Snig Tracks Research Articles

Soil protection with logging residues during mechanised harvesting of native forests in Tasmania: a preliminary study

Summary In Tasmania, Australia, mechanised forest harvesting operations often use ‘cording’ to limit soil disturbance. This means logs are laid across the snig tracks, perpendicular to the flow of traffic, providing a rigid barrier between the machinery and the ground surface. At the conclusion of harvesting, the cording material is lifted using an excavator and burnt on site. This latter procedure enhances soil nutrition through the ‘ash-bed’ effect, whilst increasing the area of seedbed available for forest regeneration. To date, the efficacy of cording in protecting soil values remains largely untested. The shallow and stony nature of many forest soils, and the presence of logging residues and cording material along snig tracks, make the investigation of soil physical properties difficult. In response, this study was undertaken to assess the effectiveness of cording by using forest regeneration (density of seedlings and seedling height) as an indicator of productivity along former snig tracks protected with cording. Available seedbed (%) and seedling form, including the incidence of browsing and disease, were recorded and key soil chemical properties (0–10 cm soil depth: organic carbon, total nitrogen and total phosphorus), were measured. In the absence of physical soil testing, the theoretical distribution and attenuation of machine loads by the cording are discussed. Forest regeneration along the former snig tracks was consistently inferior in quantity and quality compared to that of the untrafficked control areas. This was attributed largely to: (a) a reduction in the available seedbed (%) due to incomplete combustion of the cording material and retention of logging residues, both on the ground surface and mixed with the upper soil layers, and (b) poor growing conditions—the combined effects of lowered organic carbon, nitrogen and phosphorus concentrations along the former snig tracks. Operational recommendations based on this study include: (a) avoiding trafficking of bare ground during the construction of cording, (b) beginning with a layer of small—diameter material to help spread machine loads more evenly and (c) where appropriate, leaving permanent snig tracks.

Evaluation of the use of pre- and post-harvest bulk density measurements in wet Eucalyptus obliqua forest in Southern Tasmania

Abstract Criteria and indicators under the Montreal process are intended to provide a common framework for describing and evaluating progress towards sustainable forest management. In 1998 a nationally coordinated project was initiated to evaluate proposed Montreal indicators 4.1.d and 4.1.e and to provide advice to state agencies on how these indicators could be applied. Interim indicator 4.1.e quantifies ‘ Proportion of harvested forest area with significant change in bulk density of any horizon of the surface (0–30 cm) soil ’. Application and evaluation of this interim indicator was conducted as part of the Warra Silvicultural Systems Trial, in Tasmania, Australia. This forest was composed of wet mixed regrowth/mature Eucalyptus obliqua forest with a dense rainforest understorey. Pre-harvest soil sampling was conducted in four stands followed by post-harvest sampling at two of the sites. Pre-harvest sampling according to soil drainage class, showed that there was a high natural variation in bulk density within individual stands and between neighbouring stands. Post-harvest sampling was stratified according to major operational areas and disturbance classes, including snig tracks (major and minor), firebreaks, harvested and unharvested areas, landings and access roads. Forest harvesting substantially increased the variability of soil bulk density. Though moderate and severe disturbance of the snig tracks and firebreaks increased average soil bulk density, changes in soil bulk density were not uni-directional. Many of the post-harvest samples showed a marked decline in soil bulk density due to the incorporation of litter and slash in the upper soil layer. Bulk density changed most in the upper 0–100 mm layer of soil. Hence there is reasonable argument that monitoring changes in bulk density should be limited to this depth. This would substantially reduce the cost of replicate sampling to the 300 mm depth. The high natural variation found for soil bulk density and the fact that changes are not uni-directional means that it is unlikely that the interim indicator proposed can be implemented in a practical, sensitive and cost-effective manner in the forest type examined in this study.

Recovery of soil physical properties from compaction and soil profile disturbance caused by logging of native forest in Victorian Central Highlands, Australia

Soil profile disturbance and compaction can have a long-term detrimental impact on soil properties. Organic matter, macroporosity and bulk density was measured during 1989 and 1999 in three types of snig tracks: primary (PST), secondary (SST) and tertiary snig tracks (TST), log landings (LL), general logging areas (disturbed areas which were not occupied by snig tracks or log landings) and undisturbed areas (HA-S0). Within the general logging areas, measurements were made for three levels of soil profile disturbance: litter disturbed (HA-S1), topsoil disturbed (HA-S2) and subsoil disturbed (HA-S3). During 1989 samples were taken from 0 to 100 mm soil depth and during 1999 from 0 to 100, 100 to 200 and 200 to 300 mm soil depth. No significant differences in organic matter content, macroporosity and bulk density were found between 1989 and 1999 for most of the sampling sites. The rate of recovery of organic matter, macroporosity and bulk density varied depending with degree of soil disturbance and soil depth. The subsoil disturbance (HA-S3) had more influence on soil physical properties than any other type of disturbance. In general, the effect of soil profile disturbance and compaction on soil properties was greater at surface soil than deeper soil. Ten years after logging, macroporosity and organic matter content was significantly lower in the PST and HA-S3 compared to undisturbed areas. In the HA-S3 and PST, organic matter, macroporosity and bulk density was 31–41% lower, 44–60% lower, 22–68% greater, respectively, compared to undisturbed areas. The results are discussed in relation to tree growth and Montreal Process soil indicators.

Impact of major snig tracks on the productivity of wet eucalypt forest in Tasmania measured 17–23 years after harvesting

Summary During ground-based harvesting operations the passage of machinery leads to the formation of a mosaic of major and minor snig tracks from tree stumps to the landing. The impact of heavy traffic can lead to significant changes in the underlying soil physical properties and potentially in long-term growth of trees on these tracks. This study examined the impact of major snig tracks on the productivity of wet eucalypt forest in Tasmania. The three stands studied were dominated by Eucalyptus obliqua that regenerated from clearfelling, slash burning and aerial sowing 17–23 y earlier. Accumulated tree growth and soil physical and chemical properties were measured in three zones: snig tracks, transitional zone (edge of snig tracks), and control. There was a dramatic decline of 52– 80% in the accumulated tree volume in snig track zones when compared to the control zones. This was accompanied by a significant increase in the soil bulk density of 20–23%, and measured changes in a number of soil properties including 22– 33% decrease in organic carbon, 28–32% decrease in total N, and 3–11% decrease in total P on the snig track zones. There was no significant difference in either the soil physical or chemical properties of the transitional zones compared to the control zones, but there was a significant increase in tree growth in the transitional zones, ranging from 30% to 100%. An increase in stand density was the major factor contributing to improved growth in transitional zones, with increases in average diameter and average height having minimal effect. After 17–23 y the increase in stand productivity in the transitional zone compensated for much of the productivity lost due to poor growth on the snig tracks. The overall negative impact of snig tracks on stand productivity was calculated to be of the order of 2–3%.

Is soil carbon a useful indicator of sustainable forest soil management?—a case study from native eucalypt forests of south-eastern Australia

The area and percent of forest land with significantly diminished soil organic matter (SOM) and/or changes in other soil chemical properties has been proposed as a regional sustainability indicator for Australia’s forests. This study examined for native eucalypt forest in south-eastern Australia how representative soil organic carbon (SOC) is of important ecosystem properties and processes. In addition, it was investigated how sensitive the proposed indicator is to management-induced disturbance of these forests. Three sites in Victoria with a known disturbance history and a mapped distribution of soil disturbance (different intensities of fire, snig tracks, and soil perturbation) were included. These sites (2× Eucalyptus regnans, 1× Eucalyptus sieberi) had been clearfelled 9–10 years prior to sampling. The fine-soil fraction (<2 mm) was analysed for SOC, microbial C and N, mineralisable C and N, and available P. In addition, SOC was determined in rocks, plant residues, and charcoal in the fraction greater than 2 mm. Non-labile SOC in the fine-soil fraction contributed to 47–66% of the total in soil profiles (litter layer and 0–30 cm mineral soil). Charcoal in the >2 mm fraction contributed to 13–27% of total SOC. The relationships between SOC and measures of organic matter quality and N and P availability were inconsistent across sites and management practices. The effects of disturbance were most pronounced in the surface soil (0–7.5 cm). Including deeper soil layers in the statistical analysis diluted disturbance effects. Significant differences in the SOC content between soil disturbance intensities in the fine-soil fraction disappeared when size fractions>2 mm were considered. In addition, soil compaction masked changes in SOC concentration in some cases, when SOC was expressed on a volume basis. When all size fractions were considered, SOC stocks increased with fire intensity as a result of charcoal inputs. Physical soil disturbance appeared to be more critical for regrowth productivity than the effects of slash fires. Our results showed that the proposed indicator, changes in SOC, does not meet several of the attributes of what is commonly regarded as a good ecological indicator. Of particular concern are the changes in SOC resulting from charcoal inputs, which are difficult to interpret with regard to soil fertility. Without further qualifications, the changes in SOC cannot be recommended for implementation as an indicator of sustainable soil management in native eucalypt forests. Alternative approaches for the monitoring of changes in soil properties are discussed.

Modelling plumes of overland flow from logging tracks

AbstractMost land‐based forestry systems use extensive networks of unsealed tracks to access the timber resource. These tracks are normally drained by constructing cross‐banks, or water bars, across the tracks immediately following logging. Cross‐banks serve three functions in controlling sediment movement within forestry compartments: they define the specific catchment area of the snig track (also known as skid trails) so that the overland flow does not develop sufficient energy to cause gullies, and sheet and rill erosion is reduced; they induce some sediment deposition as flow velocity reduces at the cross‐bank; they redirect overland flow into the adjacent general harvesting area (GHA) so that further sediment deposition may take place. This paper describes a simple model that predicts the third of these functions in which the rate of runoff from the track is combined with spatial attributes of the track and stream network. Predictions of the extent of the overland flow plumes and the volume of water delivered to streams is probabilistically presented for a range of rainfall‐event scenarios with rainfall intensity, time since logging and compartment layout as model inputs. Generic equations guiding the trade‐off between intercross‐bank length and flow path distance from cross‐bank outlet to the stream network needed for infiltration of track runoff are derived. Copyright © 2002 John Wiley &amp; Sons, Ltd. Copyright © 2002 John Wiley &amp; Sons, Ltd.

A combined rainfall simulator and tracer approach to assess the role of Best Management Practices in minimising sediment redistribution and loss in forests after harvesting

In this paper, we use the combined results from two contrasting methods to investigate the effectiveness of Best Management Practices (BMPs) on sediment erosion and redistribution in managed forestry environments in southeastern New South Wales (NSW), Australia. The first method employed a rainfall simulator at the skid track (snig track)—water bar (cross-bank)—general harvest area (GHA) spatial scale. This showed the majority of production and redistribution occurring from the skid tracks and coinciding with the period after initial disturbance. However, 5 years after harvesting, little redistribution between these elements was occurring. Furthermore, water bar structures were effective in trapping coarse sediment generated from skid tracks but markedly less so for fine <63 μm material. The second method involved constructing a tracer budget. This was based on measuring the 137Cs content in each of the landscape elements of an entire watershed, which also enclosed a 5-year forest coupe selected for the simulator experiments. The 137Cs budget effectively balanced with 61.1±4 and 59.2±4 MBq present prior to, and after, harvesting, respectively. Total recovery was 97±10%, which indicated no net loss of sediment from the study basin over the 6-year post-harvesting period within uncertainties. Of the total sediment redistribution, some 13±4% in losses occurred from the skid tracks and log landings, whilst net gains of 10±1% occurred in the GHA, filter strip and water bars. On a per unit area basis, the filter strip retained ∼8 times the 137Cs and associated sediment of the GHA; however, the greatest overall trapping of fine sediment occurred in the GHA. Combining these two approaches suggests that management of filter areas is paramount, although the GHA remains the primary sediment buffer for the system. Greater effort to disconnect flow paths, retain roughness and reduce overland flow volumes in order to increase sediment deposition should occur here.

A tracer budget quantifying soil redistribution on hillslopes after forest harvesting

Managing the impacts of erosion after forest harvesting requires knowledge of erosion sources; rates of sediment transport and storage; as well as losses from the system. We construct a tracer-based (137Cs) sediment budget to quantify these parameters. The budget shows significant redistribution, storage and transport of sediment between landscape elements and identifies the snig tracks and log landings as the major impact sites in the catchment. Annual sediment losses from them were estimated to be 25±11 and 101±15 t ha−1 year−1, respectively, however, it is probable that most of this is due to mechanical displacement of soil at the time of harvesting. The budget showed greatest net transport of material occurring from snig tracks; representing some 11±4% of the 137Cs budget. Of the latter amount, 18%, 28% and 43% was accounted for within the cross banks, filter strip and General Harvest Area (GHA), respectively. The 137Cs budget also showed the GHA to be a significant sediment trap. The filter strip played a fundamental role in the trapping of material generated from the snig tracks, the mass delivery to them from this source was calculated to be 1.7±0.6 kg m2 year−1. Careful management of these remains critical. Overall we could account for 97±10% of 137Cs. This retention suggests that (within errors) the overall runoff management system of dispersing flow (and sediment) from the highly compacted snig tracks, by cross banks, into the less compacted (and larger area) GHA and filter strips has effectively retained surface soil and sediment mobilised as a result of harvesting at this site.

Soil recovery from track construction and harvesting changes in surface infiltration, erosion and delivery rates with time

The effects of timber harvesting activities are often characterised by significant changes in surface soil properties, runoff production and erosion rates. Here we quantify trends in surface soil recovery following timber harvesting activities, specifically snig track (skid trail) construction and logging, based on changes in soil surface compaction, infiltration, and erosion with time since initial disturbance. Sites range in age from 0.5 to 5 years. Surface erosion on the snig tracks and general harvesting areas (GHA), and sediment storage and delivery between the two areas, are measured using a large rainfall simulator. Surface soil compaction shows no significant recovery over this time period, illustrating the persistent effects of machinery compaction on surface soil structure. In contrast, surface infiltration rates on the snig tracks increase by a factor of two and snig track erosion rates decline by almost one-order of magnitude over the 5-year period. These findings have important implications for assessing the cumulative impact of timber harvesting activities.

Sediment transport, redistribution and storage on logged forest hillslopes in south-eastern Australia

Post-logging changes in catchment sediment yield have traditionally been attributed to increases in hillslope erosion and delivery rates as a result of forest harvesting activities. Linking hillslope erosion to catchment yield in forestry environments remains difficult, however, primarily because of the scarcity of data on the nature of hillslope sediment storage and delivery processes. A large rainfall simulator (350 m2) was used to apply rainstorms to a logged hillslope containing a snig track (skid trail) and a general logging or harvesting area (GHA) on 10 forest compartments in south-eastern Australia. The experiments confirmed that the compacted, disturbed surfaces, such as roads and tracks, are the dominant sources of sediment in forestry areas. Sediment transport rates were limited by available sediment supply on both the snig track and the GHA, introducing important implications for the modelling of these surfaces using sediment transport capacity theories. Sediment delivery from the snig track to the adjacent GHA, via a cross-bank (drainage diversion), was strongly influenced by the percentage fine fraction in the eroded sediment. Preferential deposition of coarse aggregates was measured at erosion control structures and on the adjacent GHA. Over 50% of fine-grained material were deposited on the hillslope over a relatively short, flow path length of <5 m, highlighting the effectiveness of runoff diversion as a practice in reducing sediment flux. The transfer of water and sediment from disturbed to less disturbed parts of the landscape, and the associated potential for sediment storage, needs to be considered as part of any catchment impact assessment. Copyright © 1999 John Wiley & Sons, Ltd.

Runoff generation and re-distribution in logged eucalyptus forests, south-eastern Australia

While pristine forests are traditionally regarded as environments with low runoff and low erosion potential, timber harvesting can dramatically affect surface runoff production, with some important consequences for in-stream water quality. A series of large-scale (300m2) rainfall simulator experiments on disturbed forest hillslopes, incorporating both snig track (skid trail) and general harvesting areas (GHA), examined runoff generation and redistribution during three sequential simulated storms on 13 sites. The simulated storms represented 30-min rainfall events with recurrence intervals of 2, 10, and 100y respectively. The 13 sites were selected to represent dominant soil types and ages since disturbance. The snig tracks and GHA are characterised by significantly different soil hydraulic and vegetation properties as reflected in the nature and magnitude of runoff production. Infiltration-excess runoff dominated the snig track areas, while on recently disturbed GHA, runoff was distinctly patchy because of the high degree of spatial variability in saturated hydraulic conductivity (Ks) and degrees of disturbance. Surface runoff from recently constructed snig tracks was an order of magnitude higher than the neighbouring GHA. Relative differences in runoff production between the two areas declined during extreme rainfall events. Infiltration tests also indicated that a change in the processes and rates of runoff persists for at least 5y after disturbance. The practice of redistributing concentrated snig track runoff at cross banks was most effective for small storms. However, during more extreme events, the volume of snig track runoff increased and flow velocities and transport distances increased as the hillslope became increasingly saturated. The varying ability of the GHA to generate runoff and absorb concentrated flow from the snig track is likely to be critical in predicting both the initial hydrologic response and the recovery of a small catchment from forest disturbance.

Rehabilitation of snig tracks and landings following logging of Eucalyptus regnans forest in the Victorian Central Highlands—a review

Summary Forest operations can potentially have significant detrimental effects on soil physical properties and tree regeneration, establishment and growth, particularly on snig tracks, landings and temporary roads. This may consequently affect catchment water quality. The Code of Practice requires that landings be rehabilitated following logging operations. This paper reviews the effectiveness of rehabilitation techniques and timing on soil recovery and tree growth with reference to the Victorian Central Highlands forest. Ripping with tines mounted on a back of a dozer is widely used in this forest to ameliorate compacted sites. The ripping efficiency can be improved significantly if winged boots are added with the tines. The excavator may also be used in rehabilitating landings and snig tracks. The soil-water content at the time of tillage is very important in terms of good seedbed preparation using any rehabilitation techniques. Various models developed for agricultural soils can be used to predict soil workability periods in the Central Highlands forest.

The use of shelterwood in Eucalyptus regnans forest: the effect of overwood removal at three years on regeneration stocking and health

Summary Shelterwood regeneration was tested as an alternative to clearfelling of Eucalyptus regnans dominated forests in southeast Victoria, using two retention levels, 30% and 50% by basal area. Removal of the retained trees was carried out 3 years after the regeneration felling. Stocking of regeneration following overwood removal was generally unsatisfactory, particularly in terms of its distribution. Large contiguous unstocked areas (0.35 to 0.7ha) were evident in all treatment units. The sources of seedling damage included tree felling, log preparation and extraction related activities such as snig track construction, log winching and snigging. Where there was soil profile disturbance, usually related to snig track construction, the vegetation was generally destroyed, accounting for much of the reduction in seedling density and stocking. In the remaining area substantial seedling damage was attributed to tree felling. Therefore, while a similar snig track network is necessary regardless of the level of overwood retention, the level of damage caused by felling trees, log preparation and winching can be expected to be directly proportional to the number of trees felled. Lower shelterwood retention levels should result in reduced damage to established regeneration. There was no conclusive evidence that dominant or co-dominant seedlings sustained more damage than intermediate or suppressed trees, although there were proportionally fewer dominant seedlings in 3 out of 4 replicates following the operation. The effect of shape, size and topography of the treatment units influenced the extent of the damage. A high perimeter to area ratio and relatively small felling plot size meant that options for directional felling of the trees to minimise regeneration damage were frequently constrained by the proximity of the boundary, and concentrated felling damage resulted in large unstocked areas. If damage to regeneration is to be reduced to an acceptable level during overwood removal operations at three years after the regeneration felling, careful consideration should be given to coupe layout and felling prescriptions, the slope of the coupe, particularly near coupe boundaries, and the machinery used for extraction.

Soil physical and hydrological properties following logging and slash burning in the Eucalyptus regnans forest of southeastern Australia

Logging causes soil profile disturbance (mixing and/or removal of soil) and compaction. Regeneration slash fire causes burning of surface soils. This may change soil physical and hydrological properties, which may affect site productivity and catchment water quality. This study was undertaken to quantify the effect of logging and slash burning on areal distribution of soil profile disturbance, fire intensity class and physical and hydrological properties of the 0–100 mm surface soil in the Victorian Central Highlands, southeastern Australia. Following clearfelling logging and slash burning, four coupes were surveyed using a systematic grid sampling technique. Each coupe was classified into the following operation categories: snig tracks, log landings and general logging areas. Each coupe was also classified in terms of both level of soil profile disturbance: undisturbed, litter disturbed, topsoil disturbed and subsoil disturbed; and intensity of fire: unburned, low intensity, moderate intensity and high intensity. The soil physical and hydrological properties were measured in two of the four logging coupes. Measurements were made in the snig tracks (primary, secondary and tertiary tracks), log landings and general logging areas. Within the general logging areas, plots were located for two classes of soil profile disturbance: undisturbed and topsoil disturbed. Within each of the two classes of soil profile disturbance measurements were made for three levels of fire intensities: unburned, moderate intensity and high intensity burn.Following logging and slash burning, on average 11% of the coupe area remained undisturbed, 11% litter disturbed, and 78% had mineral soil exposed. The snig tracks, log landings and disturbed general logging area occupied about 19%, 3% and 66% of the coupe area, respectively. On average, 52% of the coupe area remained unburned and 8% was affected by high intensity burn.Soil profile disturbance significantly changed particle size and organic matter distribution, increased bulk density, decreased aeration porosity and saturated hydraulic conductivity in the unburned general logging area. Soil compaction significantly increased bulk density, water-filled porosity (< 30 μm) and availabel water, and decreased aeration porosity and saturated hydraulic conductivity in the primary snig tracks and log landings.The high intensity slash burning significantly reduced clay and organic matter content in the undisturbed soil profile conditions but not for disturbed soil profile conditions. Implications for changes in these soil properties are discussed in terms of eucalypt establishment and growth and soil erosion potential.

Changes in physical properties of a soil associated with logging of Eucalyptus regnan forest in southeastern Australia

Logging operations can cause soil profile disturbance and compaction. Soil profile disturbance and compaction change soil physical properties, which may reduce site productivity, increase soil erosion and degrade catchment water quality. This study was undertaken to measure the effect of logging on physical properties of the 0–100 mm surface soil in the Victorian Central Highlands, southeastern Australia. Soil physical properties were measured in the snig tracks, log landings, general logging areas (disturbed areas which were not occupied by snig tracks or log landings) and undisturbed areas. Within the general logging areas, measurements were made for three levels of soil profile disturbance: litter disturbed, topsoil disturbed and subsoil disturbed. The results indicated that logging significantly increased bulk density and decreased organic carbon and organic matter content, total porosity and macroporosity on over 72% of the coupe area. However, on 35% of the coupe area, the snig tracks, log landings and subsoil disturbed areas of the general logging area, bulk densities and macroporosities reached critical levels where tree growth could be affected. On these areas, organic carbon decreased between 27 and 66%, bulk density increased between 39 and 65% and macroporosity decreased between 58 and 88%. Saturated hydraulic conductivities decreased to critical levels for runoff to occur on over 72% of the coupe area (topsoil and subsoil disturbed areas of the general logging area, snig tracks and log landings). On this area, the reduction in saturated hydraulic conductivity varied between 60 and 95%.

Water quality in mountain ash forests — separating the impacts of roads from those of logging operations

The purpose of the two catchment studies reported here was to allow the effects on water quality of road use and maintenance to be separated from the effects of a logging operation. In the first project, known as the Myrtle experiment, two small catchments in an old-growth mountain ash ( Eucalyptus regnans) forest were chosen for a paired catchment study of the effects on physical and chemical water quality (baseflow and stormflow) of logging under a strict code of practice and with no roads crossing runoff producing areas. In the second project, known as the Road 11 experiment, the effect on sediment production from unsealed forest roads of vehicle use and level of road maintenance was assessed. The Myrtle experiment showed that the harvesting and regeneration operation did not have a major impact on the stream physical or chemical water quality. Increases were detected in turbidity, iron and suspended solids at baseflows, but these were small in absolute terms and of similar magnitude to the measurement error. The stormflow data revealed no significant influence of the logging operation. The suspension of logging during wet weather, the protection of the runoff producing areas with buffer strips and the management of runoff from roads, snig tracks and log landing areas eliminated intrusion of contaminated runoff into the streams, thereby avoiding the adverse effects of logging. The Road 11 study determined that annual sediment production from forest roads was in the range of 50–90 t of sediment per hectare of road surface per year, with approximately two-thirds being suspended sediment and one-third coarse material. The use of gravel reduced sediment production, provided a sufficient depth of material was used. Increasing the level of road maintenance with increasing traffic load controlled sediment production rates, but when maintenance was not increased, sediment production increased by approximately 40%. The results indicate that by identifying the areas that produce runoff it is possible to prevent contaminated runoff reaching the streams. Roads, on the other hand, produce large quantities of sediment, even when well maintained, so careful consideration of their placement and management is paramount.

The effect of some soil chemical properties of the selective logging of a north Queensland rainforest

Some of the important chemical properties of a red granitic soil occuring under tropical rainforest in north Queensland, Australia, were measured immediately after the forest was selectively logged and one, two, and four years after loggin. The site was stratified into four disturbance classes encompassing the effects of snig tracks, crown litter accumulation and penetration of light through gaps in the canopy. Soil samples were taken in each disturbance class, as well as in undisturbed areas. The sampling design permited year to year changes in undisturbed areas to be monitored and used for comparison with disturbed areas. Snig track disturbance caused the greatest changes in soil chemical characteristics with losses of organic carbon and plant nutrients in the bulldozed portions and accumulation in the mounds formed at the sides. There were significant changes in properties from year to year but after four years, the contents of N, Ca, Mg, and K over the whole site had not altered significantly from initial values, whereas organic carbon declined by about 15%.

Changes in the composition of understorey vegetation after harvesting eucalypts for sawlogs and pulpwood in East Gippsland

AbstractCover and abundance of all understorey vascular plant species were studied on permanent plots on two areas (Maramingo and Reedy Creek) in the foothill forests of East Gippsland, eastern Victoria. The areas were harvested for sawlogs and pulpwood in 1976, and parts were burned to assist regeneration. Plots were assessed before harvesting and at intervals until 1980. Changes in total species composition were minimal, although there were many positive and negative changes in crown cover and abundance of individual species. Total cover of understorey vegetation was reduced initially but recovered well on both areas. By 1980, cover at Maramingo was slightly greater than the low levels before harvesting. Some species there were favoured by burning while others were not. At Reedy Creek the original dense understorey had not regenerated fully by 1980. Snig tracks had revegetated to 60% of original average cover but log landings were slower to revegetate. Introduced species were initially a very minor component of the vegetation on both areas: they remained so at Reedy Creek (confined mainly to tracks) but at Maramingo three species proliferated along with other small herbaceous plants.