The effects of afforestation tree species mixing on soil organic carbon stock, nutrients accumulation, and understory vegetation diversity on reclaimed coastal lands in Eastern China

Characteristics and factors influencing soil organic carbon composition by vegetation type in spoil heaps

Introduction

The variation of organic carbon content in spoil heaps is closely related to improving soil structure, maintaining soil fertility, and regulating soil carbon cycling balance. Analyzing the soil organic carbon content and related driving factors during the natural vegetation restoration process of spoil heaps is of great significance for promoting the accumulation of soil organic carbon in the spoil heaps.

Methods

we selected spoil heaps with the same number of years of restoration to research the variations in soil organic carbon components under different vegetation types (grassland: GL, shrubland: SL, secondary forest: SF) and compared the results with those on bare land (BL).

Results

Our results showed that vegetation type and soil depth significantly affect the content of soil organic carbon components. There was no difference in soil organic carbon components between SF and SL, but both were considerably superior to GL and BL (p<0.05), and the particulate organic carbon (POC) and light fraction organic carbon (LFOC) contents of SL were the highest. A significant positive linear correlation existed between SOC and active organic carbon components. Pearson's correlation and redundancy analysis showed that the available potassium (AK) and total nitrogen (TN) contents and gravel content (GC) in the BL soil significantly impacted soil organic carbon. When vegetation is present, TN, total phosphorus (TP), and Fine root biomass (FRB) significantly affect soil organic carbon. Structural equation modelling (SEM) shows that AK and soil moisture content (SMC) directly affect the organic carbon composition content of BL, When there is vegetation cover, fine root biomass (FRB) had the largest total effect in the SEM. Soil bulk density (BD) has a negative impact on soil organic carbon, especially in the presence of vegetation.

Conclusion

These findings suggest that vegetation restoration can significantly increase soil organic carbon content, FRB, AK, and TN play important roles in enhancing soil organic carbon. Supplementation with nitrogen and potassium should be considered in the bare land stage, and shrubs nitrogen-fixing functions and well-developed roots are more beneficial for the accumulation of soil organic carbon.

Different Responses of Soil Bacterial and Fungal Communities in Three Typical Vegetations following Nitrogen Deposition in an Arid Desert

The effects of increased nitrogen (N) deposition on desert ecosystems have been extensively studied from a plant community perspective. However, the response of soil microbial communities, which play a crucial role in nutrient cycling, to N inputs and plant community types remains poorly understood. In this study, we conducted a two-year N-addition experiment with five gradients (0, 10, 30, 60, and 120 kg N ha-1 year-1) to evaluate the effect of increased N deposition on soil bacterial and fungal communities in three plant community types, namely, Alhagi sparsifolia Shap., Karelinia caspia (Pall.) Less. monocultures and their mixed community in a desert steppe located on the southern edge of the Taklimakan Desert, Northwest China. Our results indicate that N deposition and plant community types exerted an independent and significant influence on the soil microbial community. Bacterial α-diversity and community dissimilarity showed a unimodal pattern with peaks at 30 and 60 kg N ha-1 year-1, respectively. By contrast, fungal α-diversity and community dissimilarity did not vary significantly with increased N inputs. Furthermore, plant community type significantly altered microbial community dissimilarity. The Mantel test and redundancy analysis indicated that soil pH and total and inorganic N (NH4+ and NO3-) levels were the most critical factors regulating soil microbial communities. Similar to the patterns observed in taxonomic composition, fungi exhibit stronger resistance to N addition compared to bacteria in terms of their functionality. Overall, our findings suggest that the response of soil microbial communities to N deposition is domain-specific and independent of desert plant community diversity, and the bacterial community has a critical threshold under N enrichment in arid deserts.

Structural equation model was used to evaluate the effects of soil chemical environment, fertility and enzyme activity on eucalyptus biomass

This paper aims to reveal the effects of multi-generational succession of eucalyptus on soil fertility, organic structure and biological properties. Soil samples were collected from eucalyptus plantations of different stand ages (5, 11, 17 and 21 years old) in a typical area in south Asia, soil organic fraction structure and content characteristics were investigated using Fourier transform infrared (FTIR), and structural equation modelling (SEM) was used to explore influences of soil fertility, enzyme activity and organic fraction on stand biomass. FTIR analysis showed that 11 infrared absorption peaks existed in the soils of this study area, attributed to silicates, aromatics, carbonate ions, sugars, esters, polysaccharides, aliphatic hydrocarbons and phenolic alcohols. Combined with the results of peak area integration, the content of esters, aromatics and phenolic alcohols was significantly higher in 17- and 21-year-old stand soils than in control soils. The results of SEM showed that organic components were negatively related (p < 0.01) to enzyme activity and biomass, with standardized coefficients of 0.53 and 0.49, respectively. In summary, multi-generation succession of eucalyptus trees can change the structure of soil organic functional group composition and promote the enrichment of aromatic and phenolic alcohol functional groups. Such changes can directly inhibit the increase in eucalyptus biomass and indirectly negatively affect biomass by inhibiting enzyme activity.

Identifying Emissions Reduction Opportunities in International Bilateral Emissions Trading Systems to Achieve China's Energy Sector NDCs

Exploring more emissions reduction opportunities for China's energy sector and lowering China's decarbonisation costs are essential to fulfilling China's nationally determined contributions (NDCs) and making China's sustainable development more feasible. This study explored emissions reduction opportunities for China's energy sector in international bilateral emissions trading systems (ETSs) using a CGE (computable general equilibrium) model. This study revealed that linking China's ETS to those of regions with lower decarbonisation responsibilities, which tend to be developing regions, could lower China's carbon prices, thus increasing China's domestic energy supply and lowering energy prices (and vice versa). Meanwhile, the volume of emissions from regions linked to China also significantly affected the degree of the change in China's carbon prices. Among these, ETS links to India and Russia could reduce China's carbon price from 7.80 USD/ton under domestic ETS to 2.16 USD/ton and 6.79 USD/ton, allowing the energy sector and energy-intensive sectors to increase greenhouse gas emissions by 1.14% and 7.05%, respectively, without falling short of meeting its NDC targets. In contrast, as a consequence of links with the United States and the European Union, China's carbon price could increase to 5.37 USD/ton and 1.79 USD/ton, respectively, which would limit China's energy and energy-intensive sectors to emitting 5.45% and 2.24% fewer greenhouse gases in order to meet its NDC targets.

The effects of green waste compost on soil N, P, K, and organic matter fractions in forestry soils: elemental analysis evaluation

We study the effects of green waste compost on soil fertility to provide a theoretical basis for accurately improving forestry soil quality. This study aims to investigate the effects of green waste compost on soil N, P, K, and soil organic matter (SOM) fractions using elemental and FTIR analyses. Therefore, five fertilization treatments were set up for research, including mineral fertilization (M-fert), green waste compost fertilization (G-fert), standard rate of M-fert plus G-fert (GM-fert), half the standard rate of M-fert plus G-fert (1/2 GM-fert), and a control with no fertilizer addition (N-fert). The results showed that GM-fert treatment significantly increased the content of soil NH₄–N, available phosphorus (AP), available potassium (AK), water soluble organic carbon (WSOC), humus (HE), and humic acid (HA), which were 8.53 ± 0.67, 76.1 ± 5.96, 168 ± 3.42, 0.152 ± 0.01, 5.64 ± 0.15, and 4.69 ± 0.21 mg kg⁻¹, respectively. The content of HA (36.7%, F = 7.55, P = 0.01) was positively correlated with the soil N, P, K, and the HA absorption peak. The relative intensities of the alcohol –OH, aliphatic –CH and carbohydrate C–O peaks showed the largest changes, which were 18.6 ± 0.56%, 13.1 ± 0.33%, and 16.3 ± 0.49%. –CH/C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C (49.8%, F = 12.9, P < 0.01) was also significantly positively correlated with soil N, P, K. In conclusion, green waste compost significantly increased soil N, P, K, and HA in forestry soils, and the –CH/CC of HA was the main factor related to soil nutrients.

Green waste compost significantly increased soil N, P, K, and HE fractions, and the –CH/CC components of the HA structures made the biggest contribution to soil N, P, K in forestry soil.