Establishment of perennial shrub and tree species in degraded Eucalyptus salmonophloia (Salmon gum) remnant woodlands: Effects of restoration treatments

Woodlands dominated by Eucalyptus salmonophloia (salmon gum) occur througho ut the fragmented landscape of the southwestern Australian wheatbelt. These remnants are often degraded by livestock grazing and weed invasion and in many cases there is little or no understorey remaining and little or no reg eneration of the dominant tree E. salmonophloia. There is a growing interes t in developing techniques for restoring remnant woodlands. This study desc ribes techniques for establishing seedlings of the dominant tree and perenn ial understorey species in E. salmonophloia (salmon gum) woodlands degraded by livestock grazing. The study tests the hypothesis that, in addition to the exclusion of livestock, management of weeds and reintroduction of plant species, restoration of plant species diversity will require techniques wh ich mimic large-scale disturbances, reduce soil compaction, and restore soi l water infiltration to suitable rates. Five-month-old seedlings of the dom inant tree E. salmonophloia and four commonly associated woody shrubs (Acac ia hemiteles, Atriplex semibaccata, Maireana brevifolia, and Melaleuca paup eriflora) were planted into areas that differed with respect to grazing (-r abbit/-livestock and +rabbit/-livestock), tree canopy disturbance (+/-compe tition with tree canopy) and amelioration of soil compaction (+/-deep rippi ng). Following three growing seasons and two summers, the exclusion of rabb its had no significant effect on the survival and growth of planted species . As a consequence grazing treatments are pooled for the purposes of presen ting the impacts of removing competition with adult trees and soil deep rip ping. The removal of competition with adult E. salmonophloia trees signific antly improved the survival of E. salmonophloia seedlings but did not impro ve survival of understorey species. Deep ripping the soil significantly imp roved the survival of both E. salmonophloia and the shrub A. hemiteles but did not improve the survival of other understorey species. In contrast to s eedling survival, the removal of adult E. salmonophloia trees and deep ripp ing soil significantly increased the growth of all species. The results ind icate that increasing levels of intervention will increase the chances of s uccessfully restoring tree and understorey species diversity in degraded E. salmonophloia woodlands.