Disequilibrium and hyperdynamic tree turnover at the forest–cerrado transition zone in southern Amazonia

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.

Effects of soil and space on the woody species composition and vegetation structure of three Cerrado phytophysiognomies in the Cerrado-Amazon transition

“…The present study area is located within the region known as the "Arc of deforestation" , where anthropogenic impacts represent a major threat to the local biodiversity. As shown in other studies (Marimon et al, 2014;Marimon-Junior and Haridasan, 2005;Kunz et al, 2009;Gomes et al, 2011;Maracahipes-Santos et al, 2015), the species richness of trees and shrubs in the Cerrados of eastern Mato Grosso is among the biome's highest. Given the results of these studies, together with those of the present survey, we would recommend the consolidation of existing conservation units, and the creation of new areas that protect the distinct Cerrado phytophysiognomies found in the region of the Cerrado-Amazon transition (see Venn diagram, Maracahipes-Santos et al, 2015).…”

“…The complexity of the relationships found in the present study may also be at least partly a result of the ongoing anthropogenic impacts that affect the study region (Marimon et al, 2014), and also the fire regime (Coutinho, 2002) creating a highly dynamic scenario that affects all types of vegetation in different ways. GOMES, L., LENZA, E., MARACAHIPES, L., MARIMON, B.S.…”

Biomass hyperdynamics as a key modulator of forest self-maintenance in a dystrophic soil in the Amazonia-Cerrado transition

“…HARIDASAN, 2000). Part of this mechanism of cerradão may be related to the high growth rates, as found by Rossatto et al (2009), and also due to the hyperdynamics of the vegetation, which results in high mortality and tree recruitmet (MARIMON et al, 2014). These hyperdynamics may help in nutrient cycling by litter decomposition, keeping them in a quick cycle between vegetation and soil, and thus guaranteeing a higher nutrient flow, which is required by the cerradões, as compared to cerrados of less biomass.…”

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“…Another explanation might be related to the particular environmental and ecological conditions (relatively fertile and aseasonal environments) in the west, which may be easier to invade by multiple lineages with diverse evolutionary backgrounds. Moreover, the ability of diverse lineages to establish in the western and southern Amazon may also be related to the high rates of disturbance and turnover in the region (Quesada et al, 2012;Marimon et al, 2013;Baker et al, 2014). Thus, in the same way that more fertile, dynamic, and disturbed tropical forests have more open nutrient-cycles on ecological time-scales (Vitousek & Sanford, 1986), they also appear to be more open to repeated establishment of plant lineages on evolutionary time-scales.…”