Introduction
Richness-stability relationships (RSRs) are a basic question of
increasing concern in modern ecology (McCann 2000; Dixon et al.2021). RSRs describe the most simplified links between species pool and
complex system persistence, and could offer a substantial, convenient,
and valuable guide to several ecological fields including artificial
community composition (Dixon et al. 2021), biological
conservation formulation (Griffiths & Philippot 2013), and ecosystem
stability assessment (García-Palacios et al. 2018).
Unfortunately, according to previous community studies, RSRs can vary
widely (Sankaran & McNaughton 1999; Naeem et al. 2000; Arthur &
Dech 2016; Baert et al. 2016; O’Brien et al. 2017;
Pennekamp et al. 2018), but the potential cause of these
differences has yet to be resolved.
Interactions between community members, both positive (e.g., mutualism
and cooperation) and negative interactions (e.g., competition and
predation), were predicted as a potential influencer of RSRs (May &
MacDonald 1978; Damore & Gore 2012). Positive interactions
theoretically benefit to extend the niche width of species and offer
them the ability to live under conditions that were originally
unfavorable, thus increasing their tolerance to stress (Damore & Gore
2012). Negative interactions were also been predicted as beneficial for
community stability in several models (Pinsky 2019). However, there is
still no empirical evidence to support whether interactions influence
RSRs.
The microbial community is a species rich and functionally important
component of ecosystems (Griffiths & Philippot 2013). However, the
relatively few studies, primarily in aquatic ecosystems, that have
investigated microbial community RSRs, have come to contradictory
conclusions. For instance, aquatic micro-cultivations utilizing
different combinations of 6 ciliate species (total of 690 incubations)
reported a negative relationship between richness and resistance
(Pennekamp et al. 2018), while a positive relationship between
richness and resistance of microbial community was reported from two
lakes in Canada (Hillebrand et al. 2018). Yet, the soil microbial
community plays an irreplaceable role in decomposition, nutrient
cycling, and above-ground community regulation for terrestrial
ecosystems (Franciska & Ashley 2013). The variation in community
composition caused by environmental stress would threaten the functions
relevant to the soil microbial community (Franciska & Ashley 2013). The
lack of soil microbial community RSRs research significantly hampers a
deeper understanding of terrestrial ecosystem stability and the response
to climatic and anthropogenic stresses (Franciska & Ashley 2013).
In order to investigate RSRs of the soil microbial community in
terrestrial ecosystems and explore the effect of interactions on RSRs,
we selected 5 successional stage ecosystems (bare soil, grass, shrub,
deciduous forest, and coniferous forest) from a typical glacial retreat
area to compare the microbial community stability components (resistance
and resilience) under simulated climatic stress. There were two main
reasons for choosing this successional gradient. Firstly, the ecosystems
were located in a glacial retreat area of approximately 3km×0.5km with
less than 100m difference in elevation, sharing the same regional
precipitation and temperature, therefore the types and extents of
climatic stress exerted on them could be treated as the same (Li &
Xiong 1995). Secondly, the richness and network structure of the
microbial community varies among successional stages, offering a natural
gradient to analyze how interaction types influence RSRs (Jiang et
al. 2018). In this study, we found that balanced positive and negative
interactions of the community offered a positive richness-resistance
relationship, while unbalanced interactions offered a negative
relationship.