Why the kwongan ecosystem of Australia is so extremely oligotrophic, part 2

Fynbos differs from kwongan in its animal community, in ways that suggest a difference in rates of recycling of nutrients.

The animals of fynbos seem consistently more ecologically powerful than those of kwongan, across a wide spectrum of niches. By ecologically powerful I refer to metabolic wattage (https://en.wikipedia.org/wiki/Watt) per square meter.

Metabolic wattage per unit area can be expected to correlate with the rates of recycling of nutrients, through

• consumption of food and corresponding defecation,
• breakage of plants not eaten,
• passing of urine,
• disturbance of litter and topsoil by trampling, scratching and digging,
• concentration of nutrients in patches of topsoil above subterranean hives (by Microhodotermes viator) and
• recycling to the surface of nutrients leached down to the groundwater (by Microhodotermes viator, see https://www.inaturalist.org/observations/11192567).

The savanna elephant (Loxodonta africana, https://en.wikipedia.org/wiki/African_bush_elephant) is more ecologically powerful than its closest functional counterpart in kwongan, namely the emu (Dromaius novaehollandiae, https://en.wikipedia.org/wiki/Emu). Both species had sparse populations and the emu digests its food as partially as the savanna elephant. However, the latter is incomparably larger-bodied and more destructive of plants.

The ruminants of fynbos, namely the common eland (Taurotragus oryx, https://en.wikipedia.org/wiki/Common_eland) and smaller-bodied species (https://en.wikipedia.org/wiki/Grey_rhebok and https://en.wikipedia.org/wiki/Cape_grysbok and https://www.inaturalist.org/observations?place_id=any&taxon_id=698822) are far more ecologically powerful than the western grey kangaroo (Macropus fuliginosus, https://en.wikipedia.org/wiki/Western_grey_kangaroo) and e.g. the western brush wallaby (Notamacropus irma, https://en.wikipedia.org/wiki/Western_brush_wallaby).

This is because the eland is large-bodied and all ruminants metabolise, grow and reproduce more rapidly than do like-size macropod (https://en.wikipedia.org/wiki/Macropod) marsupials.

The rodents of fynbos, particularly Hystrix africaeaustralis (https://en.wikipedia.org/wiki/Cape_porcupine) and otomyin murids (https://en.wikipedia.org/wiki/Otomys), are more ecologically powerful than those of kwongan (e.g. https://en.wikipedia.org/wiki/Bush_rat and https://en.wikipedia.org/wiki/Pseudomys).

The herbivorous insects of fynbos (particularly Microhodotermes viator, see https://www.inaturalist.org/observations/10997799 and https://en.wikipedia.org/wiki/Microhodotermes and https://en.wikipedia.org/wiki/Heuweltjie) are more ecologically powerful than those of kwongan (https://www.researchgate.net/publication/229990983_Abundance_and_diversity_of_termites_Isoptera_in_unburnt_and_burnt_vegetation_at_the_Barrens_in_Mediterranean_Western_Australia and https://www.semanticscholar.org/paper/The-Australian-harvester-temites-of-the-genus-%3A-Watson-Perry/369cf1c6774f5d38e99510b5e9f47a8a1c271ab0).

This is reflected in the far larger body-sizes and far more rapid metabolism, growth and reproduction of myrmecophagous mammals in fynbos than in kwongan (https://www.researchgate.net/publication/271689805_Why_Are_Termite-_and_Ant-Eating_Mammals_Smaller_in_Australia_Than_in_Southern_Africa_History_or_Ecology).

Golden moles (https://en.wikipedia.org/wiki/Amblysomus and https://www.inaturalist.org/taxa/42482-Amblysomus-corriae and https://en.wikipedia.org/wiki/Chrysochloris and https://www.inaturalist.org/taxa/42513-Chrysochloris-asiatica), which have no counterparts in kwongan, form subsurface runs (e.g. https://www.inaturalist.org/observations/11016230) in fynbos. The result is an effective tilling of the topsoil in fynbos but not in kwongan.

What this means is that, although the concentrations of nutrients are similarly limited in the two ecosystems,

• the recycling of nutrients in topsoil is more rapid/continual in fynbos than in kwongan, and
• there is a categorical difference in that nutrients are recycled to the topsoil from the groundwater (by Microdotermes viator) in fynbos but not in kwongan.

to be continued...

Posted on Φεβρουάριος 20, 2022 0806 ΠΜ by milewski