Water availability is a principal driver of large-scale land cover spatial heterogeneity in sub-Saharan savannahs

Christopher Marston, David M. Wilkinson, Sally C. Reynolds, Julien Louys, Hannah J. O'Regan

Research output: Contribution to journalArticle

7 Downloads (Pure)

Abstract

Context The heterogeneous mosaic nature of African savannah vegetation is a key aspect of its ecology. This study evaluates mosaic distributions and characteristics across sub-Saharan Africa, investigating the environmental drivers of mosaic formation. Objectives This study was designed to determine: (1) on a continental scale, how frequent are mosaics in savannahs? and (2) what are the key environmental drivers in the formation of mosaics? Methods Landsat ETM? satellite imagery was used to generate land-cover maps for 39 sample areas across sub-Saharan Africa. The spatial complexity of land-cover mosaics at 4628 savannah sub-sites was quantified, and modelled using random forests to identify the relative importance of environmental variables driving mosaic presence. Results Only six sub-sites constituted a single landcover class, illustrating that mosaic habitats are abundant at the scale analysed (19.6 km2), although mosaic characteristics varied considerably. Results indicate precipitation is most important in influencing mosaic complexity, followed by evapotranspiration, temperature, lithology and distance to rivers. Fire and ecosystem engineer presence are of lesser importance at this study scale. Conclusions Mosaics are ubiquitous in the African savannahs studied, their presence influenced by multiple environmental drivers, with water being key. The lower importance of fire and large mammal disturbance is likely resulting from these highly individualistic site-based process varying between sites, resulting in no single, coherent, across-Africa disturbance signal, and/or lack of detail in available data at this scale. Therefore, large-scale determinants of savannah mosaics appear climate-driven. Under future global warming scenarios, African savannahs are likely to become more homogenous.
Original languageEnglish
JournalLandscape Ecology
Early online date29 Nov 2018
DOIs
Publication statusE-pub ahead of print - 29 Nov 2018

Fingerprint

water availability
land cover
driver
water
habitat
ecology
engineer
river
climate
determinants
scenario
lack
mosaic
habitat mosaic
disturbance
satellite imagery
Landsat
evapotranspiration
global warming
lithology

Keywords

  • Heterogeneity
  • Land cover
  • Landsat
  • Remote sensing
  • Savannah
  • Sub-Saharan Africa

Cite this

Marston, Christopher ; Wilkinson, David M. ; Reynolds, Sally C. ; Louys, Julien ; O'Regan, Hannah J. / Water availability is a principal driver of large-scale land cover spatial heterogeneity in sub-Saharan savannahs. In: Landscape Ecology. 2018.
@article{f9c5c874c07149d18374f8c7a9ca5d05,
title = "Water availability is a principal driver of large-scale land cover spatial heterogeneity in sub-Saharan savannahs",
abstract = "Context The heterogeneous mosaic nature of African savannah vegetation is a key aspect of its ecology. This study evaluates mosaic distributions and characteristics across sub-Saharan Africa, investigating the environmental drivers of mosaic formation. Objectives This study was designed to determine: (1) on a continental scale, how frequent are mosaics in savannahs? and (2) what are the key environmental drivers in the formation of mosaics? Methods Landsat ETM? satellite imagery was used to generate land-cover maps for 39 sample areas across sub-Saharan Africa. The spatial complexity of land-cover mosaics at 4628 savannah sub-sites was quantified, and modelled using random forests to identify the relative importance of environmental variables driving mosaic presence. Results Only six sub-sites constituted a single landcover class, illustrating that mosaic habitats are abundant at the scale analysed (19.6 km2), although mosaic characteristics varied considerably. Results indicate precipitation is most important in influencing mosaic complexity, followed by evapotranspiration, temperature, lithology and distance to rivers. Fire and ecosystem engineer presence are of lesser importance at this study scale. Conclusions Mosaics are ubiquitous in the African savannahs studied, their presence influenced by multiple environmental drivers, with water being key. The lower importance of fire and large mammal disturbance is likely resulting from these highly individualistic site-based process varying between sites, resulting in no single, coherent, across-Africa disturbance signal, and/or lack of detail in available data at this scale. Therefore, large-scale determinants of savannah mosaics appear climate-driven. Under future global warming scenarios, African savannahs are likely to become more homogenous.",
keywords = "Heterogeneity, Land cover, Landsat, Remote sensing, Savannah, Sub-Saharan Africa",
author = "Christopher Marston and Wilkinson, {David M.} and Reynolds, {Sally C.} and Julien Louys and O'Regan, {Hannah J.}",
year = "2018",
month = "11",
day = "29",
doi = "10.1007/s10980-018-0750-9",
language = "English",
journal = "Landscape Ecology",
issn = "0921-2973",
publisher = "springer",

}

Water availability is a principal driver of large-scale land cover spatial heterogeneity in sub-Saharan savannahs. / Marston, Christopher; Wilkinson, David M.; Reynolds, Sally C.; Louys, Julien; O'Regan, Hannah J.

In: Landscape Ecology, 29.11.2018.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Water availability is a principal driver of large-scale land cover spatial heterogeneity in sub-Saharan savannahs

AU - Marston, Christopher

AU - Wilkinson, David M.

AU - Reynolds, Sally C.

AU - Louys, Julien

AU - O'Regan, Hannah J.

PY - 2018/11/29

Y1 - 2018/11/29

N2 - Context The heterogeneous mosaic nature of African savannah vegetation is a key aspect of its ecology. This study evaluates mosaic distributions and characteristics across sub-Saharan Africa, investigating the environmental drivers of mosaic formation. Objectives This study was designed to determine: (1) on a continental scale, how frequent are mosaics in savannahs? and (2) what are the key environmental drivers in the formation of mosaics? Methods Landsat ETM? satellite imagery was used to generate land-cover maps for 39 sample areas across sub-Saharan Africa. The spatial complexity of land-cover mosaics at 4628 savannah sub-sites was quantified, and modelled using random forests to identify the relative importance of environmental variables driving mosaic presence. Results Only six sub-sites constituted a single landcover class, illustrating that mosaic habitats are abundant at the scale analysed (19.6 km2), although mosaic characteristics varied considerably. Results indicate precipitation is most important in influencing mosaic complexity, followed by evapotranspiration, temperature, lithology and distance to rivers. Fire and ecosystem engineer presence are of lesser importance at this study scale. Conclusions Mosaics are ubiquitous in the African savannahs studied, their presence influenced by multiple environmental drivers, with water being key. The lower importance of fire and large mammal disturbance is likely resulting from these highly individualistic site-based process varying between sites, resulting in no single, coherent, across-Africa disturbance signal, and/or lack of detail in available data at this scale. Therefore, large-scale determinants of savannah mosaics appear climate-driven. Under future global warming scenarios, African savannahs are likely to become more homogenous.

AB - Context The heterogeneous mosaic nature of African savannah vegetation is a key aspect of its ecology. This study evaluates mosaic distributions and characteristics across sub-Saharan Africa, investigating the environmental drivers of mosaic formation. Objectives This study was designed to determine: (1) on a continental scale, how frequent are mosaics in savannahs? and (2) what are the key environmental drivers in the formation of mosaics? Methods Landsat ETM? satellite imagery was used to generate land-cover maps for 39 sample areas across sub-Saharan Africa. The spatial complexity of land-cover mosaics at 4628 savannah sub-sites was quantified, and modelled using random forests to identify the relative importance of environmental variables driving mosaic presence. Results Only six sub-sites constituted a single landcover class, illustrating that mosaic habitats are abundant at the scale analysed (19.6 km2), although mosaic characteristics varied considerably. Results indicate precipitation is most important in influencing mosaic complexity, followed by evapotranspiration, temperature, lithology and distance to rivers. Fire and ecosystem engineer presence are of lesser importance at this study scale. Conclusions Mosaics are ubiquitous in the African savannahs studied, their presence influenced by multiple environmental drivers, with water being key. The lower importance of fire and large mammal disturbance is likely resulting from these highly individualistic site-based process varying between sites, resulting in no single, coherent, across-Africa disturbance signal, and/or lack of detail in available data at this scale. Therefore, large-scale determinants of savannah mosaics appear climate-driven. Under future global warming scenarios, African savannahs are likely to become more homogenous.

KW - Heterogeneity

KW - Land cover

KW - Landsat

KW - Remote sensing

KW - Savannah

KW - Sub-Saharan Africa

U2 - 10.1007/s10980-018-0750-9

DO - 10.1007/s10980-018-0750-9

M3 - Article

JO - Landscape Ecology

JF - Landscape Ecology

SN - 0921-2973

ER -