Increased Soil Temperature Research Articles

Effects of winter soil warming on crop biomass carbon loss from organic matter degradation

Global warming poses an unprecedented threat to agroecosystems. Although temperature increases are more pronounced during winter than in other seasons, the impact of winter warming on crop biomass carbon has not been elucidated. Here we integrate global observational data with a decade-long field experiment to uncover a significant negative correlation between winter soil temperature and crop biomass carbon. For every degree Celsius increase in winter soil temperature, straw and grain biomass carbon decreased by 6.6 ( ± 1.7) g kg-1 and 10.2 ( ± 2.3) g kg-1, respectively. This decline is primarily attributed to the loss of soil organic matter and micronutrients induced by warming. Ignoring the adverse effects of winter warming on crop biomass carbon could result in an overestimation of total food production by 4% to 19% under future warming scenarios. Our research highlights the critical need to incorporate winter warming into agricultural productivity models for more effective climate adaptation strategies.

Improving yield and irrigation water productivity of green beans under water stress with agricultural solid waste-based material of compacted rice straw as a sustainable organic soil mulch

AbstractThis research aimed at water saving in irrigation by applying deficit irrigation using two strategies, standard drip and partial root drying (PRD), while applying organic and plastic mulch over two growing seasons of green beans. A field experiment was conducted in 2022 and 2023, using four irrigation treatments supplying 100% of the irrigation requirement (IRg), 75% IRg, 50% IRg, and 50% IRg—PRD, and four soil mulching treatments: uncovered soil (UC), plastic mulch (PM), rice straw mulch (RSM), and compacted rice straw mulch (CRSM). The combined effect of deficit irrigation strategies and soil mulching showed that the maximum irrigation water productivity (IWP) of 5.56 kg m−3 was achieved under 50% IRg—PRD & CRSM for both growing seasons, followed by 50% IRg—PRD & RSM and 50% IRg—PRD & PM, with 5.19 and 4.96 kg m−3, respectively. The highest yield of 8936 kg ha−1 was achieved with 50% IRg—PRD & CRSM, followed by 8914 kg ha−1 and 8898 kg ha−1 with 100% IRg & CRSM and 75% IRg & CRSM, respectively. The lowest yield of 6009 kg ha−1 was obtained with 50% IRg & UC. The highest soil moisture content was observed under 100% IRg & CRSM. The application of organic mulches was found to be particularly effective in conserving soil moisture due to enhanced infiltration, improved retention capacity, and suppression of weed growth, ultimately fostering optimal crop development and higher yield. The results of soil temperature variations beneath soil mulches showed that CRSM is effective in alleviating plant water stress, lowering the temperature below the cover and reducing water loss through evaporation from the soil surface. The combination of 50% IRg—PRD & CRSM produced plants with enhanced plant height, fresh and dry weight, leaf area, pod length, and green bean weight, as well as the highest vegetative growth indices. Generally, the organic mulching increased soil temperature, soil moisture, IWP, and green bean production.

Evaluation of nature-based climate solutions for agricultural landscapes in the Galápagos Islands

The Galápagos Islands are highly vulnerable to climate and environmental change, and nature-based solutions can help local communities adapt local agricultural systems. Through a comparative analysis, we evaluated the effects of three land management strategies on soil temperature, soil water availability and storage, and carbon stocks in Santa Cruz Island (Galápagos Archipelago). We installed six monitoring sites that consisted of two replicates per pathway: (i) the avoided loss of tropical forest, (ii) the conservation of scattered trees and living fences in at-risk agroforestry system, and (iii) the increase in biomass after a reduction of the grazing intensity. The monitoring sites were equipped with a dense network of rain gauges, air temperature and relative humidity sensors, and capacitance/frequency probes that registered volumetric water content and soil temperature. After pedological characterization of the soil profiles, the soil physico-chemical and hydrophysical properties were determined in laboratory. Over a period of 30 months (July 2019 to December 2021), hydrometeorological and soil environmental data were collected.We assessed differences in soil temperature, moisture availability and soil organic carbon content between native forests, sites under traditional agroforestry and under passive restoration. Forest soils were 12 % cooler;, and soil moisture under forest was 20 % higher than in parcels with silvopastural management. Forest soils had a lower dry bulk density, lower saturated hydraulic conductivity and higher water retention capacity in comparison with the other two management types. In silvopastural systems, a decrease of grazing intensity had a positive effect on soil carbon stocks, that were about 50 % higher than in soils under traditional management. This study shows that avoided loss of tropical forest within an agricultural landscape is a promising strategy to mitigate increasing soil temperatures, agricultural drought, and decline in soil organic carbon content. Continued monitoring of the experimental sites is necessary to corroborate the findings of this investigation at longer temporal scales.

ИЗУЧЕНИЕ ВЗАИМОСВЯЗЕЙ МЕЖДУ ГЛУБИНОЙ, СПОСОБАМИ ОБРАБОТКИ ПОЧВЫ И УРОЖАЙНОСТЬЮ КАРТОФЕЛЯ В ГОРНОЙ ЗОНЕ РСО-АЛАНИЯ

Depth and methods of soil cultivation for potatoes are among the most important agrotechnical techniques that allow increasing the yield of tubers without significant additional costs. The studies were conducted from 2020 to 2023, in the mountain-meadow subalpine zone in the Dargavs basin of the Republic of North Ossetia-Alania at an altitude of 1450 m above sea level (Dargavs village). The soil of the experimental site belongs to the mountain-meadow subalpine leached with a humus-illuvial horizon loamy on the eluvium of clay shale. Meteorological conditions during the years of the studies were noted as contrasting. Temperature conditions in the spring were relatively favorable, but during the flowering phase a decrease in air humidity and an increase in air and soil temperature were noted. Potatoes of the Farn variety were planted in the first ten days of May, harvested in the second ten days of September. Moldboard-less tillage methods do not significantly affect soil moisture, accumulation of available nutrients, crop yield and its quality compared to moldboard ones, but weed infestation increases. Plowing of mountain chernozems of the Republic of North Ossetia-Alania should be carried out to a depth of no more than 25 cm. Increasing the plowing depth to 35 cm or decreasing it to 15 cm causes a decrease in crop yield (subsoil tillage). Economic efficiency with moldboard plowing to a depth of 25 cm: profit from sales per 1 ha amounted to 283.1 thousand rubles. Increasing the plowing depth to 35 cm reduced profit to 56.1 thousand rubles, and decreasing it to 15 cm to 52.2 thousand rubles. The level of economic profitability amounted to 141.4; 165.7 and 147.2 %, respectively. When applying fertilizers at a dose of N60P60K60 and cultivating the soil with a flat cutter to a depth of 25 cm, the profit amounted to 247.1 thousand rubles per 1 ha with an economic profitability of 152.2 %.

Effects of Wildfire and Logging on Soil CO2 Efflux in Scots Pine Forests of Siberia

Wildfires and logging play an important role in regulating soil carbon fluxes in forest ecosystems. In Siberia, large areas are disturbed by fires and logging annually. Climate change and increasing anthropogenic pressure have resulted in the expansion of disturbed areas in recent decades. However, few studies have focused on the effects of these disturbances on soil CO2 efflux in the vast Siberian areas. The objective of our research was to evaluate differences in CO2 efflux from soils to the atmosphere between undisturbed sites and sites affected by wildfire and logging in Scots pine forests of southern Siberia. We examined 35 plots (undisturbed forest, burned forest, logged plots, and logged and burned plots) on six study sites in the Angara region and four sites in the Zabaikal region. Soil CO2 efflux was measured using an LI-800 infrared gas analyzer. We found that both fire and logging significantly reduced soil efflux in the first years after a disturbance due to a reduction in vegetation biomass and consumption of the forest floor. We found a substantially lower CO2 efflux in forests burned by high-severity fires (74% less compared to undisturbed forests) than in forests burned by moderate-severity (60% less) and low-severity (37% less) fires. Clearcut logging resulted in 6–60% lower soil CO2 efflux at most study sites, while multiple disturbances (logging and fire) had 48–94% lower efflux. The soil efflux rate increased exponentially with increasing soil temperature in undisturbed Scots pine forests (p < 0.001) and on logged plots (p < 0.03), while an inverse relationship to soil temperature was observed in burned forests (p < 0.03). We also found a positive relationship (R = 0.60–0.83, p < 0.001) between ground cover depth and soil CO2 efflux across all the plots studied. Our results demonstrate the importance of disturbance factors in the assessment of regional and global carbon fluxes. The drastic changes in CO2 flux rates following fire and logging should be incorporated into carbon balance models to improve their reliability in a changing environment.

Differential Responses of Soil Nitrogen Forms to Climate Warming in Castanopsis hystrix and Quercus aliena Forests of China

Climate warming impacts soil nitrogen cycling in forest ecosystems, thus influencing their productivity, but this has not yet been sufficiently studied. Experiments commenced in January 2012 in a subtropical Castanopsis hystrix Hook. f. and Thomson ex A. DC. plantation and in May 2011 in a temperate Quercus aliena Blume forest, China. Four treatments were established comprising trenching, artificial warming (up to 2 °C), artificial warming + trenching, and untreated control plots. The plots were 2 × 3 m in size. In 2021 and 2022, soil nitrogen mineralization, soil nutrient availability, fine root biomass and microbial biomass were measured at 0–20 cm soil depth in 6 replicate plots per treatment. Warming significantly increased soil temperature in both forests. In the C. hystrix plantation, warming significantly increased available phosphorus (AP) and fine root biomass (FRB), but it did not affect soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP) and their ratios. Warming depressed the net mineralization rate (NMR) and net ammonification rate (NAR) of the C. hystrix plantation, probably because the competition for nitrogen uptake by fine roots and microorganisms increased, thus decreasing substrates for nitrogen mineralization and ammonification processes. Trenching and warming + trenching increased the net nitrification rate (NNR), which might be related to decreased NH4+-N absorption of trees in the trenched plots and the increased microbial activity involved in soil nitrification. In the Q. aliena forest, warming significantly increased NH4+-N, MBC/MBN, Root C/N, Root N/P, and decreased pH, MBN, MBN/MBP and Root P; and there was no effect of trenching. Notably, the NAR, NNR and NMR were largely unaffected by long-term warming. We attributed this to the negative effect of increasing NH4+-N and decreasing MBN/MBP offsetting the positive effect of soil warming. This study highlights the vulnerability of subtropical forest stands to long-term warming due to decreased soil N mineralization and increased NO3−-N leaching. In contrast, the soil N cycle in the temperate forest was more resilient to a decade of continuous warming.

Characterization and Performance Evaluation of Liquid Biodegradable Mulch Films and Its Effects on Peanut Cultivation.

With the development of material science and increasing awareness of ecological environmental protection, liquid biodegradable mulch films (LBDMs) have garnered significant public interest. In this research, new LBDMs were developed using hydrophobically modified polymer materials, surfactants, and photosensitive catalysts. Characterization by scanning electron microscopy (SEM) revealed good material compatibility. LBDMs exhibited excellent wettability and degradability, effectively covering soil surfaces and enhancing soil moisture conservation, with a degradation rate of 76.09% after 80 days of burial. The field performance experiment was conducted over two consecutive years, 2021 and 2022, to assess differences in soil temperature and moisture, peanut agronomic traits, pod traits, and yield under four treatments: non-mulching (CK), LBDMs, clear polyethylene mulch films (CPEMs), and black polyethylene mulch films (BPEMs). LBDMs increased soil temperature by 0.56 °C and soil moisture by 19.25%, accelerated the seedling stage by 4-to-6 days, and improved the average emergence rate by 15.91%. Furthermore, LBDMs significantly promoted peanut growth, and it increased yield by 14.34% compared to CK. LBDMs performed comparably to the two types of PE films in maintaining soil conditions and different crop phenotype traits, including plant height, branch number, yield, and quality, and they even outperformed PE films in productivity per plant and 100-kernel weight. These findings suggest that LBDMs are a promising eco-friendly alternative to traditional PE films.

Microtopographic effect on soil temperature during a burn by shifting cultivation in a tropical rain forest

Fire is an important component of shifting cultivation systems. Although its effects on soil properties depend on its severity and duration, few studies have measured soil temperature during burns at different depths and in relation to topography in tropical forests. Frequent rain keeps the soil moist in these ecosystems, but soil moisture does not only depend on precipitation but also on relief position. Here we monitor soil temperature at 1 and 10 cm depth before the burn along elevation gradients of three logged hillsides to establish the daily temperature variation, and to compare it with the soil temperature under forested sites and during the burn. Additionally, moisture content and physicochemical properties of the soil were measured before and after the burn.Results before the burn indicate a larger daily temperature amplitude in logged versus forested areas, and specially at crests and shoulder positions in comparison to backslopes and toeslopes. The fire increased soil temperature only in 1 cm depth, and for less than 40 degrees at most of the sites. Soil moisture content was negatively correlated with maximum temperature during the burn, however, also fuel loads and litter thickness determined fire intensity, with the spatial distribution of these variables being unrelated to topography. Nutrient contents changed only in the litter layer, in which C and N diminished by 35 % and 24 %, respectively, while total Ca, Mg, K and P increased by 210, 202, 318, 235 % respectively. We conclude that soil moisture contents contributed to maintain fire intensity low at the studied site.

Direct and Remote Sensing Monitoring of Plant Salinity Stress in a Coastal Back-Barrier Environment: Mediterranean Pine Forest Stress and Mortality as a Case Study

The increase in atmospheric and soil temperatures in recent decades has led to unfavorable conditions for plants in many Mediterranean coastal environments. A typical example can be found along the coast of the Campania region in Italy, within the “Volturno Licola Falciano Natural Reserve”, where a pine forest suffered a dramatic loss of trees in 2021. New pines were planted in 2023 to replace the dead ones, with a larger tree layout and interspersed with Mediterranean bushes to replace the dead pine forest. A direct (in situ) monitoring program was planned to analyze the determinants of the pine salinity stress, coupled with Sentinel-2 L2A data; in particular, multispectral indices NDVI and NDMI were provided by the EU Copernicus service for plant status and water stress level information. Both the vadose zone and shallow groundwater were monitored with continuous logging probes. Vadose zone monitoring indicated that salinity peaked at a 30 cm soil depth, with values up to 1.9 g/L. These harsh conditions, combined with air temperatures reaching peaks of more than 40 °C, created severe difficulties for pine growth. The results of the shallow groundwater monitoring showed that the groundwater salinity was low (0.35–0.4 g/L) near the shoreline since the dune environment allowed rapid rainwater infiltration, preventing seawater intrusion. Meanwhile, salinity increased inland, reaching a peak at the end of the summer, with values up to 2.8 g/L. In November 2023, salts from storm-borne aerosols (“sea spray”) deposited on the soil caused the sea-facing portion of the newly planted pines to dry out. Differently, the pioneer vegetation of the Mediterranean dunes, directly facing the sea, was not affected by the massive deposition of sea spray. The NDMI and NDVI data were useful in distinguishing the old pine trees suffering from increasing stress and final death but were not accurate in detecting the stress conditions of newly planted, still rather short pine trees because their spectral reflectance largely interfered with the adjacent shrub growth. The proposed coupling of direct and remote sensing monitoring was successful and could be applied to detect the main drivers of plant stress in many other Mediterranean coastal environments.

Comparative analysis of water-use strategies in three subtropical mangrove species: a study of sap flow and gas exchange monitoring.

Water-use strategies play a crucial role in the adaptive capabilities of mangroves to the saline intertidal conditions, yet the intricacies of daily water-use patterns in mangrove species, which are pivotal for maintaining water balance, remain poorly understood. In this comprehensive study, we aimed to clarify the water use strategies of three co-occurring mangrove species, Avicennia marina, Aegiceras corniculatum and Kandelia obovata, through stem sap flow monitoring, leaf gas exchange and stem diameter change measurements. Our findings revealed that the daily sap flow density of Avicennia and Aegiceras reached the peak about 1 h earlier than that of Kandelia. When transpiration was strong, Kandelia and Aegiceras used stem storage to meet water demand, while Avicennia synchronized stem water storage. These three mangrove species adopted cross-peak water used and unique stem water storage to regulate their water balance. In Kandelia, the daily sap flow in per sapwood area was significantly lower, while water-use efficiency was significantly higher than those of Avicennia and Aegiceras, indicating that Kandelia adopted a more conservative and efficient water-use strategy. Sap flow in Avicennia was the most sensitive to environmental changes, while Kandelia limited water dissipation by tightly controlling stomata. Meteorological factors (photosynthetically active radiation, vapor pressure deficit and air temperature) were the main driving factors of sap flow. The increase of soil temperature can promote the water use of mangrove species, while the increase of salinity resulted in more conservative water use. Our results highlight the diversity of daily water-use strategies among the three co-occurring mangrove species, pinpointing Kandelia as the most adaptive at navigating the changing conditions of intertidal habitats in the future climate. In conclusion, our findings provide a mesoscale perspective on water-use characteristics of mangroves and also provides theoretical basis for mangroves afforestation and ecological restoration.

Wildfire effects on mercury fate in soils of North-Western Siberia

Arctic soils store 49 Gg mercury (Hg) – an extremely toxic heavy metal, whereas soil Hg can be released to the atmosphere by wildfires. For the first time we investigated the effects of wildfires on the fate of soil Hg in North-Western (NW) Siberia based on GIS maps of areas burned during the last 38 years and a field paired comparison of unburned and burned areas in tundra (mosses, lichens, some grasses, and shrubs) and forest-tundra (multi-layered canopy of larch trees, shrubs, mosses, and lichens). These field surveys were deepened by soil controlled burning to assess the Hg losses from organic horizon and mineral soil. The soil Hg stocks in the organic horizon and in the top 10 cm of the mineral soil were 3.3 ± 0.6 and 16 ± 3 mg Hg m−2 for unburned tundra and forest-tundra, respectively. After the burning by wildfires, the soil Hg stocks decreased to 2.4 ± 0.1 and 6.6 ± 0.2 mg Hg m−2 for tundra and forest-tundra, respectively. By the averages annual burned areas in NW Siberia 527 km2, wildfires in tundra and forest-tundra released 0.19 and 2.9 Mg soil Hg per year, respectively, corresponding to 28 % and 59 % of the initial soil Hg stocks. These direct effects of wildfires on Hg volatilization are raised by indirect post-pyrogenic consequences on Hg fate triggered by the vegetation succession and adsorption of atmospheric Hg on the surface of charred biomass. Charred lichens and trees accumulated 4–16 times more Hg compared to the living biomass. Blackened burned vegetation and soil reduced surface albedo and slowly increased soil temperatures in Arctic after wildfires. This created favorable conditions for seeding grasses and shrubs after wildfire and transformed burned high-latitude ecosystems into greener areas, increasing their capacity to trap atmospheric Hg by vegetation, which partly compensate the burning losses of soil Hg.

The impacts of film mulching and ridging on N2O emissions, relevant functional genes, and microbial communities in rain-fed potato fields

Rain-fed potato (Solanum tuberosum) fields in drylands significantly contribute to nitrous oxide (N2O) emissions, making them an important focus of agricultural greenhouse gas research. Film mulching and ridging are key agricultural methods in potato cultivation. Investigating the impact of these methods on N2O emissions, nitrifying/denitrifying functional genes, and microbial communities can provide a theoretical basis for soil emission reduction and more sustainable dryland agriculture. We examine the effects of flat tillage with mulching, ridge tillage with mulching, flat tillage without mulching, and ridge tillage without mulching, on potato fields under natural rainfall conditions in Wuchuan County, China. N2O emission fluxes were monitored using a static (dark) chamber and gas chromatography. Real-time quantitative PCR (q-PCR) was used to quantify abundances of nitrifying and denitrifying bacteria related to N2O emissions at various potato-growth stages. Illumina high-throughput sequencing was used to investigate microbial community structure by targeting 16S rRNA genes; related soil elements (soil temperatures and moisture) are analyzed. Mulching and ridging indirectly influence N2O emissions, nitrifying/denitrifying functional gene copy numbers, and microbial community structure by altering soil temperature and moisture. Cumulative N2O emissions and emission intensity were both consistently higher in ridge tillage with mulching during the potato-growing period. Ammonia-oxidizing archaea are the main microorganisms that control N2O emissions, with nitrification-coupled denitrification also being an important mechanism contributing to high N2O emissions during soil dry–wet cycles. Increased soil temperature and moisture elevated N2O emissions and functional gene copy numbers. The combination of mulching and ridging effectively uses the characteristics of both practices, making Nitrospira the dominant genus, and significantly increases N2O emissions.

Effect of Buried Straw Bioreactor Technology on CO2 Efflux and Indian Cowpea Yields

This study evaluates the efficacy of buried straw bioreactor (SBR) technology in enhancing soil properties, CO2 efflux, and crop yield, specifically focusing on Indian cowpea cultivation within a greenhouse environment. Conducted at the Yuxi Demonstration Park in Fujian, China, the experiment utilized a randomized block design incorporating seven treatments with varying straw application rates (4.5, 6, and 7.5 kg m−2) and burial depths (20 and 30 cm) alongside a control group. The investigation revealed that SBR technology significantly increased soil temperature, CO2 efflux, soil total nitrogen (TN), and total organic carbon (TOC), contributing to a marked improvement in the biomass of Indian cowpea roots, stems, and leaves. Notably, the optimal results were observed with 7.5 kg m−2 straw applied at a 20 cm depth, enhancing soil temperature by 1.5–2.0 °C and multiplying cowpea biomass by 2.1–6.4 times relative to the control. This treatment also led to the highest increases in soil TOC and CO2 efflux, demonstrating the potential of SBR technology for carbon sequestration and suggesting its application as a sustainable agricultural practice in cold regions to ameliorate the soil’s physical and nutritional characteristics, thus supporting enhanced crop production. The study underscores SBR technology’s role in addressing the challenge of agricultural waste through the effective reuse of crop straw, promoting the circular development of agriculture while safeguarding the ecological environment.

Variation in near-surface soil temperature drives plant assemblage differentiation across aspect.

Quantifying assemblage variation across environmental gradients provides insight into the ecological and evolutionary mechanisms that differentiate assemblages locally within a larger climate regime. We assessed how vascular plant functional composition and diversity varied across microenvironment to identify ecological differences in assemblages in a mountainous fieldsite in northeastern Utah, USA. Then, we looked at how life-history strategies and information about phylogenetic differences affect the relationship between functional metrics and environment. We found less functionally dispersed assemblages that were shorter and more resource-conservative on south-facing slopes where intra-annual soil temperature was hotter and more variable. In contrast, we found more functionally dispersed assemblages, that were taller and more resource-acquisitive on north-facing slopes where intra-annual temperature was cooler and less variable. Herbaceous and woody perennials drove these trends. Additionally, including information about phylogenetic differences in a dispersion metric indicated that phylogeny accounts for traits we did not measure. At this fieldsite, soil temperature acts as an environmental filter across aspect. If soil temperature increases and becomes more variable, intra-annually, the function of north- versus south-facing assemblages may be at risk for contrasting reasons. On south-facing slopes, assemblages may not have the variance in functional diversity needed to respond to more intense, stressful conditions. Conversely, assemblages on north-facing slopes may not have the resource-conservative strategies needed to persist if temperatures become hotter and more variable intra-annually. Given these results, we advocate for the inclusion of aspect differentiation in studies seeking to understand species and assemblage shifts in response to changing climate conditions.

Enhancing stand establishment and yield formation of cotton with multiple drip irrigation during emergence in saline fields of Southern Xinjiang

ContextFlooding irrigation prior to sowing during the winter or spring seasons has been widely employed to mitigate soil salinity and generate adequate soil moisture for cotton seedling emergence in saline fields. In an effort to conserve water, a technique known as "dry sowing and wet emergence" has been utilized in arid regions of Northern Xinjiang, China, where the soil is not irrigated before sowing, and a single drip irrigation is applied to facilitate cotton emergence immediately after sowing. However, the successful implementation of this technique has not been achieved due to high soil salinity in Southern Xinjiang, China. In light of these challenges, we hypothesize that modifying the traditional "dry sowing and wet emergence" technique from a one-time irrigation to multiple irrigations during the seedling stage could improve the microenvironment of the root-zone soil, thereby mitigating salinity stress and promoting seedling emergence and stand establishment. MethodWe conducted a two-year field experiment employing a randomized block experimental design to assess the impacts of various irrigation methods during the seedling stage on soil microenvironment, seedling emergence, stand establishment, plant physiological response to salinity stress, and yield formation of cotton. The experiment encompassed three treatments, including pre-sowing flood irrigation (flood irrigation), the traditional single drip irrigation for dry sowing and wet emergence (single drip irrigation), and the modified dry sowing and wet emergence with three rounds of drip irrigation (multiple drip irrigation). ResultsMultiple drip irrigation resulted in consistently higher soil temperatures during the period of 5–30 days after sowing (DAS), lower soil salinity from 15 to 30 DAS, and also maintained relatively higher soil moisture levels than single drip irrigation between 20 and 30 DAS. In contrast to flood irrigation, multiple drip irrigation led to an increase in soil temperature from 5 to 30 DAS and a reduction in soil salinity levels during the period of 15–30 DAS. Conversely, single drip irrigation led to a decrease in soil salinity during 5–10 DAS, but a substantial increase in soil salinity and decrease in soil moisture from 20 to 30 DAS. Multiple drip irrigations used only 40 % of the irrigation amount needed for flood irrigation but achieved comparable seedling emergence and stand establishment rates. Compared to single drip irrigation, multiple drip irrigations decreased Na+ and malondialdehyde (MDA) content in the leaves by 21.7 % and 15.6 %, and increased photosynthetic (Pn) rate and stand establishment rate by 22.0 % and 36.3 %, respectively. Moreover, multiple drip irrigation produced seedcotton yields equal to those of flood irrigation, with an increase of 24.2 % compared to single drip irrigation. ConclusionsThe results demonstrate that multiple drip irrigations enhance seedcotton yield through improving stand establishment compared to single drip irrigation. This improvement is attributed to reduced salinity stress, as evidenced by the decreased soil salinity, Na+ content, and MDA content in the leaves when using multiple drip irrigation during seedling emergence. Therefore, multiple drip irrigation is a promising technique for promoting cotton seedling emergence and stand establishment in saline fields of Southern Xinjiang and other cotton-growing areas with similar ecological conditions.

Study on the effect of ground stratification on heat transfer of vertical ground heat exchangers in lateritic clay areas

The potential effect of ground stratification on the efficiency of ground heat exchangers (GHEs) in lateritic clay regions remains unclear. Model experiments were conducted to investigate the effects of soil dry density, water content, and ground stratification on the heat exchange between GHEs and the surrounding lateritic clay. A 3D numerical model accounting for ground stratification was proposed and validated using experimental data. The model further examined the influence of soil moisture on the dynamic heat exchange process. The findings of the model experiments indicate that the heat from buried pipes increase soil temperature by 12.8 % when the initial water content of lateritic clay (with dry density of 1.1 g/cm3) rises from 5 % to 28 %. Raising the dry density from 1.1 to 1.3 g/cm3 at 28 % water content results in a 7.5 % temperature increase. The initial soil moisture and density have negligible effects on the temperature gradient within 18 cm of the geothermal pipes. The temperature increased faster in the sand layer than in the lateritic clay layer owing to the difference in thermal properties. The impact of heat produced by GHEs on the temperature field in homogeneous soil layers differs considerably from that in stratified soil layers. The 3D numerical model provided a good fit for the measured soil temperature in the stratified soil layer, including the soil temperature variation at the layered interface. The simulation results showed that for dry and saturated strata, the temperature of the lateritic clay around the GHEs increased with increasing initial stratum moisture. For unsaturated lateritic clay strata, because of the possible impacts of moisture and heat coupling migration, the temperature of the stratum around the GHEs first increased and subsequently decreased as the initial stratum moisture was enhanced.

Improved heat transfer mathematical model forpyramid shaped seasonal heat storage water pit and the influence of boundary conditions

Seasonal heat storage can make use of urban waste heat for low-carbon heating throughout the year. Previous models for pyramid shaped water pit have limited adaptability and ignore the impact of soil temperature in the early stages of operation on the performance of water pits. This article combines two classic mathematical models to establish a mathematical model that can adapt to various sizes of inverted pyramid shaped water pits. The validation of this model was conducted using experimental data from 60000 m3 water pit of Dronninglund, and the influence of boundary conditions for this module were calculated and discussed. The results showed that the root mean square errors of the simulated top, bottom, and average temperature of the water pit were 3.07 °C, 2.39 °C, and 1.37 °C, with relative deviation ratios of 4.25 %, 2.27 %, and 6.62 %, respectively. Furthermore, it was found that for every 5 °C increase in the set average soil temperature, the storage efficiency of the water pits increases by 0.4 %∼0.5 %. In the case of common top insulation of the water pit, the total heat loss at the top, side walls, and bottom are 66.83 %, 31.8 %, 1.37 %. While considering comprehensive insulation in all directions, the heat loss rate for the top, side walls, and bottom are similar with the former, being 67.84 %, 30.79 %, and 1.37 %, respectively. The proposal and findings of this article provide a basis for simplified optimization planning and design of large-scale seasonal heat storage systems.

Numerical analysis of transient soil temperature variation during wildfires

In this study, transient behavior of soil temperature during large forest fires is analyzed using the Comsol© software package. The increase in soil temperature during large wildfires can be very critical, especially when oil or gas pipelines have been laid at a certain depth in the soil mainly near forests. During forest fires, the temperature of the soil surface can reach extreme levels that penetrate deep into the ground if the fire is not extinguished within a short time. This increase in temperature on the soil surface can lead to extremely dangerous situations if the laying depth of the pipeline is not sufficient, as the heat conducted through the soil causes the surface temperature of the pipeline and therefore that of the fluid inside it to reach even high values. This can lead to a sudden rupture of the pipeline and ultimately lead to catastrophic consequences. The present study is conservative due to the assumptions made in structuring the numerical model. However, it is believed to provide invaluable information about the considerations in selecting gas pipeline locations and pipeline laying depths taking into account extreme temperatures due to wildfires. There is limited research on the topic regarding the time dependent conduction heat transfer through soils as a result of fires, but only in one dimension. Current study, being multi-dimensional, is therefore believed to be novel in the field. Future research could include extensive study on the energy content of different species of forest trees, considering their time-dependent heat release rates (HRR) during a forest fire, as well as experimental work if a field setup could be designed.

Bare Patches Created by Plateau Pikas Contribute to Warming Permafrost on the Tibet Plateau

AbstractPlateau pikas, small mammals native to the Qinghai‐Tibet Plateau (QTP), create bare patches through burrowing. No previous assessment exists on their impact on permafrost. This study fills this gap by simulating hypothetical scenarios in the Three Rivers Headwaters Region of the QTP using the Noah‐MP model for the plant growing seasons during 2015–2018. Our findings reveal a significant increase in soil temperature in the active layer due to pika‐induced bare patches, particularly during July–August. The average temperature rise at 2.5 cm depth was 0.36°C in permafrost regions and 0.29°C in seasonally frozen ground regions during August. Minimal impact on unfrozen water content was observed, with a slight increase in deep soil layers in permafrost regions, and negligible in seasonally frozen areas. These findings underscore the previously unexplored influence of pika burrowing on permafrost temperature, suggesting a potential risk of accelerating permafrost degradation, especially in permafrost‐dominated regions.

Soil warming effects on the transpiration of trees and shrubs in a subtropical secondary forest: A manipulative experiment

The climate warming can increase the productivity of some species while decrease that of others, therefore, knowledge of species-specific responses to warming is helpful to understand the possible trajectory of forest ecosystems. Despite the importance of the subtropical secondary broadleaf forests developed from afforestation in South China, our understanding of how the transpiration of trees and shrubs co-growing in these forests responds to soil warming is limited. To explore the effects of soil warming on transpiration and associated ecophysiological traits of trees and shrubs in wet and dry seasons, as well as to clarify respective contributions of trees and shrubs transpiration to the stand total, we conducted a manipulative experiment of soil warming (+2 ℃, WA) and control (CK) in a subtropical secondary broadleaf forest in South China, and continuously monitored the transpiration (based on sap flow) of trees, Schima superba and Acacia auriculiformis, and that (derived from leaf temperature and microclimate) of shrubs, Psychotria asiatica and Castanopsis chinensis, from 2021 to 2022. We also measured leaf water potentials, leaf nutrient status, and δ13C-derived intrinsic water use efficiency (WUEi). Soil warming did not significantly alter the transpiration of trees, with the exception of A. auriculiformis in 2022, whereas it notably increased transpiration of both shrubs. We attributed the stimulation of shrubs’ transpiration mainly to the more favorable leaf water potentials under warming condition. Due to the increased transpiration, the contribution of shrubs to stand transpiration was consequently increased, highlighting the potential role of shrubs in the hydrological dynamics of forest ecosystems. Additionally, the WUEi, soil main macro-nutrients, and leaf nutritional status of all species were not significantly affected by soil warming. These findings indicated that the carbon-water exchange and nutrient status of the studied plants can be maintained even when exposed to moderate increases in soil temperature and relatively drier condition, reflecting the resilience of the subtropical secondary broadleaf forest to possible climate warming. Further research on the interaction and competition of co-existing trees and shrubs under soil warming will improve the prediction of forest dynamics under future climate change, which benefits the efforts to conserve such forests in order to address the environmental pressure in the region.