Vegetative Navigation

Plants grow where they can find a niche – a set of factors that combined provides the resources the plant needs to live.

Environmental factors:

• soil pH affects the release of nutrients, e.g. acidic soils have high iron but low nitrogen, alkaline soils have high sulphur, low iron.
• soil composition sand, clay, humus. These affect crumb size and aeration in the soil. Amount of drainage and nutrient supply are also affected by composition.
• temperature - different plants have different enzymes regulating metabolism. These have different optimum productivity temperatures. Amount of stomata and other structural differences account for functionality at different temperatures. Plants exposed to sub zero temperatures have antifreeze chemical components.
• light – different species are adapted to different light levels ( size and shape of leaf and coating)
• water – different plants have a minimum requirement whilst others are mesophites and xerophites (adapted to the lack of water).
• slope - affects stability and drainage. Steep slopes are often leeched of nutrients.
• geology – different rocks leech different nutrients. Some rock is porous giving rise to water soaks and spring fed creeks.
• aspect – the direction of the slope. North facing slopes receive more sunlight than south facing slopes. Western slopes are often drier as they are in a rain shadow.
• orographic clouds – moist air hits mountains and rises. This cools and condenses watering the mountains in a fine mist. This mist has a cooling effect – significantly lowering the temperature due to the wind chill factor.
• wind – predominantly from the south east. Wind chill.

Rainforests requirement for moisture imply that they are more commonly established where wind and sun will not dry them out, where fires have traditionally not penetrated due to these moisture levels.

South aspects are the more likely to have Rainforest or wet schlerophyll forest.

North aspects are more likely to support drier forest types with xerophites like xanthorrhoea (grass trees) e.g. Mt Huntley.

The presence of orographic cloud implies a proximity to escarpments particularly in the direction the breeze is originating which is usually the southeast.

Some species of trees in South East Queensland have distinct ranges due to a change in environmental factors – the boundaries of their distribution are often distinctive and an understanding of these can help determine a position fix when the degree of foliage prevents getting a GPS fix or using a map to get a precise fix.

Altitudinal forest changes can be expected as one ascends from subtropical rainforest (up to 800 m) to warm-temperate rainforests (600 m to 1200m) and cool-temperate rainforests (above 1100m). Cool temperate forests are only found in several high altitude locations along the McPherson Ranges (e.g. Mt Warning Caldera, Mt Ballow areas). Cool temperate rainforests need high rainfall (above 1700mm pa) and frequent mist. The boundaries can be precisely known for different regions and used in a similar way to depth soundings in marine navigation.

Certain plants or forest structure can be used as key indicators of the forest types: Yellow Carabeen, Figs and three tree strata are typical of subtropical rainforests, Coachwood, Sassafras trees and two tree strata are plentiful in warm temperate rainforest and Antarctic Beech and two strata dominates cool temperate rainforests.

Lantana in southeast Queensland is hard to locate above 800m but the further north, the higher it can be found.

I have noticed certain areas are dominated by certain species. High ridges west of Point Lookout seem to be dominated by Brush Pepperbush (edible purple berries) and Maiden’s Blush. These are responsible for holding a lot of water after a rain.

Wait-a-while seems to have a need for high rainfall. Its range along the border extends to somewhere near Mt Gipps.

Dry rainforest dominated by Hoop Pines occurs where rainfall is <1200 mm per year. Rainforest along the Main Range tends to get less water than the McPherson Ranges. In dry forest the distinction between forest types with altitude becomes vague as the limiting factor becomes moisture rather than temperature.

Recognising the rare mallee species found above 1100 m on Mt Barney is a clear indicator of altitude.

Lamington National Park is an example of an area heavily affected by rain shadow. The coast side gets 2500mm per year , the western areas (away from the caldera) get 850mm per year.

I haven’t noticed that moss grows more prevalently on any side of the tree.