Plant community and fine-root growth under preserved and passively restored Cerrado sites in southeast Brazil

This is the first study to use the minirhizotron technique to examine fine-root dynamics in preserved and restored Cerrado flora, providing novel insights into belowground processes critical to tropical savanna restoration worldwide. We compared preserved cerradão and neighboring 16-year-old passive restoration sites by surveying vegetation, monitoring fine-root growth over one year, and analyzing soil. We examined (i) vegetation structure and composition, (ii) seasonal fine-root growth patterns, (iii) whether restored root dynamics resemble the preserved site, and (iv) how root production relates to climate, soil properties, and ecosystem conditions. We assessed plant community traits, root length at 0-56 cm soil depth, meteorological parameters, and thirteen soil health indicators. The restoration's woody stratum differed markedly (Sørensen index = 0.368), with 44 % fewer individuals, 35 % fewer species, a more open canopy, persistent grass invasion, and higher presence of early-successional shrubs and trees. Both sites showed similar rainy-season root production, but the restoration produced 3.7-fold more root length in the dry season and 65 % higher annual root productivity. In the cerradão, root growth correlated positively with temperature, rainfall, solar radiation, and evapotranspiration (p < 0.05; r > 0.58), while correlations were insignificant in the restoration. Soil properties, including sum of bases, cation exchange capacity, and organic matter, were at least 35 % lower in the restoration, indicating inferior soil health. In conclusion, although increased fine-root growth may enhance carbon input and aid soil recovery in the 16-year-old restoration, plant structure, soil health, and root dynamics remain distinct from the preserved cerradão, suggesting that full convergence still requires considerable time.