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Gross rates of nitrogen transformation in soils of a global biodiversity hotspot (Western Ghats, India)
Author(s) -
Sharma Niharika,
Kumar Sanjeev
Publication year - 2020
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.201900126
Subject(s) - nitrification , soil water , mineralization (soil science) , ecosystem , nitrogen cycle , environmental science , ammonium , nitrogen , environmental chemistry , chemistry , ecology , soil science , biology , organic chemistry
Background: Being one of the important nutrients required by plants during photosynthesis, nitrogen (N) exerts a significant control on primary productivity and carbon dioxide sequestration. Therefore, it is essential to quantify the rates of N cycling processes, such as gross N mineralization and nitrification, to understand the flow and availability of N in different ecosystems. Lack of such data in tropical regions, particularly the Indian subcontinent, has constrained our understanding of N dynamics in soils of the subcontinent. Aims: Here, we report the results of gross N transformation rates from the hot and humid tropical forest soils of the Western Ghats, one of the global biodiversity hotspots located in India. Results: The experiments conducted using the 15 N isotope dilution technique showed higher average gross N mineralization (2.6 ± 1.1 mg N kg −1 d −1 ) and gross nitrification (1.7 ± 1.1 mg N kg −1 d −1 ) rates in the top soil layers (0–20 cm), which decreased significantly with depth (20–40 cm) indicating potential for higher microbial activity in the top soils. The overall consumption rate of mineral N exceeded its production rate with higher consumption of ammonium (NH 4+) than nitrate (NO 3-) suggestingNH 4+as a preferred N source for microbes. The consumption ofNH 4+was higher throughNH 4+immobilization than nitrification indicating active N conservation mechanism and an efficient microbial adaptation. Conclusion: Despite high rates of consumption, accumulation ofNH 4+andNO 3-in soils of the Western Ghats suggested additional sources of mineral N other than internal recycling of N. Long residence time ofNH 4+andNO 3-in soils implied longer availability of unutilized mineral N leading to high soil acidity and potential for loss of N through leaching and denitrification.