Introducing pappusgrasses

In the subfamily Chloridoideae ( of the family Poaceae, there is a tribe called Pappophoreae. The common name of this tribe is pappusgrasses. There is nothing weedy- or vulgar-looking about these grasses, yet they are widespread.

Pappusgrasses are insubstantial-looking. However, when one gets an eye for them, they turn out to be important grasses in semi-arid ecosystems on at least four continents – that is, functionally, if not in terms of sheer biomass.
In the strict sense, pappusgrasses consist of just three genera: Schmidtia, Cottea and Enneapogon.

Pappophorum (American and also called pappusgrass, is similar, but probably not particularly closely related.
Pappusgrasses, at the level of tribe, genus and species, are remarkably widespread.

Cottea ( is monospecific and restricted to the semi-arid USA.

Schmidtia occurs in Africa and Pakistan, and the two species common in South Africa, viz. the annual S. kalahariensis and the perennial S. pappophoroides, both occur also in the Sahel. They are not naturally restricted to southern Africa. So, there are situations north of the equator in which Schmidtia - which South Africans tend to associate with Kalahari sands - occurs with presumably equivalent commonness.

The largest genus of pappusgrasses in the strict sense is Enneapogon. Its species present as local grasses, but the genus and some of its species are actually widespread.

For example, Enneapogon desvauxii (formerly called E. brachystachyus or brachystachys in South Africa) occurs commonly in the Karoo, where it is regarded as exologically typical and an important part of the diet of the springbok (Antidorcas marsupialis, However, the same species occurs naturally also in America, as far south as Chile and Argentina.

For some reason, pappusgrasses seem absent from Patagonia, which surprises me because that might seem to be idea habitat for them. Perhaps they are restricted to warm climates?

About 16 spp. of Enneapogon occur in Australia, where they are an important part of the diet of the red kangaroo just as their congeners are important to gazelles in Africa and presumably Asia.

If I recall correctly, Ken Tinley’s explanation of the former treks of the springbok has to do with Enneapogon and the periodic usurping of this resource by irruptive locusts in the Karoo. Discussing Enneapogon over the years with Ken, I always had the sense that this was a genus of grasses which, if not restricted to southern Africa, was closely associated with indigenous grazers here. I now see this differently, i.e. with a wider perspective.
Summarising so far, for emphasis:
What passes off as a typical Karoo grass, associated with the springbok, is actually a cosmopolitan grass (putting aside the details of which species is which), abundant and widespread also in Australia.

All pappusgrasses seem similar in growth-form: perennial or annual, too flimsy to be called tussocks, but on the other hand only weakly able to spread vegetatively. I would not call them lawn-forming. The seeding culms are fairly short (< 50cm and usually < 30cm). All seem to dry off in the dry season. These grasses are unsuitable for bulk-and-roughage grazers, but are particularly suitable for gazelles (and hartebeest/tsessebe) and kangaroos, and presumably guanaco in South America and pronghorn/hare in North America.

As far as I know, all pappusgrasses are palatable and easily digestible. However, that they are not substantial enough to form a staple for most grazers.

Some species have a peculiar mode of regeneration, in which the small ‘tussock’ appears to be perennial because greens re-emerge from the dry plant. On closer examination, what has happened is that the plant has died (i.e. it is actually annual) but the seed-heads have a special design in which they remain lodged at ground level within the plant, and then germinate in-situ instead of being dispersed.

Some qualify as cleistogamous (, somewhat like the peanut (Arachis hypogaea, However, the fruit is not actually borne underground, as far as I know.

I am unsure if this self-pollination and 'anti-dispersal' is, at least in part, an adaptation to grazing, i.e. some kind of alternative to lawn-formation. However, it does seem to mean that herbivores can keep the sward short (eating whatever seed-heads emerge above the leaves) without destroying the regenerative capacity of these apparently flimsy plants.
In a sense, what this hints at is that pappusgrasses tend to be something analogous with a lawn - but suited to semi-arid conditions, and never achieving the kind of conspicuousness that most ecologists notice. They seem to be a mere tissue (low, sparse, and usually dried-out looking), but may actually be quite productive for grazers overall.
It seems obvious that pappusgrasses have little to do with fire. Not only do they tend to be eaten/decomposed before becoming flammable, but they grow with limited biomass, unable to carry fire even in drought.
The important inference of all this is as follows:

Australia is the only continent on which both pappusgrasses and hummock grasses are locally dominant (in separate areas). Therefore, it is to Australia that we should look for the environmental distinctions (particularly edaphic differences) between hummock grasslands (which accumulate biomass and are adapted to wildfire) and pappusgrasslands (which support herbivores and do not benefit from fire).

Australia may show that the main difference is based on soil texture (hummock grasses more on sands). However, the vegetation on loams in e.g. the Pilbara is complex, so this needs further investigation.

Enneapogon desvauxii:

Distribution of Enneapogon desvauxii in southern Africa:

Distribution of Enneapogon desvauxii in North America:

Examples of the distribution of Enneapogon spp. in Australia, showing about a dozen of the ?16 spp.:

Global distribution of genus Enneapogon:

Cottea pappophoroides, southwestern USA:

Publicado el julio 3, 2022 01:35 MAÑANA por milewski milewski


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