Size-Mediated Interaction between a Cushion Species and Other Non-cushion Species at High Elevations of the Hengduan Mountains, SW China

Abstract

Arenaria polytrichoides (Caryophyllaceae) is a common cushion plant occurring at high elevations in the Himalaya-Hengduan Mountains, SW China. It frequently has other non-cushion species growing within its canopy, forming a contrast with the surrounding areas because it creates patches of higher diversity and greater biomass. In this study, we examined the relationship between the cushions and associated non-cushion species along a gradient of cushion size. A total of 200 A. polytrichoides individuals were selected to fit four size classes. Field measurements were carried out to assess canopy structure, functional traits relevant to growth and reproduction, and soil quality below cushions along the size gradient. Furthermore, the size effect of cushions on the richness and abundance of species and biomass production was also examined. All the morphological variables examined exhibited a positive correlation with cushion size, as did the nutrients under cushions. Large and compact cushions were associated with higher soil nutrient contents compared with small and loose cushions. As a result of these biogenic environmental changes, there was a stronger facilitation effect performed by large cushions. Data pertaining to functional traits revealed that large cushions benefit from the enhanced resources within their compact structure and exhibit greater fitness and a higher reproductive output than small cushions. Our data indicated that interactions occur between cushion species and other plants depending on the size of the cushions, probably because of the greater heterogeneity of conditions beneath larger cushions. These findings provide a clear demonstration of the generally overlooked importance of the traits of nurse plants, such as size and age, in terms of their facilitative effects.

Local trampling disturbance effects on alpine plant populations and communities: Negative implications for climate change vulnerability

“…Comparison of our data with data gathered for another facilitation study (Butterfield et al., ) at one of our sites (Val Bercla at Fallerfurgga) shows that our control areas had significantly higher species richness (Supporting Information Figure A8a in Appendix ), however our data represents the lower end of cushion size distribution (Supporting Information Figure A8b in Appendix ). As found in many other studies, we would expect a positive correlation between nurse plant size and species richness and diversity (e.g., Incerti et al., ; Molenda, Reid, & Lortie, ; Tewksbury & Lloyd, ; Yang, Chen, Schöb, & Hang, ). Smaller nurse plants understandably cannot provide the same microhabitat shelter that larger ones do, and likely act as competitors to other species in the area as they establish.…”

Shift from facilitative to neutral interactions by the cushion plant Silene acaulis along a primary succession gradient

“…The size and morphological traits of the facilitator may also change along stress gradients, which can play a role for interactions with other species (Bonanomi et al., ; Pyšek & Liška, ; Schöb et al., ; Yang, Chen, Schöb, & Sun, ). Bigger cushions provide more space, environmental heterogeneity and nutrients available for other species (Yang et al., ). Furthermore, Bonanomi et al.…”

Cushion and shrub ecosystem engineers contribute differently to diversity and functions in alpine ecosystems

“…Plant–plant interactions, both negative and positive, can influence community attributes and ecosystem functions (Callaway et al., ; Cavieres & Badano, ; Cavieres et al., ; Chen, Schöb et al., ; Chen, Yang et al., ; Kikvidze et al., , ; Pugnaire, Zhang, Li, & Luo, ). In recent decades, positive (or facilitative) interactions have been consistently shown to play important roles in alpine ecosystems where environmental conditions are extremely severe (Anthelme, Buendia, Mazoyer, & Dangles, ; Anthelme, Meneses, Human, Pozo, & Dangles, ; Badano & Cavieres, ,b; Cavieres et al., ; Chen, Schöb et al., ; Chen, Yang et al., ; Hupp, Llambí, Ramírez, & Callaway, ; Yang, Chen, Schöb, & Sun, 2017; Yang, Niu, Cavieres, & Sun, ).…”

“…In addition, this area hosts traditional pastures of the local Tibetan people where overgrazing is becoming increasingly severe (Fu, Zhao, & Du, ; Li et al., ), resulting in widespread and heavy grazing pressure (Wang et al., ). Cushion‐forming species are widely distributed in this area and have been shown to positively influence community attributes (Chen, Schöb et al., ; Chen, Yang et al., ; Yang et al., , ); they occupy a large elevation range, from ca. 4,000 m to ca.…”