Abstract
Alpine wetlands are important ecosystems, but an increased availability of soil nutrients may affect their soil nitrous oxide (N2O) fluxes and key enzyme activities. We undertook a 3-year experiment of observing nitrogen (N) and/or phosphorus (P) addition to alpine wetland soils of the Tibetan Plateau, China, with measurements made of soil extracellular enzyme activities and soil N2O fluxes. Our study showed that soil N2O flux was significantly increased by 72% and 102% following N and N+P additions, respectively. N addition significantly increased acid phosphatase (AP) and β-1, 4-N-acetyl-glucosaminidase (NAG) activities by 32% and 26%, respectively. P addition alone exerted a neutral effect on soil AP activities, while increasing NAG activities. We inferred that microbes produce enzymes based on ‘resource allocation theory’, but that a series of constitutive enzymes or the treatment duration interfere with this response. Our findings suggest that N addition increases N- and P-cycling enzyme activities and soil N2O flux, whereas P addition exerts a neutral effect on P-cycling enzyme activities and N2O flux after 3 years of nutrient applications to an alpine wetland.
Highlights
Nitrous oxide (N2O) is the main contributor to global warming
Our results showed that the mean N2O flux in the control plot was 13.55 μg N m–2 h–1, which was comparable to the value (-2.05 to 110 μg N m–2 h–1) reported by Chen et al [34] from different wetland soils on the Qinghai-Tibetan Plateau
Our study showed that NAG activities associated with P and N+P addition in comparison with control increased by 33% and 27%, respectively, suggesting that P is more important than inorganic N for regulating the activities of NAG. This 3-year field study measured the response of soil N2O fluxes and enzyme activities to N and/or P addition in an alpine wetland on the Tibetan Plateau, China
Summary
Nitrous oxide (N2O) is the main contributor to global warming. N2O emissions from terrestrial soils have been determined to be the most important source of atmospheric N2O flux (57%) [2], which increased by nearly 20% between the 1750s and 2011s [3]. There is a large body of evidence to show that global atmospheric nitrogen (N) deposition has increased dramatically [4], with the average bulk deposition of N having increased from 13.2 kg N ha−1 yr−1 to 21.1 kg N ha−1 yr−1 between the 1980s and 2000s [5].
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