•Major earthquake trigger thousands of landslides and disturb vast area of vegetation.•How long will mountain environment become stable after major quake is unknown.•Vegetation dynamic indicates the ...stability of post-seismic mountain environment.•The Wenchuan earthquake's impact may disappear within two decades.
Major mountain earthquakes could have long-term impacts on post-seismic landslide activities. Yet, we have limited understanding of the duration of these impacts due to a lack of long-term consistent observation. This study combines multi-year high spatial resolution and high temporal resolution remote sensing images collected before and after the 12 May 2008 MW 7.9 Wenchuan earthquake to investigate post-seismic landslide changes and vegetation recovery processes at landslide sites in the epicentral area. We found that the earthquake caused significant vegetation damage by triggering co-seismic landslides. Since that time, vegetation at these landslide sites has been continuously recovering, and the total post-seismic landslide area is decreasing concurrently. Post-seismic vegetation recovery reflects and possibly promotes the decrease of post-seismic landslide activities. Our findings on post-seismic vegetation recovery at landslide sites indicate that the Wenchuan earthquake's impact on regional post-seismic landslide frequency may disappear within two decades after the major event.
•Aggregate mechanical stability was larger for moderately than highly developed soils.•Clay mineralogy and exchangeable cations dominated aggregate mechanical stability.•Crystalline Fe/Al oxides ...weakened mechanical strength in contrast to vermiculite.•Climate drove aggregate mechanical stability through inorganic cementing agents.
Soil aggregate mechanical properties are of vital importance for plant growth, tillage and soil erosion, and strongly conditioned by the amount and type of cementing agents that differ with soils. As most research focus at the site scale, how aggregate mechanical stability vary across different types of soils at regional scales and underlying mechanisms remain poorly understood. Herein, seven typical zonal soils in heavy textures with an increased status of soil development were collected under two land uses (arable and forest) and at three pedogenic horizons along the mid-temperate to south-subtropical climatic gradient in the East Asian monsoon region. Aggregate tensile strength (Y), specific rupture energy (Esp) and friability (FI) were measured on air-dried aggregates in a compression test, as well as soil cementing agents related to particle size distribution, organic matter and its components, metal oxides, phyllosilicates and exchangeable cations. Y and Esp were most affected by soil type (F = 37.7 and 21.4, p < 0.001), and less affected by land use and soil horizon (F < 8.2). Y and Esp were overall remarkably larger for temperate moderately (257 ∼ 700 kPa and 40 ∼ 261 J kg−1) than for subtropical highly developed soils (171 ∼ 329 kPa and 22 ∼ 52 J kg−1); FI (0.35 ∼ 1.30) showed no distinct geographic trend. Among soil properties, exchangeable polyvalent cations, crystalline Fe and Al oxides, and vermiculite had much larger and significant explanatory power (R2 = 0.33 ∼ 0.54, p < 0.01) than traditional soil properties (organic matter, soil texture and bulk density) (R2 < 0.25, p > 0.01), suggesting the predominant roles of the inorganic cementing agents in aggregate mechanical stability across soil types. Aggregate mechanical stability was increased by exchangeable polyvalent cations and vermiculite (r = 0.71 ∼ 0.81, p < 0.001), and weakened by crystalline Fe and Al oxides (r = −0.77 ∼ −0.74, p < 0.001). Additionally, mean annual precipitation and temperature were negatively correlated with aggregate mechanical stability (r = −0.80 ∼ −0.76, p < 0.001). This study demonstrates the remarkable geographic variations of aggregate mechanical stability under the influence of climate and highlights the importance of clay mineralogy (mainly swelling clay and crystalline Fe and Al oxides) and exchangeable cations at the regional scale.
An important form of land degradation is that induced by landslides. Vegetation recovery at coseismic landslide sites not only plays an important role in reducing soil erosion and increasing land ...stability but also records the transformation of loose, exposed landslide surfaces into stable hillslopes during the post‐seismic years. However, little is known about the vegetation recovery process or its influencing factors. In this study, we use the Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) dataset, Tropical Rainfall Measuring Mission (TRMM) 3B42 daily precipitation data, and a digital elevation model (DEM) to study the impacts of precipitation and topographic parameters on vegetation recovery after the 2008 Wenchuan earthquake. Our results reveal significant NDVI decreases during the 2008 earthquake and strong recovery in the following years at the coseismic landslide sites. We also found significant negative correlations between precipitation and derivative of the NDVI trend (NDVIDT) in 2010 and 2011 and significant positive correlations in 2009 and 2013 at the regional scale. These significant negative correlations indicate that precipitation may trigger landslides to remobilize, depressing the recovery of vegetation at coseismic landslide sites during the first few years following a major earthquake. The results further show that site‐specific vegetation recovery is determined by topographic parameters at the local scale. In general, vegetation recovery is weaker at low elevations (<1,300 m) and high elevations (>3,300 m), and it is also weaker on gentler slopes (<35°) than on steeper slopes (>35°).
•Urea has non-significant effect on aggregate breakdown whatever soil type.•Ammonium and nitrate inhibit aggregate breakdown for moderately developed soils.•Ammonium and nitrate promote aggregate ...breakdown for highly developed soils.•Various effects of nitrogen forms merit consideration in nitrogen fertilizer management.
Aggregate stability strongly affects many soil processes and is critical to maintain sustainable agriculture. Aggregate breakdown is controlled by the interaction between soil intrinsic properties and solution characteristics. Nitrogen fertilization including different forms is well known to influence aggregate stability; however, relative to their long-term effects, there is little recognition on the rapid response of aggregate breakdown to nitrogen solutions. This study aimed to examine the effects of nitrogen form and concentration on aggregate stability for different types of soils. Aggregate breakdown against slaking of three soil types (Phaeozem, Luvisol, and Acrisol) and three horizons (organo-mineral (A), illuvium (B), and parent material horizons (C)) was determined subjected to nitrogen solutions of three forms (CO(NH2)2, NH4+, NO3–) and five concentrations (0.05 ∼ 1.0 mol/L). Among nitrogen forms, urea solution almost had non-significant effect irrespective of soil type and horizon (p > 0.05); for NH4+ and NO3– solutions, aggregate stability showed little variations (MWD of 0.19 ∼ 0.26 mm) with electrolyte concentration for Phaeozem in B and C horizons, overall increased for Luvisol and Phaeozem in A horizon, and decreased first and then reached a steady state for Acrisol. The effects of nitrogen forms on aggregate breakdown were dependent on soil aggregation status or cementing agents (mainly organic matter, clay mineralogy). Electrolyte nitrogen solutions (NH4+ and NO3–) inhibited aggregate breakdown mainly through reducing electrostatic repulsive forces for moderately developed soils rich in swelling clays, and promoted aggregate breakdown by both weakening particle cohesion and enhancing compression pressure of entrapped air for highly developed soils rich in non-swelling clays and Fe/Al oxides. These results facilitate an improvement of fertilizer management and irrigation to improve soil quality on different soil types.
In recent years, heavy metal pollution has caused immeasurable harm to the environment. As an emerging technology, phytoremediation technology has gained a place in the treatment of heavy metal ...pollution with its unique advantages. This study analyzes the toxic effects of mulberry (Morus alba) seeds, seedling growth and silkworm under heavy metal stress of lead (Pb) and cadmium (Cd), and explore the accumulation and migration of Pb and Cd in the soil-mulberry tree-silkworm system. The main results were as follows: (1) Seed germination and potted seedling experiments were conducted under heavy metal Pb and Cd stresses, and it was found that Pb and Cd had inhibitory effects on mulberry seed germination, growth and photosynthesis of mulberry seedlings, and as the concentration of heavy metals increased, the stronger the inhibitory effect. Moreover, Pb and Cd have a synergistic effect under compound stress. (2) The accumulation and transfer rules of Pb and Cd ions in mulberry were different. The content of Pb in mulberry was root > leaf > stem and the content of Cd was root > stem > leaf. The combined stress promoted the transfer of Pb and Cd from the underground part to the aerial portion of mulberry. (3) The silkworm feeds on mulberry leaves contaminated with heavy metals in this experiment and found that: with the increase of silkworm feeding, the heavy metal content in the silkworm body increased significantly, but the content remained in the silkworm body was less, most of it was excreted with silkworm excrement. Combined stress has no significant effect on the detoxification mechanism of silkworm. It is indispensable to think of the synergistic effect of heavy metals on plants germination when seeds are used for phytoremediation.
•Combined stress of Pb and Cd on mulberry seed showed synergistic effects.•The accumulation and migration ability of the soil-mulberry-silkworm system under Pb and Cd stress were studied.•The cumulative efficiency is low along with the transmission of food chain, which has little impact on the silkworms.
•Virtual mixtures were used as samples for training the integrated unmixing model.•A semiempirical sediment source fingerprinting workflow was explored.•Adaptive boosting algorithm was used to ...emphasize the samples with poor accuracy.•The integrated unmixing model can achieve better performance than the basic model.•The proposed approach has the potential to maximize the use of all tracer information.
Tracing technology is increasingly being used in fluvial and aeolian sediment provenance assessments. Using synthetic sample mixtures in validations of unmixing model performance is becoming a standard step in sediment source fingerprinting. With tracer variability fully considered in the sources and target sediment, this study explored a semiempirical modelling strategy based on virtual sediment mixtures and the adaptive boosting (AdaBoost) algorithm. The obtained integrated unmixing model contained multiple composite fingerprints, and the weight coefficient was obtained from the iterative process. The performance of the integrated unmixing model was compared with that of unmixing models applying single or equal-weighted multiple composite fingerprints. All generated virtual sediment mixtures (280) were split into a training dataset (240) and a test dataset (40) to validate the generalization ability of the models. The results showed that the integrated unmixing model achieved better performance than the unmixing models with a single composite fingerprint (basic models). The integrated unmixing model yielded an average mean absolute error (A-MAE) of 5.51% for training data and 5.72% for test data, and it achieved better accuracy than the best basic model (6.23% on the training and 6.75% on the test dataset, composite fingerprint C-1) or equal-weighted model (6.32% on the training and 6.41% on the test dataset, average of 42 basic models). The robustness of the model accuracy was also improved with the AdaBoost algorithm. The modelling approach proposed in this study has the potential to maximize the use of all tracer information and further improve the reliability of sediment fingerprinting.
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•WUE as indicator used to enhance CS via safe-water use in karst area.•Ecologically critical zones were identified for karst CS with NbS.•DSI impact on WUE is nonlinear. WUE rose ...faster at DSI > 0.53 in negative area.•LAI-WUE correlation has pronounced thresholds for forests, shrubs.•Restricting access to mountains is effective way to enhance artificial CS.
After extensive ecological restoration in the karst region of Southwestern China, a potential zone for achieving “carbon neutrality” has emerged, despite facing water scarcity. We analyzed the dynamics of water use efficiency (WUE) and its correlations with soil moisture (SM) and leaf area index (LAI) from 2003 to 2017 using PML-V2 data and multiple datasets for SM and LAI. Advantageous areas for artificial carbon sequestration (CS) were also identified. Key findings are as follows: (1) Temporally, WUE exhibited fluctuating growth at an annual rate of 0.01 gCmm−1H2O (P < 0.05). The advantage areas for CS accounted for 15.96%, with over 31.74% of regions needing management intervention. (2) Monthly WUE was highest in the peak forest plain (PFP) landform (2.88 gCmm−1H2O), while PFP experiencing an annual decrease of −0.0021 gCmm−1H2O. (3) Monthly WUE was highest in forests (2.88 gCmm−1H2O), followed by shrubs (2.49 gCmm−1H2O), farmland (2.32 gCmm−1H2O) and grassland (1.93 gCmm−1H2O), while farmland showing the highest rate of increase (0.02). (4) WUE and SM exhibited both positive (14.26%∼26.02%) and negative (14.19%∼30.98%) correlations. In positive areas, WUE decreased as the drought stress index (DSI) increased for all vegetation types. Clear DSI threshold observed for farmland (0.29 to 0.42) and grassland (0.19 to 0.30). However, the peak values for forests and shrubs were less pronounced. There was a transitional point in the negative impact of DSI on WUE, which increased at a faster rate for all vegetation types when DSI exceeded 0.53. (5) WUE and LAI exhibited both positive (27.09%∼30.25%) and negative (23.37%∼34.57%) correlations. In positive areas, WUE increased as LAI increased for all vegetation types. However, forests exhibited threshold LAI values of 1.85 based on MODIS data, 2.71 based on GLASS data, and 2.59 based on GEOV2 data, shrubs had values of 1.69, 2.66, and 2.23, respectively. While grassland displayed LAI values of 0.79, 0.70, and 0.72, respectively. In negative areas, WUE decreased as LAI increased for all vegetation types. The minimum WUE values were observed when the LAI of farmland was 3.14 based on MODIS data, 4.05 based on GLASS data, and for grassland, it was 1.04, 1.97, and 1.76 based on the GEOV2 data, respectively. This study helps us to identify areas with potential for enhancing CS. It also assists in making informed decisions regarding the implementation of ecological restoration initiatives by considering SM as the limiting factor for adjustment measures and utilizing LAI as the reference standard.
Biomass and carbon (C) distribution are suggested as strategies of plant responses to resource stress. Understanding the distribution patterns of biomass and C is the key to vegetation restoration in ...fragile ecosystems, however, there is limited understanding of the intraspecific biomass and C distributions of shrubs resulting from plant interactions in karst areas. In this study, three vegetation restoration types, a Dodonaea viscosa monoculture (DM), a Eucalyptus maideni and D. viscosa mixed-species plantation (EDP) and a Pinus massoniana and D. viscosa mixed-species plantation (PDP), were selected to determine the effects of plant interactions on the variations in the C distributions of D. viscosa among the three vegetation restoration types following 7 years of restoration. The results showed that: (1) plant interactions decreased the leaf biomass fraction. The interaction of P. massoniana and D. viscosa decreased the branch biomass fraction and increased the stem and root biomass fraction, but not the interaction of E. maideni and D. viscosa. Plant interactions changed the C concentrations of stems and roots rather than those of leaves and branches. (2) Plant interactions affected the soil nutrients and forest characteristics significantly. Meanwhile, the biomass distribution was affected by soil total nitrogen, clumping index and gap fraction; the C concentrations were influenced by the leaf area index and soil total phosphorus. (3) The C storage proportions of all the components correlated significantly with the proportion of biomass. Our results suggested that both the biomass distribution and C concentration of D. viscosa were affected by plant interactions, however, the biomass fraction not the C concentration determines the C storage fraction characteristics for D. viscosa.
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•The influence of the complex terrain on the dynamic environment was elucidated.•Wind velocity at any target points can be deduced from a single observation point.•The wind erosion ...risk was predicted through numerical simulation process.•The sediment source contributions were estimated using fingerprinting technology.•Aeolian sediment transport processes can be clearly understood under the framework.
A systematic understanding of the transport processes of aeolian sand from source to sedimentary areas is important for both hazard control and fundamental mechanism research. This study proposes a methodological framework consisting of wind data standardisation, computational fluid dynamics (CFD) simulation and fingerprinting technology to clarify aeolian sediment transport processes. The methodological framework was applied to the Cuona Lake section of the Qinghai-Tibetan Railway as a case study. One main finding was that the mountain passes located on the west of the lake act as outlets that converge and accelerate the predominant wind. The Basuoqu river valley and Amdo-Cuona down-faulted valley act as a ventilation tunnel in the sedimentary area. The CFD simulation clearly showed the influence of the complex terrain on the wind flow field. Second, the area southwest of the lake was predicted to be the main sediment source; a large portion of this area has an annual wind power density exceeding 1000 W/m2. Third, the fingerprinting estimation results revealed that the predicted main source area contributed more than 80% to the target sediment, which was in good agreement with the CFD simulation result. A decision-tree is provided to guide interested users in critical choices for different situations and research objectives. This CFD- and fingerprinting- based framework has the potential to contribute significantly to aeolian research and facilitate the development of a more detailed methodology.
Plant health is closely related to the soil, where microorganisms play a critical and unique role. For instance,
Paeonia suffruticosa
is an emerging woody oil crop in China with attractive ...development and utilization prospects. However, black root rot causes wilting of the aboveground plant parts, which significantly affected its seed yield and quality. Studies found that soil microorganisms are critical in maintaining plant health, but how changes in the soil microbial communities affect the healthy and diseased oil peony is unclear. Therefore, our present study used high throughput sequencing and BIOLOG to analyze the rhizosphere soil microbial communities of healthy and diseased oil peonies. Our results revealed that the physical and chemical properties of the soil of the diseased plants had changed, with the ability to metabolize the carbon source being enhanced. Moreover, our research highlighted that the oil peony-infecting fungal pathogenic genus (
Fusarium
,
Cylindrocarpon
, and
Neocosmospora
) was closely associated with oil peony yield reduction and disease aggravation. Further network analysis demonstrated that the bacterial and fungal networks of the diseased plants were more complex than those of the healthy plants. Finally, the inter-kingdom network among the diseased plants further indicated that the lesions destroyed the network and increased the intraspecific correlation between the fungal groups.
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