Summer Soil Temperatures Research Articles

A New Assessment of High Punctual Solar Trackers Effects on Poultry Welfare in Agrivoltaïc Open-Air Runs

Open-air poultry farming is currently developing with the increasing society demand for livestock farming better considering animal welfare. Outside animal comfort and open-air runs exploration could be enhanced by shelters such as trees or photovoltaic (PV) structure. The aim of this study is to confirm previous results to evaluate (i) the microclimates generated under high punctual PV trackers, (ii) the effect on laying hens comfort, (iii) the use of panels shadow area by hens. In three experimental sites, microclimates were studied and laying hens were counted in a control area, under such PV tracker and under a tree. Results showed that PV trackers, as big trees, lowered summer soil and air temperatures, radiation and lightness, decreased the occurrences of stress situations for hens, and that more hens were counted under trackers than in a control area. These results may help for optimizing such agrivoltaïc system and the hens welfare by improving the open-air run design with PV structures and vegetation.

BrGDGT lipids in cold regions reflect summer soil temperature and seasonal soil water chemistry

The distribution of brGDGT lipids produced by soil bacteria has been used to reconstruct temperatures in marine and terrestrial settings as far back as the Cretaceous period. However, modern calibrations of this proxy have primarily relied on air rather than in situ soil temperatures, which can differ by more than 10 °C. Furthermore, the influence of other parameters such as temperature seasonality and soil chemistry on brGDGT lipids is not fully understood. We measured brGDGT distributions, in situ soil temperatures, pH, soil water content, and electrical conductivity on soils from the Eastern Canadian Arctic and Iceland. We compiled our results with those of published soil brGDGT studies that also provide in situ soil temperatures and ancilliary measurements and generated global temperature and pH calibrations from the resulting dataset. Soil temperatures outperformed air temperatures in these calibrations, with mean summer soil temperature providing the highest-performing fit among the 10 tested soil temperature parameters. When applied to a loess/paleosol sequence from the Chinese Loess Plateau, these new calibrations produced paleotemperature and paleo-pH histories consistent with the results of previous studies, encouraging the application of our new calibrations on a broader scale. We also detected 7-methyl and IIIa’’ brGDGT isomers in our Eastern Canadian Arctic and Iceland soils, which have been shown in lakes to relate to salinity and anoxia, respectively. While neither correlated with bulk soil properties such as conductivity, soil water content, or pH, these brGDGT isomers did correlate with seasonality and winter soil temperature. We hypothesize that these compounds are generated in winter by bacteria in habitable niches of more saline, sometimes anoxic liquid water in the otherwise frozen soil matrix. Finally, we report the presence of overly branched GDGTs with m/z = 1064 and suggest that these heptamethylated tetraethers should be investigated as a potential tool for improving brGDGT calibrations. Overall, our results expand our understanding of the seasonality of brGDGT production, especially at high latitudes, and provide in situ soil temperature and pH calibrations for global use.

Assessing Photovoltaic Trackers Effects on Open-Air Poultry Welfare

Open-air poultry farming is currently developing with the increasing society demand for livestock farming better considering animal welfare. Outside animal comfort and open-air runs exploration could be enhanced by shelters such as trees or photovoltaic (PV) trackers. The aim of this study is to evaluate (i) the microclimates generated under PV trackers, (ii) the effect on laying hens comfort, (iii) the use of panels shadow area by hens. In three experimental sites, microclimates were studied and laying hens were counted in a control area, under a PV tracker and under a tree. Results showed that PV trackers, as trees, lowered summer soil and air temperatures and radiation, decreased the occurrences of stress situations for hens, and that more hens were counted under trackers than in a control area. Methodological improvements can be led to better apprehend differences of area uses by hens.

Континентальность климата и теплообеспеченность почв степных склонов в верховьях Индигирки и Колымы

Steppe biotopes on the southern slopes of the Indigirka and Kolyma headwaters, judging by vegetation and invertebrate population, are analogous to South Siberiaвs mountain steppes. At the same time, the area of steppe slopes and the number of steppe plant and animal species decrease from the Indigirka to the Kolyma. Climate continentality decreases in the same direction, which permits to consider it the main factor impacting the distribution of thermophytic steppes in Northeast Asia. Measurements of temperatures in thermophytic steppe soils in the named river basins revealed no soil heat supply differences related to climate continentality. Comparison of the measurement results with long-term observation data on xeromorphic biotopes of southern slopes in the upper reaches of the Kolyma River permitted to extend this conclusion to the soils of all open dry southern slopes in the headwaters of the Kolyma and Indigirka rivers. Thus, the role of climate continentality and summer soil temperature regime in the long-term preservation of "islands" with a large number steppe species of plant and animal surrounded by permafrost mountain-taiga ecosystems in the upper reaches of the Indigirca River is questioned. It is shown that restrictions in the spatial distribution of some steppe invertebrate species are not determined by differences in the summer temperature regime of soil in the headwaters of the Indigirka and Kolyma Rivers, either.

The Effect of Clearing Diseased Wood on the Soil’s Physicochemical Properties in Black Pine Forests

Clearing diseased wood is a common measure used to reduce the continued spread of pine wilt disease and prevent infecting other pines. However, the impact of clearing diseased wood on the physicochemical properties of the soil is still unclear. To elucidate this matter, we conducted a series of soil experiments and observations in Changdao, mainly focused on uncut black pine, cut black pine, and the inter-forest zone. The results showed the following. (1) The soil beneath the forest underwent a transition towards the characteristics of forest and grassland after clearing diseased wood, which indicated a potential shift in the ecosystem’s structure and function. (2) Clearing diseased wood led to an increase in the soil pH of 0.15, indicating that it facilitated the recovery of acidic soil. (3) The clearing of diseased wood can coarsen the soil’s texture. Moreover, it effectively reduced the surface soil temperature (0–20 cm) in summer by 1.52 °C, as well as significantly decreasing the surface (0–20 cm) soil moisture in spring and summer by 1.3% and 2.43%, respectively. (4) Clearing diseased wood clearing can effectively modify the content of essential nutrients in the soil. It reduced the available nitrogen by 26.86 mg·kg−1, increased the available phosphorus by 0.57 mg·kg−1, and decreased the available potassium by 1.68 mg·kg−1. Meanwhile, clearing diseased wood exacerbated soil salinization and increased the soil’s salt content by 0.70 g·kg−1. The findings of this study provide scientific solutions for the sustainable ecological development of black pine forests in Changdao.

Interannual variation in evapotranspiration in an urban forest reserve with respect to drought

IntroductionA warming global climate is expected to perturb the hydrological cycle, resulting in deviations in both frequency and duration of drought and thus being hypothesized to lead to interannual variation in evapotranspiration (ET). Interannual variation in ET in urban forest ecosystems in response to drought remains poorly understood.MethodsHere, ET in an urban forest reserve in the megalopolis of Beijing was investigated using eddy-covariance measurements collected over six consecutive years (2012–2017).ResultsThe mean annual cumulative ET was 462 ± 83mm (±first standard deviation), with a coefficient of variation of 18%. Interannual variation in both annual and monthly ET was shown to be largely controlled by canopy conductance (gs), affected by environmental factors. The main factors affecting interannual variation in monthly ET varied seasonally, namely, soil volumetric water content (VWC) and normalized difference vegetation index (NDVI) in spring, precipitation and soil temperature in summer, and VWC and net radiation (Rn) in autumn. Interannual variation in annual ET was driven largely by spring and mid-summer droughts induced by insufficient precipitation during the non-growing and mid-growing seasons, respectively. Spring drought reduced annual ET by restricting leafing out, shortening growing season length (GSL), and reducing the normalized difference vegetation index (NDVI). The summer drought reduced annual ET by reducing stomatal conductance.Discussion and conclusionResults from this study point to the importance of precipitation timing and volume and the soil moisture carry-over effect in controlling interannual variation in ecosystem ET. Irrigation during the early spring and mid-summer is viewed as a practical management measure for sustaining growth and better ecosystem services in urban forests in Northern China.

Influence of microclimate control on the growth of asparagus under greenhouse in tropical climates.

High temperatures have become common in cities in Taiwan, and this phenomenon has spread to surrounding agricultural areas. Tainan, a city located in a tropical climate zone with agriculture as its primary development industry, is one of the cities considerably affected by the high temperature. High temperatures can reduce crop yields and even cause plant death, especially for vulnerable high-value crops, which are severely to microclimate conditions. Asparagus is a high-value crop that has long been cultivated in the Jiangjun District of Tainan. Recently, asparagus has been planted in greenhouses to protect against pests and natural disasters. However, the greenhouses can overheat. To identify the optimal growth environment for asparagus, this study applies vertical monitoring to record the temperature in the greenhouse and the soil moisture content of a control (canal irrigation) and an experimental (drip irrigation) group. When the surface layer of the soil exceeds 33°C, the tender stems of asparagus bloom readily, reducing its commercial value. Therefore, drip irrigation was conducted with cool water (26°C) to reduce soil temperature in summer and warm water (28°C) to increase soil temperature in winter. The study also recorded the growth of asparagus using daily yields measured by farmers during weighing and packing to understand the benefits of controlling the greenhouse microclimate. This study reports a correlation of 0.85 between asparagus yield and temperature and a correlation of 0.86 between asparagus yield and soil moisture content. The use of a drip irrigation system with a water temperature adjustment function not only saves up to 50% of water but also resulted in an average yield increase of 10% through maintaining stable soil moisture content and temperature. Therefore, the findings of this study can be applied to asparagus yields affected by high temperature and can solve the problems of poor quality in summer and low yield in winter.

Cutting peatland CO2 emissions with water management practices

Abstract. Peat decomposition in managed peatlands is responsible for a decrease of 0.52 GtC yr−1 in global carbon stock and is strongly linked to drainage to improve the agricultural bearing capacity, which increases aeration of the soil. Microbial aerobic decomposition is responsible for the bulk of the net CO2 emission from the soil and could be reduced by wetting efforts or minimizing drainage. However, the effects of rewetting efforts on microbial respiration rate are largely unknown. In this study, we aimed to obtain more process-based understanding of these rewetting effects on peat decomposition by integrating high-quality field measurements and literature relationships with an advanced hydrological modelling approach where soil moisture and temperature are centralized as the main drivers for peat decomposition. In 2020 and 2021, two dairy farming peatlands, where subsoil irrigation and drainage (SSI) was tested against a control situation, were continuously monitored for CO2 fluxes, groundwater table, soil moisture and soil temperature. After successfully representing field hydrology and carbon dynamic measurements within our process-based model, we further explored the effects of rewetting under different weather conditions, water management strategies (raising ditchwater levels and SSI) and hydrological seepage settings. To represent peat carbon dynamics we introduced a methodology to estimate potential aerobic microbial respiration rate, based on potential respiration rate curves for soil temperature and water-filled pore space (WFPS). Measurements show that rewetting with SSI resulted in higher summer groundwater levels, soil temperatures and WFPS. SSI reduced the net ecosystem carbon balance (NECB) by 1.58 ± 0.56 kg CO2 m−2 yr−1 (83 ± 25 %) and 0.66 ± 0.62 kg CO2 m−2 yr−1 (28 ± 15 %) for Assendelft and Vlist respectively in 2020. SSI had a negligible effect in 2021 for both research locations, due to more precipitation, lower temperatures and different SSI management (in Assendelft) as compared to 2020. Simulated rewetting effects were in agreement with measured rewetting effects. Model simulations indicate that raising ditchwater levels always reduces peat respiration rates. Furthermore, we found that the application of SSI (i) reduces yearly peat respiration rates in a dry year and/or with downward hydrological fluxes and (ii) increases peat respiration rates in a wet year and/or when upward groundwater seepage is present. Moreover, combining SSI with high ditchwater levels or pressurizing SSI systems will further reduce peat respiration rates. We show that our process-based approach based on temperature and WFPS soil conditions to determine NECB represents observed variance to a greater extent than empirical relationships that involve average groundwater level observations or simulations. Therefore, we recommend using this kind of approach to estimate the effectiveness of rewetting. When this is not possible, we recommend using mean summer groundwater level instead of mean annual groundwater level as a proxy to estimate NECB. Such relations between mean groundwater levels and NECB are prone to underestimating NECB for SSI parcels.

Evaluation of Three Reanalysis Soil Temperature Datasets with Observation Data over China

Soil temperature is a crucial parameter in surface emissions of carbon, water, and energy exchanges. This study utilized the soil temperature of 836 national basic meteorological observing stations over China to evaluate three soil temperature products. Soil temperature data from the China Meteorology Administration Land Data Assimilation System (CLDAS), European Centre for Medium-Range Weather Forecasts (ERA-Interim), and Global Land Data Assimilation System (GLDAS) during 2017 are evaluated. The results showed that soil temperature reanalysis datasets display a significant north-to-south difference over eastern China with generally underestimated magnitudes. CLDAS data perform soil temperature assessment best at different depths and can be reproduced well in most areas of China. CLDAS slightly overestimates soil temperature in summer. The most significant deviation of ERA-Interim (GLDAS) appears in summer (summer and autumn). As soil depth increases, the soil temperature errors of all three datasets increase. The CLDAS represents the soil temperature over China but owns a more considerable bias in barren or sparsely vegetated croplands. ERA-Interim performs poorest in urban and built-up and barren or sparsely vegetated areas. GLDAS overall owns an enormous bias at the mixed forest, grassland, and croplands areas, which should be improved, especially in summer. However, it performs better in open shrublands and barren or sparsely vegetated areas. The ST of mixed forests shows better results in the south region than the north region. For grasslands, smaller MEs are located in the north and northwest regions. The ST of croplands shows the poorest performance over the northwest region.

Near‐surface soil thermal regime and land–air temperature coupling: A case study over Spain

AbstractUnderstanding the near‐surface soil thermal regime and its connection to the atmospheric state is important for the assessment of several climate‐related processes. However, the lack of in situ soil temperatures measurements limits the analysis of such processes. In this study, we have developed a quality‐controlled soil temperature database for Spain that consists of 39 sites spanning from 1987 to 2018. We have used this database to assess the near‐surface soil thermal regime. Likewise, we evaluate at seasonal to multidecadal timescales the land–air temperature coupling over Spain by analysing the structure of the surface air temperature (SAT) and the ground surface temperature (GST) covariance and also their long‐term evolution. In addition, we have employed the ERA5‐Land reanalysis to test the consistence between observations and reanalysis. The results show that the near‐surface soil thermal structure is dominated by conduction despite some influence of hydrology‐related processes. Regarding the land–air temperature coupling, we have found a strong connection between SAT and GST. However, in the summer months there is an offset in SAT–GST at some sites due to limited evaporation and enhanced sensible heat fluxes. Furthermore, multidecadal SAT–GST decoupling may exist over some sites as a response to decreasing precipitation. The ERA5‐Land represents the observations' climatology well, but it underestimates the summer soil temperature observations and the long‐term trends at some sites.

Soil Fauna of Ranibari Community Forest, Kathmandu, Nepal

Abstract Ranibari Community Forest (RCF) is the important forest patch present within the highly urbanized Kathmandu Valley with information gaps on soil fauna. This study aimed to explore the soil meso and macrofauna of the forest. Fourteen random quadrats (1 × 1 m2) were laid within seven blocks. Leaf litter samples and soil cores were collected, screened, sieved, and searched under a white sheet, once a fortnight from May to November 2019. The results showed that the diversity, abundance, and richness of soil fauna were the highest in the summer season (H´ = 2.897, abundance = 1,973, S = 84) dominated by Collembola. The Soil Biological Quality Index (QBS-ar) value was also found to be the highest in summer (QBS-ar = 417) and successively decreased in succeeding seasons. Soil fauna was diverse and evenly distributed in soil layers throughout the seasons, but the abundance was greater in leaf litters, particularly in summer. Fauna like Chilopoda, Diplopoda, Haplotaxida, and Isopoda were seen to be affected negatively by soil temperature in summer and autumn seasons. Soil moisture content was found to be positively correlated with immature insects, earthworms, and millipedes in the rainy and autumn seasons. Besides, the pH of the soil was seen to affect Diplura only in the autumn season. The relation of fauna with the physicochemical parameters (temperature, moisture, and pH) and also with other taxa showed their ecological roles and adaptation to a specific microclimate.

Evidence for multiple potential drivers of increased phosphorus in high-elevation lakes

Total phosphorus (TP) concentrations have increased in many remote mountain waterbodies across the western United States, and reports of algal blooms in these systems have increased in frequency. Explanations for observed TP increases are uncertain, and typical landscape drivers, such as agricultural/urban runoff, are implausible. We investigated multiple atmospheric and terrestrial-P loading mechanisms to explain the observed decadal increase in TP, including a novel hypothesis that warming soils may lead to elevated P fluxes to receiving water bodies. Using northern Utah mountains ranges as a case study, we measured prospective inputs of total and bioavailable P via dust deposition. Terrestrial loading was evaluated through soil leaching experiments designed to simulate soil acidification and recovery, as well as observed decadal increases in soil temperatures and extended growing season. In the Uinta Mountains, dust-P flux appears to be one of the most plausible mechanisms for P increases where we estimated bioavailable dust-P loading ranged from 1.6 to 23.1 mg P m−2 yr−1. However, our results revealed that an increase of soil pH by 0.5 units could lead to a rise in leached P, ranging from 4.7 to 65 mg P m−2. Rising temperatures also showed the potential to increase soil P leaching; Observed average historical (~ +3 °C) and future (+2 °C) increases in temperature led to a prospective increase in leached P from 2 to 264 mg SRP m−2. While we found that pH shifts can mobilize significant amounts of P in some locations, we found no evidence of pH changes through time in the Uinta Mountains. However, summer soil temperatures increased at most locations. The mechanisms evaluated in this study can help explain the widespread observed increases in P across Western US lakes, but the mechanisms that dominate in any given region are likely to vary based on local to regional factors.

Forestry clear‐cuts increase environmental temperatures, affecting the ecophysiological responses of specialized beetles in fragmented landscapes

AbstractThe forestry practice of clear‐cutting (the removal of all woody vegetation) results in a range of negative impacts on ectotherm physiology and behaviour. Organisms in these habitats can experience elevated body temperature due to increases in air and soil temperature, affecting their performance. In this study, we evaluated the effect of ambient temperature (air and soil), habitat type (clear‐cut, forest edge and forest interior) and season (summer and autumn) on body temperature, microhabitat use and velocity of the thermosensitive ground‐beetle Ceroglossus chilensis. We found that body temperature of C. chilensis increased with higher soil temperature in summer, especially in clear‐cuts, although body temperature decreased rapidly when sheltering in microhabitats (e.g. dead logs, plants and leaf litter). Leaf litter and dead logs were more frequently selected in native forest and clear‐cuts, respectively, but in clear‐cuts, dead logs and plants have up to 4°C higher than the optimal preference of C. chilensis. Higher soil temperature and lower activity levels of beetles were observed in clear‐cuts in summer than in the other two habitat types, and beetles moved faster in the interior of the native forest than in other habitats regardless of the season. Our results suggest that C. chilensis is a bioindicator of changes in ambient temperatures occurring after forest fragmentation by forestry. We suggest that the management and maintenance of thermal shelters in clear‐cuts could lessen the negative effects of high temperatures on thermosensitive beetles in fragmented forest landscapes.

Thermal conductivity contrast effect of organic soils and its environmental implications

Thermal conduction control is important for retarding permafrost degradation and mitigating of frost geohazards. Similar to a thermodiode, high thermal conductivity contrast (HTCC) materials can serve as good thermal insulators. A preferred HTCC material for ground cooling is larger in thermal resistance in summer and smaller in winter. Because of contrasting thermal conductivity under frozen and thawed states, organic soil is blessed with such a property. This study quantified and reported the HTCC effects on a range of soil organic matter concentrations (SOMC) and soil moisture saturation degree (SMSD). Using the COMSOL, influences of different SOMC and SMSD on ground temperatures were simulated and compared with laboratory-measured properties. Simulation results demonstrated that with constant SMSD at 20% throughout the year, the thermal insulation effect was strengthened with increasing SOMC. A better insulating effect was judged by lower annual amplitudes and smaller depths of zero annual amplitude of ground temperatures. In case of low SMSD in summer (20%) and high SMSD in winter (60–80%), the HTCC effect of soil is enhanced with increasing SOMC. This enhancement was evidenced by increased thermal offsets and decreased maximum summer and average near-surface soil temperatures. With constant SOMC and increasing SMSD, the rising HTCC effect gradually cools the ground. An integral analysis indicates that the higher the SOMC and SMSD in winter, the larger the thermal offset and the lower the ground temperature, i.e., the greater the HTCC effect of organic soil. This study may provide geocryological bases for engineering and environmental applications in cold regions.

Soil chemistry, temperature and bacterial community composition drive brGDGT distributions along a subarctic elevation gradient

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane lipids which can be used to reconstruct past terrestrial mean annual air temperature (MAAT) and soil pH values. To reconstruct these environmental conditions in geological archives, we make use of the brGDGT ratios MBTʹ5ME, CBTʹ and IR, which summarize the structural variation in brGDGT lipids. However, the most recent calibrations between the brGDGT-based temperature proxy MBTʹ5ME and temperature on a global scale are characterized by a residual error between 3.8 °C and 6.0 °C. This lack of accuracy of the MBTʹ5ME-MAAT calibration is often attributed to the difference between soil and atmospheric temperatures. Also, previous studies suggested that the variation of the MBTʹ5ME along chemistry and temperature gradients reflects a possible influence of bacterial community changes. Here, we analyzed the effect environmental variables have on brGDGT signatures collected along five elevation gradients in the north of Sweden and Norway, where MAAT changed between –4.7 °C and 2.7 °C and soil pH varies between 3.3 and 5.7. Specifically, we determined the impact of air and soil temperature, the bacterial community composition and soil chemical characteristics. The range of MBTʹ5ME values encountered (0.30–0.70) results in a wide range of reconstructed temperatures (1–13 °C). The use of in situ soil temperature data spanning one year did not improve the correlation with brGDGT MBTʹ5ME values, compared to using a long-term MAAT dataset. Although a temperature gradient was present, soil chemistry apparently determined brGDGTs concentration and distribution on this local scale. Specifically, soils with high cation exchange capacity (CEC) showed an increased concentration of brGDGT Ia, resulting in increased Community Index (CI) and MBTʹ5ME values, both brGDGT ratios that reflect the degree of methylation. Soils with increased pH (pH range 5–6) had a distinct brGDGT fingerprint with generally decreased MBTʹ5ME values, which resulted in the correlation between MBTʹ5ME and soil pH (r = –0.60, p < 0.01). Contrary to expectations, pH was a better predictor of MBTʹ5ME values than temperature (r = 0.47, r = 0. 44, p < 0.01, with MAAT and mean summer soil temperature (MSST), respectively). Soil pH also shaped the bacterial community composition, and a bio-indicator approach was used to narrow down the proposed bacterial producer of brGDGT lipids in high CI (Acidobacteria subgroups 1 and 3) and high pH soils (Acidobacteria subgroups 6 and 7). Building upon previous research, this confirms that brGDGTs respond to similar changes in bacterial community composition across sites. Because of the interplay between temperature and soil chemistry, the relationship between the MBTʹ5ME and soil temperature is clearly complex at the local scale. Further disentangling these environmental drivers is still essential in the development of the MBTʹ5ME proxy as paleothermometer.

The magnitude and causes of edge effects on soil organic carbon stocks within and across urban to rural forest patches

Landscape fragmentation has created large areas of forest edge. Understanding how soil organic carbon (SOC) stocks within forest edges respond to fragmentation is essential to assess carbon budgets; however, the causes and magnitude of edge effects on SOC stocks have been poorly characterized. Here, we quantify the edge effects on SOC stocks within and across urban to rural forest patches from three fragmented urban forests to a large patch of rural forest. The SOC stocks within 20 m of the rural forest edge (1.86kgCm−2) is on average 80% lower than the interiors of rural forest (10.47kgCm−2). We found that biotic factors, including annual litterfall mass (R2 > 0.94), peak leaf area index (R2 > 0.92), and fine-root mass density (R2 > 0.77), explained the spatial variation in SOC stocks within the rural forest. In urban forests, human activities at forest edges led to contrasting edge effects on SOC stocks, for instance, the SOC stocks at the east edges (4.74 kgC m−2) were 56% greater than at the west edges (3.03 kgC m−2) explained by the adjacent land uses (e.g., paved roads vs. non-paved soils) and in-situ litterfall management. We also found significant differences in summer soil temperature (ΔTS > 2.8 °C) and soil moisture (ΔVWC > 0.05 m3 m−3) between the east and west forest edges. Our results reveal that the factors responsible for the edge effects on SOC stocks in rural forests are biotic factors, while heterogeneous human activities at the local scale lead to complex edge effects on urban forest SOC stocks.

Retraction Note: Fire and summer temperatures work together breaking physical seed dormancy

Fire and high summer soil temperatures can break physical seed dormancy in Mediterranean fire-prone ecosystems. Their independent effect is somewhat recognized but both factors may act together with a synergistic effect yet unknown. This study aims to determine the isolated and combined effects of fire and summer temperatures on the release of physical seed dormancy in Cistaceae species. Fire and summer temperature treatments were applied in a factorial experiment to seeds of 12 species of Cistaceae. Seeds previously exposed or not to a heat shock (fire simulation) were kept for 1 or 2 months at constant or alternating temperatures (summer temperatures simulation). Additionally, I compared the effect of exposing the seeds to a heat shock before or after they had been subjected to the summer temperatures. Heat shock increased germination of all species, but summer temperatures produced different results. When seeds were exposed to summer temperatures after heat shock, germination decreased. This negative effect disappeared when heat shock was simulated at the end of the summer temperatures. Fire and summer temperatures modulate timing of germination in Cistaceae with a joint control on post-fire regeneration. Cycling of sensitivity to physical dormancy release may be the mechanism to explain this fine-tuning, which would ensure germination when environmental conditions are suitable for growth. These results contribute to our understanding of vegetation dynamics and postfire regeneration in Mediterranean ecosystems.

남한지역에서의 관측 지중온도의 기후학적 특성 및 변동경향

Soil temperature (SoT) is one of the important climate elements for the land-atmosphere interactions. In this study, the climatic characteristics and trends of SoT were analyzed at nine locations for the period of 1966 to 2020. In addition, effect of precipitation on the interannual variations of SoT was also addressed. The monthly average of the SoT shows seasonal and interannual variations regardless of location. While there are some differences depending on the location and depth, the interannual variations of SoT occur more strongly at the shallow layer during summer comparatively other seasons. The strong negative correlation between SoT and precipitation of summer shows that the large interannual variations of SoT in summer is closely related to the strong interannual variations of precipitation of same season. According to the depth the range of SoT is larger in winter and summer and smaller in spring and autumn. Generally, air temperature and SoTs are increasing due to global warming. However, the increasing trend varies and depends on the location and depth of the study area. Most of investigation stations are revealed a strong increasing trend, particularly, at the shallow layer during summer season.

Exposing wind stress as a driver of fine‐scale variation in plant communities

Abstract The effects of temperature and precipitation, and the impacts of changes in these climatic conditions, on plant communities have been investigated extensively. The roles of other climatic factors are, however, comparatively poorly understood, despite potentially also strongly structuring community patterns. Wind, for example, is seldom considered when forecasting species responses to climate change, despite having direct physiological and mechanical impacts on plants. It is, therefore, important to understand the magnitude of potential impacts of changing wind conditions on plant communities, particularly given that wind patterns are shifting globally. Here, we examine the relationship between wind stress (i.e. a combination of wind exposure and wind speed) and species richness, vegetation cover and community composition using fine‐scale, field‐collected data from 1,440 quadrats in a windy sub‐Antarctic environment. Wind stress was consistently a strong predictor of all three community characteristics, even after accounting for other potentially ecophysiologically important variables, including pH, potential direct incident solar radiation, winter and summer soil temperature, soil moisture, soil depth and rock cover. Plant species richness peaked at intermediate wind stress, and vegetation cover was highest in plots with the greatest wind stress. Community composition was also related to wind stress, and, after the influence of soil moisture and pH, had a similar strength of effect as winter soil temperature. Synthesis. Wind conditions are, therefore, clearly related to plant community characteristics in this ecosystem that experiences chronic winds. Based on these findings, wind conditions require greater attention when examining environment–community relationships, and changing wind patterns should be explicitly considered in climate change impact predictions.

Seasonal variations in carbon dioxide exchange fluxes at a taiga–tundra boundary ecosystem in Northeastern Siberia

Arctic and boreal permafrost ecosystems in Eastern Siberia, considered crucial to the climate system and global carbon cycle, are particularly vulnerable to climate change. This study investigates carbon dioxide (CO2) exchange fluxes over northeastern Siberia from 2013 to 2015 in a taiga–tundra boundary ecosystem for which such measurements are scarce. The growing season (May–September) net CO2 exchange flux (NEE) was −39.4 (−60.1 to −20.2) gCm−2, with ecosystem respiration (RE) = 306.2 (288.1–317.9) gCm−2 and gross primary production (GPP) = −345.5 (−372.5 to −317.7) gCm−2. Microclimatic factors determining these CO2 exchange fluxes change seasonally. These fluxes are significantly affected by the timing of the onset of C uptake, which is reflected by changes in the soil temperature in spring and early summer, following which fluxes respond well to the photosynthetic photon flux density, especially for NEE. These CO2 exchange fluxes at the northeastern Siberian taiga–tundra boundary ecosystem are significantly smaller than those previously reported at southern-taiga forest sites. Spring snow meltwater-rich soil moisture conditions render southern-taiga sites as stronger CO2 sinks in June than taiga–tundra boundary ecosystem, which may be largely responsible for the pronounced north–south gradient in growing season NEE.