Interaction among controlling factors on riverine din export in small mountainous rivers of taiwan: Inseparable human-landscape system

Wen Shiuan Lee, Jr Chuan Huang, Chung Te Chang, Shih Chien Chan, Ying San Liou, Chien Sen Liao, Li Chin Lee, Jun Yi Lee, Yu Ting Shih, Meng Chang Lu, Pei Hao Chen

Research output: Contribution to journalArticlepeer-review

Abstract

Increasing anthropogenic nitrogen (N) emission via different pathways has shown prominent impact on aquatic ecosystems for decades, but the effects of interaction among climate-, landscape-and human-associated variables on riverine DIN (dissolved inorganic nitrogen, mainly NO3 and NH4+) export are unclear. In this study, the data of 43 watersheds with a wide range of climate-, landscape-and human-associated gradients across Taiwan were evaluated with partial redundancy analysis (pRDA) to examine their interactive controls on riverine DIN export. Results show that the annual riverine DIN export in Taiwan is approximately 3100 kg-N km−2 yr−1, spanning from 230 kg-N km−2 yr−1 in less disturbed watersheds (eastern and central Taiwan) to 10,000 kg-N km−2 yr−1 in watersheds with intensive human intervention (southwestern and northern Taiwan). NO3 is generally the single dominant form of DIN, while NH4+ renders significance in disturbed watersheds. Nearly all environmental variables display a positive correlation with DIN export, except for landscape setting variables (e.g., slope, area, channel length), which show a negative relationship. In terms of seasonal pattern, climate and human-landscape variables are related to NO3 export independently in the wet season, yet in the dry season climate-human variables jointly dominate NO3 export. Meanwhile, human-landscape (LH) variables (λ1 of LH > 0.60) control NH4+ exports in both seasons, and human-associated (H) variables (λ1 of H = 0.13) have a minor effect on NH4+ exports in dry season. Precisely, the contribution of controlling variables on DIN export vary with species and seasons, indicating water quality management could be time-dependent, which should be taken into consideration for designing mitigation strategies.

Original languageEnglish
Article number2981
Pages (from-to)1-20
Number of pages20
JournalWater (Switzerland)
Volume12
Issue number11
DOIs
Publication statusPublished - 2020 Nov

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Geography, Planning and Development
  • Aquatic Science
  • Water Science and Technology

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