Abstract
(1) Background: Increased attention has been paid to atmospheric nitrogen (N) deposition caused by human activities. N deposition quantity has seriously affected plant productivity and greenhouse gas emissions in wetlands, but the effects of N deposition frequency remain unclear. (2) Methods: We assembled microcosms, which contained vegetative individuals (ramets) of Hydrocotyle vulgaris and soil and subjected them to three frequencies (N addition 1, 2, and 14 times during the experimental period) crossed with three quantities (5, 15, and 30 g N m−2 yr−1) for 90 days. (3) Results: The quantity of N addition significantly increased the root, stem biomass, and ramets number of H. vulgaris, but decreased the spike biomass. N addition quantity significantly promoted N2O emission and inhibited CH4 emission but had no significant effect on CO2 emission. The increasing frequency of N addition significantly promoted the root-to-shoot ratio and decreased N2O emission under high N addition quantity. (4) Conclusions: In conclusion, N addition alters the reproductive strategy of H. vulgaris and enhances its invasiveness, promoting N2O emission but not the CO2 equivalent of the H. vulgaris-soil system.
Highlights
In recent years, more attention has been paid to the increasing atmospheric nitrogen (N) deposition caused by human activities [1]
(4) Conclusions: In conclusion, N addition alters the reproductive strategy of H. vulgaris and enhances its invasiveness, promoting N2O emission but not the CO2 equivalent of the H. vulgaris-soil system
In order to alleviate the contradiction between climate change and sustainable development of the wetland ecosystem, and understand the greenhouse gas emission mechanism, it is important to study the effect of atmospheric N deposition on plant growth and greenhouse gas emissions from the wetlands
Summary
More attention has been paid to the increasing atmospheric nitrogen (N) deposition caused by human activities [1]. N deposition can increase plant biomass and decrease the root-to-shoot ratio within a certain supply range [10]. N deposition alters CO2 emission through an increase in plant biomass, a decrease in the C/N ratio of litter, and the mitigation of N restriction on microbial metabolism [12]. N deposition can affect CH4 flux by altering the activity of methanogens and methanotrophs [3,13], affecting the allocation of plant biomass, and thereby the impact on CH4 production, oxidation, and transport [10,14]. N deposition can increase N2O flux in wetlands because the growth and biomass accumulation of plants with N availability provide soil microorganisms with a more labile C source, which can be used as an energy source for denitrification [15,16]
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