Interaction among controlling factors on riverine din export in small mountainous rivers of taiwan: Inseparable human-landscape system
Journal
Water (Switzerland)
Journal Volume
12
Journal Issue
11
Pages
1-20
Date Issued
2020
Author(s)
Wen-Shiuan Lee et al.
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. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Subjects
Dissolved inorganic nitrogen (DIN); Partial redundancy analysis (pRDA); Redundancy analysis (RDA); Small mountainous rivers (SMRs); Taiwan
Other Subjects
Aquatic ecosystems; Drought; Nitrogen; Quality management; Water conservation; Water management; Water quality; Watersheds; Controlling factors; Dissolved inorganic nitrogens; Environmental variables; Interactive control; Mitigation strategy; Positive correlations; Redundancy analysis; Small mountainous rivers; Quality control; ammonium; dry season; landscape change; mountain region; nitrogen; river flow; seasonality; water quality; watershed; wet season; Taiwan
Type
journal article