DOI: 10.5061/dryad.05qfttf6v
title: Challenges and directions for open ecosystems biodiversity restoration: An overview of the techniques applied for Cerrado

description: 1. Ecological restoration of tropical open ecosystems remains challenging
 for both science and practice. Over the last decade, innovative techniques
 have been developed, but whether they have been successful or not remains
 to be demonstrated. Assessing the outcomes of these initiatives is crucial
 to drive the following steps to improve tropical grasslands and savanna
 restoration. 2. Analyzing 82 data sets from the literature and primary
 data collection, we assessed the effectiveness of passive and active
 restoration techniques applied in Cerrado open ecosystems. We used plant
 diversity variables (species and growth forms) as indicators, considering
 ruderals and exotics as non-target species. Specifically, we aimed to
 answer: (i) How does the diversity of target species change through time
 in areas subject to passive restoration? (ii) Are active and passive
 restoration techniques effective in restoring the proportion of target
 species found in old-growth reference ecosystems? (iii) Have the current
 techniques been successful in recovering the proportions of growth forms
 of reference ecosystems? 3. We found that target species proportions do
 not increase with time, suggesting limitations of typical species to
 colonize degraded sites. Hence, passive restoration will promote the
 conservation of a limited and constant number of target species. This
 number will depend on the magnitude of degradation and previous land use.
 4. The restoration techniques currently applied to restore the
 biodiversity of Cerrado open ecosystems are not reaching the reference
 standards, with distinct techniques driving plant communities to different
 sets of growth forms. Active restoration based on propagules obtained from
 pristine donor sites (topsoil translocation, plant material transplant,
 and seeding) performed better than passive restoration for most of the
 growth forms analyzed. 5. Synthesis and Applications: Different growth
 forms have different roles in determining the structure and functioning of
 Cerrado vegetation. A mix of techniques can better approximate plant
 diversity and the proportionality of target species of pristine
 ecosystems. Singular restoration approaches are insufficient for restoring
 Cerrado open ecosystem biodiversity. Mixed efforts encompassing various
 techniques are required instead. Furthermore, it is likely restoration
 success can be improved with greater investment in improving our
 understanding of and developing existing restoration techniques.
description: <em>Literature
 review:</em> We surveyed published articles and theses
 addressing different restoration techniques for open Cerrado vegetation in
 the databases available (Scopus, Web of Science, ScienceDirect, PubMed,
 Google Scholar). To be incorporated into our database, the following
 criteria were applied: (i) restoration was performed in areas that were
 open ecosystems (cerrado grasslands or open savannas) before land
 conversion or degradation occurred, (ii) the study presents at least a
 list of species introduced, and (iii) describes the site history and the
 restoration technique in sufficient detail. Techniques were excluded from
 the analysis if they were not applied in at least three separate study
 areas. Sites originally occupied by rupestrian and wet grasslands were
 also not included. Several studies collected data in the same restoration
 area, therefore, we did not consider more than one publication about the
 same restoration initiative. Details for each data set considered here are
 presented in Table S1 in the original paper. A lack of standardized
 sampling procedures among studies turned impossible to compare changes in
 plant community structure (e.g. ground cover, biomass or even species
 richness). Instead, we analyzed community composition in terms of species
 and growth forms, which could be obtained from a majority of the studies
 and is a good surrogate for vegetation structure and diversity. 
 <em>Data collection in
 the field</em>: Studies presenting data from reference
 ecosystems or control plots were rare. Consequently, to assess restoration
 success relative to a reference ecosystem for these studies we sampled
 several pristine Cerrado open ecosystems representing the regions where
 the restoration interventions were implemented (see Figure S1). We,
 therefore, assumed that the proportions of target species and growth forms
 follow standards for conserved open ecosystems in the Cerrado and would
 provide a reliable comparison. Data collection for the 13 conserved areas
 was performed in four Brazilian States (São Paulo, Paraná, Mato Grosso do
 Sul and Goiás) across the Cerrado ecoregion  (Figure S1 and Table S1). We
 selected natural remnants free from exotic species and other sources of
 degradation; all areas were characterized as cerrado grassland
 (<em>campo cerrado</em>) – dominated by a rich herbaceous
 ground layer with few scattered shrubs and trees, with &lt; 20% canopy
 cover. We focused on areas with &lt; 20% canopy cover because these
 ecosystems are the most threatened and the hardest to recover (Durigan
 & Ratter 2006; Pilon et al., 2018, 2019).
 For the restoration techniques
 to be sampled in the field, we selected: (i) two areas subject to direct
 seeding in 2016 and 2018 in the National Park of Chapada dos Veadeiros
 (PNCV, at Goías state); (ii) one area restored by grass tussock
 transplanting at Santa Ecological Station (EEcSB, at São Paulo state); and
 (iii) two areas where passive restoration has been conducted after
 eradication of former pine plantation at EEcSB and Ecological Station of
 Itirapina (also in São Paulo state) (Table S1). In each area, restoration
 sites and in undisturbed open ecosystems in the Cerrado, we performed a
 floristic characterization following the “quick survey” method.
 This method consists in
 carrying out at least three walks in a straight line across the vegetation
 500 m apart from each other, sampling during regular time intervals the
 floristic composition (see details Walter & Guarino 2006). The
 walks were performed in homogeneous vegetation patches, and in our sites,
 up to three straight-line walks were necessary. In each straight line,
 sampling stopped when less than five species were added in two consecutive
 intervals of 15 minutes. The species lists for areas in
 natural regeneration after eucalypt plantation were obtained from 19
 former eucalypt stands, differing in the time lag since eucalypt
 clearcutting (unpublished data) (Table S1 – from the paper). In October
 2019, permanent plots were established in each area (221 plots in total,
 of 25 m x 4 m), resulting in 19 lists of plant species (all growth forms
 included). In addition, three unpublished lists from abandoned pastures of
 different ages were also added to our data set, collected in 15 permanent
 plots of 25 m x 4 m (details Table S1).