Coupling Landscape Patterns and Ecological Processes - Landscape Ecology for Sustainable Environment and Culture - page 10

density, characterized by a tendency towards random or even tree spacing. Schurr
et al. ( 2004 ), using a series of integrated models, found that seed dispersal played a
larger role than root competition in shaping the vegetation pattern in Karoo
scrubland, South Africa. Bleher et al. ( 2002 ), using an individual-based, spatially-
explicit model, found that the dispersal distance of seed and tree density are the
major factors influencing tropical forest patterns.
1.3.3 Models on Coupling Landscape Patterns
and Ecological Processes
The details of building the coupling models for landscape patterns and ecological
processes are as follows: first, building model structure, writing codes, and
applying modeling tools and GIS software to integrate the pattern and process
models; and second, transferring or sharing the data across various models to
extend the models' functions. Coupling models effectively tap the advantages of
various specialized models, and validate and complement each component model
through cross-checking. The major coupling models include the meta-population,
vegetation dynamic, biogeochemical cycle, and hydrological models. Childress
et al. ( 2002 ) employed LMS (Land Management System) to integrate the EDYS
(Ecological Dynamics Simulation Model) model and the hydrological model of
CASC2D (Cascade 2 dimensional sediment), embedding the hydrological model
with the factors of climate, content of soil, water, and nutrients, as well as plant
growth, fire, disturbance, and management measures. The PLM links topography,
hydrology, nutrients, vegetation and land use, and simulates the ecological pro-
cesses by use of Pat-GEM (Patuxent-General Ecosystem Model), which success-
fully quantifies the matter cycles among pixels in rasterized landscapes (Costanza
et al. 2002 ). Similar coupling models include: IMAGE (Integrated Model to
Assess the Global Environment; Alcamo et al. 1998 ) and LANDIS (Land Infor-
mation System) pattern model (Mladenoff et al. 1996 ).
1.4 Landscape Patterns and Soil Erosion Processes
Links between land use/land cover and soil erosion provide an entry point to explore
the relationship between landscape patterns and ecological processes. The complex
mechanisms between landscape pattern and soil erosion at various scales have
become a frontier in earth sciences (Fig. 1.3 ; Huang et al. 2003 ; Wang et al. 2009b ).
The pivotal driving factors on soil erosion vary greatly depending on the spatial scale
(Table 1.1 ). Landscape pattern, represented by land use and vegetation structure,
influences the runoff yield and soil erosion by affecting multiple factors, i.e.,
evapotranspiration, rainfall interception, soil water infiltration, and underground