Structural and environmental characterization of old-growth temperate rainforests of northern Chiloé Island,Chile: Regional and global relevance

Old-growth forests are ecologically relevant reservoirs of biodiversity and provide valuable and unique ecosystem functions in the landscape. However, what constitutes an old-growth stand is confusing because the definition depends largely on the forest type under study. Despite the ecological importance of old-growth temperate rainforests in southern Chile in comparison to other global forests, no attempts have been made to characterize them as a way to assess their structural variability. Here, we characterized old-growth stands of Valdivian and North Patagonian rain forest types located in Chiloé Island (Chile, 42°30′S) using inventory data from 23 permanent plots (0.1 ha each) located in rural landscapes and protected areas of northern Chiloé Island. For each stand, its age (average age of the oldest trees present in each stand) and disturbance regimes (evidence of recent human impact, e.g. cuttings or fires, and tree growth rates) were used as defining old-growth criteria. We characterized the structure (tree species richness, size-density distributions, vertical stratification and presence of snags) and floristic composition of each stand. Environmental variables (i.e. temperature, distance to coastline and elevation) were related to stand structure using multivariate constrained correspondence analysis. Old-growth forests were commonly characterized by (a) tree basal areas >80 m²/ha; (b) density of shade-tolerant tree species in the emergent and dominant canopy layer >36%; (c) higher tree species richness (>7 tree species) than successional stands; (d) presence of large canopy emergents (>80 cm dbh, >25 m tall); (e) high vertical heterogeneity; and (f) minimum stand ages older than 200 years. Old-growth forests showed a distinctive structural variability and floristic diversity influenced both by stand age and disturbance history of the stands. Structural variability was also related to environmental differences among sites (e.g. air temperature, distance to coastline, soil types). Old-growth forest features described here can offer a baseline for managers interested in maintaining and restoring old-growth forest structure in southern temperate rain forests.     

Canopy gaps and regeneration in old-growth Oriental beech (Fagus orientalis Lipsky) stands, northern Iran

Virgin beech Fagus orientalis forests in northern Iran provide a unique opportunity to study the disturbance regimes of forest ecosystems without human influence. The aim of this research was to describe characteristics of natural canopy gaps and gap area fraction as an environmental influence on the success of beech seedling establishment in mature beech stands. All canopy gaps and related forest parameters were measured within three 25 ha areas within the Gorazbon compartment of the University of Tehran’s Kheyrud Experimental Forest. An average of 3 gaps/ha occurred in the forest and gap sizes ranged from 19 to 1250 m² in size. The most frequent (58%) canopy gaps were <200 m². In total, canopy gaps covered 9.3% of the forest area. Gaps <400 m² in size were irregular in shape, but larger gaps did not differ significantly in shape from a circle. Most gaps (41%) were formed by a single tree-fall event and beech made up 63% of gap makers and 93% of gap fillers. Frequency and diversity of tree seedlings were not significantly correlated with gap size. The minimum gap size that contained at least one beech gap-filling sapling (<1.3 m tall) was 23.7 m². The median gap size containing at least one beech gap-filling sapling was 206 m² and the maximum size was 1808 m². The management implications from our study suggest that the creation of small and medium sized gaps in mixed beech forest should mimic natural disturbance regimes and provide suitable conditions for successful beech regeneration.     

Long-term spatial dynamics of Acer saccharum during a population explosion in an old-growth remnant forest in Illinois

Species richness and evenness have greatly declined in oak–hickory forests in the central hardwood region in the U.S.A. in the past 100 years due to the rapid population growth of Acer saccharum. This study used a 50-year record of spatial dynamics to examine how demographic processes, particularly recruitment, may have contributed to this increase in an old-growth forest remnant, Brownfield Woods, Urbana, Illinois, U.S.A. The impact of canopy disturbance, including the outbreak of Dutch elm disease, on this increase was also evaluated. Historical maps of trees (≥7.6 cm DBH) from 1951, 1988, and 2001 in a 180 m × 280 m area were used to develop a series of univariate Ripley's L(d) functions to study changes in spatial patterns of three size classes of A. saccharum over time. Bivariate Ripley's L(d) functions were also utilized to evaluate spatial associations between recruitment and canopy disturbance. Our results indicated that A. saccharum was aggregated at most spatial scales up to 80 m during 1951–2001. Such aggregation arose mainly from small individuals. Furthermore, newly recruited individuals were aggregated at multiple spatial scales, and were significantly associated with canopy disturbance in general, as well as gaps created by Ulmus trees killed by Dutch elm disease. The aggregation of the 1951 initial group of small individuals changed via mortality to a random distribution over time. The results indicate that tree deaths caused by disturbances of different scales and types were the main cause of increased recruitment of A. saccharum in Brownfield Woods. The occurrence of Dutch elm disease further accelerated its population increase. This study demonstrated a direct spatial link between recruitment of A. saccharum and disturbance, and provided a long-term case study of a population explosion.     

Spatial patterns in different forest development stages of an intact old-growth Oriental beech forest in the Caspian region of Iran

Spatial patterns of trees are important structural characteristics that can provide insights into forest dynamics and may be related to the development stages of forests. The spatial patterns of three development stages (i.e., initial, optimal, and decay) of an intact old-growth beech (Fagus orientalis Lipsky) forest in the Caspian region of Iran were quantified within one-hectare permanent plots. All trees with a diameter at breast height of more than 7.5?cm were measured, stem-mapped, and then assigned to one of four diameter size classes (small, medium, large, and extra-large timbers). Spatial patterns of all trees and spatial associations among tree size classes were analyzed using Ripley’s K-function, and the spatial dependence of tree diameters was analyzed using variograms. Results showed that trees in the small size class exhibited an aggregated distribution in every development stage, which matched the overall spatial pattern of all trees in each stage. However, the degree of aggregation of all trees as well as association patterns among the size classes differed among the three development stages. Further, the average spatial dependence of tree diameters was 24, 14, and 19?m in the initial, optimal, and decay stages, respectively. Differences in spatial patterns among the development stages in this beech old-growth forest are consistent with the gap-dynamics paradigm and likely reflect different canopy disturbance events coupled with associated regeneration, release, and competition processes (e.g., shade-tolerance characteristics, seed dispersal limitation, and intraspecific competition).     

Alternative silvicultural practices with variable retention improve bird conservation in managed South Patagonian forests

Alternative silvicultural approaches to timber management, such as regeneration treatments with different degrees of stand retention, may mitigate negative effects of clear-cutting or shelterwood cuts in forested ecosystems, including changes in old-growth forest bird communities. The aims of this work were: (a) to compare bird species richness and densities among different silvicultural designs with variable retention (dispersed and/or aggregated) and unmanaged primary forests, and (b) to assess temporal changes at community and species levels before and after treatments. A baseline avian survey was conducted prior to harvesting to evaluate canopy gap presence and forest stand site quality influences. Subsequent to harvesting, data on bird species richness and density were collected by point-count sampling during the summer season for 5 consecutive years (4 treatments × 5 years × 6 sampling points × 5 counts). Bird species richness and density (15 species and 9.2 individuals ha⁻¹) did not change significantly with forest site quality of the stands and canopy gap presence in unmanaged forests. However, both variables were significantly modified in managed forests, increasing over time to 18 species and reaching to 39 individuals ha⁻¹. Inside the aggregated retention, bird communities were more similar to unmanaged primary forests than those observed within the dispersed retention or in clear-cuts. Opting for a regeneration method with dispersed and aggregated retention has great potential for managing birds in Nothofagus pumilio forests. This method retained enough vegetation structure in a stand to permit the establishment of early successional birds (at least in dispersed retention), and to maintain the bird species of old-growth forests which could persisted in the retention aggregates.     

Alternative silvicultural practices with variable retention to improve understory plant diversity conservation in southern Patagonian forests

Understory plants could can act as indicators of temperate forest sustainability, health and conservation status due to their importance in ecosystem function. Harvesting impacts on understory plant diversity depends on their intensity. Variable retention has been proposed to mitigate the harmful effects of timber harvesting, but its effectiveness remains unknown in southern Patagonian Nothofagus pumilio forests. The objectives of this study were to: (i) define a baseline of understory plant diversity in old-growth forests along a site quality gradient and under canopy gaps; (ii) evaluate stands with three different variable retention treatments compared to old-growth forests; and (iii) assess temporal changes during 4 years after harvesting (YAH). A 61 ha N. pumilio forest was selected. Understory plant (Dicotyledonae, Monocotyledonae and Pteridophyta) richness, cover (including woody debris and bare forest floor) and aboveground dry biomass were characterized in summer for 5 years. Before harvesting, baseline samples were conducted along a site quality gradient and outside/inside canopy gaps. Analyzed treatments include a control of old-growth forest (OGF) and three different harvesting treatments with variable retention: (i) dispersed retention (DR) of 30 m² ha⁻¹ (20-30% retention); (ii) aggregated retention (AR) with one aggregate per hectare and clear-cuts (28% retention); and (iii) combined dispersed and aggregated retention (DAR) with one aggregate per hectare and dispersed retention of 10-15 m² ha⁻¹ (40-50% retention). Data analyses included parametric and permutational ANOVAs, multivariate classification and ordinations.Before harvesting, 31 plant species were found, where richness, cover and biomass were directly related to site quality. The presence of canopy gaps did not have a significant impact on the measured variables. After harvesting, 20 new species appeared from adjacent associated environments (two from N. antarctica forests and 18 from grasslands and peatlands). At the stand level, understory values were higher in AR > DR > DAR > OGF. Most (81-95%) plant richness at baseline conditions was conserved in all treatments, where inside the aggregates understory remained similar to OGF. Combination of aggregated and dispersed retention (DAR) better limited exotic species introduction and protected sensitive species, improving conservation in harvested stands. Changes in understory variables were observed after the first YAH in all treatments; greater changes were observed in the harvested areas than in aggregates. Changes stabilized at the fourth YAH. As a conclusion, the location of retention aggregates should be selected to preserve species understory diversity of more speciose and diverse habitats or particularly uncommon stands. Implementation of different kinds (patterns and levels) of retention for improvement of biodiversity conservation in harvested forests should be included in timber and forest management planning.     

Understory vegetation in old-growth and second-growth Tsuga canadensis forests in western Massachusetts

We compared the understory communities (herbs, shrubs, and tree seedlings and saplings) of old-growth and second-growth eastern hemlock forests (Tsuga canadensis) in western Massachusetts, USA. Second-growth hemlock forests originated following clear-cut logging in the late 1800s and were 108–136 years old at the time of sampling. Old-growth hemlock forests contained total ground cover of herbaceous and shrub species that was approximately 4 times greater than in second-growth forests (4.02 ± 0.41%/m² versus 1.06 ± 0.47%/m²) and supported greater overall species richness and diversity. In addition, seedling and sapling densities were greater in old-growth stands compared to second-growth stands and the composition of these layers was positively correlated with overstory species composition (Mantel tests, r > 0.26, P < 0.05) highlighting the strong positive neighborhood effects in these systems. Ordination of study site understory species composition identified a strong gradient in community composition from second-growth to old-growth stands. Vector overlays of environmental and forest structural variables indicated that these gradients were related to differences in overstory tree density, nitrogen availability, and coarse woody debris characteristics among hemlock stands. These relationships suggest that differences in resource availability (e.g., light, moisture, and nutrients) and microhabitat heterogeneity between old-growth and second-growth stands were likely driving these compositional patterns. Interestingly, several common forest understory plants, including Aralia nudicaulis, Dryopteris intermedia, and Viburnum alnifolium, were significant indicator species for old-growth hemlock stands, highlighting the lasting legacy of past land use on the reestablishment and growth of these common species within second-growth areas. The return of old-growth understory conditions to these second-growth areas will largely be dependent on disturbance and self-thinning mediated changes in overstory structure, resource availability, and microhabitat heterogeneity.     

Diversity and spatio-temporal dynamics of dead wood in a temperate near-natural beech forest (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>)

The diversity, spatial patterns and temporal dynamics of dead wood were examined within the near-natural beech forests (Fagus sylvatica) of Serrahn (North-eastern Germany). Data were collected in an 8 ha sample plot and in two permanent plots (0.36 and 0.25 ha) that had been established at the end of the 1960s. The mean volume of dead wood was 94 m³ ha⁻¹, amounting to 14% of the total volume of all trees. The dead wood displayed a large variation in dead wood type, tree size and decay class. Standing dead wood accounted for about one-third of the total dead wood volume. The densities of standing dead trees were about 10% of the densities of the living trees over a wide range of diameters. The overall spatial distribution of dead trees exhibited a random pattern. Among the different dead wood types, standing entire dead trees and uprooted trees deviated from this pattern by displaying a significantly aggregated pattern. In the permanent plots a high mortality of overstorey trees was observed (1.3% year⁻¹) and the average amount of dead wood increased greatly from 2.9 to 111.6 m³ ha⁻¹ over the 35-year observation period. The near-natural beech forests of Serrahn have experienced a long period of low human interference. Nevertheless, our results suggest that the structure and dynamics of dead wood are strongly affected by the last major disturbance events that took place at the end of the Middle Ages. Information about the forest history is therefore a basic requirement when interpreting the results obtained in near-natural forests.     

Carbon storage in old-growth and second growth fire-dependent western larch (Larix occidentalis Nutt.) forests of the Inland Northwest,USA

There is limited understanding of the carbon (C) storage capacity and overall ecological structure of old-growth forests of western Montana, leaving little ability to evaluate the role of old-growth forests in regional C cycles and ecosystem level C storage capacity. To investigate the difference in C storage between equivalent stands of contrasting age classes and management histories, we surveyed paired old-growth and second growth western larch (Larix occidentalis Nutt)–Douglas-fir (Pseudostuga menziesii var. glauca) stands in northwestern Montana. The specific objectives of this study were to: (1) estimate ecosystem C of old-growth and second growth western larch stands; (2) compare C storage of paired old-growth–second growth stands; and (3) assess differences in ecosystem function and structure between the two age classes, specifically measuring C associated with mineral soil, forest floor, coarse woody debris (CWD), understory, and overstory, as well as overall structure of vegetation. Stands were surveyed using a modified USFS FIA protocol, focusing on ecological components related to soil, forest floor, and overstory C. All downed wood, forest floor, and soil samples were then analyzed for total C and total nitrogen (N). Total ecosystem C in the old-growth forests was significantly greater than that in second growth forests, storing over 3 times the C. Average total mineral soil C was not significantly different in second growth stands compared to old-growth stands; however, total C of the forest floor was significantly greater in old-growth (23.8 Mg ha⁻¹) compared to second growth stands (4.9 Mg ha⁻¹). Overstory and coarse root biomass held the greatest differences in ecosystem C between the two stand types (old-growth, second growth), with nearly 7 times more C in old-growth trees than trees found on second growth stands (144.2 Mg ha⁻¹ vs. 23.8 Mg ha⁻¹). Total CWD on old-growth stands accounted for almost 19 times more C than CWD found in second growth stands. Soil bulk density was also significantly higher on second growth stands some 30+ years after harvest, demonstrating long-term impacts of harvest on soil. Results suggest ecological components specific to old-growth western larch forests, such as coarse root biomass, large amounts of CWD, and a thick forest floor layer are important contributors to long-term C storage within these ecosystems. This, combined with functional implications of contrasts in C distribution and dynamics, suggest that old-growth western larch/Douglas-fir forests are both functionally and structurally distinctive from their second growth counterparts.     

Topographic and compositional influences on disturbance patterns in a northern Maine old-growth landscape

Disturbance patterns are strongly coupled with forest composition and structure, and patterns change through time in response to shifts in climate, anthropogenic impacts and other factors. Knowledge of the natural disturbance patterns for establishing baseline conditions for a forest type or ecosystem facilitates change detection for other elements of the biophysical system important to management and conservation. Dendrochronological reconstructions from old-growth forest remnants throughout northeastern North America document average decadal rates of disturbance of 5%–<10% over the last 150–300 years. Relatively frequent, low severity disturbance characterized by small gaps representing canopy openings made by 1–3 trees prevail in these forests dominated by varying mixtures of late-successional tree species. Few studies, though, have explicitly characterized differences related to composition or topographic setting in old-growth landscapes. We addressed this by comparing the temporal and spatial disturbance patterns reconstructed from tree rings at two spatial resolutions (0.5 ha and 200 m²). Sites were selected to assess the influence of topography (slope) and cover type in stands where red spruce (Picea rubens Sarg) and balsam fir (Abies balsamea L. Mill) were key components. Low rates of disturbance (average <10% per decade) and small gap sizes (≤30 m²) prevailed in all stands during the decades from 1850–1980. Episodic pulses of disturbance, of nearly moderate intensity in some stands, opened ca. 20–30% of the canopy area and were associated with wind events and/or insect outbreaks that differentially affected stands. We found no significant difference in the average temporal rates of disturbance related to cover type or topography in 0.5-ha plots. However, the influence of these factors was evident in comparisons of gap areas estimated for 200-m² plot sections. At this resolution, the largest canopy openings (≥100 m²) occurred most frequently in slope sites, enabling pulses of canopy accession for Betula alleghaniensis (Britton). Whereas the smallest canopy openings (≤30 m²) dominated softwood stands, favoring red spruce, balsam fir and other shade-tolerant species throughout the forest. The variable effects of common disturbance agents, regardless of topographic position and/or cover types, points to the important role of biological legacies determining stand structure and composition on subsequent disturbance events and long-term patterns.     

Derivation of a spatially explicit 86-year retrospective carbon budget for a landscape undergoing conversion from old-growth to managed forests on Vancouver Island,BC

To understand the influence of disturbance, age–class structure, and land use on landscape-level carbon (C) budgets during conversion of old-growth forests to managed forests, a spatially explicit, retrospective C budget from 1920 through 2005 was developed for the 2500 ha Oyster River area of Fluxnet-Canada's coastal BC Station. We used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), an inventory-based model, to simulate forest C dynamics. A current (circa 1999) forest inventory for the area was compiled, then overlaid with digitized historic disturbance maps, a 1919 timber cruise map, and a series of historic orthophotographs to generate a GIS coverage of forest cover polygons with unique disturbance histories dating back to 1920. We used the combined data from the historic and current inventory and forest change data to first estimate initial ecosystem C stocks and then to simulate forest dynamics and C budgets for the 86-year period. In 1920, old-growth forest dominated the area and the long-term landscape-level net ecosystem C balance (net biome productivity, NBP) was a small sink (NBP 0.2 Mg C ha⁻¹ year⁻¹). From 1930 to 1945 fires, logging, and slash burning resulted in large losses of biomass C, emissions of C to the atmosphere, and transfers of C from biomass to detritus and wood products (NBP ranged from −3 to −56 Mg C ha⁻¹ year⁻¹). Live biomass C stocks slowly recovered following this period of high disturbance but the area remained a C source until the mid 1950s. From 1960 to 1987 disturbance was minimal and the area was a C sink (NBP ranged from 3 to 6 Mg C ha⁻¹ year⁻¹). As harvest of second-growth forest began in late 1980s, disturbances again dominated the area's C budget, partially offset by ongoing C uptake by biomass in recovering young forests such that the C balance varied from positive to negative depending upon the area disturbed that year (NBP from 6 to −15 Mg C ha⁻¹ year⁻¹). Despite their high productivity, the area's forests are not likely to attain C densities of the landscape prior to industrial logging because the stands will not reach pre-logging ages. Additional work is underway to examine the relative role historic climate variability has had on the landscape-level C budget.     

Characterizing stand-replacing disturbance in western Alberta grizzly bear habitat, using a satellite-derived high temporal and spatial resolution change sequence

Timely and accurate mapping of anthropogenic and natural disturbance patterns can be used to better understand the nature of wildlife habitats, distributions and movements. One common approach to map forest disturbance is by using high spatial resolution satellite imagery, such as Landsat 5 Thematic Mapper (TM) or Landsat 7 Enhanced Thematic Mapper plus (ETM+) imagery acquired at a 30 m spatial resolution. However, the low revisit times of these sensors acts to limit the capability to accurately determine dates for a sequence of disturbance events, especially in regions where cloud contamination is a frequent occurrence. As wildlife habitat use can vary significantly seasonally, annual patterns of disturbance are often insufficient in assessing relationships between disturbance and foraging behaviour or movement patterns.The Spatial Temporal Adaptive Algorithm for mapping Reflectance Change (STAARCH) allows the generation of high-spatial (30 m) and -temporal (weekly or bi-weekly) resolution disturbance sequences using fusion of Landsat TM or ETM+ and Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. The STAARCH algorithm is applied here to generate a disturbance sequence representing stand-replacing events (disturbances over 1 ha in area) for the period 2001-2008, over almost 6 million ha of grizzly bear habitat along the eastern slopes of the Rocky Mountains in Alberta. The STAARCH algorithm incorporates pairs of Landsat images to detect the spatial extent of disturbances; information from the bi-weekly MODIS composites is used in this study to assign a date of disturbance (DoD) to each detected disturbed area. Dates of estimated disturbances with areas over 5 ha are validated by comparison with a yearly Landsat-based change sequence, with producer's accuracies ranging between 15 and 85% (average overall accuracy 62%, kappa statistic of 0.54) depending on the size of the disturbance event. The spatial and temporal patterns of disturbances within the entire region and in smaller subsets, representative of the size of a grizzly bear annual home range, are then explored. Disturbance levels are shown to increase later in the growing season, with most disturbances occurring in late August and September. Individual events are generally small in area (<10 ha) except in the case of wildfires, with, on average, 0.4% of the total area disturbed each year. The application of STAARCH provides unique high temporal and spatial resolution disturbance information over an extensive area, with significant potential for improving understanding of wildlife habitat use.     

Long-term effects of prescribed fire on mixed conifer forest structure in the Sierra Nevada, California

The capacity of prescribed fire to restore forest conditions is often judged by changes in forest structure within a few years following burning. However, prescribed fire might have longer-term effects on forest structure, potentially changing treatment assessments. We examined annual changes in forest structure in five 1 ha old-growth plots immediately before prescribed fire and up to eight years after fire at Sequoia National Park, California. Fire-induced declines in stem density (67% average decrease at eight years post-fire) were nonlinear, taking up to eight years to reach a presumed asymptote. Declines in live stem biomass were also nonlinear, but smaller in magnitude (32% average decrease at eight years post-fire) as most large trees survived the fires. The preferential survival of large trees following fire resulted in significant shifts in stem diameter distributions. Mortality rates remained significantly above background rates up to six years after the fires. Prescribed fire did not have a large influence on the representation of dominant species. Fire-caused mortality appeared to be spatially random, and therefore did not generally alter heterogeneous tree spatial patterns. Our results suggest that prescribed fire can bring about substantial changes to forest structure in old-growth mixed conifer forests in the Sierra Nevada, but that long-term observations are needed to fully describe some measures of fire effects.     

A novel empirical approach for determining the extension of forest development stages in temperate old-growth forests

In the analysis of old-growth forest dynamics, the continuous process of tree aging and forest structural change is split up into several distinct forest development stages. The criteria for distinguishing the stages vary among the different approaches. In most of them, vertical canopy heterogeneity is only coarsely addressed and horizontal forest structure is quantified at spatial scales far exceeding the size of conventional forest inventory plots. In order to describe and analyze the complex mosaic structure of temperate old-growth forests with objective and quantitative measures in the context of forest inventories, we propose the Development Stage Index I _DS . It employs two easily measured stand structural parameters (stem density and basal area) for quantifying the abundance of trees in three conventionally recognized tree diameter classes (premature ?<?40 cm; mature 40–70 cm; and over-mature?≥?70 cm) in plots of 500 m² size, systematically distributed in the forest. This allows quantifying the spatial extension of the Initial, Optimum and Terminal stages of forest development at plot, stand and landscape levels. Based on thorough stand structural analyses in three virgin beech (Fagus sylvatica) forests in Slovakia, we demonstrate that I _DS is a promising tool for (1) quantifying the proportion of the three stages on different scales, (2) visualizing the complex mixing of stages, and (3) analyzing dynamic changes in old-growth forest structure. We conclude that the Development Stage Index has the potential to improve the empirical foundation of forest dynamics research and to allow this discipline to proceed to more rigorous hypothesis testing.     

Accumulation of dead wood in abandoned beech (Fagus sylvatica L.) forests in northwestern Germany

Currently, there is much debate about what strategy is most suitable for increasing old-growth attributes in forests that have been managed intensively for wood production in the past. Passive restoration, i.e. cessation of forestry interventions, should be considered when the old-growth attributes desired can be restored within a feasible period of time.Our study focuses on standing and lying coarse dead wood (≥20 cm diameter) in beech-dominated forests in northwestern Germany. We analyzed monitoring data of 545 sample plots (sized 500-1000 m²) from 12 strict forest reserves (SFRs). The SFRs had been without forestry intervention for up to 28 years.Both, number of dead objects and volume of dead wood (m³ ha⁻¹) increased significantly with ongoing time since abandonment from forestry interventions. The mean amount doubled from 9 to 18 m³ ha⁻¹ within 10 years. The proportion of standing dead wood was about 40% of the total dead wood pool ≥20 cm diameter.With mixed linear modeling we showed that dead wood increased by a mean net rate of about 1 m³ ha⁻¹ a⁻¹. Therefore, after three decades critical values for restoring the dead wood pool could be reached. We hypothesized that the rate of dead wood input is mainly determined by disturbance driven tree mortality such as oak decline, bark beetle infestations and storms.A comparison with primeval forests or reserves abandoned more than 100 years ago showed that the SFRs studied are at the beginning of a long process of dead wood accumulation.Based on our results, the abandonment of forest activities in harvestable pure and mixed beech stands is an effective strategy for restoring the dead wood pool.     

Spatiotemporal dynamic of European beech (Fagus sylvatica L.) in Slovenia, 1970–2005

Based on data acquired from the spatial information system Silva-SI, the majority of the entire forest area in Slovenia (22,220 forest compartments with a total area of 7446 km², classified into eight forest categories) was analysed for changes in the distribution of European beech (Fagus sylvatica L.) in the period 1975–2005 using a binary logistic regression model in terms of selected site, stand and management variables. Additionally, changes in the abundance of beech in forest stands in which beech was present at the beginning and the end of the analysed period were analysed. Beech expanded its area by more than 1200 ha per year on average, i.e. the annual expansion rate amounted to 0.24%. Among the 18 studied variables, three site, four stand and no management variables were included in the binary logistic regression model of beech expansion. Beech expansion was more pronounced at lower altitudes, on sites with steep topography, and on sites with a higher proportion of beech in potential natural vegetation. The probability of beech expansion reduced by a factor of 0.54 when the distance to the nearest compartment with beech increased by 1 km. Among other stand variables, the proportion of early successional phases and the proportion of silver fir (Abies alba Mill.) and Norway spruce (Picea abies (L.) Karst.) also influenced the expansion of beech. During the observed period the growing stock of beech almost doubled, its proportion in total growing stock increasing from 27% to 32%. Significant differences were found in changes of beech proportion in the total growing stock among different forest categories; a decrease in the beech proportion was registered in alpine coniferous forests and thermophilous deciduous forests, while in other forest categories the proportion of beech increased. The recent development of forest stands and their current structure indicate a further expansion of beech and an increase in the proportion of beech in forest stands.     

Lianas and self-supporting plants during tropical forest succession

Lianas (woody vines) are an important component of tropical forests, with a strong impact on forest dynamics, but their responses during forest succession have received relatively little attention. Here, we present an analysis of the changes in stem density, biomass, and species richness of lianas and self-supporting plants during tropical forest succession. We surveyed lianas ≥0.5 cm diameter at breast height (dbh) and self-supporting plants ≥2.5 cm dbh in 0.1 ha inventory plots in a chronosequence of 30 sites in northeastern Costa Rica, 23 sites on abandoned pastures 10–44 years of age, and seven sites in old-growth forest. Stem density of self-supporting plants showed no predictable chronosequence trend, but liana stem density declined significantly with forest age. Aboveground biomass of self-supporting vegetation increased rapidly during succession, with forests 31–44 years exhibiting higher levels of biomass than old-growth forests. Liana biomass accumulated more slowly, with the highest levels in old-growth sites. Species richness of self-supporting vegetation increased significantly during succession, but species richness of lianas showed no change or a slight decline with forest age, depending on the method of assessment. The differences between tree and liana responses during succession stem from the unique physiology and life history traits of lianas.     

Characteristics of typhoon disturbed gaps in an old-growth tropical montane rainforest in Hainan Island,China

Disturbances that create gaps can shape the structure and function of forests. However, such disturbance regimes in Asian tropical montane rainforests remain largely unquantified. Least studied are typhoon disturbances that are attributable to climate change. We investigated gap characteristics in terms of size, age, and gapmaker to quantify the gap disturbance regimes in an intact old-growth tropical montane rainforest on Hainan Island,China. The intensity of typhoons has increased since 1949,and typhoon winds blow mostly(45.5%) from the northeast corner of Hainan Island, resulting in a higher frequency of gaps in the northeast. A total of 221 gap-makers(trees that fell to create canopy gaps) and 53 gaps were observed in a 3.16 ha old-growth rainforest. Most canopy gaps(85%)were 200 m~2. The average size of canopy gaps was smaller in the rainforest than in other tropical forests, while the average size of expanded gaps was similar to those in other tropical forests. The maximum age of gaps was 23.5 years indicating that gaps had more rapid turnover than other parts of tropical forests. The frequency distribution of gap-makers followed a lognormal distribution with a distinctive peak at three gap-makers, which was different from the inverse J-shaped curve typical of other tropical forests. Gaps were recorded mainly on slopes between 20° and 35° and wood density of gap-makers was between 0.6 and 0.7 g cm~(-3). Our results suggest that small-scale disturbance was the dominant agent of gap formation in this old-growth rainforest that is subject to increasing typhoon disturbances.     

Local variability of stand structural features in beech dominated natural forests of Central Europe: Implications for sampling

Current knowledge of the within-site variability of major stand structural features in beech dominated natural forests is limited. Numerous studies have used just several small plots for characterizations of natural stands, but this may lead to generalizations based on unreliable results. This study shows how major stand structural features vary at the local scale, and how suitable sampling may reflect this variability. Stem position maps of three natural forests in the Czech Republic (Zofin 71 ha, Salajka 19 ha and Zakova hora 17 ha) were used. Each vector stem position map representing all live and dead trees with DBH ≥ 10 cm was intensively analyzed using square sample plots of different sizes (10 × 10 m; 20 × 20 m; 30 × 30 m; 50 × 50 m; 100 × 100 m; 140 × 140 m and 200 × 200 m). Basic statistics (mean, standard deviation, coefficient of variation, min., and max.) were calculated for every plot size and each of six major stand features: density, basal area and volume of living trees, volume of course woody debris, total volume and proportion of course woody debris in total volume.