Climatic zone effects of non-native plant invasion on CH and NO emissions from natural wetland ecosystems.

Plant invasion can significantly alter the carbon and nitrogen cycles of wetlands, which potentially affects the emission of greenhouse gases (GHGs). The extent of these effects can vary depending on several factors, including the species of invasive plants, their growth patterns, and the climatic conditions prevailing in the wetland. Understanding the global effects of plant invasion on the emission of methane (CH) and nitrous oxide (NO) is crucial for the climate-smart management of wetlands. Here, we performed a global meta-analysis of 207 paired case studies that quantified the effect of non-native plant invasion on CH and NO emissions in tropical/sub-tropical (TS) and temperate (TE) wetlands. The average emission rate of CH from the TS wetlands increased significantly from 337 to 577 kg CH ha yr in areas where native plants had been displaced by invasive plants. Similarly, in TE wetlands, the emission rates increased from 211 to 299 kg CH ha yr following the invasion of alien plant species. The increase in CH emissions at invaded sites was attributed to the increase in plant biomass, soil organic carbon (SOC), and soil moisture (SM). The effects of plant invasion on NO emissions differed between TS and TE wetlands in that there was no significant effect in TS wetlands, whereas the NO emissions reduced in TE wetlands. This difference in NO emissions between climate zones was attributed to the depletion of NH and NO in soils and the lower soil temperature in temperate regions. Overall, plant invasion increased the global net CH emissions from natural wetlands by 10.54 Tg CH yr. However, there were variations in CH emissions across different climatic zones, indicated by a net increase in CH emissions, of 9.97 and 0.57 Tg CH yr in TS and TE wetlands, respectively. These findings highlight that plant invasion not only strongly stimulates the emission of CH from TS wetlands, but also suppresses NO emissions from TE wetlands. These novel insights immensely improve our current understanding of the effects of climatic zones on biogeochemical controlling factors that influence the production of greenhouse gases (GHGs) from wetlands following plant invasion. By analyzing the specific mechanisms by which invasive plants affect GHG emissions in different climatic zones, effective strategies can be devised to reduce GHG emissions and preserve wetland ecosystems.