In hyperarid ecosystems, vegetation often forms patchy so-called fertile islands, structured by perennial pillar plants that strongly influence soil carbon dynamics and ecosystem functioning. This study quantified their effects on soil organic carbon (SOC), soil inorganic carbon (SIC), and SOC quality in two areas of Sharaan National Park, with area 1 corresponding to canyon-protected arid woodland systems and area 2 to open dune-dominated environments, using the Rock-Eval (R) Oxypure method, a rapid thermal oxidative technique enabling simultaneous characterization of organic and inorganic carbon fractions. SOC stocks ranged from 2.6 to 72.5 Mg C ha(-1), with mean values of 4.3 +/- 2.6 to 32 +/- 14 Mg C ha(-1) in area 1 and 4.3 +/- 2.6 to 51.1 +/- 19.4 Mg C ha(-1) in area 2. In contrast, SIC stocks remained low, averaging 6.9 +/- 4.1 Mg C ha(-1) and 6.3 +/- 3.1 Mg C ha(-1) in areas 1 and 2, respectively. In area 1, the nitrogen-fixing species Retama raetam and Vachellia gerrardii were associated with higher SOC contents, whereas in area 2, Haloxylon persicum structured SOC distribution throughout the soil profile. SOC stocks were primarily controlled by soil depth and stable carbon pools in area 1, and by exchangeable cations (CaO, MgO) in area 2. The studied soils were characterized by a predominance of labile SOC pools, with relatively large labile SOC fractions observed at all soil depths. The results showed that the influence of pillar plants on SOC pool sizes was minor compared to control soils. SOC dynamics in hyper-arid environments are governed by the interaction between limited organic inputs, severe abiotic constraints (low moisture, high temperatures, sandy texture), and localized biotic hotspots (e.g., plant colonies and nitrogenfixing species). Our findings further demonstrate that certain plant species play a crucial role in enhancing deep-soil carbon stabilization mechanisms, which are essential for the development of sustainable carbon sequestration strategies in arid and hyper-arid ecosystems. Overall, these results highlight the importance of deep soil horizons as key carbon reservoirs in hyperarid environments and demonstrate the relevance of Rock-Eval (R) Oxypure for resolving SOC fractions in low-carbon systems.