Driving forces of soil fauna community construction
Recent global syntheses of soil communities have identified contrasting environmental controls on the distribution and abundance of soil animal groups (Alice et al., 2020). Our research shows that soil texture and temperature, especially the lowest temperature in the region, were important factors in shaping the distribution pattern of soil animals in East Asia. Similar conclusions were drawn from other studies. For example, global earthworm communities were observed to be strongly impacted by climatic variables (Phillips et al. 2019), and nematode abundances were observed to be increased with an increase in SOC content (Van Den Hoogen et al., 2019). However, these soil animal communities were also found to be influenced by other additional factors. For instance, soil acidity was found to influence global earthworm communities across natural and managed ecosystems, with higher species richness at intermediate soil pH levels (Johnston & Sibly, 2018). Nematode abundances were found to be decreased with increasing soil pH on a global scale (Van Den Hoogen et al., 2019). And interestingly termites were influenced by climatic factors on a regional scale, with termite diversity being highest in moist lowland tropical rainforest ecosystems (Jones & Eggleton, 2010).
Relationships of soil animal groups on a global scale broadly follow those identified for soil fungi and bacteria (Johnston & Sibly, 2020). On the global scale, climatic factors were found as the main factors affecting the diversity of soil fungi in global natural ecosystems (Tedersoo et al., 2014), and soil organic carbon level was found as the main factor affecting fungal diversity (Liu et al., 2015) on regional scales (Northeast China). The changes of temperature and SOC were further expected to cause microbial community composition shifts between fungal and bacterial dominance, leading to various trophic transfer efficiency to their soil animal consumers (Carrillo et al., 2016). The research results showed that SOC, temperature, especially the extreme minimum temperature are environmental factors that affected the overall distribution of soil animals in East Asia. Our study generalized these results to entire soil animal communities, and showed a dominance of small soil animals (e.g., Nematoda, Acari, Collembola) in high-latitude with low temperature and higher SOC contents, and greater abundances of larger soil animals (e.g., Chilopoda, Coleoptera) at mid- to low latitudes in more neutral temperature with lower SOC contents. Nevertheless, our research was inconsistent with the global research results of species distribution dominated by pH (Johnston & Sibly, 2020). The reason for this inconsistency may be because numerous taxa showed hemispheric asymmetries in latitudinal diversity gradients: trees (Burns, 2007), mammals (Gaston et al., 1995), termites (Eggleton et al., 1994), birds (Blackburn & Gaston, 1996), spiders (Platnick & Norman, 1991), ants (Dunn et al., 2009) and triatomids (Rodriguero & Gorla, 2004). Simultaneously, predacity soil animals are more susceptible to environmental impacts than phytophage animals (Roslin et al., 2017), which may lead to different distribution pattern of different functional soil animals in East Asia. This may be attributed to the relatively broad ecological niches of species with higher trophic levels, leading to multiple environmental requirements and adaptations (Chen et al., 2014; Turney & Buddle, 2016).