Shade tolerance of pasture species in relation to deciduous tree, temperate silvopastoral systems

Ten hill pasture selections, with an emphasis on cocksfoot (Dactylis glomerata L.) and perennial ryegrass (Lolium perenne L.), were evaluated for their potential to tolerate the shade conditions found in silvopastoral systems based on deciduous trees. The three experiments were on plants grown in pots in a glasshouse under varying levels of photosynthetic photon flux density (PPFD, 81 - 720 mumoles photons/m(2)/s) and red:far red ratio (R:FP, 0.57 - 1.34). The most productive selections in low PPFD had a high specific leaf area and tiller production that was relatively insensitive to the level of PPFD, and responded to decreased PPFD by increasing specific leaf area and the proportion of biomass allocated to leaf. The morphological responses of the pasture species to a decrease in R:FR ratio were small in comparison to the responses to low PPFD. The most shade tolerant selection in heavy shade (i.e., <25 % of ambient PPFD or approximately 200 mumoles photons/m(2)/s) was cocksfoot cv. Grasslands Wana due to its greater leaf area as a consequence of its high specific leaf area and the insensitivity of its tillering to low light.