Productivity of aboveground coarse wood biomass and stand age related to soil hydrology of Amazonian forests in the Purus-Madeira interfluvial area

Abstract

The ongoing demand for information on forest productivity has increased the number of permanent monitoring plots across the Amazon. Those plots, however, do not comprise the whole diversity of forest types in the Amazon. The complex effects of soil, climate and hydrology on the productivity of seasonally waterlogged interfluvial wetland forests are still poorly understood. The presented study is the first field-based estimate for tree ages and wood biomass productivity in the vast interfluvial region between the Purus and Madeira rivers. We estimate stand age and wood biomass productivity by a combination of tree-ring data and allometric equations for biomass stocks of eight plots distributed along 600 km in the Purus-Madeira interfluvial area that is crossed by the BR-319 highway. We relate stand age and wood biomass productivity to hydrological and edaphic conditions. Mean productivity and stand age were 5.6 ± 1.1 Mg ha⁻¹ yr⁻¹ and 102 ± 18 yr, respectively. There is a strong relationship between tree age and diameter, as well as between mean diameter increment and mean wood density within a plot. Regarding the soil hydromorphic properties we find a positive correlation with wood biomass productivity and a negative relationship with stand age. Productivity also shows a positive correlation with the superficial phosphorus concentration. In addition, superficial phosphorus concentration increases with enhanced soil hydromorphic condition. We raise three hypotheses to explain these results: (1) the reduction of iron molecules on the saturated soils with plinthite layers close to the surface releases available phosphorous for the plants; (2) the poor structure of the saturated soils creates an environmental filter selecting tree species of faster growth rates and shorter life spans and (3) plant growth on saturated soil is favored during the dry season, since there should be low restrictions for soil water availability

Tree growth periodicity in the ever‐wet tropical forest of the Americas

“…In some species, tree-ring formation may be genetically determined and expressed independently of environmental seasonality (Baker et al, 2017) where our study individuals occur. This idea is supported by reports of annual tree-ring in six of our tree species growing under contrasting environmental conditions: C. racemosa, A. macropetala and C. elastica have been reported in tropical seasonal forests (Brienen et al, 2009;Cintra et al, 2013;Soliz-Gamboa et al, 2011);…”

“…Adaptations of tree growth seasonality may have arisen in distinct environments, different from the Chocó region where our study individuals occur. This idea is supported by reports of annual tree‐ring in six of our tree species growing under contrasting environmental conditions: C. racemosa , A. macropetala and C. elastica have been reported in tropical seasonal forests (Brienen et al, 2009; Cintra et al, 2013; Soliz‐Gamboa et al, 2011); H. brasiliensis , S. globulifera and G. glabra were reported in seasonal moist or flooded forests (Callado et al, 2001; Lotfiomran & Köhl, 2017; Ohashi et al, 2001; Oliveira et al, 2014). Also, G. glabra and Q. lineata are widely distributed across the water availability gradient (Figure S5).…”

Dendroecology of Macrolobium acaciifolium (Fabaceae) in Central Amazonian floodplain forests

“…Additionally, the cambium enters dormancy, resulting in the formation of annual rings (Worbes 1985;Schöngart et al 2002). Dendrochronology in tropical forests and its applications to dendroecology have been used to determine age, growth rates, criteria for forest management Schöngart 2010;Rosa et al 2016), carbon sequestration in woody biomass (Schöngart et al 2011;Cintra et al 2013;Batista 2015), tree mortality in response to hydrographic changes caused by a river dam (Assahira et al 2017), and dendroclimatology (Schweingruber 1996).…”