Environmental factors that limit Stipa tenacissima L. germination and establishment in Mediterranean arid ecosystems in a climate variability context

Abstract

In a climate variability context, knowledge about Alpha grass (Stipa tenacissima) seed germination and seedling establishment requirements is a key factor given the relevance of this species in wide areas of North Africa and southern Europe. Such knowledge can help to collect information about current S. tenacissima populations allowing the conservation and restoration in these ecosystems. According to this objective, we conducted a series of laboratory studies to investigate the effects of several ecological factors as temperature, light, salinity, burial depth and drought, in relation to germination capacity and development of new seedlings. The main results revealed that germination was delayed with increasing drought conditions generated by osmotic solutions. Seeds germinated at all the concentrations of NaCl solutions, but germination was completely inhibited at a PEG 6000 solution of −1.6 MPa. Further, an osmotic potential of −0.8 MPa inhibited root and shoot growth. Variations in temperature also promoted variable germination rates (GR50). The base germination temperature (Tb (50)) was less than 2 °C for the different osmotic potentials. Burial depth was another limiting factor required for establishment. Despite significant seed production, this study has identified several key limiting points affecting seed germination and seedling establishment which can affect the viability of their populations in the near future.