Native Amazonian Canga Grasses Show Distinct Nitrogen Growth Responses in Iron Mining Substrates

Abstract

Native species may have adaptive traits that are advantageous for overcoming the adverse environmental conditions faced during the early stages of mine land rehabilitation. Here, we examined the nitrogen (N) growth responses of two native perennial grasses (Axonopus longispicus and Paspalum cinerascens) from canga in nutrient-poor iron mining substrates. We carried out vegetative propagation and recovered substantial healthy tillers from field-collected tussocks of both species. These tillers were cultivated in mining substrates at increasing N levels. The tillering rates of both species increased with the N application. Nonetheless, only in P. cinerascens did the N application result in significant biomass increase. Such growth gain was a result of changes in leaf pigment, stomatal morphology, gas exchanges, and nutrients absorption that occurred mainly under the low N additions. Reaching optimum growth at 80 mg N dm−3, these plants showed no differences from those in the field. Our study demonstrates that an input of N as fertilizer can differentially improve the growth of native grasses and that P. cinerascens plants are able to deposit high quantities of carbon and protect soil over the seasons, thus, making them promising candidates for restoring nutrient cycling, accelerating the return of other species and ecosystem services.

Low fertilization optimizes the water use efficiency of an Amazonian canga grass for mineland rehabilitation

“…In a recent work with Paspalum cinerascens (Döll) A.G.Burm. & C.N.Bastos, Caldeira et al (2021) highlighted the potential of this species to colonize mining waste substrates. Paspalum cinerascens is a native perennial grass of the canga ecosystems of Serra dos Carajás, in the eastern Brazilian Amazon (Viana et al 2018).…”

“…In the beginning of the rehabilitation processes, seeds of nonnative annual herbs are conventionally used, mostly because of their feasibility to be applied in broad areas . While less information exists on native species, they may be better adapted to unique and severe edaphic and climatic conditions, such as post mining substrates (Oliveira de Araujo et al 2020;Caldeira et al 2021), and can contribute to restoring local network interactions, thereby reducing the risk of biological invasions and the emergence of undesired new ecosystems (Gastauer et al 2020a). Efforts have been made to select promising local native species to restore mining areas in many countries such as Brazil Zappi et al 2018;Caldeira et al 2021), Russia (Treschevskaya et al 2019) and South Africa (Titshall et al 2013), among others.…”

“…While less information exists on native species, they may be better adapted to unique and severe edaphic and climatic conditions, such as post mining substrates (Oliveira de Araujo et al 2020;Caldeira et al 2021), and can contribute to restoring local network interactions, thereby reducing the risk of biological invasions and the emergence of undesired new ecosystems (Gastauer et al 2020a). Efforts have been made to select promising local native species to restore mining areas in many countries such as Brazil Zappi et al 2018;Caldeira et al 2021), Russia (Treschevskaya et al 2019) and South Africa (Titshall et al 2013), among others. The successful use of native species was reported in the reclamation of coal mining in the North American Appalachians (Fields-Johnson et al 2012) and for the restoration of ecosystem functions of bauxite mines in Western Australia (Grant et al 2007).…”

“…Covering large iron ore reserves in the mountain outcrops of the Amazon rainforest, the canga vegetation is well adapted to the adverse local environmental conditions, marked by a thin and metal rich soil, high radiation, wind, temperature and severe seasonal drought period (Skirycz et al 2014). As a perennial grass widely distributed in the canga of Serra dos Carajás (Viana et al 2018), P. cinerascens was listed as one of the most promising species for mineland reclamation in this region (Zappi et al 2018), due to its elevated tolerance to iron concentrations in the substrate (Caldeira et al 2021), as has also been reported for other species of Paspalum (Figueiredo et al 2018;Oliveira de Araujo et al 2020).…”

“…In order to further assess the potential of P. cinerascens for revegetation purposes in Serra dos Carajás, in this study we evaluated the growth of this grass in the substrate remaining from iron ore extraction in different nutritional requirement scenarios. As the species shows high carbon assimilation in canga environments (Caldeira et al 2021), we expect that P. cinerascens seedlings can grow and thrive in the mining waste substrate with little fertilization requirements.…”