Search

[Objective] In the context of the “dual-carbon” goal, accurately assessing the status, rate and potential of carbon sequestration in terrestrial ecosystems is crucial for achieving “carbon neutrality”. Shaanxi Province, which spans three climatic zones and have a large difference in climate between north and south, with abundant vegetation types. In recent years, the vegetation coverage in Shaanxi has been further improved due to the implementation of various ecological projects (Grain for Green, Three-North Shelterbelt, etc.). Its vegetation coverage reaches up to 60.7%, what resulted in huge carbon sequestration capacity. Net primary productivity (NPP), as one of the most important indicators to reflect the carbon sequestration capacity of vegetation, there are few studies on spatial and temporal dynamic changes of NPP and the spatial distribution of NPP potential in the future in Shaanxi province. [Methods] Based on these, we evaluated the temporal and spatial distribution characteristics of vegetation NPP and its potential in Shaanxi province through the CASA model and the neighborhood similarity spatial distribution method. [Results] (1) Total carbon sequestration by vegetation increased by 333 Tg, with an increase of 48.5% from 2000 to 2020 in Shaanxi province. (2) NPP was higher in the south and lower in the north, with the highest or lowest value in the middle. The average value in 2000 and 2020 were 333.2 g C/m2 and 494.8 g C/m2, respectively, with a total increasement of 161.6 g C/m2, and the increase amplitude showed a distribution trend of high in the north and low in the south in Shaanxi. (3) The carbon sequestration potential was 2 304 Tg which increased by 41.30% compared with the 2020. The spatial distribution trend was gradually decreasing from south to north, and the spatial distribution characteristics showed high spatial autocorrelation characteristics, but the local differences were large. [Conclusion] The total vegetation carbon sequestration in Shaanxi province increased significantly from 2000 to 2020, and there is huge potential for vegetation carbon sequestration in the future. This study calculated the spatial and temporal dynamic changes and predicted potential spatial distribution characteristics of NPP in the regional scale ecosystem in Shaanxi province, which can provide an evaluation systematic and theoretical reference for scientific evaluation and improvement of regional carbon sink capacity.

Microbial carbon (C) use efficiency (CUE) describes the proportion of organic C used by microorganisms for anabolic processes, which increases with soil organic C (SOC) content on a global scale. However, it is unclear whether a similar relationship exists during natural vegetation restoration in terrestrial ecosystems. Here, we investigated the patterns of CUE along a 160‐year vegetation restoration chronosequence (from farmland to climax forest) estimated by stoichiometric modeling; additionally, we examined the relationship between CUE and SOC content and combined these results with a meta‐analysis. The combination indicated that vegetation restoration decreased CUE from 0.35 to 0.28. Surprisingly, SOC content increased with decreasing CUE during vegetation restoration because forest soils have low pH values and high microbial phosphorus limitations compared to early ecosystems, implying that climax forests may not sequester as much soil C as expected. The shift in soil pH was the most important predictor of CUE compared to climate, plant, and microbial factors. CUE changes were directly induced by soil pH and not by the pH‐induced microbial community. Alkaline soil acidification tended to decrease CUE. This first large‐scale estimate of the relationship between CUE and SOC during natural restoration highlights the need to strengthen C sink management in mature forests to sustain their C sequestration potential. [ABSTRACT FROM AUTHOR]

Soil iron (Fe)‐associated carbon (C) (Fe‐OC) plays a vital role in the soil C cycle due to its high stability, but vegetation restoration might alter the composition and quantity of Fe‐OC by introducing a large amount of plant‐derived C and affecting soil properties. However, how vegetation restoration affects soil Fe‐OC remains unclear. Herein, plant and topsoil samples from grasslands, shrublands, and forestlands across three soil types (loam, loess, and sandy soil) since cropland conversions were collected to address this issue. The results showed soil Fe‐OC content decreased in loam soil but increased in loess and sandy soil following vegetation restoration. Additionally, the Fe‐OC accumulation efficiency induced by vegetation restoration increased with the coarser soil texture. Vegetation restoration promoted the accumulation of Fe‐OC by increasing soil microbial biomass C, dissolved organic C, aromatic‐C, and citric acid, but also disrupted the combination of Fe oxides and C by introducing oxalic acid, reducing Fe oxide content and iron trivalent (Fe(III)). There were two‐sided effects of vegetation restoration on Fe‐OC, but the overall effect depends on the soil types. Moreover, isotopic evidence indicated that microbial source C is the main source of Fe‐OC, but Fe oxides preferentially adsorbed dissolved organic matter (DOM) and root deposits from plants rather than microbial residues and metabolites following vegetation restoration. In addition, Fe oxides preferentially adsorbed aromatic‐C compared to other functional group components. These findings indicated that vegetation restoration in coarser‐texture soils, coupled with selecting species that increase soil microbial biomass, produce more root deposits, and enhance DOM, contribute to the accumulation of soil Fe‐OC. Plain Language Summary: Iron (Fe)‐associated carbon (C) (Fe‐OC), formed by the combination of organic C and Fe oxides, plays a significant role in soil C cycling. However, the changes in soil Fe‐OC and their underlying mechanisms following vegetation restoration remain unclear. This gap hinders our understanding of soil C cycling and our ability to protect this important C pool. Here, croplands, grasslands, shrublands, and forestlands across three soil types (loam, loess, and sandy soil) were selected to address this issue. All three vegetation types had undergone 20 years of restoration from croplands. We found that soil Fe‐OC content decreased in loam soil but increased in loess and sandy soils after vegetation restoration. Furthermore, the effects of vegetation restoration on Fe‐OC accumulation and depletion were observed across all three soil types, but the overall effect varied depending on the soil type. Additionally, microbial‐derived C was identified as the primary source of Fe‐OC during vegetation restoration, while Fe oxides preferentially adsorbed plant‐derived dissolved organic matter and root deposits. These results deepen our understanding of soil C cycling and emphasize the potential for enhancing this stable C pool through human intervention. Key Points: Vegetation restoration has a two‐sided effect on Fe‐OC, and the overall effect depends on soil typeMicrobial‐derived C is the main source of Fe‐OC during vegetation restorationFe oxide preferentially adsorbs dissolved organic matter and root exudates from plants compared to microbial‐derived C [ABSTRACT FROM AUTHOR]

Vegetation restoration has an important effect on soil carbon (C) pool dynamics. Highly stable iron (Fe)‐associated C is an important component of the soil C pool and it plays a crucial role in the soil C cycle. However, a knowledge gap remains regarding the existence of Fe‐associated C variation during vegetation restoration.Herein, 0–60 cm soil samples of cropland, grassland, shrubland and forestland from three soil types (loam, loess and sandy soils) were collected to explore the response of Fe‐associated C to vegetation restoration.The results showed that soil Fe‐associated C proportion in the study area ranged from 2.2% to 26.3%. Surface soil (0–20 cm) Fe‐associated C content in loess and sandy soils increased following vegetation restoration, but decreased in loam soil. The accumulation efficiency of soil Fe‐associated C during vegetation restoration was higher in coarser soils. Moreover, the Fe‐associated C content and proportion of forestland with a higher soil organic matter (SOM) pool were the highest among the land use types.Vegetation restoration affects soil Fe‐associated C in two different ways: (1) increasing the SOM and dissolved organic C and improving the efficiency of C and Fe binding to promote the accumulation of Fe‐associated C; (2) decreasing the total soil Fe content, reducing the trivalent iron (Fe(III)) to bivalent iron (Fe(II)) and breaking the binding of C and Fe to decrease soil Fe‐associated C content, and these two different ways were found in all three soil types. Additionally, higher SOM accumulation efficiency and less root destruction caused by vegetation restoration in coarse soils resulted in a higher Fe‐associated C accumulation efficiency.Synthesis and applications. Vegetation and soil type strongly regulated the effects of vegetation restoration on soil Fe‐associated C. Forestlands may be the optimum vegetation type to provide soil C sequestration benefits, effectively increasing soil C pool and maximising Fe‐associated C content. This study has addressed the knowledge gap regarding the effects of vegetation restoration on soil Fe‐associated C and provides scientific basis for a better understanding of the soil C cycle and developing scientific vegetation restoration measures. [ABSTRACT FROM AUTHOR]

A disassembly line is an effective disassembly system to recover end-of-life products. In real life, as end-of-life products are subject to varying degrees of wear and tear, task failure may occur in the disassembly process. In this paper, the task failure risks are considered, and an expected profit-based stochastic disassembly line balancing problem is studied. First, a mathematical model is presented to maximise the expected recovering profit with task failures. Then, a hybrid metaheuristic approach is developed to efficiently solve the proposed model, which is integrated with a variable neighbourhood descent method and an artificial bee colony algorithm. Finally, the effectiveness and robustness of the proposed algorithm are verified by three cases, and experiment results show that the solution performance of the proposed approach is superior to the other three existing methods. [ABSTRACT FROM AUTHOR]

We investigate the statistical properties of kinetic ϵu and thermal ϵ θ energy dissipation rates in two-dimensional (2D) thermal vibrational convection (TVC). Direct numerical simulations were conducted in a unit aspect ratio box across a dimensionless angular frequency range of 10 3 ≤ ω ≤ 10 7 for amplitudes 0.001 ≤ a ≤ 0.1 , with a fixed Prandtl number of 4.38. Our findings indicate ϵu is primarily associated with the characteristics of the vibration force, while ϵ θ is more related to the large-scale columnar structures. Both energy dissipation rates exhibit a power-law relationship with the oscillational Reynolds number R e os . ϵu exhibits a scaling relation as ⟨ ϵ u ⟩ V , t ∼ a − 1 R e os 0.93 ± 0.01 , while ϵ θ exhibits two distinct scaling behaviors, i.e., ⟨ ϵ θ ⟩ V , t ∼ a − 1 R e os 1.97 ± 0.04 for R e os < R e os , cr and ⟨ ϵ θ ⟩ V , t ∼ a − 1 R e os 1.31 ± 0.02 for R e os > R e os , cr , where the fitted critical oscillational Reynolds number is approximately R e os , cr ≈ 80. The different scaling of ⟨ ϵ θ ⟩ V , t is determined by the competition between the thermal boundary layer and the oscillating boundary layer. Moreover, the probability density functions (PDFs) of both dissipation rates deviate significantly from the lognormal distribution and exhibit a bimodal shape. By partitioning the contributions from the boundary layer and bulk regions, it is shown that the bulk contributes to the small and moderate dissipation rates, whereas the high dissipation rates are predominantly contributed by the boundary layer. As R e os increases, the heavy tail of the PDFs becomes more pronounced, revealing an enhanced level of small-scale intermittency. This small-scale intermittency is mainly caused by the influence of BL due to vibration. Our study provides insight into the small-scale characteristics of 2D TVC, highlighting the non-trivial scaling laws and intermittent behavior of energy dissipation rates with respect to vibration intensity. [ABSTRACT FROM AUTHOR]