Simon J. Grove

The influence of forest management history on the integrity of the saproxylic beetle fauna in an Australian lowland tropical rainforest

Forest management in temperate and boreal regions is often based on a strong foundation of applied ecological research. Increasingly, this has allowed the needs of saproxylic (dead wood associated) insects to be addressed. However, there has been very little equivalent research in tropical forests, where saproxylic insect faunas are likely to be much richer and where forestry is usually subject to weaker environmental controls. This study compares the saproxylic beetle fauna of old-growth, selectively logged and regrowth rainforest in the Daintree lowlands of northeastern Queensland, Australia. Old-growth levels of abundance, species richness, assemblage composition and guild structure were not maintained in logged and regrowth forest, suggesting that intact assemblages may not survive in the long-term in managed tropical rainforest. However, retaining a continuous supply of commercially overmature trees in the managed stand may prevent a repeat of the widespread extinctions of saproxylic insects witnessed in temperate and boreal forest regions.

Extent and composition of dead wood in Australian lowland tropical rainforest with different management histories

Deadwood (coarse woody debris or CWD and dead standing trees or snags), is regarded as an important ecological component of temperate forests, yet its status in tropical forests has gone largely unreported. Its extent and composition was studied in a series of sites in the lowland rainforests of Australias Daintree region. The aim was to compare the amounts of CWD and snags in forests with historically different intensities of management: undisturbed old-growth, selectively logged and re-growth resulting from previous total clearance. 1671 individual pieces of CWD and 173 snags were recorded and measured at 81 sampling locations. Deadwood was very patchily distributed, and occurred at considerably lower levels than in most equivalent temperate or boreal forests. Old-growth forest generally contained slightly greater mass and volume of CWD, and significantly greater volumes in the larger size-classes (>40 cm diameter), than either logged or re-growth forest; snag volumes were so variable that no relationship with management history was detectable. Overall volumes of CWD ranged from 35.68 m3 ha−1 in old-growth to 20.16 m3 ha−1 in re-growth sites, with logged sites intermediate; for snags, volumes ranged from 27.00 m3 ha−1 in logged to 10.01 m3 ha−1 in re-growth, with old-growth intermediate. Overall deadwood size-class distribution was closely correlated with living tree stand structure across all nine study sites. CWD volume, especially that in larger size-classes, was correlated with basal area and with basal area contributed by trees in the larger size-classes. These in turn are linked to management history, reaching their highest values in old-growth sites and their lowest in re-growth. These results suggest that any management system that systematically reduces the proportion of larger trees will, over the longer term, affect the forests ability to generate deadwood, especially in the larger size-classes. The proportion of forest-dwelling species that are dependent on deadwood is unknown, but may be a fifth or more, with many associated only with the larger size-classes. Thus managing tropical rainforests according to ecologically sustainable principles requires a commitment to maintaining stand structures that allow the continued generation of deadwood in a full range of sizes.

Tree basal area and dead wood as surrogate indicators of saproxylic insect faunal integrity: a case study from the Australian lowland tropics

Abstract Saproxylic (dead wood associated) insects are well-known in Europe for their associations with the mature timber habitat (old trees and dead wood)—features which have a bearing on their response to forest management and which have encouraged their use as indicators of ecological continuity. In the tropics and elsewhere, their relationships with the mature timber habitat have yet to be characterised, preventing their consideration in determining the sustainability of forest management. Furthermore, the practical difficulties of adequately sampling a tropical saproxylic insect fauna may well preclude their consideration as indicators in their own right, in which case surrogate structural indicators will need to be sought. To investigate this, the saproxylic beetle fauna of lowland rainforest was studied in a series of sites in the Daintree region of northeast Queensland, Australia. Study sites were chosen to represent a range of intensities of past management from old-growth forest, through selectively logged forest to re-growth forest that had arisen following previous clearance. Beetle abundance, incidence, species richness and assemblage composition were considered in relation to various mature timber habitat attributes, comprising living tree basal area, coarse woody debris and standing dead trees. Volume of coarse woody debris proved the strongest positive correlate of species richness, while the basal area of larger-diameter trees proved a more robust indicator of abundance, incidence and assemblage composition, and was also correlated with species richness. Given its ease of measurement compared to recording dead wood or saproxylic beetles, the basal area of larger-diameter trees is considered an appropriate surrogate measure of saproxylic beetle faunal integrity in tropical rainforest. Given the wider ecological role of old trees in forest ecosystems, the development of locally-defined indicators based on larger-diameter trees for monitoring forest management is strongly encouraged.

Coarse woody debris, biodiversity and management: a review with particular reference to Tasmanian wet eucalypt forests

Summary This paper reviews the biodiversity conservation issues relating to management of coarse woody debris (CWD) in the wet eucalypt production forests of Tasmania, with particular emphasis on clearfell, burn and sow (CBS) silviculture and on fuelwood harvesting. CBS is the standard silvicultural system in these forests, while fuelwood harvesting, as currently proposed, would involve the recovery of a higher proportion of felled biomass than standard CBS, as well as some pre-existing CWD. Studies and practices from around the world are considered that have relevance to the temperate Australian forestry situation in general, and the Tasmanian situation in particular. The paper considers the ecological roles of CWD in natural forest ecosystems, emphasising its value as a key structural component and as habitat for biodiversity (especially invertebrates). Temporal continuity and spatial connectivity in supply of CWD, and presence of larger-diameter CWD, emerge as key factors determining community richness and composition. Whilst levels of CWD naturally fluctuate spatially and temporally in wet eucalypt forests, studies from northern temperate and boreal forests with similar dynamics demonstrate that, historically, management of native forests has tended to result in a gradual diminution of the CWD resource. Larger-diameter material is readily diminished through management, with potential consequences for dependent biodiversity. Suggested mitigation measures (landscape-level and coupe-level), to accommodate biodiversity concerns and avoid a long-term conservation management problem for forest managers in Tasmania, centre on two main concerns. One is the likelihood that current standard rotation lengths used in CBS are probably too short to allow for the recruitment of sufficient CWD to replace that which is lost through harvesting, regeneration burning and natural decomposition. The other concern is that fuelwood harvesting may significantly increase the impacts of CBS on biodiversity in general and on threatened species in particular.

An inordinate fondness for beetles

In this paper we consider the extent of our knowledge of global beetle diversity. Depending on the estimates adopted, some 70-95% of all beetle species remain to be formally described, and at the current rate of progress it could be more than 200 years until the task is completed. One of the reasons for this is the difficulty of adequately sampling tropical beetle faunas and thereby ensuring sufficient material is available to taxonomists for comparative studies. Despite this, recent years have seen significant advances in our understanding of beetle taxonomy, biology, ecology and biogeography, and we are now in a good position to apply this understanding to ecological and management issues. Saproxylic (dead-wood-associated) beetles are used to illustrate this latter point.

A decade of change in the saproxylic beetle fauna of eucalypt logs in the Warra long-term log-decay experiment, Tasmania. 2. Log-size effects, succession, and the functional significance of rare species

The first decade of sequential and cyclical sampling of the saproxylic beetles of twelve freshly felled Eucalyptus obliqua logs at Warra, Tasmania has allowed comparisons between larger-diameter mature and smaller-diameter regrowth log-classes and between successive sampling cycles and years; and consideration of the interplay between these two aspects. The two log-classes support different assemblages, with the mature log-class hosting consistently more species, more unique species, and proportionally more obligately saproxylic species. Assemblages change seasonally and year-to-year, demonstrating succession. While changes in the assemblages of mature and regrowth log-classes follow similar trajectories, they remain distinct at every point in time. These differences remain apparent when considering sub-sets of the assemblages based on the rarity of the species involved, their flightedness, saproxylicity and larval feeding guild. This study suggests a need to incorporate the conservation of coarse woody debris derived from mature trees into production forestry practices. There is a particular need to devise silvicultural and/or planning systems that cater for the retention and long-term recruitment of mature trees, since these are the only source of the larger-diameter logs that were identified in this study as having particular ecological value. Through continuing the Warra long-term log-decay experiment over the next century or more, a more complete picture of the saproxylic beetle fauna will progressively emerge, together with a better understanding of the management requirements of the fauna.

Moving with the times: baseline data to gauge future shifts in vegetation and invertebrate altitudinal assemblages due to environmental change

Abstract A long-term monitoring program has been established in Tasmania, Australia, as a Satellite Project for the International Biodiversity Observation Year (IBOY). This program aims to monitor distributional change in vegetation and fauna assemblages along an altitudinal gradient (70–1300 m) in response to climate change and other environmental events. Baseline data collected over a two-year period will be available for comparison with data collected in future decades. The vegetation varies with altitude and fire history. The rate of change in vegetation is not continuous along the altitudinal gradient, but is most rapid above 700 m and below the treeline at 1000–1100 m. Most vascular plant species reach the limit of their distribution within this zone. Despite their preliminary nature, the invertebrate data also display altitudinal and seasonal patterns. The treeline and the 700–1000 m zone again appear to be notable in terms of invertebrate distribution. While the composition of ground-based taxa may be closely related to the floristic composition of the vegetation (or its environmental drivers), the airborne invertebrate fauna appears to be more closely related to structural characteristics such as height and density. Of all taxa, the Coleoptera appear to be the best potential indicators across most altitudes and times. Although the current data provide a wealth of inventory and distributional information over altitude, their greatest potential value lies in long-term comparative information. Future sampling should focus not only on changes at and above the treeline, but also on the zone below this where many species are at their altitudinal limits and may be particularly sensitive to climate change.

Maintaining data integrity in insect biodiversity assessment projects

The success of projects involving assessment of insect biodiversity depends on many things, but one which is often overlooked is the maintenance of data integrity. This is an issue best considered from project conception, through the design phase to the completion of the sample, specimen and data processing phase. This paper considers some guiding principles and details some logical steps that will help avoid loss of data integrity.

Anders Lindhe, Tobias Jeppsson and Bengt Ehnström: Longhorn beetles in Sweden—changes in distribution and abundance over the last two hundred years

In recent years entomologists and ecologists have increasingly come to accept that if species’ occurrence data are not available online for instant downloading, they must no longer be relevant and can effectively be ignored as a research tool. This book provides a timely counterpoint to this all-too-pervasive view. Based on the meticulous collation of data from some 1,400 insect collectors past and present, and from published records, it presents an acrossthe-centuries view of changes in population size and distribution for the 118 species of longhorn beetle (Coleoptera: Cerambycidae) occurring in Sweden. The authors and editorial team, lead by Mats Jonsell, are to be commended for their vision and perseverance that led them to seeing this volume through to completion. It was no mean feat. Not only has it been published in English rather than Swedish, but much of it was accomplished by knowledgeable volunteers contributing their time and expertise to the greater good. They scoured collections of all the major and minor museums in Sweden and beyond, and transcribed pertinent details from thousands of datalabels for the longhorn beetle specimens they encountered. They personally contacted more than two hundred members of the Swedish Entomological Society, which elicited hitherto unavailable data from some 140 collectors. They trawled through all the relevant published sources they could get their hands on. In a country with such a venerable tradition of natural history study stretching back to the time of Carolus Linnaeus, translating old texts from Latin to English (via Swedish perhaps) was all part of the process. Finally they incorporated on-line records of red-listed species from the Swedish Species Information Centre. Rigorous data-cleaning then whittled down the number of unique records in their database to a ‘mere’ 57,000. Data collation was just the start. In analysing the records for trends in population size or distributional changes, the authors incorporated some really rather profound insights on the changing behaviour of collectors and the relationship between time and the decay of data integrity. Collectors have never collected beetles randomly. They favour particular geographic areas, particular species, or particular collecting techniques; and these preferences vary by collector and over time as fashions, transport, technology, taxonomy, ecological understanding and patterns of landuse change. Some species develop particular ‘charisma’, perhaps because of their very rarity or beauty, and so tend to be over-represented in collections compared to more mundane species. Some localities act as honey-pots for the less adventurous collectors, and are also over-represented in collections. The level of societal interest in collecting also waxes and wanes; and time itself leads to an inevitable attrition of collection and data integrity. In an attempt to level the playing-field among records, the authors considered all these factors, and more, in judiciously weighting their data. This has enabled them to present scatter-plots (with a moving-average trend line) that chart longterm population trends for almost every species. It has also enabled them to plot maps showing how the Swedish distribution of each species has changed over time. A later chapter synthesises the main findings. Perhaps surprisingly, long-term stability in population size and distribution is the norm, despite the momentous changes to Sweden’s landscapes over the past two hundred years. Yet intensive forestry and other land-use changes have taken their toll for quite a few species, which have become rarer as a result: this is particularly the case for those associated with forest fires or S. Grove (&) Division of Forest Management, Forestry Tasmania, GPO Box 207, Hobart, TAS 7000, Australia e-mail: simon.grove@forestrytas.com.au