Invasion‐induced root–fungal disruptions alter plant water and nitrogen economies

Abstract

Despite widespread evidence that biological invasion influences the biotic and abiotic soil environments, the extent to which each of these pathways underpins the effects of invasion on native plant traits and performance is unknown. Leveraging a long-term (14-yr) manipulative field experiment, we show that an allelochemical-producing invader, Alliaria petiolata, affects native plants through biotic mechanisms, altering the soil fungal community composition, with no apparent shifts in soil nutrient availability. These changes in belowground soil fungal communities resulted in a high cost of resource uptake for native forest perennial herbs and a shift in functional traits linked to their carbon and nutrient economies. Furthermore, we illustrate that some species in the invaded community compensate for high nutrient costs by reducing nutrient uptake and maintaining photosynthesis by expending more water. This demonstrates a trade-off in trait investment that increases nutrient use efficiency as nutrient costs increase. Our results show that invasion-induced disruptions in the soil fungal community belowground can cascade to affect aboveground plant communities via shifts in physiological traits needed to maintain plant water and nutrient economies. These complex above-belowground linkages suggest that plant invasions should be evaluated at the system-level to fully understand and predict their impact on native plants and communities.

Dark diversity at home describes the success of cross‐continent tree invasions

“…Following the mycorrhizal‐associated nutrient economy hypothesis, in temperate regions, AM trees enhances a fast decomposition of high‐quality litter, while the opposite is described for ECM trees (Phillips et al, 2013). This implies that higher amounts of inorganic N can be quickly uptaken by AM plants, leading to nitrogen‐rich leaves, also occurring in non‐native species (Bialic‐Murphy et al, 2021; Phillips et al, 2013). Indeed, our findings show that higher leaf nitrogen content enhances invasion success.…”

Accelerated gross nitrogen cycling following garlic mustard invasion is linked with abiotic and biotic changes to soils

“…flexibility in favor of NO 3 − could result in garlic mustard accelerating nitrification process rates by stimulating ammonia oxidizing communities, as has been found for other invasive plant species (Hawkes et al, 2005;Shannon-Firestone et al, 2015;McLeod et al, 2016). Finally, garlic mustard can change resource use patterns in its competitor plants via disruptions to belowground fungal communities (Bialic-Murphy et al, 2021), indicating another potential microbiallymediated mechanism for garlic mustard to alter soil N cycling processes. If garlic mustard invasions reduce microbial N competition and stimulate N cycling functional groups, we would expect increases in N mineralization and nitrification rates (Figures 1B,E).…”