Abstract
Selective logging is among the main causes of tropical forest degradation, but little is known about its effects on greenhouse gas (GHG) fluxes from highly weathered Ferralsol soils in Africa. We measured soil CO2, N2O, and CH4 fluxes, and their soil controlling factors at two forests that had undergone conventional selective logging and reduced-impact logging in Cameroon. Each logging system had four replicate plots, each included the disturbed strata (road, logging deck, skidding trail, and felling gap) and an undisturbed reference area. Measurements were conducted monthly from September 2016 to October 2017. Annual GHG fluxes ranged from 4.9 to 18.6 Mg CO2–C, from 1.5 to 79 kg N2O–N, and from − 4.3 to 71.1 kg CH4–C ha−1 year−1. Compared to undisturbed areas, soil CO2 emissions were reduced and soil CH4 emissions increased in skidding trails, logging decks and roads (P < 0.01) whereas soil N2O emissions increased in skidding trails (P = 0.03–0.05). The combined disturbed strata had 28% decrease in soil CO2 emissions, 83% increase in soil N2O emissions, and seven times higher soil CH4 emissions compared to undisturbed area (P ≤ 0.01). However, the disturbed strata represented only 4–5% of the area impacted in both logging systems, which reduced considerably the changes in soil GHG fluxes at the landscape level. Across all strata, soil GHG fluxes were regulated by soil bulk density and water-filled pore space, indicating the influence of soil aeration and gas diffusion, and by soil organic carbon and nitrogen, suggesting the control of substrate availability on microbial processes of these GHG.
Highlights
Selective logging is the most common management practice used for timber harvesting in the tropics
Across the 12-month measurement period, soil CO2, N2O, and CH4 fluxes from the undisturbed reference areas did not differ between Conventional logging (CL) and reduced-impact logging (RIL) (P = 0.15–0.41; Fig. 1a–f; Table 1)
Soil CO2, N2O and CH4 fluxes were all affected by selective logging
Summary
Selective logging is the most common management practice used for timber harvesting in the tropics. Reduced-impact logging (RIL) has a management plan with a set of measures (e.g., prelogging forest inventory, mapping of merchantable trees, planning of logging infrastructures, directional tree-felling techniques, and post-harvest closure of roads and skidding trails) to minimize the negative impacts of logging (Putz et al 2008). Both selective logging systems, can result in significant soil organic carbon (SOC) loss and decrease in soil fertility (Tchiofo Lontsi et al 2019), which may lead to forest degradation. These can, in turn, affect soil microbial communities and their function on greenhouse gas (GHG) regulation (Schnurr-Putz et al 2006; Hartmann et al 2014)
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