Using plant traits to assess restoration outcomes in a tropical grassland

The Brazilian Cerrado is a global biodiversity hotspot. Restoring this tropical grassy biome is critical to conserving nature and human well-being. Several Cerrado plant species can be re-established by restoration methods yet we lack an assessment of the functional outcomes of restored ecosystems. Here, we aimed to fill this knowledge gap by comparing the soil and traits of native and invasive plants between a 3-years-old restored site and an old-growth site in the Cerrado. We carry out this study in a (i) direct-seeding grassland restoration experiment and (ii) the nearest well-conserved grassland in Central Brazil (14°05’ S, 47°38’ W). In each study site, we measured soil conditions (fertility, acidity, moisture, and texture) and traits related to plant water-use (leaf minimum water potential, ?min; minimum conductance, gmin; and turgor-loss point, psi tlp) and productivity (plant height and leaf mass per area, LMA) of the dominant graminoid native and exotic species (Urochloa decumbens). The restored area had a lower concentration of aluminum, drier soils, and lower phosphorus and nitrogen levels. Traits related to drought tolerance (gmin and ?tlp) were significantly less variable in the restored community compared to the old-growth one. The restored grassland was dominated by species with traits associated with higher productivity (low LMA) and higher drought-sensitivity (high psi tlp) (e.g., U. decumbens) in contrast to the old-growth counterpart. Lower soil moisture in the restored area compared to the old-growth area can be explained by soil texture, while soil legacies from prior invasion and land management might have determined the differences in fertility between the sites. Recovering functional diversity and composition may rely on re-assembling a diverse set of species in mimicking the dominance-rarity structure of an old-growth Cerrado grassland. Moreover, re-invasion of the African grass U. decumbens in the restored site might be favored by the fast resource-use of this invasive species. Here we found that plant functional diversity following restoration is still very different from the reference community in the short-term. Future studies could address the effectiveness of restoring soil properties and an uneven abundance structure in steering restored ecosystems to a functionally-diverse and invasion-resistant state in the Cerrado biome. (AU)