THE EFFECT OF MICROSITE VARIATION ON SEED-GERMINATION AND SEEDLING SURVIVAL OF EUCALYPTUS-DELEGATENSIS

The correlation between microsite and seedling numbers was determined in field sowings, and the impact of microsites on germination and seedling survival tested in artificial seedbeds in the glasshouse. Small scale variation in soil conditions, at the scale of tens of centimetres, markedly affected the germination and establishment of Eucalyptus delegatensis R.T.Baker seeds and seedlings. Under conditions of limiting soil moisture, microsites that afforded protection, and probably resulted in increased humidity, caused a marked increase in germination number and rate. The mean survival time was significantly higher on these protected microsites than on less protected microsites, or on microsites that restricted root penetration. The importance of this variability in microtopography was strongly influenced by season and the level of environmental stress, and was diminished as seedlings aged. Due to the different requirements for seed germination and seedling growth, a favourable microsite for germination was not necessarily a favourable site for seedling survival. A comparison of seed and seedling responses to water stress indicated that for E. delegatensis, at least, selection due to microsite differences at the time of germination may not have an impact on the developmental characteristics of the seedlings.