Accurate estimation of forest biomass to enable the mapping of forest C stocks over large areas is of considerable interest nowadays. Airborne laser scanning (ALS) systems bring a new perspective to forest inventories and subsequent biomass estimation. The objective of this research was to combine growth models used to update old inventory data to a reference year, low-density ALS data, and k-nearest neighbor (kNN) algorithm Random Forest to conduct biomass inventories aimed at estimating the C sequestration capacity in large Pinus plantations. We obtained a C stock in biomass (W t -S) of 12.57 Mg·ha −1 , ranging significantly from 19.93 Mg·ha −1 for P. halepensis to 49.05 Mg·ha −1 for P. nigra, and a soil organic C stock of the composite soil samples (0-40 cm) ranging from 20.41 Mg·ha −1 in P. sylvestris to 37.32 Mg·ha −1 in P. halepensis. When generalizing these data to the whole area, we obtained an overall C-stock value of 48.01 MgC·ha −1 , ranging from 23.96 MgC·ha −1 for P. halepensis to 58.09 MgC·ha −1 for P. nigra. Considering the mean value of the on-site C stock, the study area sustains 1,289,604 Mg per hectare (corresponding to 4,732,869 Mg CO 2 ), with a net increase of 4.79 Mg·ha −1 ·year −1 . Such C cartography can help forest managers to improve forest silviculture with regard to C sequestration and, thus, climate change mitigation.In addition to biomass, C is also stored in litter and forest soils. In fact, soils are the largest reservoir of terrestrial C, for both organic and inorganic forms [6]. Soil organic carbon (SOC) can be stored in soils for thousands of years under, suitable conditions, and is a vital component of plant nutrient cycles [7]. Forest management aimed at increasing stand growth has been shown to be effective in increasing the C sequestration capacity [8,9]. Thinning treatments improve health and tree vigor, increasing forest productivity [10], while the soil C content shows a slight decrease in the first stages, recovering its level and increasing once the canopy is restored [11].Accurate estimation of forest biomass to produce spatially explicit mapping of forest C stocks over large study areas is of considerable interest nowadays [12]. In this regard, the field-based inventory is the most common method for evaluating the dendrometric characteristics and stand dynamics of forests. These classic forest inventories have a high demand for labor, are expensive, and require lots of field plots to obtain full inventory data for large areas on the ground [13,14]. Thus, with the advances in remote sensing techniques, these traditional methods are being replaced or supplemented with Light Detection and Ranging (LiDAR) techniques, which provide stand data over large areas, optimizing time and costs. LiDAR technology brings a new perspective to forest inventories by directly providing three-dimensional information on the entire surface [12].LiDAR (Laser Imaging Detection and Ranging) systems from an airborne platform (airborne laser scanning, ALS) are equipped with a scanning device th...