Old Forests Research Articles

Understory Response to Repeated Thinning in Douglas-fir Forests of Western Oregon

This study investigated effects of a second-thinning entry on understory vegetation and tree regeneration development and understory vegetation composition. Study sites were located in the Coast Range and Cascade Range mountains of western Oregon and were dominated by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests. Stands were initially thinned between 1975 and 1982 and parts of these same stands were thinned again approximately 20 yr later. Thinning stands a second time resulted in greater amounts of fern, graminoid, and open-site species, but the abundance of tree regeneration was not affected. Despite different site conditions, compositional patterns in the understory consistently shifted toward open-site early seral species following the second thinnings. These results suggest that the initial impacts of a second thinning are not simply predictable from studies in which only a single thinning was implemented. It is important to consider that vegetation trends were already influenced by the previous thinnings, and impacts of the second thinning are thus not as easily detectable. Within these limitations, repeated thinnings may be an effective management tool to maintain early seral species in older forests, while other aspects of understory vegetation and tree regeneration are less influenced in the short term.

Spatial Analysis of Northern Goshawk Territories in the Black Hills, South Dakota

The Northern Goshawk (Accipiter gentilis) is the largest of the three North American species of Accipiter and is more closely associated with older forests than are the other species. Its reliance on older forests has resulted in concerns about its status, extensive research into its habitat relationships, and litigation. Our objective was to model the spatial patterns of goshawk territories in the Black Hills, South Dakota, to make inferences about the underlying processes. We used a modification of Ripley's K function that accounts for inhomogeneous intensity to determine whether territoriality or habitat determined the spacing of goshawks in the Black Hills, finding that habitat conditions rather than territoriality were the determining factor. A spatial model incorporating basal area of trees in a stand of forest, canopy cover, age of trees >23 cm in diameter, number of trees per hectare, and geographic coor- dinates provided good fit to the spatial patterns of territories. There was no indication of repulsion at close distances that would imply spacing was determined by territoriality. These findings contrast with those for the Kaibab Plateau, Arizona, where territoriality is an important limiting factor. Forest stands where the goshawk nested historically are now younger and have trees of smaller diameter, probably having been modified by logging, fire, and insects. These results have important implications for the goshawk's ecology in the Black Hills with respect to mortality, competi- tion, forest fragmentation, and nest-territory protection.

Changes in bird assemblages during succession following disturbance in secondary wet forests in south-eastern Australia

After a successional forest is severely disturbed by wildfire and subsequent salvage logging or by clearfell timber harvesting and slash burning, if conditions are suitable, the forest will regenerate. It then passes through a series of stages of varying floristic composition and structure until further severe disturbance occurs. The characteristics of a forest-bird assemblage vary with both the successional stage of the forest (time period since the most recent severe disturbance event) and the long-term disturbance history of the forest. To determine how the bird assemblage changes during succession in a south-eastern Australian forest type that is fire-sensitive and also subject to regular timber harvesting, we surveyed birds in five age-classes of wet forest (from 2 to >100 years post-disturbance). Bird-assemblage composition altered sequentially; the pattern and rate of change reflected those of the vegetation. Bird abundance and species richness varied little during succession. No species of bird was abundant only in early successional forest. Some species, such as Brown Thornbill (Acanthiza pusilla), Golden Whistler (Pachycephala pectoralis) and Grey Fantail (Rhipidura albiscapa), were common in all successional stages. Other species, such as White-throated Treecreeper (Cormobates leucophaea) and Striated Pardalote (Pardalotus striatus), were consistently abundant in mid-to late successional stages only; this highlighted the importance of older forests for avian biodiversity. Any increase in the frequency of severe disturbance in these forests would tend to favour only those bird species that are already common. This has implications for management programs in forests that are habitat for wildlife, but are also used by humans for timber harvesting and other commercial or recreational purposes.

Life-history traits explain rapid colonization of young post-agricultural forests by understory herbs

Large areas of agricultural land in Europe have been planted with broadleaved trees during the past decades. The aims of this study were to determine stand-scale colonization rates of European forest herbs in young (14–18years old) post-agricultural broadleaved forest plantations, to analyze whether colonization rates were related to life-history traits and site characteristics, and to compare the results with studies in older post-agricultural forests. The colonization of herbaceous forest species was mapped in 16 young broadleaved forests and compared with their distribution in adjacent older forests in southern Sweden. Stand characteristics were analyzed in 32 paired sample plots. Colonization rates (myear−1) were calculated for 43 forest plant species. For 30 forest plant species we also compared current colonization rates with results from 30 to 75year old stands. Colonization rates increased with maximum plant height and the potential dispersal distance, but were negatively related to diaspore mass and clonal spread. Soil, canopy and vegetation conditions in young forests were not significantly related to colonization rates. Nevertheless, young forests had higher soil pH and extractable phosphorus concentrations while soil organic matter content, basal area and canopy cover of the trees were higher in the adjacent older forests. Higher resource availability in young forests may favor competitive tall herbs over low-growing ancient forest plants. The comparison with colonization rates into older post-agricultural plantations revealed that while approximately half of the species had similar or lower rates, the other half had on average ca. ten times higher colonization rates in the present study, ranging from 3.0 to 11.5myear−1 indicating the potential for relatively fast colonization by some forest plants. We conclude that planted post-agricultural forests can start to contribute to restoration of forest plant diversity shortly after canopy closure when located adjacent to older forests. However, many small forest plants, including those species which form extensive flower carpets characteristic of ancient forests, colonize young forests very slowly. Further research should focus on the development of restoration measures which facilitate the colonization process of ancient forest herbs.

Edaphic Factors are a More Important Control on Surface Fine Roots than Stand Age in Secondary Tropical Dry Forests

AbstractAlthough there are generalized conceptual models that predict how above and belowground biomass increase during secondary succession after abandonment from agriculture, there are few data to test these models for fine roots (defined as ≤2 mm diameter) in tropical forests. We measured live and dead fine roots (0–10 cm depth) in 18 plots of regenerating tropical dry forest in Costa Rica that varied in age from 5 to 60 yrs, as well as in soil properties. We predicted that both stand age and soil fertility would affect fine roots, with greater values in older forests on low fertility soils. Across two sampling dates and locations, live fine roots varied from 0.35 to 3.53 Mg/ha and dead roots varied from 0.15 to 0.93 Mg/ha. Surprisingly, there was little evidence that surface fine roots varied between sampling dates or in relation to stand age. By contrast, total, live, and dead fine roots averaged across sampling dates within plots were negatively correlated with a multivariate index of soil fertility (Pearson correlations coefficients were −0.64, −0.58, and −0.68, respectively; P < 0.01) and other individual edaphic variables including pH, silt, calcium, magnesium, nitrogen, and phosphorus. These results suggest that soil fertility is a more important determinant of fine roots than forest age in tropical dry forests in Costa Rica, and that one‐way these plant communities respond to low soil fertility is by increasing fine roots. Thus, simple conceptual models of forest responses to abandonment from agriculture may not be appropriate for surface fine roots.

Effect of forest harvesting on hydrogeomorphic processes in steep terrain of central Japan

Forest harvesting activities affect various hydrogeomorphic processes in forest terrain, including increases in occurrence of mass movements (i.e., landslides and debris flows), and changes in sediment transport rate in channels. Thus, the influence of harvesting on these processes needs to be assessed to protect aquatic ecosystems. In steep terrain with frequent mass movement, relationships between rainfall magnitude and frequency of mass movements associated with forest harvesting are needed to develop improved strategies for disaster prevention. We examined the effects of forest harvesting on the frequency of mass movements in the steep Sanko catchment (central Japan) using aerial photographs for six different years covering 1976 to 2003. We also investigated the spatial distribution of sediment stored in the system as well as sediment transport rate in selected subcatchments by field surveys. Landslides occur during moderate rainfall events (return period of daily rainfall<10years) in younger forests (<25years after harvesting), whereas the threshold magnitude of rainfall for landslides is higher in older forests (>25years after harvesting). The occurrence of mass movements substantially altered the volume of sediment storage in the channel that links sediment supply from hillslopes with sediment yield downstream. However, the volume and spatial distribution of sediment deposits in headwater channels were not clearly related to forest age because of the redistribution and evacuation of sediment by debris flows. Bedload transport rate was highly affected by sediment storage volume, whereas suspended sediment concentration was affected by the area of exposed sediment along channels that was carved by debris flows. Thus, the effect of harvesting on hydrogeomorphic processes cannot be estimated simply by the elapsed time after forest harvesting; rainfall magnitude and the history of mass movements need to be considered to better understand these linkages.

The Grain for Green Project induced land cover change in the Loess Plateau: A case study with Ansai County, Shanxi Province, China

The Grain for Green Project (GGP) is the largest land retirement/afforestation program in China; it was primarily initiated to reduce the soil erosion and improve the ecological conditions in the Loess Plateau in 1999. If effective, this massive regional effort will induce significant improvement in the vegetation conditions. At this time, the effectiveness of the GGP has not been well documented. Using Ansai County as a case study, we characterized the impact of the GGP on the land covers and landscape characteristics of this area by using multi-temporal Landsat MSS, TM and ETM+ images of 1978, 1990, 1995, 2000, 2005 and 2010. The results indicate that the land cover patterns and landscape characteristics in the county were greatly altered in a considerably short period. The implementation of the GGP increased the newly forested land substantially to 21.4% of the study area by 2010 at the cost of both cropland and shrub–grassland, which decreased by 46.3% and 18.8%, respectively, from 1995 to 2010. Consequently, the coverage of forested land (both older forest and newly forested land) increased from 12.4% in 1995 to 37.7% in 2010. Moreover, the GGP increased landscape fragmentation as indicated by a decreasing mean patch size and changes in class-level landscape indicators varied with land cover categories. The GGP induced improvement in vegetation conditions may benefit soil erosion alleviation and carbon sequestration in the Loess Plateau. However, the potential for the GGP to provide long-term positive ecological effects requires further study.

Integrating forest biomass and distance from channel to develop an indicator of riparian condition

Living and detrital biomass in a riparian buffer zones ameliorate diffuse-source pollution originating from adjacent landscapes, with higher nutrient removal potential, particularly with respect to nitrogen and sediments, associated with more biomass (i.e., older forests). Pollution removal is mediated by sediment trapping and uptake of nitrogen by plants and by denitrification by microbial communities in root zones using organic matter and root exudates as energy sources. However, as a consequence of various land management activities, the amount of biomass of most forest riparian zones is much lower than its potential, which is mature forest. This makes restoration of riparian buffer zones to mature forest an ideal way to both improve water quality and increase carbon sequestration. This study measures the amount of biomass aboveground and in soils for a variety of common, age-related condition-types associated with riparian buffer zones along low order (headwater) streams in agricultural landscapes of Coastal Plain North Carolina. The data are used to determine pollution removal potential in relation to stand age and distance from channel and a basis for developing an indicator of riparian condition. Mean biomass for common riparian cover types were Mature Forest (>50 y old): 483Mg/ha; Young Forest (25–50 y old): 257Mg/ha; Regenerating Forest (5–25 y old): 205Mg/ha; recently Harvested Forest (0–5 y old): 165Mg/ha; Perennial Herb: 67Mg/ha; Shrub/Sapling: 63Mg/ha; and Annual Rowcrop: 36Mg/ha. Trees contained >96% of all aboveground biomass and >58% of total biomass present in the forested conditions. Biomass in recently harvested forests were >97% detrital, mostly due to the large amount of slash left after harvesting and the mostly intact soil organic matter. Most (>80%) of the biomass in non-forest cover types was stored in the detrital pool. By partitioning the riparian zone into inverse distance-weighted subzones based on distance from stream channel, we developed an indicator for determining riparian condition based on both biomass and proximity of biomass to channel.

Moving in three dimensions: effects of structural complexity on occurrence and activity of insectivorous bats in managed forest stands

Summary1. Forest management determines to a large degree the three‐dimensional arrangement of the vegetation in production forest systems and hence has an essential influence on habitat quality for wildlife. We investigated the effects of forest structure on occurrence, activity and species composition of European bats, an ecologically important group of vertebrates known to be affected by the physical clutter of vegetation.2. Species composition and activity of bats were assessed with acoustic monitoring on 50 one‐hectare experimental plots in a biosphere reserve in Germany. Three‐dimensional forest structure was assessed by Light Detection and Ranging (LiDAR), and a set of 20 mathematically derived and fine‐grained structural parameters with a minimum of collinearity was used for a quantitative description of the vegetation structure.3. Occurrence and activity of bats were positively associated with the structural parameters canopy height, standard deviation of the canopy surface roughness and edge fraction, indicating older forest stands with patches of different vegetation heights. In addition, species composition in differently managed forest stands was significantly influenced by the relative proportion of structural parameters. Species of one functional group, sharing similar adaptations in wing morphology and foraging strategy, showed similar associations with three‐dimensional structural parameters. In addition, we found species‐specific structural parameter associations explaining the occurrence and activity levels of individual species in differently managed production forest types.4. Synthesis and applications. High‐resolution LiDAR data are an important tool to assess structural habitat suitability for bat species. Our data revealed that bat occurrence and activity increases with structural heterogeneity in managed forest stands. Given, that bats provide an essential ecosystem service through top‐down control of herbivorous insects, increasing stand structural heterogeneity through management practices (e.g. selective harvesting) is a very effective strategy to assure vital ecosystem functioning in production forest systems.

Soil CO2 concentration and efflux from three forests in subtropical China

Measurements of soil CO2 efflux and soil CO2 concentration concurrently are important for understanding the mechanism and regulation of CO2 in the soil. We have analysed CO2 concentration in a soil profile and soil CO2 efflux in three typical forests in subtropical China: monsoon evergreen broad-leaved forest (BF, 400 years old), pine and broad-leaved mixed forest (MF, 80 years old), and pine forest (PF, 70 years old). A portable soil CO2 sampler of simple sample operation was designed and used. The seasonal patterns of soil surface CO2 efflux and soil CO2 concentration were observed, and were positively correlated with rainfall, soil temperature, and moisture. The mean values of soil CO2 concentrations at the 15, 30, 45, and 60 cm soil depth were higher in BF (3368–9243 μL L–1) than in MF (1495–7662 μL L–1) and PF (1566–5730 μL L–1), while the mean values of soil surface CO2 efflux (Rsurface) were 0.55 ± 0.11 g m–2 h–1 in BF, 0.52 ± 0.10 g m–2 h–1 in MF, and 0.45 ± 0.07 g m–2 h–1 in PF. Soil CO2 concentration and Rsurface increased gradually with the age of the forests, but the incremental increase in soil CO2 concentration will be greater than that of Rsurface in MF and PF compared with BF. The data suggested that, although older forests have more C, younger forests probably will sequester C as CO2 faster than older forests.

Patterns of Patch Colonization and Expansion In the Non-Native Annual Grass Microstegium vimineum (Poaceae)

Identifying the areas most vulnerable to a species' invasion within a habitat or region is crucial to managing and minimizing that species' eventual effect. The exotic annual grass Microstegium vimineum often occurs in the greatest density along disturbed corridors, such as waterways and trails, within otherwise undisturbed forests. We tested the hypothesis that such linear features within forests are correlated with invasion patterns. We surveyed linear transects along intermittent streams and foot trails through eight upland forests of different ages, as well as control transects within each forest that were distant from any type of linear feature. We documented significantly larger and denser patches of M. vimineum along transects in young forests than those in old stands. Streams and trails were similarly more invaded than control transects, and M. vimineum was distributed much more patchily away from such corridors. Isolated individual patches of M. vimineum (along neither streams nor trails) demonstrated the potential to expand at approximately 1 m over 1 y, although 11% of plants appeared farther than 2 m from their parent patch. Although germinants appeared downslope of the parent patch two to four times more frequently than upslope, the mean distance of spread was equivalent in both directions. Control efforts should focus on excluding the species from corridors that could allow entry, particularly in older forests.

Contemporary mature forest cover does not explain the persistence of Capercaillie (Tetrao urogallus) lekking areas in Finland

Capercaillie (Tetrao urogallus) has traditionally been considered an old forest-dependent species. The lekking sites especially,were thought to be located in older forests. We studied the persistence of Capercaillie lekking areas in relation tomature forest cover at three study areas in Finland (southwestern, SW; central, CE; and northern, NO). Atotal of 381 leks were inspected twice at intervals of 10-30 years and were classified as either persisting or vacated. We defined mature forest as forest with &gt; 152 m 3ha -1 of timber (SW and CE Finland) or &gt; 68 m 3ha -1 of timber (NO Finland). We measured mature-forest cover within two radii around the leks (1,000 and 3,000m) using satellite image-based forest inventories, and performed logistic regression analyses on these data. We did not find significant trends between mature-forest cover and lekking-area persistence in any of the study areas. However, the proportion of mature forestsmay have already been too low to detect the significance of this factor. The only significant factor affecting the lekking-site persistence was time lag between surveys. The positive relationship between the time lag and lekking-site persistence in CE and NO Finland may be due to the partial recovery of the landscapes in terms of forest regrowth, from extensive clear-cut harvesting in the 1950s and 1960s. In SWFinland, the relationship was negative, possibly indicatingmore permanent changes in the landscape that is currently characterized by human settlements and agricultural areas. We conclude that in present-day Finland, the area covered by mature forest ismost likely too scarce to explain the lekking-area persistence ofCapercaillie. An alternative explanation is that some important structural characteristics are missing from the current mature forests.

The Legacy of Logging—Estimating Arboreal Lichen Occurrence in a Boreal Multiple-Use Landscape on a Two Century Scale

In northern Sweden, the availability of arboreal lichens (Bryoria fuscescens, Alectoria sarmentosa) as winter grazing resources is an important element in reindeer husbandry. With the industrialization of forestry, forests rich in arboreal lichens have diminished considerably. Here, we analyze how forestry has impacted lichen availability from the 1920's to the present day and model its future development assuming different forest management scenarios.We recorded the current occurrence of B. fuscescens in 144 sampling plots, stratified by forest age class and dominant tree species in a 26,600 ha boreal forest landscape that is used for both reindeer herding and forestry. Lichen abundance was visually estimated in four classes: none, sparse, moderate and abundant. A binary logistic model using forest age as the independent variable was developed to predict the probability of lichens being present. Using this model, we found that lichens were present in stands that are at least 63 years old. Because of the relative paucity of stands rich in arboreal lichens, it was not possible to reliably determine how age affects the variation in abundance of older forest stands. The historical development of forests where arboreal lichens could potentially occur was studied using historic forestry records dating back 80 years. Between 1926 and the present day, forestry has reduced the cover of forests older than 60 years from 84% to 34%. The likely future spatial coverage of these stands over the next 120 years was estimated for two different management scenarios and an unmanaged reference scenario, using the Heureka strategic planning program. Under both the “business as usual” scenario and that involving more intensive forestry, continued decreases in lichen availability are projected. Our results emphasize the importance of alternative forestry practices, such as prolonged rotation periods, to increase the availability of arboreal lichens as a grazing resource for reindeer.

Mapping change of older forest with nearest-neighbor imputation and Landsat time-series

The Northwest Forest Plan (NWFP), which aims to conserve late-successional and old-growth forests (older forests) and associated species, established new policies on federal lands in the Pacific Northwest USA. As part of monitoring for the NWFP, we tested nearest-neighbor imputation for mapping change in older forest, defined by threshold values for forest attributes that vary with forest succession. We mapped forest conditions on >19millionha of forest for the beginning (Time 1) and end (Time 2) of a 13-year period using gradient nearest neighbor (GNN) imputation. Reference data were basal area by species and size class from 17,000 forest inventory plots measured from 1993 to 2008. Spatial predictors were from Landsat time-series and GIS data on climate, topography, parent material, and location. The Landsat data were temporally normalized at the pixel level using LandTrendr algorithms, which minimized year-to-year spectral variability and provided seamless multi-scene mosaics. We mapped older forest change by spatially differencing the Time 1 and Time 2 GNN maps for average tree size (MNDBH) and for old-growth structure index (OGSI), a composite index of stand age, large live trees and snags, down wood, and diversity of tree sizes. Forests with higher values of MNDBH and OGSI occurred disproportionately on federal lands. Estimates of older forest area and change varied with definition. About 10% of forest at Time 2 had OGSI>50, with a net loss of about 4% over the period. Considered spatially, gross gain and gross loss of older forest were much greater than net change. As definition threshold value increased, absolute area of mapped change decreased, but increased as a percentage of older forest at Time 1. Pixel-level change was noisy, but change summarized to larger spatial units compared reasonably to known changes. Geographic patterns of older forest loss coincided with areas mapped as disturbed by LandTrendr, including large wildfires on federal lands and timber harvests on nonfederal lands. The GNN distribution of older forest attributes closely represented the range of variation observed from a systematic plot sample. Validation using expert image interpretation of an independent plot sample in TimeSync corroborated forest changes from GNN. An advantage of imputed maps is their flexibility for post-classification, summary, and rescaling to address a range of objectives. Our methods for characterizing forest conditions and dynamics over large regions, and for describing the reliability of the information, should help inform the debate over conservation and management of older forest.

Understory succession in post-agricultural oak forests: Habitat fragmentation affects forest specialists and generalists differently

The herbaceous understory forms the richest stratum in temperate broadleaved forests in terms of plant diversity. Understanding the process of understory succession is thus of critical importance for the development of management guidelines for biodiversity restoration in post-agricultural plantation forests. We studied effects of stand age, forest fragmentation, and soil and canopy conditions on species richness and abundance of four species groups in the understory of post-arable oak plantations in southern Sweden: herbaceous forest specialists, habitat generalists and open-land species, and woody species. The group of forest specialists may approach the richness of continuously forested sites after 60–80 years in non-fragmented plantations, but many forest species were sensitive to habitat fragmentation. Open-land species richness decreased during succession, while the richness of woody species and of generalists remained stable, and was not affected by fragmentation. Abundance of generalists gradually decreased in non-fragmented plantations, probably due to competition from colonizing forest specialists. Soil pH in post-arable stands remained consistently higher than in continuously forested stands, which maintained differences in species composition. The development of a shrub layer seemed to imply a competitive advantage for forest specialists compared to generalist species. For successful recovery of a rich understory, we suggest that post-arable plantations should be established on loamy soils of intermediate to high pH proximate to older forest with source populations, and that a continuous overstory canopy cover of 70–80% is maintained by regular light thinnings and promotion of a shrub layer.

Canopy Structure in a 650-Year Douglas-Fir Chronosequence in Western Washington: Distribution of Canopy Elements and Open Space

Abstract Using within-canopy, side-viewing light detection and ranging (LiDAR), we measured canopy structure in a Douglas-fir (Pseudotsuga menziesii) chronosequence. We present foliage profiles, canopy composition, and a new metric quantifying the vertical distribution of open space, supporting and extending results from other structural studies. Foliage distribution shifted from vertically uniform in the youngest stand (50 years), to a canopy surface peak in mature forests (100–160 years old), to a near-ground maximum in old-growth (650 years). Leaf area index in old-growth and mature forests was similar but was smaller in young forest. Canopy composition changed with age: relatively more dead elements in young, boles in mature, and diversity in old-growth canopies. Older forest had greater mean and variance in open space than younger forests. Open space was vertically uniform in young, unimodal in mature, and greatest in the upper canopy in old-growth forests. Our results provide an integrated description of canopy structure over more than half a millennium, highlighting solid structure and its complement, open space. The unique element we present—open space—provides novel insights into the assessment of forest structure. This study provides a means to compare forests across ages, from immature to old-growth, with an additional canopy variable available for developing relationships between canopy structure and function.

Delineation of secondary succession mechanisms for tropical dry forests using LiDAR

Research suggests that secondary forest structure and composition subsequent to human disturbance could be related to wind or vertebrate dependent seed dispersal mechanisms. This paper examines the capability of a waveform LiDAR system (LVIS: LiDAR Vegetation Imaging System) to detect the location of wind-dispersed or vertebrate-dispersed forest patches in a mosaic of a secondary Tropical Dry Forest in the Santa Rosa National Park, Guanacaste, Costa Rica. Canopy-height estimations derived from LVIS data were used to identify and locate two types of dispersal-dependent arrangements of canopy heights: flat-topped (windborne seed dispersed) or dome-shaped (vertebrate-dispersed) fragments. Following identification, a Ripley's K indicator was used to compare the locations for each confirmed canopy type to those reported in existing maps. Results indicated that dome-shaped patches tended to be arranged in clusters at the middle of former pastures (far from older forests), and that flat-topped patches tended to be located adjacent to older forests, forming extensions from the old growth patches and at the downwind side of the slope. Such characteristics agree with the theoretical observation of the spatial configuration of vertebrate- and wind-dispersed fragments reported in the study site. Our findings demonstrate that processes controlling forest regeneration in the TDF can be successfully identified through LiDAR data.

Carabid beetle diversity and mean individual biomass in beech forests of various ages

Carabid beetle diversity and mean individual biomass (MIB) were analysed in three different successional stages of beech tree stands (60, 80 and 150 years old). Carabid beetles were captured using pitfall traps placed at nine sites (three per age class) in the Papuk Mountain of East Croatia during 2008. A cluster analysis identified three groupings that corresponded to the beech age classes. MIB values increased with stand age, ranging from 255 in 60-year-old stand to 537 in the oldest forests. The 80-year-old stand showed the highest species richness and diversity values. With respect to species composition, large species such as Carabus scheidleri and Carabus coriaceus were dominant only in the oldest forests. Furthermore, species that overwinter in the larval stage were more abundant in the oldest forests (45% of the total number of individuals from the 150-year-old stand) than in the younger ones (20% of individuals from 60-year-old, and 22% of individuals from 80-year-old stands). Our results showed that the analyses of species composition and life history traits are valuable for estimating the conservation values of older forests. Although the investigated sites form part of a continuous forested area and are only a couple of kilometres apart, MIB values detect significant differences associated with forest age and can be a useful tool in evaluating the degree to which a forest reflects a natural state.

Moose Alces alces habitat use at multiple temporal scales in a human‐altered landscape

AbstractHabitat alteration by humans may change the supply of food and cover for wild ungulates, but few studies have examined how these resources are utilised over time by individuals of different sex and reproductive status. We examined circadian and seasonal variation in habitat utilisation within a moose Alces alces population in central Norway. Our study area covers forests and open habitats, both influenced by human alterations (e.g. forestry and agriculture). We expected moose to select habitats with good forage and cover in all seasons, but to select open foraging habitats mainly during night‐time. Moose selected good foraging habitats, such as young forest stands and cultivated land during night, whereas the utilisation of older forest stands providing cover increased during daytime. This circadian pattern changed throughout the year, seemingly related to variation in hours of daylight and provision of forage. Young forest stands provided higher density of preferred food plants compared to older stands and were highly selected from spring until autumn. Relative to young forest, the selection for older forest stands increased towards winter, likely due to provision of higher plant quality late in the growing season, and to reduced accumulation of movement‐impeding snow during winter. Selection of cultivated land varied among seasons, being highest when crop biomass was high. We also found some indications of state‐dependent habitat selection as reproducing females avoided open, food rich areas in the first months after their calves were born, whereas males and females without young selected these areas in spring and summer. Our results clearly show that moose exploit the variations in cover and food caused by forestry and agriculture. This is particularly relevant for moose in Norway as current changes in forestry practice lead to a reduction in young, food‐rich forest stands, possibly aggravating the already declining body conditions and recruitment rates of moose.

Historic variability in fire-generated landscape heterogeneity of subalpine forests in the Canadian Rockies

Question: This study evaluates historical changes in landscape structure and heterogeneity in subalpine forests. We use response to severe fires in 2001 and 2003, along with historical reconstructions to examine crown-fire effects on landscape heterogeneity and to assess, comparatively, effects of fire exclusion management in the 20th century. Location: Subalpine forests of Kootenay National Park (KNP), Canadian Rockies. Methods: Using a landscape-level model based on a fire-origin stand age map, we reconstructed decadal burned areas within the landscape for 1750-2000 (forming reconstructed landscapes). Landscape pattern was analysed for each reconstructed landscape map, and we compared landscape pattern indices (total area, number of patches, mean patch area, patch area variation, largest patch index, edge density, perimeter–area ratio, landscape shape index) with those in 2005 after recent large fires. Results: After large fires in 1926, connectivity of the KNP landscape increased and its diversity was quite low. After 2001 and 2003 fires, the post-fire landscape of 2005 was highly heterogeneous in terms of size, variation, edge density and perimeter–area ratio of the remnant forest patches. Since the decline in occurrence of large fires after 1926 reflected a period of wet weather, fuel build-up resulting from landscape homogenization within the 20th century landscape could not be attributed solely to fire exclusion. This period without fires greatly enhanced connectivity of late-successional forests that finally burned in 2001/2003, but connectivity was within the historical range for these forests. The gradual increase in stand connectivity before recent large fires may indicate that fire exclusion was less responsible than often believed for fuel build-up in these fire-susceptible older forests. Conclusions: The large fires at the beginning of the 21st century are within the natural range of disturbances for this landscape, and do not stand out as “human-induced disasters” in their effects on landscape patterns. Such stochastic large disturbances contribute to maintenance of highly heterogeneous landscape structure, which is important for many taxa and natural ecological processes. Identifying future probability of such large disturbances and their ecological roles should be incorporated into management of these dynamic, disturbance-prone systems.