Variation In Soil Temperature Research Articles

Effects of Coolant Temperature on the Characteristics of Soil Cooling Curve

The cooling curves of soil are graphs that represent the variation of soil temperature with time when it is cooled. Knowledge of soil cooling curves and their characteristic parameters play an important role in most thermal analysis concerning soil freezing and/or thawing. Understanding the effect of environmental temperature on these parameters may help scientists better understand how frost heaves happen and how to predict the occurrence of frost heaves more accurately. For soils with identical type, water content, bulk density, and initial temperature, we believe that the freezing process and associated cooling characteristic parameters would be independent of the variation of external environmental temperature. To test this hypothesis, we carried out a series of freezing process experiments on soils with identical physical properties under different coolant temperature conditions. Here, the coolant temperature represents the magnitude of the environmental temperature. Our results indicate that the coolant temperature affects soil cooling curve profiles by changing the critical parameters of nucleation temperature, super-cooling, and phase-transfer duration of water in soil pores. According to the magnitude of the coolant temperature, soil cooling curves can be categorized into three different types: a “regular” freezing process without or with a little super-cooling, a sudden and small rise in temperature after the super-cooling “dip”, and a permanent super-cooling of non-freezing process. We have shown that the freezing temperature of soils is not influenced by the variation of coolant temperature.

Study on Varying Characteristics of Temperature Field and Moisture Field of Shallow Loess in the Freeze‐Thaw Period

The moisture and the temperature variation of shallow loess during the freeze‐thaw process have tremendous influences on the freeze‐thaw disease and agricultural development. The present paper, based on the field test of the temperature and water content of the shallow loess in the seasonal frozen region, probes into the variation of the temperature and moisture fields of shallow loess in the freeze‐thaw period. Field test shows that the daily variation of surface temperature reaches the maximum with the peak temperature appearing around 14:00, and the time when the peak temperature appears gradually postpones as the depth increases. Moreover, the daily variation of soil temperature decreases with the increase of temperature, and the variation can be ignored given the depth of more than 30 cm. In addition, there is an obvious variation of moisture content in shallow soil under the action of freeze‐thaw cycles. In this regard, the coupled calculation model is proposed in this paper to simulate the dynamic variation of temperature and moisture in shallow soil in Bin County located in Western China under natural conditions, compare the calculation value with the measurement value, and further verify the rationality of the numerical calculation method and parameter selection. Furthermore, the variation law of the maximum frozen depth with the air temperature is obtained through the simulation of extreme cold climate conditions.

Effects of different parameters on transient heat transfer surrounding energy piles in unsaturated soils

Energy piles are one of the best candidates to harvest shallow geothermal energy. Continuing harvesting and rejecting thermal energy from/to the ground may permanently change the soil temperature and consequently, may lead to different soil resistance parameters. Therefore, careful prediction of soil temperature variation close to energy geostructures is needed. This paper investigates the various parameters of heat source and soil media on transient heat transport in unsaturated soils. Green’s function and the method of separation of variables are employed to analytically analyze the transient heat transfer in the vicinity of energy piles. Results indicate that although higher heat flux increases the soil temperature surrounding a heat source, it has negligible effect on thermal influence zone where the soil temperature varies. In contrast, higher thermal diffusivity results in lower soil temperature close to a heat source while it increases the thermal influence zone.

Analyis of periodical variability of insolation and soil temperature in the Crimea

According to the 22-year-old series of climatology NASA Surface meteorology and Solar Energy, the results of the analysis of the temporal series of local changes in insolation and the temperature of the earth and ground air in the Crimea are carried out. A statistical analysis was carried out and a continuous time-frequency wavelet analysis revealed increased (compared to other Crimean points) insolation and heating of the earth’s surface at Kara-Dag. Using the time-and-frequency continuous wavelet analysis, six regular astronomical fluctuations, the periods of which are comparable with the periods of seasonal fluctuations, lunar and lunar-solar tidal waves, were found in the spectral structure of data on the average daily insolation incident on the horizontal surface of the earth at Kara-Dag. Periodic oscillations comparable with fluctuations in solar activity and the dynamics of rotation of the Earth-Moon system are described by sinusoidal functions, the parameters of which are determined from observations. In the data on the average daily total insolation falling on the surface of the earth at the Kara-Dag point, regular periodic fluctuations were found over an interval of periods of ~(87―402) days. The most powerful harmonic oscillations are distinguished in the interval of periods ~(231―452) days; in the time interval ~(1995―2005) years, an increasing local increase in the vibrational energy is observed. An increase in the average annual average surface temperature in the Crimea in a southeastern direction has been recorded. In individual points, deviations from the general trend are observed, which may be associated with local geological processes. The greatest warming of the earth’s surface is observed at Kara-Dag, which corresponds to increased general insolation at this point. Using the method of calculating the functions of the mutual (two-channel) power spectral density, we established mutual correlations between the time sequences of observations of local changes in insolation and changes in the length of the day, the number of sunspots, and global temperature indices.

Regional distribution patterns of wetland monocots with different root turnover strategies are associated with local variation in soil temperature.

Herbaceous perennial wetland monocots in Northern Ontario, Canada, show dichotomous root overwintering patterns, either with full senescence in autumn or survival over the winter, comparable to deciduous and evergreen leaf habits in trees. To test if these root strategies differ in their associations with growing season length, soil temperatures were recorded in autumn, winter and spring on 38 wetland sites with their dominant species being either of these two root overwintering strategies, altogether 19 monocot species. Traits associated with these strategies were assessed in garden experiments for a subset of these species. Sites with species with autumn-senescing roots were, on average, warmer than sites with species with overwintering roots. The 13 coldest sites were all sites of species with overwintering roots. Spring shoot growth in the field was delayed in species with autumn-senescing roots, despite their higher shoot relative growth rates in the garden, possibly due to the necessity to produce roots first. We conclude that species with autumn-senescing roots are more constrained by temperature than species with overwintering roots, limiting their occurrence in cool climates to locally warm soils and constraining their distribution towards the north. This is comparable to constraints on distribution of deciduous and evergreen trees.

Crop rotation and sequence effects on temporal variation of CO2 emissions after long-term no-till application

Production, transport, and emission of CO2 from soil to the atmosphere are directly influenced by soil temperature and moisture conditions, exhibiting a high variability over time due to the influence of climate events and soil management practices. Thus, this study aimed to investigate the effect of summer and off-season crop residues on the temporal variation of soil CO2 emission (FCO2), soil temperature (Tsoil), and soil moisture (Msoil) under a no-till system that has been managed with the same crop arrangement for >16 years. The experiment was conducted in strips with three replications. Treatments consisted of summer crop sequences maize monoculture, soybean monoculture, and soybean-maize rotation, as well as off-season crops maize, millet, pigeon pea, grain sorghum, and crotalaria. Sixteen assessments of FCO2, Tsoil, and Msoil were carried out over 51 days. A significant effect of the interaction between time and summer crop sequences (F = 1.44; p = 0.02) and between time and off-season crops (F = 2.26; p < 0.01) was observed for FCO2. Moreover, a triple interaction was observed between summer crop sequences, off-season crops, and time for Msoil (F = 1.83; p < 0.01) and Tsoil (F = 1.32; p = 0.01). The values of FCO2 and Msoil were high on days 229 and 230 due to precipitations in the study area. The relationship between FCO2 and Msoil was positive in all the assessed management, and about 60% of FCO2 variation over the study period could be explained by soil water content variation.

The combined effects of maize straw mulch and no-tillage on grain yield and water and nitrogen use efficiency of dry-land winter wheat (Triticum aestivum L.)

Excessive soil evaporation induced water loss resulting in drought stress is a significant yield-limiting factor in dry-land regions of China. However, the crop yield response to straw mulch and tillage depends on the cumulative rainfall that varies greatly from year to year due to frequent occurrences of extreme weather events. The aim of this study was to investigate the responses of grain yield and water and nitrogen use efficiency to mulch-based no-tillage in both humid and dry climates. The experiment was laid out in split plot design using tillage as a main factor and maize straw mulch as sub-plot with three replications each. Maize straw mulch combined with no-tillage was able to conserve soil moisture (0.348 cm3 cm–3 vs. 0.398 cm3 cm–3) at tillering stage and reduce daily variation of soil temperature in the topsoil layer, and thereby increased the maximum number of wheat tillers and fertile spikes by 51.3% and 72.3%, respectively, compared to the no-mulch control. The favorable soil hydrothermal regime also enhanced the activities of soil urease and neutral phosphatase, which activated the release of plant-available soil N and Olsen–P by 61.4% and 43.2%, respectively, compared to the no-mulch control. Improved plant-available soil N lead to greater root system vigor and root surface area and thus promoted the nitrogen uptake efficiency (NUpE), maximum value of LAI and the plant assimilate accumulation. The grain yield, WUE and nitrogen utilization efficiency (NUtE) in mulch-based no-tillage were 36.8%, 16.0% and 14.8% greater, respectively, than those in no-mulch control, and they were more effective in a dry climate than in a humid climate. These results suggest that maize straw mulch combined with no-tillage can not only conserve soil moisture for wheat tillering but also activate the release of plant-available soil N and plant N acquisition for higher grain yield and water and nitrogen use efficiency.

Responses of ground-active arthropod community in Caragana shrub plantations to grazing management in desertified region.

We investigated the community structure of ground-active arthropods as well as vegetation and soil properties in Caragana shrub plantations under grazing and exclosure management across spring, summer and autumn in Yanchi County of Ningxia in northern China. The aim of this study was to uncover the responses of ground-active arthropods in shrub plantations to grazing management in desertified regions. The results showed that: 1) plant height, soil fine sand content, and soil electrical conductivity were significantly lower, whereas soil bulk density and coarse sand were significantly higher in shrub plantations under grazing than exclosure. 2) There were 40 families from 13 orders captured. The dominant groups included Formicidae and Tenebrionidae families, which comprised 68.75% of the total individuals. There were four common groups occupying 20.82% of the total individuals. The remaining 34 groups were relatively rare, only accounting for 10.44% of the total. Across the three seasons, the composition of ground-active arthropod community was significantly different between grazing and exclosure, which indicates the sensitivity and adaptability of ground-active arthropods to environmental changes including grazing management and seasonal changes. 3) There was a significant effect of grazing on total abundance of ground-active arthropods in shrub plantations, with significantly higher values under grazing than under exclosure. There was no significant effect of grazing management on group richness and diversity of ground-active arthropods in shrub plantations. 4) There was a correlation of total abundance, evenness index and the Simpson index with plant abundance, vegetation height, soil moisture, soil pH and electrical conductivity. There was a significant correlation of the Shannon index with vegetation height, soil moisture and soil fine sand. Plant density, and soil pH, soil moisture and soil temperature were the key factors driving the structure of ground-active arthropod communities in shrub plantations under gra-zing management across seasons based on the partial RDA results. It was concluded that the variations of plant height, soil pH, soil moisture and soil temperature under grazing management could result in different ground-active arthropod taxon to changing habitats. The conservation effect of shrub on ground-active arthropod could reduce the negative impacts of grazing. Spring grazing could enhance ground-active arthropod abundances in shrub plantations. It was necessary to pay attention to prevention of insects which are caused by spring grazing in shrub plantations.

Verification of the INM RAS-MSU land surface scheme using temperature and moisture measurements in peat and mineral soils

Detailed monitoring of soil temperature provides a unique experimental material for studying the complex processes of heat transfer from the surface layer of the atmosphere to the soil. According to air temperature monitoring data, within each of the key areas there are no significant differences between the data of the observation sites. According to annual (2011-2018) observations of soil temperature, it has been found that the microclimatic properties of bog ecosystems clearly manifest themselves in the characteristics of daily and annual variations of soil temperature. The thickness of the seasonally frozen layer at all sites is 20-60 cm, and maximum freezing of the peat layer is reached in February-March. There is evidence of degradation of the seasonally frozen layer that occurs both from above and from below. It has been found that similar bog ecosystems in different bog massifs may have significantly different temperature regimes. The peat stratum of northern bogs may be both warmer (in winter) and colder (in summer), in comparison with some bogs located 520 km to the south and 860 km to the west.

Diurnal Variability of Soil and Air temperature as a function of time and depth, A case study of the cold wave that hit Zawia region during the period 1-5 February 1999

Soil temperature is one of the important variables in agricultural studies, which is necessary to be measured and analyze. There are some major challenges facing a lot of agricultural studies focus on soil temperature in Libya, such as, the soil temperature is measured only at Agro meteorological stations in the country, the lack of stations, the measurement of soil temperature is a cumbersome business and not as simple as air temperature be noted by single thermometer, Separate thermometers are required to measure the temperature of the soil at different depths, the installation of thermometer sensor correctly in the soil is another very complicated technical matter. However, in Libya there are no enough studies into the pattern of hourly variation in soil temperature over twenty-four hours due to the lack of such measurements at agricultural lands. So that, this attempt has been made to diagnose the behavior of soil temperature and air temperature as a case study, This work was carried out by using the daily and hourly data recorded for the temperature in the standard depths of soil (5,10,20,30,50,100 cm), and the surface air temperature at heights of (5, 10, 15, 50, 100, 150, 200 cm), Data were measured, Reported and collected every three hours interval during the period from 01 to 05 February 1999, at Zawia Agro-Meteorological Station where the location of the station was under the effect of cold wave. The data were measured on a daily basis at 0000, 0300, 0600, 0900, 1200, 1500, 1800, 2100 UTC. The correlation coefficient between the hourly soil temperature and hourly air temperature at certain depths and heights were calculated using the Pearson’s Formula, then the matrix of correlation factors have been derived, The vertical profile for the hourly variation of temperature in the layer between 100 cm under the surface of soil and 200 cm above the surface of soil have been described, Graphs and tables were done to show more explanation. The analysis of the observation shows that soil temperature variability decreases with depth, the highest temperature variability in top soil, and the lowest one is deeper than 50 cm. These results were affected due to the prevailing weather situation because at night time there is no enough solar radiation and the ambient temperature is lower than soil temperature. As a result, the soil temperature transferred heat from soil to atmosphere above. In addition, the low thermal conductivity of the soil is also one important factor that affects heat storage. These results demonstrated the importance of monitoring the soil temperature as an important element for agricultural studies. The results of the present paper could fill in some of the gap related to the soil temperature studies in Libya, and can be used for planning agronomic and plant protection practices.

Soil Temperature Dynamics in Transbaikalia under Changing Climate Conditions

The dynamics of multiyear mean thermal conditions in the 3.2-m soil layer in Transbaikalia is studied. A high correlation between variations in air temperature and soil temperature is revealed for summer, and low correlation is found for winter. The trends in cumulative soil temperature during the positive and negative temperature seasons are identified. The sum of negative soil temperatures at the depth of 80 cm exhibits an increasing multiyear trend. In cold seasons, the linear trends in soil temperature are stronger as compared to air temperature trends.

Effects of fire rotation interval and overstory type on ambient soil temperatures in ponderosa pine forests in Arizona

Ambient soil temperatures were measured every four weeks from May 1986 to November 1986 at three depths under the organic forest floor in ponderosa pine (Pinus ponderosa Lawson &amp; C. Lawson) forests in three stand types subjected to periodic prescribed burning. Temperatures at the organic layer – soil surface interface in sawtimber stands were higher and more variable than in pole and saplings stands. Temperature variability reached a maximum in the summer and decreased into the fall and early winter. Soil temperature variability decreased as depth below the surface increased. Three years after the low-intensity prescribed burns, soil temperatures in the burned stands were not significantly different from the those in the unburned controls, suggesting that any effect, though none was detected, of the low-intensity prescribed burns on soil temperature and belowground processes affected by temperature is short-lived in these stands.

The effect of soil temperature seasonality on climate reconstructions from paleosols

Paleosols comprise an important archive of continental paleoclimate information throughout geologic history, but resolving temperature seasonality poses a challenge to the application of paleosol-derived temperature proxies. Not only does seasonality exert a strong control on the biosphere, but it can also obfuscate accurate interpretation of proxy records of paleotemperature. In order to examine the effect temperature seasonality has on paleosol temperature proxies, soil temperature data were compiled from over 200 stations that comprise the NRCS Soil Climate Analysis Network. Observed and modeled seasonal soil temperature variations were then compared to quantify system behavior. Greater than predicted soil temperature seasonality is observed at nearly half of the sites, driven primarily by direct heating of the soil surface by solar radiation. The ground-heating effect becomes more pronounced at sites receiving less than 600 mm of annual precipitation, with an average effect > 4 °C when mean annual precipitation falls below 300 mm. Large ground heating effects cannot be presumed for all carbonate-bearing paleosols, but the effect can be approximated when combined with paleo-precipitation estimates. Approximately two-fifths of sites record less temperature variation than predicted. This reduction in soil temperature seasonality is a result of warmer cold-season soil temperatures, driven by processes such as snow cover insulation and explains why pedotransfer functions break down below mean annual air temperatures (MAAT) of 6 to 8 °C. Clumped isotope measurements of pedogenic carbonate from a stacked series of late Eocene paleosols from Northeastern Spain are also examined to demonstrate how the documented seasonal trends in modern soils can inform paleo-applications, by considering carbonate formation depth and predicted ground heating effect. These paleosol results are best explained by a MAAT of ∼27 °C with annual temperature seasonality of 25 °C.

Monitoring agricultural field trafficability using Sentinel-1

The use of heavy mobile machinery in agriculture for tillage and harvesting is now indispensable since it facilitates farming over large areas. However, one of the impacts of regular and prolonged use of heavy mobile machinery is soil compaction. To help minimize this harmful effect, trafficability of agricultural fields needs to be determined. Soil moisture acts as one of the dominant controls for field trafficability. Therefore satellites such as Sentinel-1, which is one source of spatio-temporal soil moisture information, could be useful in assessing trafficable conditions. One limitation of satellite-derived soil moisture is that only the upper surface layer is mapped. In this study, we determined the feasibility of Sentinel-1 surface soil moisture to monitor trafficability over 2016–2017. We first determined coupled conditions when surface soil moisture is a good indicator for values at the subsurface. We applied a probabilistic approach to determine trafficability using extensive in situ measurements of penetration resistance and surface soil moisture over a variety of crops. Trafficability is expressed as the probability that penetration resistance will exceed a threshold, for a given soil moisture value. Furthermore, we investigated the variability encountered from these measurements to gain insights on other temporal controls. Our results show coupled conditions for soil moisture ≥0.19 cm3 cm−3 and there is an almost 1:1 correspondence between surface and subsurface values. For decoupled conditions, values at the subsurface can be two times more than the surface. An increase in penetration resistance variability coincided with the maturity of crops for cultivated fields. Aside from soil moisture, root growth may have a significant impact on the temporal variability of soil's penetration resistance. The status of trafficability can be monitored through the high temporal resolution of Sentinel-1. However, aggregation to coarser resolutions maybe necessary as its original 10 m resolution may be suboptimal, based on validation against in situ measurements. Days favorable for traffic were observed in early spring. This information can aid farmers in the timing of tillage activities or for water managers in deciding to adjust water levels to meet agricultural demands.

Spatial-temporal variability of the fluctuation of soil temperature in the Babao River Basin, Northwest China

The Babao River Basin is the “water tower” of the Heihe River Basin. The combination of vulnerable ecosystems and inhospitable natural environments substantially restricts the existence of humans and the sustainable development of society and environment in the Heihe River Basin. Soil temperature (ST) is a critical soil variable that could affect a series of physical, chemical and biological soil processes, which is the guarantee of water conservation and vegetation growth in this region. To measure the temporal variation and spatial pattern of ST fluctuation in the Babao River Basin, fluctuation of ST at various depths were analyzed with ST data at depths of 4, 10 and 20 cm using classical statistical methods and permutation entropy. The study results show the following: 1) There are variations of ST at different depths, although ST followed an obvious seasonal law. ST at shallower depths is higher than at deeper depths in summer, and vice versa in winter. The difference of ST between different depths is close to zero when ST is near 5°C in March or -5°C in September. 2) In spring, ST at the shallower depths becomes higher than at deeper depths as soon as ST is above -5°C; this is reversed in autumn when ST is below 5°C. ST at a soil depth of 4 cm is the first to change, followed by ST at 10 and 20 cm, and the time that ST reaches the same level is delayed for 10–15 days. In chilling and warming seasons, September and February are, respectively, the months when ST at various depths are similar. 3) The average PE values of ST for 17 sites at 4 cm are 0.765 in spring >0.764 in summer >0.735 in autumn >0.723 in winter, which implies the complicated degree of fluctuations of ST. 4) For the variation of ST at different depths, it appears that Max, Ranges, Average and the Standard Deviation of ST decrease by depth increments in soil. Surface soil is more complicated because ST fluctuation at shallower depths is more pronounced and random. The average PE value of ST for 17 sites are 0.863 at a depth of 4 cm >0.818 at 10 cm >0.744 at 20 cm. 5) For the variation of ST at different elevations, it appears that Max, Ranges, Average, Standard Deviation and ST fluctuation decrease with increasing elevation at the same soil depth. And with the increase of elevation, the decrease rates of Max, Range, Average, Standard Deviation at 4 cm are -0.89 °C/100 m, -0.94°C/100 m, -0.43°C/100 m, and -0.25°C/100 m, respectively. In addition, this correlation decreased with the increase of soil depth. 6) Significant correlation between PE values of ST at depths of 4, 10 and 20 cm can easily be found. This finding implies that temperature can easily be transmitted within soil at depths between 4 and 20 cm. 7) For the variation of ST on shady slope and sunny slope sides, it appears that the PE values of ST at 4, 10 and 20 cm for 8 sites located on shady slope side are 0.868, 0.824 and 0.776, respectively, whereas they are 0.858, 0.810 and 0.716 for 9 sites located on sunny slope side.

Thermal performance analysis of slinky-coil ground-air heat exchanger system with sand-bentonite as backfilling material

The ground-air heat exchanger (GAHE) is the promising passive technique for building heating/cooling, but due to its high installation cost (mainly pipe cost and excavation cost), it could not become popular. The required length of pipe can be reduced by using thermally enhanced backfilling material (BFM), while, the length of the trench can be reduced by using slinky-coil pipe layout. In the present study, an experimental laboratory setup of GAHE system has been developed with a slinky-coil pipe layout and sand-bentonite as BFM. For this, a flexible PVC pipe of 75 mm diameter and 30 m length, has been arranged in slinky-coil pattern and installed horizontally in a soil box of 10.2 m length. For the study, variation in soil temperature (23 °C–27 °C), inlet air temperature (38 °C–46 °C), air flow velocity (5 m/s–20 m/s) and soil conditions (dry and wet), have been considered. Study reveals that a drop-in air temperature as high as 18.7 °C at 30 m pipe length (trench length of 10.2 m) can be achieved with soil at a temperature of 27 °C and inlet air temperature of 46 °C. The study also revealed that the pipe length could be reduced by 20% with wet sand-bentonite as compared to dry sand-bentonite.

Microspatial Differences in Soil Temperature Cause Phenology Change on Par with Long-Term Climate Warming in Salt Marshes

Phenology studies mostly focus on variation across time or landscapes. However, phenology can vary at fine spatial scales, and these differences may be as important as long-term change from climate warming. We used high-frequency “PhenoCam” data to examine phenology of Spartina alterniflora, a foundation species native to salt marshes on the US East and Gulf coasts, and a common colonizer elsewhere. We examined phenology across three microhabitats from 2013 to 2017 and used this information to create the first spring green-up model for S. alterniflora. We then compared modern spatial variation to that exhibited over a 60-year climate record. Marsh interior plants initiated spring growth 17 days earlier than channel edge plants and spent 35 days more in the green-up phenophase and 25 days less in the maturity phenophase. The start of green-up varied by 17 days among 3 years. The best spring green-up model was based on winter soil total growing degree days. Across microhabitats, spring green-up differences were caused by small elevation changes (15 cm) that drove soil temperature variation of 0.8°C. Preliminary evidence indicated that high winter belowground biomass depletion triggered early green-up. Long-term change was similar: winter soil temperatures warmed 1.7 ± 0.3°C since 1958, and green-up advanced 11 ± 6 days, whereas contemporary microhabitat differences were 17 ± 4 days. Incorporating local spatial variation into plant phenology models may provide an early warning of climate vulnerability and improve understanding of ecosystem-scale productivity. Microscale phenology variation likely exists in other systems and has been unappreciated.

Performance evaluation of Earth to Air Heat Exchange (EAHE) used for indoor ventilation during winter in severe cold regions

Earth to air heat exchanger (EAHE) is an efficient method for providing conditioned air. Study was conducted to explore the potential of applying EAHE in preheating fresh air in severe cold regions. A double-layer EAHE and a heat recovery unit (HRU) were combined to undertake the heating load. Performance of EAHE was detailed discussed. Experiment was carried out between Jan. 4th to Apr. 20th, 2017 (local heating season), with primary focuses on variations of air temperature, airflow rate, heating capacity and soil temperature. Analyses showed EAHE could provide an average temperature promotion of 12.4 °C under heating condition. Average heating capacity of EAHE was 4665 W while average power consumption was 130 W, which brought a considerably high average heating coefficient of performance (COP) of 29.7. At the end of heating season, due to hysteresis of soil temperature, EAHE operated under cooling mode and average cooling capacity was 2243 W. Besides, temperature distribution of surrounding soil was studied. Soil temperature variation related closely to operation mode and inlet air temperature. Influence of operation decreased along with the distance away from pipe surface. Soil temperature can recover to some extent during non-work time, which indicated proper arrangement of run schedule could support long-term reliable operation.

Microbial Diversity in Bulk and Rhizosphere Soil of Ranunculus glacialis Along a High-Alpine Altitudinal Gradient.

Serving as “natural laboratories”, altitudinal gradients can be used to study changes in the distribution of microorganisms in response to changing environmental conditions that typically occur over short geographical distances. Besides, rhizosphere zones of plants are known to be hot-spots for microbial diversity and to contain different microbial communities when compared with surrounding bulk soil. To discriminate the effects of altitude and plants, we investigated the microbial communities in the rhizosphere of Ranunculus glacialis and bulk soil along a high-alpine altitudinal gradient (2,600–3,400 m a.s.l.). The research area of this study was Mount (Mt.) “Schrankogel” in the Central Alps of Tyrol (Austria). Our results point to significantly different microbial diversities and community compositions in the different altitudinal belts. In the case of prokaryotes, environmental parameters could explain 41% of the total variation of soil communities, with pH and temperature being the strongest influencing factors. Comparing the effects derived from fraction (bulk vs. rhizosphere soil) and environmental factors, the effects of the roots of R. glacialis accounted for about one third of the explained variation. Fungal communities on the other hand were nearly exclusively influenced by environmental parameters accounting for 37.4% of the total variation. Both, for altitudinal zones as well as for bulk and rhizosphere fractions a couple of very specific biomarker taxa could be identified. Generally, the patterns of abundance of several taxa did not follow a steady increased or decreased trend along the altitudinal gradient but in many cases a maximal or minimal occurrence was established at mid-altitudes (3,000–3,100 m). This mid-altitudinal zone is a transition zone (the so-called alpine-nival ecotone) between the (lower) alpine grassland/tundra zone and the (upper) sparsely vegetated nival zone and was shown to correspond with the summer snow line. Climate change and the associated increase in temperature will shift this transition zone and thus, might also shift the described microbial patterns and biomarkers.

Variations and drivers of methane fluxes from a rice-wheat rotation agroecosystem in eastern China at seasonal and diurnal scales

The paddy rice fields act as an important anthropogenic source of methane (CH4) to the atmosphere. The study of pattern, magnitude, and environmental controls of CH4 emissions are still insufficient due to limited measurements and understand of underlying drivers for variations of CH4 fluxes at different temporal scales. In this study, CH4 fluxes from a rice-wheat rotation agroecosystem in eastern China were continuously measured using the eddy covariance technique. The diurnal and seasonal variations of CH4 flux and potential controlling factors in 2016 were analyzed using wavelet coherence, conditional Granger causality, correlation analysis and path analysis methods. CH4 fluxes showed distinguishable diurnal variations with single peaks during 13: 00–16: 00 local time. At the diurnal timescale, gross primary productivity (GPP) regulates CH4 fluxes after accounting for the effects of latent heat flux (LE), air temperature (TA), and soil temperature (TS) on CH4 fluxes. LE mirrored the diurnal pattern of CH4 fluxes when the effects of TA and TS on CH4 fluxes were considered. Daily CH4 fluxes exhibited large seasonal variations, with the largest daily CH4 flux of 1191.78 mg C-CH4 m−2 d−1 on 29 July 2016. The daily CH4 fluxes were continuously low in the growing season of wheat, and sharply increased from very low values in late June to peaks in late July and early August, and then gradually decreased to low values at the end of the rice growing season in late November and early December. Correlation analysis and path analysis showed that seasonal variations of soil temperature, air temperature, and GPP had strong effects on daily CH4 fluxes during pre-panicle initiation of the rice growing season, while soil temperature and leaf area index (LAI) had very strong effects on daily CH4 fluxes during the post-panicle initiation stage. The total of CH4 fluxes from the rice-wheat rotation agroecosystem into the atmosphere amounted to 58.08 ± 9.87 g C m−2 in 2016, and the annual net carbon (C) budget and greenhouse gas (GHG) budget were 163.50 ± 9.87 g C m−2 and 2322.53 ± 329.00 g CO2eq m−2, respectively. This study represents a comprehensive assessment of fluxes and drivers of CH4 from a rice-wheat rotation agroecosystem at different timescales. Additionally, the consecutive data of CH4 emission in this region will also useful for model calibration and validation.