Linking patterns and processes through ecosystem engineering: effects of shrubs on microhabitat and water status of associated plants in the high tropical Andes

Abstract

9Studies on alpine and semi-arid environments indicate that plants that act as ecosystem engineers improve 10 microhabitat conditions and modify local plant abundance and diversity. However, few studies have linked these 16show that H. laricifolium dampened temperature oscillations and increased soil water and organic matter contents, 17 the effect being more pronounced at the drier, lower elevation site. While positively associated forbs showed an 18 improvement in their water status when growing under the crown, the species with the lowest water potentials and 19 higher water-stress tolerance were grasses with a negative spatial relation with the shrub; this was consistent at both 20 elevations. Moreover, the effect of the shrub on the water status and abundance of the exotic herb Rumex acetosella 21 changed from positive in the drier site to negative in the more mesic site. Our results provide mechanistic evidence 22 for interpreting spatial association patterns between nurse plants and other species in the alpine tropics. We propose 23 that stress resistance strategies (tolerance vs. avoidance) and origin (native vs. exotic) influence interactions with 24 ecosystem engineers. 25

Evidence of Facilitation Cascade Processes as Drivers of Successional Patterns of Ecosystem Engineers at the Upper Altitudinal Limit of the Dry Puna

“…However, previous research [22, 23] proved that cushion plants create thermally-buffered habitat patches with higher humidity and lower temperature than surrounding open areas. Available data about soil beneath shrubs and tussocks showed marked differences in that below the tussock patches the temperature was lower than below shrubs.…”

“…Recent studies focused on alpine environments at inter-tropical latitudes, demonstrated how ecosystem engineers are capable of enhancing landscape-level richness by adding new species to the community through the regulation of temperature extremes and the modification of soil properties [22]. Moreover, they demonstrated how these nurse-induced microhabitat modifications positively influenced the physiological parameters of facilitated species [23]. However, other authors found contrasting results on the effect of ecosystem engineers on species richness at a wide scale [4].…”

Facilitation and edge effects influence vegetation regeneration in old‐fields at the tropical Andean forest line

“…; Ramírez et al. ). Plants may also exert a facilitation effect through other processes, such as litter accumulation (Facelli & Pickett ) or by attracting seed dispersing animals, reducing the effect that the distance to the forest edge has on dispersal (Duncan & Chapman ).…”

A burrowing ecosystem engineer positively affects its microbial prey under stressful conditions

“…The facilitating species studied under the stress‐gradient hypothesis are commonly ecosystem engineers. For example, nurse plants shelter seedlings of other species from harsh conditions in the microclimate formed by their canopy, but in the absence of such stress the plants merely compete (Ramírez, Rada, & Llambí, ). There has been increased effort to investigate the applicability of the stress‐gradient hypothesis to species other than plants (Bakker, Dobrescu, Straile, & Holmgren, ; Dangles, Herrera, & Anthelme, ; Fugère et al, ).…”