Selection of pasture species for groundcover suited to shade in mature macadamia orchards in subtropical Australia

Soil erosion is a significant problem in subtropical macadamia orchards in Australia, especially when groundcover vegetation is shaded out under older orchards. The aim of this study was to identify suitable low-growing, perennial groundcovers that would persist in the low light conditions under mature macadamias. Twenty-six legume and grass accessions and 1 herb were evaluated in small plots in a 16-year-old commercial orchard near Lismore, NSW. Plant density, groundcover (%), herbage mass, sward canopy height and groundcover spread were determined in high, medium and low light in the interrow for 2 years (1996–97). Groundcover was also measured for 3 years, on 19 of the accessions in a younger orchard at another site. Dactyloctenium australe provided the best groundcover in both high and low light and met most other specifications for an ideal groundcover for macadamias. Other promising grass species included Paspalum mandiocanum, Panicum laxum and Microlaena stipoides cv. Wakefield. However, Paspalum mandiocanum has been cited as having potential weediness in subtropical Australia, and is not recommended as a groundcover for macadamias. The legumes generally did not perform as well in low light as grass species. However, Arachis pintoi cv. Amarillo and a sterile Arachis pintoi × Arachis repens hybrid provided highest percent groundcover in high and medium light. Further assessment of these species in larger plots to determine their establishment and persistence under heavy orchard traffic and suitability for mechanical harvest operations has commenced

Integrated Part-Farm Irrigation In the Upper Darling Area of New South Wales

In the past five years, there has been a conspicuous increase in the number of integrated part-farm irrigation schemes in the Upper Darling Region of New South Wales. The main characteristics of 26 such schemes are described in this article. Evidence remains of a number of older irrigation installations along the Darling River. Some suggestions are made about the reasons why these earlier schemes failed. These are - (a) Failure of returns to justify the cash and opportunity costs, (b) Increasing labour costs, (c) Erratic water supply, (d) The effects of occasional, severe flooding, and (e) Agronomic problems. Several of these factors are still operative, and may cause difficulties with the present schemes

Integrated Part-Farm Irrigation In the Upper Darling Area of New South Wales

In the past five years, there has been a conspicuous increase in the number of integrated part-farm irrigation schemes in the Upper Darling Region of New South Wales. The main characteristics of 26 such schemes are described in this article. Evidence remains of a number of older irrigation installations along the Darling River. Some suggestions are made about the reasons why these earlier schemes failed. These are - (a) Failure of returns to justify the cash and opportunity costs, (b) Increasing labour costs, (c) Erratic water supply, (d) The effects of occasional, severe flooding, and (e) Agronomic problems. Several of these factors are still operative, and may cause difficulties with the present schemes.Farm Management,

Relationship between diaspore characteristics and distribution of grasses around sheep camps on the northern Tablelands of New-South-Wales

Twenty-seven common grasses on the Northern Tablelands of New South Wales were classified according to their occurrence on or off sheep camps in unfertilised natural pastures. A number of seed and seed germination attributes were examined in relation to the distribution of the individual species. Camps had a greater proportion of introduced grasses, and of annual or short-lived perennials, than off-camp zones. The sheep camp grasses in general had heavier seeds, more rapid germination, and their seeds in general did not have a sharp callus, antrorse hairs on the callus, or awns. If awns were present on sheep camp species a lower proportion were hygroscopically active than for off-camp species. There were no differences in the presence or absence of accessory floral structures in the dispersal unit, hairs on the coleorrhiza or in the shapes of seeds between sheep camp and off-camp grasses. The differences in seed and seed germination characteristics found between sheep camp and off-camp species are explained in terms of the differences in environment (water stress and damage by sheep) encountered by grasses germinating and establishing on and off the sheep camps

Resilience of a high-conservation-value, semi-arid grassland on fertile clay soils to burning, mowing and ploughing.

In grassland reserves, managed disturbance is often necessary to maintain plant species diversity. We carried out experiments to determine the impact of fire, kangaroo grazing, mowing and disc ploughing on grassland species richness and composition in a nature reserve in semi-arid eastern Australia. Vegetation response was influenced by winter-spring drought after establishment of the experiments, but moderate rainfall followed in late summer-autumn. Species composition varied greatly between sampling times, and the variability due to rainfall differences between seasons and years was greater than the effects of fire, kangaroo grazing, mowing or disc ploughing. In the fire experiment, species richness and composition recovered more rapidly after spring than autumn burning. Species richness and composition were similar to control sites within 12 months of burning and mowing, suggesting that removal of the dominant grass canopy is unnecessary to enhance plant diversity. Two fires (separated by 3 years) and post-fire kangaroo grazing had only minor influence on species richness and composition. Even disc ploughing caused only a small reduction in native richness. The minor impact of ploughing was explained by the small areas that were ploughed, the once-off nature of the treatment, and the high degree of natural movement and cracking in these shrink-swell soils. Recovery of the composition and richness of these grasslands was rapid because of the high proportion of perennial species that resprout vegetatively after fire and mowing. There appears to be little conservation benefit from fire, mowing or ploughing ungrazed areas, as we could identify no native plant species dependent on frequent disturbance for persistence in this grassland community. However, the ability of the Astrebla- and Dichanthium-dominated grasslands to recover quickly after disturbance, given favourable seasonal conditions, suggests that they are well adapted to natural disturbances (e.g. droughts, fire, flooding and native grazing)

What drives plant biodiversity in the clay floodplain grasslands of NSW?

An assessment of the relative influences of management and environment on the composition of floodplain grasslands of north-western New South Wales was made using a regional vegetation survey sampling a range of land tenures (e. g. private property, travelling stock routes and nature reserves). A total of 364 taxa belonging to 55 different plant families was recorded. Partitioning of variance with redundancy analysis determined that environmental variables accounted for a greater proportion (61.3%) of the explained variance in species composition than disturbance-related variables (37.6%). Soil type (and fertility), sampling time and rainfall had a strong influence on species composition and there were also east-west variations in composition across the region. Of the disturbance-related variables, cultivation, stocking rate and flooding frequency were all influential. Total, native, forb, shrub and subshrub richness were positively correlated with increasing time since cultivation. Flood frequency was positively correlated with graminoid species richness and was negatively correlated with total and forb species richness. Site species richness was also influenced by environmental variables (e. g. soil type and rainfall). Despite the resilience of these grasslands, some forms of severe disturbance (e. g. several years of cultivation) can result in removal of some dominant perennial grasses (e. g. Astrebla spp.) and an increase in disturbance specialists. A simple heuristic transitional model is proposed that has conceptual thresholds for plant biodiversity status. This knowledge representation may be used to assist in the management of these grasslands by defining four broad levels of community richness and the drivers that change this status

Osmotic adjustment, stomata morphology and function show contrasting responses to water stress in mesic and hydric grasses under elevated CO2 concentration

The physiological response of two species of grasses with C3 and C4 mechanisms syndromes, Napier grass (Pennisetum purpureum Schumach × Pennisetum glaucum (L.) R. Br) and hydric common reed grass (Phragmites australis (Cav.) Trin. Ex Steud) was examined under ambient (aCO2) and elevated CO2 (eCO2), in combination with water and temperature stress treatments. Under eCO2 and subjected to water and temperature stress, the Napier grass maintained higher daytime leaf water potential (LWP) by reducing transpiration (E) and executing larger osmotic adjustment (OA) at an average of 0.85 MPa compared with 0.42 MPa for common reed; carbon assimilation (PN) was thus higher for the Napier grass. Under aCO2 and low temperature, water stress induced no significant differences in OA between the grasses, but Napier grass still had higher PN than that of common reed. Recovery in LWP and PN following re-watering of water-stressed plants was more rapid in Napier grass than that in the common reed; the former had also higher water-use efficiency due to its low specific water use (water use/leaf area) that was just a fraction (less than 6%) that of the common reed. Exposure of common reed to eCO2 reduced stomata number, but increased it in the Napier grass, especially when subjected to water stress and high temperature. Exposure to eCO2 enhanced OA capacity and E control in Napier grass resulting in superior physiological profile over the common reed subjected to water and heat stress

Optimising seed processing techniques to improve germination and sowability of native grasses for ecological restoration

© 2018 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands Grasslands across the globe are undergoing expansive degradation due to human impacts and climate change. If restoration of degraded native grassland is to be achieved at the scale now required, cost-effective means for seed-based establishment of grass species is crucial. However, grass seeds present numerous challenges associated with handling and germination performance that must be overcome to improve the efficiency of seeding. Previous research has demonstrated that complete removal of the palea and lemma (husk) maximises germination performance, hence we investigated the effects of complete husk removal on seed handling and germination of four temperate Australian grass species. Three techniques were tested to remove the husk – manual cleaning, flaming or acid digestion (the latter two followed by a manual cleaning step); these techniques were refined and adapted to the selected species, and germination responses were compared. The complete removal of the husk improved seed handling and sowability for all species. Germination was improved in Microlaena stipoides by 19% and in Rytidosperma geniculatum by 11%. Of the husk removal methods tested, flaming was detrimental to seed germination and fatal for one species (R. geniculatum). Compared to manual cleaning, sulphuric acid improved the overall efficacy of the cleaning procedure and increased germination speed (T50) in Austrostipa scabra, Chloris truncata and M. stipoides, and improved final germination in R. geniculatum by 13%. The seed processing methods developed and tested in the present study can be applied to grass species that present similar handling and germination performance impediments. These and other technological developments (seed coating and precision sowing) will facilitate more efficient grassland restoration at large scale