Introduction
Understanding the mechanisms that stabilize ecosystem functions when
faced with a changing environment has been a key issue in ecology
(Tilman & Downing 1994; Tilman et al. 2006; Isbell et al.2009; Hector et al. 2010; de Mazancourt et al. 2013;
Loreau & de Mazancourt 2013; Hautier et al. 2014; Cravenet al. 2018; Wang et al. 2019b).
Greater biodiversity, especially
plant diversity, usually increases the temporal stability of biomass
production, although negative and neutral effects have been occasionally
observed (Tilman et al. 2006; Hector et al. 2010; Hautieret al. 2014; Pennekamp et al. 2018; Craven et al.2018; Wang et al. 2019b). However, the vast majority of existing
studies focused on the biodiversity of a single trophic group (Tilmanet al. 2006; Isbell et al. 2009; Hector et al.2010; Hautier et al. 2014; Hautier et al. 2015; Maet al. 2017; Wang et al. 2019b), neglecting biodiversity
across trophic levels, even though multitrophic biodiversity has been
shown to drive multiple ecosystem functions (Soliveres et al.2016; Schuldt et al. 2018; Geisen et al. 2019;
Domeignoz-Horta et al. 2020).
Soil biota, comprising an
enormous number of consumers and decomposers, represent one of the
largest reservoirs of biodiversity on Earth (Orgiazzi et al.2016; Geisen et al. 2019; Thakur et al.2020). A growing number of
studies suggest that soil biodiversity has an essential impact on plant
diversity, community composition, biomass production, plant-plant
interactions and plant tolerance to stress factors, as well as nutrient
cycling (Wagg et al. 2014; Bardgett & van der Putten 2014;
Delgado-Baquerizo et al. 2016; Wagg et al. 2019; Lianget al. 2019; Domeignoz-Horta et al. 2020; Guerra et
al. 2020). Recent work has provided a conceptual framework showing that
plant and soil biodiversity can jointly influence the stability of
biomass production via regulating these plant attributes (Yang et
al. 2018). However, there is increasing concern that soil and plant
biodiversity is threatened by anthropogenic environmental change
(Tsiafouli et al. 2015; Gossner et al. 2016; Banerjeeet al. 2019; Geisen et al. 2019; Zhou et al. 2020).
Hence, it is important to understand how biodiversity loss in both soil
and plant communities affects the stability of biomass production will
provide a broader perspective.
Here we conducted a fully factorial experiment manipulating plant
diversity and soil biodiversity using model grassland microcosms (Fig.
1). We used a dilution-to-extinction approach (Yan et al. 2015;
Hol et al. 2015; Roger et al. 2016) to create a gradient
of soil biodiversity, and then established grassland microcosms of
different plant species richness at each point along the soil
biodiversity gradient under greenhouse conditions.
We focused on the temporal
stability of biomass production, defined as the ratio of the temporal
mean to the standard deviation of plant community biomass (Tilmanet al. 2006). Because the constant environment in the greenhouse
does not capture natural variability, environmental variation in
precipitation was simulated by inducing three wet-dry cycles in all
microcosms to investigate the effects of the biodiversity treatments on
the temporal stability of biomass production.
Considering the significance of soil biodiversity on plant attributes
(Yang et al. 2018), we predicted that soil biodiversity loss will
reduce the temporal stability of biomass production. Specifically, we
tested whether and how soil biodiversity interacts with plant diversity
in terms of species richness and functional diversity to influence
temporal stability. Furthermore, we investigated how multitrophic
biodiversity, accounting for plant and soil biodiversity, affects
temporal stability. We find that both greater plant and soil
biodiversity had positive effects on the temporal stability of community
biomass production, but plant and soil biodiversity independently
affected temporal stability. Multitrophic biodiversity is positively
associated with temporal stability.