Willow Sawfly Management Trials - Weeds Australia

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Willow Sawfly Management Trials - Weeds Australia

20B) BrowsingAt both Happy Valley and Campaspe River browsing by feral animals, probably a combinationof deer, rabbits, hares and wallabies, was the major limiting factor preventing plant growth. Sodespite the exclusion domestic stock, restoration of the native riparian community was hamperedby the activities of these animals.A cycle of browsing, regrowth, browsing and more regrowth was obvious on the majority ofseedlings at both these sites, with all species affected to some extent. Tree heights for a numberof seedlings corresponded with the top of the tree guards, with any growth that emerged abovethe tree guard being consumed. There was also some browsing of plant matter lower down,within the tree guards.At Happy Valley, the browsing pressure lessened in the latter half of the 2009/10 season,possibly because there were high levels of other feed available after good spring rains. Thisallowed the plants at this site to grow beyond the height of the tree guards. However, it ispossible that this new growth will be browsed over coming months.This situation raises several interesting questions. The first of these relates to the use of treeguards, particularly at sites where relatively few seedlings are planted. At both Happy Valley andCampaspe River, only about 200 seedlings were planted into a landscape devoid of seedlings,which would be insufficient to satiate the appetites of the local herbivore populations. Althoughtree guards do provide a level of protection against browsing, they also draw attention to theplants and it is possible that their presence highlights the locality of browse to the animals. Thelack of tree guards on the additional seedlings at Campaspe River planted outside the trial plots,and their location within dense grass, may have provided these seedlings with protection frombrowsing.It is also possible that the cycle of browsing, regrowth and browsing again encourages the strongdevelopment of below-ground tissues in the affected seedlings, so that if browsing pressure isreleased, the seedlings can quickly attain greater above-ground growth from the resources storedin the root system.There are some possible options to overcome browsing at sites with high levels of herbivores,such as investing in animal-proof fencing or bait deterrents. These options can be expensive, butmay be the only solutions at some sites until plants are established. It is also possible that stagedreplanting would alleviate some of the pressure, with less palatable species being initiallyestablished at a site. At some sites, avoiding the use of tree guards may be beneficial, whileexperimenting with a range of different types of guards can help determine which give the bestprotection at a site.

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