亞熱帶山區河流營養鹽濃度和化學計量比對人為影響的反應

Responses of nutrient concentration and stoichiometric ratios to human disturbance in subtropical mountainous rivers

劉恩如(En-Ru Liu)

指導教授 ： 黃誌川

國立臺灣大學/理學院/地理環境資源學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202104014

摘要

水中溶解性有機碳（dissolved organic carbon, DOC）、溶解性有機氮（dissolved organic nitrogen, DON）和硝酸鹽（NO3-）濃度的耦合關係可以透過被動碳載體假說、DON釋放假說及間接碳控制假說來描述，且這些假說各自有不同的適用情境。營養鹽傳輸受到諸多因素調控，如土地利用、地景因子及逕流狀況，且可能存在著空間和時間上的變異。為了解環境特徵與生物地球化學循環之間的關聯，本研究監測北台灣的小型山地集水區中19個採樣點之營養鹽輸出，再依營養鹽濃度特徵做分類，符合被動碳載體假說者有13個採樣點，其餘6個採樣點則歸屬於間接碳控制假說，兩組分別運用冗餘分析（redundancy analysis, RDA）釐清營養鹽傳輸與其控制因子之關聯。
本研究區DOC的單位面積輸出量約為1.75 ton-C km-2 yr-1，而DON與NO3-則為 0.53 和1.7 ton-N km-2 yr-1。將環境參數分為土地利用、地景、水文共三組進行RDA，在DOC的部分，水文為主要控制因子；DON與NO3-的解釋變量也是由水文佔大宗，但地景與土地利用的交互作用明顯提升，尤其是在符合間接碳控制假說的集水區。本研究建議探討集水區營養鹽輸出時應考量不同因子間的交互作用，將有助於釐清集水區中營養鹽傳輸的控制因子。

關鍵字

營養鹽傳輸 ； 碳氮耦合關係 ； 生物地球化學 ； 土地利用 ； 冗餘分析

並列摘要

Stream water dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and nitrate (NO3-) concentration can be described by the passive carbon vehicle hypothesis, DON release hypothesis and indirect carbon control hypothesis, and each of these hypotheses has different applicable situations. Nutrient transport is controlled by many environmental factors, like land use, landscape and runoff, and spatial and temporal variation may exist. To realize the relation between environmental characteristics and biogeochemistry cycle, this study monitors the nutrient export of 19 sampling sites in the small mountainous catchment in northern Taiwan. The sampling sites are classified according to the passive carbon vehicle hypothesis (13 sampling sites) and the indirect carbon control hypothesis (6 sampling sites), and redundancy analysis (RDA) is used to clarify the relationship between nutrient transport and its controlling factors.
Results show the average annual DOC yields of the 19 catchments is around 1.75 ton-C km-2 yr-1, while DON and NO3- yield are around 0.53 and 1.7 ton-N km-2 yr-1. We divide the characteristics into three groups, namely, land use, landscape and hydrology for RDA. In the DOC yield, hydrology is main controlling factor. The explanatory variables of DON and NO3- are also dominated by hydrology, but the interaction between landscape and land use has largely increased, especially the sites in the indirect carbon control hypothesis set. Our study suggests that interpretation of spatial variation in nutrient export should address the overlap of characteristics, which helps to understand controlling factors of nutrient transport more accurately.

並列關鍵字

nutrient transport ； carbon-nitrogen coupling ； biogeochemistry ； land use ； redundancy analysis

參考文獻

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