Carbon dioxide emissions from dry watercourses

Abstract

Temporary watercourses that naturally cease to flow and run dry comprise a notable fraction of the world's river networks, yet estimates of global carbon dioxide (CO 2 ) emissions from watercourses do not consider emissions from these systems when they are dry. Using data from a sampling campaign in a Mediterranean river during the summer drought period, we demonstrate that the CO 2 efflux from dry watercourses can be substantial, comparable to that from adjacent terrestrial soils and higher than from running or stagnant waters. With an up-scaling approach, we show that including emissions from dry watercourses could increase the estimate of CO 2 emissions from watercourses in our study region by 0.6-15%. Moreover, our results tentatively illustrate that emissions from dry watercourses could be especially important in arid regions, increasing the estimate of global CO 2 emissions from watercourses by 0.4-9%. Albeit relatively small, the contribution of dry watercourses could help to constrain the highly uncertain magnitude of the land carbon sink. We foresee that in many areas of the world, the expected increase in the extent of temporary watercourses associated with future global change will increase the relevance of CO 2 emissions from dry watercourses.

Role of ephemeral vegetation of emerging river bottoms in modulating CO2 exchanges across a temperate large lowland river stretch

“…On the contrary, in the absence of ephemeral vegetation, an increase in C release by dry watercourses is expected. This is in agreement with the data collected by Gallo et al (2014) and von Schiller et al (2014) who recorded summer release rates of CO 2 up to 371 mmol m -2 day -1 . Under the Mediterranean climate, the dry riverbeds should be considered active sites in terms of C emissions, with rates comparable to those from running waters (Gómez-Gener et al 2015).…”

“…In such a context, the contribution brought by periodically exposed saturated sediments (i.e. parafluvial zones) to the C metabolism and in particular the role of ephemeral vegetation as CO 2 traps, remains scarcely known (Gallo et al 2014;von Schiller et al 2014;Gómez-Gener et al 2015;Vidon et al 2016). Large subsurface flows in permeable river sediments may favour microbial conversion of dissolved organic C (DOC) into CO 2 , resulting in interstitial water supersaturation and large fluxes to the atmosphere.…”

Stream Biofilm Responses to Flow Intermittency: From Cells to Ecosystems

“…A further expression of the high mineralization activity is that dry stream beds may become net exporters of CO 2 as occurs in dry soils do (von Schiller et al, 2014). These processes revert on the return of flow to the stream.…”

Biogeochemical contrast between different latitudes and the effect of human activity on spatio-temporal carbon cycle change in Asian river systems

“…The difference in the flux becomes larger in downstream region, and 5 this difference is more predominant in the stream channel than in the hillslope. The simulated result implies the effect of river network data on carbon cycle variability, which is also related to the importance of dry watercourses, intermittent rivers, and temporary waterways (von Schiller et al, 2014). The other research also indicates the importance of dry rivers that they constitute more than 30 % of the total length and discharge of the global river network (Datry et al, 2014), and that 69 % of first-order streams below 60° latitude flow only intermittently (Raymond et al, 2013).…”