Characteristics of jarrah (Eucalyptus marginata) forest at FORESTCHECK monitoring sites in south-west Western Australia: stand structure, litter, woody debris, soil and foliar nutrients

Abstract

Summary Species composition, size class distribution and developmental stage of canopy and mid-storey tree species were measured at 48 sampling grids in jarrah (Eucalyptus marginata) forest for the FORESTCHECK monitoring project. Other site attributes quantified at each grid included litter loading and coarse woody debris volume, and concentrations of N, P and K in surface soil and eucalypt foliage. Grids were located in stands treated to release regeneration by gap creation (n = 14), to establish regeneration by shelterwood harvesting (n = 12) and in stands where the outcome of harvesting was a selective cut (n = 3). Grids were also located in coupe buffers (n = 4) and in external reference forest (n =15) that had not been harvested since 1960, with eight grids having no record of previous harvesting or evidence of cut stumps. Live eucalypt basal area in external reference forest and coupe buffers averaged 41 m2 ha−1 (range 13–78 m2 ha−1), with marri (Corymbia calophylla) contributing more than half the basal area on some grids in the Jarrah South and Jarrah Blackwood Plateau ecosystems. On average, basal area was reduced by 14 m2 ha−1 to 17 m2 ha−1 in shelterwood stands and by a similar amount in selectively cut stands. Basal area was reduced by 22 m2 ha−1 to 9 m2 ha−1 in areas cut to gap release. Mature trees greater than 70 cm diameter were retained at a rate of six to seven per hectare in harvested stands. Basal area ingrowth following harvesting averaged 0.5 m2 ha−1 y−1 of jarrah and 0.3 m2 ha−1 y−1 of marri. Harvesting increased the volume of coarse woody debris, with the largest amounts present in stands cut to gap release. The volume of woody debris <250 mm in diameter was significantly less in external reference forest that had never been harvested than in shelterwood or gap release stands. Data collected during the initial 5 y of the FORESTCHECK project demonstrate that gap release treatment has resulted in fully stocked stands with a developing cohort of saplings. Shelterwood treatment has been applied conservatively with a tendency to retain more basal area than required by the silvicultural guidelines, and in areas that may already have had sufficient ground coppice to allow for satisfactorily regeneration by gap release. Shelterwood silviculture does not necessarily result in establishment of sufficient seedlings to satisfy regeneration stocking standards within 10 y of treatment, but further episodic recruitment following fire is expected to achieve this over the longer term.