DOI: 10.5061/dryad.b5mkkwhph
title: Data from: An enemy's enemy is an ally: Competitive indirect interactions mediate coexistence of trees, grasses, and subshrubs in Neotropical Savanna

description: Savannas are complex ecosystems where multiple growth forms, including
 grasses, trees, and subshrubs, coexist through intricate ecological
 interactions. Understanding the mechanisms that promote this coexistence
 is key to conserving savanna biodiversity. This study investigated the
 effects of grass competition on the survival and growth of trees and
 subshrubs, as well as the interactions between these two growth forms.
 Using three species of trees and three species of subshrubs, we conducted
 a greenhouse experiment to assess how competition between trees and
 subshrubs is influenced by the presence of grass. We found that grass
 competition significantly reduced the survival of tree seedlings, while
 subshrubs were unaffected. When trees and subshrubs competed directly,
 subshrub biomass was reduced, but only in the absence of grass. Tree
 seedling biomass was not affected by subshrubs, but was negatively
 impacted by grass in the absence of subshrubs. Both root and stem biomass
 of trees and subshrubs were reduced by grass competition; however, this
 effect was mitigated when grasses, subshrubs, and trees competed
 simultaneously. These results indicate that when grasses, subshrubs, and
 trees compete together, the intensity of competition is reduced, promoting
 coexistence and contributing to the balance of growth forms in savanna
 ecosystems. While fire is an important factor in savanna dynamics, our
 study emphasizes the critical role of competition in maintaining this
 balance. Future studies should explore how fire and competition interact
 to further our understanding of biodiversity and ecosystem function in
 Neotropical savannas.
description: <strong>Species selection, experimental design, and
 establishment</strong> To investigate the effects
 of a native grass on the growth of subshrubs and trees in Brazilian
 savanna, we selected three congeneric pairs representing these growth
 forms. We obtained seeds of the grass <em>Paspalum
 atratum</em> from the Brazilian Agricultural Research Corporation
 (Embrapa) and collected seeds for most congeneric pairs in Brasília,
 Distrito Federal, Brazil, with the exception of <em>Copaifera
 oblongifolia</em> and <em>Anacardium humile</em>, which
 were collected in Chapada Gaúcha and Grão Mogol, Minas Gerais,
 respectively, between November 2013 and July 2014. The factorial
 experiment involved the presence and absence of grass competition (G+;
 G-), congeneric competitor and without it (C+; C-) (Figure 1), and two
 growth forms, trees and subshrubs (T; S). For each species, there were 48
 replicates for each combination of grass and congener treatments. We sowed
 the seeds in polyethylene sacks with a diameter of 20 cm and a depth of 40
 cm. The grass was sown five months before the other species in February
 2014 to ensure its establishment (Figure 1). To avoid shading by grasses
 on individuals assigned to the grass-free treatment, plants in the G+ and
 G- treatments were arranged into separate groups. We broke the physical
 dormancy of <em>Stryphnodendron</em> seeds by immersing them
 in sulfuric acid for 5 minutes. The substrate for all plants was 70%
 oxisol subsoil from a site previously occupied by savanna (40 cm deep or
 more) mixed with 30% washed sand, without any added nutrients. The
 experiment was conducted in a greenhouse with an automatic irrigation
 system that provided approximately 7 mm of water per day.
 <strong>Data collection and statistical
 analysis</strong> After one year, we collected
 the biomass from six replicate plants from each combination of factors.
 The subshrubs and trees were separated into shoots and roots, dried in a
 drying chamber at 70°C for 72 hours, and weighed on a precision scale
 (0.0001 g). The remaining plants were used to quantify survival; after 1.5
 years, we counted all living plants in each sack to determine if
 competition from grass and/or congeners affected the survival of trees and
 subshrubs.
description: # An enemy's enemy is an ally: Competitive indirect interactions
 mediate coexistence of trees, grasses, and subshrubs in neotropical
 Savanna
 [https://doi.org/10.5061/dryad.b5mkkwhph](https://doi.org/10.5061/dryad.b5mkkwhph) **Description of the data and file structure** **Species selection, experimental design, and establishment** To investigate the effects of a native grass on the growth of subshrubs and trees in Brazilian savanna, we selected three congeneric pairs representing these growth forms. We obtained seeds of the grass *Paspalum atratum* from the Brazilian Agricultural Research Corporation (Embrapa) and collected seeds for most congeneric pairs in Brasília, Distrito Federal, Brazil, with the exception of *Copaifera oblongifolia* and *Anacardium humile*, which were collected in Chapada Gaúcha and Grão Mogol, Minas Gerais, respectively, between November 2013 and July 2014. The factorial experiment involved the presence and absence of grass competition (G+; G-), congeneric competitor and without it (C+; C-), and two growth forms, trees and subshrubs (T; S). For each species, there were 48 replicates for each combination of grass and congener treatments. We sowed the seeds in polyethylene sacks with a diameter of 20 cm and a depth of 40 cm. The grass was sown five months before the other species in February 2014 to ensure its establishment (Figure 1). To avoid shading by grasses on individuals assigned to the grass-free treatment, plants in the G+ and G- treatments were arranged into separate groups. We broke the physical dormancy of *Stryphnodendron* seeds by immersing them in sulfuric acid for 5 minutes. The substrate for all plants was 70% oxisol subsoil from a site previously occupied by savanna (40 cm deep or more) mixed with 30% washed sand, without any added nutrients. The experiment was conducted in a greenhouse with an automatic irrigation system that provided approximately 7 mm of water per day. **Data collection and statistical analysis** After one year, we collected the biomass from six replicate plants from each combination of factors. The subshrubs and trees were separated into shoots and roots, dried in a drying chamber at 70°C for 72 hours, and weighed on a precision scale (0.0001 g). The remaining plants were used to quantify survival; after 1.5 years, we counted all living plants in each sack to determine if competition from grass and/or congeners affected the survival of trees and subshrubs. ### Files and variables #### File: Data_Manuscript.xlsx **Description:** The dataset includes survival and biomass variables for six species grouped into three congeneric pairs. It is organized into two separate sheets: 1. **Sheet "Survive":** This sheet presents survival data from each block, separated by species. Survival was measured under four conditions: with and without the presence of a congeneric competitor and with and without the presence of grass (*Paspalum*). Additionally, the growth form of each species is specified (Tree or Subshrub). 2. **Sheet "Biomass":** This sheet records biomass-related variables for the same six species, focusing on individual-level data rather than survival. The data includes measures of root, shoot, and total biomass, as well as the root-to-shoot ratio. The conditions of competition and growth form are also recorded. **Variables:** * **Sheet "Survive":** * **Species**: Species identifier * **Genus**: Genus identifier * **Grass**: Presence or absence of grass (*Paspalum*) (G+ = Present, G- = Absent) * **Competition**: Presence or absence of congeneric pair competitor (C+ = Present, C- = Absent) * **Life Form**: Growth form of the species (Tree vs. Subshrub) * **Success**: Number of individuals that survived * **Fail**: Number of individuals that did not survive * **Total**: Total number of individuals assessed * **Survive (%)**: Survival percentage * **Sheet "Biomass":** * **Genus**: Genus identifier * **Life Form**: Growth form (Tree vs. Subshrub) * **Species**: Species identifier * **Grass**: Presence or absence of grass (*Paspalum*) * **Competition**: Presence or absence of congeneric pair competitor * **Combine**: Combined presence of grass and competition conditions * **Root Biomass**: Biomass of the root component * **Shoot Biomass**: Biomass of the shoot component * **Plant Biomass**: Total biomass of the plant * **Root Shoot Ratio**: Ratio of root biomass to shoot biomass