Damian Michael

REPTILE AND ARBOREAL MARSUPIAL RESPONSE TO REPLANTED VEGETATION IN AGRICULTURAL LANDSCAPES

We report reptile and arboreal marsupial responses to vegetation planting and remnant native vegetation in agricultural landscapes in southeastern Australia. We used a hierarchical survey to select 23 landscapes that varied in the amounts of remnant native vegetation and planted native vegetation. We selected two farms within each landscape. In landscapes with plantings, we selected one farm with and one farm without plantings. We surveyed arboreal marsupials and reptiles on four sites on each farm that encompassed four vegetation types (plantings 7-20 years old, old-growth woodland, naturally occurring seedling regrowth woodland, and coppice [i.e., multistemmed] regrowth woodland). Reptiles and arboreal marsupials were less likely to occur on farms and in landscapes with comparatively large areas of plantings. Such farms and landscapes had less native vegetation, fewer paddock trees, and less woody debris within those areas of natural vegetation. The relatively large area of planting on these farms was insufficient to overcome the lack of these key structural attributes. Old-growth woodland, coppice regrowth, seedling regrowth, and planted areas had different habitat values for different reptiles and arboreal marsupials. We conclude that, although plantings may improve habitat conditions for some taxa, they may not effectively offset the negative effects of native vegetation clearing for all species, especially those reliant on old-growth woodland. Restoring suitable habitat for such species may take decades to centuries.

The combined effects of remnant vegetation and tree planting on farmland birds.

Biodiversity conservation on agricultural land is a major issue worldwide. We estimated separate and joint effects of remnant native woodland vegetation and recent tree plantings on birds on farms (approximately 500-1000 ha) in the heavily cleared wheat and sheep belt of southern Australia. Much of the variation (>70%) in bird responses was explained by 3 factors: remnant native-vegetation attributes (native grassland, scattered paddock trees, patches of remnant native woodland); presence or absence of planted native trees; and the size and shape of tree plantings. In terms of the number of species, remnant native vegetation was more important than tree planting, in a 3:1 ratio, approximately. Farms with high values for remnant native vegetation were those most likely to support declining or vulnerable species, although some individual species of conservation concern occurred on farms with large plantings. Farm management for improved bird conservation should account for the cumulative and complementary contributions of many components of remnant native-vegetation cover (e.g., scattered paddock trees and fallen timber) as well as areas of restored native vegetation.

Contrasting mammal responses to vegetation type and fire

The response of terrestrial mammals and arboreal marsupials to past burning history as well as a year prior to, and then for 4 years after, a major wildfire in 2003 at Booderee National Park, Jervis Bay Territory was quantified. The present study encompassed extensive repeated surveys at a set of 109 replicated sites stratified by vegetation type and fire history. It was found that most species exhibited significant differences in presence and abundance between major vegetation types. Detections of long-nosed bandicoot (Perameles nasuta) increased significantly in all vegetation types surveyed, in both burnt and unburnt areas. Temporal patterns in captures of three species of small mammals (bush rat (Rattus fuscipes), swamp rat (Rattus lutreolus) and brown antechinus (Antechinus stuartii)) showed a trend for lower numbers of captures on burnt sites compared with unburnt sites. Three species of arboreal marsupials, common ringtail possum (Pseudocheirus peregrinus), greater glider (Petauroides volans) and common brushtail possum (Trichosurus vulpecula), were moderately common and all showed marked differences in abundance between vegetation types. Whereas P. peregrinus and P. volans exhibited a temporal decline between 2003 and 2006, T. vulpecula exhibited a general increase from 2003 levels. However, arboreal marsupial responses did not appear to be directly fire related.

TEMPORAL CHANGES IN VERTEBRATES DURING LANDSCAPE TRANSFORMATION : A LARGE-SCALE NATURAL EXPERIMENT

Plantation development is a significant form of landscape change worldwide. We report findings from a large-scale longitudinal natural experiment that quantified changes in Australian vertebrates as a former grazing landscape was transformed to one dominated by a radiata pine (Pinus radiata) plantation. The study included four main “treatments”: woodland remnants surrounded by emerging radiata pine (52 sites, termed “woodland treatments”), stands of radiata pine (10 sites, “pine controls”), woodland remnants where the surrounding landscape remained unchanged (56 sites, “woodland controls”), and paddocks with scattered woodland trees that surrounded the 56 woodland remnants (10 sites, “paddock controls”). In our study region, woodland is distinguished from forest by differences in tree height, tree spacing, bole length, and canopy development. Between 1998 and 2006, occupancy rates of “woodland treatments” by most mammals and reptiles increased linearly. Similar trends occurred in the “woodland controls,” suggesting that species had increased landscape-wide, rather than displaying year × treatment interaction effects. We cross-classified birds according to the statistical significance and nature of time trajectories. Groups included those that: (1) declined in woodland treatments in comparison with woodland controls, (2) decreased within woodland treatments but increased in woodland controls, (3) declined across the entire study area, (4) increased within woodland treatments in comparison with woodland controls, (5) increased within woodland treatments but declined in woodland controls, and (6) increased across the entire study area. Attributes of woodland treatments significantly associated with temporal changes in bird occupancy included: (1) age of surrounding pine stands; (2) number of boundaries with surrounding pines; (3) size of the woodland patches; (4) dominant vegetation type of woodland patches; and (5) temporal changes in vegetation structure in the woodland treatments. Bird species associated with open country and woodland environments were disadvantaged by landscape transformation, whereas those that benefited were forest taxa and/or habitat generalists capable of inhabiting pine stands and adjacent woodland patches. Beyond this generalization, an unanticipated finding was a lack of association between life history attributes and landscape transformation. We suggest that several key processes are likely drivers of change at multiple spatial scales. Recognition of such processes is important for conservation in landscapes transformed by plantation expansion.

TESTING HYPOTHESES ASSOCIATED WITH BIRD RESPONSES TO WILDFIRE

Disturbance is a key ecological process influencing the distribution and abundance of many elements of the earths biota. Predicting the response of biota to disturbance is therefore important, but it nevertheless remains difficult to make accurate forecasts of response. We tested predictions from disturbance-related theories and concepts in 10 vegetation types at Booderee National Park (southeastern Australia) using a retrospective study of bird responses to fire history (over 35 years) on 110 sites and a prospective study following a single wildfire event in 2003 at 59 of these sites. Our data did not support predictions from the intermediate-disturbance hypothesis; observed bird species richness at a site was significantly (F(1,99) = 6.30, P = 0.014) negatively related to the number of fires since 1972 and was 8.7% lower (95% CI, 1.8-15.1%) for each additional fire. In contrast to fire history effects, we found that after the 2003 fire, the vast majority of individual species and the bird assemblage per se in most vegetation types recovered within two years. Thus, recovery after a single fire did not reflect long-term effects of multiple fires on overall bird species richness at a site. We postulated that the recovery of bird species richness and bird assemblage composition after the 2003 fire would be fastest in structurally simple vegetation types and slowest in structurally complex vegetation, but observed the opposite. Although observed bird species richness in vertically heterogeneous forest and woodland had returned to prefire levels by 2006, bird species richness in structurally simple vegetation types (e.g., sedgeland) had not. Postfire vegetation regeneration, together with a paucity of early-successional specialists, would explain the speed of recovery of the bird assemblage and why it changed relatively little during our investigation.

Not All Kinds of Revegetation Are Created Equal: Revegetation Type Influences Bird Assemblages in Threatened Australian Woodland Ecosystems

The value for biodiversity of large intact areas of native vegetation is well established. The biodiversity value of regrowth vegetation is also increasingly recognised worldwide. However, there can be different kinds of revegetation that have different origins. Are there differences in the richness and composition of biotic communities in different kinds of revegetation? The answer remains unknown or poorly known in many ecosystems. We examined the conservation value of different kinds of revegetation through a comparative study of birds in 193 sites surveyed over ten years in four growth types located in semi-cleared agricultural areas of south-eastern Australia. These growth types were resprout regrowth, seedling regrowth, plantings, and old growth. Our investigation produced several key findings: (1) Marked differences in the bird assemblages of plantings, resprout regrowth, seedling regrowth, and old growth. (2) Differences in the number of species detected significantly more often in the different growth types; 29 species for plantings, 25 for seedling regrowth, 20 for resprout regrowth, and 15 for old growth. (3) Many bird species of conservation concern were significantly more often recorded in resprout regrowth, seedling regrowth or plantings but no species of conservation concern were recorded most often in old growth. We suggest that differences in bird occurrence among different growth types are likely to be strongly associated with growth-type differences in stand structural complexity. Our findings suggest a range of vegetation growth types are likely to be required in a given farmland area to support the diverse array of bird species that have the potential to occur in Australian temperate woodland ecosystems. Our results also highlight the inherent conservation value of regrowth woodland and suggest that current policies which allow it to be cleared or thinned need to be carefully re-examined.

The use of nest boxes by arboreal marsupials in the forests of the Central Highlands of Victoria

The results are reported of a nest-box study conducted in two locations in the mountain ash (Eucalyptus regnans) forests of the Central Highlands of Victoria (south-eastern Australia) to compare usage of different nest-box designs located at different heights in trees. A total of 96 nest boxes was established using a rigorous experimental design – two regions (Powelltown and Toolangi State Forests), two forest age classes (20-year post-logging regrowth and 60-year fire- and salvage-logging regrowth), two nest-box designs (large boxes with large entrance holes and small boxes with small entrance holes), and two heights at which nest boxes were attached to trees (3 m and 8 m above the ground). The study entailed setting out four nest boxes at each of 24 sites to meet the design criteria. Evidence of occupancy by vertebrates was recorded in a total of 19 of 96 boxes on 11 of 24 sites site during regular inspections over more than three years. Thirteen boxes were used by Leadbeaters possum (Gymnobelideus leadbeateri), six by the mountain brushtail possum (Trichosurus cunninghami) and seven by the common ringtail possum (Pseudocheirus peregrinus). The common ringtail possum and mountain brushtail possum were seen only in high–large boxes but Leadbeaters possum used all but the low–large boxes. There was evidence of spatial dependence in usage patterns, with all four boxes at a given site showing signs of eventually being occupied. Only two nest boxes located in mountain ash forest regenerating after the 1939 wildfires were occupied. Relatively limited use of nest boxes supports concerns about the use of a nest box over large scales and long timeframes as an effective recovery tool for species threatened by the loss and subsequent shortage in the numbers of naturally occurring hollows.

Cross‐sectional vs. longitudinal research: a case study of trees with hollows and marsupials in Australian forests

How different are insights based on cross-sectional studies from those of longitudinal investigations? We addressed this question using a detailed case study encompassing a rare suite of inter-connected cross-sectional and longitudinal investigations that have spanned the past two decades and included work on: (1) the decay and collapse of large-cavity forest trees (termed “trees with hollows”), (2) populations of a suite of species of arboreal marsupials that are reliant on trees with hollows as nesting and denning sites, and (3) relationships between the abundance, type, and condition of trees with hollows and the presence, abundance, and species richness of these animals. Our case study was from the montane ash eucalypt forests of the Central Highlands of Victoria, southeastern Australia. Our longitudinal studies led to new insights that either would not have been possible from a cross-sectional study, or which were unexpected because they did not conform, or only partially conformed, to postulated res...

Experimental evidence of the effects of a changed matrix on conserving biodiversity within patches of native forest in an industrial plantation landscape

We implemented a replicated before-after-control-impact (BACI) experiment to quantify vertebrate response in native forest patches to a major change in the surrounding exotic Radiata Pine (Pinus radiata) plantation. We contrasted vertebrate occupancy of patches of native eucalypt forest where the surrounding stands of exotic Radiata Pine (Pinus radiata) were clearfelled (termed “treatment patches”) with matched “control patches” where surrounding pine stands remained unlogged. Different species of arboreal marsupials varied in their response to our experimental treatments. The Common Ringtail Possum was unaffected by cutting of the surrounding pine stands, whereas all sightings of the Mountain Brushtail Possum were in control patches. For birds, species richness was significantly reduced by 4–9 species in treatment patches. Birds with cup and dome nests were those negatively affected by the cutting of the surrounding pine stands. They may be susceptible to altered microclimatic conditions or increasing levels of nest predation when the surrounding pine matrix is clearfelled. Our study emphasized how the biota inhabiting retained patches of native forest within plantation landscapes can be changed when stands of surrounding Radiata Pine are clearfelled. In the case of birds, more species will be maintained within eucalypt patches if logging is scheduled so that not all the surrounding pine plantation is clearfelled at once.

Enhancing fauna habitat in grazed native grasslands and woodlands: use of artificially placed log refuges by fauna

To assess whether faunal habitat can be enhanced by using artificial refuges, and whether different species preferentially use refuges with differing structural characteristics, we monitored faunal usage of artificially placed log refuges in grazed semi-arid grasslands and woodlands in Terrick Terrick National Park in Victoria. In total, 1131 log refuges were placed at 91 sites across major vegetation types in the reserve. The effect of refuge age was assessed by comparing faunal usage between new refuges and 271 old refuges that had lain in situ for more than 15 years. Refuges were surveyed for fauna monthly between June 2000 and January 2001. Different species preferred refuges with different characteristics. Overall terrestrial fauna, and three native species (Diplodactylus tessellatus, Morethia boulengeri and Suta suta) in particular, were significantly more abundant beneath old refuges, whereas the introduced Mus musculus was significantly more abundant beneath new refuges. Five species (Crinia signifera, Morethia boulengeri, Menetia greyii, Sminthopsis crassicaudata and Suta suta) were significantly more abundant beneath Eucalyptus logs that were large, wide, partially decayed, contained many holes and/or covered many subterranean invertebrate holes. This study demonstrates the effectiveness of installing log refuges in grassy landscapes as a survey method for vertebrate fauna and as a potential habitat-restoration technique to help conserve grassland fauna.