Managed Forest Sites Research Articles

Earthworm influence on soil aggregate distribution and protected carbon at managed forest sites in Vermont, USA

The long-term effect of non-native earthworm species on forest soil carbon storage is not clear. While initial invasion into earthworm-free soils stimulates carbon losses, there is evidence that carbon stabilization in soil aggregates is enhanced. Fourteen managed forest sites throughout Vermont were sampled to identify and enumerate earthworms, and determine soil aggregate distribution and physically protected carbon. Most of these sites were northern hardwoods reforested in the mid-20th century after agricultural land use. Soil at six 50 × 50 cm subplots at each site was sampled to a depth of 20 cm below the Oe horizon and the mineral soil fractionated into free microaggregates (<250 μm), small macroaggregates (250–2000 μm), and large macroaggregates (>2000 μm). Microaggregates were then isolated from the macroaggregates and organic carbon determined. Mean earthworm numbers below the Oe horizon at each site ranged from 0 to 313 individuals m−2 and ten different species were identified, representing all earthworm ecotypes. Four sites had no earthworms in the soil layer sampled, three sites had earthworms in every subplot with up to six different species, and seven sites had subplots both with and without earthworms. When subplots were grouped by number of species present, there was a trend towards a greater fraction of the mineral soil in macroaggregates containing greater protected carbon, and a lower fraction of free microaggregates. A paired t-test of subplots from the seven sites with variable earthworm presence showed significant differences in the same trends and there was significantly greater mineral soil total carbon and protected carbon in the subplots with earthworms. These results are consistent with recent research into earthworm effects on soil carbon stabilization. While initial invasion likely resulted in a negative carbon balance, our findings suggest that earthworms can enhance transfer of carbon into physically protected pools in these forest soils.

Effect of exotic species management on the recovery of relict forests through citizen participation

In the cities, remnants of the vegetation that originally occupied these areas can be found. Exotic species have established in these relicts, and therefore these spaces require management aimed at recovering native vegetation. In this study, we evaluated the impact of the removing exotic species on the floristic composition of the remnants of an oak forest. We compared the abundance/cover and composition of exotic plants in a forest that has been managed through citizen participation with that of reference forests (both with remnants, but the former without protection and the latter with protection). We established 48 sampling sites to characterize the vegetation in three strata (upper, middle, and low) and monitored changes in composition in managed forest sites for a period of 3 years. The results indicate that the managed forest hosts different species than those found in the reference forests, with lower abundance and cover of exotic plants in the upper and lower strata. Regarding temporal changes, we observed shifts in floristic composition before and after management activities, and a reduction in the cover of exotic species before and after management, with consistently low cover three years later. This underscores the effectiveness of citizen-led management activities, offering a viable alternative for restoring native vegetation in urban environments.

Effects of past and present microclimates on northern and southern plant species in a managed forest landscape

AbstractQuestionsNear‐ground temperatures can vary substantially over relatively short distances, enabling species with different temperature preferences and geographical distributions to co‐exist within a small area. In a forest landscape, the near‐ground temperatures may change due to management activities that alter forest density. As a result of such management activities, current species distributions and performances might not only be affected by current microclimates, but also by past conditions due to time‐lagged responses.LocationSweden.MethodsWe examined the effects of past and current microclimates on the distributions and performances of two northern, cold‐favoured, and two southern, warm‐favoured, plant species in 53 managed forest sites. Each pair was represented by one vascular plant and one bryophyte species. We used temperature logger data and predictions from microclimate models based on changes in basal area to relate patterns of occurrence, abundance, and reproduction to current and past microclimate.ResultsThe two northern species were generally favoured by microclimates that were currently cold, characterised by later snowmelt and low accumulated heat over the growing season. In contrast, the two southern species were generally favoured by currently warm microclimates, characterised by high accumulated heat over the growing season. Species generally had higher abundance in sites with a preferred microclimate both in the past and present, and lower abundance than expected from current conditions, if the past microclimate had changed from warm to cold or vice versa, indicating time‐lags in abundance patterns of the species.ConclusionsOur results show a potential importance of past and present microclimate heterogeneity for the co‐existence of species with different temperature preferences in the same landscape and highlight the possibility to manage microclimates to mitigate climate change impacts on forest biodiversity.

Prey size is more representative than prey taxa when measuring dietary overlap in sympatric forest bats

AbstractIn temperate forests, insectivorous bats need to use variable hunting strategies as prey availability fluctuates during the growing season. At sites with variable amounts of forested habitat, sympatric bat species may exhibit high dietary overlap, but mechanisms of coexistence are unknown. We analyzed the diets of sympatric Myotis septentrionalis and Myotis sodalis in two different landscapes in central Indiana, USA: a riparian agricultural site and a managed forest site, aiming to assess interspecific dietary overlap. We collected fecal samples from 166 Myotis over four maternity seasons and used DNA metabarcoding to assess niche overlap by operational taxonomic units (OTUs, n = 708) and prey‐size taxa (n = 79). Analyzing diets by prey‐size classes, as opposed to only species, provided an alternative interpretation of dietary richness and overlap that may more accurately represent predator perceptions of prey. With overall prey sizes ranging from 2–36 mm, M. septentrionalis (n = 88) consumed larger prey (10.0 ± 5.5 mm, μ ± σ) than M. sodalis (n = 78; 8.9 ± 5.0 mm). Myotis sodalis had a more diverse diet (547 OTUs) compared to M. septentrionalis (453 OTUs) despite the smaller sample size. Of the 708 OTUs detected, 41% (292) were common across bat species. We found greater dietary overlap between species within each site than within either species across sites, suggesting both species mostly consume whatever insects are available on the landscape. Flexible hunting strategies may allow these species to coexist by consuming different sizes of prey at different rates in the tradeoff between travel cost and profitability. Prey size is an important measure for dietary overlap and resource partitioning in bats that few studies have yet considered, with implications for linking predators, prey, and habitats.

A regional assessment of permanganate oxidizable carbon for potential use as a soil health indicator in managed pine plantations

Soil health assessments require the establishment of soil indicators that are easy to measure and sensitive to changes in management practices. Despite the global demand for wood products and the intensification of silvicultural practices, very few indicators are currently used to monitor changes in soil properties and processes in managed forest plantations. Labile pools of soil organic carbon (SOC) have been widely used in agriculture to detect early alterations in carbon (C) cycling processes but are largely untested in managed forests. Here, we investigate the potential use of permanganate oxidizable carbon (POXC) to monitor impacts of silvicultural practices on soil properties in loblolly pine plantations. Soil samples were collected from 77 managed forest sites and 297 experimental plots throughout the southeastern U.S. at four soil depths: 0–10, 10–20, 20–50, and 50–100 cm. Sites encompassed plantations with ages ranging from 2 to 29 yr that were distributed over five soil orders. Silvicultural practices included herbicide, fertilization at multiple rates, and thinning. Our study showed that POXC concentration decreases with soil depth, while POXC increased proportionally to SOC with depth. POXC positively correlates with SOC, total nitrogen, and mass of soil woody detritus other than live roots, and negatively correlates with soil pH across all soil depths. Impacts of silvicultural practices on POXC concentration were variable across sites. The mean relative response of POXC to silvicultural practices was negative in general but only significant (p < 0.10) in herbicide treatments; compared to control plots herbicide plots at 50–100 cm depth had on average 20% less POXC. The decade-long rotation lengths of southern pine plantations and the carbon cycling dynamics of forest soil O horizons may impact the sensitivity of POXC as an indicator in managed plantations. In contrast to this regional analysis, monitoring POXC in local assessments may be a more practical approach to investigate short-term impacts of silvicultural practices.

Interaction of land use history, earthworms, soil chemistry and tree species on soil carbon distribution in managed forests in Vermont, USA

Forest soils store a globally important pool of carbon (C) and reforestation has the potential to increase this pool. Past land use, tree species composition, and current management are known to affect carbon storage rates and amounts. Another important factor, especially in the vertical distribution of soil C, is the presence or absence of earthworms. We investigated these interactions in eighteen managed forest sites in Vermont that have varied land use history (cultivation, pasture, woodlot, continuous woodland) and a range of time since reforestation from 60 to 100+ years. Soils were sampled to about 1 m, or shallower if bedrock was reached, and both C and exchangeable cation pools quantified. Earthworms were enumerated to a depth of 20 cm and identified by species. Basal area by tree species was also measured and aboveground C calculated. Detailed land use history was documented using archival sources. Forest type was primarily northern hardwood, with a few lowland spruce-fir sites included. Eleven different species of earthworms were found, representing all ecotypes, and numbers ranged from 0 (at 8 of the 18 sites) to 319 individuals/m2. Carbon pools in the forest floor (1.5–30.1 Mg/ha) were greater with higher site elevation (range of 154–651 masl) and also greater with lower numbers of earthworms. Besides elevation, the best predictor of earthworm presence or absence, and overall numbers, was the soil exchangeable calcium (Ca) pool in the Oa and A horizons (range of 9.4–1288 cmolc/m2). Because soil exchangeable Ca and aluminum (Al) pools were inversely related, higher exchangeable Al was associated with lower earthworm numbers. In the mineral soil, the C pool (82.1–210.8 Mg/ha) was best explained by the thickness of the B horizons with the exchangeable Al pool as a positive, secondary factor. The thickness of the A horizon (0–16.3 cm), and its contribution to the entire profile C pool (0–54.7 Mg/ha), decreased relative to past land use in the order: cultivated < pasture < woodlot. No earthworm metric was strongly related to the C pool in either the mineral soil or the full soil profile. Dramatic differences in the vertical distribution of carbon were related to past land use and earthworm presence, which in turn was negatively correlated with elevation and the presence of conifers. While it is clear that earthworms and prior land-use have a long-lasting effect on the forest floor C pool, it is less clear whether or not there is an effect on full profile C sequestration over time.

Climate Associations with Headwater Streamflow in Managed Forests over 16 Years and Projections of Future Dry Headwater Stream Channels

Integrating climate-smart principles into riparian and upland forest management can facilitate effective and efficient land use and conservation planning. Emerging values of forested headwater streams can help forge these links, yet climate effects on headwaters are little studied. We assessed associations of headwater discontinuous streams with climate metrics, watershed size, and forest-harvest treatments. We hypothesized that summer streamflow would decrease in warm, dry years, with possible harvest interactions. We field-collected streamflow patterns from 65 discontinuous stream reaches at 13 managed forest sites in Western Oregon, USA over a 16-year period. We analyzed spatial and temporal variability in field-collected stream habitat metrics using non-metric multidimensional scaling ordination. Relationships between streamflow, climate metrics, basin size, and harvest treatments were analyzed with simple linear models and mixed models with repeated measures. Using past effects of climate variation on streamflow, we projected effects to 2085 under three future scenarios, then quantified implications on headwater networks for a case-study landscape. Ordination identified the percent dry length of stream reaches as a top predictor of spatial and temporal variation in discontinuous stream-habitat types. In our final multivariate model, the percent dry length was associated with heat: moisture index, mean minimum summer temperature, and basin area. Across future climate scenarios in years 2055–2085, a 4.5%–11.5% loss in headwater surface streamflow was projected; this resulted in 597–2058 km of additional dry channel lengths of headwater streams in our case study area, the range of the endemic headwater-associated Cascade torrent salamander (Rhyacotriton cascadae Good and Wake) in the Oregon Cascade Range, a species proposed for listing under the US Threatened and Endangered Act. Implications of our study for proactive climate-smart forest-management designs in headwaters include restoration to retain surface flows and managing over-ridge wildlife dispersal habitat from areas with perennial surface water flow, as stream reaches with discontinuous streamflow were projected to have reduced flows in the future with climate change projections.

Soil greenhouse gas, carbon content, and tree growth response to biochar amendment in western United States forests

AbstractRestoring overstocked forests by thinning and pyrolyzing residual biomass produces biochar and other value‐added products. Forest soils amended with biochar have potential to sequester carbon (C), improve soil quality, and alter greenhouse gas (GHG) emissions without depleting nutrient stocks. Yet, few studies have examined the effects of biochar on GHG emissions and tree growth in temperate forest soils. We measured GHG emissions, soil C content, and tree growth at managed forest sites in Idaho, Montana, and Oregon. We applied biochar amendments of 0, 2.5, or 25 Mg/ha to the forest soil surface. Flux of carbon dioxide and methane varied by season; however, neither were affected by biochar amendment. Flux of nitrous oxide was not detected at these nitrogen‐limited and unfertilized forest sites. Biochar amendment increased soil C content by 41% but did not affect tree growth. Overall, biochar had no detrimental effects on forest trees or soils. We conclude that biochar can be used harmlessly for climate change mitigation in forests by sequestering C in the soil.

The Effect of Logging and Strip Cutting on Forest Floor Light Condition and Following Change

We monitored changes in light conditions at a primary forest and two managed forest sites (one with line planting) after reduced-impact logging in Central Kalimantan, Indonesia. We also assessed the effect of the light conditions on seedlings in the planting lines. Hemispherical photographs were taken over a period of 31 months in three 50 × 50-m quadrats at each site and in three 100-m transects along the planting lines. The location of each photo was categorized according to the corresponding type of disturbance, including skid trails, logging gaps, and planting lines. Following logging, the level of canopy openness (CO) increased at both managed forest sites and did not differ significantly between the two. However, CO was greater in skid trails and logging gaps than in planting lines. After 31 months, the mean level of CO at each managed site had decreased significantly due to the establishment of new seedlings. Correlations between changes in CO and the growth of planted seedlings suggested that growth was inhibited by the invasion of the new species. However, the level of CO along the planting lines was greater than that at other disturbed locations. A high level of CO promoted invasion by new species that colonized the space. Line planting may influence forest dynamics and maintain a high level of CO.

Understanding the effect of disturbance from selective felling on the carbon dynamics of a managed woodland by combining observations with model predictions

AbstractThe response of forests and terrestrial ecosystems to disturbance is an important process in the global carbon cycle in the context of a changing climate. This study focuses on the effect of selective felling (thinning) at a managed forest site. Previous statistical analyses of eddy covariance data at the study site had found that disturbance from thinning resulted in no significant change to net ecosystem carbon uptake. In order to better understand the effect of thinning on carbon fluxes, we use the mathematical technique of four‐dimensional variational data assimilation. Data assimilation provides a compelling alternative to more common statistical analyses of flux data as it allows for the combination of many different sources of data, with the physical constraints of a dynamical model, to find an improved estimate of the state of a system. We develop new observation operators to assimilate daytime and nighttime net ecosystem exchange observations with a daily time step model, increasing observations available by a factor of 4.25. Our results support previous analyses, with a predicted net ecosystem carbon uptake for the year 2015 of 426 ± 116 g C m−2 for the unthinned forest and 420 ± 78 g C m−2 for the thinned forest despite a model‐predicted reduction in gross primary productivity of 337 g C m−2. We show that this is likely due to reduced ecosystem respiration postdisturbance compensating for a reduction in gross primary productivity. This supports the theory of an upper limit of forest net carbon uptake due to the magnitude of ecosystem respiration scaling with gross primary productivity.

Herbivory on young tree seedlings in old‐growth and managed mountain forests

AbstractHerbivory of invertebrates and rodents on tree seedlings in Northern temperate forests has been largely underestimated in the past and rarely addressed in studies. There is evidence that masting‐cycles of forest trees and subsequent rodents outbreaks become more frequent, leading to enhanced browsing pressure on forest regeneration. Consequently, studies exploring tree seedling mortality caused by different herbivores are required. We conducted a study on tree seedling losses in the Wilderness Area Dürrenstein, Austria on two old‐growth and one managed forest site. We conducted an exclosure experiment in two subsequent study years, using transplanted two‐month‐old tree seedlings of Picea abies, Abies alba, and Fagus sylvatica. Exclosures allowed access for invertebrates, invertebrates/rodents, and all potential herbivores. We also installed total exclosures, recording seedling losses due to climatic factors or pathogens. We calculated ZINB regressions assuming that seedling losses and seedling survival are distinct processes. Our results did not reveal fully consistent trends for both study years. The factor “treatment”, however, was significant in the ZINBs in both study years. Herbivory was a driving factor for tree regeneration in the studied forests depending on specific conditions in different years or tree species. In 2005, losses in the total exclosures and herbivory of rodents and invertebrates in the other treatments reached comparable extent. Loss rates differed not only in terms of forest management, but also between the two old‐growth forests. This, in connection with different herbivory of different tree species (higher losses of A. alba), strongly suggests the necessity of considering different herbivore guilds as drivers of tree species composition in late successional mountain forests.

Toward consistent measurements of carbon accumulation: A multi-site assessment of biomass and basal area increment across Europe

The use of tree-ring data in carbon cycle research has so far been limited because traditional study designs are not geared toward quantifying forest carbon accumulation. Existing studies that assessed biomass increment from tree rings were often confined to individual sites and used inconsistent sampling schemes. We applied a consistent biomass-oriented sampling design at five managed forest sites located in different climate zones to assess the annual carbon accumulation in above-ground woody tissues (i.e. stems and branches) and its climate response. Radial growth and biometric measurements were combined to reconstruct the annual biomass increment in individual trees and upscaled to the site level. In addition to this, we estimated that 32–60 trees are required at these five sites to robustly quantify carbon accumulation rates. Tree dimensions and growth rates varied considerably among sites as a function of differing stand density, climatic limitations, and management interventions. Accordingly, mean site-level carbon accumulation rates between 65gCm−2y−1 and 225gCm−2y−1 were reconstructed for the 1970–2009 period. A comparison of biomass increment with the widely used basal area increment (BAI) revealed very similar growth trends but emphasized the merits of biomass assessments due to species-specific BAI/biomass relationship. Our study illustrates the benefits and challenges of combining tree-ring data with biometric measurements and promotes the consistent application of a standardized sampling protocol across large spatial scales. It is thus viewed as a conceptual basis for future use of tree-ring data to approach research questions related to forest productivity and the terrestrial carbon balance.

Both forest fragmentation and coffee cultivation negatively affect epiphytic orchid diversity in Ethiopian moist evergreen Afromontane forests

The moist evergreen Afromontane forest of SW Ethiopia has become extremely fragmented and most of the remnants are intensively managed for cultivation of coffee (Coffea arabica), with considerable impacts on forest structure, biodiversity and ecosystem functioning. We assessed the effect of coffee forest management and forest fragmentation on epiphytic orchid diversity. We selected large and small intensively managed forest sites and compared their epiphytic orchid diversity with the diversity of natural unfragmented forest. We surveyed 339 canopy trees using rope climbing techniques. Orchid richness decreased and community composition changed, from the natural unfragmented forest, over the large managed forest fragments to the small managed forest fragments. This indicates that both forest management and fragmentation contribute to the loss of epiphytic orchids. Both the removal of large canopy trees typical for coffee management, and the occurrence of edge effects accompanying forest fragmentation are likely responsible for species loss and community composition changes. Even though some endangered orchid species persist even in the smallest managed fragments, large forest fragments are better options for the conservation of epiphytic orchids than small forests. Our results ultimately show that even though shade coffee cultivation is considered as a close-to-nature practice and is promoted as biodiversity conservation friendly, it cannot compete with the epiphytic orchid conservation benefit generated by large unmanaged moist evergreen Afromontane forests.

Response of Fagus sylvatica L. and Abies alba Mill. in different silvicultural systems of the high Dinaric karst

Among all silver fir forest types in Slovenia, most changes in forest composition are evident in Dinaric silver fir and beech forests, in which ageing and reduction of silver fir populations compared to European beech is evident. The situation has worsened due to a high browsing rate and environmental changes, causing a decline in abundance and a shift in silver fir′s spatio-temporal distribution. The photosynthesis response to different light and CO2 (max. photosynthetic rate –Amax, compensation points –Ic, quantum yield –Φ), the morphological response in young beech and fir to shade, and the growth response of adult trees were compared on sites with a single selection method, group selection method and old growth, during three consecutive vegetation periods (2009, 2010 and 2011). Three plots were established on each site, each with comparable light conditions according to the indirect site factor – ISF (%) under mature shelter, forest edge and open light conditions.In the old growth forest, beech and fir were more shade-tolerant and had a greater reaction to different light levels or elevated CO2 concentrations, compared to managed forest sites. Fir and beech express more physiological and morphological shade-tolerant characteristics on sites with single selection treatment, and differences are also evident in the growth responses of the two species. To establish conditions under which fir would be able to compete with beech, longer regeneration periods should be applied, with a gradual opening of the mature canopy, similar to conditions in old growth. In our study, group selection treatment proved more effective under the present environmental conditions.

Movements, cover-type selection, and survival of fledgling Ovenbirds in managed deciduous and mixed coniferous-deciduous forests

We used radio telemetry to monitor movements, cover-type selection, and survival for fledglings of the mature-forest nesting Ovenbird (Seiurus aurocapilla) at two managed forest sites in north-central Minnesota. Both sites contained forested wetlands, regenerating clearcut stands of various ages, and logging roads, but differed in mature forest composition; one deciduous with open understory, and the other mixed coniferous-deciduous with dense understory. We used compositional analysis, modified to incorporate age-specific limitations in fledgling movements, to assess cover-type selection by fledglings throughout the dependent (on adult care) post-fledging period. Compared to those that were depredated, fledglings from nests in deciduous forest that survived the early post-fledging period had more older (sapling-dominated) clearcut available, directed movements toward older clearcuts and forested wetlands, and used older clearcuts more than other cover types relative to availability. Fledglings that were depredated had more young (shrub-dominated) clearcut and unpaved logging road available, and used mature forest and roads more than expected based on availability. For birds from nests in mixed mature forest with dense understory, movements and cover-type selection were similar between fledglings that survived and those that were depredated. However, fledglings that were depredated at that site also had more young clearcut available than fledglings that survived. We conclude that Ovenbird fledgling survival is influenced by distance of their nest to various non-nesting cover types, and by the subsequent selection among those cover types, but that the influence of non-nesting cover types varies depending on the availability of dense understory vegetation in mature forest.

Mountain beaver home ranges, habitat use, and population dynamics in Washington

The mountain beaver ( Aplodontia rufa (Rafinesque, 1817)), endemic to western North America, is the only extant member of the family Aplodontidae. Limited information on movements and habitat use throughout the species’ range is available. We radio-collared 41 mountain beavers to determine home ranges, dispersal, habitat use, and population densities on two managed forest sites in coastal Washington. Both sites were recently harvested for timber. The Donovan site (16.6 ha) was treated with herbicide before seedling planting and the Sylvia site (8.9 ha) was not treated. Mountain beaver home ranges (Donovan: 4.18 ± 0.81 ha; Sylvia: 1.39 ± 0.4 ha) were greater than previously reported in the literature (0.02–0.2 ha). Home ranges (P = 0.009) and core use areas (P = 0.05) on the herbicide-treated Donovan site were larger than those observed on the untreated Sylvia site. Mountain beaver population density declined from 2002 (n = 16) to 2003 (n = 8) on the Donovan site, and reinvasion onto the site after removal trapping was low (n = 7). Population density more than doubled on the Sylvia site from 2002 (n = 21) to 2003 (n = 55), and reinvasion was greater (n = 27) than observed at Donovan. In addition, we documented habitat characteristics centered at 9 Donovan and 10 Sylvia nest locations. Sites were similar in most habitat characteristics, but the Sylvia site had more herbaceous forbs, stumps, and woody debris. Our findings suggest that mountain beaver populations and home ranges are affected by availability of forage, such as herbaceous forbs, after herbicide treatment, as well as by availability of woody cover.

Life History of the Southern Torrent Salamander (Rhyacotriton variegatus) in Coastal Northern California

Southern Torrent Salamanders (Rhyacotriton variegatus) range widely from north coastal Oregon to northern California but are a patchily distributed inhabitant of forested seeps and headwater springs. We collected bimonthly samples of this species from managed forest sites in the Mad River watershed, Humboldt County. Larvae were measured, marked, and released, but a limited number of transformed individuals were preserved for laboratory analyses. North coastal R. variegatus breeds annually and has an extended courtship and egg-laying period. Cloacal spermatophores were present in gravid females from February through June, and oviposition likely occurs spring through fall. A prolonged larval period (hatching to metamorphosis) lasts 2–2.5 yr; transformed females require another 1.5–2 yr until first breeding, and clutch size averages 7.5 eggs. Adult sizes, size at metamorphosis, and developmental times were comparable to north coastal Oregon R. variegatus, suggesting that a simple north-south, harsh-mild environmental cline does not influence developmental time for coastal populations. Unexpectedly, clutch size and size-fecundity relationships for the California population of R. variegatus were more similar to Rhyacotriton cascadae, an inland, northern species with longer larval periods and larger sizes at metamorphosis, than to R. variegatus in north coastal Oregon. Rhyacotriton variegatus has limited rates of population increase because of long generation times and low fecundities and could be highly sensitive to frequent disturbances that impact numbers.

Gap evapotranspiration and drainage fluxes in a managed and a virgin dinaric silver fir–beech forest in Slovenia: a modelling study

The monthly water balance in gaps in a managed Dinaric silver fir–beech forest and a virgin forest remnant located in SE Slovenia was modelled using a capacity water balance model for two growing seasons. Two gaps of different size (ca. 0.07 and 0.15 ha) were selected in each forest and plots for soil moisture monitoring were established in each gap (2–4) and in the surrounding forest (2–3). We report on the modelled actual evapotranspiration (AET) and potential evapotranspiration (PET) and drainage fluxes (DF) from the rooting zone at the plots. Precipitation over the 2001 growing season (May–October) was considerably drier than average and that for 2002 growing season was wetter than average. Modelled AET for the 2001 growing season varied between 88% and 96% of PET for the managed forest plots and between 90% and 100% for the virgin forest plots. The values for the gap plots varied between 87% and 100% at the managed forest site and between 92% and 96% for the gaps in the virgin forest site. Monthly AET values declined to 57–59% of PET at plots in the centre of the gaps in the managed forest site and to 63–74% in the gaps in the virgin forest site (July), indicating that the highest drought stress occurs in gap centres. For 2002 growing season, AET for all plots was 100% of PET. Modelled DF values in 2001 were 13–35% of rainfall for plots in the gap centres and 12–16% for plots in the forest at the managed forest site. On an average, gap DF values were 20% (154 mm) higher than the forest plot values. DF values in 2002 were similar for all plots at the managed forest site, 31–33% of rainfall. At the virgin forest site, 2001 growing season, DF values varied between 12% and 30% of rainfall at the forest plots and between 12% and 32% at the gap plots. In 2002, DF values for all plots in the virgin forest site varied between 24% and 38% of growing season rainfall. The varying development of vegetation and forest in the gaps of the virgin forest remnant resulted in more variable evapotranspiration and DF during the drought year 2001, with values not as clearly related to distance from the gap centre as in the managed forest site.

Spatial variation of arthropod communities in virgin and managed sites in the Kibale Forest, western Uganda

The structure of arthropod communities in the forest floor vegetation in four differently managed forest sites (virgin forest, lightly selectively logged, heavily selectively logged, and exotic Pinus caribaea plantation) in Kibale Forest National Park, western Uganda, was studied by sweep net between March and May 1985 and July 1995. For the analysis three (or four) 800 sweeps samples were collected from each habitat. In the samples eight arthropod groups (Araneae, Hymenoptera, Heteroptera, Homoptera, Coleoptera, Orthoptera, Lepidoptera, caterpillars (Lepidoptera larvae)) formed over 95% of all the individuals of the arthropod caught in all habitats. The variation within one habitat was smaller than variation between habitats in samples of the same year. Thus, the arthropod communities in differently managed forests differ from each other after over 20 years of management practices (selective logging and clear-cut plus pine plantation) as well as from adjacent virgin forest, and the differences seem to become greater during the succession in managed sites. Samples taken in the same habitat type, 10 years apart, differed greatly from each other. This is the result of both long-term succession and seasonal variation.

Long-term forest utilization can decrease forest floor microhabitat diversity: evidence from boreal Fennoscandia

Forest floor microhabitat diversity was studied in old Pinus sylvestris L. dominated forest sites in two regions within the middle boreal vegetation zone in Fennoscandia: in 50 managed forest sites in the Häme region in southwestern Finland and in 45 natural or old selectively logged forest sites in the Kuhmo–Viena region in northeastern Finland and northwestern Russia. The forests in the Häme region are characterized by a long history of forest utilization, while the forests in the Kuhmo–Viena region can be regarded as natural or near natural. The managed forest sites in Häme had significantly lower forest floor microhabitat diversity compared with natural and near-natural forests. Microhabitats that were significantly more scarce in managed versus natural and near-natural forest sites included humps, depressions, decayed wood, and vicinity of decayed wood. On the other hand, even ground was significantly more abundant in managed forest compared with natural and near-natural forest. Microhabitat availability was also reflected in the occurrence of tree saplings growing in different microhabitats. The results suggest that long-term forest utilization has decreased forest floor microhabitat diversity. This has occurred because of a decreased amount of fallen deadwood and, possibly, lack of soil disturbances because of fewer uprootings caused by falling trees.