Competitive Strategies and Growth of NeighbouringBromus valdivianusPhil. andLolium perenneL. Plants Under Water Restriction

Abstract

AbstractOften perennial pastures have to tolerate soil water restriction during summer, which can affect the relative abundance of the most desired species. In the south of Chile,Bromus valdivianusandLolium perenneare preferred species. The competitiveness ofB. valdivianusandL. perennewas evaluated when sown in pots in a glasshouse as monocultures or a mix (50/50 %) with restricted water availability. The water restriction treatments were as follows: 80–85 % field capacity (FC), 45–50 %FCand 20–25 %FC, maintained for 1196 growing degree days. For both species, dry matter (DM) accumulated per plant and per pot decreased similarly with increasing water restriction, but at tiller level, resource allocation differed, forB. valdivianusroot growth was accentuated over aerial development, but this was less so forL. perenne. The foliage mass per tiller forB. valdivianusdecreased relatively more than that forL. perennewith increasing water restriction. As monocultures,B. valdivianusproduced larger tillers thanL. perenne, such thatB. valdivianustillers had 2.2 times greater lamina mass, 3.6 times more leaf area and 2.5 times greater root mass than those ofL. perenne. However,L. perenneproduced a larger number of smaller tillers that enabled foliage, root and total mass at plant level, to be similar to that ofB. valdivianus. Within the mixed pasture,L. perennetiller density increased compared with when grown as a monoculture, but not forB. valdivianus. The results of the study suggested thatL. perenneandB. valdivianushave differences in growth strategies that allow them to survive under environmental stress and competition. Competitiveness increased forL. perenneaboveground without water restriction and that forB. valdivianusincreased belowground as water restriction was increased.