The effect of exotic grass Urochloa decumbens (Stapf) R.D.Webster (Poaceae) in the reduction of species richness and change of floristic composition of natural regeneration in the Floresta Nacional de Carajás, Brazil.

Leandro V Ferreira,Pia Parolin,Denise A Cunha,Priscilla P Chaves,Darley C.L Matos,Selvino O Neckel

doi:10.1590/0001-3765201620150121

Leandro V Ferreira, Pia Parolin + Show 4 more

Open Access

https://doi.org/10.1590/0001-3765201620150121

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Abstract

The introduction of exotic species is considered as one of the major causes of biodiversity loss. The National Forest of Carajás is one of the largest mineral provinces in the world. Mining activities caused changes of the natural habitats, leaving degraded areas after the mineral exploitation. One of the mining areas within FLONA Carajás was used for the extraction of gold. In the process of exploitation, a huge depression was formed by the removal of soil which was mounded up nearby. To prevent soil erosion of these mounds, an exotic grass, Urochloa decumbens (Stapf) R.D.Webster (Poaceae) was planted. The objective of this study was to compare the impact of this non-native grass on species richness and species composition of the natural regeneration in the degraded areas. Four areas were compared, two with and two without presence of U. decumbens. In each area, twenty four 1m²/plots were established. Species richness of the regeneration areas and population sizes were significantly lower in the plots where the exotic grass was present. Our study shows that U. decumbens had a negative effect on species richness and population density, and its presence changed the species composition and distribution of life forms of the natural regeneration.

Highlights

Mining activities imply some of the most serious forms of environmental degradation, because the extraction of ores causes the removal of vegetation and soil organic layers, leaving the area degraded (Salomão et al 2007)
In the present study we focus on the exotic grass U. decumbens which was deliberately introduced into the degraded sites of the National Forest of Carajás two decades ago
Thirty six species were inventoried in the plots dominated by U. decumbens and 103 species where U. decumbens was absent (Appendix SI - Supplementary Material)

Summary

Introduction

Mining activities imply some of the most serious forms of environmental degradation, because the extraction of ores causes the removal of vegetation and soil organic layers, leaving the area degraded (Salomão et al 2007). The main limiting factors for the establishment of plant species after the mining process are soil compaction and the scarcity of nutrients and organic matter in the remaining. Depending on the degree of environmental degradation, after the human impact, different processes and techniques of recovery can be chosen and different plant species may be employed for the restoration area (Salomão et al 2007). The main methods used for the recovery of degraded areas by mining include planting of grasses (Ray and Brown 1995), soil enrichment and/or cultivation of native or exotic tree species (Tilstone et al 1998). The recovery should begin with the planting of native pioneers, and finish with native climax species, with the goal of re-establishing a vegetation pattern as close as possible to the original matrix

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