Conservation strategies rely on precise taxonomic delimitation, yet delineating species complexes remains challenging. Despite these difficulties, it is crucial to protect vulnerable complexes. We examined the Poidium complex, comprising five morphologically similar taxa that co-occur in the highland grasslands of northeast Rio Grande do Sul, Brazil. Our goals were to assess whether morphological characters distinguish taxa or groups within the complex, evaluate correlations with environmental and geographic patterns, and inform conservation priorities. Using uni- and multivariate analyses of morphometric and environmental data, we identified three main groups within the complex, each defined by distinctive palea and lemma surface traits. Quantitative spikelet and lemma characters significantly differentiate these groups, and environmental and morphometric variables help characterize subgroups within the clusters. The majority of subgroups are concentrated in Northeast Rio Grande do Sul. Our results support circumscribing Poidium juergensii as having only strigose lemmas and no infraspecific delimitation, as well as treating individuals with glabrous lemmas at the species level, as Poidium tricholepis sp. nov. In addition, we highlight the weak morphological distinction between Poidium calotheca and Poidium ambiguum in sympatric areas. This study underscores the uniqueness of the South Brazilian highland grasslands and the relevance of including species complexes in conservation efforts.

Although ecosystem management and restoration are known to enhance carbon storage, limited knowledge of ecosystem-specific soil organic carbon (SOC) stocks and processes hinders the development of climate-ready, biodiversity-focused policies. Baseline SOC stocks data for specific ecosystems is essential. This paper aims to: (i) examine SOC stock variability across major grassy ecosystems in Brazil and (ii) discuss data limitations and applications. We compiled the Grassland Synthesis Working Group dataset, which comprehensively aggregates SOC stocks data from published studies on main Brazil's grassy ecosystems. Our dataset results from systematic literature review and regional soil sampling datasets. The dataset provides spatially explicit SOC stocks, physical soil properties, and ancillary information from 182 studies (1996-2021) across 803 sites, spanning 35 degrees latitude and 28 degrees longitude. The dataset, structured in relational tables, reports soil C stocks and ancillary soil parameters at depths up to 100 cm. SOC stocks vary by grassy ecosystem types and sampling depth, with subtropical grasslands (Campos Gerais, South Brazilian highland grasslands, and Pampa) showing the highest SOC stocks across all depth layers (SOC 0-30 cm: 64.5-162.8 Mg C ha-1; SOC 0-100 cm: 137.6-224.7 Mg C ha-1). The tropical Cerrado and Amazon grassy ecosystems exhibit high SOC stocks, particularly in subsurface layers (SOC 0-30 cm: 53.6 and 38.3 Mg C ha-1; SOC 0-100 cm: 109.8 and 121.4 Mg C ha-1, respectively). Our data analysis shows high carbon stocks in natural/seminatural ecosystems, but some ecosystems are undersampled. The dataset on SOC stocks in grassy ecosystems could greatly aid Brazil's national greenhouse gas inventory.

Grasslands in the Campos Sulinos region are suffering rapid losses due to expansion of agricultural fields and exotic tree plantations, resulting in risks of losses of biodiversity and ecosystem services. In this chapter, we analyse the current contribution of the protected area to conservation of grasslands, discuss the role – and implementation problems – of Legal Reserves and Areas of Permanent Protection, as well as the need for adequate grassland management. Only 5% of the total area of southern Brazil is currently in protected areas, with biases in terms of spatial distribution and type of ecosystem protected: grasslands are under-represented. The Legal Reserve could be an interesting instrument to complement the protected area networks, but implementation at the moment is insufficient and there have been attempts to undermine the instrument in favour of agricultural expansion. Besides implementation of Legal Reserve and expanding the network of protected areas, it is important that grassland areas are properly managed, as they are disturbance-dependent ecosystems. Grazing, fire and mowing can be used in active management, depending on the ecological and socioeconomic context of a specific site, and creation of spatial and temporal heterogeneity seems especially interesting from a conservation perspective. We conclude that the role of grassland conservation for safeguarding essential ecosystem services should be further explored in future studies to advance in conservation.

Current distribution of C3 and C4 grasses is often explained by contrasting environmental conditions. Regions where C3 and C4 grasses coexist, as the Southeastern South America grasslands (SESA grasslands), provides an excellent opportunity to investigate the evolutionary imprints of grasses through clade distribution patterns. Here, we aimed to understand how ecological and evolutionary processes affect the phylogenetic diversity of grass communities along 666 sites located in a latitudinal gradient ranging from 26°S to 38°S in SESA grasslands (Argentina, Brazil, and Uruguay). We applied generalized linear models (GLM) to understand the role of the different environmental and historical drivers that shape the proportion of C3 grasses distribution in SESA grasslands. The effect of latitude on phylogenetic beta-diversity patterns among the vegetation surveys was evaluated through principal coordinates of phylogenetic structure. Contribution of C3 species increased southwards (R² = 0.40, P<0.001). C3 species are more likely to occur in colder areas with higher historical temperature stability, reflecting lineages that have specialized and radiated in cold environments (GLM results: R² = 0.37, P<0.01). Climatically stable areas are the coldest, while unstable areas include warmer habitats, which enabled colonization by C4 species. Regarding soil conditions, C3 grasses are more likely to occur in more fertile soils and with low capacity to retain water (GLM results: pseudo-R² = 0.37, P<0.01). We found that phylogeny has an important role as a structuring agent of grass communities across our study region, indicating turnover of grass lineages along the latitudinal gradient. Grass species found at the northern portion of the gradient belong mostly to the clade which contain both C4 and C3 species. At the southern part of the gradient, communities are dominated by grasses belonging to a C3-exclusive clade. The distribution of grass clades across the SESA grasslands is indicative of the environmental gradients found in this region between temperate and tropical zones, describing a climate space where disturbance driven feedbacks play a major role in maintaining open vegetation. Our results contribute to the understanding of ecological and evolutionary drivers of grass distribution in the region that up to now has been poorly described. 

Campos Sulinos grasslands have a long evolutionary history intertwined with fire and grazing: they are disturbance-dependent ecosystems. Disturbance, in this context, refers to events that remove plant biomass. In this chapter we explore the main types of disturbance, namely fire, grazing, and animal disturbance, and their influence on the vegetation composition, structure, and functioning of Campos Sulinos grasslands. Grasslands in the region can be classified into three major types: highland grassland, Pampa grasslands, and coastal grasslands, each with their specific environmental drivers and disturbance history. While disturbance in general is necessary for the maintenance of grasslands, different disturbance regimes result in different plant community structure and composition. High grazing level results in communities where prostrate species play an important role, while fire leads to dominance of tussock grasses. Intensity and frequency of disturbances drive species richness and community dynamics over space and time. A thorough understanding of the key drivers of change in subtropical and temperate grassland communities is critical to maintaining their high biodiversity and has practical implications for management and restoration.

Cortaderia selloana (Schult. & Schult. f.) Asch. & Graebn. (Pampas grass) is a perennial grass native to temperate and subtropical regions of South America. The species was introduced to western Europe for ornamental purposes during the nineteenth century, where it has become naturalized in anthropogenic and natural habitats, especially in sandy, open, and disturbed areas. Female plants of C. selloana produce thousands of seeds that are dispersed over long distances by wind and germinate readily. Its invasive success is also attributed to its ability to adapt and tolerate a wide range of environmental conditions, such as high salinity levels, long droughts, and soil chemical pollution. Cortaderia selloana usually invades human-disturbed habitats where it encounters little competition with other plants and high resource availability. However, the species can invade natural habitats, especially those with high light availability, causing biodiversity loss and changes in ecosystem functioning (e.g. alteration of succession and nutrient dynamics). The species may cause negative socio-economic impacts by reducing productivity of tree plantations, causing respiratory allergies, and decreasing the recreational value of invaded areas. Control costs are high due to the extensive root system that C. selloana develops and the high resprouting ability following physical damage. Although herbicides are effective control measures, their use is not allowed or is undesirable in all situations where the plant occurs (e.g. near riverbanks, natural protected sites). No biological control agents have been released on C. selloana to date, but the planthopper Sacchasydne subandina and the gall midge Spanolepis selloanae are promising targets.

Detailed alien species inventories are important to assess strategies for its management. We built a vascular alien plant specieslist from published papers available for the Río de la Plata grasslands (RPG). Species were described regarding their geographicorigin, life form, photosynthetic pathway (only Poaceae), human use, and invasion status according to legislation of Brazil,Argentina and Uruguay. Occurrence records were obtained from Global Biodiversity Information Facility and rasterized intogrid-cells of 10 arc minutes resolution.The alien flora of the RPG comprises 592 species, among which 317 are considered invasive and 275 naturalized. Alien species canbe sourced to all continents, although most species have their native range from Temperate Asia (n = 413), Africa (n = 382), andEurope (n = 362). Herbs are the most frequent life form (n = 332), followed by graminoids (n = 125) and trees (n = 72). However, 86%of alien tree species are invasive. Regarding invasive species, only 8 species are common to three countries. We registered 235 exclusive invasive species in Argentina, 40 in Brazil and 9 in Uruguay. Alien species richness was higher in areas closer to major cities.Even so, we highlight higher alien species richness in Argentina. There is no clear spatial pattern regarding geographical origin,reflecting favourable conditions for alien species from different ecological contexts in the region. Our results have implicationsfor long-term conservation management of native biodiversity. Efforts to control alien species should surpass political boundariesand encompass all ecological units of the RPG.

Our editorial introduces a Special Collection of scientific articles on current vegetation research in the most biodiverse of all biogeographic realms, the Neotropics. It contains nine scientific contributions dedicated to vegetation data, description and classification. Four research papers provide new vegetation classifications of important Neotropical biomes, namely the Arid Chaco in Argentina, Mexican temperate forests, and Andean wetlands in the Argentine Puna and southern Peru. Furthermore, one study provides a novel bioclimatic-vegetation classification approach applied to Mexican vegetation, while another proposes a new synthesis of the South American terrestrial biomes as geocomplexes. Finally, three vegetation databases are presented in the Special Collection: ArgVeg - Database of Central Argentina (GIVD ID: SA-AR-002), CACTUS - Vegetation database of the Dutch Caribbean Islands (GIVD ID: SA-00-004) and VegAndes: the vegetation database for the Latin American highlands (GIVD ID: SA-00-005). The Special Collection provides fundamental data and tools to better understand the diversity and complexity of Neotropical vegetation.