Carbon Dioxide Emission from Streams and Rivers as an Integrative Part of Terrestrial Respiration

Shaoda Liu

doi:10.19080/ijesnr.2019.19.556010

Abstract

Streams and rivers emit significant CO2 to the atmosphere and are ecologically heterotrophic receiving carbon inputs from the terrestrial ecosystem. Despite close coupling between two ecosystems, CO2 emission from streams and rivers has never been integrated or compared to other terrestrial carbon fluxes. Here a framework integrating stream and river CO2 emission to terrestrial carbon fluxes was proposed for a better perspective of the role of streams and rivers in global carbon cycle. Using terrestrial net primary product (NPP) as the base for comparison, it is found that streams and rivers emitted more carbon than expected from their areal extent on the landscape. This elevated role of streams and rivers in releasing terrestrial carbon to the atmosphere is believed to result from a disproportional transfer of terrestrial carbon (both organic and gaseous) to the inland waters. Correlations between riverine carbon emissions and areal extent of the flowing waters suggest a hydrology-driven mediation of terrestrial carbon release by streams and rivers.

Highlights

Streams and rivers emit significant CO2 to the atmosphere and are ecologically heterotrophic receiving carbon inputs from the terrestrial ecosystem
From the point of view of a coupled biogeochemical cycle, net heterotrophy and excess CO2 emission from inland waters represent a part of the terrestrial respiration that is no more distinguishable from the rest of terrestrial carbon fluxes [5,6,7,8,9,10,11,12]
While a few studies propose to link the aquatic CO2 emission to terrestrial carbon fluxes [11,13,14], no systematic comparison has been made between the magnitude of aquatic CO2 emission and terrestrial carbon fluxes from the perspective of a combined biogeochemical cycle of carbon on land and in inland waters

Summary

Introduction

Streams and rivers emit significant CO2 to the atmosphere and are ecologically heterotrophic receiving carbon inputs from the terrestrial ecosystem. Importance of carbon emission from the rivers with respect to the terrestrial carbon fluxes was further assessed using an elevation ratio (ER) defined as the ratio of riverine carbon emission to regional NPP, divided by the ratio of the areal extent of the river network to total land area of the study region/catchment (see footnote of Table 1).

Results

Conclusion