Floristic composition and pasture condition of Aristida/Bothriochloa pastures in central Queensland. I. Pasture floristics

Abstract

A survey was conducted in central inland Queensland, Australia of 108 sites that were deemed to contain Aristida/Bothriochloa native pastures to quantitatively describe the pastures and attempt to delineate possible sub-types. The pastures were described in terms of their floristic composition, plant density and crown cover. There were generally ~20 (range 5–33) main pasture species at a site. A single dominant perennial grass was rare with three to six prominent species the norm. Chrysopogon fallax (golden-beard grass) was the perennial grass most consistently found in all pastures whereas Aristida calycina (dark wiregrass), Enneapogon spp. (bottlewasher grasses), Brunoniella australis (blue trumpet) and Panicum effusum (hairy panic) were all regularly present. The pastures did not readily separate into broad floristic sub-groups, but three groups that landholders could recognise from a combination of the dominant tree and soil type were identified. The three groups were Eucalyptus crebra (narrow-leaved ironbark), E. melanophloia (silver-leaved ironbark) and E. populnea (poplar box). The pastures of the three main sub-groups were then characterised by the prominent presence, singly or in combination, of Bothriochloa ewartiana (desert bluegrass), Eremochloa bimaculata (poverty grass), Bothriochloa decipiens (pitted bluegrass) or Heteropogon contortus (black speargrass). The poplar box group had the greatest diversity of prominent grasses whereas the narrow-leaved ironbark group had the least. Non-native Cenchrus ciliaris (buffel grass) and Melinis repens (red Natal grass) were generally present at low densities. Describing pastures in terms of frequency of a few species or species groups sometimes failed to capture the true nature of the pasture but plant abundance for most species, as density, herbage mass of dry matter or plant crown cover, was correlated with its recorded frequency. A quantitative description of an average pasture in fair condition is provided but it was not possible to explain why some species often occur together or fail to co-exist in Aristida/Bothriochloa pastures, for example C. ciliaris and E. bimaculata rarely co-exist whereas Tragus australianus (small burrgrass) and Enneapogon spp. are frequently recorded together. Most crown cover was provided by perennial grasses but many of these are Aristida spp. (wiregrasses) and not regarded as useful forage for livestock. No new or improved categorisation of the great variation evident in the Aristida/Bothriochloa native pasture type can be given despite the much improved detail provided of the floristic composition by this survey.

The value of grasslands for pest suppression: an assessment of grassland refuge quality and their integration into agricultural landscapes

“…However, poorly managed grasslands can also provide habitat and resources utilised by pests, allowing their populations to build up and colonise crops quickly in large numbers, negating the benefits of increased predator populations. Many of the Native grasslands remaining in agricultural regions have been degraded through overgrazing, nutrient depletion and mechanical disturbance, often resulting in neglected grasslands invaded by weeds and other undesirable, unpalatable or exotic species (Silcock & Scattini, 2007;Silcock et al, 2015b; Chapter 2). Several agricultural pest species have been associated with weeds; thus, Native grasslands have the potential to provide important refuge for a number of key pests (De Barro et al, 1992;Parry et al, 2015;Yasuda & Yasuda, 2016).…”

“…(Lloyd et al, 2007;Silcock & Scattini, 2007;O'Sullivan, 2013;Chapter 2). Dominant native grass communities include Queensland bluegrass (Dichanthium sericeum) and Aristida-Bothriochloa pastures which can also include various species of Panicum, Chloris, Astrebla, Themeda and Chrysopogon (Silcock & Scattini, 2007;Silcock et al, 2015a; Chapter 2).…”