Site preparation for Pinus establishment in south-eastern Queensland 1. Temporal changes in bulk density

Abstract

In south-eastern Queensland, Australia, standard site preparation practices used for Pinus plantation establishment are mounding (bedding) on poorly drained soils and blade cultivation (subsurface, wing rip) on well-drained soils. This paper reports the impacts of both site preparation treatments on soil bulk density over time. Following site preparation, the extent of bulk density reduction and the nature of bulk density consolidation was affected by soil type, soil depth and the site preparation technique used. On high strength, hardsetting soils, bulk density reductions from both mounding and blade cultivation persisted throughout the 28-month period, and contrasted with non-hardsetting soils in the plantation estate, which consolidated more rapidly and had higher bulk densities relative to precultivation levels for the period 4-28 months following site preparation. The studies reported in this paper were the first in south-eastern Queensland to investigate the impact of site preparation for Pinus establishment on the nature and longevity of bulk density reductions. Previously, plantation managers assumed that positive site preparation impacts would be relatively short-lived, and therefore developed a prudential policy of planting Pinus seedlings immediately following site preparation. For the soils studied, delays of 2-4 months, and perhaps up to 6 months, between site preparation and planting would not compromise Pinus growth, but would assist management planning.