Passive and Active Restoration Strategies to Activate Soil Biogeochemical Nutrient Cycles in a Degraded Tropical Dry Land

The potential use of two restoration strategies to activate biogeochemical nutrient cycles in degraded soils in Colombia was studied. The active model was represented by forest plantations of neem (Azadirachta indica) (FPN), while the passive model by successional patches of native plant species was dominated by mosquero (Croton leptostachyus) (SPM). In the field plots fine-litter traps and litter-bags were established; samples of standing litter and surface soil samples (0–10 cm) were collected for chemical analyses during a year. The results indicated that the annual contributions of fine litterfall in FPN and SPM were 557.5 and 902.2 kg ha−1, respectively. The annual constant of decomposition of fine litter (k) was 1.58 for neem and 3.40 for mosquero. Consequently, the annual real returns of organic material and carbon into the soil from the leaf litterfall decomposition were 146 and 36 kg ha−1 yr−1 for FPN and 462 and 111 kg ha−1 yr−1 for SPM, respectively. Although both strategies showed potential to activate soil biogeochemical cycles with respect to control sites (without vegetation), the superiority of the passive strategy to supply fine litter and improve soil properties was reflected in higher values of soil organic matter content and cation exchange capacity.