Soil fauna community distributions
In this study, the comparative analysis was conducted on the order
composition similarities of 14 forest sites in East Asia. As expected,
smaller distances between the sites
tended to increase similarity in species composition (Figure 2). Order
richness was observed to be decreased with increasing latitude (Figure
1). This was consistent with most research findings that lower latitudes
provide more available resources (Convey, 2013; Johnston & Sibly,
2018). Decaëns (2010) pointed to an
enhanced efficiency of mutualism under tropical climates as a possible
reason for a latitudinal gradient in soil animal communities. However,
the results of this study found that the total richness of soil animals
in temperate zones was significantly higher than that in tropical and
subtropical zones, which was in line with the results of the non-linear
shifts in soil animal community with latitude studied by
Petersen and Luxton (1982). Total
soil animal biomass declined from temperate ecosystems (forests and
grass-lands) towards both arctic and tropical ecosystems and were
accompanied by shifts in soil animal community composition (Alice et
al., 2020). For instance, the biomass of smaller soil animal groups
(Nematoda, Collembola, Enchytraeidae, and Acari) decreased in tropical
ecosystems comparing to temperate ecosystems (Petersen 1982; Johnston &
Sibly, 2020). This could be resulted from different tolerance of the
diverse soil faunas to climate, especially temperature.
Based on the 14 sites we studied, the patterns of order turnover
increased significantly with increasing latitude differences for
βj and βs of overall orders, phytophage,
and predacity faunas, respectively (Figure 4). These results were
consistent with those obtained in previous studies (Abrahamczyk et al.,
2011; Ulrich et al., 2012; Andersen et al., 2015). The reasons for the
increase in order turnover rate with increasing latitude differences
could be complicated. Among the
reasons, latitudinal gradients in climatic tolerance and sampling effect
of the species pool have been mostly reported
(Dunck et al., 2016; Kent et al.,
2020). The hypothesis of latitudinal gradients in climatic tolerance
claims that species are more climatically tolerant in high than in low
latitudes (Chen et al., 2016). Lower climatic tolerance may further lead
to narrower niche breadths in tropical than in temperate mountains,
thereby decreasing the likelihood of co-occurrence of different species
and increasing the species turnover rate (Janion-Scheepers et al., 2019;
Kent et al., 2020).