Effect of Land Use Management Patterns on Mineralization Kinetics of Soil Organic Carbon in Mount Bambouto Caldera Area of Cameroon

Formeluh Abraham Toh,Lawrence Monah Ndam,Tsi Evaristus Angwafo,Ngosong Christopher

doi:10.4236/ojss.2020.109021

Abstract

Soil organic carbon (SOC) mineralization was carried out on soil samples collected from two depths: 0 - 20 cm and 20 - 40 cm for all land use (LU) types (grasslands, croplands, natural forest/fallow lands, cocoa/palm plantations, and settlement/agro-forests). Microbiological analyses were carried out by measuring microbial activity in 40 g of dried soil samples wetted to 60% water holding capacity and incubated at 27 °C. Carbon dioxide (CO2) emission was measured for 10 weeks using a CO2 trap. Descriptive and graphical analyses of CO2 respiration were done using CO2 emission data. Models were developed to describe CO2 respiration and the first order kinetic model provided best fit to C-mineralization. Potentially mineralizable carbon (Co) and C-mineralization rate were higher in grasslands than other LU types, indicating a higher rate of microbial activity and carbon cycling. Metabolic quotient was higher in forest/fallow lands and reflects greater stress of the microbial community and a high requirement of maintenance energy. Grasslands enhanced more SOC accumulation and decomposition, suggesting a better carbon sink than other land use and management systems (LUMS). Microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) varied across LU patterns with maximum values in grasslands and minimum values in natural forest/fallow lands insinuating better soil quality for grasslands. MBC and SOC positively correlated with Co and C-mineralization, which intimates that C-mineralization is influenced by availability of MBC and SOC. Metabolic quotient (qCO2) negatively correlated with microbial quotient (MBC:SOC), depicting that higher values of qCO2 signify difficulties in using organic substrates during microbial activity as a result of low MBC:SOC. Changes in LUMS affected the mineralization kinetics of SOC in the study area.

Highlights

Land use and management patterns are inherently associated with changes in soil nutrients and soil quality parameters, which affect the immediate biophysical environment and agricultural productivity
High Soil organic carbon (SOC) and Microbial biomass carbon (MBC) result in high soil respiration [23] [54], which means the high mineralizable carbon in grasslands indicates a more decomposable organic matter while the low mineralizable carbon in other land use and management systems (LUMS) signifies a more difficult to decompose organic matter
More CO2-C was mineralized in grassland than other LUMS, indicating higher rate of microbial activity and carbon cycling

Summary

Introduction

Land use and management patterns are inherently associated with changes in soil nutrients and soil quality parameters, which affect the immediate biophysical environment and agricultural productivity. Steady population growth increasingly triggers the conversion of natural vegetation to different land use types and management patterns [3] [4] with significant changes in soil properties and associated soil health implications. The effects of land use changes on soil carbon pools and atmospheric CO2 concentrations have various environmental implications [3] [5] [6] since soils serve as C sinks and are large sources of atmospheric carbon supply. There is need to be abreast with variations that occur in the organic carbon pool due to land use changes since they have implications on the sustainable management of ecosystems [8] [9]

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