Eucalypt establishment in agricultural landscapes and implications for landscape-scale restoration

In south-eastern Australia large-scale re-establishment of woody vegetation is required to halt loss of biodiversity, land degradation and dryland salinisation. Revegetation is often undertaken via intensive replanting by tube-stock or seed although such methods are costly and can have limited biodiversity benefits. Regeneration from naturally dispersed seed is an alternative and cost-effective method of revegetation. Describing the relationships between broad-scale patterns of natural regeneration, landscape characteristics, climate and current and historical land use could assist in the development of regional revegetation strategies. In this paper we describe the results of a survey of eucalypt regeneration across 519 sites in grassy dry forests and grassy woodlands of central Victoria, Australia. Eucalypt regeneration was observed in 27% of all sites. The probability of eucalypt regeneration was reduced by intensive past land use (cultivation), regular livestock grazing, increasing distance to remnant trees and high cover of exotic annual vegetation. Even when these factors were taken into account, public land was predicted to have higher probabilities of supporting regeneration suggesting that a long-history of agriculture can limit future recruitment even when grazing is removed. Although the highest probability of regeneration was observed in ungrazed sites, regeneration also occurred under intermittent grazing regimes. Natural regeneration has potential to make considerable contributions to future tree cover in these landscapes. Scenario testing at three farms suggests that under current patterns of tree cover (2.7%), 40% of the total area has a high probability of supporting natural regeneration in the absence of livestock grazing. However, due to paddock tree decline this could be reduced to 18% of total farm area if no management action is taken in the next 30 years.