Atmospheric deposition versus rock weathering in the control of streamwater chemistry in a tropical rain-forest catchment in Malaysian Borneo. (September 2014)

• Record Type: Journal Article
• Authors: Yamashita, Naoyuki; Sase, Hiroyuki; Kobayashi, Ryo; Leong, Kok-Peng; Hanapi, Jamil Mohd; Uchiyama, Shigeki; Urban, Siniarovina; Toh, Ying Ying; Muhamad, Maznorizan; Gidiman, Jikos; Chappell, Nick A.
• Is Part Of: Journal of tropical ecology. Volume 30:Part 5(2014:Sep.)
• Page Start: 481
• Page End: 492
• Publication Date: 2014-09
• Subjects: Ecology -- Tropics -- Periodicals; 577.0913
• DOI: 10.1017/S0266467414000303
• Languages: English
• ISSNs: 0266-4674

Abstract

<abstract abstract-type="normal"> <title>Abstract:</title> <p>Uncertainty about the H<sup>+</sup> buffering capacity in tropical rain forest limits our ability to predict the future effect of anthropogenic deposition on the streamwater chemistry. Export of major ions to the stream and the ion-fluxes via rainfall, throughfall, litter-leachate and soil-water pathways were observed to examine the source of streamwater nutrients in a small catchment in Sabah, Malaysia. The streamwater and the ion-fluxes were measured for 3.75 and 2 y, respectively, by collecting water twice a month and setting ion-exchange-resin columns. Streamwater pH ranged from 6.5 to 7.6 and was not sensitive to water discharge controlling base cations. The NO<sub>3</sub><sup>−</sup>-N, Ca<sup>2+</sup> and Mg<sup>2+</sup> fluxes were low in atmospheric depositions (0.6, 0.5 and 0.3 kg ha<sup>−1</sup> y<sup>−1</sup>, respectively) and markedly increased in the litter layer. The NO<sub>3</sub><sup>−</sup>-N flux decreased drastically from subsoil (70 kg ha<sup>−1</sup> y<sup>−1</sup>) to the stream (1.4 kg ha<sup>−1</sup> y<sup>−1</sup>) whereas the Ca<sup>2+</sup> and Mg<sup>2+</sup> fluxes were not different between subsoil (38 and 18 kg ha<sup>−1</sup> y<sup>−1</sup>) and stream (30 and 15 kg ha<sup>−1</sup> y<sup>−1</sup>). Neutral pH in tropical streams was mainly due to the base cation leaching with deep chemical weathering in deeper strata, and a rapid decrease in NO<sub>3</sub><sup>−</sup> leaching from the subsoil to the stream.</p> </abstract>