The World Health Organization declared the outbreak of the novel coronavirus (COVID-19) as a pandemic on March 11, 2020. Due to the global threat, many countries impose immediate lockdown. The impact of lockdown on the environmental pollutants and climate indicators gained considerable attention in the literature. This study aims to describe the variations in the environmental pollutants (CO, NO 2 , SO 2 , PM 2.5 and PM 10) with and without the lockdown period in the majorly hit states and provinces of the USA and China, respectively. Data during the first quarter year of 2019 and 2020 (lockdown period) was used in this study. Moreover, the effect of these pollutants on the pandemic spread was also studied. The results illustrated that the overall concentrations of CO, NO 2 and PM 2.5 were decreased by 19.28%, 36.7% and 1.10%, respectively, while PM 10 and SO 2 were increased by 27.81% and 3.81% respectively in five selected states of the USA during the lockdown period. However, in the case of chosen provinces of China, overall, the concentrations of all selected pollutants, i.e., CO, NO 2 , SO 2 , PM 2.5 and PM 10 , were reduced by 26.53%, 38.98%, 18.36%, 17.78% and 37.85%, respectively. The COVID-19 reported cases and deaths were significantly correlated with NO 2 , PM 2.5 and PM 10 in both China and the USA. The findings of this study concluded that the limited anthropogenic activities in the lockdown situation due to this novel pandemic disease result in a significant improvement of air quality by reducing the concentrations of environmental pollutants. As the trend goes on, the reduction of most pollutant concentrations is expected as long as partial or complete lockdown goes on.

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Ombrotrophic peatlands are important long-term sinks for atmospheric carbon as plant productivity exceeds litter decomposition. Changes in plant community composition may alter decomposition rates through alterations in microbial communities and activity. Such plant community driven changes in decomposition rates may however differ between microhabitats. Nevertheless, the microhabitat-context-dependency of plant community composition effects on decomposition remains poorly understood. We used a long-term (> 10 year) plant removal experiment to study how vascular plant functional types (PFTs, i.e. graminoids and ericoids) influence decomposition processes in wet lawns and hummocks. We employed the Tea Bag Index (TBI) as an indicator for early litter decomposition and carbon stabilization and assessed the potential activity of five hydrolytic extracellular enzymes (EEAs) as indicators for microbial activity. PFT removal had no effect on the TBI decomposition rate constant (k), nor on the stabilization factor (S). Yet, k increased slightly when both PFTs were absent. In the lawns, we observed higher values of k and S as compared to hummocks. PFT composition influenced four out of five hydrolytic EEAs that can drive decomposition. Yet, this influence was non-pervasive and microhabitat dependent. In wet lawns, PFT removal generally increased enzyme activities, while opposite trends were detected in the hummocks. Our results suggest an important role for vegetation change, through their influence on enzyme activity, along the lawn-hummock gradient in regulating decomposition processes in northern peatlands. This implies that potential consequences of vegetation changes on organic matter turnover, hence the peatland carbon sink function, cannot be generalized across peatland microhabitats.

Despite their low primary production, ombrotrophic peatlands are important long-term sinks for atmospheric carbon due to even lower rates of litter decomposition. Litter decomposition can be affected by plant functional types (PFTs; Graminoids, Ericoids) and microhabitat (hummock, lawn), but the microhabitat context-dependency of PFT effects on decomposition processes remains poorly understood. We used a long-term (> 10 yr) plant removal experiment, in conjunction with the Tea Bag Index (TBI), to explore how PFT removal in both hummock and lawn microhabitats influence decomposition. In parallel, we assessed potential activity of five extracellular hydrolytic enzymes as proxies for microbial activity. Our results indicate that PFT removal had no effect on the TBI decomposition constant ( k ), nor on the stabilisation factor (S). Yet, k increased slightly when both PFTs were absent. In the lawns, we observed higher values of S as compared to hummocks. A similar trend was observed for the decomposition rate constant ( k ). PFT compostion influenced the potential hyrolytic EEAs underlying decomposition process, however this influence was non-pervasive and depended on microhabitat. Our results suggest an important role for vegetation change – through their influence on enzyme activity – along the lawn-hummock gradient in regulating decomposition processes in northern peatlands. Our results highlight it is important to monitor the interplay between plant functional type composition and microhabitat in order to understand decomposition processes in peatlands.