Aim: In savannas, a grass-dominated ground layer is key to ecosystem function via grass-fire feedbacks that maintain open ecosystems. With woody encroachment, tree density increases, thereby decreasing light in the ground layer and potentially altering ecosystem function. We investigated how light availability can filter individual grass species distributions and whether different functional traits are associated with response to a shade gradient in a landscape experiencing woody encroachment. Location: Savanna-forest mosaic in the Cerrado domain, southeastern Brazil. Methods: Along an encroachment gradient of increasing tree leaf area index (LAI) and shade, we determined how changing light availability alters grass diversity and ground layer structure relative to grass cover and grass functional traits (photosynthetic pathway, underground storage organs, bud protection and traits related to grass shape, size and leaf dimensions). Results: Increasing shade led to a decrease in grass cover and grass species richness, and also compositional and functional changes. We found that where tree LAI reached 1, grass cover was reduced by 50% and species richness by 30%. While C 4 grass species abundances decreased with increasing shade, the opposite pattern was true for C 3 grasses. There were only small differences in light preferences among C 4 subtypes, with phosphoenolpyruvate carboxykinase (PCK) species tolerating slightly more shaded conditions. Persistence of some C 4 species under more shaded conditions was possible, likely due to an ability to store starch reserves via underground storage organs. Conclusions: Woody encroachment changes diversity and structure of the grassy layer that is critical to the functioning of savanna ecosystems, highlighting the dependence of the diverse grass layer on open and sunny conditions. Our results suggest a threshold of tree cover close to LAI ≈ 1 as being critical to cerrado grassy layer conservation.

SummaryThe genus Ziziphus (Rhamnaceae) is revised for Borneo. 13 species are recognised using morphological evidence, including three new endemic species: Ziziphus cuspidata, Z. domatiata and Z. puberula. Borneo is therefore the island with the greatest known diversity of Ziziphus species. The area surrounding Mount Kinabalu is particularly diverse, with nine species occurring in Ranau. Two new varieties of Z. borneensis are also described here, Z. borneensis var. ranggam and Z. borneensis var. velutina, five new synonyms are established, including the placement of Z. elmeri as a synonym of Colubrina beccariana. A taxonomic treatment, including a preliminary IUCN conservation status assessment, is presented for each species and variety.

Functional traits are a way to infer processes from pattern, and as such are used to disentangle the macroecology and biogeography of plant families (e.g., Onstein et al., 2019;Xue et al., 2020) and biomes (e.g., Gomes et al., 2020;Solofondranohatra et al., 2018), but only infrequently plant genera (although see Proches et al., 2012;Pezzini et al., 2021). As morpho-physio-phenological characters, functional traits relate to the life history strategies of plants that embody growth, reproduction, and survival (Violle et al., 2007) and indicate how species relate to the environment. Fruit traits have been used to interpret the fossil record and infer genus-level paleo-distribution