@article{fdi:010083927,
  title = {{P}artitioning carbon sources between wetland and well-drained ecosystems to a tropical first-order stream - implications for carbon cycling at the watershed scale ({N}yong, {C}ameroon)},
  author = {{M}oustapha, {M}. and {D}eirmendjian, {L}oris and {S}ebag, {D}avid and {B}raun, {J}ean-{J}acques and {A}udry, {S}. and {B}essa, {H}. {A}. and {A}datte, {T}. and {C}ausserand, {C}. and {A}damou, {I}. and {N}gatcha, {B}. {N}. and {G}u{\'e}rin, {F}r{\'e}d{\'e}ric},
  editor = {},
  language = {{ENG}},
  abstract = {{T}ropical rivers emit large amounts of carbon dioxide ({CO}2) to the atmosphere, in particular due to large wetland-to-river carbon ({C}) inputs. {Y}et, tropical {A}frican rivers remain largely understudied, and little is known about the partitioning of {C} sources between wetland and well-drained ecosystems to rivers. {I}n a first-order sub-catchment (0.6 km(2)) of the {N}yong watershed ({C}ameroon 27 800 km(2)), we fortnightly measured {C} in all forms and ancillary parameters in groundwater in a well-drained forest (hereafter referred to as non-flooded forest groundwater) and in the stream. {I}n the first-order catchment, the simple land use shared between wetland and well-drained forest, together with drainage data, allowed the partitioning of {C} sources between wetland and well-drained ecosystems to the stream. {A}lso, we fortnightly measured dissolved and particulate {C} downstream of the first-order stream to the main stem of order 6, and we supplemented {C} measurements with measures of heterotrophic respiration in stream orders 1 and 5. {I}n the first-order stream, dissolved organic and inorganic {C} and particulate organic {C} ({POC}) concentrations increased during rainy seasons when the hydrological connectivity with the riparian wetland increased, whereas the concentrations of the same parameters decreased during dry seasons when the wetland was shrinking. {I}n larger streams (order > 1), the same seasonality was observed, showing that wetlands in headwaters were significant sources of organic and inorganic {C} for downstream rivers, even though higher {POC} concentration evidenced an additional source of {POC} in larger streams during rainy seasons that was most likely {POC} originating from floating macrophytes. {D}uring rainy seasons, the seasonal flush of organic matter from the wetland in the first-order catchment and from the macrophytes in higher-order rivers significantly affected downstream metabolism, as evidenced by higher respiration rates in stream order 5 (756 +/- 333 g{C}-{CO}2 m(-2) yr(-1)) compared to stream 1 (286 +/- 228 g{C}-{CO}2 m(-2) yr(-1)). {I}n the first-order catchment, the sum of the {C} hydrologically exported from non-flooded forest groundwater (6.2 +/- 3.0 {M}g{C} yr-1) and wetland (4.0 +/- 1.5 {M}g{C} yr(-1)) to the stream represented 3 %-5 % of the local catchment net {C} sink. {I}n the first-order catchment, non-flooded forest groundwater exported 1.6 times more {C} than wetland; however, when weighed by surface area, {C} inputs from non-flooded forest groundwater and wetland to the stream contributed to 27 % (13.0 +/- 6.2 {M}g{C} yr(-1)) and 73 % (33.0 +/- 12.4 {M}g{C} yr(-1)) of the total hydrological {C} inputs, respectively. {A}t the {N}yong watershed scale, the yearly integrated {CO}2 degassing from the entire river network was 652 +/- 161 {G}g{C}-{CO}2 yr(-1) (23.4 +/- 5.8 {M}g{C} {CO}2 km(-2) yr(-1) when weighed by the {N}yong watershed surface area), whereas average heterotrophic respiration in the river and {CO}2 degassing rates was 521 +/- 403 and 5085 +/- 2544 g{C}-{CO}2 m(-2) yr(-1), which implied that only similar to 10 % of the {CO}2 degassing at the water-air interface was supported by heterotrophic respiration in the river. {I}n addition, the total fluvial {C} export to the ocean of 191 +/- 108 {G}g{C} yr(-1) (10.3 +/- 5. 8 {M}g{C} km(-2) yr(-1) when weighed by the {N}yong watershed surface area) plus the yearly integrated {CO}2 degassing from the entire river network represented similar to 11 % of the net {C} sink estimated for the whole {N}yong watershed. {I}n tropical watersheds, we show that wetlands largely influence riverine {C} variations and budget. {T}hus, ignoring the river-wetland connectivity might lead to the misrepresentation of {C} dynamics in tropical watersheds.},
  keywords = {{CAMEROUN} ; {ZONE} {EQUATORIALE} ; {ZONE} {TROPICALE} ; {NYONG} {BASSIN} {VERSANT}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {19},
  numero = {1},
  pages = {137--163},
  ISSN = {1726-4170},
  year = {2022},
  DOI = {10.5194/bg-19-137-2022},
  URL = {https://www.documentation.ird.fr/hor/fdi:010083927},
}