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Soil carbon sequestration is vital to reduce the atmospheric carbon concentration, which is expected to increase within future climatic scenarios. The present study aims to investigate the effects of land use changes to different plantation systems on SOC stocks, and simulate these changes using the RothC model in Mizoram, India. With this aim, four land uses, viz., secondary forest, oil palm, orange, and arecanut plantations, established on degraded shifting cultivation lands, and a control natural forest were selected for this study. The soils were sampled 0–30 cm in the secondary forest, plantations, and the natural forest, at an interval of five years. Measured SOC stocks were the highest in the secondary forest (67.0 Mg C ha−1) and the lowest under the oil palm plantation (37.4 Mg C ha−1), 10 years after land use conversion. The climate change projections for 2021–2035 and 2036–2050 indicated that temperature and rainfall changes, projected to increase by 0.8 and 2.0 °C, and 5.9 and 5.4%, respectively, will affect SOC stocks in the future differently, depending on the land use and carbon input from vegetation. Baseline climate simulations under land use change showed the highest increase in the SOC stock under the secondary forest (116%), and the lowest in the oil palm plantation (27%). Overall, the model predicted that SOC stocks would increase, but the rate of change (0.23–1.86 Mg C ha−1 yr−1) varied with different land uses, plant species, and land management practices. The model results indicated that restoring secondary forest following the abandonment of a shifting cultivation and orange plantations are the best options to improve SOC stocks within future climate change scenarios. Conversely, arecanut and oil palm need to be reduced because the SOC storage is lower. [ABSTRACT FROM AUTHOR]

• Stability of SOC fractions differed among the forest types. • SOC stock was highest in a temperate forest (132.7 Mg C ha−1). • Active and passive carbon pool was highest in temperate and Quercus forests, respectively. • Conversion of natural forests to bamboo and jhum land reduced SOC stock. • Quercus forest plays a significant role in long-term carbon sequestration. Forests are among the largest terrestrial carbon pools that are most vulnerable to land use and land cover change (LULC). Therefore, it is essential to manage forest ecosystems to enhance soil organic carbon (SOC) pools and soil functionality. The present study was carried out to analyze C stability and change in SOC stock under different forest types in the eastern Himalayan region of India. Topsoil (0–15 and 15–30 cm) samples from six dominant forests i. e. tropical wet evergreen, montane subtropical, temperate, Quercus , bamboo, and shifting cultivation (Jhum) lands were collected and analyzed for selected soil properties and SOC stock. Active (very labile + labile), slow (less labile), and passive (non-labile) C fractions were also analyzed to determine the stability of the SOC pool under the LULC scenario. Results show that the percentage contribution of active C to total organic carbon in topsoil was highest in a temperate forest (74.1%) while lowest in a bamboo forest (48.1%). Unlike, slow C (18.4%) and passive C (26.6%) were highest in Quercus forest. Pearson correlation analysis shows significant positive relation of active and slow C pool with SOC and total nitrogen concentration. The estimates of SOC stock (0–30 cm) were significantly higher in temperate forests (132.7 Mg C ha−1). However, the conversion of natural forests to bamboo forest and jhum land reduced SOC stock by 29% and 68%, respectively. C lability index shows higher labile C in jhum land while recalcitrancy index was highest in a bamboo forest. Our study concluded that LULC change significantly altered the stability and stock of SOC in natural forests. Owing to a higher percentage of slow and passive C pools, Quercus forests play a major role in C sink management. [ABSTRACT FROM AUTHOR]

Surface coal mining activities have numerous consequences on terrestrial ecosystems. Loss of soil and biomass carbon pool due to mining activities is a serious concern in the rapidly changing environment. We investigated the effect of fast-growing trees (Albizia lebbeck, Albizia procera, and Dalbergia sissoo) on soil fertility and ecosystem carbon pool after eight years of afforestation in the post-mining land of Jharia coalfield, India, and compared with the adjacent natural forest site. Significant differences in soil organic carbon (SOC) and total nitrogen (TN) stocks in afforested mine soil and natural forest soils were observed. Greater SOC stock was found under D. sissoo (30.17 Mg·C·ha−1) while total N stock was highest under A. lebbeck (4.16 Mg·N·ha−1) plantation. Plant biomass accumulated 85% of the natural forest carbon pool after eight years of afforestation. The study concluded that planting fast-growing trees in post-mining lands could produce a promising effect on mine soil fertility and greater carbon storage in a short period. [ABSTRACT FROM AUTHOR]

Understanding what controls the soil organic matter (SOM) storage and its stability is important to predict how SOM will respond to environmental changes. The role of mycorrhizal fungi in mediating soil carbon (C) and nitrogen (N) cycling is increasingly recognized. However, how mycorrhizal fungi could affect C distribution and N demand of different soil fractions is largely unknown. Here, we compiled a global dataset of C and N concentrations in different SOM fractions from arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) dominated ecosystems, covering major biomes, including tropical forest, temperate forest, boreal forest, and grassland. Based on this dataset, we evaluated the effect of mycorrhiza symbiosis on C storage and C: N stoichiometry of SOM fractions with different stability. We found that for both topsoil and subsoil, bulk soil C storage and C: N ratio in EcM ecosystems were higher than those in AM ecosystems, and a similar pattern was also observed in the particulate organic matter fraction (POM). However, the C storage in the mineral-associated organic matter fraction (MAOM) was not different between AM and EcM ecosystems. Moreover, with the increase in bulk soil C concentration, the C storage in topsoil MAOM reached a stable level in EcM ecosystems but continued to increase in AM ecosystems. With the increase in soil N concentration, bulk soil C storage of EcM ecosystems increased more rapidly than that of AM ecosystems, which was mainly driven by the increase in POM C storage. Our study highlights that soil C storage and relative stability are different between AM and EcM ecosystems. Although EcM ecosystems have a higher soil C storage and lower N demand per unit soil C, most C is distributed in relative labile POM. Therefore, SOM in EcM ecosystems could be more susceptible to disturbances caused by land use and climate changes. • EcM ecosystems have higher soil C storage and C:N than AM ecosystems. • EcM ecosystems have higher particulate organic C content than AM ecosystems. • The mineral-associated organic C content is not different between AM and EcM ecosystems. • The mineral-associated organic C content can reach saturation in EcM ecosystems. • SOM in EcM ecosystems could be more vulnerable to land use and climate changes. [ABSTRACT FROM AUTHOR]

Plant carbon (C) inputs via shoot, roots, and the associated mycorrhizal fungi are vital drivers of soil organic C (SOC) stock and turnover. Both the amounts and proportions of plant C inputs to the soil through these pathways can be affected by soil fertility. Yet, we know little about how divergent pathways of plant C inputs contribute to SOC cycling under different soil fertility. By growing the C4 grass Cleistogenes squarrosa in C3 soils, we quantified the contributions of shoot, roots, and arbuscular mycorrhizal fungi (AMF) to SOC turnover with different fertility in a temperate grassland. Our four-year field experiment showed that soils with higher fertility sequestered more shoot-, root- and AMF-derived C, which were mainly driven by greater soil microbial biomass. Irrespective of soil fertility, roots contributed the most (44%) to new SOC formation, while shoot (28%) and AMF (28%) exerted similar but lower contributions. We found that the positive priming effects induced by roots and AMF were greater in more fertile soils, which were primarily associated with more root- and AMF-derived C, respectively. Across all the soil fertility levels, root pathway had an equal impact on new SOC accumulation and native SOC losses via priming effects, and thus caused no net SOC changes. However, the priming effect induced by AMF pathway was 60% higher than the root pathway across treatments. The disproportionately large priming effects relative to new SOC accumulation induced by AMF led to net SOC losses, especially in soils with higher fertility. Overall, we demonstrated that plant C inputs through shoot, root, and mycorrhizal pathways have differential impacts on SOC turnover. Our quantitative estimation should be valuable for more accurately modeling how much plant-derived C can be sequestered in the soils and advancing our understanding of future SOC dynamics under global changes. [Display omitted] • We quantified contributions of C inputs via shoot, roots, and AMF to SOC turnover. • Soils with higher fertility sequestered more shoot-, root- and AMF-derived C. • Root-derived C contributed more to new SOC formation than shoot- and AMF-derived C. • Priming effects induced by root-derived C were smaller than that by AMF-derived C. • Root-derived C caused no net SOC changes but AMF-derived C induced net SOC losses. [ABSTRACT FROM AUTHOR]