Density Of Natural Regeneration Research Articles

A crop for a forest: Opuntia ficus-indica as a tool for the restoration of Mediterranean forests in areas at desertification risk

IntroductionThe Mediterranean is the European region with the lowest woody cover and the highest level of habitat degradation, being highly susceptible to climate change effects and desertification risk. In such worrying conditions, increasing woody cover and restoring forests is a major goal established in several international commitments. However, recruitment limitation of woody species is rather frequent both within natural regeneration processes and active restoration programs, particularly due to drought, overgrazing, and a lack of post-planting tending operations. Therefore, finding suitable tools to improve the recruitment success of native woody species is of crucial importance.MethodsWe assessed woody natural regeneration under abandoned prickly pear orchards, olive trees, and nearby open areas in three sites under high desertification risk in central Sicily (Italy). Then, we tested for differences in density, richness, diversity, height, and basal diameter of the woody recruiting species between these three habitats.Results and discussionNatural regeneration was widespread under prickly pear, with 94.6% of the sampled plots showing at least one recruit, in comparison to 61.6% of plots under olive and 22.3% in open areas. Natural regeneration density under prickly pears (114 ± 99 individuals m−2) was significantly higher (p < 0.001) than under olive trees (60.4 ± 76.4) and open areas (4.6 ± 9.3). Recruits’ diversity, basal diameter, and height were also significantly higher under prickly pear, concentrating 94.4% of the individuals higher than 100 cm and all late successional species. Our results indicate a great potential for prickly pears to accelerate the natural regeneration of Mediterranean woody species in pear instead of pears under desertification. However, a site-specific evaluation must be made taking into account prickly pear’s historical presence, temporary income as a crop, management capacity and, especially, its invasive potential.

Post-Fire Restoration and Deadwood Management: Microsite Dynamics and Their Impact on Natural Regeneration

After large and severe wildfires, the establishment of tree regeneration, particularly for species without specific fire-adaptive traits, can be challenging. Within harsh environments, the presence of favorable microsites, as those provided by deadwood, enhancing microclimatic conditions, is crucial to the re-establishment of forest cover and thus to foster recovery dynamics. Active restoration strategies can have an impact on these dynamics, altering or hindering them. The main hypothesis of this study is that manipulating deadwood in terms of quantity and spatial arrangement can result in differences in natural regeneration density and composition. Post-disturbance regeneration dynamics and the role played by deadwood over time in the creation of safe sites for seedling establishment were investigated in an area affected by a high-severity wildfire that underwent different post-fire restoration treatments along a gradient of increasing deadwood manipulation, spanning from salvage logging to non-intervention. Two inventories were performed 5 and 11 years after the fire. Ground cover proportion was significantly different among treatments, with lower values of lying deadwood in salvaged sites. A higher probability of regeneration establishment close to deadwood was found in both surveys, confirming the facilitating role of deadwood on post-fire forest regeneration. Microsite dynamics resulting from deadwood facilitation were highlighted, with establishment probability and anisotropic relationships between deadwood elements and seedlings changing over time, as recovery processes slowly improved environmental conditions. In dry mountain areas affected by stand-replacing wildfires, by removing deadwood, salvage logging reduces the number of safe sites for regeneration, further impairing the ecosystem recovery. Passive management should be the ecologically preferred management strategy in these conditions, although intermediate interventions (e.g., felling without delimbing, leaving deadwood on the ground) could be effective alternatives, accelerating snag fall dynamics and immediately increasing favorable microsite availability.

Natural regeneration potential and dynamics in boreal lichen woodlands of eastern Canada following soil scarification

Boreal lichen woodlands (LWs) are stable low tree-density zones of the Canadian boreal forest whose afforestation has been proposed as a way to create new C sinks and thus mitigate climate change. Planting operations in these remote areas are however costly and time-consuming, and may not be necessary when soil scarification is followed by dense natural regeneration. In the present study, we assessed the natural regeneration potential and dynamics in six boreal LWs of Québec, Canada, 11 years after soil scarification. The number, size (height and stem diameter) and age of seedlings were measured in 2-4 sampling plots per site (18 plots in total). Our data show that scarification operations produced on average 1,400 m2 ha–1 of exposed mineral soil (scarification intensity of 14%) with, however, a large within-site variability. The natural regeneration was mainly composed of black spruce seedlings (> 95%), averaged ∼12,000 seedlings ha–1 across the six sites and significantly varied among sites, mostly due to the variation in scarification intensity. Seedling density averaged ∼9 seedlings m–2 of exposed mineral soil and increased with seed tree mean diameter at breast height (DBH) (R2 = 0.51; P < 0.05) but not with the density of seed trees, revealing the importance of old and large seed trees in natural regeneration success. Together, scarification intensity and the DBH of remaining seed trees explained ∼60% of the variation in natural regeneration density across the 18 sampled plots. The rate of establishment of seedlings was generally high – with on average 60% of the carrying capacity of the substrate being reached within three years following scarification – and increased with seed tree mean DBH (R2 = 0.77; P < 0.05). However, the growth rate of seedlings was very low. Eleven years after scarification, 60% of the seedlings were < 15 cm and the height of 10-yr-old seedlings averaged 27.5 cm. Thus, even though seedling establishment was successful, the biomass accumulated by the natural regeneration was negligible in the span of a decade. Therefore, the implementation of afforestation following scarification appears to be necessary to create significant C sinks in the midterm.

A new methodology to evaluate natural regeneration: A case study of Quercus ilex in the montado in Portugal

Regeneration and recruitment are primordial for stand sustainability. However, natural regeneration is usually only evaluated by density and height, so no details are provided regarding the individual traits of the saplings/seedlings. Hence, the findings of these regeneration studies are of limited selection power in future management. The main goal of this study was to develop a new methodology that enables the evaluation of individual quality traits of regeneration in the early stages of stand development so that their future potential development can be assessed. Natural regeneration (NR) was evaluated in each field plot using the conjugation of two new methods: first using the natural regeneration density (NRD) method and second using the new natural regeneration tree classification (NRTC). NRTC is composed of a set of criteria with categorical variables that allow the evaluation of traits of individuals and their potential for future recruitment. In this classification system, five criteria were used, namely, upper story influence to evaluate the competition of the trees of the upper story cast on the regeneration individuals, crown isolation to characterize the competition between saplings, height as a surrogate of sapling development, diameter as a proxy of growth, and tree habit as a proxy of the habit of saplings. To test both methods, we applied them in a case study of Quercus ilex in the montado agroforestry system in Portugal, where different degrees of crown cover coexist. Our results indicated that in 85% of the plots with a crown cover higher than 30%, we could find good-quality natural regeneration oak saplings suited to be recruited and located outside of the upper story crown projection. Only 15% of the plots with a crown cover higher than 30% were dominated by Cistus ladanifer and had almost no oak saplings. In future, we suggest that the NRTC be used in all NR individuals in the forest inventory when the NR density is less than 200 NR individuals ha−1.

Forest Gaps Modulate the Composition and Co-Occurrence Network of Soil Bacterial Community in Larix principis-rupprechtii Mayr Plantation

Forest gaps create a favorable microenvironment for the growth of the soil microbial community. This study aimed to explore the effects of gap-related microenvironmental heterogeneity on soil bacterial communities in Larix principis-rupprechtii Mayr forest gaps. Therefore, the redundancy analysis (RDA) and structure equations modeling (SEM) of affecting elements were further used to test the significance of forest gaps’ effect on soil bacterial community composition and co-occurrence structure complexity. The formation of forest gaps increased canopy opening (CO) and significantly increased soil moisture content (SW), soil temperature (ST) and the accumulation of acid phosphatase (PHO) and sucrase (INV) in the soil, and the G250 (forest gap size: >250 m2) was most conductive to the accumulation of light and soil total nutrient. G50, G70, and G100 (forest gap size: 50–70 m2, 70–100 m2, 100–125 m2) were most favorable for the natural regeneration of the L. principis-rupprechtii Mayr plantation. The light properties under the forest gaps were the most significant factor that influenced the soil bacterial community composition, followed by the size of the forest gap, with standard path coefficients (Std. PCs) of 0.45 and −0.37, respectively. The canopy opening (CO), relative light intensity (RLA) and leaf area index (LAI) were considered to be the most important environmental factors affecting bacterial community composition (Std. PCs: 0.97, 0.99, and −0.93, respectively). The natural regeneration density under the forest gap was the most significant factor influencing the complexity of the soil bacterial community co-occurrence network, followed by soil nutrients (Std. PCs: 0.87 and −0.76, respectively).

CHARACTERISTICS OF NATURAL OAK FORESTS AND NATURAL RENEWAL IN THE CONDITIONS OF SE «TULCHINSKE LMG»

It was established that the territory of the farm belongs to the following forest categories: forests of nature protection, scientific, historical and cultural purposes – 1322.4 ha; recreational and health forests – 718 ha; protective forests – 3837.9 ha; exploitation forests – 17,407.7 ha. As a result of conducted field research within the forest fund of the enterprise, it was established that plantations over 100 years old are characterized by the predominance of common oak with the participation of common ash in the composition. It has been established that within the boundaries of the forest and hunting economy, among the areas where it is planned to carry out felling for the main use, plantations that are classified as exploitation forests predominate. The total area of such plantations is 152.3 hectares, and the number of plots is 47. It was determined that the number of areas of oak forests over 100 years old that will be felled in the next audit period during felling of the main use in protective and recreational forests is 6 and 5, respectively. According to the above results, out of the total number of main-use felling plots – 58 forest stands of fresh hornbeam forest – 55. Only 3 plots are located in wet hornbeam forest. Accordingly, the largest areas of main felling areas – 179.9 hectares – are concentrated in fresh hornbeam forest. It was investigated that the territory of the farm belongs to high credit standings (credit rating 1-1a-2). The largest number and area of plots is characterized by the 1st rating (42 plots with an area of 114.0 ha). There are almost 2-3 times less plots of 2 rating (15 plots, with an area of 68.3 hectares). In the process of conducting research, we discovered a significant number of stands with possible natural regeneration. The total share of such stands in relation to the total number is 3.75 %, and from the total area – 4.88 %. Accordingly, the maximum area of a separate plot is 10.5 hectares, and the minimum is 2.5 hectares. According to the conducted research, out of 80 plots, 37 lack any natural regeneration in sufficient quantity.It was determined that the average age of natural renewal is 11 years. The height is 3.6 m, the density of natural regeneration is 7.7 thousand pieces/ha, the average age is 23.6 years.

The naturalization of the almond Prunus dulcis in different ecological contexts in the Mediterranean: An underestimated process?

Although Prunus dulcis has been frequently listed in non-native floras all around the world, its naturalization has been rarely studied in the field. Probably, because this species has generally invaded synanthropic habitats. We assessed the density of natural regeneration of almond, biometric parameters (height and basal stem diameter), and the distribution in life stage classes in three different ecological contexts in Sicily (Mediterranean Italy): one natural habitat (maquis), one pine afforestation and two prickly pear orchards. We recorded 236 naturally regenerating almond individuals, with density ranging from 140 individuals per hectare (prickly pear orchard 1) up to 2,400 individuals per hectare (pine afforestation). Despite the higher density, almond individuals presented the lowest height and basal stem diameter under pine afforestation, suggesting a more recent establishment. Reproductive individuals were dominant (67.8%), followed by pre-reproductive (22.1%), and juveniles (10.1%). Although the naturalization of the almond in Mediterranean contexts is not new, in the last two decades there is evidence of an increasing trend. Most importantly, for the first time, we found the almond thriving within a natural habitat in large areas covered by Mediterranean maquis. Since the almond appears to be perfectly integrated within local plant communities, the origin and meaning of this peculiar vegetation aspect deserve to be further deepened.

Drivers of ash (Fraxinus excelsior L.) natural regeneration spread into suboptimal sites – Refugee or dead end?

Ash disease caused by ascomycete fungus Hymenoscyphus fraxineus leads to the retreat of ash, particularly in ash-dominated stands characterized by moist, fertile, and neutral soils. Thus, it has a more severe impact on species regeneration and survival in ash optimal sites. We aimed to investigate the joint effects of seed dispersal limitation triggered by the distance from seed source, as well as soil fertility, browsing, and understory vegetation on ash natural regeneration in optimal and neighboring suboptimal sites. We examined ash regeneration within 40 circular plots (25 m2) in Western Poland along soil fertility gradient and increasing distance from seed source (0–100 m). We confirmed the seed dispersal limitation of ash regeneration. We found that the increase of distance from seed source increases ash natural regeneration (both of <0.6 and 0.6–1.3 m height) survival by escaping distance-dependent mortality, referring to the Janzen-Connell effect. Moreover, soil drivers i.e. groundwater table level, CaCO3, and soil C:N influenced ash regeneration damage rate. Furthermore, we indicated that light availability can enhance ash regeneration. We found the highest browsing in sites with the highest ash natural regeneration density. Understory species composition was related to ash regeneration density, browsing, and damage proportion, indicating that species typical of mesic broadleaved forests can be considered as positive indicators of the ash regeneration niche. In conclusion, we state that suboptimal sites can act as refugees for ash, helping this species to persist over ash dieback. Therefore, we recommend broadening the scope of ash conservation and silviculture into suboptimal sites, that can host ash regeneration and allow it to emerge and reproduce. Such sites in the neighborhood of typical ash sites damaged by H. fraxineus can in the future serve as seed sources for forest regeneration and improve the resilience of the forest ecosystem.

Effects of Gap Size and Cardinal Directions on Natural Regeneration, Growth Dynamics of Trees outside the Gaps and Soil Properties in European Beech Forests of Southern Italy

The present study was focused on how cardinal directions inside gaps of different sizes (small, 200 m2; medium, 400 m2; and large, 600 m2) can affect soil characteristics and tree regeneration. Additionally, the effects of gap size on the growth dynamics of trees outside the gaps were evaluated. The study was carried out in a European beech stand located in Aspromonte National Park (Southern Apennines, Calabria, Italy). Microclimatic variables, physical, chemical, and biochemical soil properties, natural regeneration density, and growth trees outside the gaps density of natural regeneration were assessed. This study provided evidence for an important effect of cardinal points on micro-environmental parameter variability, nutrient cycle, physic-chemical soil properties, water availability, and biological processes such as trees growth and regeneration. The European beech natural regeneration was most abundant in the south part of the gaps. Thus, we can state that cardinal points affect the trees natural regeneration in a species-specific manner. The new microclimatic conditions due to the gap opening had positive effects on the tree growth located along the gap edge, especially in the trees sampled on the edges of the medium gaps. On the contrary, the trees located in the forest recorded a productivity coherent with the period prior the gap opening. In medium-sized gaps, the combination and interaction of microclimatic and soil parameters (humification and mineralization process and microbial activity) created the best conditions for beech natural regeneration and favored an increase in the productivity of the trees at the edge of the gaps.

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.

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&lt;0.001), canopy openness (p&lt;0.001), tree species richness (p&lt;0.01), and bulk density (p&lt;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&lt;0.01), soil pH (p&lt;0.001), elevation (p&lt;0.01), and canopy openness (p&lt;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.

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.

Ecosystem restoration after bauxite mining: favorable indicators for Technosols construction and soil management using liming and subsoiling

Although its economic importance, bauxite mining causes the loss of natural ecosystems. In this sense, the Technosols building from materials made or modified by man, such as mine tailings, is necessary for recovering degraded areas. Additionally, the Technosols management, such as subsoiling and liming, increases chances of plants establishment and growth. In this study, a degraded area by bauxite mining with constructed Technosol in the Eastern Amazon, Brazil, was tested under three different soil management treatments: Technosol-1 (Tech-1), Liming only; Technosol-2 (Tech-2), Subsoiling + 200 g of NPK in the pit; Technosol-3 (Tech-3), Scarification + liming + all Tech-2 procedures. In every treatment and in a reference forest (R-forest), 8 years after the initial seedling planting, three types of indicators were assessed: structural (horizontal vegetation structure, density of natural regeneration, and soil cover), compositional (species diversity, ecological groups, and dispersal syndromes), and functional (chemical properties of Technosols and dry matter and nutrients from the litter stock). The most representative species in all treatments were Croton matourensis and Vismia guianensis, both coming from the natural regeneration and common in early successional stages. Coverage rates in all treatments showed less than 5% of exposed Technosol and the diversity, ecological group, and dispersal syndrome indexes followed a successful trajectory along 8 years. Tech-2 and Tech-3 presented the best chemical attributes and nutrients in the litter stock, but they would probably last several decades to reach the R-forest attributes. Thus, subsoiling alone or with liming provided the best chemical results for soil, litter, and vegetation performance, being recommended to speed up restoration of degrades areas by bauxite mining in the Amazon.

Anthropogenic disturbances stimulate natural regeneration of Euxylophora paraensis Huber in a forest fragment in the eastern Amazon

In the Brazilian Amazon, forest fragments increase annually leading many species to local extinction. Euxylophora paraensis Huber is an endemic species whose natural habitat is restricted to the north of Brazil. The natural regeneration was evaluated using 10 circular plots of land each with a radius of 20 meters. The density of regenerating individuals at the edge and the interior of the fragment and the behavior in relation to the parent tree. The Periodic Annual Increment of the diameter and the height were calculated individually for each plant that remained alive during all four measurements and GLM (General Linear Model) was applied to verify if there were differences between environments and the size of the individuals. The results show that the density of natural regeneration increases as the distance from the parent tree increases and has a significant negative correlation with canopy area, the smaller the canopy area the higher the density of individuals. Larger diametric growth was observed in saplings and small trees at the edge and larger increments of height in small trees were observed both at the edge and interior of the fragments. Therefore, natural regeneration is influenced by the process of forest fragmentation where the germination of seeds and establishment of saplings is favorable, however, there were no adult trees at the edge.

Modelling potential density of natural regeneration of European oak species (Quercus robur L., Quercus petraea (Matt.) Liebl.) depending on the distance to the potential seed source: Methodological approach for modelling dispersal from inventory data at forest enterprise level

The use of natural oak regeneration from admixed oaks and neighbouring oak stands provides an interesting alternative to cost-intensive artificial oak regeneration when aiming for forest conversion of pure coniferous stands. In this study analysis of forest inventory data is done on how far and in what density natural regeneration of both Pedunculate and Sessile oak occurs in coniferous stands.In order to investigate as exclusively as possible the effect of distance to the seed source on the regeneration density of both oaks, the regeneration potential was determined by using quantile regression. By applying a .995th quantile, reducing factors on seedling density, e.g. desiccation, browsing, pathogens or limited resource availability, were excluded as much as possible. Thus, the effect of zoochorus vectors on effective dispersal could be quantified.The regeneration potential was determined based on data from the forest inventory of the Saxony state forest enterprise, Germany, including 2357 sample plots. Remote sensing data, including the location of oaks in the overstorey, were used to determine the distance to the nearest potential seed source.The results of the present study demonstrate that the highest regeneration densities are not found in the immediate vicinity of the nearest seed source, but at distances between 60 and 140 m to it, i.e. the maximum of seedling density per area unit is in some distance to the trees trunk. In the present study, dispersal distances of established regeneration up to 1565 m were detected. From a distance of 1570–2300 m on, there was no oak regeneration.The results prove that acorns are taken from the seed source and that, in addition to barochorus dispersal, the zoochorus dispersal is of great importance for the succession of coniferous stands. The position of potential seed sources is therefore an important information for silvicultural planning, in order to estimate potential oak regeneration densities.

Ash dieback, soil and deer browsing influence natural regeneration of European ash (Fraxinus excelsior L.)

European ash (Fraxinus excelsior L.) dieback affects both overstory trees and natural regeneration. The decline of ash caused by severe crown defoliation and branch mortality has a high impact on ash natural regeneration. The site factors affecting the disease symptoms vary significantly and are not fully understood. Hence, we aimed to assess the joined effects of soil fertility and moisture (expressed by soil pH, CaCO3 content, and summer groundwater table level), herbivory, and health conditions connected with Hymenoscyphus fraxineus (T. Kowalski) Baral, Queloz, and Hosoya infestation on natural regeneration of F. excelsior. We examined 32 ash stands in Western Poland across soil fertility gradient. We established randomly selected circular plots (400 m2) in forests with ≥60% of ash in overstory species composition. We assessed natural regeneration density, the proportion of browsed trees, and trees damaged by ash dieback using generalized mixed-effects models. We found a higher proportion of damaged trees in neutral and base soils than in acid soils. Moreover, we found a low proportion of damaged trees in sites with low groundwater table levels. High CaCO3 content decreased the proportion of browsed trees, similarly as high shrub cover. The density of F. excelsior natural regeneration depended on groundwater table level, canopy cover, and proportion of damaged trees. We also found a positive relationship between density and deer browsing. The factor responsible for the higher infestation of saplings (low groundwater table level) also influenced natural regeneration density. This way, our study revealed how soil properties influence ash natural regeneration directly and indirectly. We showed that ash dieback will have a more severe impact on ash regeneration in ash typical sites. This is essential for predicting forest recovery and the ability to resilience after disturbances caused by H. fraxineus. CapsuleJoined effects of ash dieback, soil pH, and CaCO3 content, together with soil moisture, as well as deer browsing, affect ash regeneration.

Effect of Invasive Rhododendron ponticum L. on Natural Regeneration and Structure of Fagus orientalis Lipsky Forests in the Black Sea Region

Biological invasions threaten global biodiversity and forest ecosystems; therefore, it is necessary to use appropriate strategies for combating the spread of invasive species. Natural regeneration of eastern beech (Fagus orientalis Lipsky) is considerably limited by an aggressive invasive shrub, pontic rhododendron (Rhododendron ponticum L.), in the Black Sea Region of Turkey. Therefore, the future character of the region’s forests is uncertain. The aim of this research was to evaluate the structure of beech forests with different management regimes of rhododedron and to determine the interaction among tree layer, rhododendron cover, and natural regeneration in Düzce Province using the FieldMap technology. The following variants of forests were compared: without intervention (control) and three and six years after rhododendron clearance. The results showed that tree density ranged between 175–381 trees ha−1 and stand volume between 331–589 m3 ha−1. The horizontal structure of the tree layer was mostly random, and the spatial pattern of natural regeneration was aggregated. Recruit density and height in the beech stands were significantly differentiated due to the influence of presence or absence of invasive rhododendron. Rhododendron cover ranged between 81%–97%, and woody stems amounted to 72,178–86,884 ha−1 in unmanaged forests. Canopy in the overstory did not have a significant effect on the density of regeneration and rhododendron cover. Tree layer had a significant negative influence on natural regeneration within a 4 m radius on the plots without rhododendron. However, on the plots with dense rhododendron cover, tree layer had a positive influence on regeneration within a 1.5 m radius. Natural regeneration density was significantly higher when rhododendron was cleared than the plots without intervention. On the plots without woody clearance, there was an insufficient regeneration (113–619 recruits ha−1); however, they had higher mean height compared to the sites without rhododendron. After three and six years of rhododendron clearance, the numbers of recruits in natural regeneration were 63,981 ha−1 and 105,075 ha−1, respectively. In conclusion, invasive spread of rhododendron was a limiting factor of the prosperous regeneration and tree species diversity, and manual clearance of rhododendron is recommended in managed beech forests of the study region.

First Assessment of Natural Regeneration and Seed Dispersal of Persian Walnut (Juglans regia L.) in Mediterranean Agroecosystems

Persian walnut (Juglans regia L.), which is native to Central Asia, has been widely cultivated throughout Europe over millennia as a multipurpose tree. However, only recently the naturalization process outside cultivation has been studied, mostly in temperate Europe, with no information regarding the Mediterranean region. Here we provide the first field investigations about the natural regeneration of walnut in two traditional Mediterranean agroecosystems: an irrigated mixed orchard in suburban areas and a non-irrigated prickly pear (Opuntia ficusindica [L.] Mill.) orchard. The natural regeneration densities were statistically different in the two agroecosystems, ranging from 75 individuals per hectare in the prickly pear orchard to 200 individuals per hectare in the mixed orchard. Crows were frequently observed actively carrying walnuts in both environments. The irrigation practices and the shade provided by larger trees in the mixed orchard, and the potential benefits provided by prickly pear individuals, seemed to be crucial for seedling establishment and development in the two orchards, respectively. On the other hand, climate does not seem to represent a constraint for walnut recruitment, even if the mean annual temperature at the mixed orchard is slightly above the optimal temperature for walnut. Other biotic and abiotic factors that may trigger or hamper the naturalization process are also discussed in this paper, which explores the research needs for better understanding the naturalization potential of the Persian walnut in Mediterranean agroecosystems, as well as the effects of different land uses and future climate change on this process.

Consumption of Euterpe edulis fruit by wildlife: implications for conservation and management of the Southern Brazilian Atlantic Forest.

This study aimed to measure the wildlife consumption of Euterpe edulis fruit and use this data to discuss management possibilities. To estimate infructescence fruit volume consumed, collectors were installed in fruit-bearing palms. To characterize consumption from the ground, samples were placed next to fruiting palms. To identify wildlife and their activities, camera traps were installed in infructescences and on the ground. The results suggested that there was a small fruit surplus (1.8 %), and this finding indicated the possibility of a harvest to reduce food for the wildlife. However, recurrent variations in the annual fruit production (21.4 %) were also noted, and suggested that wildlife could tolerate some fruit harvesting. Thus, a harvest could be restricted to fruit volume that exceeds the annual average (94 kg/ha/year). Turdus flavipes, a migratory bird, was the most active species in the dispersal of seeds; this finding indicates the need for broader conservation strategies. Wildlife composition also changed along with the fruiting, and this alteration suggests that dependence on the fruit is variable among different species. Seed germination and seedling mortality were high, results that indicate that local conditions may have a predominant effect on seed volume in natural regeneration density.