7.1 Soils of 50 ha CTFS LTER plot and upper catchment of Conrad Creek

The 50 ha LTER plot was sited so as to minimise abiotic environmental variation (Harms, 2001).  It is located in the centre of the andesite dipslope, and is as topographically and geologically homogeneous as is possible for an area of 1 x 0.5 km on BCI.  The plot covers most of the upper catchment of Conrad Creek, which was the kaolinite watershed in the geo-hydro-chemical study of Johnsson & Stallard (1989).

Most of plot is flat or gently sloping, with minor scarp slopes along the eastern boundary and even slighter slopes in the northwestern corner.   The principal interruption to the main surface is the shallow valley of upper Conrad Creek and its swamp in the centre of the plateau.

Because the plot is kept as inviolate as possible, we examined the soils only in augerings and took no samples.  We characterised and sampled the soils in more detail in profile pits just outside the plot border (Figure 7.1).  In a separate study, topsoils have been sampled at 300 points within the plot and analysed for Mehlich-extractable nutrients (John et al., 2007). 
Soil variation is limited, with Ava red light clays covering 72% of the plot.  They typical Ava, with deep, bright and unmottled red sola and silty clay loam topsoil field textures that gradually fine to silty clay in the subsoil. The subsoils appear permeable and porous, and crumble to friable micro-aggregates in the hand.  However, subsoils are very firm and compact in situ, and this made for strenuous augering and digging.

The soils on the steeper slopes on the eastern side and northwestern corner are Marron brown fine loams.  These are shallower and less rubefied than the Ava clays, with saprolite or common clasts in the upper metre. There are scattered stones and boulders on the surface, especially on the eastern slope.  A Lake - type pale heavy clay subsoil was seen in one augering in the Marron soils in the SE corner, but is not mapped separately.

Figure 7.1 Soils of the 50 ha LTER plot and upper catchment of Conrad Creek, BCI (click to enlarge)

7. Soils of Specific Research Areas

7.2 Soils of Lutz Creek catchment