VEGETATION MANAGEMENT PLAN for Bidjigal Reserve - Land

Vegetation Management Plan - Bidjigal ReserveCRITERION BACKGROUND METHODOLOGY FOR FIELD RANKING LIMITATIONSThe following disturbance types were recorded if they occurred in at least10% of the boundary:• Physical disturbance of soil• Imported fill soils• Dumped garden refuse• Physical disturbance of vegetation• Stormwater runoff/drainage impactsDisturbances in CoreLevel of Management Assessment: ZoneThis criterion is discussed in the previous section (disturbance onedges/boundaries). However, as core disturbance has serious implicationsfor resource allocation and for on-going management, core disturbance hasbeen weighted accordingly.As above, but in remainder of zone (i.e. all areas not within 10 metres ofthe boundary)As aboveWeed Population CharacteristicsNoxious WeedsLevel of Management Assessment: UnitAs a public authority, the land manager (the Trust) has a legal obligation tocontrol noxious weeds on lands under its care and control.Therefore, high priority was given to sites with a large number and/ordistribution of noxious weeds.The occurrence and density of weeds listed as noxious in the HawkesburyCounty Council (listed in Appendix 6 and 7) was recorded for eachManagement Unit during the field survey.Environmental WeedsLevel of Management Assessment: UnitEnvironmental 9 weeds threaten the health of bushland (including those inadjacent privately owned bushland) because of their propensity to spreadwidely and rapidly in bushland.Therefore, high priority was given to sites with a higher number and/ordistribution of environmental weeds.The cover (High, Medium or Low) of species considered to beenvironmental weeds was estimated for each Management Unit duringthe field survey.Noxious weeds and Weeds of National Significance (WONS) are alsoconsidered environmental weeds and therefore they have beenincorporated into this criterion.The estimates of cover were given an individual weighting for priorityassessment (see below):• Number present with a low percentage cover = 1• Number present with a medium percentage cover = 2• Number present with a high percentage cover = 3Difficulty in estimating cover, particularly in large sites, and sites with morethan one (1) environmental weed species.The cover of environmental weed was highly variable within sites, whichprobably caused some errors in estimates. Large ranges of percentages foreach score limited the implications of such errors. However sites with acover estimated to be close to a percentage threshold may have beenassigned an inaccurate score.Observer bias may have caused errors in score designation as this criterionwas based on a visual estimate only. However, this error was expected tohave been largely overcome by the same observer consistently recordingdata for all field survey sites.Condition of BushlandLevel of Management Assessment: UnitCondition (or health) of bushland is an important factor to consider whendetermining works priorities as site resilience (as determined by the numberof native plants remaining on a site) will determine the likelihood of success.Priority is generally given to areas in good condition because of factors suchas ease of restoration (i.e. natural regeneration vs. planting) which impactson the cost effectiveness of the program, and the obvious need to protectthe healthiest, most diverse areas of bushland.The condition of bushland was determined from the mapping componentof this project. This is shown in Figures 3.2. Management Units wereassessed using the Ku-ring-gai Municipal Council (KMC) method andsubsequent weightings used to indicate the bushland condition. Thesefigures were allocated a ranking for priority assessment (see below).Figures in brackets represent KMC calculated weed class value.1) No weed management issues (1)2) Low infestation - mostly confined to lower layer and moderatepercentage in mid layer. No weeds in upper layer (1.3)Ku-ring-gai Municipal Council (KMC) Condition of bushland assessment isbased on a ‘three-layer’ vegetation structure which sometimes does notconform with structure of the vegetation being assessed.9 An environmental weed is a non-indigenous plant which is capable of modifying the ecosystem which it invades, usually to the detriment of the native flora and fauna.UBM Ecological Consultants Pty Ltd 40