Plant assemblages in atmospheric deposition

Abstract

<p><strong>Abstract.</strong> Plants disperse spores, pollen, and fragments into the atmosphere. The emitted plant particles return to the pedosphere by sedimentation (dry deposition) and/or by precipitation (wet deposition) and constitute part of the global cycle of substances. However, little is known regarding the taxonomic diversities and flux densities of plant particles deposited from the atmosphere. Here, plant assemblages were examined in atmospheric deposits collected in Seoul in South Korea. A custom-made automatic sampler was used to collect dry and wet deposition samples for which plant assemblages and quantities were determined using high-throughput sequencing and quantitative PCR with universal plant-specific primers targeting the internal transcribed spacer 2 (ITS2) region. Dry deposition was dominant for atmospheric deposition of plant particles (87 %). The remaining 13 % was deposited by precipitation, i.e., wet deposition, via rainout (in-cloud scavenging) and/or washout (below-cloud scavenging). Plant assemblage structures did not differ significantly between dry and wet deposition, indicating that washout, which is likely taxon-independent, predominated rainout, which is likely taxon-dependent, for wet deposition of atmospheric plant particles. A small number of plant genera were detected only in wet deposition, indicating that they might be specifically involved in precipitation through acting as nucleation sites in the atmosphere. Future interannual monitoring will control for the seasonality of atmospheric plant assemblages observed at our sampling site. Future global monitoring is also proposed to investigate geographical differences and investigate whether endemic species are involved in plant-mediated bioprecipitation in regional ecological systems.</p>

Falling bacterial communities from the atmosphere

“…Large sedimentation velocities were observed for bacteria (Fig. 6 and Table 1 ), with a mean of 1.72 cm s − 1 , which is greater than that previously reported for the velocities of fungi (0.80 cm s − 1 ) [ 17 ] and plants (0.40 cm s − 1 ) [ 43 ] (Table 2 ). The large sedimentation velocity was associated with the large aerodynamic diameter of bacteria (Table 2 ).…”

“…On average, precipitation contributed to 95% of total bacterial deposition in our sampling site in Korea. The large contribution of precipitation might be in part due to their large-size particles, which can serve as efficient nuclei in clouds (e.g., as giant cloud condensation [17,43] were analyzed here. Briefly, the sampling site was on a university campus in a hilly suburban forested area in the Seoul Special City, the capital megacity of South Korea.…”

“…Briefly, the sampling site was on a university campus in a hilly suburban forested area in the Seoul Special City, the capital megacity of South Korea. Detailed information of our sampling site, such as the vegetation, topography, climate characteristics, and weather conditions such as temperature, relative humidity, wind velocity, and precipitation, is available in our previous publications [17,43]. Briefly, deposition samples were collected using an automatic dry and wet deposition sampler [44].…”

“…3). The high bacterial concentration in May is possibly due to high concentrations of non-bacterial particles, such as Asian dust and airborne pollen, which are known to increase in Korea during the spring months [43,[86][87][88] and serve as external vectors for bacteria dispersal [15,[89][90][91].…”

“…Here, we wished to extend our investigation into bacterial analyses. Specifically, we reanalyze air, sedimentation, and precipitation samples that were previously collected in Seoul in South Korea from May to November 2015 for our fungal [ 17 ] and plant [ 43 ] analyses. These samples were collected by an automatic dry and wet deposition sampler [ 44 ] and a collocated eight-stage Andersen sampler [ 45 ].…”