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In the Mediterranean region, despite bamboo being an alien species that can seriously alter plant and animal biocoenosis, the area occupied by bamboo plantations continues to increase, especially for the purpose to sequester carbon (C). However, the C dynamics in the soil–plant system when bamboo is grown outside its native area are poorly understood. Here we investigated the C mitigation potential of the fast-growing Moso bamboo (Phyllostachys edulis) introduced in Italy for climate-change mitigation. We analyzed aboveground (AGB) and belowground (as root/shoot ratio) biomass, litter and soil organic C (SOC) at 0–15- and 15–30-cm depths in a 4-year-old bamboo plantation in comparison with the former annual cropland on which the bamboo was established. To have an idea of the maximum C stored at an ecosystem level, a natural forest adjacent the two sites was also considered. In the plantation, C accumulation as AGB was stimulated, with 14.8 ± 3.1 Mg C ha–1 stored in 3 years; because thinning was done to remove culms from the first year, the mean sequestration rate was 4.9 Mg C ha–1 a–1. The sequestration rates were high but comparable to other fast-growing tree species in Italy (e.g., Pinus nigra). SOC was significantly higher in the bamboo plantation than in the cropland only at the 0–15 cm depth, but SOC stock did not differ. Possibly 4 years were not enough time for a clear increase in SOC, or the high nutrient uptake by bamboos might have depleted the soil nutrients, thus inhibiting the soil organic matter formation by bacteria. In comparison, the natural forest had significantly higher C levels in all the pools. For C dynamics at an ecosystem level, the bamboo plantation on the former annual cropland led to substantial C removal from the atmosphere (about 12 Mg C ha–1 a–1). However, despite the promising C sequestration rates by bamboo, its introduction should be carefully considered due to potential ecological problems caused by this species in overexploited environments such as the Mediterranean area. [ABSTRACT FROM AUTHOR]

There is considerable interest devoted to old-growth forests and their capacity to store carbon (C) in biomass and soil. Inventories of C stocks in old-growth forests are carried out worldwide, although there is a lack of information on their actual potential for C sequestration. To further understand this, soil organic carbon (SOC) was measured in one of Italy’s best-preserved old-growth forests, the Sasso Fratino Integral Nature Reserve. This reserve is on the World Heritage List along with other ancient beech forests of Europe, and it is virtually untouched due to the steepness of the terrain, even before legal constraints were imposed. Although the sandstone-derived soils are often shallow, they are rich in organic matter. However, no quantification had been carried out. By systematically sampling the topsoil across the forest, we accurately determined the average amount of SOC (62.0 ± 16.9 Mg ha–1) and nitrogen (4.0 ± 1.2 Mg ha–1) in the top 20 cm. Using the CENTURY model, future dynamics of SOC stocks were predicted to 2050 according to two climate scenarios, A1F1 and B2, the first of high concern and the second more optimistic. The model projected an increase of 0.2 and 0.3 Mg ha–1 a–1 by 2030 under the A1F1 and B2 scenarios, respectively, suggesting that the topsoil in old-growth forests does not reach equilibrium but continues accumulating SOC. However, from 2030 to 2050, a decline in SOC accumulation is predicted, indicating SOC net loss at high altitudes under the worst-case scenario. This study confirms that soils in old-growth forests play a significant role in carbon sequestration. It also suggests that climate change may affect the potential of these forests to store SOC not only in the long term but also in the coming years. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) sequestration is a key function of natural and semi-natural ecosystems. Restoring this property in terrestrial ecosystems has become central to the EU's climate change mitigation and adaptation strategies. However, SOC sequestration is a widely misunderstood concept. The different methodological approaches used to investigate and compare SOC stock under sustainable agricultural practices play a key role in reinforcing misconceptions about this complex process. This commentary paper aimed not only to provide a clear definition of SOC sequestration, but also to interpret the results that can be obtained for SOC stock change estimation using the SOC stock difference and the paired comparison methods, as well as to identify the soil carbon-related processes that achieve climate mitigation. SOC sequestration can be defined as the progressive increase in a site's SOC stock compared with pre-intervention via a net depletion and transfer of atmospheric CO2 into the soil, where it is retained as soil organic matter (SOM), by plants, plant residues, or other organic solids such as the material derived from the organic fraction of farming solid waste, which can be used as a fertilizer (e.g., manure, compost, biochar, and digestate), and that is produced or derived from that land unit. To date, the most appropriate way to determine whether a land unit's soil is a sink or rather a source of atmospheric CO2 is to implement the SOC stock difference method, provided the non-occurrence of carbon exchange between ecosystems. [ABSTRACT FROM AUTHOR]

To assess the degree to which it has met its commitments under the Paris Agreement, Morocco is called upon to carry out carbon assessments and transparent evaluations. Within the forestry sector, little is known about the role of Morocco's forests in contributing to carbon uptake. With this aim, we applied for the first time in the literature the 3-PG model to Cedrus atlantica ((Endl.) Manetti ex Carrière, 1855), which represents about 131,800 ha of Morocco's forest area (i.e., Azrou forest). Through the Differential Evolution-Markov Chains (DE-MC) we tested and assessed the sensitivity and calibrated the 3-PG model. This process-based model provided significant results regarding the carbon sequestration capacity. The results showed the following: i. Parameters related to stand properties, canopy structure, and processes, as well as biomass partitioning, are the most important or sensitive for the performance of the model; ii. The DE-MC method optimized the values of the 3-PG parameters which was confirmed by the means of the Gelman–Rubin convergence test; iii. According to the predictions of the calibrated 3-PG, the Net Primary Production in the pure Azrou forest varies between 0.35 and 8.82 tC. ha − 1. yr − 1 , it is equal in average to 5.48 tC. ha − 1. yr − 1 , which given the total area corresponds to 7918 tC. ha − 1 . [ABSTRACT FROM AUTHOR]

Areas covered by seminatural grasslands have been in constant decline for decades in Europe. This trend is particularly strong for mountain territories, where such traditional agricultural practices as cattle grazing are no longer economically feasible. This study was conducted in the subalpine pasture of Cinte Tesino (TN, Italy), where local farmers have applied the following different management strategies: shorter and longer grazing durations during the season and a complete abandonment for the last 15 years. We aimed to study how these different management strategies impact the functioning and diversity of vegetation and the chemical and biological characteristics of the soil. Species richness was higher in plots subjected to longer grazing with a prevalence of D. caespitosa in terms of biomass share. A decline in species richness in abandoned plots was accompanied by an increase in the share of other graminoids in collected biomass. A concomitant increase in leaf N concentration and light availability in grazed plots resulted in higher photosynthetic efficiency in some species, as revealed by the δ13C of plant tissues. Soils under grazing were characterised by a higher concentration of total and extractable N, almost doubled microbial biomass C and increased extracellular enzymes activity, evidencing nutrient cycling mobilization. While the microbial pool was characterised by lower mineralization rates, C was lost from the soil with 15 years of abandonment. The longer grazing season demonstrated to be the most beneficial, promoting species richness, C accumulation and better soil microbial functioning. A change in soil pH from strongly acidic to moderately acidic with longer grazing is likely one of the important factors adding to the success in the functioning of primary producers and decomposers in this site. [ABSTRACT FROM AUTHOR]