Observatorio de I+D+i UPM

Memorias de investigación
Thesis:
Land use and vegetation dynamics in a silvopastoral system: Effect on their ecological structure and carbon storage
Year:2018
Research Areas
  • Soil resources,
  • Remote sensing
Information
Abstract
The landscape in the old agricultural border in Nicaragua is a fragmented matrix in a livestock environment involving many different land uses with different tree cover and carbon storage. The municipality of Matiguás is a representative area of the livestock landscape in the sub-humid tropics. In order to assess land use and land cover (LULC) changes in Matiguás, the most representative traditional silvopastoral systems (TSPS) in the area were selected: shrubland, intervened secondary forest, pasture with high tree density, pasture with low tree density and degraded pasture. As an alternative to monitor and quantify these changes, remote sensing was used. In the last two decades, before Landsat images were free, developing countries could not afford monitoring through remote sensing because of the high cost of acquiring satellite imagery and commercial software. However, Landsat time series nowadays allows the characterization of changes in the vegetation across large areas over time. Nearly cloud free Landsat scenes: A Landsat 5 Thematic Mapper scene from 1986 and a Landsat 8 OLI scene from 2015 have been the datasets used in the study. A process chain following Jensen?s (2009) four-step definition of the remote sensing process was conceptually developed and implemented, based on free open source software components and by applying the Random Forest algorithm. A conceptual LULC classification scheme representing TSPS was developed. Although the imagery shows a heterogeneous surface cover and mixed pixels, it was possible to achieve promising classification results with out-of-the bag errors below 13% for both images along with an overall accuracy level of 85.9% for the 2015 subset and 85.2% for the 1986 subset. The classification shows that from 1986 to 2015 (29 years) the intervened secondary forest increased 2.6 times while the degraded pasture decreased by 34.5%. The livestock landscape in Matiguás is in a state of constant transformation, but the main changes head toward the positive direction of tree cover recovery and an increase number of areas of natural regeneration. Digging deeper into the analysis, each land use ecological structure was assessed in terms of tree richness and diversity index. Our study estimated the above and belowground biomass carbon using allometric equations. Soil organic carbon was evaluated at four depths: 0-10 cm, 10-20, 20-40 and 40-100 cm. Of the land uses studied, shrubland had the highest diversity. The biomass carbon ranged from 1.9 to 13.2 t C ha-1 for degraded pasture and intervened secondary forest, respectively. The highest soil organic carbon storage at 1 m depth was for intervened secondary forest (163 t C ha-1), whereas degraded pastures had the lowest value (76 t C ha-1), rather higher than biomass values. Since SOC is the largest pool of total carbon, its evaluation should be normalized down to a depth of at least one meter. Increasing tree coverage in degraded and low-tree density pastures can contribute not only to enhance carbon sequestration but also to restore degraded lands in livestock landscapes. Comparing the total biomass carbon stocks from 1986 and 2015 images, our results indicate an increasing trend in that period (24%). The results indicated that Matiguás is characterized by a great dynamism in terms of land use changes with simultaneous processes of loss and gain of tree cover, with a net balance of gains. The transformation of the landscape does not mean a reduction of livestock areas, but rather, a change in the concept of livestock as we know. Natural regeneration is playing an important role, being a low cost solution to change land use, improving the tree cover in pasture and boost with the conservation and protection of aquatic resources, without a capital inversion
International
No
Type
Doctoral
Mark Rating
Sobresaliente cum laude
Date
23/07/2018
Participants
  • Autor: Aura Yorlene Cardenas Velasquez (UPM)
  • Director: Chiquinquira Hontoria Fernandez (UPM)
  • Director: Ana Maria Moliner Aramendia (UPM)
Research Group, Departaments and Institutes related
  • Creador: Grupo de Investigación: Calidad de Suelos y Aplicaciones medioambientales
  • Departamento: Producción Agraria
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