Soil–Occupancy Effects of Invasive and Native Grassland Plant Species on Composition and Diversity of Mycorrhizal Associations

Abstract

Diversified grasslands that contain native plant species can produce biofuels, support sustainable grazing systems, and produce other ecosystem services. However, ecosystem service production can be disrupted by invasion of exotic perennial plants, and these plants can have soil-microbial “legacies” that may interfere with establishment and maintenance of diversified grasslands even after effective management of the invasive species. The nature of such legacies is not well understood, but may involve suppression of mutualisms between native species and soil microbes. In this study, we tested the hypotheses that legacy effects of invasive species change colonization rates, diversity, and composition of arbuscular-mycorrhizal fungi (AMF) associated with seedlings of co-occurring invasive and native grassland species. In a glasshouse, experimental soils were conditioned by cultivating three invasive grassland perennials, three native grassland perennials, and a native perennial mixture. Each was grown separately through three cycles of growth, after which we used T-RFLP analysis to characterize AMF associations of seedlings of six native perennial and six invasive perennial species grown in these soils. Legacy effects of soil conditioning by invasive species did not affect AMF richness in seedling roots, but did affect AMF colonization rates and the taxonomic composition of mycorrhizal associations in seedling roots. Moreover, native species were more heavily colonized by AMF and roots of native species had greater AMF richness (number of AMF operational taxonomic units per seedling) than did invasive species. The invasive species used to condition soil in this experiment have been shown to have legacy effects on biomass of native seedlings, reducing their growth in this and a previous similar experiment. Therefore, our results suggest that successful plant invaders can have legacies that affect soil-microbial associations of native plants and that these effects can inhibit growth of native plant species in invaded communities.

Negative competitive effects of invasive plants change with time since invasion

“…These studies show higher impacts with time since invasion, with the exception of one study that found the impact of an invasive plant was eroded over time by soil pathogens (Dostál et al 2013) ( Table 2). Higher ecological impacts over time may be attributable to a lag time in observed effects in recently invaded areas (Crooks 2005) or legacy effects of early invaders at older, more established sites (Grove et al 2012, Jordan et al 2012). In addition, subtle ecosystem-level impacts such as changes to soil characteristics may accrue over time, such that the extent of the impact may not be observed for decades; such long-term cumulative impacts are generally caused by ecosystem engineers (see Crooks 2002, Strayer et al 2006).…”

Differential effects of abiotic factors and host plant traits on diversity and community composition of root-colonizing arbuscular mycorrhizal fungi in a salt-stressed ecosystem

“…Recent studies have revealed that roots of native species had higher (Jordan et al 2012) or lower (Lekberg et al 2013) AMF richness than these of the invaders. By contrast, the composition of AMF colonizers was significantly different between invasive and native hosts, but no effect of plant origin was detected for the AMF diversity in our study, indicating the invaders, as the native plant species, might have also benefited from a substantial number of AMF taxa for thriving in the salt-stressed ecosystem.…”

“…Nevertheless, knowledge about AMF diversity of plant species in salt-affected ecosystems remains insufficient, and the environmental constraints and host effects in saline ecosystems have yet to be investigated. The AMF communities of plants from different origins (Greipsson and DiTommaso 2006;Moora et al 2011;Jordan et al 2012;Lekberg et al 2013) and life style Lugo et al 2012;Torrecillas et al 2012) have been investigated, but again, little is known about the effect of the origin and life style of plant species on AMF diversity and community in salt-stressed ecosystems.…”

The Relationship between the Distribution of Invasive Plant Alternanthera philoxeroides and Soil Properties is Scale-Dependent

“…Exploring the relationship between invasive species and environmental factors will help to elucidate invasion mechanisms. Human disturbance, temperature, latitude, soil properties, soil microorganisms, and various environmental factors may be associated with biological invasion [12][13][14][15][16]. Latitude strongly affects the distribution pattern of invasive plants in China at the provincial scale [17].…”

“…Although numerous studies have documented the relationship between plant invasion and soil properties [5,15,[27][28][29], little attention has been paid to understanding how soil properties affect the distribution of A. philoxeroides and whether such abiotic factors are scale-dependent. The aim of our work was to explore the environmental factors that influence the distribution of A. philoxeroides in the main rivers around Nansi Lake at two different scales (river scale and plot scale).…”