Estimating carbon fluxes from various agroecosystems in U.P. La Granja Station, La Carlota City, Negros Occidental: A biomodelling approach.

Date

10-2000

Degree

Bachelor of Science in Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Virginia C. Cuevas

Abstract

The Soil Changes Under Agroforestry (SCUAF) model was used to study the fluxes of carbon from sugarcane, corn and mahogany agroecosystems in U.P. La Granja Research and Training Station, La Carlota City, Negros Occidental. The model was calibrated using available biophysical data on each of the agroecosystem, data from related studies and default values in the SCUAF. At the end of the 20-year simulation period, the mahogany system had the lowest cumulative soil loss of 2,703 kg/ha, compared to 340,142 and 145,075 kg/ha for sugarcane and corn, respectively. The high rates of soil loss resulted to increased soil carbon depletion in all the agroecosystems, with the sugarcane system having 90 percent of its initial soil carbon depleted, 87 percent for corn, and 34 percent for mahogany. The SCUAF also predicted decreasing biomass production for the sugarcane and corn systems with 54 and 49 percent reduction, respectively. Biomass production in the mahogany system cumulatively increased from an initial value of 6,048 kg/ha to 108,607 kg/ha because of lower rates of carbon depletion due to erosion. The rates of carbon sequestration for the annual agroecosystems declined steadily while the mahogany system showed the opposite trend. By the end of the simulation period, half of the total carbon sequestered in the mahogany system (94,195 kg/ha) is in the plant biomass, while majority of the carbon in the sugarcane (12,819 kg/ha) and corn systems (8,677 kg/ha) are in the soil. This study highlights the importance of maintaining soil carbon to improve plant growth. Low plant growth is predicted in agroecosystems with high reduction of soil carbon due to erosion. The decreasing trends of soil carbon in the sugarcane and corn systems suggests that carbon inputs from the humification and non-burning of harvest residues cannot compensate for the faster reduction of soil carbon by erosion. Erosion indiscriminately removes the finer and most fertile fractions of topsoil where soil carbon and other soil nutrients are found. The maintenance of soil carbon is an indicator of soil quality because of its connection with soil nutrient availability and physical status. Intensively cultivated agroecosystems have the potential to sequester carbon through the humification of litter in the soil. Although tree plantations can sequester more total carbon as biomass, soil organic carbon is a more a stable carbon sequestering mechanism than plant biomass. The use of a simple erosion/productivity model like the SCUAF shows that simulation modelling can be an alternative approach to expensive and conventional experimental research in studying the dynamics of carbon in agroecosystems.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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