Invasion of the Brazilian campo rupestre by the exotic grass Melinis minutiflora is driven by the high soil N availability and changes in the N cycle.
The Serra do Rola Moça State Park (PESRM) in Minas Gerais State, Brazil is a preserved site representative of the campo rupestre biome over an ironstone outcrop that has a high level of plant diversity. Almost 60% of this grassy field has been invaded by the exotic molasses grass (Melinis minutiflora), which constitutes a severe threat to the biodiversity and survival of this biome, particularly due to the impacts of annual fires and inappropriate restoration interventions. Many invasive species exhibit a high demand for nitrogen (N). Hence, this work aimed to study the N cycle alterations promoted by M. minutiflora in a site of the campo rupestre, where the leguminous species Mimosa pogocephala was prevalent. The biome's soils exhibited a high natural N fertility and low C:N ratio. The main N source in this biome resulted from the biological N fixation performed by M. pogocephala associated with Burkholderia nodosa, as evidenced by the total leaf N content, leaf δ15N signature, nodule occupation and bacterial molecular identification analyses. The displacement of native species by molasses grass was associated with changes in the soil N forms, namely the nitrate increased as the ammonium decreased. The latter was the dominant N form in the native species plots, as observed in the soil analysis of total N, ammonium and nitrate contents. The dominant ammonium form was changed to the nitric form by the stimulation of ammonia-oxidising bacteria populations due to the invasive species. Therefore, the key mechanism behind the invasiveness of the exotic grass and the concomitant displacement of the native species may be associated with changes in the soil N chemical species. Based on this finding and on the high N-based soil fertility found in the campo rupestre N fertilisation procedures for restoration of invaded areas should be strictly avoided in this biome.
Departmento de Botânica - Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha, Belo Horizonte, Minas Gerais CEP 31270901, Brazil.
Pâmella C D
PC
Ribeiro
Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain.
Esther
E
Menendez
Departmento de Botânica - Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha, Belo Horizonte, Minas Gerais CEP 31270901, Brazil; Departmento de Microbiologia-Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha, Belo Horizonte, Minas Gerais CEP 31270901, Brazil.
Danielle L
DL
da Silva
Departmento de Microbiologia-Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha, Belo Horizonte, Minas Gerais CEP 31270901, Brazil.
Douglas
D
Bonieck
Instituto de Recursos Naturales y Agrobiología (IRNASA-CSIC), Cordel de Merinas 40-52, 37008 Salamanca, Spain.
Martha Helena
MH
Ramírez-Bahena
Departmento de Microbiologia-Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha, Belo Horizonte, Minas Gerais CEP 31270901, Brazil.
Maria Aparecida
MA
Resende-Stoianoff
Instituto de Recursos Naturales y Agrobiología (IRNASA-CSIC), Cordel de Merinas 40-52, 37008 Salamanca, Spain.
Alvaro
A
Peix
Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain.
Encarna
E
Velázquez
Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain.
Pedro F
PF
Mateos
Departmento de Botânica - Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha, Belo Horizonte, Minas Gerais CEP 31270901, Brazil. Electronic address: mritascottimuzzi@gmail.com.
Maria Rita
MR
Scotti
Ammonia monooxygenase (amoA); Ammonium; Biological nitrogen fixation; Burkholderia nodosa; Mimosa pogocephala; Nitrate