A GRAZIERS' GUIDE TO THE MALLEE COUNTRY OF WESTERN NSW Mallee country- what should you do with it? Are you happy that you are doing the right thing with it? Are you worried about the fire hazard? Is mustering taking too long? Are weeds invading your country? Do you know what condition your mallee is in? ARE YOU MANAGING YOUR PROPERTY EFFE01VELY? Although mallee is one of the less pastorally productive range types, there are still options available to increase sustainable production. 'Sustainable' production is production without degradation to the soil and the pasture. Ifthese have been degraded (if soil starts to erode or unpalatable plants become dominant), animal production drops as pasture quality and quantity are lowered. There are lots of constraints to production in mallee country, and perhaps the greatest is one that is common throughout western NSW ­ unreliable rainfall. By planning for dry spells and drought, you can save yourself a lot of problems. This booklet aims to help you understand and manage mallee lands more effectively. 3 Mallee lands, characterised by multi-stemmed eucalypts, occur across southern Australia, generally on wind-formed (aeolian) landforms, with sandy soils. Mallee rangelands occur in the 250 to 380 mm rainfall zone. However, drought is a fact of life in these areas, and the rainfall will often be less than 100 mm per year. The rainfall tends to fall mainly in winter in the southern areas, while in the northern mallee areas (between Ivanhoe and Cobar) rainfall is more evenly spread throughout the year. This diagram shows just how frequently droughts have occurred. We must expect them to continue occurring regularly. Another feature that occurs repeatedly in the mallee is fire-in fact, mallee is a fire-promoting vegetation type. Major wildfires raged through large areas of the mallee during the summers of 1957-58, 1964-65, 1974-75, 1976-77 and 1984-85. In general, mallee soils erode readily once stripped of vegetation and are low in fertility. The soils on the dunes tend to be sands, whereas in the swales and plains calcareous red or brown earths are more common. The mallee in western NSW is most commonly used for gazing, although some areas with higher and/or more reliable rainfall have been developed for cropping. Another significant land use is conservation of the mallee habitat and land type. In fact, about 1800 km2 or almost 10% of the mallee in NSW is conserved in National Parks and Nature Reserves. Other land uses in the mallee include Siliceous Sand Calcareous Earth honey production, eucalyptus oil production and harvesting of broombush for brush fencing. 4 The Mallee Ecosystem Like many rangeland types, the mallee ecosystem is very resilient in the face of changes such as drought, fire, rainfall and even grazing. Changes occur in the quantity and diversity of the vegetation, but they are rarely permanent. Mallee trees dominate the vegetation in mallee communities. They have very deep root systems (roots have been found at depths of 28 m) and are thus able to obtain soil moisture at depth. This means that their growth rate is not affected by individual wet or dry periods. In fact, unlike the more shallowly rooted herbaceous species, mallee eucalypts tend to grow in summer, even though this is the drier season. The herbaceous species commonly grow from early autumn to late spring. The sandy soils of the mallee country tend to favour mallee trees rather than herbaceous plants because most of the water in the soil is found at depth rather than near the surface. As well, mallees concentrate rainfall down their stems to the base of the tree, to such an extent that the amount of water in the soil around the base can be up to ten times higher than the actual rain received. Mallee eucalypts therefore suppress the herbaceous (or pasture) layer in all except wet periods. Consequently, following a fire, it is possible for the pasture layer to flourish for a period of time in the absence of competition from the mallee trees. It is probable that in 'pre-European times’ fire was a more frequent event than it is today. It has been suggested that if fire were more frequent now, dense stands of woody shrubs would be less common, since they are susceptible to fire when young. Mallee Eucalypts • pointed mallee (Eucalyptus socialis) and congoo mallee (E. dumosa) are the most common species • trees are usually multi-stemmed. The stems or trunks increase in size yearly in the absence of fire • main growth period is in summer (October to March) • litter production is highest in summer • regeneration is usually from lignotubers (the 'mallee root') rather than from seed • seedlings are suppressed, developing mainly after some form of disturbance - for example, a spring burn followed by good autumn rain • highly resilient to natural or wildfire; even if above ground part of plant is completely burnt, shoots are produced from the lignotuber • repeated autumn burns (carried out whenever there is sufficient fuel - i.e., every four to five years in open mallee containing speargrass) will reduce mallee density Mallee Eucalypt - Yorrel 5 Mallee Types Mallee can be classified into many different types according to different criteria. The types that follow are only one way of classifying the mallee, based on the type of mallee trees occurring and what other plants occur with them. COMMON MALLEE is the most widespread type occurring in NSW It consists of low, multi-stemmed mallee trees (Eucalyptus spp.) which are closely spaced. When very dense and low, it is known as 'whipstick' mallee. Associated trees include sugarwood (Myoporum platycarpum), rosewood (Heterodendrum oleifolium), needlewood (Hakea leucoptera) and butterbush (Pittosporum phylliraeoides). Wattles (Acacia spp.), cassias (Cassia spp.), turkey bushes (Eremophila spp.), hopbushes (Dodonaea spp.) and other woody shrubs are also usually present. Common Mallee BIG MALLEE is dominated by larger 'bull' mallee trees. The shrub storey is often sparse. Saltbushes (Atriplex spp.) and bluebushes (Maireana spp.) may be present. In wet years speargrasses (Stipa spp.) can become abundant. This type of mallee country is reasonably good grazing country and can be cheaply improved by burning. SALTBUSH MALLEE is similar to Big Mallee but good stands of saltbushes (Chenopodium spp. and Atriplex spp.) or bluebushes (Maireana spp.) are present. PORCUPINE GRASS MALLEE typically occurs on the sandy infertile soils of dune crests and extensive inter-dune sand plains. The understorey is dominated by porcupine grass (Triodia irritans). This type is unsuitable for clearing because of its highly erodible soils. SCRUB MALLEE supports a moderate to dense understorey of shrubs such as broombush (Melaleuca uncinata) and occurs Big Mallee throughout but is most common in the higher rainfall areas. Saltbush Mallee Scrub Mallee Porcupine Grass Mallee 6 IMPORTANT SPECIES IN THE MALLEE Of the 270 or so species recorded in the mallee of western NSW, some have particular significance to the rangeland manager. Some are important for forage, others are weeds, some have value as soil binders, and the presence of others can reveal something about the condition of the pasture. Some examples: Dodonaea attenuata (narrow-leaf hopbush) • a mufti-stemmed shrub occurring mainly in open areas and on abandoned cropping paddocks • a woody weed - suppresses pasture production and reduces carrying capacity • may be browsed, especially by cattle, when other forage is absent • seedlings are susceptible to drought and commonly die during their first or second dry summer • fire can kill adult plants, and does kill seedlings, but also promotes germination of seeds • fire can be used to control invasion of this shrub if there is sufficient grass fuel, particularly when the plants are young • follow-up burns are necessary to control emerging seedlings • grazing management is important following fire - seedlings can Dodonaea attenuata be stressed by allowing large quantities of grass to remain over Narrow-leaf Hopbush dry summer periods • control of outlying shrubs, particularly those less than 1 m tall, is important in limiting speed of invasion • large-scale infestations can be controlled on areas where regular cropping is possible Melaleuca uncinata (broombush) • a mufti-stemmed shrub occurring mainly on the deep red sandy soils and loams of the eastern mallee lands • regenerates after fire, shooting from ground level not grazed by stock • harvested for brush fences Melaleuca uncinata Sclerolaena diacantha (grey copperburr) Broombush (Photo: NPWS) • short-lived perennial plant grows throughout the year, particularly in the warmer months, if moisture is available • highly resistant to drought • responds to isolated rainfall events • a major herbage species after fire • good drought forage Sclerolaena diacantha Grey copperburr (Photo: Plants of Western NSW) 7 Stipa spp. (speargrasses) • previously known as 'variable speargrass; there are now a number of separate species recognised • short-lived perennial grasses, growing mainly in winter or after good summer rains • can respond to rain during any season • shoots from the butt for a number of years if seasons are suitable • palatable and good feed when actively growing, that is, in winter or after summer rain • seeding generally occurs in spring and early summer • following a good growing season, seeds can be a serious problem to stock health, lodging in the eyes, lips and skin • prolific winter growth is likely to carry over into summer and provide fuel for fires Triodia irritans (porcupine grass) • a hummock-forming grass • common on dune crests and sandplains but occurs throughout the mallee • growth occurs mainly in spring and summer or after fire a fire-promoting species • a useful binder of sand dunes • its presence is an indicator of very sandy soil which is liable to drift if cleared. Other species of importance or abundance in the mallee include: Stipa sp.