查看更多>>摘要：? 2022 Elsevier B.V.Forests cover a considerable proportion of the land area and function importantly to regulate the global climate system as carbon (C) sinks. Rapid urbanization process may be changing the C sink function of forests worldwide, but its potential effects on the accumulation of soil organic C (SOC) remain inconclusive. In this study, we collected litter and soil samples in the surface layer of six urban and suburban forests to fractionate SOC by combining physical, chemical and biological methods and quantify the contents of these SOC fractions. The results showed that urban forests contained significantly lower contents of labile and non-labile SOC fractions, therefore contributing to significantly lower total SOC content in urban than in suburban forests. Interestingly, we observed that the SOC content was significantly correlated with the litter C stock in urban forests but not in suburban forests, while it was significantly correlated with the soil microbial biomass in suburban forests but not in urban forests. These scenarios suggest that urbanization could have substantially regulated the SOC accumulation mode in the surface soil of subtropical forests, e.g., from microbial filtering pathways to abiotic ones, therefore influencing the stabilization of SOC in these subtropical forests.
查看更多>>摘要：? 2022 The Author(s)Evaporitic lakes such as playa-lakes are characteristic of many arid regions and are unique environments with respect to fauna and flora, while being very vulnerable to climate and environmental fluctuations and threatened by the current global change scenario. Water balance oscillations in these systems can trigger the precipitation or dissolution of different evaporitic minerals, negatively impacting local biodiversity and economic activities. Here, we study the sedimentary record of a small saline pond from a playa-lake complex in southwestern Iberia in order to reconstruct the paleohydrological evolution of this area and assess potential anthropogenic disturbances. The different proxies studied in the ～11.9 ky old sedimentary record of the Laguna de la Ballestera suggest that the greatest lake extension and the highest water levels occurred during the Early Holocene, pointing to the wettest period of the record. Climate transitioned towards more arid conditions during the Middle Holocene, and even more dramatically during the Late Holocene. In this last stage the wetland surface and the water level largely diminished and gypsum precipitation gradually increased pointing towards a negative precipitation/evapotranspiration balance and lowest water levels. Summer desiccation likely occurred under this scenario, especially after ～1.0–0.9 cal ky BP coeval with the Medieval Climate Anomaly, when gypsum content started to rise abruptly. However, this significant gypsum precipitation was only associated with a massive drop in the siliciclastic content and scarce carbonates (dolomite and calcite) during the last ～400 years. This evidence suggests a shift from a (semi) permanent to a temporal/seasonal hydrological regime. The environmental evolution of this wetland responded to the general climatic evolution of the western Mediterranean during the Holocene, being mostly controlled by changes in insolation. Our data also show that the environmental response of the studied wetland to natural climate variations was only significantly disturbed by human activities since the 20th century, especially in the second half of the century, deduced by abrupt fluctuations in the siliciclastic, gypsum and organic content in the sediments, as well as by the enhanced sedimentary accumulation rates, probably as a response to changes in the hydroperiod of the lake and in the catchment land use.
查看更多>>摘要：? 2022 Elsevier B.V.The sheet and rill erosion phases dominate the erosion process of the catchment area and up-slope of Benggang (a special gully) area, and its evolution has a vital impact on erosion characteristics in the erosion feedback loop. Here, the rill development processes, morphological characteristics and corresponding soil loss were investigated by laser scanning on the four coarse-textured granite topsoils defined as WH, TC, GX, and CT for the counties of Wuhua, Tongcheng, Ganxian, and Changting in China, respectively. A soil flume (3 × 0.8 m) at a slope gradient of 16.7% was treated with rainfall-inflow at the upslope inflow rate of 2 L min?1 and rainfall intensity of 90 mm h?1. Results showed that soil erosion rate increased with erosion evolution (sheet erosion, rill advance, and rill maturity phases). A comparison of the four different soils exhibited that the soil erosion rate showed a downtrend with the increase of soil clay and gravel contents. Specifically, the CT soil with high clay and gravel content showed the minimal soil erosion rate (0.024 kg m?2 min?1), rill density (0.95 m m?2), headward erosion rate (0.41 cm min?1), and surface evolution rate. The maximal soil erosion rate and rill depth were observed on the WH slope, with the rill headward erosion rate reaching the maximum of 20.59 cm min?1. Despite no significant difference in the geomorphologic comentropy of the four soils, their variation trend and rate could reflect dynamic changes in erosion. The total sediment transport efficiency was improved by rill formation and development, with rill erosion contributing to about 70% of total soil loss for the four soils. This study can enrich our understanding of the rill erosion process and surface morphology of coarse-textured topsoils.
查看更多>>摘要：? 2022 Elsevier B.V.Water erosion exerts a profound, but uncertain effect on the terrestrial carbon cycle. Therefore, the soil erosion intensity is uncertain in different terrains. Previous studies have focused on the slope and intensity of soil erosion, while ignored the special terrain such as gully created by erosion. To advance the understanding of the mineralization dynamics of soil organic carbon (SOC) from the micro perspective, the relationship between soil erosion and carbon source and sink is expected to be further improved. In this study, we explored the impact of water erosion on SOC mineralization in the areas of gully erosion in Qingyuan mountain, Jiangxi, China by combining the 137Cs technique and laboratory incubation experiment, calculated the first-order kinetic model parameters of the SOC mineralization of bulk soil and aggregates in the area of gully erosion, and estimated the correlation between the factors that may affect SOC mineralization. The results showed that (1) the mineralization rates of SOC in the bulk soil and aggregates showed fluctuations and reached a peak, and finally became stable. The soil erosion intensity was significantly positively correlated (p < 0.05) with the cumulative mineralization of SOC. (2) The cumulative mineralization in the depositional area (489.67 mg kg?1) was higher than that in the erosional area (402.69 mg kg?1). (3) Soil macroaggregates were the main contributors to SOC mineralization (63.56%–92.28%), and the soil macroaggregate organic carbon mineralization dynamics was more sensitive to soil erosion. Additionally, significant effects (p < 0.05) of soil mechanical composition, capillary pores, saturated water content, and contents of carbon and nitrogen on SOC mineralization were observed. Erosion increased the risk of SOC loss by mineralization of SOC, especially in macroaggregates. The deposition process caused the enrichment and burial of SOC, and the background level of SOC and the content of macroaggregates in the depositional area were higher than those in the erosional area. The results showed that soil erosion increased the risk of SOC loss by mineralization of SOC based on laboratory simulation. The present study aiming at examining the effect of gully erosion on the mineralization and sequestration of SOC provides important insights into balancing the global carbon budget.
查看更多>>摘要：? 2022 Elsevier B.V.Land subsidence is a phenomenon commonly associated with water withdrawal and mining. In river valleys it increases the risk of flooding, which is usually reduced by channel alignment and raising of flood dykes. In this work, we describe the natural, advanced processes of sedimentation and channel adjustment to ground level changes in the Chech?o River reach within an about 30-year-old subsidence basin in southern Poland. Physicochemical properties of sediments, channel geometry and its changes over a 5-year period have been analyzed. These sediments of the ponded depression differ markedly from the laminated overbank deposits of the unaffected river reach in respect of their stratigraphy and accretion rate. Formation of a levee is the characteristic feature of the ponded reach. The levee deposits are silt-dominated and highly organic and overlay thick sandy strata. The ponded parts of the basin outside the levee zone are characterized by slow deposition of fine grained organic sediments. A local increase in a channel slope induces relatively intensive erosion at the knickpoint and the formation of sediment wave on the channel at the downstream end of the pond. These changes are associated with a rapid increase of the Width/Depth ratio. The sediment wave has a tendency to disperse in place due to channel downcutting and the formation of the over 100 m-long downstream reach with the geometry similar to that observed in unaffected river reaches. These investigations indicate that even small subsidence ponds can exist in a highly dynamic fluvial environment for decades before they disappear. They can enrich the local habitat and landscape for long enough to be important for biodiversity in regions heavily impacted by human activity. Decisions regarding the restoration of subsided lands should be site-specific and preceded by considerations for achieving the best possible benefits instead of mandatory liquidation of subsidence depressions.
查看更多>>摘要：? 2022 Elsevier B.V.Bio-mulching is a common agricultural practice in southwest China to improve crop productivity and soil fertility. In this study, a field experiment to investigate the effects of Chinese milk vetch (Astragalus sinicus L.) mulching and soybean straw retention (at the rate of 2250 and 4500 kg ha?1) on wheat soil microbial community and carbon utilization efficiency was conducted in southwest China. Results showed that the alpha diversity indices (Chao and Shannon) of bacteria and fungi in milk vetch mulching treatment were significantly increased in the wheat non-rhizosphere soils compared with control soil (without mulching). Within the bacterial community, the relative abundance of Actinobacteria and Chloroflexi was significantly increased by milk vetch mulching over the control, while the relative abundance of Acidobacteria, Firmicutes, Verrucomicrobia, and Gemmatimonadetes were significantly decreased in both wheat rhizosphere and non-rhizosphere soil. Within the fungal community, the relative abundance of Basidiomycota was significantly increased in milk vetch mulching treatment than that of control. By contrast, the differences in microbial diversity and community structure between the soybean straw retention and control were not distinctive. The correlation analysis revealed that wheat soil moisture, soil nitrate content, microbial biomass carbon, dissolved organic carbon and nitrogen content were closely related to the soil microbial community structure under different mulching practices. Results of the Biology ECO-plate revealed that all bio-mulching practices have enhanced the carbon source utilization rate. In addition, the relative abundance of Actinobacteria and Basidiomycota has a positive correlation with the metabolism rate of carbon substrates, such as glycyl-L-glutamic acid, I-erythritol, D-xylose, and α-cyclodextrin. Overall, our results suggested that bio-mulching, especially milk vetch mulching, has changed greatly the soil microbial community structure and function in the wheat rhizosphere.
查看更多>>摘要：? 2022 Elsevier B.V.Microorganisms are critical for litter decomposition, organic carbon (C) and nutrient transformations in soil, corresponding to the vegetation succession. The dynamics of microbial activities and ecological functions during the soil recovery after agricultural land use (post-agricultural restoration) remains unclear. We investigated the effects of vegetation and soil restoration duration on active microbial biomass, microbial growth rates, C use efficiency (CUE, analyzed by 14C glucose utilization), and enzyme activities in three soil types of Russia: Haplic Luvisol in a deciduous forest (chronosequence from 0 to 37 years), Luvic Phaeozem in forest steppe (0–66 years), and Haplic Phaeozem in forest steppe (0–42 years). The microbial CUE (0.66–0.82) decreased during restoration and was highly dependent on soil type: the lowest in Luvisol and the highest in Haplic Phaeozem. The activities of β-1,4-glucosidase, β-1,4-N-acetylglucosaminidase, leucine aminopeptidase, and acid phosphatase increased during post-agricultural restoration. Microbial growth rates and the proportion of active microorganisms increased with restoration, reflecting a shift of microbial community to fast-growing decomposers (mainly r strategists) caused by large litterfall from recovered natural vegetation. The increase of the portion of active microorganisms and microbial growth rates was correlated with activities of enzymes responsible for C, N and P cycling. In conclusion, the post-agricultural restoration activates microorganisms, raises microbial growth, increases enzyme activities and accelerates microbially-mediated C and nutrient turnover.
查看更多>>摘要：? 2022 The AuthorsIn the current paper, a hybrid model was developed to generate 3D delineated soil horizons using clay sensitivity (St) with 1 m depth intervals in a landslide prone area in the southwest of Sweden. A hybridizing process was carried out using generalized feed forward neural network (GFFN) incorporated with genetic algorithm (GA). The model was conducted by means of seven variables consisting of the geographical coordinates and piezocone penetration test data (CPTu). The output of model (St) as a description of the effect of soil disturbance on shear strength plays a significant role in landslides in Sweden and thus can be applied for site-specific evaluation. Therefore, the use of St-based models to delineate soil layers can be a cost-effective solution to improve geo-engineering design practices and assist in the reduction of related environmental risks, such as catastrophic landslide events or excavation failures. Evaluated model performance based on different applied soil classifications showed 4.38% improvement in the predictability level of GFFN-GA compared to optimum GFFN. Accordingly, delineated soil layers were evaluated using different criteria including previous landslides as well as supplementary geophysical and geotechnical investigations. The results show that the adopted hybrid GFFN-GA is an efficient tool that can potentially be applied to delineate soil horizons for the prediction of future events.
查看更多>>摘要：? 2022The detrimental impacts of surface runoff and soil erosion, particularly in cultivated areas, call for the use of distributed runoff and soil erosion models with a view to supporting adapted catchment management strategies. However, runoff model parameterization remains challenging in agricultural catchments due to the high spatial and seasonal variability of soil properties. Data acquisition is demanding and may not always be feasible. Therefore, model parameterization in such environments have been the subject of numerous research efforts. The combined analysis of land use management and soil surface state was proposed in literature to address this issue and demonstrated its potential for runoff analysis and modelling. However, these research findings were related to specific rainfall sequences and/or soil surface state. In this study, existing knowledge on soil surface state and its application to runoff model parameterization were synthetized and included in an easy-to-use parameterization software (PREMACHE), providing a framework for modelers lacking of means and/or data for modelling complex agricultural catchments. To develop and evaluate the software, a dataset was acquired over 9 years on more than 110 plots in a 1045 ha agricultural catchment, including crop types, soil surface state, rainfall and runoff time series. Soil surface state dynamics was modeled based on crop types and daily rainfall. It was evaluated in the experimental catchment and validated in a nearby catchment. Soil hydrodynamic properties (e.g. infiltration capacity) were deduced from this framework and literature data at a daily time step, for each plots. Moreover, runoff events were measured when the modeled infiltration capacity was low, indicating that the parametrization adequately captured its temporal dynamics. The software developed in this study, as well as setup values deduced from the monitoring campaigns are provided with the manuscript for application in other ungauged catchments and explore their impact on agricultural catchment hydrological dynamics.
查看更多>>摘要：? 2022 Elsevier B.V.Cultivated land plays a vital role in human survival and the development of human civilization. The cultivated land quality (CLQ) is of considerable significance for ensuring food security and social stability. Although studies have been conducted to assess CLQ, efforts regarding the quantitative impacts of CLQ on crop production capacity are still scarce, especially in arid regions. Understanding such a question greatly benefits land resources management and sustainable development of oasis agriculture. The objective of this study is to explore the spatiotemporal variations of CLQ and to quantify the impacts of CLQ on crop production capacity via an ordinary linear regression (OLS) model and correction analysis in arid regions. The Delphi-AHP (analytic hierarchy process) method is applied to assess CLQ in this study with the highest accuracy (96.35%). The average score of cultivated land quality (S-CLQ) is 58.75 in the study area. The results further suggest that the quality of decreasing cultivated land (61.53) is much higher than that of increasing cultivated land (57.99). We use net primary productivity (NPP) calculated by the vegetation photosynthesis model (VPM) to simulate the crop production capacity and find that CLQ has a significant positive impact on crop production capacity (R2 = 0.706). The distribution of average annual NPP is similar to that of CLQ. 62.41% of cultivated land shows an increasing trend in annual NPP, whereas 37.57% of cultivated land shows a decreasing trend. Pearson coefficient by intervals is calculated to identify areas where crop production capacity does not match the quality of cultivated land. The results reveal considerable differences in the Pearson coefficient in various intervals (negative correlation in 5 intervals and positive correlation in 10 intervals). This research quantifies the impacts of CLQ on crop production capacity and provides a way to accurately capture the location of cultivated land that needs to be improved in arid regions.
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