area. In this study, we collected tree-ring width and maximum density data from nine plots along an altitudinal gradient. Results showed that altitude affected both tree-ring width and maximum density. At high altitudes, tree-ring width was positively correlated with temperature in February of the current year. Tree-ring width was also positively correlated with precipitation in July of the previous year, and January and July of the current year, and negatively correlated with the monthly diurnal temperature range (DTR). At low altitudes, tree-ring width was negatively correlated with temperature in the early growing season and the growing season. Tree-ring width was positively correlated with precipitation in June and September of the previous year, and May of the current year. The tree-ring maximum density was positively correlated with temperature and the DTR of the growing season, and negatively correlated with precipitation in winter and growing season. Moving correlation analysis showed that the positive response of tree-ring width to precipitation in the growing season was enhanced over time at high altitudes. In the low-altitude trees, the negative response of tree-ring width to temperature in the growing season was reduced, while the positive response to precipitation in the growing season was enhanced. The positive response relationship between tree-ring maximum density and the temperature in July weakened over time. At low altitudes, the negative response of tree-ring maximum density to winter precipitation was strengthened, and a stable negative response to July precipitation was observed. As the climate becomes wetter and warmer in the Tianshan Mountains, our results suggest that the radial growth of trees may benefit at elevations above 2400 m a.s.l. There was no obvious elevation limit for the increase in tree-ring maximum density. These findings provide a basis for sustainable forest management under global climate change.

Brief Overview of Greek Fir Radial Growth in Response to Climate and European Fir Budworm: Three Case Studies from Giona Mountain, Central Greece

Tree rings provide an invaluable insight into how trees adapt to changes in climate. This study presents aggregated results, from our research on tree rings, climatic response and the insect Choristoneura murinana infestations from three studies on Greek fir, located in stands across Central Greece and Giona Mountain on three different altitudes. In our studies, was found that extreme droughts and wet events had a negative or positive effect on fir growth, respectively. April’s precipitation had a positive correlation with growth for all the stands, which supports other authors’ findings. Moreover, the average maximum temperature of the growing season and the maximum temperature of April, July and August were also linked to growth. Evapotranspiration during the growing season was seen to be inversely proportional to the growth of fir. An apparent decline in tree ring growth more severe in stand 3 (Average Tree Ring Width Index, ARWI < 0.6) has been observed, particularly in recent years. The data suggests that temperature is having a detrimental effect on fir growth in the area, with a significant decreasing tendency in growth from 1993 for the high altitude stands and from 1998 for the lower altitude stand. To ensure successful and sustainable forest management in the future, more research into tree rings and their relationship with climate must be carried out.

Effect of Temperature on Microorganisms and Nitrogen Removal in a Multi-Stage Surface Flow Constructed Wetland

The effect of low temperature on microbial nitrogen metabolism in constructed wetlands has yet to be extensively investigated. In this study, we analyzed the effects of temperature changes on nitrogen-associated microorganisms and nitrogen metabolism functional genes in a multi-stage surface flow constructed wetland (MSSFCW) using metagenomic sequencing. The treatment of polluted river water in the MSSFCW, which had a mean water temperature (MWT) of ≤17 °C, resulted in a low removal efficiency (RE) for total nitrogen (TN; average RE: 23.05% at 1–17 °C) and nitrate nitrogen (NO3−-N; average RE: −2.41% at 1–17 °C). Furthermore, at a MWT of ≤11 °C, the REs were low for ammonium nitrogen (NH4+-N; average RE: 67.92% at 1–11 °C) and for chemical oxygen demand (COD; average RE: 27.45% at 1–11 °C). At 0.24 m3 m−2 d−1 influent load, the highest REs for TN (66.84%), NO3−-N (74.90%), NH4+-N (83.93%), and COD (52.97%) occurred in July and August, when water temperatures were between 26 and 28 °C. The lowest rates (TN: 11.90%, NO3−-N: −21.98%, NH4+-N: 65.47%, COD: 24.14%) occurred in the January–February period, when the water temperature was lowest (1–5 °C). A total of 25 significantly different species were detected in surface sediment, none of which were dominant species. The dominant phyla and genera at low (January) and high (July) temperatures were similar; however, microorganisms were more abundant in the low-temperature months. Our analysis indicated that the same nitrogen metabolism pathways occurred in January and July. Denitrification-associated functional genes were the most abundant; nitrification-related functional genes were the least abundant. Only nirBD displayed significantly different abundances between January and July. This paper can hopefully help researchers and managers further understand how temperature affects nitrogen removal performance in constructed wetlands.

Age matters: Older Alnus viridis ssp. fruticosa are more sensitive to summer temperatures in the Alaskan Arctic

Abstract The Arctic is rapidly warming, and tundra vegetation community composition is changing from small, prostrate shrubs to taller, erect shrubs in some locations. Across much of the Arctic, the sensitivity of shrub secondary growth, as measured by growth ring width, to climate has changed with increased warming, but it is not fully understood how shrub age contributes to shifts in climate sensitivity. We studied Siberian alder, Alnus viridis ssp. fruticosa, a large nitrogen‐fixing shrub that has responded to climate warming with northward range expansion over the last 50 years. We used serial sectioning of 26 individual shrubs and 94 cross‐sections to generate a 98‐year growth ring chronology, including one 142‐year‐old, Siberian alder in Northern Alaska. We tested how secondary growth sensitivity to climate has changed over the past century (1920–2017) and how shrub age affects climate sensitivity of alder growth through time. We found that over time, alder growth as expressed by the stand chronology became more sensitive to July mean monthly air temperature. Older shrubs displayed higher sensitivity to June and July temperature than younger alders. However, during the first 30 years of growth of any shrub, temperature sensitivity did not differ among individuals. In addition, the June temperature sensitivity of growth series from individual cross‐sections depended on the age of the attached shrub. Our results suggest that age contributes to climate sensitivity, likely through modifying internal shrub carbon budgets by changing size and reducing alder's dependence on N‐fixation over time. Older, more sensitive alder may enhance C and N‐cycling while having greater recruitment potential. Linking alder age to climate sensitivity, recruitment and total N‐inputs will enable us to better predict ecosystem carbon and nitrogen cycling in a warmer Arctic. Read the free Plain Language Summary for this article on the Journal blog.

Development and the Effect of Weather and Mineral Fertilization on Grain Yield and Stability of Winter Wheat following Alfalfa—Analysis of Long-Term Field Trial

Within the framework of a long-term experiment, established in 1955, we evaluated the development and effects of weather and mineral fertilization (Control, NPK1, NPK2, NPK3, NPK4) on the yield and stability of winter wheat following alfalfa. In total, 19 seasons were analysed. The weather changed considerably at the experimental site. Significant increases in minimal, mean, and maximal temperatures were dated to the period 1987-1988, while precipitation remained the same to this day (insignificantly increasing trend by 0.5 mm per annum). Rising temperatures in November, May, and July positively affected wheat grain yield, especially in treatments with higher N doses. No relationship between yield and precipitation was recorded. Highest inter-annual yield variability was recorded in Control and NPK4 treatments. Although minerally fertilized treatments provided slightly higher yields, the difference between Control and NPK treatments was insignificant. According to the linear-plateau response model, the recommended dose of 44 kg ha-1 N corresponds with yield of 7.4 t ha-1, while Control provides an average yield of 6.8 t ha-1. The application of higher doses did not lead to significant grain yield increase. Alfalfa as a preceding crop reduces the need of N fertilization and contributes to sustainable conventional agriculture, however, its share in crop rotations is decreasing both in the Czech Republic and in Europe.

Tree rings as an ecological indicator of the reaction of Swiss stone pine (Pinus cembra L.) to climate change and disturbance regime in the extreme environment of cliff forests

Tree rings are an ecological indicator, useful for studying the adaptation of trees in a changing environment, especially in the unique habitat of high-elevation cliff forests. The main aim of this study was to characterize tree-ring changes in Stone pine (Pinus cembra L.) growing in the extreme conditions of cliff forests of the Western Carpathians (at elevation 1300–1600 m a.s.l.), in order to reconstruct the growth release pattern and to better understand the influence of climate. The study was based on 104 tree ring series covering a 449-year-long chronology (1561–2009). In the last century, mean annual temperature has increased by +2.0 °C and precipitation has decreased slightly in the Tatras. The growth of stone pine was strongly related to summer temperature of June and July. In the last decades, the negative influence of summer precipitation on tree growth has abated; this may be related to warmer summers and decreasing precipitation. Temperature of the previous autumn, winter, and early spring, which had a significant influence on stone pine growth in the past, is not an important factor now. In the extreme environment of mountain cliffs, the influence of temperature and precipitation on tree growth is not stable over time under changing climate. The current changes in climate seem to promote stone pine and its potential upward elevational shift. The numerous past disturbance events have affected a limited number of trees, suggesting that single individuals have been randomly eliminated from the cliff stands during the last three centuries. Our results highlight the complex pattern of the reaction of stone pine on cliffs to changes in the environment. Swiss stone pine, a long-lived tree species, shows high adaptability for colonization of mountain cliffs and is an excellent object for studying the response of plants to changing climate. Understanding the effect of interactions between climate, disturbances, and the radial growth of trees in extreme environments of cliff forests on different temporal scales (monthly, seasonal, yearly) should increase our knowledge of such ecologically valuable areas.

The Contribution of Adsorbent Materials (Silica Gel and Sawdust) in Removing Water Vapor; Iraq as a Study Case

This research aims to remove the moisture (latent load) generated by the occupants of the space due to the addition of water vapor resulting from the natural breathing process, the perspiration that evaporates in the air of the space. In sum, the dehumidification system (DS) reduces the amount of latent load or removes it completely to reduce the load on the air conditioner. In this study, adsorbent materials, such as silica gel-Blue and sawdust were used and their effectiveness was compared when used in dehumidification. The results of these experiments for June showed that the adsorption rate and temperature of the blue silica gel - Blue were 20% and 34°C, while the humidity and temperature increased to 52% and 36°C when using sawdust (when rotating the dehumidifying system hourly). Moreover, for July, the adsorption percentages of silica gel-Blue were 8%, while the moisture content of sawdust increased to 49%, while the adsorption percentage in August when using silica gel - Blue was 10% and the relative humidity increased until it reached 39% when using sawdust. While the temperatures in July and August reached their maximum value when using silica gel - Blue and sawdust at 35°C and 36°C, respectively. The water vapor absorption rate in June, July, and August is 83.39 g, 70.82 g, and 65 g, respectively. While the drying process increased during these months due to the increase in solar radiation. Therefore, silica gel - Blue has proven its effectiveness by absorbing moisture more efficiently than sawdust. However, when drying sawdust, it was more effective and faster drying than silica gel - Blue.

Is Aquatic Fern <i>Salvinia natans</i> (Salviniaceae) Rare in Russia?

According to publication and literature, herbarium data, materials of Internet resources, the change in distribution of aquatic fern Salvinia natans (Salviniaceae) on Russian territory was traced since the beginning of XX century until 2021, and the current boundaries of its range were determined. Among the bioclimatic and temperature indicators that determine the distribution of S. natans, the minimum and maximum temperatures in October and January and the maximum temperatures in April and July showed the highest statistical significance, which is associated with important stages of the life cycle of S. natans. Comparison of species localities with climatic and temperature indicators for the time periods of 1960–1969, 2010–2018, 2011–2021 showed that up to 2021 in the European part, West Siberia, and the Far East there was significant spreading of S. natans to the north (more than 200 km). A notable increase in the number of records of the species has been found since the 2000s in different regions. For example, in the Ivanovo Region from 2018 to 2021 their number has increased more than three time. The expansion of the species occurs against the background of a noticeable increase in average annual temperatures and changes in other bioclimatic indicators. If present temperature trends continue, S. natans will expand its range even further north, east, and west in European Russia, north and west in West Siberia and the Far East. Due to the ongoing expansion of S. natans, the premises for the exclusion of the species from a number of regional Red Data Books were discussed.

Bioregionalization of Albania: Mismatch between the flora and the climate suggests that our models of Southern European bioregions are in need of a revision

We analysed the floristic subdivisions of Albania by hierarchical clustering of all the vascular plant species of Albania over a grid of 25 km cells, adapting data from the Vascular Species Distribution Atlas in Albania of ( Barina Z (ed.) (2017) Distribution atlas of vascular plants in Albania. Hungarian Natural History Museum, Budapest). We identified the principal axes of variation of the flora and the bioclimatic variables that explain it. We also analysed the bioclimate of Albania by means of a self-organizing map (SOM) of the main climatic variables and the application of the global bioclimatic model of Rivas-Martínez. We compared the analysis based on the flora with that based on the bioclimate. The results divided Albania into eight floristic units corresponding to the main vegetation types (Carpinus orientalis woodlands, Quercus cerris woodlands, Quercus petraea and Fagus sylvatica woodlands, Quercus coccifera woodlands, Quercus coccifera and Quercus ithaburensis woodlands, Pinus heldreichii woodlands, alpine vegetation of North Albania, and alpine vegetation of eastern Albania). Two main trends of variation can be recognized: four elevational belts, strongly correlated with average July temperature, and a north–south subdivision, weakly correlated with annual rainfall and thermal excursion. The bioclimatic analysis (SOM and Rivas-Martínez model) resolves and adds detail to the axis of the elevational belts but cannot discern the north–south subdivision apart from the high mountains. We obtained a division into eight floristic units ordered according to two gradients: four elevational belts, each in turn subdivided into a north-central and a southern province. These two gradients seem to have a broader meaning in Southern Europe, particularly the north–south subdivision at about 30° latitude. The partial mismatch between the bioclimate and the flora indicates that bioclimatic models of Europe are in need of a revision and suggests that the history, in addition to the present-day climate (for instance, the vegetation of the last glacial maximum), can play a role in shaping the biogeography of Southern Europe.

The Use of Basal Area Increment to Preserve the Multi-Decadal Climatic Signal in Shrub Growth Ring Chronologies: A Case Study of Betula glandulosa in a Rapidly Warming Environment

Climate warming at high latitudes has contributed to the growing interest in shrub tree-ring analysis. Shrub architecture presents new challenges for dendrochronology, such as the seemingly lower and inconsistent climatic sensitivity of stems vs. root collars. Shrub stems may thus be considered as sub-optimal to study climate–growth relationships. In this paper, we propose that the lower climatic sensitivity of stems could be caused by the use of unsuitable detrending methods for chronologies spanning decades rather than centuries. We hypothesize that the conversion of the ring width (RW) to basal area increment (BAI) is better suited than traditional detrending methods to removing age/size-related trends without removing multi-decadal climate signals. Using stem and root collar samples collected from three sites in the forest–tundra ecotone of eastern Canada, we compared the climate–growth relationships of these two approaches for stems and root collars using mixed-effects models. The climate sensitivity was, on average, 4.9 and 2.7 times higher with BAI than with detrended (mean-centered) RW chronologies for stems and root collars, respectively. The climatic drivers of radial growth were identical for stems and root collars when using BAI (July temperature and March precipitation), but were inconsistent when using detrended RW series (root collars: July temperature and March precipitation at all sites; stems: April and June temperature, depending on the site). Although the use of BAI showed promising results for studying long-term climate signals in shrub growth chronologies, further studies focusing on different species and locations are needed before the use of BAI can become broadly used in shrub dendrochronology.

Predicting Habitat and Distribution of an Interior Highlands Regional Endemic Winter Stonefly (Allocapnia mohri) in Arkansas Using Random Forest Models

Stoneflies are a globally threatened aquatic insect order. In Arkansas, a diverse group of winter stonefly (Capniidae: Allocapnia) have not been surveyed since the 1980s, likely because species-level identification requires the rarely-collected adult form. Allocapnia mohri, a regional endemic, was previously commonly found in mountainous, intermittent streams from the Ouachita Mountains ecoregion north to the Ozark Highlands, but no species distributional models including land use or climate variables exist to our knowledge. We collected adults from 71 stream reaches from the historic Arkansas range from November to April 2020 and 2021. We modeled distributions using random forest (RF) models populated with landscape, climate, and both data to determine which were most predictive of species presence. Correlations between landscape or climate variables and presence were examined using multiple logistic regression. The landscape RF models performed better than the climate or landscape + climate RF models. A. mohri presence sites tended to have a greater elevation, a lower mean July temperature, and a greater percentage of very slow infiltration soils in the watershed, compared to absence sites. A. mohri was absent at the Ouachita Mountains sites and may be experiencing a range contraction or migration northward.

Response to drought stress differs among Pinus pinea provenances

Severe drought causes decline in growth and stability of Mediterranean forests because autochthonous species and provenances may reach their drought tolerance limits. Stone pine (Pinus pinea L.), which is one of the primary Mediterranean forest tree species due to its high economic value, has been extremely suffering from drought during the past years. We investigated turgor loss point traits of shoots derived from pressure-volume curves, vulnerability to cavitation of lateral shoots and the physiological response (water potential, photosynthetic activity) to an experimental drought of two-year-old seedlings of seven stone pine provenances native to Turkey with the aim of providing suggestions for selection of provenances for future afforestations. We monitored turgor loss point in the period from June-August and hydraulic vulnerability in July. Water potentials corresponding to 50% conductivity loss (P50) and 25% relative water loss were significantly higher (less negative) in the northern provenances, indicating a higher hydraulic vulnerability to cavitation. Reaction to drought stress varied considerably among provenances. Provenances originating from higher latitudes (more northern regions) had higher relative water content at turgor loss point (RWCTLP) and modulus of elasticity (ε) in August, but also higher midday and pre-dawn water potentials as a result of the experimental drought. RWCTLP and ε in July were negatively related to ME (mean of the maximum temperatures of June, July and August) and positively to the pluviothermic quotient (Q). August RWCTLP was as well lower in provenances from regions with higher ME. Regarding the strategy towards drought, P. pinea provenances ranged from isohydry in the most northern provenance to anisohydry in the most southern provenances. Isohydry is usually related with avoidance of dehydration, while anisohydry is related with tolerance to dehydration and a lower P50. For future reforestation it is suggested to select provenances with a more anisohydric strategy towards drought stress.

Climatic and vegetational controls of Holocene wildfire regimes in the boreal forest of northern Fennoscandia

Abstract Climate change is expected to increase wildfire activity in boreal ecosystems, thus threatening the carbon stocks of these forests, which are currently the largest terrestrial carbon sink in the world. Describing the ecological processes involved in fire regimes in terms of frequency, size, type (surface vs. crown) and severity (biomass burned) would allow better anticipation of the impact of climate change on these forests. In Fennoscandia, this objective is currently difficult to achieve due to the lack of knowledge of long‐term (centuries to millennia) relationships between climate, fire and vegetation. We investigated the causes and consequences of changes in fire regimes during the Holocene (last ~11,000 years) on vegetation trajectories in the boreal forest of northern Finland. We reconstructed fire histories from sedimentary charcoal at three sites, as well as vegetation dynamics from pollen, moisture changes from Sphagnum spore abundance at two sites, and complemented these analyses with published regional chironomid‐inferred July temperature reconstructions. Low‐frequency, large fires were recorded during the warm and dry mid‐Holocene period (8500–4500 cal. year BP), whereas high‐frequency, small fires were more characteristic of the cool and wet Neoglacial period (4500 cal. year BP onward). A higher proportion of charcoal particles with a woody aspect—characterizing crown fires—was recorded at one of the two sites at times of significant climatic and vegetational changes, when the abundance of Picea abies was higher. Synthesis. Our results show both a direct and an indirect effect of climate on fire regimes in northern Fennoscandia. Warm and dry periods are conducive to large surface fires, whereas cool and moist periods are associated with small fires, either crown or surface. Climate‐induced shifts in forest composition also affect fire regimes. Climatic instability can alter vegetation composition and structure and lead to fuel accumulation favouring stand‐replacing crown fires. Considering the ongoing climate warming and the projected increase in extreme climatic events, Fennoscandian forests could experience a return to a regime of large surface fires, but stand‐replacing crown fires will likely remain a key ecosystem process in areas affected by climatic and/or vegetational instability.