Invasive potential of the winter grass Schismus barbatus during the winter season of a predominantly summer-rainfall desert in Central-Northern Monte

Winter establishment of the alien annual Schismus barbatus is not affected by insect herbivory in Northern-Central Monte Desert

“…In a previous study of the non-dormant soil seed bank of S. barbatus in a similar site of the Northern-Central Monte, Pucheta et al (2011) found more than 30 000 germinable seeds m À2 (ranging from 2672 to 128 260 seeds m À2 ) in samples collected just before the emergence seedlings observed in this study (March 2006). Hence, seedling recruitment in the field represented roughly half of the estimated non-dormant seed bank.…”

“…However, in a study by Shiponeni and Milton (2006) in a semiarid African fynbos ecosystem, S. barbatus has been found to be dispersed in wildebeest dung, suggesting their occasional consumption. Moreover, low-mass seeds, as those in Schismus (420e435 mm length) may not be consumed by the large-sized ant A. lobicornis, resulting in a high density seed bank (Pucheta et al, 2011).…”

“…Moreover, rainfall conditions for plant recruitment and reproduction similar to the ones observed during the study year had occurred several times in the recent past at the study site. It could be argued that S. barbatus success is expected to be low given the predominantly summer rainfall regime and the low rainfall amounts for April and May, the time when the number of non-dormant seeds of S. barbatus reaches its maximum (Pucheta et al, 2011). However, inspecting a period of thirty years (1979e2008), we found that cool season rainfall above the 10 mm threshold for Schismus germination (Gutterman, 1994), were met seven times in April (1979April ( , 1981April ( , 1992April ( , 1999April ( , 2000April ( , 2003April ( and 2007 and three times in May (1987, 2000 and 2004), suggesting that this non-indigenous plant species have had the opportunity to establish a self-maintained population once they have arrived as a seed in a recent past.…”

“…barbatus is a winter annual grass native to the Mediterranean region that has mostly colonized deserts where rainfall concentrates during winter (e.g., Sonora, Austral Monte) (Brooks, 2000;Morici et al, 2006). However, S. barbatus has been recently observed during the cool season in a Northern-Central Monte Desert, where rainfall concentrates during summer (Pucheta et al, 2011). In spite of the very low frequency of winter rainfall in this area, this non-indigenous plant species has a large non-dormant soil seed bank (>30 000 germinable seeds/m 2 , Pucheta et al, 2011) and can germinate as soon as five to seven days after small pulses (w15 to 20 mm) of late-summer or early-autumn rains, often coexisting with low densities of native plant species (pers.…”

Invasiveness of Cut-Leaf Ground-Cherry (Physalis angulata L.) Populations and Impact of Soil Water and Nutrient Availability

“…Seed germination of invasive or other alien species is one of the main factors that defines their spread and invasion potential, and it is therefore extensively studied (Travlos et al, 2007;Pucheta et al, 2011). Seed germination aspects of P. angulata have already been studied, and it has been reported that cut-leaf groundcherry seeds were less sensitive than seeds of other species to simulated moisture stress (Thomson and Witt, 1987).…”