Shrub Control Research Articles

Expert advice for shrub control.

SHRUBKILL is a microcomputer based decision-support system which provides expert advice on the use of fie to control non-desirable shrubs and thus improve grazing potential in the semi-arid woodlands of eastem Australia. Pescribed fire is argued to be the only economically viable management option for broad-scale shrub control in these rangelands. Management decisions about "when" and "how" to bum and the cost and expected economic benefit of buming involve answering many difficult questions which can be aided by the advice of experts. However, these experts are not always available to give on-the-spot advice to managers. SHRUBKILL is a decision-support system that has incorporated the knowledge of fire-experts in an easy-to-use microcomputer program to: advise the user on what the "expert" would have recommended; provide detailed information supporting the expert's recommendation; and give summaries of the consultation. SHRUBKILL was written in BASIC on an IBM Personal Computer but it will run on IBMPC compatibles.

The economics of prescribed burning for shrub control in the semi-arid woodlands of north-west New South Wales.

Costs and benefits of prescribed buming for shrub control in a representative 2000 ha paddock are estimated, based on anecdotal and survey data collected from graziers in the Western Division. For a hypothetical paddock, two bums were assumed to take place during the space of seven years. Costs include those for constructing firebreaks and controlling the fire. In particular circumstances, income from grazing may be foregone when "spelling" the paddock prior to the bum, and also after the bum until rainfall has induced the regrowth and seeding of pasture. Benefits from prescribed buming include increased livestock production, primarily through higher lamb weaning percentages and wool cuts from the self-replacing Merino flock, reduced mustering time and improved surveillance of livestock, resulting in better control of pests such as blowflies, lice, feral pigs and foxes. Capital value of the land is also improved. Cash flows over a 20 year period indicate that prescribed burning for shrub control is profitable. Despite this, users should carefully assess the maximum area that property cash flows will allow for setting aside to bum when an appropriate season allows.

Response of Three Shrub Communities in Southeastern Idaho to Spring-Applied Tebuthiuron

Tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-61lN, N'-dimethylurea) pellets containing 20 and 40%0 active ingredient were applied at 0.6 and 1.1 kg ha-' during May 1979 to range sites dominated by mountain big sagebrush (Artemisia tridentata subsp. vaseyana Nutt.), threetip sagebrush (A. tripartita Rydb.), and gray horsebrush (Tetradymia canescens DC) to determine effectiveness for shrub control and response of associated grasses and forbs. Sagebrush densities were significantly less (P?.05) in 1984 on all herbicide treated sites compared to the untreated sites. The 1.1 kg ha-' (20P) treatment reduced the densities of all shrubs more than other treatments at all sites. Grass production was significantly (PiS.05) greater on plots treated at 1.1 kg ha-' (40P) at the mountain big sagebrush and threetip sagebrush sites. Forb production did not respond to tebuthiuron treatments. Grass production was not increased or decreased signiflcantly by any treatment at the gray horsebrush site. For sites with similar soil and environmental conditions, the 1.1 kg ha-' (40P) treatment should give sufficient control of sagebrush to allow for significant increases in total grass and forb production.

Response of Three Conifer Species to Site Preparation and Shrub Control

Abstract A 5-year field study was conducted to determine the effect of three methods of site preparation in combination with three levels of shrub suppression on subsequent microenvironmental, shrub and tree responses. Shrub canopy volume and survival, growth, and water potential of planted ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Lawson.), sugar pine [Pinus lambertiana Dougl. (Strobus L. Mold.)], and white fir [Abies concolor (Gord. & Glend.) Lindl.] were measured. Ponderosa pine survived better than sugar pine or white fir regardless of shrub presence or absence. Shrub canopy volume did not influence tree survival; however, the presence of shrub debris from some treatments increased planting difficulty and resulted in increased tree mortality. Predawn and midday water potential, height, stem diameter, and canopy volume of conifers were highest when shrub canopy volumes were low. Forest Sci. 32:61-77.

The case for prescribed burning to control shrubs in eastern semi-arid woodlands.

of the paper highlights his willingness to contribute his experience freely to the discussion of issues confronting rangeland managers: "In this paper I hope to lead you through the financial history of Willangee Station. Through decisions we made, the mistakes we have made, the lessions we have learnt, the debts we have taken on and the profits we have made. Our aim is to expose all of these factsso people may learn from them'. The paper, along with others presented at the Seminar, was published in the Australian Rangeland Journal. In 1980 Bill hosted a tour of Willangee by the Barrier Environment Group during a Conference on the theme'% the West Darling becoming a Desert?" By his actions, conservationists and graziers were brought together duringa period when conservation of Australia's arid lands was becoming a major issue. Through his leadership of the Broken Hill Branch of the Australian Rangeland Society, Bill has contributed greatly to the exchange of ideas between academics, the pastoralist community and conservationists. With such a wealth of knowledge of the district and its people Bill has been aguiding influence to the Broken Hill Branch, the Committee and its members. Aust. Rangel. J. 7(2) 1985, 64- 74 THE CASE FOR PRESCRIBED BURNING TO CONTROL SHRUBS IN EASTERN SEMI-ARID WOODLANDS K.C. Hodgkinson and G.N. Harrington CSIRO Division of Wildlife and Rangelands Research, Private Bag, P.O., Deniliquin, N.S. W. 2710 Abstract A theor) for shrub control by prescnbed burn~ng In semi-and woodlands of eastern Australla IS outlmed. Th~s theory IS based on ~nev~table shrub Increases wh~ch occur pnnc~pally by ep~sod~c, w~despread, mass establ~shment events Wet per~ods whlch foster shrub establ~shment also promote abundant grass growth pred~sposlng the plant community to be~ng burnt Fue then k~lls nearly all recently establ~shed shrubs and many of theadult shrubs, thereby con- trollmg the shrub populat~on Today, fire IS much less frequent and IS prevented altogether In some areas. Prescr~bed burn~ng before any potential wddflre season w~ll both control shrubs and hm~t the spread of wddfires Three constraints to the adopt~on of prescrtbed burn~ng are recogn~sed economlc benefits are ma~nly real~sed over a 10-20 year term: * grazlers have l~ttle experience and Infrequent opportunltles to learn about fire; grazlers are reluctant to accept the nsks associated with burnmg. If semi-and woodlands are to be burnt at a frequency necessary for shrub control. grazlng pressures may need to be reduced to husband the vlgour of perenn~al pasture plants Opponun~st~c burnlng should take place at times of w~despread shrub seedl~ngestabl~shment. Prescribed burnlng IS the only known method for broad-scale shrub control and relevant State departments and grazlers are urged to collaborate In prescr~bed burn~ng to a regonal strategy. rather than property by property

Assessment of Landsat Multispectral Scanner spectral indexes for monitoring arid rangeland

The utility of Landsat Multispectral Scanner (MSS) spectral indexes for monitoring arid range land was tested in south-central New Mexico by determining correlations between spectral indexes and vegetation parameters. Also, spectral index change from 1976 to 1980 was calculated from retrospective MSS data and compared with qualitative ground truth to determine if vegetation change could be detected using spectral indexes. MSS band 5, albedo, and the Kauth-Thomas Brightness component were correlated with total vegetation cover, with maximum r = −0.844. Dry season green vegetation indexes were the best estimators of combined cover of mesquite plus snakeweed, two shrub invaders of degraded grassland. The dry season-wet season difference in green vegetation indexes gave rough estimates of grass cover. In retrospective monitoring, cover change in response to shrub control and changes in grating intensity and rainfall was detected by change in brightness indexes. Brightness index change consistently differentiated between cover increase and decrease, but Index change was apparently offset from true cover change. The offset was attributed, at least in part, to failure of the methods used to standardize MSS scenes for differences in sensor response. In contrast to brightness indexes, green vegetation indexes failed to consistently differentiate between cover increase and decrease.

Vegetation changes and animal productivity under sheep and goat grazing on an arid Belah (Casuarina cristata) - Rosewood (Heterodendrum oleifolium) woodland in western New South Wales.

In an arid (275 mm rainfall) belah (Casuarina cristata)-rosewood (Heterodendrurn olrifolium) woodland, goat does of feral origin and Merino ewes were grazed separately or in mived groups to.determine the relative effects of the different com- binations on the shrub and herbaceous vegetation, and on total animal production. The goats browsed the accessible foliage of trees, but did not obtain a substantial amount of their forage from that source. Thus they were competitive with sheep for the herbaceous layer (principally Stipa variabilis (variable speargrass) and Sclerolaet~a spp. (copperburrs). Grazing sheep and goats together did not achieve greater animal production than grazing them separately. Under drought conditions, those sheep grazing in conjunction with goats lost weight sharply in comparison with the goats, or to other sheep grazing without goat competition. The weights of the kids born in this trial were only 60% of the weights of the lambs, at both weaning and 1.5 years of age, although the net reproduction rate of does (120%) was twice that of the ewes (57%). Goat grazing did not suppress the unpal- atable shrubs. It is concluded that the grazing of feral goats. either alone or mixed with sheep, will not result in higher animal production or shrub control in this woodland community.

Application Abstracts

The effect of feral goats and sheep on the shrub populations in a semi arid woodland G. Harrington Feral goats have been suggested as a means of counteracting the increase in shrubs in some grazed woodlands in western New South Wales and Queensland. Hopbush and mulga can be destroyed and punty reduced by very heavy goat pressures but the difficulties and expense of such a treatment are prohibitive for extensive areas. Neither mature or seedling budda and turpentine are susceptible to goats although root sprouts after bulldozing budda and wilga can be controlled by heavy goat pressure. Moderate grazing by goats has very little effect on any shrub except young mulga. Goast are not recommended for shrub control in these areas. Effect of fertility level on the yield of some native perennial grasses on the North-West Slopes, New South Wales G.M. Lodge Native grasses have traditionally been regarded as unresponsive to applied fertilizer, and any fertilizer application to the rangelands of northern New South Wales has largely resulted in increased legume yield. In this study some native grass species such as Bothriochloa macra (redgrass), Chbris truncata (windmill grass) and Dichanthium sericeum (bluegrass) were found to be responsive to applications of nitrogen, phosphorus and sulphur. Information on the response of individual species to varying fertility conditions will allow a greater under. standing of the ecology of rangelands and enable more informed management practices to be used. A survey of the regeneration of some problem shrubs and trees after wildfire in western New South Wales A.D. Wilson and W.E. ~Wulhanz Following extensive wildfires in 1974175 the recovery of several different species of sh~ubs and trees was recorded at a number of sites across western New South Wales. Fire had a considerable effect on the survival of some plant species, but only a minor effect on others. Young trees of white cypress pine (Callitris columellaris) and mulga (Acacia aneura) had a poor recovery rate and hence could be thinned by the use of fire. Narrow-leaved hopbush (Dodonaea attenuata) and punty (Cassia eremophila var. platypoda) suffered severe losses at some sites, but not at others. Large numbers of seedlings emerged after the fires, so it is unlikely that a single fire would have a lasting effect on the density of these shrubs. Other woody plants - yarran (Acacia homalophylla) budda or sandalwood (Eremophila mitchellii) and turpentine or budda bush (E. sturfii) - had only low death rates and would be difficult to control by burning. However, seedlings which had emerged prior to the fires were considerably reduced in number so that burning may have a greater role in keeping country clear of these shrubs than in the eradication of mature stands. These results may not apply under all conditions, but they do provide a guide for further research on burning under controlled conditions as a means of scrub control. SYMPOSIUM ON POPLAR BOX (EUCAL YPTUS POPULNEA) LANDS

A Comparison of Planting and Natural Succession After a Forest Fire in the Northern Sierra Nevada

(1) Approximately 15 000 ha of mixed coniferous forest in the northern Sierra Nevada of California were burned during the Donner Ridge Fire in 1960. (2) Two areas were compared in the burnt forest that had received different management: one area was planted with Pinusjeffreyi Grev. and Balf. and sprayed with 2,4,5-T for shrub control; the other area was allowed to follow a natural post-fire succession. (3) Similar numbers of P. jeffreyi occurred on both sites, but shrubs and herbs were greatly reduced on the planted area and grasses increased. (4) Only Ribes cereum Dougl., which is normally a minor component of the natural shrub community, flourished in the planted area. (5) The ecological effects of conifer plantations in the northern Sierra Nevada are discussed.

Fire Effects on Semidesert Grasses and Shrubs

1 Central headquarters maintained in cooperation with CoZorado State University at Fort Collins. Author stationed at Tucson, Arizona, in cooperation with the University of Arizona. world (Humphrey, 1958; Weaver and Clements, 1938). Thornber (1910) observed that several semidesert shrubs were killed by fire in southern Arizona. More recently, Humphrey (1949), Humphrey and Everson (1951), and Reynolds and Bohning (1956) have reported on the effects of fires in killing semidesert shrubs. The effects of burning on associated annual and perennial grasses have received less attention. The present studies consisted of measuring changes in grass and shrub cover after burning and reburning to determine (1) the effectiveness of planned burning for shrub control, and (2) the direct and indirect effects of burning on perennial grasses. The study period, 1952-1965, included several years with precipitation above average and several years with precipitation below average.

Shrub Control and Reseeding Effects on the Oak Chaparral of Arizona

Highlight Burning-reseeding and burningreseeding-herbicide treatments near Dewey, Arizona significantly reduced oak chaparral shrub cover for over 7 years and resulied in significantly greafer grass production for 5 fo 7 years. Grass producfion was up fo 770 lb/acre greater on treated areas than on untreated, depending on fhe type of treatment, number of years following freafmenf, and various environmental factors.

Shrub Control Studies in the Oak-Chaparral of Arizona

Shrub Control Studies in the Oak-Chaparral of Arizona

A Southwestern Rancher's Viewpoint of Shrub Control

A Southwestern Rancher's Viewpoint of Shrub Control

Encroachment and Control of Shrubs in Relation to Grassland Development in Africa

Encroachment and Control of Shrubs in Relation to Grassland Development in Africa

The use of herbicides for the control of Alder brush and other swamp shrubs in the Lake States.

The use of herbicides for the control of Alder brush and other swamp shrubs in the Lake States.

Shrub Invasion of Southern Arizona Desert Grassland

E NCROACHMENT of mesquite, burroweed, and other noxious shrubs has seriously reduced the carrying capacity of thousands of acres of desert grassland ranges. Two principal theories have been advanced for this invasion-grazing and control of fires. In the early part of the century Griffiths (1910), and Thornber (1910) observed the large mesquites along the water courses, and the presence of young mesquites on the ridges separating them. Griffiths predicted that both mesquite and other shrubs would increase in size and number on these ridges. Both expressed the opinion that fire, formerly unchecked and with abundant fuel, had maintained the grassland in its original shrub-free state. They believed that livestock grazing had controlled fires indirectly through removal of fuel by trampling and grazing. Later, Wooton (1916) observed that Griffiths' prediction was coming true. He noted that occasional fires were the only check on the increasing shrubs. Leopold (1925) advanced this same theory for the short-grass areas of northern Arizona and called attention to the encroachment of oak and juniper from the higher elevations. This invasion followed the cessation of fires which was shown by burn scars to have been some 40 years earlier. He doubted, however, that the lower levels of the desert grassland ever supported sufficient vegetation for widespread or frequent fires. Humphrey (1949) called attention to the earlier work of Thornber, Griffiths and Wooton. In a study of two burned areas near Tucson, Arizona, he observed that burroweed and snakeweed were effectively controlled by fire. He also recorded a moderate degree of control of such shrubs as jumping cholla; mesquite and palo verde. The grazing theory also has many adherents (Allred 1948, Upson et al 1937, Young et al 1948). In general, they believe that breakdown of the sod and compaction of the soil surface through grazing pressure and drought has led to the invasion of shrubs, causing a grazing disclimax. In refutation of the fire theory of shrub control, Allred (1948) has pointed out that some of the most frequently recurring fires are in the Texas brush country where mesquite is densest. It should be kept in mind that Allred's observations pertain primarily to Texas while the workers referred to in the previouis paragraphs obtained their results in Arizona. Further support is lent to the grazing theory by the fire-resistant nature of mature mesquites. Although the top is readily killed by hot grass fires, the plant is a stump sprouter, and usually sprouts following severe injury to the top. Many other desert plants are similar to mesquite in this respect. Neither of these theories has been adequately proved. Doubtless both fire and grazing have played an important part in the ecology of the desert grassland. Further information concerning the rate of shrub invasion, its relation to management practices and forage production, and the successional relationships of the invaders is necessary for control of the

Fire as a Means of Controlling Velvet Mesquite, Burroweed, and Cholla on Southern Arizona Ranges

A THOROUGH study needs to be made of the possibility of controlling undesirable shrubs or trees by fire on southern Arizona ranges. Other control methods, even if effective, are generally so costly as to prevent their general adoption on low-value range. Yet, it is on these low-value ranges that control is frequently most urgently needed. It has been known for many years that certain shrubs are readily killed by fire while others are very difficult to eradicate in this way (1, 6). Many observers of range conditions in the Southwest and elsewhere have suggested the use of fire as a tool to control undesirable trees and shrubs (1, 3, 6, 7). In 1907, Thornber (7) noted that when an area supporting burroweed (Aplopappus tenuisectus) was burned, all of the plants were killed, even when only partly charred. Such shrubs as catclaw (Acacia greggii), creosote bush (Larrea tridentata), Mormon tea (Ephedra trifurca), velvet mesquite (Prosopis velutina), and graythorn (Condalia lycioides), were also killed. Thornber, in 1910 (8), again reported on burning as a means of shrub control. He stated that burroweed, creosote bush, Mormon tea, and hackberry could be killed at very small expense by burning during the dry foresummer, i.e., May to June, inclusive. He noted further that charred stumps, occurring on certain areas, were an indication that fires had occurred commonly in the past and that velvet mesquite, formerly held in check by occasional fires, was at that time spreading. In the same year Griffiths (3) noted that areas formerly grass covered on the Santa Rita Experimental Range, by 1910 supported an abundant growth of young velvet mesquite and other shrubs. During the seven years that he had observed the area he noted a very definite increase in both shrubs and mesquite. He says in this connection: The probability is that neither protection nor heavy grazing has much to do with the increase of shrubs here, but that it is primarily the direct result of the prevention of fires.-The prediction is ventured that the time is coming when these foothill grassy areas, which now have only an occasional small shrub, will be as shrubby as the deserts and lower foothills below them, if not more so. He continues with the thought that although mesquite may have been spread to some extent on the Santa Rita Experimental Range by grazing animals, its increase was more probably due to grazing that removed the combustible ground cover, thus preventing fires. Griffiths concluded that before the area was grazed by domestic stock it probably produced more grass than in 1910 and that it was formerly burned at rather frequent intervals. In his opinion this burning had little effect on the grasses but almost entirely prevented establishment of undesirable shrubs. Bec8use of the slow growth rate of the shrubs he felt that they could be controlled by fires occurring only once in ten years. He believed also that were it not for recurrent fires the then grass-covered mesas would have been dominated by shrubs as were the more