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The potential utilisation of natural regeneration of European beech (Fagus sylvatica L.) for forest conversion has received little attention to date. Ecological knowledge is necessary to understand and predict successful natural regeneration of beech. The objective of this study was to improve understanding of what drives the occurrence of beech regeneration and, once regeneration is present, what drives its density. In the study, we utilised a forest inventory dataset provided by Sachsenforst, the state forestry service of Saxony, Germany. The dataset was derived from 8725 permanent plots. Zero-altered negative binomial models (ZANB) with spatial random effects were used to analyse factors influencing occurrence and density simultaneously. The results provided by the spatial ZANB models revealed that the probability of the occurrence of beech regeneration is highly dependent on seed availability, i.e. dependent on source trees in close proximity to a plot. The probability of beech regeneration rises with the increasing diameter of a potential seed tree and decreases with increasing distance to the nearest potential seed source. The occurrence of regeneration is affected by overstorey composition and competition exerted by spruce regeneration. Where sites are affected by groundwater or temporary waterlogging, the impact on the occurrence of regeneration is negative. Although distance to the nearest potential seed source has an influence on occurrence, this variable exerts no influence on density. A high regeneration density arises in conjunction with a high beech basal area in the overstorey. Beech regeneration density, but not occurrence, is negatively affected by browsing intensity. These variables can be used to predict the occurrence and density of beech regeneration in space to a high level of precision. The established statistical tool can be used for decision-making when planning forest conversion using natural regeneration.

The genetic diversity and mating status of seed production stands are crucial factors impacting the genetic quality and ecological stability of progeny plantations. The genetic homogeneity of seeds collected from a seed production population in different years has not yet been clearly described. In this study, the genetic diversity and differentiation of a seed-tree stand of 58-year-old Pinus massoniana (P1959) and four-open pollinated plantations of its progeny (OS1996, OS2000, OS2006 and OS2015) were determined by using microsatellite markers. The results showed that similar high genetic diversity was preserved in the seed-tree stand and its four progenies. This implied that current artificial seed harvesting from the seed-tree stand for reforestation does not lead to a significant reduction in genetic diversity; the F index across most loci was significantly greater than zero, indicating population homozygote excess. The pairwise genetic differentiation of the five populations ranged from 0.035 to 0.075, among which OS2015 was the most differentiated from the parent. The differentiation between the parental population and its progeny seemed to increase with increasing age of the seed-trees. This implied that a limited pollination coupled with variable within-stand pollen availability has created opportunities for both self- and foreign pollination to be successful in various periods, resulting in a seemingly paradoxical scenario of both high selfing and gene flow, ultimately resulting in gradually increasing differences in the gene frequency composition between the parental population and its progeny. Management considerations in addressing these problems in similar seed production stands were discussed.

Particularly after disturbance events, the early successional colonistBetula pendulaRoth is experiencing renewed silvicultural interest with respect to the natural regeneration of large disturbed forest areas. In a case study, we therefore studied the seed dispersal ofB. pendulafrom two adjacent spruce stands to large storm-felled sites at high altitudes in the Thuringian Forest (Germany) over a 2-year period. We applied inverse modelling to describe the distance-dependent seed distribution using a negative exponential kernel and seed production function of birch seed trees. Maximum seed numbers of 2015 n m−2(non-mast year) and 9557 n m−2(medium year) occurred within 40‒50 m distance to a seed tree. The predicted seed production rate of a birch seed tree with a reference dbh of 20 cm was approximately 350,000 n tree−1(non-mast year) and 1,500,000 n tree−1(medium year). Regardless of the seed crop, the dispersal distances were similar in both years. The isotropic model showed mean dispersal distances of 86 and 97 m (uphill) and 367 and 380 m (downhill) for the 2 years of seed sampling. No directionality in seed dispersal was found. The findings showed birch seed dispersal to be strongly influenced by site inclination, seed tree position (valley, slope or plateau) and distance to the storm-felled site. Furthermore, the seed shadow is influenced by the number of seed sources. Therefore, risk-adapted forest management should include the ‘spatial optimization’ of birch seed trees, ideally creating a network of small seed tree groups scattered more or less regularly within pure conifer forests.

Protein variation among 37 species of carcharhiniform sharks was examined at 17 presumed loci. Evolutionary trees were inferred from these data using both cladistic character and a distance Wagner analysis. Initial cladistic character analysis resulted in more than 30 000 equally parsimonious tree arrangements. Randomization tests designed to evaluate the phylogenetic information content of the data suggest the data are highly significantly different from random in spite of the large number of parsimonious trees produced. Different starting seed trees were found to influence the kind of tree topologies discovered by the heuristic branch swapping algorithm used. The trees generated during the early phases of branch swapping on a single seed tree were found to be topologically similar to those generated throughout the course of branch swapping. Successive weighting increased the frequency and the consistency with which certain clades were found during the course of branch swapping, causing the semi-strict consensus to be more resolved. Successive weighting also appeared resilient to the bias associated with the choice of initial seed tree causing analyses seeded with different trees to converge on identical final character weights and the same semi-strict consensus tree. The summary cladistic character analysis and the distance Wagner analysis both support the monophyly of two major clades, the genus Rhizoprionodon and the genus Sphyrna.. The distance Wagner analysis also supports the monophyly of the genus Carcharhinus. However, the cladistic analysis suggests that Carcharhinus is a paraphyletic group that includes the blue shark Prionace glauca.

Introduction: Regeneration of forest stands under management is one of the most relevant silvicultural practices for forest cultivation. Objective: To compare growth and water balance for both naturally regenerated and planted seedlings in Pinus patula Schltdl. &Cham. stands harvested with the seed tree method in the ejido Carbonero Jacales, Huayacocotla, Veracruz. Materials and methods: Four sites per stand with natural regeneration and planted seedlings were selected for paired comparison. Origin and age of seedlings were recorded at each site, water potential was measured throughout the day during the dry season in 2019, also annual height and diameter growth at the base of the stem during the period 2018-2019. Results: Naturally regenerated seedlings had significantly (P ≤ 0.01) higher annual height growth (73.8 ± 12.29 cm) compared to planted seedlings (60.8 ± 12.39 cm); the same was for diameter at stem base (20.52 ± 3.51 vs. 14.76 ± 3.54 mm). Natural regeneration also showed significantly higher (P ≤ 0.05) diurnal water deficit recovery capacity (-0.90 MPa) compared to planted seedlings (-1.06 MPa). Conclusion:P. patula naturally regenerated seedlings had better annual growth and better physiological performance in root, which allowed a faster recovery to diurnal water deficit in foliage.

Wide-spread use of single-tree harvest methods has inhibited regeneration of yellow birch in shade-tolerant hardwood forests. Shelterwood harvesting can improve recruitment, but incurs higher costs, longer harvesting cycles, and produces an even-aged structure. Group selection (GS) harvesting provides an alternative method with the benefits of single-tree selection (STS; mixed-ages, shorter cycles), yet produces larger gaps that may favour recruitment of mid/intolerant tree species. Recent GS trial studies have shown promise, but results vary and differences in edaphic conditions and competition dynamics associated with climate, historical management, and season of harvesting may influence responses. We evaluated the yellow birch recruitment efficacy of GS in an Ontario shade-tolerant hardwood forest by comparing change in regeneration as percent ground cover (stems 50 cm) over ten years in STS harvested and unharvested forest relative to two types of GS gaps: “typical” gaps placed in suitable microsites, and indiscriminate “systematic” interval gaps harvested on a grid. Autumn-harvested gaps established 2–4× more yellow birch cover and recruited 7–10× more large stems by year ten than STS and winter harvested gaps; unharvested controls remained unchanged. Typical gaps recruited 3× more stems than systematic gaps in autumn-only. Soil disturbance and seed tree proximity were correlated to establishment of yellow birch cover in year 1, which predicted large stem recruitment by year 10. Winter-harvesting favoured sugar maple cover in year 1, which predicted lower yellow birch recruitment by year 10. These results indicate that autumn-harvested typical gaps optimised germination and growth conditions for yellow birch (light availability, soil disturbance, reduced competition, seed proximity/dispersal). Consequently, GS harvesting in autumn can be considered an effective alternative to shelterwood harvesting for yellow birch recruitment in poorly-represented shade-tolerant hardwood stands.

Introduction:Forest managers need to know the impact of regeneration cuts on tree species diversity in order to conserve it. Objective:To evaluate changes in tree species richness and diversity after applying the seed tree method in six communities. Materials and methods: The communities of Cienega Grande, Las Cienegas, La Colmena, El Venado, Los Bajios and Pino Gordo of the Pueblo Nuevo ejido, Durango, were divided into three plots called: a) regeneration in seed trees cuttings (RST); b) regeneration in adult trees (RAT); and c) adult trees (AT). Starting from the center of each RST plot, and following the cardinal and subcardinal points, eight sites of 25 m2 and 0.1 ha were located to record the regeneration and adult tree species, respectively. Species richness indicators (Shannon-Wiener, Simpson, Pielou and Sorensen) were estimated to characterize the plots by community and were compared with t-tests and rarefaction analysis. Results and Discussion. Twelve species were recorded in the study area, of which 11 are found as a renewal of seed trees. Species richness in the RST plots with respect to that of AT was equal in the Cienega Grande, El Venado and La Colmena communities, and higher in Las Cienegas and Los Bajios. The Shannon-Wiener and Simpson indices were higher in Pino Gordo, Los Bajios and El Venado. The Sorensen index ranges from 0.67 to 1.0, indicating high species similarity among plots. Conclusions. The seed tree method in a mixed forest ensures the continuity of tree species diversity.

Clearcutting reduces proximity to seed sources and mycorrhizal inoculum potential for regenerating seedlings. Partial retention of legacy trees and protection of refuge plants, as well as preservation of the forest floor, can maintain mycorrhizal networks that colonize germinants and improve nutrient supply. However, little is known of overstory retention levels that best protect mycorrhizal inoculum while also providing sufficient light and soil resources for seedling establishment. To quantify the effect of tree retention on seedling regeneration, refuge plants, and resource availability, we compared five harvesting methods with increasing retention of overstory trees (clearcutting (0% retention), seed tree (10% retention), 30% patch retention, 60% patch retention, and 100% retention in uncut controls) in an interior Douglas-fir-dominated forest in British Columbia. Regeneration increased with proximity to legacy trees in partially cut forests, with increasing densities of interior Douglas-fir, western redcedar, grand fir, and western hemlock seedlings with overstory tree retention. Clearcutting reduced cover of ectomycorrhizal refuge plants (from 80 to 5%) while promoting arbuscular mycorrhizal plants the year after harvest. Richness of shrubs, herbs, and mosses declined with increasing harvesting intensity, but tree richness remained at control levels. The presence of legacy trees in all partially cut treatments mitigated these losses. Light availability declined with increasing overstory cover and proximity to leave trees, but it still exceeded 1,000 W m−2 in the clearcut, seed tree and 30% retention treatments. Increasing harvesting intensity reduced aboveground and belowground C stocks, particularly in live trees and the forest floor, although forest floor losses were also substantial where thinning took place in the 60% retention treatment. The loss of forest floor carbon, along with understory plant richness with intense harvesting was likely associated with a loss of ectomycorrhizal inoculum potential. This study suggests that dispersed retention of overstory trees where seed trees are spaced ~10–20 m apart, and aggregated retention where openings are

Since 1978 one of the legal silviculture systems in Indonesian regard to managing mangrove forest is seed tree method. The ability of this silviculture system to recruit the seeds to fulfill the regeneration is one of the importantaspects. The research is conducted to get the information about regeneration condition and the ability of seed tree method to recruit the regeneration in any various plot with different agecutting. Vegetation analysis for naturalregeneration (seedlings and saplings) were conducted at four different age logged-over area with the total 640 plots. The plot size is 78.5 m2. The result showed that existence of seed tree can affect the type of regeneration for seedlings recruitment with percentage between 59.52% to 83.37%.Key words: mangrove, natural regeneration, seed tree, seedling recruitment

Over the past century the size and severity of wildfires, as well as post-fire recovery processes (e.g., seedling establishment), have been altered from historical levels due to management policies and changing climate. Tree seedling establishment and growth drive future overstory tree dynamics after wildfire. Post-fire tree regeneration can be highly variable depending on burn severity, pre-fire forest condition, tree regeneration strategies, and climate, however, few studies have examined how different abiotic and biotic factors impact seedling density and growth and the interactions among those factors. We measured seedling density and height growth in the period 2015–2016 on three wildfires that burned in ponderosa pine (Pinus ponderosa) forests in the period 2000–2007 across broad environmental and burn severity gradients. Using a non-parametric multiplicative regression model, we found that downed woody fuel load, duff depth, and fall precipitation best explained variation in seedling density, while the distance to nearest seed tree, a soil productivity index, duff depth, and spring precipitation as snow best explained seedling height growth. Overall, results highlight the importance of burn severity and post-fire climate in tree regeneration, although the primary factors influencing seedling density and height growth vary. Drier conditions and changes to precipitation seasonality have the potential to influence tree establishment, survival, and growth in post-fire environments, which could lead to significant impacts for long-term forest recovery.

We studied the success of natural regeneration eight years after seed tree cutting on four drained peatland Scots pine stands in central and northern Finland (Parkano, Sievi, Vaala, Simo) when retaining ca. 50 Scots pine stems ha-1 followed by site preparation. The total number and the number of crop seedlings and their mean height were investigated by species and methods of site preparation (control, scalping, mounding). The results showed that the total seedling numbers were very high (9,100 – 51,000 ha-1) in all sites and treatments. The share of downy birch seedlings was 64 –76 %. The total number of crop seedlings varied from 1,450 to 2,000 ha-1 (2,000 maximum density accepted), with number of Scots pine seedlings varying from 600 in Parkano to 1,950 ha-1 in Sievi. Site preparation increased the number of pine crop seedlings on two of the four sites: at Parkano by 900 – 1,100 seedlings ha-1 and at Vaala by 600 – 800 seedlings ha-1. On average, the number of pine crop seedlings was slightly higher and that for all birch seedlings clearly higher when site preparation was applied. About 22 – 81% of crop seedlings were grown in a prepared surface in scalped plots and 75-91% on mounded plots. The mean height of the crop seedlings was not significantly affected by the site preparation treatment. With respect to the minimum requirements set for the regeneration result required by forest legislation, seed tree cutting appeared to provide sufficient regeneration in eight years in terms of the total seedling density and the number of crop seedlings when downy birches were included. The beneficial effect of soil preparation was seen in the increased share of Scots pine crop seedlings.

Exponential fertilization (EF) can feed seedlings with more nutrients than needed for growth and continuous lighting is expected to reduce the risk of loading at high application rate. In this study, red-seed tree (Ormosia hosiei Hemsley & E. H. Wilson) seedlings were raised by EF at a low rate of 160 mg nitrogen (N) plant-1 (conventional) (N-phosphorus [P]-potassium [K], 12-9-12) and a high rate of 600 mg N plant-1 (intensive), which was adapted from previous studies with large-pot-seedlings. Both fertilizer regimes were nested to either of two light spectra from high-pressure sodium (HPS) and light-emitting diode (LED) sources with three replicates for each combined treatment. Seedlings subjected to the conventional regime in the LED spectrum showed better growth and greater biomass accumulation with higher leaf N and P contents than other ones. In the conventional fertilizer regime, the LED spectrum also resulted in higher photosynthesis shown by more pigments and higher N synthesis than the HPS spectrum. The HPS spectrum strengthened P synthesis in the intensive regime. The antioxidative activity was stimulated by a high dose of EF, hence excessive toxicity was likely induced. We recommend using the normal rate of 160 mg N plant-1 for the culture of red-seed tree seedlings with LED lighting to promote seedling quality without causing excessive nutrient toxicity.

Coalescent histories provide lists of species tree branches on which gene tree coalescences can take place, and their enumerative properties assist in understanding the computational complexity of calculations central in the study of gene trees and species trees. Here, we solve an enumerative problem left open by Rosenberg ( IEEE/ACM Transactions on Computational Biology and Bioinformatics 10: 1253-1262, 2013) concerning the number of coalescent histories for gene trees and species trees with a matching labeled topology that belongs to a generic caterpillar-like family. By bringing a generating function approach to the study of coalescent histories, we prove that for any caterpillar-like family with seed tree $t$ , the sequence $(h_n)_{n\ge 0}$ describing the number of matching coalescent histories of the $n$ th tree of the family grows asymptotically as a constant multiple of the Catalan numbers. Thus, $h_n \sim \beta _t c_n$ , where the asymptotic constant $\beta _t > 0$ depends on the shape of the seed tree $t$ . The result extends a claim demonstrated only for seed trees with at most eight taxa to arbitrary seed trees, expanding the set of cases for which detailed enumerative properties of coalescent histories can be determined. We introduce a procedure that computes from $t$ the constant $\beta _t$ as well as the algebraic expression for the generating function of the sequence $(h_n)_{n\ge 0}$ .

To address the instability of phylogenetic trees in morphological datasets caused by missing values, we present a phylogenetic inference method based on a concept decision tree (CDT) in conjunction with attribute reduction. First, a reliable initial phylogenetic seed tree is created using a few species with relatively complete morphological information by using biologists&rsquo, prior knowledge or by applying existing tools such as MrBayes. Second, using a top-down data processing approach, we construct concept-sample templates by performing attribute reduction at each node in the initial phylogenetic seed tree. In this way, each node is turned into a decision point with multiple concept-sample templates, providing decision-making functions for grafting. Third, we apply a novel matching algorithm to evaluate the degree of similarity between the species&rsquo, attributes and their concept-sample templates and to determine the location of the species in the initial phylogenetic seed tree. In this manner, the phylogenetic tree is established step by step. We apply our algorithm to several datasets and compare it with the maximum parsimony, maximum likelihood, and Bayesian inference methods using the two evaluation criteria of accuracy and stability. The experimental results indicate that as the proportion of missing data increases, the accuracy of the CDT method remains at 86.5%, outperforming all other methods and producing a reliable phylogenetic tree.

La demanda de recursos forestales ha provocado la intensificación en el aprovechamiento de los bosques, y la necesidad de evaluar su efecto sobre las aves. El propósito del presente estudio fue evaluar la diversidad de aves en un bosque templado de producción forestal. Establecimos transectos y puntos de conteo intensivo en áreas representativas de los tratamientos silvícolas en el ejido Acolihuia, municipio de Chignahuapan, Puebla. Los tratamientos silvícolas que consideramos fueron cortas de aclareo, de liberación, de regeneración y de selección. Identificamos 35 especies de aves: 30 fueron residentes y 5 migratorias neotropicales. Cinco especies tienen alguna categoría de endemismo, y registramos a Myadestes occidentalis, sujeta a protección especial por la NOM-059- SEMARNAT-2010. La abundancia y riqueza de especies entre tratamientos silvícolas fue diferente. La mayor riqueza y diversidad alfa la registramos en áreas manejadas por el método de desarrollo silvícola. La similitud de especies entre tratamientos es baja o intermedia, lo que sugiere que las especies pueden conservarse durante la rotación de los tratamientos. En un escenario de deforestación persistente y requerimiento creciente de productos forestales, el fomento al manejo forestal sustentable puede contribuir a la conservación de la diversidad de aves.

We studied the genetic impact of natural regeneration practices, such as Single seed tree, Group seed tree, Patch clear cutting and Alternate strip clear cutting systems, by comparing the nuclear microsatellite(nSSR) variation of post-practice natural regeneration one-year old seedlings of Pinus densiflora to that of pre-practice mature trees. The levels of genetic diversity of seedlings (A=13.6, =4.3, =0.571, =0.597) were similar to those of mature trees (A=13.4, =4.3, =0.596, =0.598) and the differences in the level of genetic diversity between seedlings and mature trees for each of the practices were not statistically significant. The degree of genetic differentiation between seedlings and mature trees was very low (=0.002) and the pairwise values between seedlings and mature trees for all practices were less than 0.01. Overall, the natural regeneration practices appeared to have only minor impacts on the genetic diversity and the genetic composition in the studied P. densiflora stands. For a better understanding of the genetic effects of natural regeneration practices, subsequent studies such as temporal genetic variation of seedlings formed by crossing among post-practice mature trees should be considered.

We studied the establishment of natural seedlings after seed tree cutting and scalping in two drained Scots pine peatland stands in northern Finland (Simo and Sievi). Approximately, 50 ha−1 of Scots pine stems were retained on both sites. During the six subsequent years, five seedling surveys were conducted. The effect of site preparation was analysed using generalized linear mixed models (GLMM). The mean density of pine seedlings increased more quickly in the scalped plots and was ca. 1.1 m−2 after six years compared to 0.87 m−2 in the non-scalped plots, on average. Scalping increased the number of pine seedlings 2-fold compared to that in non-treated plots in Simo, however, in Sievi non-treated plots had 30% higher pine seedling density after six years. Downy birch seedling density was 9–10-fold compared to that of non-treated plots in both sites. In terms of seedling density, seed tree cutting led to satisfactory pine regeneration after just two growing seasons in drained pine peatlands, even w...

Forest regeneration is a key element in achieving sustainable forest management. Partial harvest methods have been used extensively in temperate broadleaf and mixedwood ecosystems to promote regeneration on poorly stocked sites and to maintain forest composition and productivity. However, their effectiveness in promoting conifer establishment has yet to be demonstrated in unmanaged boreal forests, especially those dominated by black spruce (Picea mariana (Mill.) BSP) where constraints for regeneration differ from those found in more meridional regions. We aimed to evaluate conifer seedling density and dimensions, 10 years after the onset of a gradient of silvicultural treatments varying in harvesting intensities, and to identify the critical factors driving the regeneration process. Study blocks of even-aged black spruce stands in the eastern Canadian boreal forest were submitted to three variants of shelterwood harvesting: a seed-tree harvest, a clear-cut and an untreated control. Shelterwood and seed-tree harvesting were combined with spot scarification to promote regeneration. Shelterwood and seed-tree harvesting produced a density of conifer regeneration sufficient to maintain forest productivity, but they did not promote seedling growth. Black spruce was the predominant species in terms of regeneration density, with proportions 3–5× higher than that for balsam fir (Abies balsamea (L.) Mill.). Ten years after treatment, seed-origin black spruce seedlings were abundant in skidding trails, while layers dominated the residual strips. Balsam fir density was not influenced by treatment nor by tree position relative to skidding trails. Balsam fir and black spruce had different responses to treatment in terms of height and diameter, the former exhibiting a better growth performance and larger diameter in the residual strips. Spot scarification created micro-sites that had a significant impact on the regeneration process. Overall, our results support that shelterwood and seed-tree harvesting combined with scarification enable adequate regeneration in black spruce stands, confirming these treatments as viable silvicultural alternatives to clear-cutting when required by sustainable forest management objectives.

The productivity value of six new Prunus persica genotypes - BN-1, BN-3, BN-4, BN-7, BN-8 and BN-45 for the seedling rootstock production for cultivated peach varieties was investigated. The control seedling varieties were P. persica ‘Mandzurska’ and P. persica ‘Siberian C’. All investigated trees were grown in the Experimental Orchard in Dąbrowice (Central Poland) of the Research Institute of Horticulture. Intensity of flowering and fruiting was evaluated as well as date of fruit ripening, size of fruits and their seeds (stones) including ability to germinate in relation to the age of the seeds (freshly harvested vs stored). The best (highest) yield was collected from trees of genotypes BN-1, BN-4 and BN-8. All of the new tree genotypes were producing smaller fruits and seeds with higher germination capacity compared to control trees. In terms of the characteristics assessed, the best as a seed source tree was genotypes BN-7 and BN-8. The trees of genotypes BN-1, BN-3 and BN-4 were very much comparable to control seedling varieties in terms of fruiting intensity of trees, number of stones obtained from the fruit yield and number of stones contained in 1 kg of their weight. This indicates tremendous usefulness of the evaluated new genotypes for sourcing seeds necessary for the production of rootstocks for peach varieties. They can be used in cultivation of peach not only in Poland but also in countries located in a cooler areas of the moderate climate.

Brazil nut tree is a species of economic importance for the Amazon region, known for the commercialization of its almonds. The objective of this work was to study the genetic diversity among half-sib progenies from different Brazil nut trees present in native forest in the municipality of Itauba, MT, belonging to the Brazilian Amazon. In a native forest area of nine hectares, fruits of nine parent trees, randomly selected in the plot, were collected. The seeds were planted at greenhouse and they were named, according to their origin, identifying seed tree and fruit. After the seed germination and initial development of the seedlings, leaves were collected for DNA extraction and analyzed with microsatellite molecular markers. It was performed analysis of molecular variance and cluster analysis of progenies and seed trees. There is greater genetic diversity between families than among progenies from the same family. The clustering of progenies from different families in the same group can be explained by the low dissimilarity between the seed trees. Among the loci analyzed in this study, eight were informative for evaluations of genetic diversity in Brazil nut, except BET12 and BET16 loci

Due to fire suppression policies, timber harvest, and other management practices over the last century, many low‐ to mid‐elevation forests in semiarid parts of the western United States have accumulated high fuel loads and dense, multi‐layered canopies that are dominated by shade‐tolerant and fire‐sensitive conifers. To a great extent, the future status of western US forests will depend on tree species’ responses to patterns and trends in fire activity and fire behavior and postfire management decisions. This is especially the case in the North American Mediterranean‐climate zone (NAMCZ), which supports the highest precipitation variability in North America and a 4‐ to 6‐month annual drought, and has seen greater‐than‐average increases in air temperature and fire activity over the last three decades. We established 1490 survey plots in 14 burned areas on 10 National Forests across a range of elevations, forest types, and fire severities in the central and northern NAMCZ to provide insight into factors that promote natural tree regeneration after wildfires and the differences in postfire responses of the most common conifer species. We measured site characteristics, seedling densities, woody shrub, and tree growth. We specified a zero‐inflated negative binomial mixed model with random effects to understand the importance of each measured variable in predicting conifer regeneration. Across all fires, 43% of all plots had no conifer regeneration. Ten of the 14 fires had median conifer seedling densities that did not meet Forest Service stocking density thresholds for mixed conifer forests. When regeneration did occur, it was dominated by shade‐tolerant but fire‐sensitive firs (Abies spp.), Douglas‐fir (Pseudotsuga menziesii) and incense cedar (Calocedrus decurrens). Seedling densities of conifer species were lowest in sites that burned at high severity, principally due to the biotic consequences of high severity fire, for example, increased distances to live seed trees and competition with fire‐following shrubs. We developed a second model specifically for forest managers and restoration practitioners who work in yellow pine and mixed conifer forests in the central NAMCZ to assess potential natural regeneration in the years immediately following a fire, allowing them to prioritize which areas may need active postfire forest restoration and supplemental planting.

Given a gene tree and a species tree, ancestral configurations represent the combinatorially distinct sets of gene lineages that can reach a given node of the species tree. They have been introduced as a data structure for use in the recursive computation of the conditional probability under the multispecies coalescent model of a gene tree topology given a species tree, the cost of this computation being affected by the number of ancestral configurations of the gene tree in the species tree. For matching gene trees and species trees, we obtain enumerative results on ancestral configurations. We study ancestral configurations in balanced and unbalanced families of trees determined by a given seed tree, showing that for seed trees with more than one taxon, the number of ancestral configurations increases for both families exponentially in the number of taxa n. For fixed n, the maximal number of ancestral configurations tabulated at the species tree root node and the largest number of labeled histories possible for a labeled topology occur for trees with precisely the same unlabeled shape. For ancestral configurations at the root, the maximum increases with \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $$ k_0^n$$ \end{document}, where \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $${{k_0}} \approx \bf1.5028$$ \end{document} is a quadratic recurrence constant. Under a uniform distribution over the set of labeled trees of given size, the mean number of root ancestral configurations grows with \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $$\sqrt {\bf 3 / 2} { {\bf ( 4 / 3 ) ^n}}$$ \end{document} and the variance with ∼\documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $${{\bf 1.4048 ( 1.8215 )} ^n}$$ \end{document}. The results provide a contribution to the combinatorial study of gene trees and species trees.

Partial cutting is thought to be an alternative to achieve sustainable management in boreal forests. However, the effects of intermediate harvest intensity (45%–80%) on growth remain unknown in black spruce (Picea mariana (Mill.) B.S.P.) stands, one of the most widely distributed boreal species with great commercial interest. In this study, we analysed the effect of three experimental shelterwood and one seed-tree treatments on tree radial growth in even-aged black spruce stands, 10 years after intervention. Our results show that radial growth response 8–10 years after cutting was 41% to 62% higher than in untreated plots, with stand structure, treatment, tree position relative to skidding trails, growth before cutting and time having significant interactions. The stand structure conditioned tree growth after cutting, being doubled in younger and denser stands. Tree spatial position had a pronounced effect on radial growth; trees at the edge of the skidding trails showed twice the increase in growth compared to interior trees. Dominant trees before cutting located close to the skidding trails manifested the highest growth response after cutting. This research suggests that the studied treatments are effective to enhance radial wood production of black spruce especially in younger stands, and that the edge effect must be considered in silvicultural management planning.

Artificial pollination of black walnut (Juglans nigra L.) is not practical and timber breeders have historically utilized only open-pollinated half-sib families. An alternate approach called "breeding without breeding," consists of genotyping open-pollinated progeny using DNA markers to identify paternal parents and then constructing full-sib families. In 2014, we used 12 SSR markers to genotype 884 open-pollinated half-sib progeny harvested from two clonal orchards containing 206 trees, comprised of 52 elite timber selections. Seed was harvested in 2011 from each of two ramets of 23 clones, one upwind and one downwind, based on prevailing wind direction from the west-southwest. One orchard was isolated from wild black walnut and composed of forward selections while the other orchard was adjacent to a natural forest containing mature black walnut composed of backward selections. Isolation significantly increased within-orchard pollination (85%) of the progeny from the isolated orchard compared to 42% from the non-isolated orchard. Neither prevailing wind direction nor seed tree position in the orchard affected paternity patterns or wild pollen contamination. Genetic diversity indices revealed that progeny from both orchards were in Hardy-Weinberg equilibrium with very little inbreeding and no selfing. A significant level of inbreeding was present among the forward selected parents, but not the first generation (backward selected) parents. Some orchard clones failed to sire any progeny while other clones pollinated upwards of 20% of progeny.

Pollen and seed dispersal are key processes affecting the demographic and evolutionary dynamics of plant species and are also important considerations for the sustainable management of timber trees. Through direct and indirect genetic analyses, we studied the mating system and the extent of pollen and seed dispersal in an economically important timber species, Entandrophragma cylindricum (Meliaceae). We genotyped adult trees, seeds and saplings from a 400-ha study plot in a natural forest from East Cameroon using eight nuclear microsatellite markers. The species is mainly outcrossed (t = 0.92), but seeds from the same fruit are often pollinated by the same father (correlated paternity, rp = 0.77). An average of 4.76 effective pollen donors (Nep ) per seed tree contributes to the pollination. Seed dispersal was as extensive as pollen dispersal, with a mean dispersal distance in the study plot approaching 600 m, and immigration rates from outside the plot to the central part of the plot reaching 40% for both pollen and seeds. Extensive pollen- and seed-mediated gene flow is further supported by the weak, fine-scale spatial genetic structure (Sp statistic = 0.0058), corresponding to historical gene dispersal distances (σg ) reaching approximately 1,500 m. Using an original approach, we showed that the relatedness between mating individuals (Fij = 0.06) was higher than expected by chance, given the extent of pollen dispersal distances (expected Fij = 0.02 according to simulations). This remarkable pattern of assortative mating could be a phenomenon of potentially consequential evolutionary and management significance that deserves to be studied in other plant populations.