Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes

Abstract

We constructed a whole carbon budget for a catchment in the Western Amazon Basin, combining drainage water analyses with eddy covariance (EC) measured terrestrial CO2 fluxes. As fluvial C export can represent permanent C export it must be included in assessments of whole site C balance, but it is rarely done. The footprint area of the flux tower is drained by two small streams (~5–7 km2) from which we measured the dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC) export, and CO2 efflux. The EC measurements showed the site C balance to be +0.7 ± 9.7 Mg C ha−1 yr−1 (a source to the atmosphere) and fluvial export was 0.3 ± 0.04 Mg C ha−1 yr−1. Of the total fluvial loss 34% was DIC, 37% DOC, and 29% POC. The wet season was most important for fluvial C export. There was a large uncertainty associated with the EC results and with previous biomass plot studies (−0.5 ± 4.1 Mg C ha−1 yr−1); hence, it cannot be concluded with certainty whether the site is C sink or source. The fluvial export corresponds to only 3–7% of the uncertainty related to the site C balance; thus, other factors need to be considered to reduce the uncertainty and refine the estimated C balance. However, stream C export is significant, especially for almost neutral sites where fluvial loss may determine the direction of the site C balance. The fate of C downstream then dictates the overall climate impact of fluvial export.

Erosion of organic carbon from the Andes and its effects on ecosystem carbon dioxide balance

“…Erosion and river transport of POC biosphere represents export of carbon from forest ecosystems [Hilton et al, 2012;Ciais et al, 2014;Galy et al, 2015]. This component of ecosystem carbon budgets is not often considered at the forest plot scale [Iwata et al, 2005;Ciais et al, 2014;Vihermaa et al, 2016]. In the Kosñipata River valley, the net primary production of forests (NPP-the carbon equivalent of above and belowground biomass production) is~1000 t C km À2 yr À1 [Malhi et al, 2016].…”

Peer Review #1 of "Importance of active layer freeze-thaw cycles on the riverine dissolved carbon export on the Qinghai-Tibet Plateau permafrost region (v0.1)"

“…Also, the large proportion of subsurface interflow, which is averagely 25.2% of total runoff (Wang et al, 2009), could Manuscript to be reviewed possibly introduce much soil carbon into the river channels. The dissolved carbon concentrations were higher than non-permafrost rivers (Ran et al, 2013;Vihermaa et al, 2016). The relatively high total dissolved carbon concentrations at our site indicated that the active layer in such highelevation permafrost is a hotspot for promoting dissolved carbon loss.…”

“…These response of hydrological changes to permafrost degradation are also expected to change the patterns of riverine carbon export (Frey and McClelland, 2009), which is not only a major component of carbon cycle (Cole et al, 2007), but also an indicator of the responses of adjacent terrestrial ecosystems to environmental change (Spencer et al, 2015). Riverine carbon export is closely coupled with watershed hydrology (Hartmann, 2009;McClelland et al, 2016;Raymond and Oh, 2007;Vihermaa et al, 2016).…”

Toward Landsat and Sentinel-2 BRDF Normalization and Albedo Estimation: A Case Study in the Peruvian Amazon Forest

“…At the station, a Campbell Scientific NR01 4-component net radiometer installed on a 44-meter tower does continuous measurements of upward and downward shortwave radiation over the canopy and the 10-min average value is recorded. More details of the validation station and instruments can be found in Vihermaa et al (2016). Data was acquired during the time period studied (2013-2017).…”