Biochar Rescues Native Trees in the Biodiversity Hotspot of Mauritius

Abstract

Many tropical invasive species have allelopathic effects that contribute to their success in native plant communities. Pyrolyzed biomass (“biochar”) can sorb toxic compounds, including allelochemicals produced by invasive plants, potentially reducing their inhibitory effects on native species. Strawberry guava (Psidium cattleianum) is among the most important allelopathic invasive species on tropical islands and recognized as the most serious threat among invasive species in the global biodiversity hotspot of Mauritius. We investigated the effects of additions of locally produced biochar on native tree species in a field experiment conducted in areas invaded by strawberry guava within Mauritius’ largest national park. Growth and survivorship of native tree species were monitored over 2.5 years in plots subjected to four treatments: non-weeded, weeded, weeded + 25 t/ha biochar, and weeded + 50 t/ha biochar. Native tree growth and survivorship were strongly suppressed by strawberry guava. Biochar treatments dramatically increased native tree performance, with more than a doubling in growth, and substantially increased native tree survivorship and species diversity, while suppressing strawberry guava regeneration, consistent with growth-promoting properties and sorption of allelochemicals. We conclude that biochars, including “sustainable biochars” produced from locally accessible biomass using low-tech pyrolysis systems, have considerable potential to counteract effects of allelopathic invaders and increase the capacity for native species regeneration in tropical island ecosystems.

Biochar mitigates allelopathic effects in temperate trees

“…BCs have the capacity to sorb or immobilize toxic metals (Beesley et al, 2011; Rees et al, 2014), salts (Hammer et al, 2015; Thomas et al, 2013), and toxic organic compounds (Hale et al, 2015), including allelochemicals (Elmer & Pignatello, 2011; Gámiz et al, 2021). Allelopathy increases the negative effects of many invasive species and makes them more difficult to manage, but BC is a promising tool against allelopathic invasive species (Sujeeun & Thomas, 2022) due to its ability to sorb and reduce the bioavailability of a wide range of organic compounds (Hall et al, 2014; Kumar et al, 2020). Recent laboratory trials have shown that BCs have the potential to alleviate the inhibitory effects of a wide range of allelopathic invasive plants (Bieser et al, 2022; Shen et al, 2020; Sujeeun & Thomas, 2017).…”