Fig 1.
Permafrost distributions, locations of sampling sites and stations with precipitation data for the headwater rivers of the Tibetan Plateau.
Data of permafrost distributions were from [20]. The map was plotted by ArcGIS 10.2.1 software (ESRI®). Detailed information concerning the sampling sites is shown in Table 1.
Table 1.
Sampling information of the studied rivers.
Table 2.
Discharge (km3 yr-1), dissolved organic carbon (DOC) concentration (mg-C L-1), C/N (unitless) and DOC loads (GgC yr-1) of three rivers draining the Tibetan Plateau.
Fig 2.
Distributions of Δ14C and δ13C isotopes of dissolved organic carbon for rivers of the Tibetan Plateau and other regions.
A full reference list for the carbon isotopes data is provided in Data Set 1.
Table 3.
Concentrations, stable carbon and radiocarbon isotope values for dissolved organic carbon in Tibetan Plateau rivers.
Fig 3.
Significant relationship between permafrost soil area as a percentage of watershed area (%) and 14C age of dissolved organic carbon (DOC) in years before present.
Note: samples 3 and 15 were not included in the regression because the old DOC ages of these two samples were attributed to factors other than permafrost carbon contributions. Sample 3 was collected from the lower reaches of the large Longyangxia reservoir on the main stem of the Yellow river. The long residence time of water in the reservoir [23] or carbon age reservoir effects [50] may therefore have contributed to the old 14C age of DOC in this sample. Sample 15 was collected from Yarlung Tsangpo Grand Canyon, the region with the maximum topographic slope on the Tibetan Plateau [51].