Unharvested Control Research Articles

Fuelwood collection depresses the seed-dispersal service provided by rodents

Abstract Understanding the interaction between plants and their animal seed dispersers is essential for predicting the effects of disturbances on ecosystems. Timber harvests, including fuelwood collection, cause changes in both biotic and abiotic environments and could substantially reduce the total amount of forestland worldwide, thereby having multiple impacts on wildlife. Fluctuations and behavioral alterations of some species have been observed within fuelwood-collection forests, but the implications for forest recruitment processes are unknown. Here, using the acorn–rodent system, we quantified the impacts of fuelwood collection on the process of seed dispersal in two types of fuelwood-collection forests (i.e., active and abandoned) and an unharvested control forest in the non-mast and mast seeding year. Fewer seeds were dispersed at shorter distances in the active fuelwood-collection forest relative to the control forest, indicating depressed seed dispersal. Although seed dispersal effectiveness (SDE) in the active fuelwood-collection forest was similar to that in the control forest in a non-mast seeding year (0.029 vs. 0.031), we detected a 54.6% reduction in the active fuelwood-collection forest (0.017 vs 0.038) in the mast seeding year. The number and distance of seeds dispersed in a fuelwood-collection forest that had been abandoned for over 15 years, was intermediate between the low values observed in the active fuelwood-collection forest and the higher values found in the unharvested control. This suggests some recovery of seed dispersal after fuelwood-collection ceases; however, the SDE in this forest type was the lowest in both non-mast and mast seeding years (0.016 and 0.010). These patterns in the seed dispersal process (apart from SDE in fuelwood-collection forests) were stronger in the mast seeding year than in the non-mast seeding year. Variations in food availability, habitat structure, environmental pressure, and the size and composition of the disperser community following the removal of canopy trees for fuelwood induced these depressed seed dispersal processes. Given wildlife’s key roles in plant recruitment as seed dispersers, depressed animal-mediated seed dispersal as observed in this study may affect tree recruitment success and thus has wider implications for the spatial structure of plant communities in diverse forest ecosystems in which fuelwood is collected.

Tree removal as a management strategy for the lady’s slipper orchid, a flagship species for herb-rich forest conservation

In boreal herb-rich forests, the dominance of Norway spruce (Picea abies) decreases light availability for understory species, many of which depend on canopy gaps for reproduction. Here, we explored the response of a rare clonal understory herb, the lady’s slipper orchid (Cypripedium calceolus), to tree removal. We used demographic data spanning 16 years from ten unharvested control sites and ten harvest sites which were divided into three treatments with differing harvest intensity: (1) dense spruce forests, where half of the total tree basal area (TBA) was cut, (2) sparse spruce forests, where one-fourth of the spruce TBA was cut and (3) sparse broadleaf forests, where one-fourth of the total TBA was cut. The effects of harvesting on different demographic rates (ramet density, reproduction, survival, and dormancy) were studied with generalized linear mixed models with harvest intensity, time since harvest and the starting level of the response variable as explanatory variables. Tree removal sites had 2.2 times higher orchid ramet density, 2.4 times higher odds of survival, and 2.1–3.1 times higher odds of flowering and fruiting than the control sites, but these effects were not seen at all treatment levels at all times. Tree removal had no effect on dormancy or seedling or flower density. Orchid flowering and fruiting probabilities increased only at the most intensively harvested sites (both spruce forest sites, and dense spruce forest with 50% TBA removal, respectively), while survival and ramet density increased at the moderately harvested broadleaf forest sites. The effects on flowering and fruiting probabilities and survival disappeared quickly (after three years) when the canopy gaps closed, whereas ramet density responded only with a lag of over three years and was maintained to the end of the study. Our results thus demonstrate that for the lady’s slipper orchid, selective tree harvest might be a suitable management method that increases population size at the ramet level.

Effects of multiaged silvicultural systems on reserve tree growth 19 years after establishment across multiple species in the Acadian forest in Maine, USA

This study investigated the growth response of mature, isolated reserve trees (n = 528) in two multiaged silvicultural systems in the Acadian Forest Ecosystem Research Project (AFERP). Absolute and percent increases in basal area increment (BAI; cm2·year−1) were assessed for the five predominant reserve tree species in AFERP: Acer rubrum L., Picea rubens Sarg., Pinus strobus L., Thuja occidentalis L., and Tsuga canadensis (L.) Carrière. Absolute growth was significantly greater in the large-gap treatment (23.7 ± 1.1 cm2·year−1; mean ± SE) than in the small-gap treatment (16.3 ± 0.9 cm2·year−1). Percent growth increase was greater in the small-gap treatment (187.6% ± 15.8%) than in the large-gap treatment (143.4% ± 19.3%), and both treatments had greater percent increases than the unharvested control (9.6% ± 5.2%). Species differed in their response to treatment. Pinus strobus had the greatest absolute increase (large-gap, 52.5 cm2·year−1), while Tsuga canadensis (large-gap, 270% ± 71.6%) and Acer rubrum (small-gap, 262% ± 42.4%) had the greatest percent increases. Growth responses typically diminished with increasing tree size and pretreatment growth rate; however, reserve trees showed greater growth responses than their paired analogues in the control across all initial tree sizes and prior growth rates. The results suggest that these silivicultural systems accelerate the development of large trees.

Bryophyte abundance, diversity and composition after retention harvest in boreal mixedwood forest

Abstract Variable‐retention harvest is widely recognized as an alternative to more intensive methods such as clear‐cutting. However, present information is inadequate to judge the impact of variable retention on biodiversity of indigenous forest organisms intolerant of canopy removal, such as forest‐inhabiting bryophytes. We examined how bryophyte species cover, richness, diversity and composition change with time in response to a broad range of dispersed retention harvest treatments (2% [clear‐cut], 10%, 20%, 50%, 75% retention of original basal area) contrasted with uncut controls [100% retention]) in broadleaf deciduous, mixedwood and conifer‐dominated boreal forests in North West Alberta, Canada. Bryophytes were studied in 432 permanent sample plots within 72 compartments before harvest and at 3, 6 and 11 years after harvest. Clear‐cut and lower (10% and 20%) retention levels resulted in lower cover and richness of bryophytes than in unharvested control compartments in mixed and conifer‐dominated forests, but less so in deciduous‐dominated forests, which generally supported low cover and richness. Species composition in each forest type varied along the gradient of harvesting intensity; clear‐cuts and lower levels of retention supported similar composition, as did control plots and those representing higher retention levels. Over time, the retention harvest treatments became more similar to uncut controls. Synthesis and applications. Variable‐retention harvests can better maintain bryophyte biodiversity in managed boreal mixedwood forests, as compared to clear‐cuts. We found the efficacy of retention harvest scaled with harvest intensity. Higher levels of retention better moderated the negative impacts of harvesting on bryophyte assemblages across all forest types. Our results suggest, however, that even 10% retention will facilitate faster post‐harvest recovery of bryophytes, as compared to clear‐cutting.

Short-time effect of harvesting methods on soil respiration dynamics in a beech forest in southern Mediterranean Italy

CO2 fluxes from soil, together with soil water content and temperature have been measured over one solar year in an even-aged beech forest (Fagus Sylvatica L.) in southern Italy. We investigated the effects of three different harvested biomass removal treatments (traditional, innovative, unharvested control) on soil respiration (Rs) in three plots from May 2014 to April 2015, with the aim to evaluate the effects of such silvicultural practices on the CO2 respired from the forest floor. The influence of soil temperature and soil moisture on soil respiration was also analysed. Rs showed large variations among the treatments, with the innovative treatment resulting in significantly higher soil respiration than control and traditional treatments. There were no significant differences in soil temperature between the treatments, whereas soil water content was statistically different only in the innovative treatment. The study showed that the mean soil respiration increased with thinning intensity, confirming that after harvesting, residues remaining on the forest floor and decomposing roots may contribute to raise soil respiration, due to the higher microbial activity.

Harvesting influences functional identity and diversity over time in forests of the northeastern U.S.A.

Concern over global environmental change and associated uncertainty has given rise to greater emphasis on fostering resilience through forest management. We examined the impact of standard silvicultural systems (including clearcutting, shelterwood, and selection) compared with unharvested controls on tree functional identity and functional diversity in three forest types distributed across the northeastern United States.Sites included the Argonne, Bartlett, and Penobscot Experimental Forests located in Wisconsin, New Hampshire, and Maine, respectively. We quantified functional trait means for leaf mass per area, specific gravity, maximum height, height achieved at 20years, seed mass, drought tolerance, shade tolerance, and flood tolerance as well as standard functional diversity measures from standing biomass reconstructed at the beginning and end of a 20-year study period using increment cores and historic inventory data. As expected, functional identity differed between harvest methods with means for plant traits associated with later stages of succession (e.g. shade tolerance) increasing in stands managed with selection systems. Opposite trends occurred with greater canopy disturbance, and functional diversity indices remained stable over time in the absence of disturbance. Estimates of functional diversity and functional identity hold promise as important approaches for evaluating outcomes of forest management, particularly as the connections among functional diversity, delivery of ecosystem services, and ecosystem resilience are further developed.

Forest harvest intensity and soil depth alter inorganic nitrogen pool sizes and ammonia oxidizer community composition

Intensive forest harvest techniques have the potential to alter soil carbon and nutrient stocks and biogeochemical processes. We investigated how differing levels of organic matter removal (OMR) during timber harvest influenced the long-term stability of nitrification and the microbes regulating this process. Nitrification is limited by the activity of ammonia oxidizing bacteria (AOB) and archaea (AOA); however, reports on the relative contribution of each of these groups to forest soil nitrification have varied and have not been investigated in response to OMR. The influence of soil depth on the structure and function of the ammonia-oxidizing community has also been underreported and was included in this study. We quantified soil physicochemical properties including concentrations of ammonium (NH4+) and nitrite (NO2−) + nitrate (NO3−), and also coupled next generation sequencing and qPCR of the amoA gene to a whole-soil assay that stimulates nitrification and allows for the discrimination of AOA-from AOB-activity using 1-octyne, which inhibits bacterial ammonia monooxygenase activity. Soils were collected (1 m depth) from replicated loblolly pine (Pinus taeda L.) stands subjected to three different intensities of OMR (i.e., unharvested control, bole-only harvest, and whole-tree harvest + forest floor removal). Increasing intensity of OMR and increasing soil depth lead to significant reductions in concentrations of in situ NH4+ and NO2− + NO3−. Sequencing and subsequent annotation of the ammonia oxidizing community revealed that AOA were dominated by Crenarchaeota and AOB were dominated by Nitrosospira spp. The abundance of both bacterial and archaeal amoA were influenced by OMR and soil depth; furthermore, archaeal amoA was more abundant than bacterial amoA across all soil depths and the ratio of AOA to AOB increased with depth. Community structure of AOA and AOB were influenced by soil depth; however, only AOB were altered by OMR. Soil incubations revealed nitrification was N-limited in these forest soils. Furthermore, AOA- and AOB-contributions to total nitrification were nearly equivalent in surface soils; however, AOA contribution increased to 75% at 1 m. In general, the highest rates of nitrification occurred in the soils taken from unharvested control stands; however, OMR treatment differences were only significant when soils were amended with high levels of ammonia indicating that at ambient levels, intensive OMR may not lead to long-term alterations in nitrification potential.

Mechanical Harvesting Effectively Controls Young Typha spp. Invasion and Unmanned Aerial Vehicle Data Enhances Post-treatment Monitoring.

The ecological impacts of invasive plants increase dramatically with time since invasion. Targeting young populations for treatment is therefore an economically and ecologically effective management approach, especially when linked to post-treatment monitoring to evaluate the efficacy of management. However, collecting detailed field-based post-treatment data is prohibitively expensive, typically resulting in inadequate documentation of the ecological effects of invasive plant management. Alternative approaches, such as remote detection with unmanned aerial vehicles (UAV), provide an opportunity to advance the science and practice of restoration ecology. In this study, we sought to determine the plant community response to different mechanical removal treatments to a dominant invasive wetland macrophyte (Typha spp.) along an age-gradient within a Great Lakes coastal wetland. We assessed the post-treatment responses with both intensive field vegetation and UAV data. Prior to treatment, the oldest Typha stands had the lowest plant diversity, lowest native sedge (Carex spp.) cover, and the greatest Typha cover. Following treatment, plots that were mechanically harvested below the surface of the water differed from unharvested control and above-water harvested plots for several plant community measures, including lower Typha dominance, lower native plant cover, and greater floating and submerged aquatic species cover. Repeated-measures analysis revealed that above-water cutting increased plant diversity and aquatic species cover across all ages, and maintained native Carex spp. cover in the youngest portions of Typha stands. UAV data revealed significant post-treatment differences in normalized difference vegetation index (NDVI) scores, blue band reflectance, and vegetation height, and these remotely collected measures corresponded to field observations. Our findings suggest that both mechanically harvesting the above-water biomass of young Typha stands and harvesting older stands below-water will promote overall native community resilience, and increase the abundance of the floating and submerged aquatic plant guilds, which are the most vulnerable to invasions by large macrophytes. UAV's provided fast and spatially expansive data compared to field monitoring, and effectively measured plant community structural responses to different treatments. Study results suggest pairing UAV flights with targeted field data collection to maximize the quality of post-restoration vegetation monitoring.

Decadal‐scale changes in forest soil carbon and nitrogen storage are influenced by organic matter removal during timber harvest

AbstractThis study investigates whether different intensities of organic matter removal associated with timber harvest influence decadal‐scale storage of soil organic carbon (SOC) and total nitrogen (TN) in the top 1 m of mineral soil 18 years postharvest in a Pinus taeda L. forest in the Gulf Coastal Plain. We quantified forest harvest‐related changes in SOC, TN, microbial biomass carbon (MBC), and nitrogen (MBN) pools (0–100 cm) in unharvested control stands and in two organic matter removal treatment stands subjected to either (i) merchantable bole/stem‐only harvest or (ii) whole‐tree harvest + forest floor removal. In addition, δ13C of SOC and δ15N of TN were measured in mineral soil to provide insights regarding mechanisms that might explain changes in SOC and TN pool sizes. Soils were sampled seasonally for 1 year. Increasing organic matter removal intensity reduced SOC, TN, MBC, and MBN relative to the unharvested control. Furthermore, soils from whole‐tree harvest + forest floor removal stands had lower δ13C and higher δ15N values, suggesting that increasing organic matter removal may decrease heterotrophic activity as well as increase rates of N loss. Seasonal variabilities in SOC and TN were correlated to changes in forest biological properties such as root biomass and forest floor mass. These results indicate that more intensive harvest methods may lead to decade‐scale decreases in SOC and TN storage in surface and subsurface soils which could influence rates of biogeochemical processes, the availability of soil nutrients, and potential forest productivity.

Effect of harvest gap formation and thinning on soil nitrogen cycling at the boreal–temperate interface

In mixedwood forest, different types of commercial thinning that generate different gap sizes are being tested as alternatives to clearcutting to create forest stands with an irregular structure that would emulate the pre-industrial forests. The main goal of this study was to investigate the soil nitrogen (N) dynamics in response to two partial harvesting treatments, used alone or in combination: commercial thinning creating tree-size canopy gaps and harvest gaps creating 0.05 ha gaps. In a 30 year old balsam fir (Abies balsamea (L.) Mill.) stand, both treatments, alone or in combination, as well as unharvested controls were compared on replicated 0.75 ha plots. The most noticeable changes following treatments were observed in gaps, while commercial thinning did not significantly influence any of the parameters assessed. In gaps, increases in N mineralization rates and mineral N concentrations and proportions (NO3−-N and NH4+-N) relative to dissolved organic N were observed. Our results suggest that these changes are caused by the increase in soil temperature and water content. In these forests, the response threshold of the N cycling regarding the size of the intervention would therefore be located between the removal of one or a few trees (one to three stems, 6–12 m2) and a gap of 500 m2. Other studies conducted in different climate and forest types have shown that this threshold could be of equivalent or of a smaller size. These findings will contribute to optimizing our management strategies regarding partial cuts or small-scale clearcuts.

Canopy treatment influences growth of replacement tree species inFraxinus nigraforests threatened by the emerald ash borer in Minnesota, USA

Fraxinus nigra Marsh. (black ash), a dominant tree species of wetland forests in northern Minnesota, USA, is imperiled by the invasive insect emerald ash borer (EAB; Agrilus planipennis Fairmaire, 1888). Regeneration of associated tree species is generally low in F. nigra forests and could be impacted further by climate change. Proactive management may be critical to maintaining tree cover and ecosystem function following EAB invasion. We investigated the mean height and diameter relative growth rate (RGR) of seedlings of 10 potential replacement tree species, including two from the next southern climate zone projected to be adapted to the future northern Minnesota climate. Seedlings were planted in F. nigra wetlands under four canopy treatments: unharvested control, clearcut, girdling F. nigra to emulate EAB-induced mortality, and group selection. Mean height and diameter RGR was fastest overall in the clearcut treatment, followed by the girdling, group selection, and control treatments. Depending on species, treatment significantly influenced RGR. Several species projected to be adapted to the future northern Minnesota climate had moderate to rapid mean RGR, including one from the next southern climate zone. Our results suggest that seedling plantings and overstory treatment represent an effective strategy for establishing F. nigra replacement tree species as EAB approaches, while reducing future risk from climate change.

Assessing the long-term ecological effects of riparian management practices on headwater streams in a coastal temperate rainforest

Our understanding of how effective forestry Best Management Practices (BMPs) can mitigate logging impacts on the structure and functioning of temperate headwater streams tends to be based upon studies conducted within the first few years post-harvest. Little is known about how the affected biological parameters of streams change during riparian and upland forest regeneration, particularly the time taken to return to pre-harvest levels, or to within the range of reference conditions. By following up on an earlier study in southwestern British Columbia, Canada, we examined the post-logging recovery trajectories of stream attributes under multiple forest treatments. These treatments provided a gradient of riparian protection, including streamside clear-cutting with no reserves, and with fixed-width reserves (10m and 30m), and thinning with 50% basal area removal of riparian trees, which were compared with unharvested control sites. About 15years after clear-cutting and 9years after thinning, slower decomposition of red alder leaves (Alnus rubra) was reported in streams affected by forest harvesting, which was attributed to lower density of shredder invertebrates. Thinned reaches had lower litter decomposition rate than, but similar shredder density and richness to, unharvested reference sites. After a further 7years of forest regrowth (time elapsed between the previous and present study), we found that litter decomposition rate and shredder density in logging-affected reaches converged with values in reference reaches. Stream functional integrity, as reflected by litter decomposition, increased across all forest treatments. Some differences in rarefied shredder richness among forest treatments emerged in this study. The legacy effects of thinning on some biotic variables likely diminished more quickly (2–9years post-harvest) than those of clear-cutting with and without riparian reserves (8–15years). Stream recovery from thinning to reference conditions should continue to warrant attention, as wider, larger-scale partial harvesting practices are recommended within emerging paradigms of forest management. Overall, our findings indicate time scales towards recovery of an important ecological process of streams under common forestry practices, which could be longer than other stream properties, such as water quality. Such differences in recovery time frames should be considered for the planning of forestry operations and monitoring of harvesting legacies.

Ten-year responses of ground-dwelling spiders to retention harvest in the boreal forest.

The Ecosystem Management Emulating Natural Disturbances (EMEND) project tests the hypothesis that varying levels of green tree retention maintain and retain forest biodiversity better than conventional clear-cutting. We studied epigaeic spiders to assess biodiversity changes 2, 5, and 10yr following a range of partial retention harvests (clear-cut, 10-75% retention) and unharvested controls in four boreal mixedwood cover types. A total of 56 371 adult spiders representing 220 species was collected using pitfall traps. Lasting effects on forest structure were proportional to harvest intensity. These changes strongly influenced spider richness, abundance, and species composition, as well as assemblage recovery. Distinctive assemblages were associated with disturbance level, especially with partial harvests (≤50% retention), and these were dominated by open-habitat species even 10yr after harvest. Assemblages were more similar to those of controls in the highest (75%) retention treatment, but significant recovery toward the structure of pre-disturbance assemblages was not detected for any prescription in any cover type. Although early responses to retention harvest suggested positive effects on spider assemblages, these are better explained as lag effects after harvest because assemblages were less similar to those of unharvested controls 5yr post-harvest, and only minor recovery was observed 10yr following harvest. Retention of forest biodiversity decreased over time, especially in conifer stands and the lower (10-50%) retention treatments. Overall, retention harvests retained biodiversity and promoted landscape heterogeneity somewhat better than clear-cutting; however, there was a clear gradient of response and no retention "threshold" for conservation can be recommended on the basis of our data. Furthermore, results suggest that retention harvest prescriptions should be adjusted for cover type. We show that low retention ameliorated impacts in broadleaved forests characteristic of earlier stages in mixedwood succession, but only higher retention was associated with less impact in successionally older conifer forests. Although these short-term responses (10yr) of spider assemblages support use of retention harvests, understanding the true conservation merit of these practices, relative to conventional approaches, requires evaluation over longer time scales, with work more focused on recovery of biodiversity than on its preservation after harvest.

Prescribed burning is an effective and quick method to conserve rare pyrophilous forest‐dwelling flat bugs

Abstract Fire suppression and reduced volumes of dead wood have led to a major decline in pyrophilous and saproxylic insects in Fennoscandian boreal forests. As a consequence, several species are currently seriously threatened. Flat bugs (Heteroptera, Aradidae) is an important invertebrate group that includes several pyrophilous species, including many threatened ones. We explored whether specific conservation measures – prescribed burning and retention forestry – can facilitate the survival of flat bugs in managed forests. The large‐scale field experiment consisted of a burning treatment (yes/no) and four levels of logging intensity (clear‐cut, retention levels of 10 and 50 m3 ha−1, and unharvested controls). The data included 1224 individuals of 12 species, sampled over a 4‐year period. Burning increased the species richness and abundance of the pyrophilous species. Two Red‐Listed and very rare pyrophilous species, Aradus angularis J. Sahlberg (Vulnerable) and A. laeviusculus Reuter (Near Threatened), were abundant after burning. The number of non‐pyrophilous flat bugs collapsed after burning but they re‐colonised the stands quickly, becoming as abundant as at the unburned stands. Logging increased the abundance of flat bugs only when retention forestry was applied. This study shows that pyrophilous flat bugs are quickly able to locate recently burned forests and that these forests are important for their survival. The effect of fire is, however, transient at the stand level and pyrophilous species disappear almost completely quickly after fire. To maintain these species, recently burned forests with a sufficient volume of retention trees should be available continuously at the landscape level.

Assessment of Streamside Management Zones for Conserving Benthic Macroinvertebrate Communities Following Timber Harvest in Eastern Kentucky Headwater Catchments

Headwater streams generally comprise the majority of stream area in a watershed and can have a strong influence on downstream food webs. Our objective was to determine the effect of altering streamside management zone (SMZ) configurations on headwater aquatic insect communities. Timber harvests were implemented within six watersheds in eastern Kentucky. The SMZ configurations varied in width, canopy retention and best management practice (BMP) utilization at the watershed scale. Benthic macroinvertebrate samples collected one year before and four years after harvest indicated few differences among treatments, although post-treatment abundance was elevated in some of the treatment streams relative to the unharvested controls. Jaccard index values were similar across SMZ treatments after logging, indicating strong community overlap. These findings suggest that stream invertebrate communities did respond to the timber harvest, though not negatively. Results also suggest that SMZ criteria for aquatic habitats in steeply sloping topography, including at least 50 percent canopy retention and widths of at least 16.8 m, appear to be adequate for protecting benthic macroinvertebrate communities from logging impacts.

Influence of Variable Streamside Management Zone Configurations on Water Quality after Forest Harvest

Streamside management zones (SMZs) are a common best management practice (BMP) used to reduce water quality impacts from logging. The objective of this research was to evaluate the impact of varying SMZ configurations on water quality. Treatments (T1, T2, and T3) that varied in SMZ width, canopy retention within the SMZ, and BMP utilization were applied at the watershed scale to two watersheds each. Watersheds with wider SMZs (T3: 110 ft, 100% canopy retention) and improved crossings were not significantly different from unharvested control (C) watersheds for all parameters except nitrate and diurnal stream temperatures. Changes in total suspended solids, turbidity, nitrate, dissolved oxygen, and maximum stream temperature were detected for watersheds treated with the current recommended minimum SMZ configurations (T1: 55 ft, 50% canopy retention) and watersheds with unharvested SMZs (T2: 55 ft, 100% canopy retention) and improved crossings.

The responses of a critically endangered mycophagous marsupial (Bettongia penicillata) to timber harvesting in a native eucalypt forest

Mycophagous bioturbators provide ecosystem services that can be important for the resilience and restoration of ecosystems. Among the Australian mammals, mycophagy is most prevalent within the Potoroidae (bettongs and potoroos). However, proportionally more species of Potoroidae are either recently extinct or currently threatened than any other mammalian family in Australia, and they are among the least studied. The critically endangered woylie, or brush-tailed bettong (Bettongia penicillata), is a mycophagous, ground dwelling ‘ecosystem engineer’ that was one of Australia’s most abundant and widely distributed potoroids prior to European settlement. After substantial range contraction, however, the remaining indigenous populations are now restricted to eucalypt forests in south-western Australia. Using an experimental approach, we investigated the population responses of the woylie to timber harvesting in these forests. Nine treatments, including varying logging intensities and unharvested controls, were applied at 22 sites. The abundance of the woylie in the harvested areas, in unharvested stands between logged areas, and in extensive unharvested stands outside the harvest management area were compared using a replicated before-after-control-impact (BACI) repeated measures design and capture-mark-recapture modelling. A total of 5860 captures of 815 individuals were recorded during 35 trapping sessions over 16years (one year preceding, two years during, and 13years after disturbance). Capture rate was a good index of abundance for this species and woylie abundance, survivorship and recruitment were not adversely affected by silvicultural practices in the jarrah (Eucalyptus marginata) forest. On the contrary, the harvested areas may have afforded some localised protection when an unrelated, species-wide decline began three years after harvesting disturbance ended; woylie numbers declined by up to 77% and 95% in harvested and unharvested areas, respectively. Thus the nature and spatial extent of the timber harvesting regimes investigated in this study were not a major threatening process for this species. However, ongoing monitoring and evaluation are necessary to ensure that timber harvesting activities remain benign in the face of a changing climate, possible increased mortality from introduced predators, disease, and further declines in the abundance of this critically endangered marsupial.

Decadal effects of emulating natural disturbances in forest management on saproxylic beetle assemblages

Prescribed burning and retention forestry are used to bring the biological legacies of forest harvesting closer to those of natural disturbances. Although widely used, the effects of these methods on species assemblages in the longer term are still relatively unknown. In 2000, we established a large-scale replicated field experiment to explore the effects of prescribed burning and tree retention (four levels: 0, ten and 50m3ha−1 and unharvested control) on saproxylic beetles. Assemblages were monitored over 10 post-treatment years. Our results showed that species richness of predators was increased by burning of the forest stand. Early- and late-stage xylophagous species increased in the first post-harvest year. Increased logging intensity led to a decrease in mycetophagous, early-stage xylophagous and predator species richness over the ten year period. In the burned unharvested stands, the total species richness remained high after ten years, but decreased to the pre-treatment level in the stands with retention trees, and to even lower levels in the clear-cuts. Furthermore, the saproxylic beetle assemblages in the burned unharvested stands differed from the assemblages in any of the harvested stands. Burning increased pyrophilous and rare and red-listed (RRL) species richness. Over the ten year period, the richness of those species collapsed in the harvested stands, but increased in the burned unharvested stands. Our results emphasize the difference in tree stand legacies between logging and natural disturbance, but also indicates that prescribed burning and retention forestry have the potential to alleviate the negative effects of forest management on biodiversity in the longer term.

Response of the soil microbial community and soil nutrient bioavailability to biomass harvesting and reserve tree retention in northern Minnesota aspen-dominated forests

Intensive forest biomass harvesting, or the removal of harvesting slash (woody debris from tree branches and tops) for use as biofuel, has the potential to negatively affect the soil microbial community (SMC) due to loss of carbon and nutrient inputs from the slash, alteration of the soil microclimate, and increased nutrient leaching. These effects could result in lowered forest productivity and threaten the long-term sustainability of forest management. Retaining organic material post-harvest, including greater amounts of harvesting slash and live trees, within harvested areas may ameliorate some negative effects of biomass harvesting on soil processes. We evaluated the effects of biomass harvests with reserve tree and slash retention on the SMC and soil nutrient bioavailability (assessed using plant-root simulator probes) in trembling aspen (Populus tremuloides Michx.) forests in northern Minnesota during the spring and summer, 1–3 years after harvest. Variable biomass removal levels tested include complete removal (whole tree harvest of boles and branches), complete slash retention (bole only harvest), and 20% slash retention (amount suggested by regional biomass harvesting guidelines). Compared to the unharvested control, biomass harvests had no effect on the multivariate SMC composition or microbial biomass, but did result in a 1–4% increase in arbuscular mycorrhizal fungal abundance and reduced bacterial stress two and three years after harvest. Additionally, biomass harvesting increased NH4 bioavailability during year one, and reduced NO3 bioavailability during year two when compared to unharvested controls. Among the three biomass harvests with differing levels of slash removal there were few differences in overall SMC composition, microbial biomass, and soil nutrients; however, the abundance of arbuscular mycorrhizal fungi, gram positive and actinomycete bacteria were significantly higher in harvested treatments with more slash retained. These results are specific to single rotation biomass harvesting in aspen stands due to the unique relationships between plants and their associated SMCs, and may not be directly applicable to forest biomass harvesting of other commercial forest tree species, or multiple rotations.

Nine-year changes in carbon dynamics following different intensities of harvesting in boreal aspen stands

Mixedwood forests occupy a large extent of boreal regions and have the potential for sequestering large amounts of carbon. In the context of forest ecosystem management, partial cutting prescriptions are increasingly being applied to boreal mixedwood stands. Partial harvesting is expected to maintain carbon pools and dynamics within the limits of those of natural stands. Changes in live tree, deadwood (standing snags, downed logs), forest floor and mineral soil carbon pools were assessed over a 9-year period in a replicated large-scale experiment, which included unharvested controls, two variants of partial harvesting and clear-cuts. We also measured leaf litter and deadwood inputs and decay rates. Carbon flux through leaf litterfall recovered rapidly following partial harvesting. Carbon flux from live trees to deadwood pools was a dominant process in partially harvested stands where snags and downed log carbon pools remained similar to those of natural stands. Hence, the nature of litter inputs diverged strongly among clear-cut and partially harvested treatments. Leaf and wood decay rates were higher in the partial cuts and controls than in clear-cuts. No significant differences in forest floor and mineral soil carbon were observed 9 years after harvesting. Carbon sequestration in live tree biomass was the carbon pool that most strongly differentiated the treatments allowing partial harvesting to maintain forest stands as net carbon sinks.