Increased Soil Temperature Research Articles

The Effects of Hedgerows Shading on Soil Temperature and Gravimetric Soil Water Content

This study sets out to examine the effects of hedgerow shading on soil physical properties, specifically soil gravimetric water content and soil temperature. Analyses of both soil parameters were conducted at two locations with different shade proportion. The aim of the study was to address the links between hedgerow shading and basic physical soil properties which could be significant both for agricultural production and for ecological processes in agroecosystems. At both locations, soil samples and measurements were taken at different distances from hedgerow and in different time intervals. Diurnal shading variation at certain distances from the hedgerow on Location 1 and 2 was calculated with the software toll for Arboriculturists. At Location 1 shading is consistently high throughout the year, ranging from 76 to 100%. In contrast, shading at Location 2 varies from 1 to 25%. The results reveal that hedgerows at Location 1, do not have a statistically significant impact on gravimetric soil water content and soil temperature across the entire plot surface. Additionally, the percentage of shading is only marginally decreases with distance. Conversely, Location 2 exhibits an increase in soil temperature and a slight but (non-significant) decrease in soil gravimetric watercontent as the distance from the hedgerow increases., The total mean shading at Location 2 is considerably lower compared to Location 1, and the shading percentage declines more at the distance from the hedgerow increases. Overall, lower soil temperatures and higher gravimetric soil water content where observed at the more shaded Location 1. The research outcomes are helpful in agricultural production planning as well as in the evaluation of hedgerows for the needs of agricultural policy.

Plant litter loss exacerbates drought influences on grasslands.

Plant litter is known to affect soil, community, and ecosystem properties. However, we know little about the capacity of litter to modulate grassland responses to climate change. Using a 7-yr litter removal experiment in a semiarid grassland, here we examined how litter removal interacts with a 2-yr drought to affect soil environments, plant community composition, and ecosystem function. Litter loss exacerbates the negative impacts of drought on grasslands. Litter removal increased soil temperature but reduced soil moisture and nitrogen mineralization, which substantially increased the negative impacts of drought on primary productivity and the abundance of perennial rhizomatous graminoids. Moreover, complete litter removal shifted plant community composition from grass-dominated to forb-dominated and reduced species and functional group asynchrony, resulting in lower ecosystem temporal stability. Our results suggest that ecological processes that lead to reduction in litter, such as burning, grazing, and haying, may render ecosystems more vulnerable and impair the capacity of grasslands to withstand drought events.

Research on renewable energy coupling system based on medium-deep ground temperature attenuation

Medium-deep geothermal has large reserves, a high temperature, a high heat flow density, and other characteristics, but the traditional medium-deep ground heat pump system have long relied on heating from the ground, and soil temperature decreases annually. Using a community building heating system as an example, from a point of view of heat accumulation or not, this article examines the design of a photovoltaic photothermal coupled medium-deep ground source heat pump system (PV/T-GSHP) and a photovoltaic-assisted medium-deep ground source heat pump coupled air source heat pump system (PVGSHP-ASHP). First, the operational performance of a typical GSHP system was compared to that of the PV/T-GSHP and PVGSHP-ASHP systems, both of which were built using TRNSYS. Second, the energy balance and electrical consumption of each system were compared. Finally, the effect of the PV/T-GSHP system’s key parameters and the different ASHP load ratios in the PVGSHP-ASHP system on soil temperature were analyzed. The results showed that after 20 years of operation, the average soil temperature decreased from 38.29 °C to 36.89 °C for the GSHP system, resulting in a decrease in the performance coefficient of the ground source heat pump and the system performance coefficient. The PV/T-GSHP system can address the issue of declining soil temperature with an increase in soil temperature of 0.09 °C. The PVGSHP-ASHP system can mitigate the issue of decreasing soil temperature. The PVGSHP-ASHP system is better than the PV/T-GSHP system in terms of electricity economy. In the PV/T-GSHP system, the larger PV/T component area of similar structures, the smaller flow rate of the heat collector pump, and the volume, inclination, and set temperature of the heat storage tank that are more suitable for the system can achieve higher soil temperatures. As the air-source load ratio increases, the rate at which the soil temperature in the PVGSHP-ASHP system decreases progressively decelerates.

Responses of winter wheat yield and water productivity to sowing time and plastic mulching in the Loess Plateau

On the Loess Plateau, unfavorable late-sowing conditions often arise due to late harvests from the previous season or excessive rainfall during the sowing season, which can delay seed germination, reduce tiller numbers, and decrease winter wheat yields. Few studies have explored whether plastic mulching (PM) can mitigate the adverse effects of late sowing. Consequently, we conducted a 3-year field experiment from 2017 to 2020 on the Loess Plateau combining two mulching conditions [PM and no mulching (NPM)] and three sowing times (normal, 10-day late, and 20-day late sowing). We investigated the combined influence of sowing time and mulching conditions on soil hydrothermal status, crop water productivity (WP), and yield. The results revealed that delayed sowing significantly prolonged emergence times and decreased tiller numbers, leaf area index (LAI), root biomass, and aboveground biomass (AGB). The PM increased soil temperatures, advancing wheat emergence and increasing tiller numbers. Plants under PM had higher LAI, root biomass, and AGB than those under NPM. Moreover, PM reduced ineffective transpiration by accelerating the degradation of ineffective tillers, resulting in higher yields without a corresponding increase in evapotranspiration. The beneficial effects extended to spike numbers, thousand-grain weight, and harvest index. Specifically, PM combined with 10-day late sowing increased yield by 12.8 % compared to NPM combined with normal sowing. Furthermore, under 20-day late sowing, PM mitigated yield losses, reducing them from a 28.7 % decline under NPM to a 12.8 % decline when compared to normal sowing under NPM. We conclude that PM completed compensated for the yield loss under 10-day late sowing and partially alleviated losses under 20-day late sowing. Therefore, combining 10-day late sowing (accumulated air temperature before winter > 430 °C d) with PM was the optimal approach for simultaneously improving yield and WP in winter wheat seasons with unfavorable late-sowing conditions.

The effect of high altitude on ephedrine content and metabolic variations in two species of Ephedra.

Ephedra is an important plant in Chinese medicine; however, there are few reports on two species of Ephedra which are distributed at high altitudes from 3000 to 5200 meters. We collected a total of 84 individuals representing five Ephedra gerardiana and nine Ephedra saxatilis populations respectively located from 3158 to 5200 meters altitude, and determined the relative content of 213 metabolites using UHPLC-MS/MS (Ultra-High-Performance Liquid Chromatography-tandem mass spectrometry). 37 Chemical compositions were annotated using the KEGG (Kyoto Encyclopaedia of Genes and Genomes) database. From the top five significant enrichments in metabolic KEGG pathway analysis, we found a total of 166 compounds belonging to phenylpropanoids, 123 flavonoids, 67 metabolites carried by ABC transporters, and 61 in purine metabolism. We identified the top 8 altitude-related compounds in two species. Ephedrine and pseudoephedrine were found to be associated with altitude in both E. saxatilis and E. gerardiana. To verify which environmental factors influenced the metabolic content, the soil moisture and temperature of each population site were collected, and quantitative analysis of ephedrine and pseudoephedrine was performed using UHPLC-MS (Ultra-High-Performance liquid chromatography-tandem mass spectrometry). After detection, soil moisture ranged from 0.074 to 0.177 mm3/mm3, and temperature ranged from 9.7°C to 23.9°C. The content of ephedrine ranged from (0.84 ± 0.49)% to (2.01 ± 0.41)% in E. saxatilis, which was positively correlated with soil moisture; the content of pseudoephedrine ranged from (0.72 ± 0.45)% to (1.11 ± 0.57)% and was negatively correlated with soil moisture. In contrast to these results, in E. gerardiana, the content of ephedrine and pseudoephedrine was negatively correlated with soil moisture. Furthermore, the trends of alkaloid contents in two kinds of Ephedra were similar when the temperature was lower than 17°C even if the sum was various. With the increase in soil moisture and temperature, the total alkaloid content of E. saxatilis was higher than that of E. gerardiana. When the soil moisture was lower, the alkaloid content of the two Ephedra species was higher. These results provide useful data for the future separation of new compounds, and for seed homogeneous growth to determine artificial breeding of Ephedra located at high altitudes.

The long-term effects of thinning on soil respiration vary with season in subalpine spruce plantations

Thinning is a principal silvicultural practice in temperate plantations with potential impacts on soil respiration (Rs). However, most of the existing measurements of Rs dynamics after thinning have been performed during the growing season, while those in the nongrowing season have been seldom determined, even though recent evidence demonstrates that the nongrowing season Rs occupied a considerable proportion of the annual carbon (C) budgets in temperate forests. Here, we investigated the long-term (17 years) impacts of thinning on Rs in middle-aged subalpine spruce plantations in northwestern China. We found that thinning significantly (p < 0.001) increased Rs from 3.00 to 4.18 μmol m−2 s−1 in the growing season while significantly (p < 0.001) decreasing Rs from 1.05 to 0.90 μmol m−2 s−1 in the nongrowing season; additionally, thinning had no significant (p = 0.0989) effect on the Q10 value (temperature sensitivity of Rs) in the growing season, with values ranging from 2.10 to 2.44, while it significantly (p < 0.01) increased the Q10 value from 2.91 to 3.48 in the nongrowing season. In the growing season, increased nitrate nitrogen due to elevated soil moisture (SM) played a fundamental role in stimulating Rs by improving microbial biomass (MB) and fine root biomass, and increased soil temperature (ST) also contributed to the increases in MB and Rs. However, these variables and pathways were not applicable in the nongrowing season, when decreased dissolved organic C induced by decreased ST explained most of the decline in MB and Rs. Our results revealed that the long-term effects of thinning on the nongrowing season Rs were completely different from those in the growing seasons in subalpine spruce plantations. Furthermore, the greatly increased Q10 value in the nongrowing season indicated that a substantial increase in Rs can be expected in subalpine forests after thinning due to nongrowing season warming at high altitudes.

The regulation of gross nitrogen transformation rates in greenhouse soil cultivated with cucumber plants under elevated atmospheric [CO2] and increased soil temperature

Climate change scenarios forecast both increase in atmospheric CO2 concentration ([CO2]) and temperature. Elevated [CO2] (e[CO2]) and soil temperature (eST) significantly increased plant growth and nitrogen (N) uptake. However, studies on the combined effect of these factors on soil N transformation and microbial community are scarce in agricultural intensification. In the present work, we cultivated cucumber plants under e[CO2] or/and eST, followed by a paired labeling 15N tracer experiment (15NH4NO3 and NH415NO3) to quantify soil gross N transformation rates. Results showed that e[CO2] decreased soil gross N nitrification rate, indicated by a decline in ammonia-oxidizing bacteria (amoA-AOB) and nitrite oxidoreductase alpha subunit (nxrA) gene copy numbers, and changed microbial taxonomic composition under ambient soil temperature (aST). Furthermore, eST increased chitinase gene (chiA) and amoA-AOB gene copy numbers and alpha diversity and changed the microbial taxonomic composition to improve soil gross N mineralization and nitrification rates. The combination of e[CO2] and eST promoted soil gross N mineralization, nitrification, and immobilization rates compared with ambient [CO2] and aST. The study showed that the combination of e[CO2] and eST increased the primary gross N transformation rates and accelerated soil N circulation, which could ensure plant N demand. Therefore, combining e[CO2] and eST provided a promising way to help cultivators promote vegetable growth in winter, mitigate soil N loss, and achieve sustainable development in greenhouse vegetable cultivation.

Review of the Impact of Drip Irrigation Mulching on Soil Characteristics and Efficiency in Water Usage

Vegetable growth and productivity are influenced by watering techniques and different kinds of mulch. The current study reviewed drip irrigation that used different irrigation volumes (V, 0.7V, and 0.9V) in drip treatments. Transparent mulch resulted in higher soil temperatures compared to black mulch. The study or situation involved the use of black mulch, which is a type of mulching material often used in agriculture. The use of black mulch caused the soil temperature to rise. The increase in soil temperature ranged from 2.6 to 5.5 degrees Celsius (°C). This indicates a considerable temperature difference. The moisture content in the non-mulched plots was found to be higher than that in the mulched ones. The utilization of plastic mulch resulted in water conservation ranging from 26% to 36% across various treatment conditions. In comparison to the control treatment, all treatment groups that used black mulch saw increased yields. By maximising water use, the use of mulching and drip irrigation in vegetable cultivation offers the potential to lower cultivation costs.

Subsurface irrigation with ceramic emitters improves greenhouse tomato yield and resource utilization efficiency by stabilizing soil hydrothermal status

Maintaining a stable and suitable soil hydrothermal status is crucial for promoting the high quality and yield of greenhouse vegetables throughout the year. Irrigation by regulating soil moisture changes to soil heat capacity is an effective measure to alleviate the fluctuation of soil hydrothermal environment caused by interannual solar radiation. To investigate the soil hydrothermal status of greenhouse tomatoes under subsurface irrigation with ceramic emitters (SICE) and its impact on tomato growth and yield, we conducted a two-season greenhouse experiment with subsurface drip irrigation (SDI) as a control. The results showed that soil hydrothermal changes under SICE fluctuated less with time in the autumn and spring experiment than SDI; SICE could increase soil temperature in the tomato root zone profile in winter and decrease the profile temperature in summer. This indicates that SICE could reduce the direct effect of air temperature on soil temperature and maintain a stable and suitable soil hydrothermal condition. Furthermore, the underground and vegetative biomass of SICE stopped increasing with the rapid growth of water and heat resources to the inflection point. They shifted to the accumulation of reproductive biomass. However, the vegetative biomass of SDI continued to increase in the late stage of water and heat resources. Therefore, under similar total biomass conditions, SICE obtained more output. SICE increased tomato yields by 11.60 in autumn and 8.36 t hm−2 in spring compared to SDI. The regulation mechanism also improved the hydrothermal resource utilization efficiency under SICE, with SICE increasing water and heat resource use efficiency by 24.04 % and 3.73 % (in autumn) and 9.80 % and 6.00 % (in spring), respectively, compared to SDI. We conclude that SICE is an effective and promising irrigation method for greenhouse tomato cultivation for stabilizing the soil water and heat environment, promoting yield, and improving the utilization rate of solar radiation.

Effects of rainfall amount and frequencies on soil net nitrogen mineralization in Gahai wet meadow in the Qinghai-Tibetan Plateau

Global climate change has led to a significant increase in the frequency of extreme rainfall events in the Qinghai-Tibetan Plateau (QTP), thus potentially increasing the annual rainfall amounts and, consequently, affecting the net soil nitrogen (N) mineralization process. However, few studies on the responses of the soil net N mineralization rates to the increases in rainfall amounts and frequencies in alpine wet meadows have been carried out. Therefore, the present study aims to assess the effects of rainfall frequency and amount changes on the N fixation capacity of wet meadow soils by varying the rainfall frequency and amount in the Gahai wet meadow in the northeastern margin of the QTP during the plant-growing season in 2019. The treatment scenarios consisted of ambient rain (CK) and supplementary irrigation at a rate of 25 mm, with different irrigation frequencies, namely weekly (DF1), biweekly (DF2), every three weeks (DF3), and every four weeks (DF4). According to the obtained results, the increased rainfall frequency and amount decreased the soil mineral N stock and increased the aboveground vegetation biomass (AB) amounts and soil water contents in the wet meadows of the QTP. Ammonium (NH4+-N) and nitrate N (NO3–-N) contributed similarly to the mineral N contents. However, the ammonification process played a major role in the soil mineralization process. The effects of increasing rainfall amount and frequency on N mineralization showed seasonal variations. The N mineralization rate showed a single-peaked curve with increasing soil temperature during the rapid vegetation growth phase, reaching the highest value in August. In addition, the N mineralization rates showed significant positive correlations with soil temperatures and NH4+-N contents and a significant negative correlation with AB (P < 0.05). The results of this study demonstrated the key role of low extreme rainfall event frequencies in increasing the net soil N mineralization rates in the vegetation growing season, which is detrimental to soil N accumulation, thereby affecting the effectiveness of soil N contents.

Effects of Climate Change on Soil Organic Matter C and H Isotope Composition in a Mediterranean Savannah (Dehesa): An Assessment Using Py-CSIA.

Dehesas are Mediterranean agro-sylvo-pastoral systems sensitive to climate change. Extreme climate conditions forecasted for Mediterranean areas may change soil C turnover, which is of relevance for soil biogeochemistry modeling. The effect of climate change on soil organic matter (SOM) is investigated in a field experiment mimicking environmental conditions of global change scenarios (soil temperature increase, +2-3 °C, W; rainfall exclusion, 30%, D; a combination of both, W+D). Pyrolysis-compound-specific isotope analysis (Py-CSIA) is used for C and H isotope characterization of SOM compounds and to forecast trends exerted by the induced climate shift. After 2.5 years, significant δ13C and δ2H isotopic enrichments were detected. Observed short- and mid-chain n-alkane δ13C shifts point to an increased microbial SOM reworking in the W treatment; a 2H enrichment of up to 40‰ of lignin methoxyphenols was found when combining W+D treatments under the tree canopy, probably related to H fractionation due to increased soil water evapotranspiration. Our findings indicate that the effect of the tree canopy drives SOM dynamics in dehesas and that, in the short term, foreseen climate change scenarios will exert changes in the SOM dynamics comprising the biogeochemical C and H cycles.

CO&lt;sub&gt;2&lt;/sub&gt; Emission by Soils of the Ecotone Zone in the North of Western Siberia

The study area in the North of Western Siberia is located at the southern limit of the distribution of surficial permafrost in the ecotone zone on the border of taiga and southern tundra. Area is characterized by the contrasting landscapes: pine forests with Albic Podzol; palsa with Histic Oxyaquic Turbic Cryosol and bog ecosystems with Fibric Histosol. The objectives of the study included evaluation the values of CO2 emission (SR) by soils of key landscapes in the growing seasons of 2019–2022, and evaluation the factors of spatial variability of this indicator and its interannual variability. The study included analysis of the RS database (static closed chamber method) and soil hydrothermal parameters for four years in August. In the absence of trends in changing climatic parameters over the past 10 years, a gradual increase in soil temperature in all landscapes and an increase in the depth of thawing in palsa were observed. These changes were not accompanied by significant changes in the SR value. It averaged from 485 to 540 mgCO2/(m2 h) in forest ecosystems, from 150 to 255 mgCO2/(m2 h) in the peat-bog complex with high coefficients of spatial variability. High values of SR in forest ecosystems are determined by a favorable hydrothermal regime, high reserves of root biomass, and good water-physical properties. Part of the CO2 produced by palsa soils is transported by supra-permafrost waters and released from the surface of bog soils. Soil temperature, regulated by seasonal thawing, was a significant predictor of the spatial variability of SR on the soils of the palsa-bog complex.

Methane Producing and Oxidizing Microorganisms Display a High Resilience to Drought in a Swedish Hemi‐Boreal Mire

AbstractAn increased frequency of droughts due to anthropogenic climate change can lead to considerable stress for soil microorganisms and their functioning within northern peatlands. A better understanding of the diversity and relative abundance of methane producing and oxidizing taxa, and their functional genes, can help predict the functional potential of peatlands and how the microorganisms respond to disturbances such as drought. To address knowledge gaps in the understanding of how functional genetic diversity shifts under drought conditions, we investigated a hemi boreal mire in Southern Sweden. Environmental parameters, including soil and air temperature, precipitation, and water table depth, as well as methane flux data were collected during the summer of 2017 under typical growing conditions, and in 2018 during a drought. In addition, the diversity and composition of genes encoding for methane metabolism were determined using the captured metagenomics technique. During drought we observed a substantial increase in air and soil temperature, reduced precipitation, and a lower water table depth. Taxonomic and functional gene composition significantly changed during the drought, while diversity indices, such as alpha and beta diversity, remained similar. These results indicate that methane producing and oxidizing microbial communities, and their functional genes, displayed a resilience to drought with specific genera having the ability to outcompete others under stress. Furthermore, our results show that although methane emissions are substantially reduced during drought, we can expect to see a shift toward more resilient methanogens and methanotrophs under future climate conditions.

Study on two nematode species suggests climate change will inflict greater crop damage

Food security has become one of the greatest challenges of the millennium and it is predicted to be exacerbated by climate change due to the adverse effects of soil temperature on crop productivity. Although plant-parasitic nematodes are one of the most important limiting factors of agricultural production, the fate of soil temperature in their biology is not fully understood. Here we present the effects of soil temperature on survival, reproduction, virulence, and disease severity from the perspective of two nematode species Rotylenchulus reniformis and Meloidogyne floridensis. The two nematode species were purposefully selected to represent a significant threat to annual and perennial crops. We employed novel approaches of direct as well as indirect heat exposure to evaluate nematode biology. The direct heat exposure assay involved the exposure of nematodes to hot water in a heating block at 32, 33, and 34 °C for 7 h, and subsequent evaluation of their survival after 18 h. The indirect exposure assay employed a commercial heat mat to raise soil temperatures to 32, 33, and 34 °C for 7 h during the daytime, and subsequent evaluation of nematode reproduction, virulence, and/or disease severity over the period of 6 weeks after inoculation. When directly exposed to hot water at 34 °C, the survival of R. reniformis increased by 10% while the survival of M. floridensis decreased by 12% relative to that at 32 °C. Upon increasing soil temperatures from 32 to 34 °C, the reproduction of R. reniformis and M. floridensis decreased by 49% and 53%, respectively. A significant reduction in the reproduction of M. floridensis occurred when soil temperature was increased from 33 to 34 °C, however, the same condition did not significantly affect R. reniformis reproduction suggesting the latter species has a greater ability to adapt to increasing soil temperature. Additionally, the virulence of R. reniformis was greater at 33 and 34 °C relative to that at 30 °C indicating increased aggressiveness of the nematode at higher soil temperatures. The virulence of M. floridensis appeared to be decreased as evident from increased root biomass when soil temperature was increased from 32 to 34 °C, however, the greater root biomass may have resulted from increased root galling at the higher temperatures. Results of the current study suggest that while higher soil temperatures due to climate change may lead to reduced nematode reproduction, crop losses will likely increase due to increased nematode virulence. Through the current study, we report practical evidence of the quantitative impact of climate change on the biology of plant-parasitic nematodes. Further studies involving a wider range of temperature and exposure time are needed to better understand nematode biology under climate change.

Effects of Climate Change and Nitrogen Addition on Carbon Loss in Alpine Wetland of Qinghai–Tibet Plateau

Soil microorganisms and soil organic carbon (SOC) play important roles in ecosystem cycling, but there is a lack of clarity about the effects of nitrogen addition on soil microorganisms and SOC, as well as the key microbial taxa that influence SOC. This study was conducted in the alpine wetland of Xiaopo Lake in the Qinghai Lake basin, using NH4NO3 as the nitrogen source, three nitrogen addition gradients (N2: 2 g/m2, N5: 5 g/m2, N10: 10 g/m2), and a blank control treatment (N0: 0 g/m2), with three replicate experiments for each treatment. The main findings were as follows: (1) Both increased soil temperature and decreased precipitation reduced SOC content. SOC content gradually decreased with increasing nitrogen concentration; SOC was reduced by 3.36–29.54% and 8.57–26.66% at 0–15 cm and 15–30 cm soil depths, respectively. (2) Proteobacteria, Chloroflexi, Acidobacteria, and Actinobacteria were the main dominant species, and their changes determined the changes in the entire bacterial community. The relative abundance of Proteobacteria and Actinobacteria decreased under nitrogen addition; Acidobacteria increased significantly; and Chloroflexi did not change significantly. The overall abundance and diversity of soil bacteria showed an increasing trend. The number of soil bacteria is a key factor affecting SOC content, and an increase in the number and diversity of soil bacteria enhances their decomposition capacity, and thus, reduces SOC content. (3) Increased soil temperatures and decreased precipitation are associated with decreased SOC and are the main climatic factors affecting SOC. This study provides a reference for the rational utilization and management of wetland ecosystems under climate change.

Effects of different ratios of organic and inorganic fertilizer on rice yield and soil physicochemical properties under conventional and controlled irrigation conditions

AbstractWater and fertilizer management practices are critical in rice fields. Excessive application of fertilizer adversely affects soil physicochemical properties, consequently decreasing yield. A greenhouse experiment was conducted to determine the effect of high (L1), medium (L2) and low organic fertilizer ratios (L3) as well as chemical fertilizer alone (L4) and no fertilization (L5) under conventional (C) and controlled irrigation (M) on rice yield and soil characteristics. Statistically, the regression equation was developed by using principal component analysis to clarify the influence of different soil quality factors on rice yield. The results showed that controlled irrigation could increase soil temperature (ST), electrical conductivity (EC) and nitrogen content while decreasing soil pH. The application of organic fertilizer enhanced ST and decreased EC. Under equal nitrogen application conditions, rice yield increased with organic fertilizer application, and it was highest under L1, which was 2.7% higher than L4 and 22% higher than L5. In the case of irrigation methods, controlled irrigation application increased yield by 6% compared to conventional irrigation. The multiple linear regression equation showed that the cumulative contribution of variance of the two principal component eigenvalues reached 75%, among which soil pH, total nitrogen (TN) content and nitrate nitrogen (NO3−‐N) contributed positively to yield, while ammonium nitrogen (NH4+‐N), soil organic carbon (SOC), EC and ST showed negative effects on rice yield. Thus, our study findings can provide a scientific basis for improving management practices.

Effects of mulching types on the yield and water utilization by broomcorn millet (Panicum miliaceum): Results of a study in the Loess Plateau, China

Mulching practices have been widely adopted to improve rainfed crop productivity. However, the major resources including water, heat, and light that influenced the yield of broomcorn millet in different dryland regions have rarely been explored. A three-season field experiment with three mulching practices i.e. traditional planting with non-mulching (TP), ridge-furrow mulching system (RF), and plastic film mulching (PFM) was conducted in three semi-arid regions in the Loess Plateau, China, i.e. Guyuan city (GY), Huining county (HN), and Yulin city (YL) between 2020 and 2022 to investigate the impacts of mulching regimes on soil hydrothermal conditions, agronomic characteristics, leaf photosynthetic properties, broomcorn millet yield, and water use efficiency (WUE). Results showed that both PFM and RF treatments increased soil temperature and moisture, and enhanced dry matter accumulation by promoting leaf photosynthetic capacity and chlorophyll content, thereby improving broomcorn millet yield and WUE. PFM and RF increased the average broomcorn millet yield by 15.08% and 24.86% at GY site, 20.86% and 25.61% at HN site, and 15.75% and 25.57% at YL site, respectively, and increased the average WUE by 16.31% and 27.48% at GY site, 23.21% and 28.80% at HN site, 15.55% and 28.57% at YL site, respectively. Partial least squares path modeling analysis revealed that soil moisture was an important environmental factor in determining broomcorn millet yield. Overall, RF practice can be taken to improve the management of agricultural climate factors and maximize yield, thereby promoting the sustainable development of dryland agriculture in the Loess Plateau.

Ecological signals of arctic plant-microbe associations are consistent across eDNA and vegetation surveys

Understanding how different taxa respond to abiotic characteristics of the environment is of key interest for understanding the assembly of communities. Yet, whether eDNA data will suffice to accurately capture environmental imprints has been the topic of some debate. In this study, we characterised patterns of species occurrences and co-occurrences in Zackenberg in northeast Greenland using environmental DNA. To explore the potential for extracting ecological signals from eDNA data alone, we compared two approaches (visual vegetation surveys and soil eDNA metabarcoding) to describing plant communities and their responses to abiotic conditions. We then examined plant associations with microbes using a joint species distribution model. We found that most (68%) of plant genera were detectable by both vegetation surveys and eDNA signatures. Species-specific occurrence data revealed how plants, bacteria and fungi responded to their abiotic environment – with plants, bacteria and fungi all responding similarly to soil moisture. Nonetheless, a large proportion of fungi decreased in occurrences with increasing soil temperature. Regarding biotic associations, the nature and proportion of the plant-microbe associations detected were consistent between plant data identified via vegetation surveys and eDNA. Of pairs of plants and microbe genera showing statistically supported associations (while accounting for joint responses to the environment), plants and bacteria mainly showed negative associations, whereas plants and fungi mainly showed positive associations. Ample ecological signals detected by both vegetation surveys and by eDNA-based methods and a general correspondence in biotic associations inferred by both methods, suggested that purely eDNA-based approaches constitute a promising and easily applicable tool for studying plant-soil microbial associations in the Arctic and elsewhere.

Impact of Climate Warming on Paddy Soil Organic Carbon Change in the Sichuan Basin of China

Climate warming can increase soil temperature and lead to soil carbon release, but it can also increase soil organic carbon by increasing primary productivity. Cropland soils are considered to have a huge potential to sequester carbon; however, direct observations for the responses of cropland soil organic carbon to climate warming over broad geographic scales are rarely documented. Paddy soil is one of the important cultivated soils in China. Based on the data of 2217 sampling points obtained during the second national soil survey and the data of 2382 sampling points collected during 2017-2019, this study analyzed the change characteristics of soil organic carbon content of paddy surface soil in Sichuan Basin of China and explored the relationships between the soil organic carbon change of paddy soil and temperature, precipitation, cropland use type, fertilization intensity, and grain yield. The results showed that the content of soil organic carbon of paddy soil changed from 13.33 g·kg-1to 15.96 g·kg-1, with an increase of 2.63 g·kg-1, suggesting that soils in the Sichuan Basin have acted as a carbon sink over past 40 years. The soil organic carbon increment of paddy soil varied with different geomorphic regions and different secondary basins. The increase in SOC content in paddy soil was positively correlated with annual average temperature; negatively correlated with annual average precipitation; and initially increased and then decreased with annual average fertilizer application, annual average increase rate of fertilizer application, annual average grain yield, and annual average grain yield growth rate. The relationship between the increase in SOC content and the annual average temperature growth rate was different under different farmland utilizations, and the increase in the annual average temperature growth rate had significant effects with the increase in SOC content only on paddy-dryland rotation. These results indicate that the paddy soil organic carbon change in Sichuan Basin was co-affected by various factors, but climate warming was an important factor leading to the paddy soil organic carbon change, and its influence was controlled by the water conditions determined by farmland use.

Assessment of PAR Interception and Radiation Use Efficiency on Tomato Growth and Yield in the Upper Brahmaputra Valley Zone of Assam, India

A field experiment was conducted in Jorhat, Assam during the rabi season of 2019-20 to examine the effects of PAR interception, radiation use efficiency, and modified microclimates on tomato growth and yield. The variety Arka Rakshak was grown in split plot design with 4 dates of planting (P1: 25th October, P2: 14th November, P3: 3rd December, and P4: 8th January) in main plots and three types of mulching (M0: no mulch, M1: rice straw mulch, and M2: black polythene mulch) in sub-plots. Measurements of incident PAR (IPAR), reflected PAR (RPAR), transmitted PAR (TPAR) were taken at 10 days regular intervals. The results showed that IPAR ranged from 531 to 1431 μ mol s-1 m-2, with an average of 1140.4 μ mol s-1 m-2. RPAR varied between 41 and 285 μ mol m-2 s-1 under different microclimates. The tomato yield ranged from 76.6 to 392.6 q ha-1, with an average of 234.9 q ha-1. Planting on November 14th (P2) provided the most favorable microclimate conditions, while black polythene mulch (M2) was found to be the most suitable for crop growth, yield, and radiation use efficiency due to increased soil temperature. The study indicated that selecting the right planting date and implementing black polythene mulch can enhance tomato growth, yield, and radiation use efficiency in Upper Brahmaputra Valley Zone of Assam (Jorhat) agro-climatic condition.