Clearfell Harvesting Research Articles

The importance of exotic plantation forest for the New Zealand long-tailed bat (Chalinolobus tuberculatus)

Environmental certification schemes have stimulated increasing interest in biodiversity and its management within exotic plantation forests. These schemes expect management to be scientifically-based, even though little is known about how often, or which, native species use exotic plantation forests. Greater knowledge of the ecology of native species within exotic plantation forests is required to advise management and reduce risks to native species, particularly those that are rare, such as the New Zealand long-tailed bat (Chalinolobus tuberculatus). Long-tailed bats use exotic plantation forests throughout New Zealand but need protection from the impacts of forest management, and particularly clear-fell harvest, that is achievable only through a better understanding of their biology. The consequences of the current reduced re-planting, and the conversion of plantation forests into pasture resulting in smaller forested areas, should not be ignored because they may be associated with reductions in long-tailed bat populations. We review the current knowledge of long-tailed bats' use of exotic plantation forests, and report for the first time which exotic plantations long-tailed bats are known to use. We make recommendations for the design of monitoring programmes to detect long-tailed bats within plantation forests, and for research into the effects of forest management, especially logging, and comment on the likely impacts of reductions in forested areas on long-tailed bats.

A value basis for the social acceptability of clearfelling in Tasmania, Australia

In this research, the basis for social acceptability judgements of clearfell harvesting in people's values and beliefs was explored. During an initial qualitative field study the value orientations, valued objects and beliefs about consequences of 18 participants were identified. A hypothesis was then developed drawing on two cognitive hierarchy theories: the Theory of Reasoned Action and Value Belief Norm Theory. It was predicted, that in judging clearfelling people would draw on value orientations toward the natural environment. These would lead them to value objects in the forest and to develop beliefs about the consequences of harvesting for those objects, which would in turn lead to acceptability judgements. In a second study approximately 560 Tasmanians were shown images of a clearfell, burn and sow management system and asked to judge its acceptability. On average, industry-affiliated participants rated clearfelling much more acceptable than did non-affiliated and conservation-affiliated participants. Participants also responded to questions that measured the four levels on the cognitive hierarchy. Structural equation modelling was used to test whether these data were consistent with the cognitive hierarchy model. There was no basis to reject the model.

Clear-fell harvest impacts on biodiversity: past research and the search for harvest size thresholds

Clear-fell harvesting has large aesthetic impacts and significantly alters ecosystem attributes at multiple spatial scales. Known abiotic changes include increased microclimatic variability, changes in regional water balance, and modified hydrological patterns that influence erosion processes. Biotic changes include increased species richness immediately post-clear-felling due to shifts in species composition resulting from changes in individual species abundance and colonization by disturbance-adapted or open-habitat species. Given the large ecological changes caused by clear-fell harvesting and the negative public perception of clear-felling, it is surprising that few studies have investigated whether reducing clear-fell harvest area may be a viable strategy to mitigate ecological change within individual clearcuts. Clear-fell size studies conducted to date rarely exceed a maximum harvest area of 10 ha, and biotic communities measured exhibit mixed responses with respect to species richness and other biodiversity attributes with increasing clear-fell size. Some postharvest ecological responses are nonlinear with respect to harvest area and suggest possible threshold sizes beyond which clear-fell impacts increase disproportionately to their size. Conceptual models of potential ecological thresholds in clear-fell harvest impacts are discussed, as is the need for rigorous empirical testing to ensure a solid foundation exists for forest harvesting guidelines.

Managing Plantation Forests to Provide Short- to Long-Term Supplies of Wood to Streams: A Simulation Study Using New Zealand’s Pine Plantations

Riparian functions such as the recruitment of wood to streams take decades to recover after a clear-fell harvest to the stream edge. The implications of two sets of riparian management scenarios on the short- and long-term recruitment of wood to a hypothetical stream (central North Island, New Zealand) were compared through simulation modeling. In the first set (native forest buffer), a designated tree-less riparian buffer was colonized by native forest species after a pine crop (Pinus radiata) had been harvested to the stream bank. In the second set (pine to native forest buffer), native forest species were allowed to establish under the pine canopy in a designated riparian buffer. In general, the volume of wood was greater in streams with wider buffers (5-m to 50-m) and this effect increased with forest age (800 years). The pine to native forest buffer supplied more wood to the stream more quickly, and matched the long-term supply to the stream from the native forest buffer. For the native forest buffer, total wood volume was minimal for the first 70 years and then increased uniformly for the remainder of the simulation. In contrast, the pine to native forest buffer produced a bimodal response in total wood volume with the initial sharp peak at year 100 attributed to pine recruitment and a second more gradual peak lasting for the rest of the simulation, which was similar to levels in the native forest simulations. These results suggest that existing plantations could be an important source of wood to the stream during the first 100+ years of native forest development.

Decline in tree-fern abundance after clearfell harvesting

Common and widespread plant species can change in abundance as a result of timber harvesting practices, with potentially broad effects on an ecosystem. Yet few studies have quantified such changes and their effects and as a result, subsequent management can be poorly defined. Tree-ferns are among a number of vegetative resprouters that have been shown to decline in abundance after clearfelling in Victorian Wet Forest. This study quantifies the initial survival of two common species of tree fern, Dicksonia antarctica and Cyathea australis, on six Wet Forest coupes in the Victorian Central Highlands, south-eastern Australia. Sixteen percent of the 2391 tree-ferns monitored remained alive 1 year after clearfelling and seedbed preparation, with only 5% remaining in an upright position. Mortality was still increasing up to 6 years after clearfell harvesting, particularly for C. australis. Sixty-seven percent of D. antarctica surviving to 1 year post-harvest were still alive after 4 or 6 years, whereas only 35% of C. australis survived this period. Low tree-fern survival is likely to result in declines in the abundance of other species that rely directly on tree-ferns for habitat. The altered forest structure resulting from reduced tree-fern numbers will affect local microclimates and forest processes. As tree-fern recruitment is low and growth rates are slow, these changes are likely to be long term. Survival of individuals through harvesting operations is crucial to the maintenance of the role of tree-ferns as a keystone species in Wet Forests and simple modifications to current practices could increase the survival of tree-ferns in clearfelled areas.

Does clearfell, burn and sow silviculture mimic the effect of wildfire? A field study and review using litter beetles

The ecological effects of clearfell harvesting followed by high intensity burning are sometimes thought to mimic wildfire, the major natural disturbance regime in Tasmanian wet forests. We investigated whether the litter-inhabiting beetle populations in logged and burnt regeneration forest resembled those in forest regenerating following natural wildfire. Pitfall trapping and habitat assessment were conducted at three pairs of adjacent 33-year-old logging and wildfire regeneration sites. In total, 6128 beetles were collected, representing 179 morphospecies in 30 families. The beetle assemblages in logging and wildfire treatments could not be distinguished. However, beetle populations did differ subtly between sites. One Aleocharinae (Staphylinidae) morphospecies and one Carabidae species were more abundant at one of the three site pairs. Multivariate analyses of common species indicated that the litter beetle assemblages differed significantly between sites, and this was partially related to their degree of geographical separation. Environmental factors considered indicative of logging impacts did not differ between wildfire and logging regeneration treatments. Temporal and landscape scale differences between logging and the natural disturbance regime and changes to logging practices since these study sites were harvested may have negative impacts on litter beetles in the future. Changes to current harvesting practices are recommended to better mimic the natural disturbance regime and thus improve conservation of forest biodiversity.

Effects of site preparation on runoff, erosion, and nutrient losses from Pinus plantations established on the coastal lowlands of south-east Queensland, Australia

Site preparation practices used during establishment of second rotation Pinus plantations on the coastal lowlands of south-east Queensland became more conservative during the 1990s. Traditionally, site preparation included stick raking of residue into windrows, followed by burning. Areas subject to periodic saturation were then cultivated to form continuous high mounds, while better drained sites were contour strip cultivated. These practices were replaced by retention of residue biomass on hillslopes. Similarly, intensive site disturbance was increasingly replaced by tillage of the immediate planting zone only and, as far as possible, avoidance of continuous furrows, major drainage structures, and high mounding works. In the study reported here, simulated rainfall and overland flows were used to assess the impacts of the earlier, less-conservative site preparation practices on hillslope soil loss, nutrient loss, and the potential for off-site nutrient movement.Where residue from clearfell harvesting of the first rotation was not removed, runoff, erosion, and nutrient loss were negligible. Harvesting tended to distribute residue widely across hillslopes, and, together with naturally occurring understorey biomass, it formed a largely continuous groundcover. Highest concentrations of sediment in overland flow were recorded for hillslopes in the newly stick-raked condition. Sediment concentrations in overland flows applied to properly designed and constructed high mounds were low, even for large flows simulating relatively long furrow lengths. However, sediment in rainfall-induced runoff from mounded areas was observed to be nutrient enriched, indicating potential for an off-site nutrient pollution risk, at least prior to establishment of grass cover along furrows. Nutrient enrichment was correlated with enrichment of finer size classes of sediment in runoff.The work reported in this paper vindicated the move away from traditional residue removal and site preparation practices to an approach based on residue retention, minimum site disturbance, and, wherever possible, ‘spot’ rather than continuous mounding/cultivation.

Regeneration of Wet Forest flora a decade after clear-felling or wildfire - is there a difference?

There is increasing recognition of the importance of ecologically sustainable forest management, including forest biodiversity conservation. Knowledge of the effects of forest practices on flora values can be gained by comparing the floristics of natural and harvested forest stands at the same stage of development. This paper presents the results from a comparative study of natural and managed forest regeneration in Eucalyptus regnans F.Muell dominated forests in the Victorian Central Highlands. The vascular floristics about a decade after clear-fell harvesting operations differed significantly from the floristics of similarly aged forest regenerating after wildfire. In clear-felled areas, weed and sedge species occurred more frequently than on wildfire sites and Acacia dealbata Link was much more abundant, whereas resprouting shrubs, tree ferns and most ground-fern species were more abundant in wildfire regeneration. The low survival rate of resprouting species reported in an increasing number of studies suggests that soil disturbance is likely to be a major contributor to differences. The floristics of sites burned by intense wildfire differed significantly from those subjected to less intense wildfire, indicating that considerable variation in floristics can occur under a natural disturbance regime. The failure of the clear-fell regeneration to fit within this broad natural variability suggests that clear-fell harvesting alters the natural regeneration processes. As species composition in these forests is largely determined by the initial floristic composition after disturbance, this paper provides evidence that some clear-felled regrowth forests may remain different in structure and composition to forests regenerating after natural disturbances.

Management of compaction during harvest of Pinus plantations in Queensland: II. Preliminary evaluation of compaction effects on productivity

Summary Two retrospective studies were conducted in the coarse-textured, coastal lowland soils of south-eastern Queensland to provide a preliminary assessment of compaction affects on the productivity of Pinus plantations. In the first study, stem wood volume of a 9-year-old plantation established on a site used as a log dump during clearfell harvest of the first rotation was reduced by 40.3%. There was a clear link between persistent compaction, reduced root development and reduced wood production. Standard site preparation and cultivation operations used at the time of second rotation establishment did not ameliorate compaction damage. A number of operational measures are suggested for minimising the impact of log dumps on plantation productivity. In the second study, dendro-chronological techniques were used to determine annual basal area increments (BAIs) of crop trees following thinning operations that resulted in rut compaction of various intensities. The methodology allowed both positive growth responses to thinning and adverse growth responses from compaction to be identified. BAI reduction was most prominent in larger trees adjacent to rut compaction exceeding 10 cm depth. For example, BAI of trees with a 27.5 cm under-bark diameter adjacent to ruts 15 and 35 cm deep was reduced by 17% and 29% respectively compared to increment of those adjacent to ruts 0 cm deep. The study provides support for proscribing rut compaction exceeding 10 cm in depth.

Effects of Clearfell Harvesting on Lucanid Beetles (Coleoptera: Lucanidae) in Wet and Dry Sclerophyll Forests in Tasmania

The effects of commercial forestry harvest and regeneration practices (clearfelling and slash-burning) on the lucanid fauna of the wet sclerophyll forests of southern Tasmania and the dry sclerophyll forests of eastern Tasmania were examined using pitfall catches. Lucanids are saproxylic beetles, dependent on dead, moribund and decaying wood. Samples taken from old-growth forest and from a chronosequence of sites regenerating after logging, in each forest type, were used to compare the species richness and abundance of the lucanid assemblages. In both forest types, species richness and abundance was highest in the youngest regeneration sites (1–3 year), reflecting the species richness of the original and adjacent unlogged forest, lowest in the older (20–25 year) sites, and variable in the old-growth sites. TWINSPAN cluster analysis showed no clear distinction between regeneration and old-growth forest. The post-harvest slash and stump residue provided an important refugium and initial habitat, but our research indicates that some species may not maintain populations in the long term. Our results suggest that most species of lucanids will find a continuous supply of suitable habitat only in old-growth forests; and such species may become less common as clearfell harvesting leads to a replacement of heterogeneous old-growth forest with single-aged monospecific stands. Continuity of supply of wood in all decay stages, the maintenance of sufficient source areas, and biological connectivity between old-growth stands to enable dispersal, are all likely to be essential to maintain lucanid beetle community integrity. If similar principles apply to other saproxylic species of invertebrate, then clearfelling and slash-burning may cause a gradual extinction of an important element of the forest biota.