Space-time variability in mediterranean pastures analyzed with diversity parameters

Abstract

Different parameters of diversity and spatial niche amplitude (Pielou, 1975, Pineda et aL, 1981 have been used to describe the spatial organization of mediterranean grasslands in Central Spain. A slope sampled by 480 contiguous 8 X 8 cm quadrats proved to have a homogeneous floristic distribution when it was divided into 160 parts and maximum heterogeneity when divided into 4 sectors. These sectors corresponded to different geomorphological zones of the slope. The complexity of vegetation distribution on the slope was reflected by differences in organization -measured by diversity parameter A = H(P/E)/log a N (number of plots) between the parts obtained by division. The presence of low-entropy species -specialists -and high entropy species -generalists -was related to the different scales of slope organization. The spatial distribution of plants was compared for different successional stages. Multivariate analysis of sampling plots confirmed previously identified organizational characteristics and clarified the nature of transitions between communities of different floristic composition or structure.

Fine‐scale spatial structure in a grassland community: quantifying the plant’s‐eye view

“…The information theory used by Bartha et al is after Juhasz-Nagy (1984) and is related to BQC. Analyses that relate to the plant's-eye view are in bold Amarasinghe & Pemadasa (1982) 1.0 Transect of cells BQV, BQC Zamfir et al (1999) 1.0 Transect of cells DCA De Pablo et al (1982) 0.64 Transect of cells H(E.P) Mahdi & Law (1987) 0.28, 0.13, 0.03 Separate plant-centred areas Densities within areas Kershaw (1962) 0.25 Transect of cells BQV, BQC Gibson & Greig-Smith (1986) 0.25 Transect of cells BQV Gibson (1988) 0.25 Transect of cells TTLQV, 3TLQV, TTLCA, DCA Bartha et al (1995) 0.25 Transect of cells Information theory Edwards et al (1996) 0.25 Transect of cells TTLQV Stowe & Wade (1979) 0.16 Transect of points J Agnew & Gitay (1990) 0.16 Transect of cells TTLQV Kershaw (1958Kershaw ( , 1959 0.05 Transect of points BQV, interspecific correlations Kershaw & Tallis (1958) 0.05 Transect of points BQV, interspecific correlations Turkington & Harper (1979) 0.05 Transect of points BQC Galiano (1985Galiano ( , 1986 0.04 Transect of cells BQV Wilson et al (1987) 0.04 Transect of cells Variance in species richness Van der Hoeven et al (1990) 0.04 Grid of cells Lagged Moran's I Van Rijnberk & During (1990) 0.016 Grid of points Z-correlograms Watkins & Wilson (1992) 0.016 Grid of cells Variance in species richness Thórhallsdóttir (1990b) 0.0078 Transect of points J Law et al (1993) 0.0078 Grid of points Neighbour identities…”

Bases ecológicas para implementar un sistema de uso silvopastoral en la región patagónica de Aysén, Chile

“…Este método se ha aplicado con anterioridad en trabajos de comunidades vegetales a datos de abundancia relativa de especies para identificar el patrón de ocupación espacial y su evolución temporal (Pineda et al 1981, de Pablo et al 1982) pero hasta ahora no se había usado sobre los valores de una única variable.…”

“…Las especies con nicho espacial generalista están uniformemente distribuidas, su abundancia es homogénea en el territorio, y las de nicho especialista están restringidas a determinadas localizaciones. La amplitud de nicho puede variar con la escala (de Pablo et al 1982) y esta variación informa del hábito y preferencias ambientales de las especies. Por ejemplo, una especie puede ser generalista a escala de mucho detalle y mostrar mayor especificidad a escala de menor detalle.…”

Abandono agropastoril y recolonización vegetal : el papel de las especies leñosas como indicadoras del estadio de regeneración vegetal y de la edad de abandono (Haut Couserans-Pirineo Central francés)

“…La datación de los campos abandonados, a pesar de alguno's intentos realizados (GAUSSEN y DURRIEU, 1971;CENCI, 1976;KING, 1981;DE PABLO et al, 1982;PEREZ-CHACON y V ABRE, 1987) aparece como un problema pendiente.…”