Microwave soil heating reduces seedling emergence of a wide range of species including invasives

Abstract

A microwave‐based process to control invasive species (seeds and adult stages) in the field prior to plant community restoration is currently under development. We investigated the effect of four microwave treatment pairings of Power × Duration (2kW4min, 4kW2min, 2kW8min, and 4kW4min) on seedling emergence of (1) an abandoned field seed bank used as a model for various plant species and (2) seeds of three species invasive in Europe: Datura stramonium (Jimson weed), Reynoutria × bohemica (Bohemian knotweed), and Solidago gigantea (Giant goldenrod). In addition, we assessed whether nontreated seeds of these three invasive species could germinate on microwave‐treated soils. As microwave soil heating usually leads to nonhomogeneous temperatures within a sample, we also assessed whether the position of seeds in the soil during microwave treatment (center vs. edges) impacted seedling emergence. Results show that the most intensive microwave treatments (2kW8min and 4kW4min), enabling the soil to reach 85°C, are highly effective in inhibiting seedling emergence of invasive species and the seed bank. The 2kW8min treatment, combining lowest power and longest exposure, is the most effective, reducing seed bank seedling emergence by 98% compared to control. The results also reveal a species‐specific response to heat, and lower microwave effectiveness on seeds located at the soil surface, which may explain the incomplete effectiveness of intensive treatments. Our results also suggest that prior microwave soil treatment does not prevent a considerable proportion of newly arrived invasive species seeds from germinating, suggesting that this method should be followed by restoration of native plant cover.

Beyond the species pool: modification of species dispersal, establishment, and assembly by habitat restoration

“…In general, the soil seed bank of degraded sites mainly consists of undesired species (Török et al ; Hess et al ; Klaus et al ; Török et al ). Thus, information about the composition of the seed bank can inform site managers about the most important future threats, such as the encroachment of weeds and invasive species.…”

“…If the seed bank is largely infested by invasive species, only its complete removal can prevent future invasion. Hess et al () provided a novel approach for eradicating the seed bank of undesired species by microwave heating of soils. Even though the method is currently being fine‐tuned for larger‐scale field application, it seems to be a promising and innovative approach to fight against invasive species without pesticide application.…”

Rain‐based soil solarization for reducing the persistent seed banks of invasive plants in natural ecosystems – Acacia saligna as a model

“…Consequently, there has been an ongoing search for effective new control methods. Recently it was reported that microwave soil heating could be a potential method to reduce the seed bank of invasive plants, but a field microwave device has not yet been developed. In recent years, our group has been involved in examining the efficacy of soil solarization in reducing the seed bank of Acacia saligna (Labill.)…”

Soil solarization based on natural soil moisture: a practical approach for reducing the seed bank of invasive plants in wetlands

“…However, unsatisfactory results and the limitations of using prescribed burning in many natural habitats have led to efforts to develop new efficient control methods. Recently, for example, microwave soil heating has been suggested as a potential method to control the seed bank of invasive plants in natural habitats (De Wilde et al 2017;Hess et al 2018), but an applicable device has not yet been developed. Our group, using Acacia saligna as a model plant, demonstrated that soil solarization has high potential as a control method for this purpose in natural habitats undergoing restoration.…”