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17 pages, 13676 KiB

Open AccessArticle

The Characteristics of Soil C, N and P and Stoichiometric Ratios as Affected by Land-Use in a Karst Area, Southwest China

by Yang Ma, Chunlai Zhang, Hui Yang, Yikai Xu, Yan Chen and Jing Ning

Land 2023, 12(6), 1126; https://doi.org/10.3390/land12061126 - 25 May 2023

Viewed by 1098

Abstract

Chemometric analysis is often used as an effective indicator of the supply capacity of nutrients in soil–plant systems and their biogeochemical cycles. Understanding ecological stoichiometric characteristics of C, N and P in soils under various land uses is crucial to guide ecological restoration [...] Read more.

Chemometric analysis is often used as an effective indicator of the supply capacity of nutrients in soil–plant systems and their biogeochemical cycles. Understanding ecological stoichiometric characteristics of C, N and P in soils under various land uses is crucial to guide ecological restoration and agricultural cultivation in karst rocky desertification region. However, data on ecological stoichiometry at different land uses in karst areas is limited. This study aimed to evaluate the effects of different land uses on soil ecological stoichiometric ratios and further identify the factors that influence soil ecological stoichiometric ratios. The topsoil from forest, shrub and cultivated land (paddy field and dry land) both in a karst area and non-karst area (as a reference) of Mashan County was sampled to investigate the spatial variance of the ecological stoichiometric characteristics of C, N and P under different land uses. The results show that: (1) Land-use types significantly determined the spatial heterogeneity of soil ecological stoichiometry in karst areas. (2) Soil organic carbon (SOC) was not significantly different between shrubs in the karst area and forests in the non-karst area (p = 0.595), but there were virtual differences in total nitrogen (TN), total phosphorus (TP), C:N, C:P and N:P between shrubs in the karst area and forests in the non-karst area (p < 0.01). (3) The contents of SOC, TN, and C:P, N:P in the study area were all generally higher in forests than those in cultivated land, and the content of TP was lower in forests than cultivated land, while C:N in cultivated land was higher than in shrubs in karst areas, and C:N was higher in forests than in cultivated land in non-karst areas. (4) Available nitrogen (AvN) was the main factor influencing stoichiometry in shrubs in karst areas, while pH, AvN, available phosphorus and elevation were the main factors in forests in non-karst areas, indicating that these factors significantly affect the soil ecological stoichiometric ratio during land-use changes. This study helps to understand the variations in soil ecological stoichiometric ratios under land-use changes. It provides guidance for the sustainable management of revegetation in karst regions in southwest China. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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12 pages, 8920 KiB

Open AccessArticle

Interaction Mechanism of Fe, Mg and Mn in Karst Soil-Mango System

by Can Xu, Hui Yang, Chao Huang, Mingguo Lan, Zujian Zou, Fagui Zhang and Liankai Zhang

Land 2023, 12(1), 256; https://doi.org/10.3390/land12010256 - 14 Jan 2023

Cited by 2 | Viewed by 1687

Abstract

Manganese (Mn), an essential trace element for plants in which it is involved in redox reactions as a cofactor for many enzymes, represents an important factor in environmental contamination. Excess Mn can lead to toxicity conditions in natural and agricultural sites. Manganese toxicity [...] Read more.

Manganese (Mn), an essential trace element for plants in which it is involved in redox reactions as a cofactor for many enzymes, represents an important factor in environmental contamination. Excess Mn can lead to toxicity conditions in natural and agricultural sites. Manganese toxicity is one of the most severe growth limiting factors in acid soil, which accounts for 21% of the total arable lands in China. The more significant part of Mn-toxicity is its interactions with other mineral elements, in particular with phosphorus (P), calcium (Ca) and iron (Fe). The application of P or Ca can be beneficial in the detoxification of manganese, whereas Mn seems to interfere with Fe metabolism. Manganese toxicity varies with plant species, nutrients, and the soil environment. Mango is the main economic fruit in the karst area of the subtropical region of China. The karst soil in the mango orchard is characterized by high Fe, Mn and Mg. In order to explore the interaction among Fe, Mg, and Mn in karst soil and mango systems under high Mn conditions, a typical mango orchard in the karst depression landform in Baise in southern China was selected to study the effects of Fe and Mg on the toxic expression of Mn in mango plants and the interaction mechanism of Fe-Mn-Mg in mango plants. The results show that: (1) the mango growth status is closely correlated with Fe²⁺ (active iron) and Mg under the same soil Mn concentration; (2) The black spots on mango leaves were mainly caused by Fe and Mn. There is a lot of Fe³⁺ and Mn³⁺ in the black spots, which accounts for more than 90% of the total; (3) In addition, the studies also showed that the Fe and Mg inhibited the expression of Mn toxicity in mango. Conclusively, the interaction effect of Fe, Mn, and Mg is an important factor that affects mango growth, which can indicate the status of the soil and plants. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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18 pages, 18733 KiB

Open AccessArticle

The Effect of Bedrock Differences on Plant Water Use Strategies in Typical Karst Areas of Southwest China

by Jing Ning, Xiang Liu, Xia Wu, Hui Yang, Jie Ma and Jianhua Cao

Land 2023, 12(1), 12; https://doi.org/10.3390/land12010012 - 21 Dec 2022

Cited by 4 | Viewed by 1271

Abstract

Moisture conditions are important ecological factors limiting plant growth in karst areas. In karst areas, because bedrock exposure and permeability are significant and soils are dispersed—without spatial continuity—and shallow, the water storage required for plant uptake and growth in rock fissures as well [...] Read more.

Moisture conditions are important ecological factors limiting plant growth in karst areas. In karst areas, because bedrock exposure and permeability are significant and soils are dispersed—without spatial continuity—and shallow, the water storage required for plant uptake and growth in rock fissures as well as shallow soils is very limited, and therefore, water conditions are an important factor influencing plant growth. In order to discover the sources of water used by plants in the karst zone ecosystem of southwest China and the differences in plant water use under different lithological conditions, this study selected limestone and dolomite in the karst ecological test site of Maocun, Guilin, Guangxi, for comparison with the clastic rock area. By measuring the δD and δ¹⁸O composition of plant stem water and the potential water sources (soil water, groundwater and precipitation) of the dominant species in the study area, and using the IsoSource and soil water excess (SW-excess) models, we analyzed the proportion of water utilization by different vegetation types under different lithological conditions. The results showed that (1) the slope and intercept of the local rainfall line (LMWL) and soil water line (SWL) in the study area were smaller than those of the global rainfall line (GMWL), and also smaller than those of the local atmospheric precipitation line in Guilin (δD = 8.8δ¹⁸O + 17.96), indicating that the local rainfall is influenced by evaporation and is formed by nonequilibrium fractionation of isotopes; (2) in general, the plant water sources in the dolomite, limestone, and clastic areas were dominated by rainfall, groundwater, and soil water, respectively; and (3) the fluctuation range of SW-excess in karst areas was significantly greater than that in nonkarst areas, the xylem water of plants in karst areas was more depleted in δD than soil water, and groundwater was more enriched in δD than soil water, indicating that there might be an ecological–hydrological separation phenomenon in karst areas, i.e., the “two water worlds” hypothesis. The results of this study provide scientific data for hydrological regulation in the ecological restoration of karst areas. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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12 pages, 2109 KiB

Open AccessArticle

Preliminary Research on Agricultural Cultivation Decreasing Amino Sugar Accumulation in Calcareous Soils in Subtropical Karst Region of China

by Mengxia Zhou, Hui Yang, Tongbin Zhu, Cheng Zhang and Degen Zhu

Land 2022, 11(10), 1684; https://doi.org/10.3390/land11101684 - 29 Sep 2022

Viewed by 1563

Abstract

Soil microbial residues play an important role in the formation and stabilization of soil organic matter and can be quantitatively characterized by amino sugars. However, the response of soil microbial residues to agricultural cultivation in karst areas remains unclear. In this study, we [...] Read more.

Soil microbial residues play an important role in the formation and stabilization of soil organic matter and can be quantitatively characterized by amino sugars. However, the response of soil microbial residues to agricultural cultivation in karst areas remains unclear. In this study, we collected soil samples from natural reserved land as well as five plantation forests dominated by Citrus trees cultivated for 0, 1, 5, 15, 30 years to examine the effects of agricultural cultivation on the content of microbial residues (amino sugar analysis). Results showed that: (1) Soil Amino Sugars (ASs) contents were significantly reduced after agricultural cultivation along with the sharp decrease in soil organic carbon (SOC). After 30 years of cultivation, the contents of total ASs, glucosamine (GluN), galactosamine (GalN), and muramic acid (MurA) in cultivated soils decreased by 58.22%, 55.30%, 27.11%, respectively, compared with 0 yr.; (2) Microbial residual carbon contribution to SOC increased from 34.11% to 81.33% after 30 years of cultivation, including fungal residual carbon (FRC) (25.79% to 48.6%) and bacterial residual carbon (BRC) (8.32% to 32.72%); (3) Soil GluN/MurA values tended to decrease with increasing cultivation years. The results highlight the significant effect of cultivation years on amino sugar accumulation. It indicates that the years of reclamation in karst areas have different impacts on the organic fractions derived from various microbial communities in the soil organic matter pool, and the microbial residues indicated by amino sugar are of great significance for the interception of soil organic matter. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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13 pages, 2830 KiB

Open AccessArticle

Tillage-Induced Fragmentation of Large Soil Macroaggregates Increases Nitrogen Leaching in a Subtropical Karst Region

by Shuangshuang Xiao, Xiajiao Liu, Wei Zhang, Yingying Ye, Wurong Chen and Kelin Wang

Land 2022, 11(10), 1648; https://doi.org/10.3390/land11101648 - 24 Sep 2022

Viewed by 1331

Abstract

Tillage leads to rapid loss of soil nitrogen (N) over a short period of time in karst areas. N leaching is the primary pathway of soil N loss and therefore is key to understanding the mechanisms of N loss induced by tillage. However, [...] Read more.

Tillage leads to rapid loss of soil nitrogen (N) over a short period of time in karst areas. N leaching is the primary pathway of soil N loss and therefore is key to understanding the mechanisms of N loss induced by tillage. However, the factors affecting N leaching under tillage are not fully understood. Effects of tillage at various frequencies on leached N were examined in a one-year in situ simulation experiment using five tillage treatments: no tillage (T0), semiannual tillage (T1), and tillage every four months (T2), two months (T3), and monthly (T4). Concentration and amount of leached N had peaks in dry–rewetting months. Tillage significantly increased total amounts of leached N during the one-year experiment, and the largest amount of leached N was under tillage at the highest frequency. The primary form of N in leachate was NO₃¯ (88.49–91.11%), followed by DON (7.80–9.87%), and then NH₄⁺ with the lowest amount (1.09–2.10%). Tillage increased the amount of leached NO₃¯ and DON, but had no significant effect on leached NH₄⁺. Additionally, the amount of leached N had significantly negative correlations with 5–8 mm soil aggregate, NO₃¯, DON, and sand content, and positive correlations with 2–5 and 0.25–2 mm. Soil 5–8 mm aggregate and DON were the main factors explaining the variation in leached N according to the RDA analysis. Tillage increased the breakdown of large aggregates, appearing to have increased the mineralization of organic matter, which resulted in increased N leaching. Our results emphasize the importance of reducing or eliminating physical disturbance indued by tillage and maintenance of large soil aggregates for decreasing N leachate in lime soil of karst regions. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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16 pages, 2121 KiB

Open AccessArticle

Investigating the Binding Properties between Strontium and Dissolved Organic Matter under the Influence of pH and Ca²⁺ in a Typical Karst Area, China

by Xin Yao, Chuntian Su, Tuantuan Fan, Haoyu Ren and Fei Luo

Land 2022, 11(9), 1376; https://doi.org/10.3390/land11091376 - 23 Aug 2022

Cited by 1 | Viewed by 1088

Abstract

Due to the unique hydrogeological environment of karst areas, pollutants are more likely to enter the soil and water, showing a special migration and transformation behavior. In this work, the binding behaviors between strontium (Sr²⁺) and dissolved organic matter (DOM) extracted [...] Read more.

Due to the unique hydrogeological environment of karst areas, pollutants are more likely to enter the soil and water, showing a special migration and transformation behavior. In this work, the binding behaviors between strontium (Sr²⁺) and dissolved organic matter (DOM) extracted from soil under the influence of pH and Ca²⁺ in a typical karst area were investigated by applying three-dimensional fluorescence spectroscopy combined with parallel factor analysis (EEM–PARAFAC) and two-dimensional correlation analysis (2D-COS) of synchronous fluorescence spectra (SF). The results show that DOM extracted from soil was dominated by tryptophan-like and tyrosine-like materials (77% in total). Two-dimensional COS of SF showed that the tryptophan-like substance in DOM extracted from soil preferentially bound to Sr²⁺. When the pH was 7, the binding coefficient (logK_a) of the four DOM components ranged from 2.69 to 4.04, which was more conducive to the binding of DOM extracted from soil and Sr²⁺ than under acidic and alkaline conditions. Ca²⁺ in soil weakened the binding of DOM extracted from soil to Sr²⁺ by competing for binding sites and changing the molecular surface potential. This research is helpful for acknowledging the migration and transformation of Sr²⁺ and offers a reference for groundwater protection in karst areas. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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14 pages, 1092 KiB

Open AccessArticle

Distribution Characteristics and Risk Assessment of Heavy Metals in Soils of the Typical Karst and Non-Karst Areas

by Weijie Li, Tongbin Zhu, Hui Yang, Chunlai Zhang and Xia Zou

Land 2022, 11(8), 1346; https://doi.org/10.3390/land11081346 - 18 Aug 2022

Cited by 2 | Viewed by 1764

Abstract

To investigate the distribution characteristics and hazard levels of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in karst soil with a high geological background of heavy metals, 32 and 40 surface soil samples were collected from limestone and clastic [...] Read more.

To investigate the distribution characteristics and hazard levels of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in karst soil with a high geological background of heavy metals, 32 and 40 surface soil samples were collected from limestone and clastic rock areas, respectively, in the northern part of Mashan County, Guangxi Province, a typical mountainous county dominated by primary industries in China. Geostatistical methods, Pearson’s correlation analysis, the geo-accumulation index, and the potential ecological hazard index were applied to explore the influencing factors of those heavy metals and evaluate their potential contamination risks. The results show that (1) the levels of the eight heavy metal elements in the surface soils of karst areas exceeded the background values of soil for Mashan County, the background value of soil (layer A) in China, and abundance value of upper crust. According to the soil pollution risk screening values specified in the Soil Environmental Quality: Risk Control Standard for Contamination of Agricultural Land, the proportions of heavy metals in the soils of karst areas were ranked as Cd (100%) > As (90.6%) > Cr (84.4%) > Zn (68.8%) > Ni (37.5%). Meanwhile, the heavy metals in the soils of non-karst areas did not exceed the overall values for Mashan County, and Ni, Pb, and Zn did not exceed the overall national soil values. One-quarter of Cd in non-karst samples exceeded the risk-threshold screening value. There was a high degree of variation and a significant difference in the contents of heavy metal elements between karst and non-karst areas. (2) The element combinations of As-Cd-Cu-Hg-Ni-Pb-Zn and Cr in karst areas were characterized by the influence of carbonate rock parent material. The non-karst areas were characterized by Ni-Cu-Pb-Zn, As-Cr-Hg, and Cd assemblages, which were mainly influenced by the mixture of laterite parent materials, sand shale parent materials, and basic-rock residual materials, and that may be affected by element migration caused by soil erosion and anthropogenic activities. (3) Analysis of the geo-accumulation index showed that karst areas were generally found to be at the clean to light pollution level, except for in the areas whose samples exhibited medium/high pollution levels for Cd and Cr, with the Cd pollution being the more serious of the two. Small amounts of Cd and Cu were present in the non-karst areas at a light contamination level, while other elements were at the level of no pollution. (4) The results of the potential ecological risk index showed that Cd and Hg were the main ecologically hazardous heavy metal elements in the soils of the study areas. The potential ecological risk level in karst areas was much higher than in non-karst areas, especially for Cd, and was mainly influenced by the carbonate rock parent material. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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17 pages, 1553 KiB

Open AccessArticle

Nutritional Diagnosis of the Mineral Elements in Tainong Mango Leaves during Flowering in Karst Areas

by Chao Huang, Can Xu, Yiqi Ma, Tao Song, Zhi Xu, Si Li, Jianhong Liang and Liankai Zhang

Land 2022, 11(8), 1311; https://doi.org/10.3390/land11081311 - 14 Aug 2022

Cited by 1 | Viewed by 1456

Abstract

The balance of the mineral nutrition in mango leaves during the flowering period affects the flowering of mango trees and fruit production. Because the soil in karst areas has a slow and unbalanced supply rate of nutrients, mango orchards in a karst area [...] Read more.

The balance of the mineral nutrition in mango leaves during the flowering period affects the flowering of mango trees and fruit production. Because the soil in karst areas has a slow and unbalanced supply rate of nutrients, mango orchards in a karst area generally have a low yield. There are few studies on the fertilization of mango orchards in karst areas, especially on the diagnosis of leaf mineral nutrition. In this study, mango orchards in the typical karst areas of Guangxi province, one of the main mango-producing areas in China, were selected from the low-yielding and medium-yielding mango orchards. Surface soil samples and leaf samples from mango orchards in full bloom were collected to test for macronutrients and micronutrients. The Diagnosis and Recommendation Integrated System (DRIS) graphical method, the DRIS method, the Modified DRIS (M-DRIS), and the Deviation from Optimum Percentage (DOP) index diagnostic methods were applied to the leaves. The results showed that the DRIS graphical analysis yielded appropriate ratios of N, P, K, Mg, S, Fe, Mn, Cu with the corresponding three elements, Ca, Zn, and B, which can be used as reference diagnostic criteria. Based on the values of the DRIS diagnostic criteria for high-yielding orchards, the critical ranges of the suitable values of the mineral nutrients in the Tainong mango leaves during flowering were determined as N (14.87–17.27 g/kg), P (0.69–0.89 g/kg), K (4.45–6.90 g/kg), Ca (9.51–16.55 g/kg), Mg (1.44–2.20 g/kg), S (0.75–1.06 g/kg), Fe (0.10–0.13 g/kg), Mn (0.61–1.02 g/kg), Cu (5.41–8.89 mg/kg), Zn (7.91–18.95 mg/kg), and B (8.38–16.23 mg/kg). The results of the DRIS, M-DRIS, and DOP index methods were analyzed to determine the order of the fertilizer requirements for the low-yielding orchards: Mg > Fe > S > Zn > B > Cu > K > N > P > Mn > Ca, and for the medium-yielding orchards: Mg > Fe > B > Zn > S > Cu > N > Mn > K > P > Ca. The soil and leaf correlation analysis showed that the soil exchangeable Ca and effective Fe were significantly negatively correlated. Leaf Ca and Fe elements had a mutually antagonistic effect, leaf Mn-rich contents inhibited the uptake of the Mg and Fe elements, and low-yielding orchards had an excess of Mn and a deficiency of Mg. We found that there is lack of the Mg and Fe, a low content of the S and B, and an excess of the Ca and Mn in the mango orchards of the Baise karst area. We suggested that the DRIS graphical method is suitable for the diagnosis of three nutrient elements, and either the DRIS or M-DRIS index method can be chosen. The present research can be used for the precise fertilization of mango orchards in karst areas to improve the yield and quality of local mango orchards. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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12 pages, 1091 KiB

Open AccessArticle

Effects of Dodonaea viscosa Afforestation on Soil Nutrients and Aggregate Stability in Karst Graben Basin

by Lijun Liu, Guanglin Gou, Jinxia Liu, Xuebin Zhang, Qilin Zhu, Jinxia Mou, Ruoyan Yang, Yunxing Wan, Lei Meng, Shuirong Tang, Yanzheng Wu and Qiuxiang He

Land 2022, 11(8), 1140; https://doi.org/10.3390/land11081140 - 25 Jul 2022

Cited by 3 | Viewed by 1416

Abstract

Dodonaea viscosa is widely cultivated in the karst graben basin and is crucial for recovering land after rocky desertification. However, the effect of long–time D. viscosa afforestation on changes in the quality of soil remains unclear. Soil nutrients and aggregate composition can be [...] Read more.

Dodonaea viscosa is widely cultivated in the karst graben basin and is crucial for recovering land after rocky desertification. However, the effect of long–time D. viscosa afforestation on changes in the quality of soil remains unclear. Soil nutrients and aggregate composition can be used to evaluate the beneficial effects of afforestation of D. viscosa in improving soil functional stability. In this study, soil nutrients and aggregate stability were investigated using cropland, 10–year, 20–year, and 40–year D. viscosa afforestation and secondary succession shrub. Compared to the cropland, D. viscosa afforestation significantly increased the soil water content (WC), soil organic carbon (SOC), and total nitrogen (TN) contents, with an enhanced effect observed with prolonged afforestation. Soil nutrient contents under D. viscosa afforestation rapidly reached the level of the shrub. Dodonaea viscosa afforestation promoted the formation of >2 mm aggregates and decreased the ratio of 0.053–0.25 mm aggregates, which varied with afforestation years. Compared to the cropland, the content of >0.25 mm water–stable aggregates (R_>0.25), mean weight diameter (MWD), and geometric mean weight diameter (GMD) of soil increased exponentially. However, soil erodibility factor (K) and unstable aggregates index (E_It) decreased exponentially with prolonged D. viscosa afforestation, and the latter two indicators did not reach the level of the shrub. These results indicated that soil nutrients, aggregate stability, and erosion resistance increased with prolonged D. viscosa afforestation. However, the aggregate stability and erosion resistance exhibited by D. viscosa could not reach the level of secondary shrub for a long time. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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16 pages, 1774 KiB

Open AccessArticle

Characterization of Soil-Plant Leaf Nutrient Elements and Key Factors Affecting Mangoes in Karst Areas of Southwest China

by Tao Song, Chao Huang, Hui Yang, Jianhong Liang, Yiqi Ma, Can Xu, Mingbao Li, Xiang Liu and Liankai Zhang

Land 2022, 11(7), 970; https://doi.org/10.3390/land11070970 - 24 Jun 2022

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Abstract

Baise city is one of the largest producers of mangoes, with this agricultural industry located in the karst region of Southwest China. However, calcium-rich and alkaline soils, severe soil fragmentation, and poor water and fertilizer retention capacity contribute to low mango yields and [...] Read more.

Baise city is one of the largest producers of mangoes, with this agricultural industry located in the karst region of Southwest China. However, calcium-rich and alkaline soils, severe soil fragmentation, and poor water and fertilizer retention capacity contribute to low mango yields and are key issues that limit the development of the mango industry in karst areas. Our study objectives were to identify the soil factors that limit mango growth and yield in the karst region of Southwest China, and to determine how these growth- and production-limiting conditions vary between landscape positions. This study analyzed the differences in soil nutrient and element contents in mango leaves, and used a Random Forest algorithm to calculate the eigenvalues of the mango leaf and soil elemental indices in the different geomorphic parts (slopes, transition zone, passes, high-yielding depressions, and low-yielding depressions) of the karst peak-cluster depressions. The key factors affecting the mango leaves and soil were screened based on the diagnostic results and the eigenvalues. The results showed that for the elemental contents of Fe, Mg, Ca, and Mn in the mango leaves in the different geomorphic parts of the karst, the peak-cluster depressions were generally deficient and varied significantly. The contents of available B (AB), soil organic matter (SOM), pH, total nitrogen, available Fe, available Mn, alkaline hydrolysis nitrogen, exchangeable Ca (Caex), exchangeable Mg, and other indices in the soils differed significantly, and AB, available Zn, and available K (AK) showed low or very low content levels. In addition, the key soil factors limiting mango yield in the karst areas were AB, fulvic acid, SOM, Fe, Mn, Caex, soil water, and AK; and the key mango leaf factors were Ca, Mn, Fe, Zn, and Mg. Consequently, the characteristics of soil water content, pH, and soil organic matter may be the main drivers affecting the differences in the mango yield and the elemental characteristics. These findings suggest that the addition of organic fertilizer could improve the quality and yield of mangoes in karst areas. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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11 pages, 1516 KiB

Open AccessArticle

Divergent Response of the Supply Capacity and Turnover of Inorganic Nitrogen to Pitaya Cultivation in the Subtropical Karst Region of Southwest China

by Lin Yang, Xuebin Zhang, Jinxia Liu, Dongni Wen, Lei Meng and Tongbin Zhu

Land 2022, 11(6), 781; https://doi.org/10.3390/land11060781 - 25 May 2022

Viewed by 1277

Abstract

Determining the availability and supply capacity of soil inorganic nitrogen (N) can effectively guide the appropriate application of N fertilizers during crop cultivation. However, the mechanism underlying soil inorganic N production remains unknown for cash crops in karst regions. In this study, the [...] Read more.

Determining the availability and supply capacity of soil inorganic nitrogen (N) can effectively guide the appropriate application of N fertilizers during crop cultivation. However, the mechanism underlying soil inorganic N production remains unknown for cash crops in karst regions. In this study, the rates of organic N mineralization to ammonium (NH₄⁺) and NH₄⁺ nitrification to nitrate (NO₃⁻) were determined using a ¹⁵N tracing technique to evaluate the supply capacity of inorganic N in soils from woodland and pitaya plantations with different cultivation years (3, 9, and 15 years) in the subtropical karst region of China. The conversion of woodland to pitaya plantations significantly decreased the content of soil organic carbon (SOC), total N, calcium (Ca), and magnesium (Mg), along with the soil pH and cation-exchange capacity (CEC), but significantly increased the content of available potassium, available phosphorus, iron, and aluminum, in a more pronounced fashion with the increasing length of pitaya cultivation. The conversion of woodland to pitaya plantations has not significantly changed soil NH₄⁺ and NO₃⁻ content, but this land use has resulted in divergent effects on mineralization and nitrification rates. Compared to woodland (5.49 mg N kg⁻¹ d⁻¹), pitaya cultivation significantly reduced the mineralization rate to 0.62–2.38 mg N kg⁻¹ d⁻¹. Conversely, the nitrification rate significantly increased from 4.71 mg N kg⁻¹ d⁻¹ in soil under woodland to 9.32 mg N kg⁻¹ d⁻¹ in soil under 3-year pitaya cultivation, but this rate decreased to 1.74 mg N kg⁻¹ d⁻¹ under 15-year cultivation. Furthermore, the mean residence time of inorganic N was significantly higher in long-term than in short-term pitaya plantations, indicating the decline in inorganic N turnover with the increasing length of pitaya cultivation. Taken together, long-term pitaya cultivation could significantly decrease the supply capacity and turnover of inorganic N in soil. The Ca, Mg, SOC, and total N content, as well as CEC, were significantly and positively related to the mineralization rate, but negatively related to the mean residence time of NH₄⁺ and NO₃⁻, suggesting that the incorporation of organic matter can accelerate the soil inorganic N supply and turnover for long-term pitaya plantation in subtropical regions. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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17 pages, 1760 KiB

Open AccessReview

Carbonate Mineral Dissolution and Its Carbon Sink Effect in Chinese Loess

by Mingyu Shao, Muhammad Adnan, Liankai Zhang, Pengyu Liu, Jianhua Cao and Xiaoqun Qin

Land 2023, 12(1), 133; https://doi.org/10.3390/land12010133 - 31 Dec 2022

Cited by 1 | Viewed by 1616

Abstract

The relationship between the source and sink of atmospheric CO₂ has always been a widely discussed issue in global climate change research. Recent studies revealed that the chemical weathering of carbonate rocks contributed to 1/3 (~0.5 Pg C/yr) of the missing carbon [...] Read more.

The relationship between the source and sink of atmospheric CO₂ has always been a widely discussed issue in global climate change research. Recent studies revealed that the chemical weathering of carbonate rocks contributed to 1/3 (~0.5 Pg C/yr) of the missing carbon sinks (MCS) globally, and there are still 2/3 of MCS (~0.5 Pg C/yr) that need to be explored. As one of the main overburdened parts of the earth, loess is one of the important driving factors for atmospheric CO₂ consumption. Here, we elaborated on the dissolution process and the carbon sink effect from carbonate and silicate minerals in loess. The relationship between carbonate dissolution and carbon source/sink is elucidated, and the mechanism of carbon sink formation from secondary carbonates in loess is clarified. Additionally, the commonly used methods for the identification of primary and secondary carbonates are summarized, and the methods for the study of loess carbon sinks and the influencing factors of loess carbon sinks are also revealed. Based on the research results and progress interpretations, the prospects of loess carbon sinks are discussed to provide a scientific basis for further research on loess carbon sinks. Full article

(This article belongs to the Special Issue New Insights in Soil Quality and Management in Karst Ecosystem)

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