Nitrogen (N) deposition in China may increase due to urbanization and economic growth. Current research has considered the ecological significance under the assumption of increasing N deposition. Atmospheric N deposition tending toward levelling or declining has been observed in China. Such potential recovery and responses of high N loads ecosystems under decreasing atmospheric N deposition scenarios have yet to be adequately investigated. This work reviews existing literature to consider possible responses of carbon (C) sequestration, biodiversity and species composition, soil acidification, and greenhouse emissions in ecosystems responding to recent patterns of N deposition. Potential effects of N composition and internal ratios may be further explored through state-of-the-art N addition experiments and model development.

Greenhouse gases (GHGs) carbon dioxide (CO₂) and nitrous oxide (N₂O), contribute significantly to global warming, and they have increased substantially over the years. Reforestation is considered as an important forestry application for carbon sequestration and GHGs emission reduction, however, it remains unknown whether reforestation may instead produce too much CO₂ and N₂O contibuting to GHGs pollution. This study was performed to characterize and examine the CO₂ and N₂O emissions and their controlling factors in different species and types of pure and mixture forest used for reforestation. Five soil layers from pure forest Platycladus orientalis (PO), Robinia pseudoacacia (RP), and their mixed forest P-R in the Taihang mountains of central China were sampled and incubated aerobically for 11 days. The P-R soil showed lower CO₂ and N₂O production potentials than those of the PO soils (P < 0.01). The average reduction rate of cumulative CO₂ and N₂O was 31.63% and 14.07%, respectively. If the mixed planting pattern is implemented for reforestation, the annual CO₂ reduction amounts of China’s plantation can be achieved at 8.79 million tonnes. With the increase of soil depths, cumulative CO₂ production in PO and RP soils decreased, whereas CO₂ and N₂O production in P-R soil did not show similar pattern. Soil particle size fraction was the main factor influencing GHGs emissions, and the clay fraction showed negative correlation with cumulative CO₂ and N₂O production. In summary, compared with PO pure artificial forests, the mixture plantation mode can not only reduce GHGs pollution but also improve soil fertility, which is conducive to sustainable management of artificial forests.

Riparian areas are widely recognized as the main areas for carbon sequestration and nitrogen pollution removal, while little is known about the effects of the respective sand mining activities on riparian zones. In this study, the effects of sand mining activities on the soil organic carbon (SOC) storage, different N-removal processes (Feammox, anammox, and denitrification), and composition of the relative bacterial community at a depth of 0–40 cm were determined based on investigations in riparian sand mining areas and adjacent forestlands. The SOC density of the sand mining areas (2.59 t ha⁻¹, depth of 0–40 cm) was lower than that of the riparian forestlands (80.42 t ha⁻¹). Compared with those of the riparian forestland, the sand mining area exhibited a dramatic reduction in the CO₂-fixed gene abundances (cbbL) and a significant change in the composition of cbbL-containing bacteria. The rates of the Feammox (0.038 ± 0.014 mg N kg⁻¹ d⁻¹), anammox (0.017 ± 0.017 mg N kg⁻¹ d⁻¹), and denitrification (0.090 ± 0.1 mg N kg⁻¹ d⁻¹) processes at a depth of 0–20 cm in the soil layer of the sand mining area were reduced by 70.17%, 91.5%, and 93.62% compared with those of the riparian forestland, respectively. The riparian areas in the study area (approximately 12 ha, depth of 0–40 cm) destroyed by sand mining activities released approximately 933.96 t stored soil carbon, which reduce the annual carbon sequestration potential by 28.8–40.8 t. Moreover, the potential N-removal rates in the riparian forestlands (depth of 0–20 cm) by the Feammox, anammox, and denitrification processes were 1514.21–1530.95 kg N ha⁻¹ year⁻¹, whereas the potential N-removal rates in the sand mining area were only 121.2–126.19 kg N ha⁻¹ year⁻¹. Therefore, more investigations are necessary for comparing the benefits and damage of sand mining activities in riparian areas before more sand mining activities are approved.

The incorporation of crop straw with fertilization is beneficial for soil carbon sequestration and cropland fertility improvement. Yet, relatively little is known about how fertilization regulates the emissions of the greenhouse gas nitrous oxide (N₂O) in response to straw incorporation, particularly in soils subjected to long-term fertilization regimes. Herein, the arable soil subjected to a 31-year history of five inorganic or organic fertilizer regimes (unfertilized; chemical fertilizer application, NPK; 200% NPK application, 2 × NPK; manure application, M; NPK plus manure application, NPKM) was incubated with and without rice straw to evaluate how historical fertilization influences the impact of straw addition on N₂O emissions. The results showed that compared to the unfertilized treatment, historical fertilization strongly increased N₂O emissions by 0.48- to 34-fold, resulting from increased contents of hot water-extracted organic carbon (HWEOC), NO₃⁻, and available phosphorus (Olsen-P). Straw addition had little impact on N₂O emission from the unfertilized and NPK treatments, primarily due to Olsen-P limitation. In contrast, straw addition increased N₂O emissions by 102–316% from the 2 × NPK, M, and NPKM treatments as compared to the corresponding straw-unamended treatments. These results indicated that N₂O emissions in response to straw addition were largely regulated by historical fertilization. The N₂O emissions were closely associated with the depletion of NO₃⁻ and decoupled from change in NH₄⁺ content, suggesting that NO₃⁻ was the main substrate for N₂O production upon straw addition. The stoichiometric ratios of HWEOC to mineral N and mineral N to Olsen-P were key factors affecting N₂O emissions, underscoring the importance of resource stoichiometry in regulating N₂O emissions. In conclusion, historical fertilization largely regulated the impacts of crop straw incorporation on N₂O emissions via shifts in NO₃⁻ depletion and the stoichiometry of HWEOC, mineral N, and Olsen-P.

We investigated the growth and nutrient uptake of Myriophyllum spicatum under different nutrient conditions and evaluated its implications for ecosystem services in an enclosed area of Jinshan. The specific growth rate ranged from 1.29%–4.37%/day, and the dissolved inorganic carbon and nitrogen, and phosphorus uptake rates were 1.30–1.62, 0.040–0.453, and 0.003–0.027 mg/(g∙day), respectively, under different nutrient conditions. The O₂-production and carbon-sequestration efficiencies in the field were 154.30 and 1.25 mg/(g DW∙h), respectively. The average removal efficiencies of NH₄⁺-N, NO₃⁻-N, NO₂⁻-N, and PO₄³⁻-P were 43.05%, 97.03%, 64.26%, and 59.24%, respectively, in M. spicatum-cultivated areas compared with in the open sea. Harvesting of M. spicatum removed 12,936.87, 1289.97 and 114.81 kg of carbon, nitrogen, and phosphorus, respectively, from seawater in Jinshan in Nov, 2018. In conclusion, M. spicatum is a good candidate for integrated macrophyte/animal multi-trophic aquaculture in terms of nutrient extraction and economic diversification in low-salinity environments.

The exotic smooth cordgrass (Spartina alterniflora) has invaded intertidal wetlands near the Ronggenshan tidal flats of Beihai, Guangxi, China, where historically seagrasses and mangroves coexisted. We investigated sediment organic carbon (SOC) storage and macrobenthic community structure in the existing mangroves (MG), S. alterniflora (SA), seagrass bed (SG), and unvegetated flat (UnV) habitats following the S. alterniflora invasion. SOC storage increased after S. alternifolia invasion in the SG and UnV habitats. Spartina alterniflora invasion changed the dominant species of the macrobenthos in the original habitats and reduced the diversity of macrobenthos in SG and UnV habitats. Clearly, S. alternifolia invasion can change the ecological functioning of south China's coastal ecosystems by altering carbon sequestration and affecting biodiversity.

As an important ecological process, litter production is generally recognized as being directly relevant to net primary productivity and carbon storage of mangrove ecosystems. In the present study, we made continuous, monthly assessment of litter production from 2010 to 2016 for five mangrove sites in Shenzhen Futian Mangrove Nature Reserve. Results showed that all mangrove locations displayed distinct seasonality in litter production, and that the alien species produced significantly more litters than the native species. Carbon isotope analysis revealed an interesting, strongly negative relationship between litter production and δ¹³C of leaf litter (δ¹³CLL) among the five studied sites. Although it has long been known that δ¹³C of plant leaves correlates with water use efficiency and some components of plant productivity, the observed δ¹³CLL-litter production linkage is novel, justifying future exploration of δ¹³CLL as an potential indicator of litter production and net primary productivity in mangrove ecosystems.

Global climate change has attracted worldwide attention. The ocean is the largest active carbon pool on the planet and plays an important role in global climate change. However, marine plastic pollution is getting increasingly serious due to the large consumption and mismanagement of global plastics. The impact of marine plastics on ecosystem responsible for the gas exchange and circulation of marine CO₂ may cause more greenhouse gas emissions. Consequently, in this paper, threats of marine microplastics to ocean carbon sequestration are discussed. Marine microplastics can 1) affect phytoplankton photosynthesis and growth; 2) have toxic effects on zooplankton and affect their development and reproduction; 3) affect marine biological pump; and 4) affect ocean carbon stock. Phytoplankton and zooplankton are the most important producer and consumer of the ocean. As such, clearly, further research should be needed to explore the potential scale and scope of this impact, and its underlying mechanisms.

Green roof (GF) as an important role of urban ecosystem services is more and more focused on carbon sequestration for the mitigation of climate change, which there is still a gap of longer period of investigation on carbon sequestration on GF. This work aims to quantify the carbon sequestration on green roofs from 2012 to 2017 by measuring and calculating parameter on substrate organic carbon and plant organic carbon, when using waste building material substrate (WBMS) as GF substrate for the recycling of waste solid. Green roof group 2 (waste building material substrate (WBMS) as substrate) and green roof group 1 (local natural soil (LNS) as substrate), planting same three native plants (N. auriculata, L. spicata, and L. vicaryi), were both three substrate depth of 20 cm, 25 cm, and 30 cm, respectively. Results show that both innovative WBMS and LNS were a great capability of carbon sequestration and carbon storage on green roofs. Carbon storage of green roof group 1 and green roof group 2 was 65.6 kg C m⁻² and 72.6 kg C m⁻², respectively. Annual mean carbon sequestration of the WBMS was 1.8 times higher than LNS. The overall average carbon sequestration (12.8 kg C m⁻² year⁻¹) in green roof group 2 using WBMS was 1.1 times than corresponding in green roof group 1 (11.4 kg C m⁻² year⁻¹ using LNS). WBMS substrate and L. vicaryi could be considered as the most adaptable green roof configuration, which can be a recommendation to promote the carbon sequestration and the function of green roof for the better urban ecosystem services. Future work may focus on the GF carbon model, water interface, long-term monitoring, environmental impact, water quality and quantity, synthesized effect on GF ecosystem, low impact development (LID), management and simulation, and combination on intelligent urban system, based on LCA.

Heterotrophic system for carbon sequestration is gaining importance in the recent decades. Carbonic anhydrase (CA) is a major enzyme involved in carbon sequestration and biomineralization process. In this paper, we evaluate the effect of pesticide on CA activity using inhibitory assay. 2,4-D, being one of the most extensively used pesticide, being deleterious to soil health, its usage should be minimized to regain the soil health. Maximum inhibitory constant (Kᵢ) was observed for 5% 2,4-D (49.53 mM) followed by 5% glyphosate (43.92 mM). The maximum Km increase with increase in pesticide concentration by 3.05-fold was in case of glyphosate which was higher than that of 2,4-D (2.08-fold) and dichlorvos (2.38-fold). Moreover, we evaluated the carbon sequestration using CA enzyme in the soil microcosm. In the present study, we identified the negative impact of 2,4-D on carbonic anhydrase produced by Bacillus halodurans PO15. The inhibition was a mixed type and had significantly lowered the carbon reduction to about 2.38 ± 0.17% in a soil microcosm study. Based on the molecular docking, the inhibition was contributed due to weak H-bonding interaction with amino acid residues (Gly65, Gly95, Val147, Ser150 and Gly65, Ser146, and Ser150).