Fertilization during mineland rehabilitation may shift competitive outcomes toward invasive species

Abstract

Managing invasive species is essential for achieving mineland rehabilitation goals and ensuring the long-term provision of critical ecosystem services while preventing new dispersion sources to neighboring areas. Traditional techniques include chemical and manual weeding, but frequent reinvasion limits their long-term success. Therefore, additional integrated tools, such as stimulating natural competitors, may become necessary, especially where sensitive ecosystems, e.g. the ferruginous savanna ecosystem (cangas) from the Carajás National Forest, Eastern Amazon, Brazil, are found nearby rehabilitation sites. Here, we investigate the influence of different substrates and fertilization levels on the biotic interactions between two native canga grasses (Axonopus longispicus and Paspalum cinerascens) and the invasive molasses grass (Melinis minutiflora), which is frequently found in anthropized and natural ecosystems in Latin America. Nutrient application significantly influenced the growth, resource use strategies, and competitive outcomes of M. minutiflora. Nutrient application has positive effects on the growth of native species when cultivated in isolation but reduces plant development when subjected to competition with molasses grass, potentiating the invader. Although neither of the tested native species exhibited competitive advantages over M. minutiflora, increased nitrogen availability favored the competitive ability of this invasive grass. Thus, eliminating fertilization during mineland rehabilitation may be important for reducing the cover of M. minutiflora in the Carajás region, as sensitive canga ecosystems lack natural barriers against invasion. This strategic approach mitigates the operational risks and costs associated with combating invasive species from rehabilitating minelands, reducing propagule pressure on neighboring canga areas.