Can an invasive African grass affect carbon and nitrogen stocks in open habitats of the Brazilian Cerrado?

Considering the emergence of ecosystems dominated by invasive species, there is growing interest in estimating the effect of biological invasions in ecosystem processes and provision of services. African grasses are the most invasive plants in the Cerrado (Brazilian savanna), but their impact on C and N stocks is poorly known. We compared patterns of C and N stocks in the aboveground biomass, root biomass and soil in open Cerrado (campo sujo) sites, both uninvaded and invaded by the African grass Urochloa decumbens. In both sites we estimated the aboveground biomass of U. decumbens and native grasses, as well as the root biomass up to 50 cm. We obtained C and N contents in the soil, as well as C and N stocks, up to 1 m depth, and variation in soil δ13C and δ15N. Although invasion did not affect the aboveground biomass, it did affect belowground biomass, leading to higher C stock in fine roots and soil N content close to soil surface, as well as higher C content along the soil profile. C and N soil stocks, soil δ13C and δ15N values did not significantly differ between invaded and uninvaded site. Even a relatively low level of invasion by U. decumbens changed the root distribution pattern and increased C and N contents in the upper soil, which may promote ecosystem changes by altering nutrient dynamics. Although still preliminary, our study shows that dominance by U. decumbens can have severe effects in the Cerrado belowground environment.

New records and key to Poa (Pooideae, Poaceae) from the Flora of Southern Africa region and notes on taxa including a diclinous breeding system in Poa binata

Four species of Poa L. are newly reported for sub-Saharan Africa and southern Africa, Poa compressa L., P. iconia Azn., P. infirma Kunth and P. nemoralis L. This is the first report of P. iconia from Africa. Vouchers at PRE of P. bulbosa L. all belong to var. vivipara Koeler, those of P. iconia belong to var. iconia and the one of P. trivialis L. belongs to var. trivialis. Two subspecies are recognised in P. pratensis L.: subsp. irrigata (Lindm.) H.Lindb. and subsp. pratensis. We also designate a lectotype for P. iconia and second-step lectotype for P. leptoclada Hochst. ex A.Rich. and report the first recording of a diclinous breeding system in P. binata Nees. Our account updates the treatment in Identification Guide to Southern African Grasses (Fish et al. 2015) including a key to the taxa and notes on infrageneric taxonomy, DNA subtypes, ecology, chromosome numbers and breeding systems.

IMPACT OF CLIMATE CHANGE ON THE POTENTIAL DISTRIBUTION OF NATIVE AND INVASIVE GRASSES IN THE CERRADO

Biological invasion, mainly by African grasses, is one of the main threats to the Cerrado's biodiversity. The objective of this study was to elucidate the distribution patterns of the exotic grass Melinis minutiflora and the native grass Trichanthecium cyanescens, in order to verify the areas of potential occurrence of these species and, thus, to infer if their potential distribution will be affected by climate changes. Species occurrence data and ten uncorrelated climatic variables referring to the forecasts for the current period and future forecasts (2050 and 2070) were used for the analysis of the modeling. The models indicated the existence of environmental suitability, with AUCs above 0.8 (good) being observed in M. minutiflora and above 0.9 (excellent) in T. cyanescens. It is concluded that climate change may have negative impacts on the geographic distribution of these species, reducing the area of environmental suitability for them. In addition, the species studied have similar areas of potential distribution and regularly overlap, which can make M. minutiflora a threat to the conservation of T. cyanences, due to the invasion potential of the first.

Taxonomic novelties in Central African grasses (Poaceae), Paniceae 2

Background and aims – Within the framework of the renewed production of the Flore d’Afrique centrale, the grasses are being studied to accomplish their treatment. Taxonomic novelties, or other information not deemed appropriate in a Flora, are published in a series of separate papers of which this is the second.Methods – Standard herbarium techniques have been applied to material from BR, BRLU, GENT, P and WAG. Some types were studied through the JSTOR Global Plant facility.Key results – Novelties are presented for the genera Anthephora, Cenchrus (incl. Pennisetum) and Setaria. Three new combinations are made. Lectotypes are designated for five names. Ten names are treated as new synonyms of accepted species names, with explanations of the new taxonomic concepts applied.