Inversion of plant dominance–diversity relationships along a latitudinal stress gradient

Abstract

Species interactions affect plant diversity through the net effects of competition and facilitation, with the latter more prevalent in physically stressful environments when plant cover ameliorates abiotic stress. One explanation for species loss in invader-dominated systems is a shift in the competition-facilitation balance, with competition intensifying in areas formerly structured by facilitation. We test this possibility with a 10-site prairie meta-experiment along a 500-km latitudinal stress gradient, quantifying the relationships among abiotic stress, exotic dominance, and native plant recruitment over five years. The latitudinal gradient is inversely correlated with abiotic stress, with lower latitudes more moisture- and nutrient-limited. We observed strong negative effects by invasive dominant grasses on plant establishment, but only in northern sites with lower-stress environments. At these locations, disturbance was critical for recruitment by reducing the suppressive dominant (invasive) canopy. In more stressful environments to the south, the impacts of the dominant invaders on plant establishment became facilitative, and diversity was more limited by seed availability. Disturbance prevented recruitment because seedling survival depended on a protective plant canopy, presumably because the canopy reduced temperature or moisture stress. Seed limitation was similarly prevalent in all sites. Our work confirms the importance of facilitation as an organizing process for plants in higher-stress environments, even with transformations of species composition and dominance. It also demonstrates that the mechanisms regulating diversity, including invader impacts, can vary within the same plant community depending on environmental context. Because limits on native plant recruitment are environmentally contingent, management strategies that seek to increase diversity, including invader eradication, must account for site-level variations in the balance between biotic and abiotic constraints.

Long‐term effects of prairie restoration on plant community structure and native population dynamics

“…The results of this study align with these previous suggestions given that the sites in Washington experience lower abiotic stress than the sites in Oregon and British Columbia (Richardson et al ). Throughout the entirety of the experiment and extended monitoring (2005–2014), Washington sites consistently received higher rainfall and had fewer extreme drought years than both Oregon and British Columbia, potentially facilitating abundant regrowth of exotic grass species that thrive in low‐stress conditions.…”

“…Change in percent cover of exotic grasses from 2005 pre‐treatment levels (represented by the dotted line at zero). Sites are arranged in order of decreasing abiotic stress, as defined in Richardson et al (). Median values are represented by the central horizontal line, while upper and lower quartiles are represented by the corresponding ends of the box.…”

Out of the shadows: multiple nutrient limitations drive relationships among biomass, light and plant diversity

“…Carson & Pickett ; Dickson & Foster ; Richardson et al . ). We showed elsewhere how nutrient addition negatively affects soil moisture (Harpole, Potts & Suding ), and water and nitrogen generally co‐limit plant communities across a wide range of precipitation (Hooper & Johnson ; Eskelinen & Harrison ).…”

“…Shading can have positive effects on diversity, including when facilitating plant recruitment in moisture-stressed environments (e.g. Carson & Pickett 1990;Dickson & Foster 2011;Richardson et al 2012 showed elsewhere how nutrient addition negatively affects soil moisture (Harpole, Potts & Suding 2007), and water and nitrogen generally co-limit plant communities across a wide range of precipitation (Hooper & Johnson 1999;Eskelinen & Harrison 2015). Therefore, addition of multiple nutrient resources need not necessarily shift competition to above-ground light but can shift the identity of limiting resources to an alternative below-ground resource such as water (for example, see Simkin et al 2016).…”

Shifting Species Interaction in Soil Microbial Community and Its Influence on Ecosystem Functions Modulating

“…Given that virtually soil microbial species isolation and cultivation remain a longstanding challenge [18,19], biotic interactions within the microbial communities have not been taken into consideration to check whether environmental stress gradients generate patterns consistent with the SGH. In addition, this hypothesis was developed originally just for plant-plant interactions analyses, therefore most of related studies were performed and tested the SGH limited to plant communities in various habitats [20][21][22] or between plant and herbivore [23]. Moreover, a large amount of experimental works actually tested the relationships only between pair-wise interacting plants along high/low dualistic stress gradients [3].…”