Biochar Rescues Native Trees in the Biodiversity Hotspot of Mauritius

Sean C. Thomas,Leeladarshini Sujeeun

doi:10.3390/f13020277

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.

Highlights

Academic Editor: Qinfeng GuoThe global success of non-native invasive plants is often attributed to the lack of natural enemies that allow them to fully exploit their potential for resource competition and displace native species [1]
We conclude that biochar has significant positive effects on native tree growth and survivorship in native forest communities invaded by strawberry guava
Our results are consistent with biochar reducing allelopathic effects and altering the competitive balance of native and invasive species, thereby favoring the former

Summary

Introduction

Academic Editor: Qinfeng GuoThe global success of non-native invasive plants is often attributed to the lack of natural enemies that allow them to fully exploit their potential for resource competition and displace native species [1]. Psidium cattleianum Sabine (Myrtaceae) is likewise a highly invasive species that forms dense monotypic stands [8] and can suppress native vegetation by releasing allelochemicals into the soil [9,10,11]. Invasive plant species such as P. cattleianum have a high potential for expanding their range in tropical biodiversity hotspots and threatening plant diversity globally [12]. The negative impacts of invasive species on native biota are increasing rapidly [13], in tropical island ecosystems where ecological impacts are most acute due to limited habitat area, poor competitive ability of native species, and putative vacant niches [14]

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Conclusion