Evaluating the demographic, reproductive, and genetic value of eucalypt paddock trees for woodland restoration in agricultural landscapes

Eucalypt woodlands have been extensively cleared in southern Australia for agricultural production and the scattered trees that remain (“paddock trees”) are at risk of extinction without conservation action to lift recruitment rates. Here we assessed the reproductive, demographic, and genetic structure of trees from two vegetation types (paddock vs. intact vegetation fragments) for each of two species of eucalypts to characterize post-clearance population structure and to evaluate paddock trees as seed sources for revegetation. Paddock trees of both species were structurally larger than trees in vegetation fragments, but seedlings and saplings were completely absent in paddocks due to ongoing agricultural land use. Eucalyptus leucoxylon paddock trees had high mortality, but overall paddock trees were not in poorer condition than fragment trees. E. leucoxylon paddock trees had lower reproductive output than trees in fragments, and Eucalyptus camaldulensis paddock trees had higher. Levels of genetic diversity of adult trees were very similar in the two vegetation types, and there was no genetic differentiation between paddock trees and remnant vegetation across our survey sites. These results suggest that paddock trees represent a potential source of seed to contribute to genetically diverse woodland restoration plantings, though further trials will be required to evaluate seedling survival on agriculturally modified land and under predicted future climate conditions.Kym M. Ottewell, Steve C. Donnellan, and David C. Pato