Journal article
Nitrogen deposition contributes to soil acidification in tropical ecosystems
Global Change Biology, Vol.20, pp.3790-3801
20
2014
PMID: 24953639
Web of Science ID: WOS:000344375700020
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Abstract
Elevated anthropogenic nitrogen (N) deposition has greatly altered terrestrial ecosystem functioning, threatening ecosystem health via acidification and eutrophication in temperate and boreal forests across the northern hemisphere. However, response of forest soil acidification to N deposition has been less studied in humid tropics compared to other forest types. This study was designed to explore impacts of long-term N deposition on soil acidification processes in tropical forests. We have established a long-term N-deposition experiment in an N-rich lowland tropical forest of Southern China since 2002 with N addition as NH₄, NO₃ of 0, 50, 100 and 150 kg N ha⁻¹ year ⁻¹. We measured soil acidification status and element leaching in soil drainage solution after 6-year N addition. Results showed that our study site has been experiencing serious soil acidification and was quite acid-sensitive showing high acidification (pH₍ₕ₂ₒ₎<4.0), negative water-extracted acid neutralizing capacity (ANC) and low base saturation (BS,< 8%) throughout soil profiles. Long-term N addition significantly accelerated soil acidification, leading to depleted base cations and decreased BS, and further lowered ANC. However, N addition did not alter exchangeable A1ᶜ⁺, but increased cation exchange capacity (CEC). Nitrogen addition-induced increase in SOC is suggested to contribute to both higher CEC and lower pH. We further found that increased N addition greatly decreased soil solution pH at 20 cm depth, but not at 40 cm. Furthermore, there was no evidence that A1ᶜ⁺ was leaching out from the deeper soils. These unique responses in tropical climate likely resulted from: exchangeable H+ dominating changes of soil cation pool, an exhausted base cation pool, N-addition stimulating SOC production, and N saturation. Our results suggest that longterm N addition can contribute measurably to soil acidification, and that shortage of Ca and Mg should receive more attention than soil exchangeable Al in tropical forests with elevated N deposition in the future.
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Details
- Title
- Nitrogen deposition contributes to soil acidification in tropical ecosystems
- Publication Details
- Global Change Biology, Vol.20, pp.3790-3801
- Resource Type
- Journal article
- Publisher
- Wiley-Blackwell Publishing Ltd.; United Kingdom
- Series
- 20
- Copyright
- 2014 John Wiley & Sons Ltd
- Identifiers
- WOS:000344375700020; 99380090760206600
- Academic Unit
- Biology; Hal Marcus College of Science and Engineering
- Language
- English