Germination ecology of Central Asian Stipa spp: differences among species, seed provenances, and the importance of field studies

Abstract

Stipa-species are wide-spread in Central Asia, but sexual reproduction in the dry steppes is rare. To facilitate conservation and restoration of these important rangelands, we studied germination characteristics of three common Mongolian Stipaspecies under field-and lab conditions. Seeds of Stipa krylovii, Stipa gobica and Stipa glareosa were sown at the study site in Southern Mongolia over two consecutive years during which period tests were carried out to ascertain whether competition or herbivory are the main constraints of seedling establishment. In addition, we tested germination and seed viability in the laboratory under two different temperature regimes (20/10°C and 8/4°C), as well as the effect of cold-stratification. The lab experiments also included S. krylovii seeds originating from three climatically different provenances. None of the three Stipa-species seedlings emerged during the first 2 years of the field study. However, after an unusually intense rain event in the third year, 3% of S. krylovii, 0.6% of S. glareosa and 0.1% of S. gobica seeds germinated in the study plots. The factors 'sowing-year' and 'vegetation' significantly affected seedling emergence, whereas grazing had no effect at all. Under laboratory conditions a high percentage of viable seeds of S. gobica and S. glareosa germinated at both incubation temperatures, and cold-stratification had no effect on germination or viability. Germination of S. krylovii seeds required warmer temperatures and cold-stratification had a positive effect. Such evidence for dormancy was more pronounced in seeds from the moister, northern provenances. Germination of Stipa-species in the field is rare and only possible under exceptionally moist conditions. Conservation should thus concentrate on steppe conservation rather than on restoration. Where artificial reseeding is necessary, differences among species and also among different seed provenances should be taken into account.

Effects of fertilization and irrigation on productivity, plant nutrient contents and soil nutrients in southern Mongolia

“…Given that our artificial irrigation did not improve plant vigour, most of the natural rain events with a median of 2.3 mm will also have very little effects on steppe productivity. This underlines the importance of distribution and intensity of rainy events, which has been repeatedly shown in drylands (Fisher et al 1988;Fravolini et al 2005;Patrick et al 2009) and also for reproduction of Stipa species in our area (Ronnenberg et al 2008).…”

“…In less severe conditions, plants are more likely to invest in aboveground vegetation and reproductive output, as opposed to mere persistence in leaner times (Peck et al 1998). However, in the Gobi, sexual reproduction is generally very restricted and depends on erratic rainstorms (Song et al 2002;Ronnenberg et al 2008). Effects of fertilization on resource allocation to belowground biomass or to reproductive organs have, hitherto hardly been studied in southern Mongolian drylands.…”

Trees in the desert: Reproduction and genetic structure of fragmented Ulmus pumila forests in Mongolian drylands

“…Such suitable climate conditions by no means occur every year, but recruitment should be theoretically possible. Rare events of recruitment are typical for most of the long-lived plants of the Gobi (Gunin et al, 2003;Ronnenberg et al, 2008). Thus, elm stands cannot be seen as remnant (Eriksson, 1996) in the sense that they simply persist vegetatively through the current climatic conditions, and merely represent relics of former more suitable climates.…”

Local adaptation to different phytogeographic regions: habitat‐related variations in seed germination in response to temperature and salinity for two medicinalSalviaspecies fromJordan

“…Furthermore, it can provide clues to a species’ survival strategy with respect to seed dormancy, pretreatments, optimal conditions for seed germination and the influence of seed provenance (Baskin & Baskin ; Ronnenberg et al . ; Hamasha & Hensen ). The study of seed germination behavior has provided the data required for developing and implementing effective strategies and protocols for the ex situ and in situ conservation of, for example, Arabis kennedyae (Andreou et al .…”