Abstract
Riverine dissolved organic carbon (DOC), responsible for riverine productivity, is rarely documented in subtropical small mountainous rivers (SMRs) where high rainfall and steep slopes are the main features. This study investigated the DOC export at eight sites in three Taiwan SMRs to characterize the dynamics and controlling factors of DOC transport. Results showed that the mean DOC concentration of ~0.78 mg L−1 is much lower than the global average of ~5.29 mg L−1. However, the mean DOC yield, ~22.51 kg-C ha−1 yr−1, is higher than the global average of 14.4–19.3 kg-C ha−1 yr−1. Comparing with worldwide rivers from literature, the annual discharge, slope, and SOC (soil organic carbon) are controlling factors as expected, though they influence in different ways. SOC stock likely regulated by elevation-dependent biomes dominate the DOC supply, while slope restrains the DOC generation due to shallow soil depth and fast runoff velocity. However, the abundant discharge flushing this persistent low supply leads to a large DOC export in the SMRs. Furthermore, the DOC dynamics during typhoon periods showed a clockwise hysteresis, suggesting that the DOC is mainly from the riparian zone or downslope area during the rising limb of the hydrograph. This study elucidates the DOC transport in SMRs and provides an atypical yet significant piece of understanding on DOC transport in a global context.
Highlights
Of Studied small mountainous rivers (SMRs)Taiwan has a unique locality at the juncture between the Philippine and Eurasian tectonic plates and in the corridor of tropical cyclones[18,22]
Our observations show that the annual mean dissolved organic carbon (DOC) concentration at the eight sites is ~0.78 mg L−1, which is much lower than the global average of 5.29 mg L−1
The DOC yields with an average of 22.51 kg-C ha−1 yr−1, is higher than the global average of 14.4–19.3 kg-C ha−1 yr−1
Summary
Taiwan has a unique locality at the juncture between the Philippine and Eurasian tectonic plates and in the corridor of tropical cyclones[18,22]. The first river is Chi-Chia-Wan River, the renowned sole habitat for the endangered landlocked salmon, Oncorhynchus masou formosanus[22] In this river, three sampling sites were selected at C1, C2, and C3 due to different land use configurations. Two sampling sites at L1 and L2 were set to represent the entire Li-Wu River and the main tributary. The last river is Bei-Shi River whose sampling sites were set at B1, B2, and B3 tributaries. These three tributaries confluence in Pin-Lin and flow into Fei-Tsui Reservoir, which is the main domestic water supply for Taipei metropolis[23,24]. The detailed hydroclimatic metrics, landscape setting, sampling scheme, and the method of DOC measurement were described in the supplementary material
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
