Regeneration Density Research Articles

Ricolinostat induces microtubule acetylation and neurite regeneration in cellular models of diabetic and chemotheraphy-induced neuropathy

Peripheral nerves have unique regenerative capability, but two questions are still unanswered: what are the underlying mechanisms and why do some patients show higher spontaneous nerve fibers regeneration than others. Here we investigated if microtubule posttranslational modifications (PTMs) impact on neuronal regeneration in in vitro models of small fiber neuropathy (SFN) and predict intra-epidermal nerve fibers regeneration density (IENFD) in patients.

Effects of Fire Severity and Woody Debris on Tree Regeneration for Exploratory Well Pads in Jack Pine (Pinus banksiana) Forests

Restoring anthropogenic footprints to pre-disturbance conditions or minimizing their long-term impacts is an important goal in conservation. Many footprints, particularly if left alone, have wide-ranging effects on biodiversity. In Canada, energy exploration footprints result in forest dissection and fragmentation contributing to declines in woodland caribou. Developing cost effective strategies to restore forests and thus conserving the woodland caribou habitat is a conservation priority. In this study, we compared the effects of wildfire and local variation in the amount of residual woody debris on natural regeneration in jack pine on exploratory well pads in Alberta’s boreal forest. Specifically, we investigated how footprint size, fire severity (overstory tree mortality), ground cover of fine and coarse woody debris, and adjacent stand characteristics (i.e., height, age, and cover), affected tree regeneration densities and height using negative binomial count and linear models (Gaussian), respectively. Regeneration density was 30% higher on exploratory well pads than adjacent forests, increased linearly with fire severity on the exploratory well pads (2.2% per 1% increase in fire severity), but non-linearly in adjacent forests (peaking at 51,000 stems/ha at 72% fire severity), and decreased with amount of woody debris on exploratory well pads (2.7% per 1% increase in woody debris cover). The height of regenerating trees on exploratory well pads decreased with fire severity (0.56 cm per 1% increase in fire severity) and was non-linearly related to coarse woody debris (peaking at 286 cm at 9.4% coarse woody debris cover). Heights of 3 and 5 m on exploratory well pads were predicted by 13- and 21-years post-fire, respectively. Our results demonstrate that wildfires can stimulate natural recovery of fire-adapted species, such as jack pine, on disturbances as large as exploratory well pads (500–1330 m2) and that the type and amount of woody debris affects these patterns.

Understanding Grass Invasion, Fire Severity, and Acacia koa Regeneration for Forest Restoration in Hawaiʻi Volcanoes National Park

With invasive grasses increasing wildfire occurrence worldwide, a better understanding of the relationships between native plants, fire, and invasive grass is needed to help restoration plans facilitate ecosystem resilience. Invasive grasses are particularly problematic for altering fire regimes in the tropics, yet in Hawaiʻi, restoration sites are often planted with monocultures of the native tree Acacia koa, which can promote grass growth via nitrogen fixation. This, combined with the difficulty of estimating pre-fire grass cover under thick canopies, complicates attempts to restore Hawaiian ecosystems. We studied the 2018 Keauhou Ranch Fire in Hawaiʻi to investigate three questions: (1) at what level of precision can pre-fire grass cover be accurately estimated from oblique aerial photos? (2) how are post-fire A. koa regeneration densities affected by fire severity? and (3) how are post-fire A. koa regeneration densities affected by pre-fire grass cover and its interaction with fire severity? We collected burn severity and post-fire regeneration data from 30 transects stratified across mid-elevation woodland, montane woodland, and montane shrubland communities. We evaluated visual estimates of pre-fire grass cover from oblique aerial imagery with quantitative in situ data from 60 unburned transects of the same cover types. Pre-fire estimates of grass cover categories were 67% accurate in montane woodland (n = 9) and 100% accurate in montane shrubland (n = 11), but only 20% accurate in mid-elevation woodland (n = 10). In montane woodlands with low pre-fire tree densities, A. koa regeneration densities were higher with increased fire severity, but this trend reversed when pre-fire tree densities were high. We detected no effect of pre-fire grass cover, nor its interaction with fire severity, on A. koa regeneration density. This indicates that restoration through the planting of A. koa may be successful in promoting fire-resilient A. koa forest, although there are potential issues to consider regarding the effects that A. koa’s grass promotion may have on other species within the ecosystem.

Does the high density of Psychotria shrubs in the understory influence the natural regeneration of trees?

Shrubs of the Psychotria L. (Rubiaceae) genus can occur like a dominant species in the understory of subtropical forests. This study aims to understand the ecological conditions of Psychotria dominance, specifically Psychotria leiocarpa Cham. & Schltdl. and Psychotria carthagenensis Jacq. in the understory, and its relation with natural tree regeneration. We sampled 162 plots of 1 m2 in an ecotonal Semi-deciduous Seasonal Forest remnant (243.28 ha) in the Pampa biome, in Southern Brazil. The analysis considered three habitat-selective regimes which occur in the remnant (road-edge, eucalyptus-edge, and forest-interior), and environmental variables (air temperature, relative humidity, canopy opening, inclination, solar exposition, altitude, and ground cover), according to which relationships between Psychotria and regenerating trees could be established in a different way. We assumed the hypothesis that the dominance of Psychotria shrubs in the understory may influence the natural regenerating trees and differ in relation to habitat-selective regimes and in function of environmental variables. No evidence of effective ecological dominance was found. The results indicated regular regeneration density for regenerating trees and for Psychotria shrubs. P. leiocarpa was predominant in the regeneration community, followed by regenerating trees and P. carthagenensis. In addition, P. carthagenensis demonstrated an aggregated behavior, forming few groups with high density. The environmental variables influenced the composition and/or abundance of the regeneration community and were more intense than the habitat-selective regimes. The habitat-selective regimes mostly acted in P. leiocarpa, which presented less density at the road-edge. Our results demonstrate that Psychotria shrub densities do not decrease the natural regeneration of trees, thus suggesting that P. leiocarpa and P. carthagenensis are multifunctional species which act in the understory as filters which favor ecological succession, even in different habitat-selective regimes. Therefore, they can be a key tool for ecological restoration and conservation, acting as core species in strategies to promote succession processes and ecological enrichment.

Low-density aspen seedling establishment is widespread following recent wildfires in the western United States.

Sexual regeneration is increasingly recognized as an important regeneration pathway for aspen in the western United States, a region previously thought to be too dry for seedling establishment except for during unusually wet periods. Because of this historical assumption, information on aspen seedling establishment and factors influencing its occurrence is limited and frequently anecdotal. We conducted a systematic field survey of 15 recent fire footprints that burned in 2018 in the western United States to quantify how common aspen seedling establishment is following fire and to identify factors associated with establishment. We found aspen seedling establishment in 12 of 15 (80%) of fire footprints surveyed, although densities were mostly low. Establishment probability was positively associated with mean annual precipitation and negatively associated with seed-source distance and the density of asexual aspen regeneration. Our results suggest that aspen seedling establishment may be a widespread, if often low-density, feature in postdisturbance areas. Even in low numbers, aspen seedlings may play a disproportionately large role in aspen regeneration ecology, providing adaptive capacity and facilitating local range expansion.

Accelerating the development of structural complexity: lidar analysis supports restoration as a tool in coastal Pacific Northwest forests

A century of land-use changes and intensive plantation-style forestry in the Pacific Northwest have resulted in a substantial deficit of structurally complex late-successional forests, which serve key ecological and social functions. Restoration treatments can theoretically accelerate the development of structural complexity in simplified forest stands, but our understanding of the short-term effects of such treatments on forest structure and gap patterns is still emerging. In this study, we used a bi-temporal airborne lidar dataset to assess short-term (10 years post-treatment) effects of restoration treatments on the structural complexity of forest stands in the Ellsworth Creek Preserve in southwestern Washington. We also compared forest structure and gap patterns between treated stands and existing late-successional areas within the preserve. Restoration treatments in older stands (60- to 80-years old) resulted in a greater increase in the mean and variability of both vertical and horizontal structural complexity and a considerable increase in the density of canopy gaps, indicating accelerated development towards increased structural complexity. Treatments in the younger stands (20- to 30-years old) primarily accelerated the development of vertical canopy complexity. Older treated stands within the preserve will require natural growth in canopy height, increased regeneration density, and filling in and diversification of canopy gaps to reach the structural complexity of late-successional forests in the preserve, but accelerating these developments may require additional restoration-focused treatments. Forest managers in the region should consider restoration treatments as a viable option for improving short-term structural complexity in simplified forest stands. We also encourage long-term management and monitoring plans that continue to address the deficit of late-successional forests in the region.

Natural regeneration of Norway spruce, an introduced species, in and around plantations in Quebec, Canada

Introduced species are used more and more for timber production throughout the world. This raises much debate about their impact on natural ecosystems. In Quebec, Canada, similar concerns are expressed regarding Norway spruce (Picea abies (L.) H. Karst.), which was introduced in the early 1900s and is currently the main non-native conifer used for planting. The purpose of the present study was to evaluate the current spread of Norway spruce in Quebec and to assess under which circumstances it can regenerate and become established. We studied Norway spruce regeneration dynamics over 5 years in the understory, edge and surroundings of 10thinned Norway spruce plantations aged 36 to 65 years. Most Norway spruce regeneration was found in the understory and near the edge of plantations, and beyond the plantation border on a few sites. Norway spruce seedling density was highly variable in the understory and at the plantation edge (0.6–30.7stems·m−2 and 0–8.5stems·m−2, respectively). Beyond the edge, high densities of Norway spruce regeneration (0.1 to 1.2 seedlings·m−2) were found in 2 recent clearcut areas and in only 2 intolerant hardwood high forests, as far as 28 m from Norway spruce plantations. Overall, Norway spruce regeneration was young (less than 16 years for 98% of seedlings) and relatively slow-growing (on average, 1.1–7.9 cm·year−1, depending on transect location and height class). Balsam fir (Abies balsamea (L.) Mill), a native species, regenerated well (mean density of 3.1stems·m−2) in the understory and the edge of 5 of the 10 studied plantations. When regeneration of both species was present, mean seedling age, growth and height were similar, but balsam fir had a better survival rate than Norway spruce (84% vs.65%). These findings suggest that Norway spruce shows a limited invasive capacity, particularly in the closed canopy of natural forests. Moreover, the presence of native balsam fir in the understory of Norway spruce plantations indicates that the successional pathway could move the stand towards a more natural ecosystem. These results can be useful to target surveys of the most sensitive ecosystems and to develop proactive management strategies.

Clarifying the factors affecting Larix gmelinii forest regeneration based on structural equation model

Based on data from 49 plots of natural Larix gmelinii forests in Cuigang Forest Farm of Xinlin Forestry Bureau, Daxing'anling Mountains, China, we used 37 measurable variables that mainly focused on stand non-spatial structure, stand spatial structure, species diversity, soil condition, and site condition to construct the structural equation model of natural regeneration densities and size diversities (i.e., height and ground-diameter). The direct, indirect, and total influence coefficients of each path were quantified to extract the critical and controllable factors that influence regeneration density and diversity of natural L. gmelinii forests, which would help implement sustainable forest management. The results showed that the effects of various latent variables on rege-neration density were following an order as: stand non-spatial structure (-0.410) > species diversity (0.380) > soil condition (0.250) > site condition (0.249) > stand spatial structure (0.197), while the order were changed as: soil condition (0.778) > site condition (0.748) > stand spatial structure (0.684) > stand non-spatial structure (0.287) > forest diversity (0.105), when evaluated on the regeneration diversity. Generally, the critical and controllable factors affecting rege-neration quantity and diversity were soil pH, total potassium concentration, species diversity, tree height diversity, uniform angle index and stand volume per hectare. In the management, suitable thinning treatments or replanting broadleaved trees were recommended for optimizing and adjusting species composition, species diversity, soil pH and nutrition, which would promote natural regene-ration.

Differing regeneration patterns after catastrophic fire and clearfelling: Implications for future stand dynamics and forest management

Silvicultural systems in native forests typically attempt to mimic natural disturbance regimes to ensure that the dominant tree species and associated biodiversity persist. Where the disturbance regime is driven by catastrophic, stand-replacing disturbances, such as fire and windstorms, even-aged (or single-cohort) silvicultural systems such as clearfelling (clearcutting) are commonly applied. However, there are important differences between stand-replacing natural disturbances and clearfelling. Considerable attention has focused on the biological legacies that persist after these disturbances (e standing dead trees, coarse woody debris). However, the inherent variability in regeneration patterns, which will drive long-term stand development patterns over the coming decades and centuries, has been largely overlooked. In this study we take advantage of a catastrophic fire event to compare patterns of regeneration for a dominant tree species after a high-intensity natural disturbance and after clearfelling. We focused on the mountain ash (Eucalyptus regnans F. Muell.) forests of southeastern Australia that were burned in the 2009 Black Saturday fire complex and are typically managed through clearfelling. We surveyed mountain ash seedling density in 24,200 quadrats across 121 plots (35 clearfelled, 86 burnt). We developed a statistical model to characterise the abundance and variability of seedling density. Our results demonstrated that natural regeneration density after the 2009 fires was nearly two times greater than regeneration at clearfelled sites that was aerially sown by helicopter. More importantly, however, the over-dispersion parameter in our model was nearly four times greater in the clearfelled sites than in the fire sites, meaning that regeneration in the clearfelled sites was much more spatially uniform than in the fire-affected sites. More than 50% of the surveyed quadrats in the fires sites had no mountain ash seedlings. The highly patchy distribution of natural regeneration has important implications for future stand development. Over time, patchy regeneration leads to structural variability that can benefit wildlife habitat and forest resilience to disturbances. A comparison of diameter distributions of stands that established at very different initial densities after the catastrophic 1939 fires shows the importance of early density on future stand structure. Our results provide an ecological basis for modifying current regeneration practices to better align contemporary forest management with natural disturbance regimes.

Species climatic niche explains post-fire regeneration of Aleppo pine (Pinus halepensis Mill.) under compounded effects of fire and drought in east Spain

Fire and drought are two major agents that shape Mediterranean ecosystems, but their interacting effects on forest resilience have not been yet fully addressed. We used Pinus halepensis to investigate how compound fire-drought regimes determine the success of post-fire regeneration. We measured the density of P.halepensis newly established individuals following fire in forty-three sites along the Spanish east coast, the wetter region of the species distribution. The climatic niche of P.halepensis was characterized by considering their populations across its Spanish distribution range. We used yearly values (1979–2013 period) of accumulated precipitation, mean temperature and the warmest quarter values of these two variables to generate the climatic space or climatic niche occupied by the species. Kernel density estimates were then applied to determine the niche centroid, which would correspond to the species’ climatic optimum within its Spanish distribution range. Then, we computed the pre- and post-fire climatic deviations of each sampling site as the difference between site-specific climate conditions respect to the species niche centroid, and assessed their relationship with the success of post-fire regeneration. We found highly variable patterns of post-fire regeneration density of P.halepensis over the studied sites, ranging from 7 to 42,822 tree pines ha−1. Generalized linear models indicated a positive relationship between fire severity and the density of P.halepensis regeneration. Positive temperature deviations - warm conditions - before fire were positively related to pine regeneration. This effect increases under higher fire severity. By contrast, warm temperatures after fire showed a negative effect on the density of pine trees. Positive precipitation deviations - wet conditions - after fire enhanced pine regeneration, while precipitation before fire did not had any significant effect. Though P.halepensis is considered a species adapted to fire and drought, the interaction between these two disturbances can alter the success of its post-fire recovery patterns limiting the species’ resilience in the future.

Tree mortality and regeneration of Euphrates poplar riparian forests along the Tarim River, Northwest China

BackgroundTree mortality and regeneration (seedling and sapling recruitment) are essential components of forest dynamics in arid regions, especially where subjected to serious eco-hydrological problems. In recent decades, the mortality of the Euphrates poplar (Populus euphratica) along the Tarim River in Northwest China has increased. However, few studies have quantified the causes of mortality and regeneration in this azonal riparian forest type.MethodsThe present study describes the annual hydrological response of tree mortality and regeneration in forest gaps. A total of 60 canopy gaps were investigated in six replicate grid plots (50 m × 50 m) and the annual runoff and water consumption data during the period of 1955–2016 were collected from hydrological stations in the middle reaches of the Tarim River. We compared the regeneration density of seedlings and saplings within the canopy gap areas (CGAs), undercanopy areas (UCAs), and uncovered riverbank areas (RBAs) through detailed field investigation.ResultsOur study found that the mortality of young and middle-aged gap makers has increased remarkably over recent decades, particularly since the year 1996. The main results indicated that regional water scarcity was the primary limiting factor for long-term changes in tree mortality, as shown by a significant correlation between the diameter at breast height (DBH) of dead trees and the annual surface water. The average density (or regeneration rate) of seedlings and saplings was highest in the RBAs, intermediate in the CGAs, and lowest in the UCAs. Compared with the UCAs, the CGAs promote tree regeneration to some extent by providing favorable conditions for the survival and growth of seedlings and saplings, which would otherwise be suppressed in the understory. Furthermore, although the density of seedlings and saplings in the CGAs was not as high as in the RBAs, the survival rate was higher in the CGAs than in the RBAs.ConclusionForest canopy gaps in floodplain areas can play a decisive role in the long-term germination and regeneration of plant species. However, as a typical phreatophyte in this hyper-arid region, the ecosystem structure, functions and services of this fragile P. euphratica floodplain forests are threatened by a continuous decrease of water resources, due to excessive water use for agricultural irrigation, which has resulted in a severe reduction of intact poplar forests. Furthermore, the survival of seedlings and saplings is influenced by light availability and soil water at the regional scale. Our findings suggest that policymakers may need to reconsider the restoration and regeneration measures implemented in riparian P. euphratica forests to improve flood water efficiency and create canopy gaps. Our results provide with valuable reference information for the conservation and sustainable development of floodplain forest ecosystems.

Biomass procurement in boreal forests affected by spruce budworm: effects on regeneration, costs, and carbon balance

Biomass procured from forests affected by natural disturbances as a bioenergy source is increasingly considered in the context of climate change mitigation. By comparing clearcuts with and without biomass procurement, we aimed to determine the effects of biomass extraction performed alongside lumber harvesting on regeneration density, number of planting microsites, forest renewal costs, and carbon fluxes, in harvested boreal stands affected by spruce budworm. The results showed that biomass procurement increased regeneration density and number of planting microsites. Reduction of downed woody debris due to biomass procurement lowered site preparation costs by 282.07 $CAN·ha−1, equivalent to 14.45 $CAN per oven-dry metric ton (odmt−1) of harvested biomass. Product value from biomass processing had to reach from 13.90 to 76.84 $CAN·odmt−1 to make biomass procurement operations profitable. Since biomass procurement significantly increased stocking and reduced the amount of decaying debris, it also reduced cumulative CO2 emissions relative to scenarios without biomass procurement. However, ensuring forest renewal through site preparation and plantation per se, irrespective of biomass procurement, played a more important role for carbon sequestration and net balance. Integrating biomass harvesting with silviculture could have significant ecological and financial impacts on forest management while supporting mitigation efforts against climate change.

Environmental and anthropogenic factors affecting natural regeneration of degraded dry Afromontane forest

Natural regeneration of trees may provide a cost‐effective way to restore degraded tropical dry forests, but the factors predominantly affecting natural regeneration success are poorly understood. We performed a multifactor analysis of natural regeneration in an Afromontane forest in Northern Ethiopia. Inventory plots of 400 m2, each with a nested 9 m2 subplot, were systematically established. All trees larger than 5 cm DBH and natural regeneration were identified and recorded in the plots and subplots, respectively. Variables describing climate, topography, soil, vegetation, and indications of local human degradation were collected. Determinants of regeneration presence and abundance were analyzed using Hurdle negative binomial regressions. Sixty‐nine woody species were represented in the regeneration, with an average regeneration density (SE) of 14,700 (51) ha−1. The presence of regeneration was positively associated with canopy cover (p < 0.001), distance to the road network (p = 0.04), precipitation (p = 0.003) and tree species diversity (p = 0.03), and negatively with Northing (p = 0.003). The regeneration abundance was positively associated with soil quality (p = 0.001), canopy cover (p = 0.04), and precipitation (p = 0.01). Including the abundance of dominant species in the tree canopy and regeneration layers in the regression model did not affect the presence of natural regeneration, but it clearly affected regeneration abundance. In such a model, the regeneration abundance was positively associated with Euclea racemosa seedlings abundance and negatively associated with the basal area of Dodonaea angustifolia (p = 0.02) and Rhus natalensis (p = 0.04). In this model, forest degradation (p = 0.01) negatively affected the late‐successional species regeneration but not the regeneration of the drought‐resistant light‐demanding species. The low representation of late‐successional trees species in the natural regeneration calls for active restoration intervention.

Post‐fire conifer regeneration hinders digital estimation of understorey plant cover in subalpine forest vegetation

AbstractQuestion: Reliable estimates of understorey (non‐tree) plant cover following fire are essential to assess early forest community recovery. Photographic digital image analysis (DIA) is frequently used in seral, single‐strata vegetation, given its greater objectivity and repeatability compared to observer visual estimation; however, its efficacy in multi‐strata forest vegetation may be compromised, where various visual obstructions (coarse downed wood [CDW], conifer regeneration, and shadows) may conceal plant cover in the digital imagery. We asked whether vegetation complexity influences plant cover estimated by DIA relative to two visual methods: plot‐level (20 m2) estimation (PLE) and quadrat‐level (1 m2) estimation (QLE)?Location: Greater Yellowstone Ecosystem, USA.Methods: We estimated understorey plant cover in subalpine forest vegetation on permanent plots (n = 141) at two study areas ~30 years after the 1988 Yellowstone fires to: (a) assess differences in visual obstructions between study areas in our digital imagery; (b) compare digital to visual estimates of plant cover; and (c) determine relationships between estimated plant cover and visual obstructions measured in situ.Results: Percent conifer regeneration pixels differed significantly (odds ratio = 8.34) between study areas which represented the greatest difference in visual obstructions. At the study area with lower conifer pixels, DIA estimated 9% (95% confidence interval [CI] = 3%–14%) and 16% (95% CI = 10%–21%) more understorey plant cover than PLE or QLE, respectively, but had comparable variability. At the study area with higher conifer pixels, DIA estimated 28% (95% CI = 24%–32%) and 22% (95% CI = 18%–26%) less understorey plant cover than PLE or QLE, respectively, and had more variability. Furthermore, plot‐level subcanopy regeneration (height>137 cm) density was negatively associated with digitally derived plant cover but showed no relationship with visually derived plant cover.Conclusions: Post‐fire conifer regeneration hindered the efficacy of DIA in estimating understorey plant cover. Digital estimation is advantageous in single‐strata vegetation but should not be used in complex, multi‐strata vegetation.

Factors Influencing the Natural Forest Regeneration at Khadimnagar National Park, Bangladesh

Natural regeneration is an indicator of a healthy forest, hence, understanding the influence of site factors on natural regeneration is a significant concern for ecologists. This work aimed to assess the impact of site factors on natural tree regeneration at Khadimnagar National Park (KNP). Biotic factors (tree density, tree species richness, and basal area), physical factors (elevation, canopy openness), and soil properties (bulk density, moisture content, soil pH, organic matter, sand, silt, and clay) data were investigated from 71 sample plots to examine their effects on natural regeneration density and richness in KNP. Stepwise multiple linear regression analysis was done to predict both regeneration density and regeneration richness. The results showed that soil pH (p<0.001), canopy openness (p<0.001), tree species richness (p<0.01), and bulk density (p<0.01) had a significant effect on regeneration density, explaining 42% of the total variation. Regeneration richness was driven by four factors: tree species richness (p<0.01), soil pH (p<0.001), elevation (p<0.01), and canopy openness (p<0.01) with a model that explained 60% of the total variation. This study observed that soil pH, tree species richness, and canopy openness are the main controlling factors that influenced both the density and richness of regenerating species in KNP. Therefore, these findings have implications for natural resource management, especially in selecting suitable silvicultural systems in a tropical forest under protected area management where enhanced tree cover and conservation of biodiversity are needed.

Effects of stand features and soil enzyme activity on spontaneous pedunculate oak regeneration in Scots pine dominated stands \u2013 implication for forest management

BackgroundA challenge in current forestry is adaptation of managed forests to climate change, which is likely to alter the main processes of forest dynamics, i.e. natural regeneration. Scots pine will probably lose some parts of its distribution area in Europe. However, two native oaks, pedunculate and sessile may maintain or expand the area of their occurrence in central Europe. The utilization of spontaneous (not initialized by foresters) oak regeneration in Scots pine stands for the creation of next generation stands is one of the adaptation methods to climate change. Many factors influencing pedunculate oak regeneration are well known, but there is a lack of knowledge on the relation between soil enzyme activity and the establishment and development of the species. The aim of the study was to identify the relationships among stand characteristics, herb species composition, soil enzyme activity and the establishment or recruitment of oak regeneration in Scots pine-dominated stands.ResultsThe one of the most influential factors shaping the oak seedling count was dehydrogenase activity in the humus horizon. We found that plots without litter and fern cover had higher seedling density. The raspberry ground cover and birch crown projection area had a positive influence on oak seedling number. The factor indicating good conditions for high density of oak saplings was phosphatase activity in the organic horizon. The same enzyme activity but in humus horizon described conditions in which more numerous recruits were observed.ConclusionsThe activity of soil enzymes can be used as the predictor of the establishment and advancement of oak regeneration but also could be seen as a new dimension of oak regeneration. The general density of spontaneous oak regeneration was not sufficient for the creation of new generation forest stands dominated by oak, but it is possible to use them as admixtures in new generation stands.

Correlation analysis of electroneuromyographic, functional-anatomical and morphometric indicators of regeneration of the injured sciatic nerve

Objective. To study the electrophysiological, functional-anatomical and morphometric indicators of the sciatic nerve regeneration after complete transection and connection of the nerve stumps with epineural sutures and adhesives. Materials and methods. The experiments were carried out on white outbred male rats. The efficiency of sciatic nerve regeneration was investigated with the standard 4-6 epineural sutures and the use of polyethylene glycol hydrogel Duraseal or Tisseel fibrin glue with 2 fixation sutures. On the 14th, 30th and 60th days after the complete transection of the sciatic nerve and subsequent connection of the nerve stumps with epineural sutures, hydrogel or fibrin glue, limb function was assessed using SFI test and ENMG. The distal segment of the nerve was sampled for electron microscopic and morphometric studies. The density of the regenerated myelinated nerve fibers was studied and a correlation analysis was performed with the results of SFI test and ENMG. Results. The use of adhesives provides a similar result of connecting the transected sciatic nerve, as in standard neurorrhaphy, and regeneration of myelinated nerve fibers in the distal nerve. The regeneration density of myelinated nerve fibers significantly increased on the 30 th and 60th days in the groups in which Duraseal hydrogel and Tisseel fibrin glue were used, without a statistically significant difference in ENMG parameters (M-response amplitude, nerve conduction velocity, latency period) and the result of SFI test. The amplitude of M-response on the 30th day was statistically significantly lower after the connection of nerve stumps with Tisseel fibrin glue in comparison with the Duraseal hydrogel, whereas on the 60th day there was no difference according to the results of electrophysiological studies. Conclusions. The efficiency of sciatic nerve regeneration after the combined connection exceeds the standard technique, and the results of pathophysiological assessments are more often correlated with morphometry data on the 30th day.

Effect of game browsing on natural regeneration of European beech (Fagus sylvatica L.) forests in the Krušné hory Mts. (Czech Republic and Germany)

Abstract Tree damage by game browsing is one of the biggest threats to forest ecosystems at the time of climate change and large-scale forest disturbances. The aim of the paper was to determine the effect of browsing by ungulates on the diversity, abundance and species composition of natural regeneration in forest stands dominated by European beech (Fagus sylvatica L.). The research was conducted on 10 permanent research plots in the Krušné hory Mts. in the Czech Republic and Germany. The density of natural regeneration was in the range of 23,300–114,100 recruits ha−1. A higher proportion of silver birch (Betula pendula Roth.) and rowan (Sorbus aucuparia L.) was found in the regeneration compared to the mature stands. A total of 78% of recruits was damaged by browsing. The most frequently damaged tree species were sycamore (Acer pseudoplatanus L.; 98%) and black alder (Alnus glutinosa [L.] Gaertn.; 97%), while Norway spruce (Picea abies [L.] Karst; 31%) and sessile oak (Quercus petraea [Matt.] Liebl.; 50%) were the least affected. Seventy-nine percent of European beech recruits were damaged. The game significantly reduced the height of regeneration by up to 40%, especially by terminal browsing. Browsing also negatively affected the quality and abundance of regeneration. For successful dynamics of species-rich natural forest ecosystems, it is necessary to minimize tree damage by game browsing. These main measures include the reduction of ungulate population levels and the optimization of their age structure and sex ratio, an increase in the number of overwintering enclosures and food fields for game and a change in the political approach to game management with sufficient consideration of forestry interests.

Gap regeneration and dynamics: the case study of mixed forests at Křtiny in the Czech Republic

Abstract Gap regeneration remains the best silviculture technique for sustainable forest regeneration in mixed forests. The study examined tree species composition, diversity and dynamics of natural regeneration in gaps under three contrasting forest stands at Křtiny in the Czech Republic. In spring 2013, experimental gap design begins, when semi-permanent 1 m2 circular sub-sampling plots along North-South-East-West transects were delineated under 6 selected natural canopy openings ≤ 20 m2. In winter 2013/14, these naturally originated openings were artificially enlarged to the current gap sizes ranging between 255 and 1149 m2 through group felling. Natural regeneration in gaps was measured four times: from the growing season before disturbance (BD) in 2013 to the next three consecutive growing seasons after disturbance in 2014 – 2016, respectively. Seven (7) new species with light demanding growth strategy that were previously not present at mother stands were occurring there during the first growing season after disturbance (FGS), yielding the highest taxa (14 species) and diversity (Shannon diversity index, H = 1.7) while BD attained the lowest (8 species; H = 0.9), respectively. Study site being part of Fagus sylvatica vegetation community and providing favorable natural conditions for the optimal growth of Picea abies significantly explains the regeneration dominance of these species in gap regeneration from BD until the third growing season after disturbance (TGS), respectively. Small scale gap-disturbance contributed to the higher regeneration densities of all studied species during FGS. However, drought, competition from other life forms, and browsing activities substantially caused a progressive decline in natural regeneration during three consecutive years after disturbance.

Moisture and vegetation cover limit ponderosa pine regeneration in high-severity burn patches in the southwestern US

BackgroundFire regimes are shifting in ponderosa pine (Pinus ponderosa Lawson & C. Lawson)-dominated forests, raising concern regarding future vegetation patterns and forest resilience, particularly within high-severity burn patches. The southwestern US has recently experienced a marked increase in large fires that produce large, high-severity patch interiors, with few surviving trees. These areas could be more susceptible for forest loss and conversions to alternative vegetation types than areas closer to the forest edge with more available seed sources. To better understand forest recovery, we surveyed ponderosa pine regeneration within edge and core areas (>200 m from edge) of high-severity patches in ten fires that burned between 1996 to 2008 across Arizona and New Mexico, USA. Specifically, we compared regeneration density, height, and canopy cover in patch edge and core areas and used generalized linear models to investigate the abiotic and biotic factors that contribute to ponderosa pine seedling establishment and density.ResultsHigh-severity burn-patch edge and core plots were not significantly different in seedling density, height, or canopy cover across fires. Seedling establishment was more likely at higher-elevation mesic sites and less likely when Gambel oak (Quercus gambelii Nutt.) was more abundant. Seedling density was negatively impacted by shrub, grass, and Gambel oak cover.ConclusionsRegeneration density varied among fires but analysis of regeneration in aggregated edge and core plots showed that abundance of seed availability was not the sole factor that limited ponderosa pine regeneration, probably because of surviving tree refugia within high-severity burn patches. Furthermore, our findings emphasize that ponderosa pine regeneration in our study area was significantly impacted by xeric topographic environments and vegetation competition. Continued warm and dry conditions and increased wildfire activity may delay the natural recovery of ponderosa pine forests, underscoring the importance of restoration efforts in large, high-severity burn patches.