Shrubby Understorey Research Articles

Influence of light, water stress and shrub cover on sapling survival and height growth: the case of A. unedo, F. ornus and S. domestica under Mediterranean climate

Resprouter species are of great interest for Mediterranean forest resilience as they can survive fire or drought by activating dormant vegetative buds to produce regrowth. Understanding which factors control the early growth and survival of these species is needed to develop strategies to enhance stand resilience. In this study, three broadleaved resprouter species, two trees—Fraxinus ornus and Sorbus domestica—and a shrub—Arbutus unedo—were planted under a gradient of pine cover. Sapling survival and height growth were monitored for 6 years, 2 years after their plantation, as well as light and shrub cover. We developed a two-strata forest water balance model, which produces a water stress index. We aimed to determine the effect of light, water stress and shrub cover on sapling survival and height growth using a modelling approach. We found that high levels of transmittance had a negative impact on both survival and height growth of F. ornus and S. domestica, while it had a positive effect on A. unedo growth. Water stress was found to negatively affect survival and height growth of all species. Lastly, shrub cover had an overall positive effect on the survival and growth of saplings, indicating a facilitating effect of the shrubs. Our results suggest that shade-tolerant tree species like F. ornus and S. domestica are more suited to moderate and light cover, while photoinhibition-tolerant shrub species like A. unedo are more adapted to open conditions. To maximize sapling survival and growth, we recommend preserving the shrubby understorey when present.

The population status of southern hairy-nosed wombats (Lasiorhinus latifrons). II. Landscape factors affecting distribution and abundance

The southern hairy-nosed wombat has a fragmented distribution across the arid and semiarid regions of southern South Australia and south-eastern Western Australia. Its distribution and abundance are highly patchy, with large clusters of warrens in some areas but few to no warrens in adjacent areas. In order to understand why this occurs, we mapped the species’ distribution and correlated the locations of over 8130 data points (5349 presence points and 2781 absence points) with environmental and landscape data. Overall, the wombat distribution is influenced by rainfall, with no wombats in areas where the mean annual rainfall is <154mm. Abundance is greatest in areas where rainfall is >227mm per annum. At the regional/local scale, warrens are found only in areas where the soil clay content is between 9 and 40%, and warren abundance is higher in open vegetation classes (saltbush/bluebush shrublands, grasslands) than in closed vegetation (mallee woodlands with shrubby understorey). Over-riding all of these environmental influences are anthropogenic land-use practices: although 38% of the wombats are located in protected areas and 51% are located on grazing land, they are virtually absent from croplands (~2%).

An isolated population of the southern scrub-robin (Drymodes brunneopygia) in the Great Victoria Desert

From 2013 to 2015 we recorded an isolated, highly fragmented and previously undocumented population of the southern scrub-robin within the arid shrublands of the Great Victoria Desert. In this region, the southern scrub-robin persists in scattered and intermittent areas of long-unburnt mulga (Acacia spp.) shrubland, with a dense shrubby understorey dominated by Aluta maisonneuvei and Eremophila shrubs. The Great Victoria Desert supports the only known desert population as the southern scrub-robin otherwise occurs in the temperate and semiarid shrublands of southern Australia and occurs in the desert at the arid extreme of its range. Fire is highlighted as a significant threatening process due to the species’ restricted occurrence (less than 5% of the landscape in the region), low reproductive rate, limited dispersal capability and persistence within long-unburnt and fire-sensitive habitats. As forecast environmental changes are likely to render the arid extremes of the species’ range unsuitable, this outlying, desert population is potentially declining and of conservation significance.

Predicting fire behaviour in dry eucalypt forest in southern Australia

This paper describes the development of two empirical models to predict the potential spread of an established line of fire in dry eucalypt forest with a shrubby understorey. These models use inputs of fine fuel moisture, wind speed, near-surface fuel height, and either a numerical fuel hazard score or a descriptive fuel rating for the surface and near-surface fuel. A model to predict flame height from rate of spread and elevated fuel height is also presented as a guide to suppression difficulty.Models were developed using data from a series of simultaneous experimental fires in fuels of different fuel ages ranging from 2 to 22years since last fire. They were tested against data from independent experimental fires and well documented wildfires that were assigned reliability ratings for fuel, weather and spread rate. Models performed reliably when the reliability of wildfire data ratings for fuel and weather were also high.Models predict the potential rate of spread and are likely to over-predict the spread of fires starting from a point ignition during the early stages of development when the headfire is less than 120m wide. Existing guides should be used for prescribed burning operations based on point ignition, and the models described here can be used to predict rate of spread from line ignition.Predictions from the new models will be more reliable when rate of spread is averaged over an interval of 30min or longer. The reliability will be low when compared to observations made over short time intervals, at specific points in the topography, or when very large fires interact to produce wind speeds that are very different to the ambient wind in the open.

Influence of fine‐scale habitat requirements and riparian degradation on the distribution of the purple‐crowned fairy‐wren (Malurus coronatus coronatus) in northern Australia

AbstractSpecies distributions are influenced by variation in environmental conditions across many scales. Knowledge of fine‐scale habitat requirements is important for predicting species occurrence and identifying suitable habitat for target species. Here we investigate the perplexing distribution of a riparian habitat specialist, the western subspecies of the purple‐crowned fairy‐wren (Malurus coronatus coronatus), in relation to fine‐scale habitat associations and patterns of riparian degradation. Surveys of vegetation attributes, river structure and disturbance indicators that are likely to be causal determinants of the species occurrence were undertaken at 635 sites across 14 catchments. Generalized Linear Mixed Modelling demonstrated that the probability of purple‐crowned fairy‐wren occurrence increased with Pandanus aquaticus crown cover, shrub density and height of emergent trees, while riparian structure and signs of cattle were indirect predictors of occurrence. As our study area predominantly contained Pandanus type habitat, we failed to identify river grass as an important component of habitat. Predictions from a cross‐validated model of purple‐crowned fairy‐wren occurrence suggested distribution is constrained by three factors: (i) low quality of local habitat within catchments where the species occurs; (ii) broad‐scale reduction in habitat quality that has resulted in extinction of the species from parts of its range; and (iii) unmeasured variables that limit the exploitation of suitable habitat. The reliance of the species on dense shrubby understorey suggests conservation efforts should aim to maintain the complexity of understorey structure by managing fire and grazing intensity. Efforts to halt the continuing decline of riparian condition and maintain connectivity between areas of quality habitat will help to ensure persistence of riparian habitat specialists in northern Australia.

Returning biodiversity of rehabilitated forest on a coal mined site at Tanjung Enim, South Sumatra

Suhartoyo H, Munawar A, Wiryono. 2012. Returning biodiversity of rehabilitated forest on a coal mined site at Tanjung Enim, South Sumatra. Biodiversitas 13: 13-17. Restoring disturbed mined land is challenging since the outcomes of various rehabilitation procedures on mined sites in terms of vegetation structure, composition and ecological function are not presently understood, especially in the developing countries. This study examined the mechanism of biodiversity recruitment, especially on structural attributes of an undisturbed forest community and rehabilitated forests of different ages on sites disturbed by coal-mining operations at Tanjung Enim, South Sumatra. Un-mined forest was characterized by complex structural features including a dense stand of trees in a range of sizeclasses, an almost closed canopy, and a shrubby understorey. In contrast, young mined sites were characterized by a low density of woody stems, a relatively open canopy and herbaceous ground cover. Soil characteristics of rehabilitated site were progressing towards the reference site. The marked differences in structural complexity between unmined and mined sites suggest that it will take very long time for the mined sites to recover into their original conditions. So, more restoration intervention will be needed to speed the recoveryprocesses.
 Key words: restoration, mining, biodiversity, structural complexity.INTRODUCTIONRehabilitation of disturbed areas due to miningactivities is intended to assist the environment in returningto a stable and sustainable land use as soon as possible(Bell 1996; Parker 1997). The nature of the post-miningland use will depend on a number of factors including theecological potential of the mined environment and thewishes of the neighboring society. Currently, in Australia,many mining operations are using native plant species inrehabilitation programs leading to the establishment ofpastures and forests (Bell 1996, 2001; Gardner 2001),however in Indonesia, mining operators are mostly usingfast growing exotic species in their rehabilitation(Suhartoyo 2008), as in many other countries al around theworld (Martínez-Ruiz et al. 2007; Alday et al. 2010).As more mine operators need to establish their postmining plan

Stop the bullying in the corridors: Can including shrubs make your revegetation more Noisy Miner free?

Summary Noisy Miners (Manorina melanocephala) are aggressive Australian honeyeaters that dominate many areas of remnant vegetation and forest edges from which they competitively exclude small birds. A similar domination can also occur in planted wildlife corridors. The aim of this study was to determine which corridor plantings encouraged the presence of small native birds in regions where Noisy Miners dominate. Six vegetation mixes were investigated in the main study: eucalypts with and without shrubby understorey; acacia with and without shrubby understorey; exotic conifer; and exotic deciduous trees. A supplementary study then examined sites with a mixture of eucalypt and acacia trees with a shrubby understorey. The findings showed that Noisy Miners dominated corridors of eucalypts, virtually excluding small birds, whereas native acacias, exotic conifer and exotic deciduous corridors had small birds and no resident Noisy Miners. The greatest abundance and richness of small birds occurred in plantings combining eucalypts with at least 15% acacias, in this case bipinnate species. Given these results, it is recommended that eucalypt plantings should be supplemented with both acacias (preferably bipinnate) and a shrubby understorey.

Late Pleistocene megafauna site at Black Creek Swamp, Flinders Chase National Park, Kangaroo Island, South Australia

The occurrence of fossil vertebrate remains at Black Creek Swamp at the western end of Kangaroo Island, South Australia, along with reports of ‘primitive’ stone implements in the vicinity has, for more than seventy years, fuelled speculation that this site would reveal a definitive relationship between humans and megafauna. Radiocarbon dating in the 1970s and again in 2004 suggested accumulation at around the last glacial maximum, making it potentially the youngest megafaunal deposit in Australia. Our excavations produced no artefacts and no evidence of butchering. Taphonomic evidence indicates three phases of drought accumulation around an ephemeral water source. These droughts may have been induced by climate, sinkhole drainage, or both. The fauna includes 29 species; one third of the species are extinct. This component is represented by browsing herbivores and their putative predator, Thylacoleo carnifex. The extant species indicate a mosaic of habitats including open sclerophyll forest, grassy patches, areas of shrubby understorey and semi-permanent water sources. The occurrence of two dwarfed species is suggestive of isolation and resource depletion. Multiple dating techniques (OSL, ESR, U-series and C) revealed a complex geochemical history for this site. New age estimates place the fossil accumulation between 110 and 45 ka.

Development of forest structure on cleared rainforest land in eastern Australia under different styles of reforestation

Rainforests in eastern Australia have been extensively cleared over the past two centuries. In recent decades, there have been increasing efforts to reforest some of these cleared lands, using a variety of methods, to meet a range of economic and environmental objectives. However, the extent to which the various styles of reforestation restore structure, composition and ecological function to cleared land is not presently understood. In this study, we develop and apply a method for quantifying the structural attributes of reforestation sites in tropical and subtropical Australia. The types of reforestation studied were plantation monocultures, mixed-species cabinet timber plots, diverse restoration plantings and unmanaged regrowth. Two age classes of reforestation were examined: ‘young’ (5–22 years), incorporating sites from all categories, and ‘old’ (30–70 years), in which only monoculture plantations and regrowth were represented. A total of 104 sites were surveyed including reference sites in intact rainforest and pasture. Intact rainforest was characterised by a suite of complex structural features including abundant special life forms (vines, epiphytes, hemi-epiphytes and strangler figs), a dense stand of trees in a range of size classes, a closed canopy, a shrubby understorey and a well-developed ground layer of leaf litter and woody debris. These features were lost on conversion to pasture. While all types of reforestation returned some elements of structural complexity to cleared land, young plantation monocultures, cabinet timber plots and young regrowth had a relatively simple structure. These sites typically had a low density of woody stems, a relatively open canopy and grassy ground cover, and lacked large trees, coarse woody debris and most special life forms. Restoration plantings and old regrowth were more complex, with a high density of woody stems, a relatively closed canopy and shrubby understorey. Old monoculture plantations in the tropics had acquired many of the structural attributes of intact forest, however this was not the case in the subtropics, where plantations were subject to more intensive management. The marked differences in structural complexity between sites suggest that the different types of reforestation practiced in eastern Australia are likely to vary considerably in their value as habitat for rainforest biota.

The vegetation and flora of Deal Island, Kent Group

There are eight formations mapped for Deal Island comprising forests and woodlands, scrub, sedgeland,grassland and a coastal complex. Tussock grassland, which results from burning and clearing of Allocasuarina forest, occurs on the limestone soils, while the soils formed directly over granite are clothed with Eucalypt-dominated scrub and woodland with a healthy or shrubby understorey. A total of 176 plant taxa are recorded, of which only two are Tasmanian endemics. About one-quarter of the flora comprise exotic species. A distinct Bassian floristic element is present, which includes some Eremean flora.

Community associations and structure in the Late Cretaceous vegetation of southeast Australasia and Antarctica

The structure and species richness of the Late Cretaceous (Santonian-Maastrichtian) vegetation in the Otway Basin, southeast Australia is reconstructed based on knowledge of palaeolatitudes, palaeotemperatures, plant taxa identified from fossil spores and pollen, and ecophysiological relationships established for present-day ecosystems. The vegetation, which grew at palaeolatitudes of 60–65°S and at mean annual palaeotemperatures of 16.5–19°C, comprised tall open-forests (Foliage Projective Cover 60–70%, height about 30 m) containing austral conifer and proteaceous taxa having coriaceous, notophyll-sized leaves. Today the taxa ( Podocarpus, Dacrydium, Dacrycarpus, Knightia, Gevuina, Macadamia) from a minor component of upland closed-forests (usually termed rainforests) of tropical northeast Australia and New Caledonia. A conical-shaped crown to the trees of the tall open-forests situated in high latitudes during the Cretaceous would enable some light to penetrate the canopy to a shrubby understorey (of Proteaceae, Winteraceae, Trimeniaceae, Nothofagus, and Ilex) and a ground stratum of diverse cryptogams. On nutrient-poor, waterlogged sites fringing the forest, sclerophyllous leaved taxa ( Adenanthos, Stirlingia, Epacridaceae, and possibly Beauprea) developed, with wetland swamps of Callitriche, ferns and some epacrids. In cooler localities in New Zealand and Antarctica, the productivity of the forests would have been greater, and the canopy taxa mainly with coriaceous, microphyll-sized leaves. Austral podocarps and Proteaceae occurred in the canopy of New Zealand forests, whereas the canopy of Antarctic forests contained podocarps and Nothofagus.

Effects of fire on the bird communities of tropical woodlands and open forests in northern Australia

Abstract Birds were censused at 24 plots which had been subjected to 14 years of four experimental fire regimes (fire‐exclusion, annual early burn, annual late burn and biennial burn) in Eucalyptus open forest and woodland at Munmarlary, Northern Territory. In addition, short‐term responses of birds to fire at a savannah woodland site near Katherine were examined. At this site patches of the study area were burnt in April, June and August 1987, and birds were censused monthly over the period April to October 1987.Many bird species were attracted to areas that had been recently burnt. These were mostly granivorous species, and omnivorous and carnivorous species which fed on the ground. Influxes of these species occurred because fires increased accessibility to food by clearing the ground of its previous dense grass layer. Succession of bird species to long‐unburnt areas was relatively limited, although species which fed or nested in the shrubby understorey occurred at greater densities in such areas. Frugivorous birds may become more common in areas protected from fire, thereby driving succession to monsoon vine forests from Eucalyptus forests, though, in terms of current fire regime, this process may be prohibitively slow.The hot fires of the mid to late Dry season may be less beneficial to granivores than the cooler fires typical of the early Dry. Accordingly, recent changes in the fire regime may have contributed to the decline of some bird species.

Odour movement, wind direction, and the problem of host‐finding by tsetse flies

ABSTRACT. Movement of host odour was modelled in natural tsetse habitats with smoke and ultra‐light 7‐cm‐long wind vanes; the speed and direction of the air movements were analysed from video recordings thereof. Wind of <1 ms‐1 did not move in straight lines, since large packets of air (>10 m across) often changed direction together. The rate of this change of direction (meander) correlated negatively with windspeed. In open woodland with a shrubby understorey (in which windspeed was reduced by a factor of >5 from that above the canopy, to ax 0.3 m s‐1), this wind meander fell by 2d̀ s‐1 change of direction for each 0.1 m s‐1 increase in windspeed (r2=0.96). Over open ground without shrub cover, the meander fell by 0.5d̀ s‐1 per 0.1 m s‐1 increase in windspeed (r2=0.85). In both situations, such meandering virtually ceased in winds of > 1 m s‐1. In woodland, the relationship between the direction of air movement near the surface of bare earth (one potential tsetse landing site) and that c. 0.5 m above ground level (flight height) was often weak (r2=0.2‐0.4), but this problem would be reduced if the fly averaged the ground‐level wind for at least 30 s. Odour (smoke) travelling from a source 15 m ‘upwind’ over open ground arrived at a notional tsetse fly for 80% of the time from a direction within 10d̀ of the true source direction. In typical tsetse woodland, however, the ‘odour’ arrived from all directions (including >90d̀ away from the source), with only a 30% bias towards the true source direction (±10d̀). Evidently, tsetse must navigate up odour plumes by means that get round these difficulties‐simple, moth‐type upwind anemotaxis alone seems unlikely to be adequate.

Birds in a Tropical Mosaic - the Distribution of Bird Species in Relation to Vegetation Patterns

Wilson and Bowman (1986) classified and mapped vegetation in a complex mosaic at Howard's Peninsula, Northern Territory. The relationship of bird distribution to this vegetation classification was considered through 10 repeat censuses of 5 replicate quadrats in each of 20 vegetation units. Censusing period was April-May. 118 bird species were recorded. Closed forests (3 units), mangroves (2 units) and swamplands (3 units) all had distinctive bird species compositions, but bird species showed a relatively poor relationship with the classification of woodland and grassland units. Eucalyptus woodlands regrowing after devastation by a cyclone in 1974 had similar bird species diversity and density to undamaged woodlands, though somewhat different bird species composition. Eucalyptus woodlands with a dense shrubby understorey had significantly greater bird density and species diversity than those with open or grassy understories and their bird species composition showed appreciable association with that of closed forests. Closed forest and, less so, mangrove units had highest diversity and density (despite their relatively small proportion in the study area and in the region generally), probably because they offered a wider range of foraging possibilities.

Distribution and Aspects of the Biology of the Parma Wallaby, Macropus parma, in New South Wales

M. pauma, which was formerly thought to be extinct in Australia, has been found in the Great Dividing Range of coastal New South Wales between 29D 28' and 32D 23's. The optimum habitat appears to be areas of wet sclerophyll forest with a thick shrubby understorey in association with grassy areas. Although the species may be locally common, its present status is best defined as rare; it has a limited distribution and normally occurs at a low density throughout its range. Limited data indicate that most young are born between February and June. Two of six females examined were probably in embryonic diapause. Females may mature sexually as early as 12 months old, and at a weight of 2.6-2.8 kg. Adult females in Australia were significantly heavier than those in New Zealand (Kawau I.), and larger in seven external body measurements. In contrast, adult males were significantly larger in Australia than Kawau I. in ear length only. The species is mainly nocturnal and the mean group size is 1.34 animals, i.e. it is usually single individuals that are encountered.

Detection of Die-Back Disease in the Brisbane Ranges by Aerial Photography

Black and white panchromatic and colour infrared aerial film were used to detect areas of diseased forest in the Brisbane Ranges, Vic., Australia. Two extensive areas of damaged forest were detected. Subsequent ground surveys revealed that the first was a seasonal defoliation due to insect attack, while the second was characterized by death of both the eucalypt overstorey and the shrubby understorey caused by Phytophthora cinnamomi.