Contrasting responses of different functional groups stabilize community responses to a dominant shrub under global change

Abstract

Changes in precipitation regimes and nitrogen deposition levels due to global change are altering terrestrial ecosystems worldwide. Most attempts at understanding how biotic interactions affect plant species and community responses to global change have focused on biotic interactions measured at the community level. However, these approaches ignore that communities include functionally dissimilar species that might respond differently to changes in the effects of dominant neighbours along environmental gradients. We test the hypothesis that plant species with differences in functional traits may exhibit contrasting interactions with a dominant shrub species within a single community, thereby stabilizing community‐level responses to the effects of global change. We manipulated water and nitrogen applications in a semi‐arid dune community in northern China, quantified the biomass of herbaceous species occurring below the dominant shrub, Artemisia ordosica, and in adjacent open patches (without the shrub), and measured herbaceous species height and leaf dry matter content. The effects of A. ordosica were quantified at the species, group and community levels using the relative interaction index (RII). Redundancy analysis was performed on species traits and the RII values to assess the relationships between functional differences in species and plant–plant interactions. Species were then grouped using a cluster analysis and the RII values were recalculated at the group level. The redundancy analysis showed that species height and leaf dry matter content were significantly correlated to the changes in species' responses to the effect of A. ordosica along treatments. The four groups of species identified by the cluster analysis showed contrasting variations in competitive or facilitative responses depending on species traits and environmental treatments. However, the interactions measured at the group level balanced the community‐level responses, as we found no significant changes in the effects of A. ordosica along treatments for community biomass, richness and functional diversity indices. Synthesis. Our findings indicate that species with different functional strategies within a community exhibit contrasting responses to a dominant shrub along environmental gradients. These contrasting changes in plant–plant interactions of functionally different species may balance the responses of community‐level metrics. This suggests that functional differences between species groups and the balance of plant–plant interactions stabilize community responses to global change.

Artemisia sieberishrubs have contrasting specific effects on understory species in Iranian steppes

“…This result highlights that communities are complex units of interacting species from different functional strategies (Michalet et al, 2015a). This finding is key since balancing within‐community responses to environmental conditions and effects of neighbours may stabilize community responses to climate change, as shown by Bai et al (2021) in continental dune communities of North China.…”

“…This result highlights that communities are complex units of interacting species from different functional strategies(Michalet et al, 2015a). This finding is key since balancing within-community responses to environmental conditions and effects of neighbours may stabilize community responses to climate change, as shown byBai et al (2021) in continental dune communities of North China.Consistent with our third hypothesis, and the results of several authors(Michalet et al, 2015a;Wang et al, 2017), we found that the different responses of subordinate species to the shrub's effects were significantly related to community composition, as shown by variation in the relative frequency and abundance of group A and group B between the intact-shrub and shrub-removed and open treatments. Thus, balancing responses of different species groups at the community level may contribute to explaining community composition.…”

“…For example, Michalet et al (2015a) found in a species‐rich subalpine shrubland community from the Tibet Plateau (China) that herbaceous subordinate species had either positive or negative responses to the direct and indirect effects of dominant shrubs and grasses. Furthermore, Bai et al (2021) showed in a desert shrub sand dune community that the contrasting variation in responses to a dominant shrub of understorey species with contrasting morphological traits could stabilize community response to watering and fertilization‐simulating global change effects.…”

Strong homogenization effects of shrubs on nematode communities across large spatial scales on the Qinghai-Tibet Plateau

“…However, the increased MAT increased the rhododendron andpotentilla effects and decreased the salix effect on the homogenization of nematode communities. A possible explanation was the differences in shrub crown diameter, which was related to litter inputs and was recognized as a good proxy of shrub competitive ability and influence range (Zhang et al , 2020;Bai et al , 2021). Compared with other shrubs, salix had the largest crown diameter, and its crown diameter increased significantly with MAP (Figure S6, Figure S7d).…”

Extreme precipitation increases the productivity of a desert ephemeral plant community in Central Asia, but there is no slope position effect

“…Through niche differentiation of roots, below-ground resources such as soil water and nutrients can be fully utilized, which is not only conducive to the coexistence of species but also enables them to cope with environmental changes (Schwinning & Ehleringer, 2001;Tiemuerbieke et al, 2018). Moreover, a recent study reported that functional differences between species groups and plant-plant interactions stabilize community responses to global change scenarios such as increased precipitation (Bai et al, 2021).…”