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Remotely sensed canopy height reveals three pantropical ecosystem states: a comment
Author(s) -
Synodinos Alexis D.,
Eldridge David,
Geißler Katja,
Jeltsch Florian,
Lohmann Dirk,
Midgley Guy,
Blaum Niels
Publication year - 2018
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.1997
Subject(s) - pantropical , ecology , geography , conservation biology , biodiversity , biology , genus
Xu et al. (2016) recently demonstrated the existence of three ecosystem states in the tropics: forest, savanna and 'treeless'. Using remotely sensed tree cover and canopy height measurements, they conclude that 1) savannas and forest represent alternative states due to their climatic overlap in moist conditions (1,500-2,000 mm mean annual precipitation (MAP)), and 2) that 'treeless' and savanna ecosystems do not occur in the same MAP range, and that an abrupt shift from one ecosystem state to the other occurs at 600 mm MAP. While the first conclusion accords with existing studies (Hirota et al. 2011, Staver et al. 2011, Ratajczak and Nippert 2012), the second one contradicts our own observations from Africa and Australia as well as empirical data from published studies (February et al. 2007, Ward et al. 2013, Dohn et al. 2017), all of which indicate that savanna ecosystems certainly do occur within this dry rainfall range (<600 mm) and thus constitute an alternative ecosystem state to the 'treeless' one. This article is protected by copyright. All rights reserved.