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Abstract
Background: The zone of transition (ZOT) between the Cerrado and the Amazon forest in southern Amazonia represents a unique and rapidly shrinking area due to land-use change.
Aims: To compare the dynamics and above-ground biomass of vegetation located in the ZOT with core Amazon forest and to determine how ZOT dynamics differ within vegetation types for different tree diameter classes.
Methods: Censuses of trees were conducted in seven plots in monodominant forest, semi-deciduous seasonal forest, gallery forest, cerrado sensu stricto and cerradão, in north-eastern Mato Grosso, Brazil from 1996 to 2010, including data for the 2005 drought year. Separate analyses of stem dynamics and biomass were carried out for two different diameter (d) classes: 5 ≤ d < 10 cm and d ≥ 10 cm.
Results: For trees with d ≥ 10 cm the average mortality rate was 2.8% year−1, with an estimated above-ground dry biomass of 210 Mg ha−1. Trees with 5 ≤ d < 10 cm constituted only a small fraction of the total biomass store (ca. 10 Mg ha−1) and had a mortality rate of 7.4% year−1 and recruitment of 6.5% year−1. Overall, mortality and recruitment in the ZOT were greater than in core Amazonian forests (1–2% year−1).
Conclusions: The distinct vegetation formations of the southern Amazon ZOT are markedly more dynamic than core Amazonian forest. Continued long-term monitoring throughout the region is required to assess whether they also respond differently to climate change.
Acknowledgements
This study was partially supported by a grant from the NERC through the RAINFOR network and partially supported by a grant from the Brazilian National Council for Scientific and Technological Development (CNPq)/Long Term Ecological Research (PELD) project (Proc. 558069/2009-6) and Mato Grosso State Support Research Foundation (FAPEMAT, Nr. 217.088/2011). BS Marimon acknowledges CNPq for financial support for her post-doctorate study (Proc. 201914/2012-3) during which time part of this manuscript was developed. OP is supported by an ERC Advanced Grant “Tropical Forests in the Changing Earth System” and by a Royal Society Wolfson Research Merit Award. COS, HAM, EAO, LM and AM were supported by CAPES studentships. We thank the staff of the ‘Laboratório de Ecologia Vegetal’, Campus de Nova Xavantina, UNEMAT, and Mr. Jairo R. Machado for logistical help and support. The manuscript was developed with help from the NERC project AMAZONICA and the Gordon and Betty Moore Foundation in their 2008–2012 grant to the RAINFOR project. We gratefully appreciate the critical comments and suggestions by the anonymous referees.