Stand Structure Characteristics Research Articles

Precipitation and Temperature Influence the Relationship between Stand Structural Characteristics and Aboveground Biomass of Forests—A Meta-Analysis

Forest aboveground biomass (AGB) is not simply affected by a single factor or a few factors, but also by the interaction between them in complex ways across multiple spatial scales. Understanding the joint effect of stand structural characteristics and climate factors on AGB on large scales is critical for accurate forest carbon storage prediction and sustainable management. Despite numerous attempts to clarify the relationships between stand structural characteristics (tree density/TD, diameter at breast height/DBH, basal area/BA), climate factors (mean annual temperature/MAT, mean annual precipitation/MAP), and AGB, they remain contentious on a large scale. Therefore, we explored the relationships between stand structural characteristics, climate factors, and AGB at a biome level by meta-analyzing datasets contained in 40 articles from 25 countries, and then answered the questions of how stand structural characteristics influence AGB at the biome level and whether the relationships are regulated by climate on a large scale. Through using regression analysis and the establishment of a structural equation model, the results showed that the influence of basal area on AGB at the biome level was more substantial than that of tree density and DBH, and the significant relationship between basal area and AGB was relatively stable regardless of biome variation, but the effects of tree density and DBH was non-negligible within the biome. Climatic factors (e.g., temperature and precipitation), should be considered. Our meta-analysis illustrated the complicated interactions between climate factors, stand structural characteristics, and the AGB of forests, highlighting the importance of climate effects on regulating stand structural characteristics and AGB relationships. We suggest that basal area be preferred and considered in forest sustainable management practice to optimize stand structure for increasing carbon storage potential, with close attention to local climate conditions. Overall, our meta-analysis will crucially aid forest management and conservation in the context of global environmental changes, and provide novel insights and a scientific reference to lead to future carbon storage research on large scales.

Ecological and silvicultural assessment of European aspen (Populus tremula L.) stands: The sample of Erciyes Mountain

Türkiye’de yayılış alanı giderek artan saf titrek kavak meşcerelerinin işletme amaçlarının ve silvikültürel uygulamalarının tespiti önem taşımaktadır. Çalışma kapsamında Erciyes dağı çevresinde doğal olarak yayılış gösteren titrek kavak ormanlarının alansal dağılımının, ekolojik karakteristiklerinin, meşcere kuruluş özelliklerinin ve silvikültürel müdahalelerin ortaya koyulması amaçlanmıştır. Çalışma Erciyes ve Develi Orman İşletme Şefliğinde yer alan titrek kavak meşcerelerinde gerçekleştirilmiştir. Her bir meşcere gelişim çağından alınan örnek alanlarda ekolojik özelliklerle birlikte hektardaki birey sayıları, göğüs yüksekliği çap değerleri ve kapalılık dereceleri tespit edilmiştir. Ayrıca 2019 yılında ilk aralama müdahalesi yapılan ve bakım müdahalesi yapılmayan aynı yaş ve bonitetteki saf meşcerelerden örnek alanlar alınmış ve titrek kavak meşcerelerinin aktüel durumu yanında iki yıllık aralama müdahalelerinin etkisi incelenmiştir. Çalışma sonucunda Kayseri Erciyes dağının kuzey, güney ve batı bakılardaki eteklerinde toplam 3674.1 ha titrek kavak ormanının yer aldığı belirlenmiştir. Bu ormanlar genellikle saf meşcereler halinde ve 1750-2250 metrelerde yayılış göstermektedir. Meşcerelerin çoğunlukla %21-40 ve %41-60 eğim grubunda yer aldığı tespit edilmiştir. Meşcere gelişme çağlarına göre gençlik çağında hektardaki birey sayısının 100000-200000 adet arasında (3-4 yaşında, 0.5-1.5 m boy ve 2-8 mm çap) değiştiği belirlenmiştir. Sıklık çağında ortalama çapın 7.42 cm (2.8 cm-12.3cm) ve hektardaki birey sayısının 7500 adet olduğu ortaya koyulmuştur. 2019 yılı ilk aralama müdahaleleri sonrasında 2021 yılında yapılan ölçümlere göre ortalama boy artımının Erciyes için 1.0 m/yıl, Develi için 1.35 m/yıl olduğu, göğüs yüksekliği çap artımının ise Erciyes için 1.08 cm/yıl, Develi için 1.79 cm/yıl olduğu belirlenmiştir. Titrek kavak ormanlarının gelişim çağlarına bağlı olarak gerekli silvikültürel müdahalelere konu edilmesi ve böylelikle sürdürülebilirliğin sağlanması gerekmektedir.

Stand Structural Characteristics Derived from Combined TLS and Landsat Data Support Predictions of Mushroom Yields in Mediterranean Forest

Forest fungi provide recreational and economic services, as well as ecosystem biodiversity. Wild mushroom yields are difficult to estimate; climatic conditions are known to trigger temporally localised yields, and forest structure also affects productivity. In this work, we analyse the capacity of remotely sensed variables to estimate wild mushroom biomass production in Mediterranean Pinus pinaster forests in Soria (Spain) using generalised additive mixed models (GAMMs). In addition to climate variables, multitemporal NDVI derived from Landsat data, as well as structural variables measured with mobile Terrestrial Laser Scanner (TLS), are considered. Models are built for all mushroom species as a single pool and for Lactarius deliciosus individually. Our results show that, in addition to autumn precipitation, the interaction of multitemporal NDVI and vegetation biomass are most explanatory of mushroom productivity in the models. When analysing the productivity models of Lactarius deliciosus, in addition to the interaction between canopy cover and autumn minimum temperature, basal area (BA) becomes relevant, indicating an optimal BA range for the development of this species. These findings contribute to the improvement of knowledge about wild mushroom productivity, helping to meet Goal 15 of the 2030 UN Agenda.

Estimating height-diameter relations for structure groups in the natural forests of Northeastern China

Tree height-diameter (H-D) models are essential for estimating tree volume and forest production. The development of such models can be especially challenging in multi-species natural forests. We present new generalized mixed-effects models based on a set of 456 sample plots and 77,908 individual tree measurements. Tree species were assigned to one of four structure groups according to their life forms, regeneration modes and stand structure characteristics: (1) Understory tree species with an L-shaped D distribution (UL); (2) Sub-canopy tree species with an L-shaped D distribution (SL); (3) Sub-canopy tree species with a bell-shaped D distribution (SB); and (4) Canopy tree species with a bell-shaped D distribution (CB). A distance-dependent competition index (DCI) was included in the base model of the structure groups, and a mixed-effects model for each group with tree species as random-effect. The four models represent unique allometric relationships for the four structure groups. Model accuracy was improved for all groups after adding DCI. Two sets of mixed-effects H-D models (with or without DCI) are presented to improve the estimates of productivity and carbon stock in the temperate natural forests of Northeastern China. The general approach adopted in this study may serve as an example for similar studies in other multi-species and multi-layered forest stands.

Forest stand structure and cone crop affect winter habitat use by Eurasian red squirrel (Sciurus vulgaris)

Food resources are one of the important components of high quality habitat. One way to better understand the behavioral decisions made by animals to select foraging patches is focusing on the important forest stand structure characteristics. In this study we investigate the relationship between red squirrel habitat preferences, forest characteristics, i.e. distance to forest edge, canopy closure, cover of understory and undergrowth, and estimated cone biomass. We explore for the first time a methodology to predict cone biomass based on allometric equations and the extent to which this parameter affects habitat choice by red squirrels. Using tree measurements to predicted cone biomass at the plot level which is located in a given stand provides a usefulness proxy of food resources and it is not time-consuming compare with the traditional annual cone count. We selected sixty 30-by-30 m plots in mature Norway spruce forest stands where we measured percentage understory cover, percentage undergrowth cover, distance to forest edge, number of Norway spruce trees, diameter at breast height and height of each Norway spruce tree, number of other tree species and percentage of canopy closure. Within each plot, we counted all Norway spruce cones stripped by red squirrels. Results showed that both forest characteristics (i.e. distance to forest edge and canopy closure) and estimated cone biomass were significant predictors of red squirrel feeding signs on Norway spruce. Our study revealed the potential usefulness of cone biomass as a parameter to determine cone productivity of Norway spruce stands. The effects of food abundance and forest stand structure characteristics are crucial for habitat selection by red squirrels. Estimation of cone biomass based on the tree measurement can be useful for predicting potential foraging habitats for red squirrels regardless of the seed year and can be simple to use for conservation practice in order to locate potential sites for protection of this species.

Global transpiration data from sap flow measurements: the SAPFLUXNET database

Abstract. Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (https://doi.org/10.5281/zenodo.3971689; Poyatos et al., 2020a). The “sapfluxnetr” R package – designed to access, visualize, and process SAPFLUXNET data – is available from CRAN.

Beetlemania: Is the bark worse than the bite? Rocky Mountain subalpine forests recover differently after spruce beetle outbreaks and wildfires

Due to the shifting global climate, the frequency and severity of disturbances are increasing, inevitably causing an increase in disturbances overlapping in time and space. Bark beetle epidemics and wildfires have historically shaped the disturbance regimes of Western North American forests. Their interactive effects on stand dynamics and recovery are inadequately studied in Picea engelmannii (Engelmann spruce)-Abies lasiocarpa (subalpine fir) dominant forests; understanding these interactions is imperative to the management and health of forested ecosystems. This study focuses on the effects of epidemic Dendroctonus rufipennis (spruce beetle) outbreaks, high-severity fires, and the subsequent species and structural diversity of subalpine forest regeneration and structure in Northern Colorado and Southern Wyoming. We compared tree seedling densities and species composition, surface fuel loading, and stand structure characteristics across 80 sites that experienced either high tree mortality from epidemic spruce beetle outbreaks (>50% affected basal area), high-severity wildfire, post-outbreak high-severity wildfire (1–3 years post-outbreak), or no disturbance (control). The beetle outbreak sites span multiple years post-outbreak from 1996 to 2017, ultimately comprising a chronosequence of beetle-affected stands. Analyses indicate a significant increase in fuel loading over time-since-outbreak, as aerial fuels are transferred to the forest floor following high tree mortality. Tree seedling densities among outbreak and control sites differ significantly from burned areas, indicating that wildfires override the effects of repeated disturbances on regeneration. There was consistent Engelmann spruce seedling survival following beetle outbreaks, providing evidence for stable forest recovery following a single disturbance. However, fire was a dominate force in determining post-disturbance species composition, indicating continued prevalence of high severity fire may prove detrimental for the persistence of spruce-fir species, while promoting shifts toward more drought and fire tolerant tree species (e.g., Pinus contorta). It is critical to understand post-disturbance fuel dynamics and stand recovery to identify hazards for subsequent fire suppression, implement treatments to enhance forest resilience, and to understand the potential consequences of climate-induced shifts in disturbance regimes on forest health.

How does the stand structure of treeline-forming species shape the treeline ecotone in different regions of the Nepal Himalayas?

Stand structure dynamics are considered as major happenings in any forest as a response to environmental changes. However, this important topic is underrepresented in the treeline studies in the Nepal Himalayas. We aimed to investigate site- as well as species-specific changes in morphometric features (basal diameter, crown cover, density, and height) along the elevational gradient across treeline ecotones in response to recent environmental changes. The stand structure characteristics of Abies spectabilis, Pinus wallichiana, and Betula utilis across the treeline ecotone of three study sites in Eastern (Barun), Central (Manang), and Western (Dhorpatan) Nepal were analyzed to elucidate structural heterogeneities. Altogether, eight transects (20 m × (60–250 m)) across the treeline ecotone were established. Trees of all life forms, trees (> 2 m), saplings (0.5–2 m), and seedlings (< 0.5 m), within each transect were enumerated and sampled for the morphometric features and age. Site-specific and species-specific stand structure dynamics were found. The rate of basal area increment was higher in Barun, but the Manang treeline, despite profound regeneration in recent years, had a low annual basal area increment. Moreover, the altitudinal distribution of age and morphometry were not consistent among those ecotones. Furthermore, intra-specific competition was not significant. The site-specific stand structure dynamics explain why treelines do not respond uniformly to increasing temperature. It invokes, in further studies, the incorporation of the tree’s morphometric adaptation traits, phenotypic plasticity, and interactions between species genotype and the environment.

An Application of Non-Parametric Method and Simple Linear Regression in Rainfall Partitioning in Tropical Lowland Forest of Sepilok Forest Reserve, Sabah

This study was conducted in the alluvial forest and heath forest in the lowland tropical forest of Sepilok Forest Reserve, Sabah, Malaysia. The main objective was to assess how forest structure regulates rainfall partitioning in both forests. Field monitoring involved a series of forest inventory work to determine the forest stand characteristics. Mann Whitney U test was performed to compare physical characteristics between the two forests. Meanwhile rainfall partitioning was quantified by measuring the throughfall (Tf) for a period of 12 months in ten (15 x 15 m) Tf plots and a simple linear regression was conducted to obtain a regression model to estimate Tf. In terms of stand structure characteristics, data in the alluvial forest indicates wider variation. Percentage of Tf as of gross rainfall (Pg) is higher in the heath forest than in alluvial forest with the value of 89.5 % and 76.8 %, respectively. Representative trees were selected for stemflow (Sf) estimation at each forest type. The estimated Sf is 0.2 % in alluvial forest and 0.5 % in heath forest. In this study, tree diameter at breast height (Dbh) and height as well as aboveground biomass were identified to have some influence in Tf and Sf production. Keywords: rainfall partitioning; gross rainfall; throughfall; stemflow; Mann Whitney U; simple linear regression

Stand Structural Characteristics Are the Most Practical Biodiversity Indicators for Forest Management Planning in Europe

Including biodiversity assessments in forest management planning is becoming increasingly important due to the importance of biodiversity for forest ecosystem resilience provision and sustainable functioning. Here we investigated the potential to include biodiversity indicators into forest management planning in Europe. In particular, we aimed to (i) identify biodiversity indicators and data collection methods for biodiversity assessments at the stand and landscape levels, and (ii) evaluate the practicality of those indicators for forest management planning. We performed a literature review in which we screened 188 research studies published between 1990 and 2020. We selected 94 studies that fulfilled the inclusion criteria and examined in more detail. We considered three aspects of biodiversity: structure, composition, and function, and four forest management categories: unmanaged, managed, plantation, and silvopastoral. We used three criteria to evaluate the practicality of forest biodiversity indicators: cost-effectiveness, ease of application, and time-effectiveness. We identified differences in the practicality of biodiversity indicators for their incorporation into management plans. Stand-level indicators are more practical than landscape-level indicators. Moreover, structural biodiversity indicators (e.g., large trees, canopy openness, and old forest stands) are more useful in management plans than compositional indicators, as these are easily observable by non-professionals and can be obtained by forest inventories. Compositional indicators such are vascular plants, fungi, bryophyte, lichens, and invertebrate species are hard to identify by non-professionals and thus are impractical. Functional indicators (e.g., nutrient cycling) are not sufficiently addressed in the literature. Using recently updated existing databases (e.g., national forest inventories and bird atlases) is very time and cost-efficient. Remote sensing and other technology (e.g., smartphone applications) are promising for efficient data collection in the future. However, more research is needed to make these tools more accurate and applicable to a variety of ecological conditions and scales. Until then, forest stand structural variables derived from inventories can help improve management plans to prepare European forests towards an uncertain future.

Effect of spatial scale and harvest on heterogeneity of forest floor CO2 efflux in a sessile oak forest

Soil respiration is the second largest flux of carbon between terrestrial ecosystems and the atmosphere and it is substantially sensitive to climate change. Monitoring CO2 efflux and its upscaling from field measurements to the ecosystem level is a complex task, due to the high spatial and temporal variability of the fluxes. Human intervention, e.g. through forest harvest, may change both CO2 efflux and its spatial heterogeneity. The objective of our study was to quantify spatial heterogeneity of soil CO2 efflux within and among plots distributed within a topographically variable sessile oak forest stand before and after harvesting. Forest floor CO2 efflux, soil temperature and soil water content were measured monthly in a sessile oak forest during two growing seasons: one before and one after harvesting. Stand structure characteristics (gap fraction, leaf area index, tree number and size) and the amount of understory also were determined. Relationships between individual variables and spatial heterogeneity were analyzed. The small-scale spatial heterogeneity (expresses as the coefficient of variation) of forest floor CO2 efflux and soil water content (SWC) in the undisturbed forest was low, at maximum 0.22 and 0.13, respectively. Studied variables had no effect on spatial heterogeneity of forest floor CO2 efflux except for the amount of understorey vegetation which positively correlated with forest floor CO2 efflux. Although the studied forest was situated in topographically variable terrain, we observed that inter-plot heterogeneity of forest floor CO2 efflux was lower than that within plots. Stand harvest increased the intra-plot heterogeneity of forest floor CO2 efflux but did not affect the inter-plot heterogeneity. This leads to the conclusion that the number of positions within an individual plot should increase after harvest but the number of plots may remain unchanged to determine adequately ecosystem forest floor CO2 efflux.

Effects of Thinning on the Spatial Structure of Larix principis-rupprechtii Plantation

Structure-based forest management is a scientific and easy-to-operate method for sustainable forest management. We analyzed the stand spatial structure of Larix principis-rupprechtii plantation under five reserve densities. The results indicated that with the decrease of densities after thinning, the average mingling degree and uniform angle index had an increasing tendency, but the amplitude was small. Most of the trees were in zero mix, and a few of them were in moderate, strong, and relatively strong mix; the horizontal distribution patterns were uniform or near-uniform random. The distribution of neighborhood comparison and opening degree changed with a fluctuant pattern, but thinning decreased the competitive intensities to some extent. A composite structure index (Ci) was established, based on the relative importance of the above four indicators, to evaluate the overall effect of thinning on stand structure characteristics. The findings showed that Ci increased with the increase of thinning intensity, that is, the stand spatial structure became more complex. This indicated that Ci may be a simple and rapid indicator to evaluate the overall effect of thinning on stand spatial structure within densities after thinning.

Human and natural controls of the variation in aboveground tree biomass in African dry tropical forests.

Understanding the anthropogenic and natural controls that affect the patterns, distribution, and dynamics of terrestrial carbon is crucial to meeting climate change mitigation objectives. We assessed the human and natural controls over aboveground tree biomass density in African dry tropical forests, using Zambia's first nationwide forest inventory. We identified predictors that best explain the variation in biomass density, contrasted anthropogenic and natural sites at different spatial scales, and compared sites with different stand structure characteristics and species composition. In addition, we evaluated the effects of different management and conservation practices on biomass density. Variation in biomass density was mostly determined by biotic processes, linked with both species richness and dominance (evenness), and to a lesser extent, by land use, environmental controls, and spatial structure. Biomass density was negatively associated with tree species evenness and positively associated with species richness for both natural and human-modified sites. Human influence variables (including distance to roads, distance to town, fire occurrence, and the population on site) did not explain substantial variation in biomass density in comparison to biodiversity variables. The relationship of human activities to biomass density in managed sites appears to be mediated by effects on species diversity and stand structure characteristics, with lower values in human-modified sites for all metrics tested. Small contrasts in carbon density between human-modified and natural forest sites signal the potential to maintain carbon in the landscape inside but also outside forestlands in this region. Biodiversity is positively related to biomass density in both human and natural sites, demonstrating potential synergies between biodiversity conservation and climate change mitigation. This is the first evidence of positive outcomes of protected areas and participatory forest management on carbon storage at national scale in Zambia. This research shows that understanding controls over biomass density can provide policy relevant inputs for carbon management and on ecological processes affecting carbon storage.

Fine-scale spruce mortality dynamics driven by bark beetle disturbance in Babia Góra National Park, Poland

Bark beetle outbreaks have had major impacts on Norway spruce forests in Europe. The large majority of these forests are located in areas under forest management; thus, few studies have investigated outbreak-driven spruce mortality patterns unaffected by humans. Our study examined spruce mortality resultant from a beetle outbreak in a high-elevation, unmanaged forest over a 17-year span. We analyzed three tree-level survivorship and DBH datasets collected during pre-, mid-, and post-outbreak conditions to evaluate long-term mortality dynamics. We measured changes in mortality severity, topographic and stand structure characteristics, and stand complexity using ANOVAs, and we assessed five topographic and stand structure mortality predictors by employing boosted regression trees. Our results showed that though spruce mortality increased significantly over time, such increases were disproportionate with spatial synchrony. Moreover, the outbreak did not significantly alter the living stand structure and had little effect on stand complexity, exhibiting the effects of an outbreak that spread throughout the forest without causing major stand-level damage. Larger trees at higher elevations on south-facing slopes were targeted most frequently, particularly during the later stages of the outbreak. Aspect, elevation, and slope were the best predictors of mortality, demonstrating moderate forecasting ability. We showed that bark beetle outbreaks can operate on patch-scale gradients, affecting microhabitat conditions, without resulting in sweeping, stand-altering mortality. Small-scale outbreaks may increase forest resilience against more severe outbreaks in the future by creating canopy gaps that facilitate regeneration, which leads to more complex age and size structures within the stand.

Assessing stand structure in successional stages of dark coniferous forests in western Sichuan, China

Subalpine dark coniferous forests in the western Sichuan Province of China play an important role in the hydrological processes in the upper reaches of the Yangtze River. Second-growth forests, with different stand successional stages, have developed as a result of logging over the past 50 years. Forest cover and stand structure changed greatly with concomitant degradation of forest ecosystem functions. To understand how the stand structures of the second-growth forests change during the stand succession process, we analyzed stand structure characteristics and an old-growth state index of the bamboo and moss-forest types. We found that stand structure at the young successional stage featured one-third of the structure characteristics of the old-growth dark coniferous forests, while the structure of the medium-aged stage had reached half the structure of the old-growth state. The two forest types were similar in the rate of development at the young successional stage but differed at the medium-aged stage; the moss-forest type had more advanced development than the bamboo-forest type at the medium-aged successional stage.

Tree and stand-level patterns and predictors of Norway spruce mortality caused by bark beetle infestation in the Tatra Mountains

This study investigates temporal shifts in Norway spruce (Picea abies) mortality, stand structure characteristics, and stand complexity facilitated by a bark beetle (Ips typographus) outbreak that affected an unmanaged subalpine forest region in Tatra National Park, Poland in the late 2000s. Changes in survivorship and stand structure characteristics (diameter (DBH), basal area, height, age, and crown length ratio) of nearly 2500 spatially-referenced trees located in 64 long-term survey plots were compared over four time periods that spanned the duration of the outbreak disturbance event. Stand structure characteristics, topographic factors (slope, elevation, and aspect), and solar equinox radiation were tested as predictors of mortality for multiple stages in the outbreak using boosted regression tree modeling. Our findings showed that: (1) spatial synchrony was not reflective of mortality severity; (2) mortality rates increased significantly as the outbreak progressed; (3) the stand’s structure was altered significantly by the outbreak (larger trees were killed most frequently); (4) stand structure characteristics were the best predictors of mortality in all stages of the outbreak, though topographic factors and solar equinox radiation also exhibited moderate to strong predictive power in some stages; and (5) stand complexity decreased significantly as the outbreak progressed. This illustrates the inherently complex nature of bark beetle outbreaks on fine spatial scales and suggests that the extent and severity of spruce mortality during an outbreak event is largely dependent on the relative stage of the outbreak and the structure of the stand.

Bark beetles and wildfires: How does forest recovery change with repeated disturbances in mixed conifer forests?

Increased wildfire activity and recent bark beetle outbreaks in the western United States have increased the potential for interactions between disturbance types to influence forest characteristics. However, the effects of interactions between bark beetle outbreaks and subsequent wildfires on forest succession remain poorly understood. We collected data in dry mixed conifer forests across Idaho and western Montana to test whether vegetation responses differ between sites experiencing single and repeated disturbances. We compared tree seedling density and age, surface fuel loading, and stand structure characteristics in stands that experienced either high severity wildfire, large‐scale tree mortality from bark beetles, or stands that experienced high bark beetle mortality followed by severe wildfire within 3–8 years of attack. Tree seedling density was 300–400% higher in gray bark beetle‐affected stands than burned sites, but there was no evidence that a beetle and wildfire interaction affected seedling densities. The age distribution of Douglas‐fir and grand fir seedlings in stands with repeated disturbances differed from those that only experienced wildfire, suggesting that seed availability varies between these stands. Though both bark beetle outbreaks and wildfires resulted in the death of numerous large trees and surface woody fuel loads 100–200% greater than control sites, the creation of large snags and higher fuel loads across the landscape may have ecological benefits. Compounding effects of bark beetle activity and wildfires were not observed in surface fuel loadings or stand densities. Overall, the effects of high severity wildfire drove post‐disturbance fuel complexes and succession whereas the effects ofDendroctonus pseudotsugaeandDendroctonus brevicomisoutbreaks before wildfires resulted in minimal post‐wildfire differences. We conclude that although seedling age structure is responsive to bark beetle and fire interactions, in terms of fuel complexes and tree densities these disturbances are non‐additive and compounding effects on forest trajectory of dry mixed conifer forests of the northern Rockies were not supported.

Biodiversity composition reflects the history of ancient semi-natural woodland and forest habitats—Compilation of an indicator complex for restoration practice

For centuries, Fennoscandian wooded meadows and woodland pastures (Habitats Directive habitat types *6530 and 9070 respectively) covered large areas of Northern Europe. In the Twentieth Century, abandonment-driven encroachment has led to the wooded grasslands changing into what may be considered as old-growth deciduous forests. The present paper examined whether the present stand structure and the composition of three contrasting functional groups (herbaceous layer vascular plants, epiphytic bryophytes, and earthworms) could serve as indicators of the historic origin of the forest patches, i.e. to what extent changes in ecological conditions in overgrown woodlands have shifted towards broad-leaved forests with ancient trees. Indicators were tested for the objective of restoration planning of habitat quality, i.e. whether semi-open woodlands could be restored or if it would be more appropriate to preserve them as broad-leaved forests. The study was carried out by comparing the composition of ancient forest cores, forest edges and overgrown wooded grasslands. The land use history of sample sites was examined from historical topographical maps and aerial photos.The results showed that as long as 60 years after abandonment, parts of the studied forests still retained some light-demanding plant species characteristic of historical wooded grasslands. The composition of earthworm communities was similar in all of the studied historical forest groups. Only some of the stand structure characteristics and epiphytic mosses indicated that there were differences between ancient forest cores and overgrown wooded grasslands. We conclude that the combination of various functional indicators should be used in the evaluation of successional woodlands for habitat restoration.

A Comparison of Growth and Stand Structural Characteristics in Pure- and Mixed-Family Stands of Loblolly Pine

A Comparison of Growth and Stand Structural Characteristics in Pure- and Mixed-Family Stands of Loblolly Pine

Abandonment status and long-term monitoring of strict forest reserves in the Pannonian biogeographical region

The Pannonian region is situated in the Carpathian basin where forests have been used intensively for centuries. The article shows a map and a tabular overview of the forest reserves featured as forests “left for free development” of the region, and presents the most important stand structural characteristics of beech, mesophytic and thermophilous deciduous forests surveyed recently. The sampling points of six sites were selected to provide preliminary descriptive statistics according to the main types and abandonment status groups (recently managed, long abandoned and old-growth or primary stands) of these forests. In old-growth and primary stands the composition (list and mixture ratio of tree species) and stand structure characteristics [gap class distribution, stem density, distribution of relative crown classes and broad diameter at breast height (at 130 cm) classes, density of thick snags, and the amount of lying dead wood] proved to be similar to other European deciduous natural forests, while the abandoned and recently managed stands indicate that these forests are in a transitional stage towards natural ones.