TY - JOUR
T1 - Not only trees
T2 - Grasses determine African tropical biome distributions via water limitation and fire
AU - D'Onofrio, Donatella
AU - von Hardenberg, Jost
AU - Baudena, Mara
PY - 2018/6
Y1 - 2018/6
N2 - Aim: Although much tropical ecology generally focuses on trees, grasses are fundamental for characterizing the extensive tropical grassy biomes (TGBs) and, together with the tree functional types, for determining the contrasting functional patterns of TGBs and tropical forests (TFs). To study the factors that determine African biome distribution and the transitions between them, we performed the first continental analysis to include grass and tree functional types. Location: Sub-Saharan Africa. Time period: 2000-2010. Major taxa studied: Savanna and forest trees and C4 grasses. Methods: We combined remote-sensing data with a land cover map, using tree functional types to identify TGBs and TFs. We analysed the relationships of grass and tree cover with fire interval, rainfall annual average and seasonality. Results: In TGBs experiencing < 630 mm annual rainfall, grass growth was water limited. Grass cover and fire recurrence were strongly and directly related over the entire subcontinent. Some TGBs and TFs with annual rainfall > 1,200 mm had the same rainfall seasonality but displayed strongly different fire regimes. Main conclusions: Water limitation to grass growth was fundamental in the driest TGBs, acting alongside the well-known limitation to tree growth. Marked differences in fire regimes across all biomes indicated that fire was especially relevant for maintaining mesic and humid TGBs. At high rainfall, our results support the hypothesis of TGBs and TFs being alternative stable states maintained by a vegetation-fire feedback for similar climatic conditions.
AB - Aim: Although much tropical ecology generally focuses on trees, grasses are fundamental for characterizing the extensive tropical grassy biomes (TGBs) and, together with the tree functional types, for determining the contrasting functional patterns of TGBs and tropical forests (TFs). To study the factors that determine African biome distribution and the transitions between them, we performed the first continental analysis to include grass and tree functional types. Location: Sub-Saharan Africa. Time period: 2000-2010. Major taxa studied: Savanna and forest trees and C4 grasses. Methods: We combined remote-sensing data with a land cover map, using tree functional types to identify TGBs and TFs. We analysed the relationships of grass and tree cover with fire interval, rainfall annual average and seasonality. Results: In TGBs experiencing < 630 mm annual rainfall, grass growth was water limited. Grass cover and fire recurrence were strongly and directly related over the entire subcontinent. Some TGBs and TFs with annual rainfall > 1,200 mm had the same rainfall seasonality but displayed strongly different fire regimes. Main conclusions: Water limitation to grass growth was fundamental in the driest TGBs, acting alongside the well-known limitation to tree growth. Marked differences in fire regimes across all biomes indicated that fire was especially relevant for maintaining mesic and humid TGBs. At high rainfall, our results support the hypothesis of TGBs and TFs being alternative stable states maintained by a vegetation-fire feedback for similar climatic conditions.
KW - African vegetation
KW - Alternative stable states
KW - Fire
KW - Grass cover
KW - Mean annual rainfall
KW - Rainfall seasonality
KW - Savanna
KW - Tree functional type
KW - Tropical forest
KW - Tropical grassy biomes
UR - http://www.scopus.com/inward/record.url?scp=85045375537&partnerID=8YFLogxK
U2 - 10.1111/geb.12735
DO - 10.1111/geb.12735
M3 - Article
AN - SCOPUS:85045375537
SN - 1466-822X
VL - 27
SP - 714
EP - 725
JO - Global Ecology and Biogeography
JF - Global Ecology and Biogeography
IS - 6
ER -