A continental analysis of correlations between tree patterns in African savannas and human and environmental variables

This study analyses possible relationships between natural processes taking place in savannas and the tree patterns found in savannas. This can lead to new hypotheses about which processes are driving savanna physiognomy. To do so tree patterns were quantified for African savannas from historical ae...

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Bibliographic Details
Published in:Journal of arid environments Vol. 75; no. 8; pp. 724 - 733
Main Authors: Groen, T.A., van Langevelde, F., van de Vijver, C.A.D.M., de Raad, A.L., de Leeuw, J., Prins, H.H.T.
Format: Journal Article
Language:English
Published: Kidlington Elsevier Ltd 01.08.2011
Elsevier
Subjects:
Abiotic conditions
Aerial photographs
Aerials
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
coexistence
Correlation analysis
Density
density patterns
ecosystems
fire frequency
Fundamental and applied biological sciences. Psychology
Herbivory
Human
Livestock
Nearest neighbour
Precipitation
Savanna trees
semiarid savannas
southern-africa
Spatial pattern
stability
Synecology
Terrestrial ecosystems
Trees
vegetation
woodlands
woody cover
Africa
Nearest neighbour
Abiotic conditions
Precipitation
Aerial photographs
Herbivory
Spatial pattern
Savanna trees
Human
Herbivorous
Arid environment
Environmental factor
Aerial photography
Spatial variation
Spatial distribution
Savanna woodland
Tree
ISSN:0140-1963, 1095-922X
Online Access:Get full text
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Summary:This study analyses possible relationships between natural processes taking place in savannas and the tree patterns found in savannas. This can lead to new hypotheses about which processes are driving savanna physiognomy. To do so tree patterns were quantified for African savannas from historical aerial photographs applying frequently used landscape metrics. Also, additional data for these areas were collected to quantify the processes taking place at these locations. Correlations between tree pattern indices and explaining factors were analysed. We found a negative trend between tree cover and density of sheep and goats, but no relationship between tree cover and density of cattle, suggesting that small livestock have an effect on tree cover, but that larger livestock (or obligate grazers) do not. Also, a positive correlation between human population density and tree cover was found. Possible explanations for the found relations are discussed. Subsequent ways to analyse the latter correlation are discussed, and the potential of the presented historical database of aerial photographs is highlighted. ► Tree patterns in historical areal photographs were quantified. ► These patterns were correlated with processes. ► Sheep and goat density had a negative correlation with tree cover. ► Human population density had a positive correlation with tree cover.
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ISSN:0140-1963
1095-922X
DOI:10.1016/j.jaridenv.2011.03.010