Ecological processes of soil fauna community construction
Most ecological patterns and processes in nature are scale-dependent
(Gao et al., 2014; Widenfalk et al.,
2015; Gao et al., 2021), that is, their community patterns and
construction mechanisms could be different under different spatial scale
conditions (Chase & Leibold, 2002), and may be simultaneously
controlled by processes from multiple scales (Levin, 1992, Guo er al.,
2018). Locally, pure spatial variables were important in regulating
species composition, whereas the spatially structured environmental
factors contributed most at regional scale at the northeast China (Gao
et al., 2021). Our results supported the hypothesis that the effect of
environmental processes on order turnover of soil fauna in East Asia is
more important than that of neutral processes. Our study area and the
obtained species taxon were different with the study of Gao et al.
(2021). Therefore, our results were not entirely consistent with those
of Gao’s.
The mechanism causing patterns of soil animal communities in East Asia
was driven by environmental processes, but the driving paths of
herbivorous and predatory animal communities may be different (Roslin et
al., 2017). This study showed that the effect of environmental processes
was more important than neutral processes for phytophage and predacity
faunas, and that the effects of the latitude difference for predacity
were minimal. The active dispersal abilities of soil animals separated
by a Tullgren along the soil matrix was generally very limited (Gao et
al., 2018). This may weaken the influence of the neutral process. In
contrast, soil animals were sensitive to environmental changes (Fu et
al., 2009; Wu, 2011). Thus, soil animals were more affected by
environmental processes.
These results contrasted with the findings obtained by Zhang (2016) and
Gao (2018), who determined that neutral processes explained more
variation for soil faunas. This discrepancy may result partly from the
use of spatial extents and species variables in the two studies. Zhang
(2016) and Gao (2018) focused only on northeast of China and the two
soil animal groups of beetles and mites. By comparison, our study
covered 14 research samples and three temperature belts in East Asia. In
particular, our taxon included almost all soil animal groups. Thus, we
concluded that on a large scale, environmental processes explained more
variation for turnover of soil faunas.
The effects of climate as an environmental factor on phytophages was
greater than that of soil, but the effects of climate and soil factors
in predators was basically the same. Climate, mainly temperature, drive
the species conversion of forest trees and shrubs in East Asia (Chen et
al., 2016), led to changes in the food resources of phytophagous.
Therefore, the influence of climate was observed to be greater than that
of soil as environmental driving factors. For predatory animals, the
biotic interaction (predation behavior) strength increases towards the
equator may cause the expansion of the resources available to the
predator, leading to the expansion of the niche
(Roslin et al.,
2017). The width of niche could be
restricted by more environmental factors, such as climate and soil.
Therefore, climate factors and soil factors were almost equally
important in the construction of soil animal communities in East Asia.
Finally, our study used order-level identification to ensure the
consistency of soil fauna taxon in all sites in East Asia. Ponge and
Salmon’s (2013) study showed that
environmental filtering or species
sorting culminated at the family level, and were obscured by convergent
evolution and co-adaptation at higher taxonomic levels. High
family-level diversity was commonly associated with a high structural or
trait diversity (Terlizzi et al., 2009; Zou et al., 2020). Order-level
classification was adequate for the needs of our research, because this
study only focused on the presence/absence of information on species
instead of specific traits of species. However, biological interactions
processes, such as nutritional level and food web structure, phylogeny,
and functional traits are the important factors that are often ignored
in community ecology studies. Therefore, future research should consider
more and better biological factors and distinguish the effects of
neutral and environmental processes on a community assembly.