Landscapes Forest and Global Change - ESA - Escola Superior ...

P. González-Moreno et al. 2010. The influence of spatial structure on natural regeneration and biodiversity
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However, proximity relations could be complicated considering the relief. Mountain areas are
anisotropic surfaces where the downhill dispersal of propagules will be easier due to the direct
effect of gravity (Ohsawa et al. 2007) or because animal dispersal vectors move downhill in
order to save energy (Li and Zhang 2003). Patch geometry considers the shape or area of
patches and the effect that those characteristics could have on internal patch dynamics. Patch
geometry determines the edge effect (Turner, Gardner, and O'Neill 2001). The edge has drier
conditions, with more light and it receives the visit of open habitat species. These differences
influence species composition and thus biodiversity and probability of propagules arrival.
Turner et al., (2001: 3) defines landscape as an area that is spatially heterogeneous in at least
one factor of interest. This heterogeneity, can be observed at different scales. Thus, given a
landscape with a determined scale, it is possible to identify mosaics of patches within patches.
This nested model of mosaics is important to understand the ecological processes because it
implies that the spatial configuration of mosaics at different scales are interconnected.
Therefore, not only the vegetation context and patch geometry will affect the performance of
recruitment of species but also the mosaic of microhabitats within plantation patches (i.e.
internal vegetation structure). This structural diversity can be obtained from texture analysis of
high resolution imagery (Hepinstall and Sader 1997; St-Louis et al. 2006). Texture is the spatial
distribution of different gray-levels in the same band of the image (Haralick, Shanmugam, and
Dinstein 1973). Considering that each gray-level is the spectral response to a specific vegetation
type or microhabitat, the analysis of the spatial combination of gray-levels can give valuable
information about the spatial structure. This type of analysis can be done applying the Gray
Level Co-occurrence Matrix (GLCM) developed by (Haralick, Shanmugam, and Dinstein
1973). This method gives the probability that two pixels in the same image window have same
tone in a given distance and direction.
In a previous research in the same study area we evaluated the effect of several environmental
gradients (climate, distance to oak vegetation and stand density) on biodiversity and plant
regeneration of pine plantations (Gómez-Aparicio et al., 2009). Here our objective was to
evaluate specifically the effect of the spatial configuration of pine plantations on tree
regeneration and plant diversity at different scales. Specifically we asked how is natural
regeneration and plant diversity of different species within plantation patches related at
landscape scale to the vegetation context of pine plantation patches (proximity to seed source)
and plantation patch geometry (area and patch shape complexity) and at patch scale to the
internal structural diversity of pine plantations patches
2. Methodology
2.1 Study site
Sierra Nevada National Park (Southeast Spain) is a mountain region with an altitudinal range
between 860 m and 3482 m. It has an extension of more than 2000 Km 2 , and a main length of
90 Km. Annual average temperature decreases in altitude from 12-16 ºC bellow 1500 m to 0 ºC
above 3000 m. Precipitation is scarce in summer, while the winter precipitation is mainly in
form of snow over 2000 m. The average annual precipitation oscillates from less than 250 mm
in the lowest and Eastern part of the mountain, to more than 700 mm in the highest peaks.
2.2 Dataset
Regeneration and plant diversity variables were obtained from the Forest Inventory of Sierra
Nevada National Park collected during 2004-2005 (SINFONEVADA). 275 inventory plots
within pine plantation were selected for the analysis covering a gradient from 974 to 2439 m
a.s.l. Plot size ranged from 300 to 400 m 2 . Two additional subplots were established within each
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.