Soil carbon and wood decay models in Nigeria’s Niger Delta environment

Decaying of wood is a major factor in modelling global carbon emissions and their effect on climate change. When not properly considered, trees used in urban greening have been observed to cause hazards and do a disservice in terms of carbon storage due to their degradation. This degradation process is aided by species properties and climatic and biological factors, but the quantitative characteristics of this process on commonly used avenue trees in Nigeria are scarce. The decay rate of wood-block samples of six commonly used avenue trees (Azadirachta indica, Gmelina arborea, Delonix regia, Casuarina equisetifolia, Musanga cecropiodes, and Ficus elastica), as well as soil carbon changes beneath the wood blocks, were monitored under natural varying climatic conditions (Soil temperature, air temperature, relative humidity) and incidence of termite attack over a period of 16 weeks. Soil and air temperature showed a quadratic trend with decay rate, with p-values less than 0.05 and 0.10, respectively, while density and incidence of termite attack were negatively linear (p<0.05) and positively linear (p<0.01), respectively. Among the species, D. regia had the highest coefficient for predicting decay rate. Soil depth and wood density were significant predictors of soil carbon accumulation from decaying wood samples. Soil temperature and other climatic variables of a region should be considered for various tree planting and management projects to discourage the selection of trees with a high decay rate and carbon loss in the area, such as D. regia.