Tesis doctoral por el sistema de compendio de publicaciones.Tesis con mención internacional
Ecosystem services (ES) can be defined as the goods and services that
ecosystems provide to the society for its well-being. The importance of ES in different
fields of environmental sciences, ecology and land planning has been highlighted in
recent years. The relevance of spatial aspects of the data describing ecosystems has
driven the use of several spatial analysis techniques and methods for ES assessment.
However, the extended use of Land Use/Land Cover maps may lead to uncertainty and
bias due to oversimplification and generalization of the study area and associated elements.
Ecosystem services and the ecological processes that generate them are
strongly related. These processes are not constant at all spatial scales and display high
levels of spatial and temporal heterogeneity. Thus, appropriate selection of the data
sources and analytical methods used to characterize the ecosystems is essential for
development of accurate models and minimization of potential bias in the assessments.
The general objective of this research was to carry out a multi-scale analysis of the
spatial pattern of ES supply and the distribution of some ecosystems that provide the
ES. Different data sources were used to characterize agricultural and forest landscapes
in the NW Iberian Peninsula. Forests are major components of the landscape in the
area, and several authors have highlighted the wide range of ES that these
ecosystems provide. We first characterized the ecosystems in order to identify the
areas where the main forest tree species in the area are growing. Quercus robur L. and
Castanea sativa Mill. forests are mainly located in zones below 500 m where low
temperatures do not usually occur. By contrast, Quercus petraea (Matt.) Liebl. and
Fagus sylvatica L. forests are associated with lower temperature zones at higher
elevations. We then used digital soil cover data to analyze the pattern of supply of six
ES (provision of food, materials and energy, regulation of climate and erosion, and
cultural services) by spatial statistical methods. We used the lacunarity metric to
analyze the regularity of the no supply areas at multiple spatial scales. We found some
divergence in the thresholds of spatial clustering of the ES and obtained higher values
for food and materials provision. We also identified the spatial scales (extensions) at
which the probability of supply of each ES is maximized. In addition, we used a
functional approach to analyze the pattern of supply of a similar set of ES. We
developed spatial models of these ES on the basis of Net Primary Production,
calculated for a phenological year from Landsat 5-TM data and using the ¿NDVI index.
The index was then combined with some socio-environmental variables. We used two
multi-scale metrics (lacunarity and four term local quadrat variance) to analyze the
observed patterns. The analysis revealed clustered patterns for provisioning services
and a more extended distribution for regulating services, with different characteristic
spatial scales for each type. Finally, we used a high resolution forest thematic map to
assess the potential supply of some ES from forest ecosystems. We thus explored the
spatial relationships between these ES and found some differences between the ES
associated with native forests and those supplied by forest plantations of exotic
species. We also determined the zones with a high density of elements involved in ES
supply at different spatial scales. This enabled us to identify the locations of the most
important areas for some ecosystems in relation to the supply of different ES in the NW
Iberian Peninsula. Finally, we also analyzed the most characteristic spatial scales and
the effect of different types of data sources on ES assessment.
