This report presents a methodology to assess the stocks of carbon pools both aboveground and belowground under various land-use systems, the status of their biodiversity and that of land degradation. The report also describes methods to analyse win-win land use and land management scenarios. These aim to reduce land degradation while enhancing soil fertility, land productivity and carbon sequestration. The report presents the related models and software tools and the test results of case studies in selected areas of Mexico and Cuba.
The methodology has been applied in the various watersheds of the case study areas. It can be summarized as follows:
carbon stock assessment, involving computations of aboveground biomass (from field measurements and satellite image interpretation) and estimates of belowground biomass (derived from aboveground computations);
carbon dynamics simulation and estimation of carbon sequestration considering actual land use, using the Roth C-26.3 and CENTURY (V.4.0) models;
land suitability assessment for each land unit in the watershed for potential land utilization types, involving: pre-selection of crops, trees and grass mixes according to potential on the basis of high carbon photosynthetic assimilation (C3 and C4 pathways) and multicriteria climatic suitability, and suitability in terms of topography, wetness, soil fertility, physical and chemical characteristics (using decision-tree models in the Automated Land Evaluation System);
carbon dynamics simulation and estimation of carbon sequestration considering potential land-use types, using the Roth C-26.3 and CENTURY (V.4.0) models;
computation of carbon totals per land unit and per land-use type for current land use;
estimation of carbon totals from potential land-use patterns;
computation of biodiversity indices at the field sampling sites and their extrapolation to the watershed area;
development of a customized database for biodiversity computations;
computation of land degradation indices (physical, biological and chemical) at the sampled sites and extrapolation to all the watershed area;
application of an analytical hierarchy process model for participatory decision-making regarding potential land-use scenarios including carbon sequestration.
The case studies involve three sites: Bacalar and Texcoco (Mexico) and Rio Cauto (Cuba). One Mexican site is located in a dry, poverty-stricken, degraded highland area in central Mexico with high population pressures on resources; the other in a tropical semi-deciduous forest area with very low population pressure, a high incidence of poverty and lower levels of environmental degradation. The Cuban site is located in the Province of Holguin in the Rio Cauto watershed. It is a dry, tropical area with various levels of resource degradation and a high incidence of resource constraints.
Data from each of the three sites were used to create georeferenced databases. Carbon simulation models (i.e. RothC-26.3 and CENTURY) were run using these databases.
The study also investigated the effect of alternatives to slash-and-burn agriculture on carbon dynamics in two locations in the Yucatan Peninsula (Quintana Roo), Mexico. Scenarios of land-use changes were generated through the models, and management approaches relating to soil organic matter and carbon dynamics necessary for stabilizing slash-and-burn agriculture were identified.
Soil-C, a customization of the CENTURY model (v. 4.0) including visual input and output interfaces and parameterization options for tropical and subtropical conditions, was implemented (beta version).
The CENTURY model was integrated fully with GIS via customization (i.e. software development with Visual Basic and scripts) in order to provide VISUAL CENTURY-GIS with map visualization capabilities as part of Soil-C. This enables non-expert users to run the carbon dynamics simulation model.
The study included comprehensive research on measurements of biomass and carbon stock estimation. A methodology for plant biodiversity estimation was also researched. Procedures were elaborated for assessing biomass and carbon stock of relatively large areas through field measurements and remote sensing.
A dedicated Internet-GIS system was developed to serve map and attribute data from the three case study sites, and to allow for remote spatial queries and basic GIS functionality on the Internet.
The software tools are designed to facilitate their customization and transferability to other areas.