Mineral Soil Research Articles

Soil carbon determination for long‐term monitoring revisited using thermo‐gravimetric analysis

AbstractSoils and the vadose zone are the major terrestrial repository of carbon (C) in the form of soil organic matter (SOM), more resistant black carbon (BC), and inorganic carbonate. Differentiating between these pools is important for assessing vulnerability to degradation and changes in the C cycle affecting soil health and climate regulation. Major monitoring programs from field to continent are now being undertaken to track changes in soil carbon (SC). Inexpensive, robust measures that can differentiate small changes in the C pools in a single measurement are highly desirable for long‐term monitoring. In this study, we assess the accuracy and precision of thermo‐gravimetric analysis (TGA) using organic matter standards, clay minerals, and soils from a national data set. We investigate the use of TGA to routinely differentiate between C pools, something no single measurement has yet achieved. Based on the kinetic nature of thermal oxidation of SC combined with the different thermodynamic stabilities of the molecules, we designed a new method to quantify the inorganic and organic SC and further separate the organic biogeochemically active SOM (as loss on ignition, LOI) from the resistant BC in soils. We analyze the TGA spectrums of a national soil monitoring data set (n = 456) and measure total carbon (TC) using thermal oxidation and also demonstrate a TC/LOI relationship of 0.55 for soils ranging from mineral soils to peat for the United Kingdom consistent with previous monitoring campaigns.

Implications of alder shrub growth for alpine tundra soil properties in Interior Alaska

ABSTRACT The increase in deciduous shrub growth in response to climate change throughout the Arctic tundra has uncertain implications, in part due to a lack of field observations. Here we investigate how increasing alder shrub growth in alpine tundra in Interior Alaska corresponds to active layer thickness and soil physical properties. We documented increased alder growth by combining biomass harvests and dendrochronology with the analysis of remotely sensed Normalized Difference Vegetation Index and fire history. Active layer thickness was measured with a tile probe and carbon and nitrogen pools were assessed via elemental analysis. Shallower organic layers under increasing alder growth indicate that nitrogen-rich, deciduous litter inputs may play a role in accelerating decomposition. Despite the observed reduction in organic carbon stocks, active layer thickness was the same under alder and adjacent graminoid tundra, implying deeper thaw of the underlying mineral soil. This study provides further evidence that the widely observed expansion of deciduous shrubs into graminoid tundra will reduce ecosystem carbon stocks and intensify soil–atmosphere thermal coupling.

Gamma radiation for the estimation of mineral soil water content in a boreal forest

Continuous monitoring of water quantities in different soil horizons is necessary to understand the behavior of infiltrated water in the soil. Under certain conditions, using measurements of natural ground gamma radiation can help us estimate soil water content measurements over a 100 m2 surface within a 15 cm depth. A CS725 sensor can provide up to four daily estimates of soil water content by detecting the natural emission of gamma radiation. However, in boreal forest environments, gamma radiation mitigated by the water in the thick humus layers (litter, fermented, and humic horizon) can bias the underlying mineral soil water content measurements. The objective of this research was to evaluate the accuracy of methods that incorporate variables describing the surface humus layer into calculations of the underlying mineral soil water content, by measuring the soil’s natural gamma emission with the CS725. Using raw gamma radiation values obtained by CS725 sensors deployed over various boreal soils, we tested two functions. The first one included variables describing the humus layer and the other excluded these variables (manufacturer’s method). The function that included the descriptive humus layer variables showed superior results compared to the function without. The results of this study suggest that the CS725 sensor can adequately estimate mineral soil water content within ±10% absolute of the reference water content when examined with the following humus variables: humus layer thickness, fractioned composition, bulk density, and linear gamma radiation attenuation.

Groundwater for drinking and industrial purposes: A study of water stability and human health risk assessment from black sand mineral rich coastal region of Kerala, India

Tempero-spatial analysis of groundwater to disseminate the level of drinking water quality and industrial suitability to meet the developmental requirement of a region is a significant area of research. Accordingly, groundwater quality and geochemical interactions prevailed in a black sand mineral rich coastal village is systematically presented in appraisal of drinking and industrial uses for economic engineering purposes. The study area focused is Alappad village, Kollam, Kerala, India has numerous ecological features in a sustainable perspective. The region is unique with placer deposits where an alluvial soil aquifer–saline water–freshwater interaction occurs. This dynamics decides the pertinent hydro geochemistry, potable and designated uses of ground water in season wise. Coastal area is hereby presented based on water quality parameters predicted with the health risk assessment model with a view on human health and cancer risk due to ions (Pb, Ni, Cu, Ba, Fe, Al, Mn, Zn) in groundwater.. To ascertain industrial usage, ground water is evaluated by Langelier saturation index (LSI), Ryznar stability index (RSI), Aggressive index (AI), Larson-Skold index (LS) and Puckorius scaling index (PSI) and inferences are complemented. Chemical weathering and evaporation processes are the natural factors controlling hydrochemistry of this aquifer. This complex coastal system has Nemerow pollution index (NPI) of moderate pollution for total dissolved ions of Fe and lesser for Cu, and Cr present in groundwater. LSI indicates, water is scale forming but non corrosive (46% in PRM, 20% in MON and 47% in POM). Water quality index (WQI) in POM (ranged 28.7–79.9) was excellent for drinking, followed by PRM (23.6–218.2) and MON (33.4–202.7) seasons. This groundwater bears temporary hardness with the dominance of Ca–Mg–HCO3 water type. Health risk assessment of non-carcinogenic risk index of trace metals (Fe, Zn, Mn, and Pb) revealed, children are at ‘low risk’ and ‘medium’ risk with Ni and Cu. The carcinogenic risk index indicated 93% of samples were high Ni induced cancer risk for children, and 87% for adults due to long term ingestion (drinking water intake) pathway. Studies specific on placer mineral deposited coastal region of India are not sufficiently reported with a focus on the above perspectives. Growing need of rare earths for material, device and energy applications, placer mineral explorations can destabilise the coastal hydrosphere. Interrelations of mineral soil – water chemistry prevailed and health hazard predicted would kindle a set of sustainable deliberations. This study summarises the drinking and industrial use of coastal groundwater for future development and human well-being on the basis of quality criteria, corrosion proneness, water stability and health risk factors.

Deciphering Biotic and Abiotic Mechanisms Underlying Straw Decomposition and Soil Organic Carbon Priming in Agriculture Soils Receiving Long-Term Fertilizers.

Straw-related carbon (C) dynamics are central for C accrual in agro-ecosystems and should be assessed by investigating their decomposition and soil organic carbon (SOC) priming effects. Our understanding of biotic and abiotic mechanisms underpinning these two C processes, however, is still not sufficiently profound. Soils that had received organic and mineral fertilizers for 26 years were sampled for a 28 day incubation experiment to assess 13C-labeled straw decomposition and SOC priming effects. On the basis of analyzing physicochemical properties, fungal taxonomic (MiSeq sequencing) and functional (metagenomics) guilds, we quantified the contributions of biotic and abiotic attributes to straw decomposition and SOC priming. Here, we propose two distinct mechanisms underlying straw decomposition and SOC priming in agriculture soils: (i) accelerated straw mineralization in manure-treated soils was mainly driven by biotic forces, while (ii) larger SOC priming in NPK-amended soils was through abiotic regulation.

Soil carbon and nitrogen contents in forest soils are related to soil texture in interaction with pH and metal cations

The aim of this study was to better understand how soil carbon (C) and nitrogen (N) contents and the C:N ratio are related to soil texture, pH, and exchangeable aluminum and calcium in forest soils.For this purpose, we studied 1992 temperate and boreal forest soils located all over Sweden. We measured organic C and N as well exchangeable aluminum, calcium, and pH in the organic layer and three depth increments in the mineral soil (down to 65 cm), and analyzed the relationship between element contents, soil texture, and soil pH as well as their interactions.Soil C concentration and the C:N ratio were negatively related to soil pH. The C concentration was on average 2.6 times higher in very acidic soils (pH ≤ 4.0) than in soils with pH > 5.0, in the uppermost 10 cm of the mineral soil. In contrast, N varied much less with pH, particularly in the organic layer, but was related to soil texture. The N concentration was 2.3 times higher in clayey and fine silty soils than in sandy soils, while the C concentration was only 1.85 times higher in clayey and fine silty soils than in sandy soils (in the uppermost 10 cm). Differences in C and N concentrations between clayey and fine silty soils compared to sandy soils were largest in the class of soils with pH > 5.0 and smallest in the class of soils with pH ≤ 4.0. Furthermore, C and N concentrations were both positively correlated with the concentration of exchangeable aluminum in the mineral soil, and these correlations were stronger in coarse-textured than in fine-textured soils. In addition, the C concentration was positively correlated with the concentration of exchangeable calcium in the organic layer.In conclusion, our results show that C concentration varied much more strongly with pH than N concentration, likely due to effects of pH on microbial respiration. The N concentration was more strongly related to soil texture than the C concentration, which is very likely due to the high charge density of organic N, which gives organic N a high affinity to adsorb to mineral surfaces. Furthermore, exchangeable aluminum seems to play an important role in the sorptive stabilization of organic matter in the mineral soil.

Assessment of degradation mechanism of imidacloprid residues in grape rhizosphere soil by UHPLC-Orbitrap™-MS and its residual impact on soil enzyme activity.

Imidacloprid (IM) is a systemic insecticide persistent in the environment and possesses a negative impact on the non-targeted ecosystem. The objective of the present study was to evaluate the dissipation and degradation mechanism of IM residues in grape rhizosphere soil and to investigate its residual effect on soil enzyme activity at different IM spiking levels. The half-life of IM residue in soil was 27, 36, and 43.5days at a spiking level of 1, 10, and 50mgkg-1, respectively following a bi-phasic first + first-order dissipation kinetics. UHPLC-Orbitrap™-MS analysis by targeted metabolomics approach revealed that IM metabolites such as IM-amine analogue, guanidine (reduction), 5-hydroxy IM (hydroxylation), IM-Urea (oxidation), reduced NO analogue of IM (oxidation), and olefin of guanidine IM (dehydrogenation) were identified and proposed the degradation mechanism in grape rhizosphere soil. Toxicity of IM residues on five extracellular enzymes, viz., dehydrogenase, acid phosphatase, alkaline phosphatase, β-glucosidase, and urease revealed that activity of dehydrogenase, acid phosphatase, and alkaline phosphatase remained unaffected at 60th day of sampling. The β-glucosidase and urease were negatively affected throughout the incubation period indicating the influence of IM residues on carbon and nitrogen mineralization in soil. Thus, long-term exposure of IM to grape rhizosphere through soil drenching could affect soil enzyme activity which has a negative effect on the soil nutrient cycle and soil microbiome.

Quantifying earthworm soil ingestion from changes in vertical bulk density profiles

Soil mixing by earthworms can have a large impact on the fate of nutrients and pollutants and on the soil's ability to sequester carbon. Nevertheless, methods to quantify earthworm ingestion and egestion under field conditions are largely lacking. Soils of the Fennoscandian tundra offer a special possibility for such quantifications, as these soils commonly lack burrowing macrofauna and exhibit a well-defined O horizon with low bulk density on top of a mineral soil with higher density. Since ingestion-egestion mixes the two soil layers, the temporal changes in the bulk density profile of such soils may be useful for estimating field ingestion rates. In this study, we applied a model for earthworm burrowing through soil ingestion to observed changes in soil densities occurring in a mesocosm experiment carried out in the arctic during four summers with intact soil. The earthworms present in the mesocosms were Aporrectodea trapezoides, Aporrectodea tuberculata, Aporrectodea rosea, Lumbricus rubellus and Lumbricus Terrestris (fourth season only). We show that changes in soil density profiles can indeed be used to infer earthworm ingestion rates that are realistic in comparison to literature values. Although uncertainties in parameter values were sometimes large, the results from this study suggest that soil turnover rates and endogeic earthworm soil ingestion rates in tundra heath and meadow soils may be as high as those reported for temperate conditions. Such large ingestion rates can explain observed large morphological changes in arctic soils where dispersing earthworms have resulted in complete inmixing of the organic layer into the mineral soil. Our approach is applicable to soil profiles with marked vertical differences in bulk density such as the soils of the Fennoscandian tundra where earthworms are currently dispersing into new areas and to layered repacked soil samples that are incubated in the field.

Study and evaluation of the effects of vegetation cover destruction on soil degradation in Middle Guinea through the application of remote sensing and and geotechnics

Soil degradation in Middle Guinea is increasing over the years. While it's good to have precautions to deal with it, it's even more important to go back to the source of the scourge in order to lessen its effects over time, or even eradicate it. At the center of the factors that are often mentioned is the destruction of the vegetation cover, and the aim of this study is to clear it (in all its forms: trees, grass, savannah, etc.) by following its variation in time [1982 and 2021] and in space. The present study was conducted by combining the remote sensing and GIS results, developed with data from geotechnical survey data and laboratory tests. On the Mali Labé Linsan axis, between [1982 and 1992], 63 % of the territory explored was occupied by fresh vegetation cover, compared to 13 % of dry vegetation, as well as 12 % of sterile soil and 12 % of sand mineral soil. For the periods [1992–2002] and [2002–2012], these same parameters increased to: 67 %; 11 %; 11 % and 11 %. The period [2012–2021] was marked by changes of 73 %; 10 %; 9 % and 9 %, respectively. The bearing capacity of soils varies from one point to another. In all six boreholes presented, their maximum values are greater than or equal to 400 Kpa (≥400 Kpa). The minimum values calculated for 2.1 ≤ B(m)≤7.3 fluctuate between 291 Kpa and 806 Kpa. The investigations carried out on this subject show that the overall movement of the positive variation of the vegetation cover in time (63 % < 67 % < 73 %) and very contrasted in space, would not be responsible for the degradations (which are local and mainly caused by erosion: wind and water). In addition, they open up to a (geoscientific and geotechnical) approach of a deep analysis, the purpose of which suggests the adoption of slab/concrete/grating foundations (depth of anchorage specific to each soil analyzed).

Disentangle the drivers of soil organic carbon mineralization and their temperature sensitivity in both topsoil and subsoil: Implication of thermal stability and chemical composition

Information about the temperature dependence of soil organic carbon (SOC) mineralization is important to predict the possible carbon (C) release from the terrestrial ecosystem facing global warming. However, the way in which SOC quality and mineral protection of SOC affects mineralization rates and their response to increasing temperature remains poorly understood. Here, we focused on investigating thermal stability and chemical composition of soils which differed greatly with the type and extent of organo-mineral associations, and revealing their implications for SOC mineralization. Chemical composition and thermal stability of SOC were analyzed with 13C nuclear magnetic resonance spectroscopy (13C NMR) and simultaneous thermogravimeteric analysis and differential scanning calorimetry (TG-DSC), respectively. Soil mineralization and its temperature sensitivity (Q10) were assessed by incubating soils at 15 and 25 °C for 90 days.Our results showed that SOC of subsoil was more biologically stable, but exhibited higher temperature sensitivity than those of topsoil. Significant differences in chemical composition and thermal stability of SOC were detected across soils developed from four parent materials but not between two soil layers, and indicators obtained from the two techniques showed apparent associations with depth-specific SOC mineralization rates. Increase in SOC mineralization rates at two incubation temperatures and two soil layers were observed when the soils were characterized by higher percentage of labile SOC fractions (i.e., O-alkyl C and organic carbon oxidized during exothermic reactions). The Q10 values of topsoil were positively and mostly related to the percentage of Alkyl C. In addition to notable relationships with chemical composition, the Q10 values of subsoil were positively correlated with Exo1/Exo2 ratios and Energy density values, and negatively correlated with TG-50. It was interesting to note that thermal stability was possibly as a function of soil texture and total oxides. Results from VPA analysis further revealed that SOC mineralization rates at two soil layers and Q10 of topsoil were mainly driven by SOC quality, while it was related to both SOC quality and chemical protection for subsoil, implying that factors controlling the temperature sensitivity of SOC mineralization were depth-specific. Altogether, substrate accessibility as a function of chemical composition and chemical protection would play vital role in determining the feedbacks of the subsoil SOC pool to the future climate warming.

Interaction of selected pesticides with mineral and organic soil components

Interaction of selected pesticides with mineral and organic soil components

Liming leads to changes in the physical properties of acidified forest soils

AbstractBackgroundForest liming is a common practice in many German forests, which aims primarily at improving soil chemical properties that have been negatively impacted by acid rain. Effects on physical functions have not yet been studied widely.AimsThe hypothesis of this study is that chemical changes after liming lead to changes in the physical properties of the humus layer and mineral soil.MethodsWe studied soil physical characteristics (water retention characteristics, air and water permeabilities, and conductivities) of limed and adjacent control plots of sandy to loamy, acidified soils under spruce and beech‐dominated stands.ResultsWe found differences between limed and control plots, especially in the humus layer and mineral top soil. Here, air capacity values (representing air‐filled macropores at −6 kPa) have experienced an increase, while available water capacities (representing the sum of dewatered mesopores between −6 and −1500 kPa) were reduced to a variable extent. These changes in pore size distributions affected gas diffusion as well as gas permeability positively. Unsaturated hydraulic conductivity was not affected. Below the top mineral soil, a tendency to a reduced macroporosity and gas permeability was observed, but no clear changes were detected.ConclusionsSmall but significant changes of soil physical properties and functions in the humus layer and top mineral soil are discussed to be an indirect effect of forest liming. Liming improves pH and nutrient availability, which in turn should have stimulated activity and abundance of soil fauna, especially earthworms. Where observed, their activity could explain the observed changes in soil physical properties. We believe that effects below the top soil might be due to mobilization and translocation of soil particles and a clogging of pores, but these depths were only studied at three plots. Compared to common liming practices, however, the investigated sites are characterized by significantly higher lime applications. The effects on practice liming areas in forestry praxis are therefore likely to be smaller than in this study.

Source or decomposition of soil organic matter: what is more important with increasing forest age in a subalpine setting?

Afforestation has been the dominant land-use change in the Swiss Alps during the last decades which has not only the potential to increase soil organic carbon sequestration, but it has also the potential to alter soil organic matter (SOM) dynamics through the vegetation shift and change in organic matter (OM) input into soils. The effects of afforestation on SOM dynamics, however, are still not fully understood as specific sources of OM and modifications of soil processes influencing decomposition and preservation remain largely unknown on alpine to subalpine slopes. Within this study we aimed to identify the potential sources and the decomposition of OM in a subalpine afforestation chrono-sequence (0–130 years) with Norway spruce (Picea abies L.) on a former pasture by using a multi-proxy molecular marker approach. We observed that leaf-derived OM plays an essential role in the pasture areas, while root-derived OM only plays a minor role in pasture and forest areas. Needle-derived OM represents the dominant source of SOM with increasing forest age, while understory shrubs and moss also contribute to the OM input in younger forest stand ages. However, needle litter and buildup of organic layers and subsequently less input of fresh OM from organic horizons to mineral soil can result in increased OM decomposition in mineral soils rather than contributing to additional SOM stabilization in mineral soils. This was most pronounced in the oldest forest stand (130-year-old) in the investigated afforestation sequence, particularly in deeper soil horizons (10–45 cm). Thereby, our study provides new insights into SOM dynamics following afforestation, especially with respect to the long-term SOM sequestration potential of afforestation of subalpine pasture soils.

Soil organic carbon stocks did not change after 130 years of afforestation on a former Swiss Alpine pasture

Abstract. Soil organic matter (SOM) plays an important role in the global carbon cycle, especially in alpine ecosystems. However, ongoing forest expansion in high-elevation systems potentially alters SOM storage through changes in organic matter (OM) inputs and microclimate. In this study, we investigated the effects of an Picea abies L. afforestation chrono-sequence (0 to 130 years) of a former subalpine pasture in Switzerland on soil organic carbon (SOC) stocks and SOM dynamics. We found that SOC stocks remained constant throughout the chrono-sequence, with comparable SOC stocks in the mineral soils after afforestation and previous pasture (SOC forest40 = 11.6 ± 1.1 kg m−2, SOC forest130 = 11.0 ± 0.3 kg m−2 and SOC pasture = 11.5 ± 0.5 kg m−2). However, including the additional carbon of the organic horizons in the forest, reaching up to 1.7 kg m−2 in the 55-year old forest, resulted in an increase in the overall SOC stocks following afforestation. We found that the soil C:N ratio in the mineral soil increased in the topsoil (0–5 cm) with increasing forest stand age, from 11.9 ± 1.3 in the pasture to 14.3 ± 1.8 in the 130-year old forest. In turn, we observed a decrease in the soil C:N ratio with increasing depth in all forest stand ages. This suggests that litter-derived organic matter (C:N from 35.1 ± 1.9 to 42.4 ± 10.8) is likely to be incorporated and translocated from the organic horizon to the mineral topsoil (0–10 cm) of the profiles. Due to the high root C:N ratio (pasture 63.5 ± 2.8 and forests between 54.7 ± 3.9 and 61.2 ± 2.9), particulate root-derived organic matter seems to have a rather small effect on forest soil C:N ratios, as well as on SOC accumulation in the mineral soil. These results suggest that, although afforestation does not change the SOC stock in the mineral soil, there is an apparent alteration in the SOM dynamics through changes in the litter composition caused by the vegetation shift. We conclude that, at our study site, spruce afforestation on a former subalpine pasture does not change the total SOC stock and that, consequently, there is no additional SOC sequestration on a decadal to centennial scale.

Unleashing the power of old maps: Extracting symbology from nineteenth century maps using convolutional neural networks to quantify modern land use on historic wetlands

Topographical maps from the nineteenth century hold significant historical and environmental value, providing insights into landscape changes over the past two centuries. These maps feature distinct symbols representing various land cover types, such as forests and wetlands, offering a unique historical perspective on land-use changes. For example, there has been a significant reduction in wetlands because of agricultural expansion and intensification which lead to biodiversity loss and increased greenhouse gas emissions globally. Our study uses U-net CNN to automatically segment wetland symbols from nineteenth century maps from hundreds of map sheets for an area of interest a large river catchment in Ireland. Extracted wetland extents were intersected with digital land cover datasets to estimate current land cover on former wetland (on both organic and mineral soils). Utilizing U-Net, we successfully automated the segmentation of wetland symbols from hundreds of nineteenth-century map sheets, focusing on a large river catchment area in Ireland. Our analysis achieved a very high F1 score of 98.2% and a Kappa of 89%. While it is challenging to verify the veracity of historical map content, the largely untapped information contained within these maps are important for understanding landscape change over time, and especially before the era of Earth observation & remote sensing. The data extracted from these sources can inform modern environmental management strategies, for example, in targeted rewetting of peatlands, or in habitat restoration.

Glucose input profit soil organic carbon mineralization and nitrogen dynamics in relation to nitrogen amended soils

Exogenous carbon (C) inputs stimulate soil organic carbon (SOC) decomposition, strongly influencing atmospheric concentrations and climate dynamics. The direction and magnitude of C decomposition depend on the C and nitrogen (N) addition, types and pattern. Despite the importance of decomposition, it remains unclear whether organic C input affects the SOC decomposition under different N-types (Ammonium Nitrate; AN, Urea; U and Ammonium Sulfate; AS). Therefore, we conducted an incubation experiment to assess glucose impact on N-treated soils at various levels (High N; HN: 50 mg/m2, Low N; LN: 05 mg/m2). The glucose input increased SOC mineralization by 38% and 35% under HN and LN, respectively. Moreover, it suppressed the concentration of NO3−-N by 35% and NH4+-N by 15% in response to HN and LN soils, respectively. Results indicated higher respiration in Urea-treated soils and elevated net total nitrogen content (TN) in AS-treated soils. AN-amended soil exhibited no notable rise in C mineralization and TN content compared to other N-type soils. Microbial biomass carbon (MBC) was higher in glucose treated soils under LN conditions than control. This could result that high N suppressed microbial N mining and enhancing SOM stability by directing microbes towards accessible C sources. Our results suggest that glucose accelerated SOC mineralization in urea-added soils and TN contents in AS-amended soils, while HN levels suppressed C release and increased TN contents in all soil types except glucose-treated soils. Thus, different N-types and levels play a key role in modulating the stability of SOC over C input.

The trend of groundwater recharge in the secondary perched reaches of the Yellow River in the past 50 years

Precipitation infiltrates into the soil or river and then percolates downward through the deeper mineral soil to the groundwater. Understanding the interactions between surface water and groundwater in the river ecosystem is crucial for supporting decision-making in eco-construction and the efficient use of water resources. In our study, the secondary perched reach of the lower Yellow River was taken as the research area. The trend analysis and correlation relationship were evaluated using the M–K significance test and gray correlation; furthermore, the groundwater recharge was quantified by Darcy‘s law and the water balance method based on 50 years of hydrological data. The results showed that 1) from 1972 to 2020, the runoff and water level of the Huayuankou hydrological station and the Jiahetan hydrological station showed a significant downward trend. 2) The calculation of the gray correlation degree method shows that the groundwater level is mainly affected by the Yellow River. The river water and groundwater levels show a significant downward trend using the M–K significance test. 3) The unit width recharge values of the secondary perched river to the groundwater in the dry year were calculated to be 566.79 and 374.13 m3/m·d, using Darcy‘s law and the water balance method, respectively, indicating that the results of the two methods are basically the same. Our findings highlight the storage capacity of groundwater and can provide support for regulation and sustainable management of water resources in the ecosystem.

Searching for identity: finding the expression of place under ground

ABSTRACTCities are increasingly looking for green solutions to urban development, such as green roofs and vertical green infrastructure, as a response to globalisation and climate change. However, while engineered topsoils are being used to support green infrastructure initiatives, the hidden layers of mineral soil and rock that give landscapes their unique shape are often ignored. This research looks at the potential of subterranean soil conditions to express regional differences and challenge global trends in soil use by engaging with the underground in Aotearoa New Zealand. It finds that the uniqueness and richness of the layers of hidden soil can lead to new ways of understanding place through texture, colour, and structure, which in turn can inform aesthetic decisions and develop authentic regional aesthetics.

Influence of Land Uses on Soil Carbon Mineralization in Selected Agro-ecological Units of South Kerala, India

Soil is a major reservoir of terrestrial carbon and it plays an important role in the global carbon cycle. The soil organic carbon (SOC) is the fundamental factor for sustainable agriculture because of the ability in maintaining the soil fertility which is critical to soil productivity. Soil carbon pool has gained paramount importance in the recent decades owing to the alarming issues of climate change and global warming. Land use change was found to have a larger net effect on SOC storage than projected climate change. Depending on the land use management practices, soils can be a net sink or source for CO2. In this regard the present study was carried out to assess the impact of different land uses on carbon storage and mineralization in soils of selected agro-ecological units of south Kerala.The agro-ecological units (AEUs) of south Kerala namely, southern coastal plain (AEU 1), Onattukara sandy plain (AEU 3), southern laterites (AEU 8), south central laterites (AEU 9) and southern and central foothills (AEU 12) were selected. In each AEU, different agricultural land use categories as described by IPCC for the carbon inventory such as, garden land (coconut), wet land (rice), fallow (uncultivated) and plantation (rubber) were also selected for the study. The potential for carbon mineralization in soil was assessed by evaluating factors such as Total organic carbon, mineralizable carbon, particulate organic carbon, global warming potential, carbon distribution, and turnover. The total organic carbon and particulate organic carbon were higher in rubber land use and AEU 12. The mineralizable C content in soil varied from 1.40 to 3.45, 1.18 to 3.41, 1.04 to 3.04, 1.23 to 3.35 and 1.01 to 3.02 mg g⁻¹ in AEU 1, 3, 8, 9 and 12 respectively. The highest value was observed from AEU 1 and rice land use. Similar trend was obtained for global warming potential of soils based on CO2 evolution which varied from 31.82 to 78.41, 26.89 to 79.02, 22.89 to 69.02, 28.03 to 76.06 and 22.96 to 68.64 in AEU 1, 3, 8, 9 and 12 respectively. The C proportion and turnover rates were in the range of 0.25 to 0.77 and 0.04 to 0.17 respectively. The C proportion was the highest in AEU 12 and rubber land use whereas the C turnover was the highest in AEU 1 and rice land use.

The use of hydromulching increases yield and quality of drought-stressed artichokes (Cynara cardunculus subsp. scolymus L. (Heigi)) by improving soil properties and plant hormone homeostasis

There exist many research papers which pointed out the positive effects of using the mulching technique in stressful conditions, showing crop productivity and physicochemical quality improvement of the product. We hypothesized that a novel organic liquid mulching formulations (hydromulching) can be used in sustainable agricultural production under drought stress through both their direct influence on physicochemical and biological soil properties as well as by their effect on plant hormonal balance leading to the improvement of crop yield and quality. Artichoke plants were grown on bare soil (BS) or mulched with traditional polyethylene (PE) or with three different types of ecological hydromulching treatments obtained from recycled additives, namely: substrate used for mushroom cultivation (MS), rice hulls (RH) and wheat straw (WS); and were subjected to optimal (100% ETc) and reduced (70% ETc) irrigation regimes. Under water limitation, soil organic matter and carbon and mineral soil concentrations increased in the hydromulched soils (by 60% on average). Mulched treatments produced the highest crop yield (by 40% on average) attributed to increased artichoke head fresh weight, giving rise to the improvement of the important physical quality parameters in artichoke: color, firmness, and size. Furthermore, hydromulched treatments induced higher content of mineral nutrients in artichoke heads, while sugar concentrations were superior in non-mulched soil due to a major exposure to water stress. This may be related to the diminished carbohydrate metabolism activity under drought stress, including notable changes in the hormonal balance. The crosstalk of growth-promoting hormones (cytokinins) with the stress-related hormone factors (ethylene precursor 1-aminocyclopropane-1-carboxylic acid) has been shown to regulate adaptive responses such as sugar osmoregulation in artichoke heads under drought stress. Altogether, these results demonstrate that hydromulching is a sustainable alternative to plastic films to cope with drought stress by improving yield and physical quality characteristics of artichoke heads and maintaining their chemical and nutritional quality over bare soil.