Carbon Storage Contributions of Remnant Forest Patches in Banana-Dominated Agroecosystems in Southern Philippines

Remnant forest patches within agricultural landscapes may play an underappreciated role in tropical carbon storage. Understanding their carbon storage contribution will inform land-use policies to balance economic production with forest-based climate mitigation strategies, especially in tropical developing countries where agriculture dominates. This study quantified and compared carbon stocks of five biomass pools (overstorey, understorey, litter, roots, and soil) using 54 nested plots established in nine pairs of remnant forest patches and adjacent banana (Musa spp.) agroecosystems in Bukidnon, Southern Philippines. Results showed that forest patches stored most carbon in the overstorey layer (65-75%) followed by roots (18-22%), litter (5-8%) and understorey layers (< 2%). Banana agroecosystems stored more carbon in the pseudostems and litter layer with 40-45% and 45-50% of the total biomass carbon, respectively, while roots had only 8-10%. The absence of understorey vegetation in banana plantations may indicate the intensive nature of management practices in this agroecosystem. Forest patches stored significantly higher carbon in the overstorey (77.06 ± 69.71 Mg C ha−1), understorey (1.24 ± 0.44 Mg C ha−1), and roots (20.43 ± 17.23 Mg C ha−1). Interestingly, litter carbon was higher in banana agroecosystems (20.40 ± 12.15 Mg C ha−1) than in forest patches (7.67 ± 3.43 Mg C ha−1) likely due to the practice of leaving banana residues after harvest. Total biomass carbon was two to three times greater in forest patches (106.39 ± 88.40 Mg C ha−1), with significantly higher carbon accumulation (2.62 ± 2.18 Mg C ha−1 yr−1) and CO2 fixation rates (9.60 ± 7.98 Mg CO2-eq ha−1 yr−1) than banana plantations. Although SOC levels were statistically comparable between the two land uses, further research is needed to confirm whether the apparent stability of SOC in banana plantations is sustainable or whether it represents a transient stage before eventual depletion. Nonethless, we recommend to prioritize the conservation and restoration of forest patches as permanent features within agricultural landscapes to optimize carbon storage and mitigate ecological degradation.