查看更多>>摘要：? 2021 Elsevier B.V.Karst systems perform an important function in the global carbon cycle. Carbonate rocks contain the largest reservoir of C in the world and represent 12 to 18% of the total terrestrial surface free of water. This is relevant in the karst regions of western Cuba, where Red Ferralitic soils are distributed in the zones of the strongest agricultural production and population density, and the most important water supply basins. The objective was to examine the effect of carbon sequestration on terrain modeling in the stabilized karst regions that coincide with CO2 sinks, which is beneficial for the soil cover since it encourages the increase of soil organic carbon, and for the agroecosystem in general since it mitigates the effects of climate change. But it is harmful to karstic morphogenesis, because it was estimated that the average dissolution of CaCO3 is 0.15 mmol?L-1?yr?1, which represents a sequential evolution of the relief of ?0.04 m?yr?1. The progress of this process in the next 120 years would diminish the agricultural potential by over 44%. These results must be interpreted as the basis for the design of agro-environmental strategies and policies in the karst regions of Cuba, insufficiently studied from this perspective to date.
Alexandre Costa Crusciol C.Penn C.J.Gonzalez J.M.de Campos M....
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查看更多>>摘要：? 2021 Elsevier B.V.Combining deep soil tillage systems with lime application is a potential strategy for improving the sugarcane production in acidic soils. The authors evaluated the influence of tillage systems and lime application on sugarcane performance and soil attributes, including acidity. A field study in a clayey-textured Rhodic Hapludox soil was conducted with sugarcane for two growing seasons utilizing a 3 × 2 factorial scheme comprising three soil tillage systems with and without lime: conventional soil tillage system (CT), deep strip-tillage system (DT) and modified deep strip-tillage system (MDT). The soil tillage systems differed in the depth of soil disturbance and/or lime positioning. In addition to sugarcane stalk and sugar yields, pH, potential acidity (Pac), soil organic carbon (SOC), solid-phase and soil-solution calcium (Ca) and magnesium (Mg), the percentage distribution of exchangeable (%Alex) and non-exchangeable aluminum (%Alne) in the solid phase, and total monomeric (%TM-Al) in soil water extracts were analyzed and determined. The positioning of lime by the different tillage systems influenced the distribution of the Al fractions. TM-Al existed exclusively as organic monomeric Al (OM-Al) and showed little influence from treatments. In contrast, the distribution of Alex and Alne were highly influenced by lime and tillage system and varied according to the tillage efficiency of soil amendment. Soil chemical attributes and yield parameters were also influenced by the treatments in both growing seasons, highlighting the residual effect of liming. The soil chemical attributes influenced the Al fractions. Soil pH and exchangeable and soluble calcium (Caex and Cas) and magnesium (Mgex and Mgs) explained the variation of %Alne. Pac correlated with %Alex, whereas SOC explained the variation of %TM-Al. In general, the sucrose concentration, total recoverable sugar and stalk and sugar yields were increased by lime addition in plant cane and by lime addition and tillage systems in second ratoon. The stalk yield was highest in MDT, whereas the sugar yield was highest in both deep tillage systems.
查看更多>>摘要：? 2021 Elsevier B.V.Heterotrophic soil microbes are increasingly recognized as a key mediator transforming labile organic carbon (OC) into relatively stable soil carbon (C) in the form of microbial necromass (dead cells) and extracellular compounds associated with minerals. However, the accumulation of microbial necromass relative to labile OC consumption and its regulating factors remain poorly understood, although it has vital implications for soil C sequestration and modeling. Here by mimicking microbial C accumulation in constructed model soils using fructose as the sole OC substrate, we present a benchmark comparison of microbial C accrual versus OC mineralization under declining substrate availability and mineralogy. By quantifying various microbial components including biomass (living cells; indicated by phospholipid fatty acids), necromass (indicated by amino sugars) and total microbial C (including biomass, necromass and extracellular compounds; estimated as the difference between added and residual substrate C minus respiration) in a simple soil system, we compare microbial metabolic quotient (qCO2; i.e., microbial respiration rate per unit of biomass), amino sugar accumulation efficiency (AAE; i.e., ratio of amino sugars to respiration) and microbial C accumulation efficiency (mCAE; i.e., ratio of total microbial C to total microbial C and respiration), and assess their regulating factors. We find that while clay (bentonite) promotes microbial respiration, it enhances the rate as well as efficiency of amino sugar accumulation without affecting qCO2 or mCAE. On the contrary, ferrihydrite increases qCO2 and decreases AAE but promotes labile OC preservation via inhibiting microbial growth in the alkaline model soil. Hence, amino sugar accrual is more efficient in clay-rich model soils while labile OC is less consumed in model soils containing iron (hydr)oxide. Furthermore, while mCAE was correlated with qCO2 in all but the model soil with 6% clay, AAE was correlated with qCO2 only in model soils with 12% clay when the mineral treatments were considered separately. Collectively, our findings suggest that mCAE and AAE heavily depend on mechanisms preserving microbial C components but not solely on the metabolic efficiency and is mediated by soil mineral content as well as composition. Parameters considering microbial C preservation such as mCAE or AAE warrant further study for modelling and managing the formation of microbial derived stable soil OC.
查看更多>>摘要：? 2021 Elsevier B.V.Livestock integrated land use systems are considered as viable options for enhancing soil organic carbon (SOC) sequestration in a changing climate. This study assessed the influence of water deficit and livestock stocking density on soil carbon stocks. A total of 101 matching data were extracted from map layers of water deficit and livestock stocking density for C storage in Arenosols of Omusati and Otjozondjupa regions of Namibia. Maps for water deficit and livestock stocking density were obtained from national databases. The SOC data were arranged into four treatment combinations represented by two levels of water deficit and two levels of livestock stocking density. Linear mixed models (LMM) were then used to evaluate differences in SOC stocks in response to livestock stocking density and water deficit. Results showed that there was a significant interaction (p = 0.013) between the effects of livestock stocking density and water deficit on C-stocks. In conditions where the water deficit was small, the SOC stock was larger under more intensive grazing. Whilst in conditions where water deficit was large, the SOC stock was larger under less intensive grazing. Furthermore, the difference between SOC stock at large and small water deficits was larger under more intensive grazing. This shows that the impacts of a changing climate, and changes in the intensity of grazing must be considered together to predict effects on the SOC stock.
查看更多>>摘要：? 2021 The Author(s)Forest management, including selection of appropriate tree species to mitigate climate change and sustain biodiversity, requires a better understanding of factors that affect the composition of soil fauna communities. These communities are an integral part of the soil ecosystem and play an essential role in forest ecosystem functioning related to carbon and nitrogen cycling. Here, by performing a field study across six common gardens in Denmark, we evaluated the effects of tree species identity and mycorrhizal association (i.e., arbuscular mycorrhiza (AM) and ectomycorrhiza (ECM)) on soil fauna (meso- and macrofauna) taxonomic and functional community composition by using diversity, abundance, and biomass as proxies. We found that (1) tree species identity and mycorrhizal association both showed significant effects on soil fauna communities, but the separation between community characteristics in AM and ECM tree species was not entirely consistent; (2) total soil fauna abundance, biomass, as well as taxonomic and functional diversity were generally significantly higher under AM tree species, as well as lime, with higher litter quality (high N and base cation and low lignin:N ratio); (3) tree species significantly influenced the properties of litter, forest floor, and soil, among which litter and/or forest floor N, P, Ca, and Mg concentrations, soil pH, and soil moisture predominantly affected soil fauna abundance, biomass, and taxonomic and functional diversity. Our results from this multisite common garden experiment provide strong and consistent evidence of positive effects of tree species with higher litter quality on soil fauna communities in general, which helps to better understand the effects of tree species selection on soil biodiversity and its functions related to forest soil carbon sequestration.
查看更多>>摘要：? 2021 The Author(s)Changing climatic conditions (warming and decreasing precipitation) have been found to be a threat to the agricultural sustainability of Mediterranean croplands. From the climate change perspective, biochar amendment may interact with the effects of warming and drought stresses on soil ecosystems. However, the responses of soil microbial communities to the joint effects of climate change and biochar in Mediterranean croplands are not sufficiently known. To help fill this knowledge gap, in this work we used a field experiment to determine the effects of partial rain exclusion alone or combined with a soil temperature increase in biochar-amended (20 t ha?1) and unamended plots under crop rotation on soil chemical properties, enzyme activities, and the microbial community activity, structure, composition, abundance, and functions. The biomass, composition, and activity of the soil bacterial and fungal communities were more responsive to biochar addition than to climate manipulation. Thus, soil chemical parameters, enzyme activities and the relative abundances of bacterial populations were not responsive to the interaction of biochar and climate manipulation, while the predicted functionality of the bacterial community was modified by both factors. Soil β-glucosidase activity significantly decreased in response to biochar addition and climate manipulation, while urease activity was significantly increased by biochar, and protease activity was significantly decreased by climate manipulation. Gram negative and fungal biomasses were significantly affected by the interaction of biochar with climate manipulation. Climate manipulation produced changes in the composition of the soil fungal community without loss of diversity. This study illustrates how the interactions between biochar amendment and future climate change scenarios influence microbially-driven ecosystem services related to the maintenance of nutrient cycles and biodiversity in a Mediterranean agroecosystem.
查看更多>>摘要：? 2021 Elsevier B.V.Forest soils that have accumulated anthropogenic sulfur (S) as a result of historical air pollution may gradually or suddenly release inorganic sulfate either by desorption of inorganic sulfate or by mineralization of organic S, even after mitigation of previous air pollution. The release of inorganic sulfate from soil to surface water leads directly to watershed acidification. Thus, whether the organic S compounds that have accumulated in soils are resistant to microbial activity, due to formation of organo-mineral complexes, is essential information for management of forest soil ecosystem services. A nationwide air pollution monitoring survey by the Japanese Ministry of the Environment identified acidification of both surface water and soil in the Lake Ijira watershed of central Japan, presumably sourced from the Chukyo Industrial Area which lies upwind of the watershed. We compared the amount of S accumulated in the Ijira soils (Dystrudepts) with that in comparable soils in other watersheds in central Japan that were less affected by industrial air pollution. To determine how much mineral-associated organic S had accumulated in the Ijira soils, we measured pyrophosphate- extractable S. We used high-resolution x-ray fluorescence (HRXRF) spectroscopy with a double-crystal type high energy resolution spectrometer to estimate the oxidation states of both mineral-associated and free organic S. We also measured S isotope compositions to explore S dynamics in the soils. We found that more S had accumulated in the Ijira soils than in the comparable soils from other watersheds in central Japan. Concentrations of total S in the Ijira soils varied among soil horizons, reaching more than 1000 mg S kg?1 in some horizons. Mineral-associated organic S accounted for more than half of the total accumulated S. High-resolution x-ray fluorescence spectrum analyses showed that mineral-associated organic S was retained at both high and low oxidation states. The δ34S values of total S in the deeper horizons tended to be higher than those of the uppermost horizons of the Ijira soils and correlated positively with concentrations of extractable Al and Fe oxides (which characterize pedogenic minerals). Our results suggest that about half of total accumulated S in Ijira soils is stabilized in pedogenic minerals and the remainder comprises free organic S and adsorbed inorganic sulfates. There might have been repetitive mobilization and immobilization of S and the degraded organic S might have greater affinity with pedogenic minerals. Further, the ratio of total C to mineral-associated organic S correlated negatively with concentrations of extractable Al and Fe oxides, suggesting that organic S is more resistant to mineralization than organic C because S is preferentially associated with the pedogenic minerals. Monitoring of the chemical states of S compounds in soils historically exposed to air pollution is recommended to assist in prediction of the fate of the S compounds that have accumulated in them.
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