Edaphic controls on ecosystem-level carbon allocation in two contrasting Amazon forests

Abstract

Studies of carbon allocation in forests provide essential information for understanding spatial and temporal differences in carbon cycling that can inform models and predict possible responses to changes in climate. Amazon forests play a particularly significant role in the global carbon balance, but there are still large uncertainties regarding abiotic controls on the rates of net primary production (NPP) and the allocation of photosynthetic products to different ecosystem components. We evaluated three different aspects of stand-level carbon allocation (biomass, NPP, and its partitioning) in two amazon forests on different soils (nutrient-rich clay soils versus nutrient-poor sandy soils) but otherwise growing under similar conditions. We found differences in carbon allocation patterns between these two forests, showing that the forest on clay soil had a higher aboveground and total biomass as well as a higher aboveground NPP than the sandy forest. However, differences between the two forest types in terms of total NPP were smaller, as a consequence of different patterns in the carbon allocation of aboveground and belowground components. The proportional allocation of NPP to new foliage was relatively similar between them. Our results of aboveground biomass increments and fine-root production suggest a possible trade-off between carbon allocation to fine roots versus aboveground compartments, as opposed to the most commonly assumed trade-off between total aboveground and belowground production. Despite these differences among forests in terms of carbon allocation, the leaf area index showed only small differences, suggesting that this index is more indicative of total NPP than its aboveground or belowground components.

Net Primary Productivity and Edaphic Fertility in Two Pluvial Tropical Forests in the Chocó Biogeographical Region of Colombia

“…In summary, this study supports the hypothesis that at the landscape scale, soils control a trade-off between carbon allocation to fine roots versus aboveground biomass increment [56], which could explain the similitude of NPP among sites with different environmental conditions; its detailed examination is an important area of research in order to deepen our understanding of factors governing NPP across the globe.…”

“…Likewise, important edaphic controls on carbon allocation of two Amazon forests under similar climatic conditions on contrasting soils (clayey versus sandy soils) has been reported [56]. In particular, they found that NPP, fine litterfall and the increment of aboveground biomass were higher in the clayey soil forest; while, fine-root production was higher in the white-sand forest.…”

White‐sand Ecosystems in Amazonia

“…, Jiménez et al . ). In some cases, pH values, which vary between 3.5 and 5 (Anderson , Coomes , Quesada et al .…”

Spatial and temporal variation of forest net primary productivity components on contrasting soils in northwestern Amazon

“…We assessed intra‐annual variation or seasonality among plots of above and belowground NPP components by making detailed measurements of fine litterfall, stem growth, fine‐root mass, and leaf area index (LAI), with methods described in Jiménez et al (2014). Fine litterfall (leaves, flowers, fruits, and twigs with diameter ≤2 mm and indeterminate material for 2004–2006) was collected bi‐weekly, from 25 mesh traps (0.5 m 2 ) per plot.…”