Search

Tree search algorithms, such as branch-and-bound, are the most widely used tools for solving combinatorial and non-convex problems. For example, they are the foremost method for solving (mixed) integer programs and constraint satisfaction problems. Tree search algorithms come with a variety of tunable parameters that are notoriously challenging to tune by hand. A growing body of research has demonstrated the power of using a data-driven approach to automatically optimize the parameters of tree search algorithms. These techniques use a training set of integer programs sampled from an application-specific instance distribution to find a parameter setting that has strong average performance over the training set. However, with too few samples, a parameter setting may have strong average performance on the training set but poor expected performance on future integer programs from the same application. Our main contribution is to provide the first sample complexity guarantees for tree search parameter tuning. These guarantees bound the number of samples sufficient to ensure that the average performance of tree search over the samples nearly matches its future expected performance on the unknown instance distribution. In particular, the parameters we analyze weight scoring rules used for variable selection. Proving these guarantees is challenging because tree size is a volatile function of these parameters: we prove that, for any discretization (uniform or not) of the parameter space, there exists a distribution over integer programs such that every parameter setting in the discretization results in a tree with exponential expected size, yet there exist parameter settings between the discretized points that result in trees of constant size. In addition, we provide data-dependent guarantees that depend on the volatility of these tree-size functions: our guarantees improve if the tree-size functions can be well approximated by simpler functions. Finally, via experiments, we illustrate that learning an optimal weighting of scoring rules reduces tree size. [ABSTRACT FROM AUTHOR]

Summary: Stem respiration constitutes a substantial proportion of autotrophic respiration in forested ecosystems, but its drivers across different spatial scales and land‐use gradients remain poorly understood. This study quantifies and examines the impact of logging disturbance on stem CO2 efflux (EA) in Malaysian Borneo.EA was quantified at tree‐ and stand‐level in nine 1‐ha plots over a logging gradient from heavily logged to old‐growth using the static chamber method.Tree‐level results showed higher EA per unit stem area in logged vs old‐growth plots (37.0 ± 1.1 vs 26.92 ± 1.14 g C m−2 month−1). However, at stand‐level, there was no difference in EA between logged and old‐growth plots (6.7 ± 1.1 vs 6.0 ± 0.7 Mg C ha−1 yr−1) due to greater stem surface area in old‐growth plots. Allocation to growth respiration and carbon use efficiency was significantly higher in logged plots. Variation in EA at both tree‐ and stand‐level was driven by tree size, growth and differences in investment strategies between the forest types.These results reflect different resource allocation strategies and priorities, with a priority for growth in response to increased light availability in logged plots, while old‐growth plots prioritise maintenance and cell structure. [ABSTRACT FROM AUTHOR]

The results of the studies devoted to the consequences of the Kakhovka dam destruction on June 6, 2023 in the course of the Russia-Ukraine war are presented. After the accident, the Kakhovske reservoir, which was the largest by volume on the Dnipro River, practically disappeared. It has turned into the network of river branches and lakes that do not compare with the former reservoir. Currently, the conditions on the territory of the former reservoir have approached those observed in natural conditions. To some extent, they depend on the water discharge of the Dnipro River, more exactly, on the water discharge of the Dnipro HPP located upstream. In the conditions of large water runoff, the large part of the former Kakhovske reservoir is covered with water. An unusual natural phenomenon of the area of the former reservoir is very rapid overgrowth, primarily by willow. A year after the accident, its height in places which is rich in organic sediments exceeded 4 meters. At the same time, the size of the trees on the bottom covered by sands is much smaller. Today, a large area of the former reservoir looks like a dense forest. [ABSTRACT FROM AUTHOR]

Aim: We test the hypothesis that wind dispersal is more common among emergent tree species given that being tall increases the likelihood of effective seed dispersal. Location: Americas, Africa and the Asia‐Pacific. Time period: 1970–2020. Major taxa studied: Gymnosperms and Angiosperms. Methods: We used a dataset consisting of tree inventories from 2821 plots across three biogeographic regions (Americas, Africa and Asia‐Pacific), including dry and wet forests, to determine the maximum height and dispersal strategy of 5314 tree species. A web search was used to determine whether species were wind‐dispersed. We compared differences in tree species maximum height between biogeographic regions and examined the relationship between species maximum height and wind dispersal using logistic regression. We also tested whether emergent tree species, that is species with at least one individual taller than the 95% height percentile in one or more plots, were disproportionally wind‐dispersed in dry and wet forests within each biogeographic region. Results: Our dataset provides maximum height values for 5314 tree species, of which more than half (2914) had no record of this trait in existing global databases. We found that, on average, tree species in the Americas have lower maximum heights compared to those in Africa and the Asia Pacific. The probability of wind dispersal increased significantly with tree species maximum height and was significantly higher among emergent than non‐emergent tree species in both dry and wet forests in all three biogeographic regions. Main conclusion: Wind dispersal is more prevalent in tall, emergent tree species than in non‐emergent species and may thus be an important factor in the evolution of tree species maximum height. By providing the most comprehensive dataset so far of tree species maximum height and wind dispersal strategies, this study paves the way for advancing our understanding of the eco‐evolutionary drivers of tree size. [ABSTRACT FROM AUTHOR]

Individual modelling is a foundational approach to study the natural forest growth and in this paper, we develop a serial distance-depended individual tree model for some species in natural forest which would provide prediction and characteristics for natural species. The data used to develop individual model for natural mixed forests were collected from 712 remeasured 10-year periodic permanent sample plots of in Baihe Forest Bureau of Changbai Mountains, northeast China. Based on analyzing relationship between diameter increment of individual trees with tree size, competitive status, and site condition and finding out the major independent variables, the growth models for individual trees of 15 species in the natural mixed forests, that have good predicting precision, and easily applicable, were developed using stepwise regression method. The individual growth model developed in this study can reflect the tree increment of 15 species and be generally well suited for simulating tree and stand growth for natural mixed forests in Changbai Mountains. The research results for individual trees growth model of each species showed that main variable to influence on diameter increment of individual trees for natural mixed forests were tree size (D) and then competition index. The site condition was not related with diameter increment. The natural logarithm of DBH (lnD) and square diameter (D2) were included in the predicting models of diameter increment for all 15 species. The diameter increment was directly proportional to tree diameter for each species. For the competitive indexes in growth model, the relative diameter (RD), canopy closure (P), and the ratio of diameter of subject tree with maximum diameter (DDM) were related to diameter increment and the stand density measures were not significantly influenced on diameter increment. As canopy closure increase, tree increment decreases. The site conditions were performance less of factors in increment predictions in the model. [ABSTRACT FROM AUTHOR]

Background: Plants allocate resources to growth, defense, and stress resistance, and resource availability can affect the balance between these allocations. Allocation patterns are well-known to differ among species, but what controls possible intra-specific trade-offs and if variation in growth vs. defense potentially evolves in adaptation to resource availability. Methods: We measured growth and defense in a provenance trial of rubber trees (Hevea brasiliensis) with clones originating from the Amazon basin. To test hypotheses on the allocation to growth vs. defense, we relate biomass growth and latex production to wood and leaf traits, to climate and soil variables from the location of origin, and to the genetic relatedness of the Hevea clones. Results: Contrary to expectations, there was no trade-off between growth and defense, but latex yield and biomass growth were positively correlated, and both increased with tree size. The absence of a trade-off may be attributed to the high resource availability in a plantation, allowing trees to allocate resources to both growth and defense. Growth was weakly correlated with leaf traits, such as leaf mass per area, intrinsic water use efficiency, and leaf nitrogen content, but the relative investment in growth vs. defense was not associated with specific traits or environmental variables. Wood and leaf traits showed clinal correlations to the rainfall and soil variables of the places of origin. These traits exhibited strong phylogenetic signals, highlighting the role of genetic factors in trait variation and adaptation. The study provides insights into the interplay between resource allocation, environmental adaptations, and genetic factors in trees. However, the underlying drivers for the high variation of latex production in one of the commercially most important tree species remains unexplained. [ABSTRACT FROM AUTHOR]

In forests, a significant proportion of the carbon fixed by trees during photosynthesis is transported belowground along the conducting phloem, so variations in phloem anatomy can lead to variations in transport capacity. Phloem conductance at tree level (Ktree) is also affected by tree height. Both the phloem anatomy and the tree size change during ontogeny, and also differ under different environmental conditions. The goal of our work was to identify the main drivers of variation in Ktree in Scots pine trees growing in natural boreal forests. We conducted a phloem anatomical study and calculated Ktree in trees of three age groups growing in different climatic conditions along a latitudinal gradient from south to north. We found that Ktree was maintained at the same level in actively growing pine trees (25–80-years-old) but increased in old-aged trees (180–190-years-old), possibly reflecting the shift in source-sink relationships of aboveground and belowground parts of trees. Trees of the same age group growing in different climatic conditions demonstrated similar values of Ktree due to coordinated changes in the phloem anatomy and the tree height. In general, the negative influence of tree height on Ktree is offset by the positive influence of phloem width (or trunk diameter) and sieve cell diameter. The exception was young trees growing in the transition zone of the northern taiga subzone to the tundra, where Ktree was the highest in its age group and even exceeded Ktree of middle-aged trees. [ABSTRACT FROM AUTHOR]

Depending on the strength of the relationship between biodiversity and aboveground biomass (AGB), diversity loss could lead to varied declines in carbon storage, compromising the role of forests as carbon sink. This study assesses different factors affecting the diversity–AGB relationship, including small trees (diameter < 7.5 cm) and considering different diversity metrics (Hill numbers), plot sizes (80, 400 and 1000 m2) and successional age categories (8–22, 23–30 and > 60 years). The study compares these relationships across three types of tropical dry forests: deciduous, semi-deciduous, and semi-evergreen. Results reveal the highest deviance values in plots with large trees in the 400 m2 size (d2 = 40.4), decreasing when small trees were included (d2 = 25.8). Higher deviance values show the major contribution of large trees to diversity and AGB of 400 m2 plots, while lower deviance values indicate the high contribution of small trees to diversity but limited contribution to AGB. When analyzing only large trees, deviance decreased with the order of Hill numbers. However, incorporating small trees increased deviance for higher Hill numbers. This is because abundance of small and large trees together has a greater influence on AGB. The diversity–AGB relationship was more prevalent and stronger in the semideciduous forest, which had marked orographic and successional age variation. The strongest diversity–AGB effect occurred in early successional ages, weakening in older stages. Our results show that accuracy in estimating the diversity–AGB relationship varies with plant size, diversity parameters, plot size and forest type. [ABSTRACT FROM AUTHOR]

Galton-Watson forests consisting of N rooted trees and n non-root vertices are considered. The distribution of the forest is determined by that of critical branching process with infinite variance and regularly varying tail of the progeny distribution. We prove limit theorem for the maximal size of a tree in a forest as N, n → ∞ in such a way that n/N → ∞. Our conditions are significantly wider than was previously known. [ABSTRACT FROM AUTHOR]

Due to the importance of trees in urban ecosystems, it is crucial to understand the distribution, prevalence, and intensity of parasitic mistletoe infection across urban landscapes. In this study, we aimed to understand how various tree-related factors (e.g., tree taxonomy, size, pruning history, nativity, foliage, density, and diversity) might influence mistletoe prevalence and infection intensity across a typical subtropical urban greenspace. We surveyed 6,012 trees representing 96 species, 76 genera, and 44 families across a large, urban university campus in a major Southwest Chinese city. In total, we found 353 mistletoe host trees (prevalence: 5.87%), largely concentrated on the eastern part of campus, partially due to the proximity of waterbodies and a large adjacent greenspace, as well as higher tree density. To understand how predictors affected the prevalence and intensity of mistletoe infection, we used a hurdle model fitting our zero-inflated count data. Four independent variables significantly affected the prevalence of mistletoe infestation, with three demonstrating positive correlations (crown width, tree density, and tree diversity). One variable (evergreen foliage) negatively correlated with mistletoe prevalence. However, only one factor was found to significantly affect mistletoe infection intensity (crown width, positively). Due to the variety of ecosystem services mistletoes provide, more studies are necessary to assess the impact of various mistletoe management strategies, especially on urban biodiversity. Highlights: Of 6,012 surveyed trees, 353 hosted mistletoes, but 50 of 96 species did not. Four tree-related factors affected mistletoe prevalence (3 positively/1 negatively). Only tree size (positively) affected infection intensity. [ABSTRACT FROM AUTHOR]

Simple Summary: Spatial patterns are characteristics of spatial processes, although they do not always match each other exactly. An ordinary way to explore the spatial progresses driving these spatial patterns is spatial pattern analysis, which has been widely employed in ecology studies but not in the studies of forest diseases. For diseased forest trees, the spatial pattern is a complex of the spatial pattern of forest trees and the disease itself. So, it is necessary to explore whether an antecedent pattern of host/nonhost trees affects the spatial pattern of a forest disease. Another subject that is neglected is the effect size of an antecedent pattern. In this study, taking a stem fungal disease caused by Inonotus hispidus as an example, we explored the two questions. Our results showed that the spatial pattern of host size affected the spatial pattern of the infection and the infection likelihood of the focal tree. Our results provide a new perspective to understand the effect of host patterns on forest disease. The spatial pattern of diseased forest trees is a product of the spatial pattern of host trees and the disease itself. Previous studies have focused on describing the spatial pattern of diseased host trees, and it remains largely unknown whether an antecedent spatial pattern of host/nonhost trees affects the infection pattern of a disease and how large the effect sizes of the spatial pattern of host/nonhost trees and host size are. The results from trivariate random labeling showed that the antecedent pattern of the host ash tree, Fraxinus mandshurica, but not of nonhost tree species, impacted the infection pattern of a stem fungal disease caused by Inonotus hispidus. To investigate the effect size of the spatial pattern of ash trees, we employed the SADIE (Spatial Analysis by Distance IndicEs) aggregation index and clustering index as predictors in the GLMs. Globally, the spatial pattern (vi index) of ash trees did not affect the infection likelihood of the focal tree; however, the spatial pattern of DBH (diameter at breast height) of ash trees significantly affected the infection likelihood of the focal tree. We sampled a series of circular plots with different radii to investigate the spatial pattern effect of host size on the infection likelihood of the focal tree locally. The results showed that the location (patch/gap) of the DBH of the focal tree, rather than that of the focal tree itself, significantly affected its infection likelihood in most plots of the investigated sizes. A meta-analysis was employed to settle the discrepancy between plots of different sizes, which led to results consistent with those of global studies. The results from meta-regression showed that plot size had no significant effects. [ABSTRACT FROM AUTHOR]

Tropical forests continue to face deforestation in countries such as the Philippines. To look at the long-term behavior of forests in response to intrinsic and extrinsic factors, continual monitoring of forest dynamics is needed. To do this, we established a 2-ha permanent tropical forest plot in a low-disturbance area in Maluyon, Philippines. We addressed three main questions: 1) How does the plot change through time? 2) How do different species in the plot change through time? 3) Would the responses differ by tree size? We measured, mapped, and identified all trees >1 cm in diameter in 2011. In 2015, we re-measured surviving trees and measured, mapped, and identified recruits. A total of 177 tree species were found in the plot. The forest exhibited a mean growth rate of 0.054 cm/year, mortality rate of 0.011%/year, and recruitment rate of 0.019%/year. Overall growth and mortality rates were lower in Maluyon than in other plots, possibly due to the forest’s high tree density and low disturbance. Species-specific rates revealed the presence of both the growth-survival and the stature-recruitment trade-offs. Size class analysis showed higher growth rates in large-sized than in small-sized trees. In contrast, small-sized trees exhibited a higher mortality rate compared to large-sized trees, likely due to density dependence. Key findings of the study may be utilized to increase the success rate of restoration efforts in this watershed. Using a mix of fast-growing, generalist species with high survival rates (e.g., Allophyllus cobbe and Anisoptera thurifera) is highly recommended.

Currently, mistblowers are the most common sprayer type used for pesticide application in orchards. However, maximizing canopy deposition with high application efficiency remained a challenge due to the intricate canopy structure. This study compares the performance of two air-conveyor sprayers on pear trees: a conventional sprayer and an optimized sprayer. The optimized sprayer was equipped with a spray controller that displays its operational conditions (forward speed, spraying pressure, etc.) during application through a user interface of the device. In addition, the controller was capable of recommending spray volume for an orchard with the operator's inputs based on the Tree Row Volume (TRV) method. Two experimental blocks in two pear orchards, with different tree sizes referred to as 'small trees' and 'large trees', were designated to evaluate the foliage deposition and off-target losses of the two sprayers. The conventional sprayer applied a spray volume of 1160 L ha-1 on both orchards following the farmers' conventional procedure. In contrast, the spray volumes of the optimized sprayer were determined by the controller based on the TRV model, resulting in a reduction of 29% and 55% for the large and small pear trees, respectively. The foliar deposition of each block was sampled from five randomly selected trees in a central row, with leaves collected from nine different canopy positions for small trees and twelve positions for large trees. Petri dishes were placed on the ground to assess the ground losses. Poles with nylon threads were mounted at various positions to evaluate airborne drift. The results showed that the mean normalized foliar depositions of the optimized sprayer were 1.57 and 1.81 µg cm-2 / kg-1 tracer ha-1 for large and small trees, respectively, whereas with the conventional sprayer, the depositions were 0.85 and 2.11 µg cm-2 / kg-1 tracer ha-1 for large and small trees, respectively. The optimized sprayer achieved a more uniform deposition distribution throughout the canopy compared to the conventional sprayer, as no significant differences in foliage deposition were detected between positions with the optimized sprayer. The optimized sprayer was capable of providing higher normalized deposits than the conventional sprayer for the large trees with less application volume. In addition, the optimized sprayer reduced spray losses in the air by 10% and 64% compared to the conventional sprayer for small and large trees, respectively, whereas ground losses were diminished by 45% and 50%, respectively. The results of this study suggest that controlling sprayer parameters, along with the spray volume adjustment based on canopy characteristics, may increase foliar deposition and could reduce pesticide use, although its influences on off-target loss reduction were insignificant. [ABSTRACT FROM AUTHOR]

There is considerable interest in identifying and locating natural forests as accurately as possible, because they are deemed essential in preventing biodiversity loss. In the boreal region, natural forests contain a substantial amount of dead wood and exhibit considerable variation in tree age, size, and species composition. However, it is difficult to define natural forests in a quantitative manner. This is an issue, for example, in the Finnish national forest inventory. If naturalness could be related to the metrics derived from tree measurements, it would be easier to locate natural forests based on the inventory data. In this study, we investigated the value of metrics computed from tree locations and tree sizes for the characterization of a key aspect of naturalness, namely, structural naturalness as defined in the Finnish national forest inventory. We used L-moments, Gini coefficient, Lorenz asymmetry, and interquartile range to quantify the variations in tree size at the plot level. We summarized the spatial pattern of trees with a spatial aggregation index. We compared the structural metrics, species proportions, and stand age using the classes of structural naturalness described in the Finnish national forest inventory, which have been determined in the field without strict numerical rules. These categories are 'natural', 'near-natural', and 'non-natural'. We found that the forests evaluated as structurally natural had larger variations in tree size and species composition and showed a more clustered spatial pattern of trees on average, although the variation in the structural metrics was considerable in all three classes. In addition, we used the structural metrics to predict naturalness by employing a random forest algorithm. Based on the structural metrics, it was possible to obtain high precision in the classification only if we simultaneously accepted low recall, and vice versa; the link between the inspected metrics and naturalness evaluated in the field was weak. The stand age separated the three classes more clearly and it also improved the classification. [ABSTRACT FROM AUTHOR]

Large tree decline is occurring globally with critical implications for biodiversity and carbon sequestration. Restoration thinning is a potential management action to accelerate tree growth and promote large tree development in forests, yet trials have been limited and results have been mixed.We conducted a large‐scale trial to determine whether restoration thinning could accelerate the development of large trees in river red gum forests in Australia that had experienced widespread woody thickening and a decline of large trees due to long‐term commercial timber harvesting and river regulation.Thinning was conducted on 44 9‐ha plots by removing trees <40 cm diameter from around retained trees at a range of spacings. Initial tree densities ranged from ~260 to ~1860 trees per ha and 8%–86% of trees were removed by thinning. We monitored 1980 trees prior to thinning, and annually for 5 years post‐thinning. We tested the effects of thinning intensity on diameter growth of different sized trees and explored whether long‐ and short‐term water availability affected outcomes.Thinning promoted the growth of small trees <56 cm diameter, especially in drier sites during wet years. Higher thinning intensities reduced the growth rates of large trees (no smaller than 79.5 cm diameter) in wetter sites.For medium‐ and large‐sized trees, long‐ and short‐term water availability were stronger drivers of tree growth than competition due to tree density.Synthesis and applications. Restoration thinning may accelerate tree growth in young river red gum forests where all trees are small. But restoration thinning may be ineffective or detrimental in multi‐aged forests where the goal is to promote the growth rates of trees that are already medium to large in size. [ABSTRACT FROM AUTHOR]

To maintain the ecosystem resilience to large-scale disturbances in managed forests, it is essential to adhere to the principles of close-to-nature silviculture, adapt practices to the traits of natural forest types, and utilize natural processes, including natural regeneration. This study examines the natural regeneration patterns in silver fir (Abies alba Mill.)-dominated forests, analyzing how the stand structure—tree size diversity, species composition, and stand density—affects the regeneration. We analyze the data from four sites in Poland, Germany, and Italy, employing generalized linear and zero-inflated models to evaluate the impact of the management strategies (even- vs. uneven-aged) and forester-controlled stand characteristics (structural diversity, broadleaf species admixture, and stand density) on the probability of regeneration, its density, and the developmental stages (seedling, small sapling, and tall sapling) across a climatic gradient. Our results indicate a significantly higher probability of regeneration in uneven-aged stands, particularly in areas with lower temperatures and lower overall regeneration density. The tree size diversity in the uneven-aged stands favors advancement from juveniles to more developed stages (seedling to sapling) in places with higher aridity. A denser stand layer (higher stand total basal area) leads to a lower density of natural regeneration for all the present species, except silver fir if considered separately, signifying that, by regulating the stand growing stock, we can selectively promote silver fir. A higher admixture of broadleaf species generally decreases the regeneration density across all the species, except in a water-rich site in the Bavarian Alps, where it had a strong positive impact. These findings underscore the complex interactions of forest ecosystems and provide a better understanding required for promoting silver fir regeneration, which is essential for a close-to-nature silviculture under climate change. [ABSTRACT FROM AUTHOR]

The phenomenon of divergent responses in tree ring radial growth to climate change has been observed in the mid- and high-latitude regions of the Northern Hemisphere amidst global warming. However, the stability of the responses of the primary conifer species to climate factors in the mountainous regions of northeastern China remains unclear. Additionally, it is uncertain whether the radial growth in this area consistently responds to different competition indices. In our study, we developed tree ring width chronologies for Dahurian larch (Larix gmelinii) and analysed the radial growth responses to the regional climate from 1980 to 2012. This analysis was conducted by correlating meteorological data from different physiological stages of trees. We also evaluated the reliability of competition indices in predicting tree growth by constructing multiple linear regression models. Furthermore, we explored the relationship between the Basal Area Increment (BAI) of each tree and the competition indices in the sample plot over the previous five years. Our results showed that the temperature during the Non-Structural Carbohydrate (NSC) accumulation period and the NSC consumption period was significantly negatively correlated with the Ring Width Index (RWI) of Dahurian larch. Conversely, the RWI was significantly positively correlated with precipitation during these periods. The Standardised Precipitation Evapotranspiration Index (SPEI) at any period had a significantly positive correlation with the RWI. These findings suggest that future radial growth is likely to continue to be constrained by rising temperatures and water scarcity. Our findings also demonstrated that radial growth was less negatively impacted by competition from nearby trees and more influenced by the initial size of the tree. Compared to models that included other indices, models that included the BAL index as a single explanatory variable demonstrated superior statistical effectiveness. Our research suggests that before evaluating the competitive effects of the neighbourhood on radial growth, it is necessary to consider the stand diversity of tree species and the parameters related to spatial structure when selecting an appropriate competition index. [ABSTRACT FROM AUTHOR]

Masson pine (Pinus massoniana Lamb.) is a tree species that is widely distributed throughout southern China and holds significant economic and ecological value. The main objective of our study was to assess the effects of thinning on aboveground biomass increments and tree diversity in both the overstory and understory. Additionally, the underlying factors and mechanisms responsible for driving changes in biomass increment were analyzed. Four different thinning treatments (control, light thinning, moderate thinning, and heavy thinning) were implemented in 214 plots (~1800 tree ha−1) in three Masson pine forests in Hunan Province, China. A robustly designed experiment was used with over six years of repeated measurements. The differences in biomass increment and tree diversity among the different treatments were compared using repeated measures ANOVAs. The Mantel test was used to determine environmental metrics correlated with biomass increments across tree strata. Structural equation modeling was utilized to explore the multivariate relationships among site environment, tree diversity, and post-treatment biomass increment. The results indicated that thinning overall increased biomass increment, the Shannon index, and the Gini index, while decreasing the Dominance index over time. Moderate thinning (25%–35% of trees removed) was found to promote overstory biomass increment to 9.72 Mg·ha−1·a−1 and understory biomass increment to 1.43 Mg·ha−1·a−1 six years post-thinning, which is significantly higher than that of other treatments. Environmental metrics such as light intensity, soil organic matter, and other soil physiochemical properties were positively correlated with biomass increments, and their effects on the overstory and understory differed. Structural equation modeling revealed that thinning treatments, environmental metrics, tree diversity, and their interactions could be the main drivers for biomass increments across tree strata. Specifically, thinning treatments, light intensity, and tree size diversity (Gini index) had significant effects on overstory biomass increment, while understory species richness (Shannon index) and soil organic matter affected understory biomass increment. In conclusion, moderate thinning is an effective silvicultural treatment for stimulating biomass increments of both the overstory and understory in Masson pine forests in southern China if a middle period (e.g., six years) is considered. Some factors, such as species richness, tree size diversity, and environmental metrics (e.g., light and soil), are suggested for consideration to improve the efficiency of thinning. [ABSTRACT FROM AUTHOR]

There is a lack of research on whether tree size affects lamina and petiole biomass allocation patterns, whereas the trade‐off between leaf biomass allocated to the lamina and the petiole is of significance when considering the hydraulic and mechanical function of the leaf as a whole. Here, Camptotheca acuminata Decne was selected for study because of the availability of trees differing in size growing under the same conditions. A total of 600 leaves for two tree size groups and 300 leaves per group differing in height and trunk diameter were collected. The lamina fresh mass (LFM), lamina dry mass (LDM), lamina area (LA), petiole fresh mass (PFM), and petiole length (PL) of each leaf was measured, and reduced major axis regression protocols were used to determine the scaling relationships among the five functional traits. The bootstrap percentile method was used to determine if the scaling exponents of the traits differed significantly between the two tree size groups. The results indicated that (i) there was a significant difference in the LFM, LDM, PFM, PL, LMA, LFMA and PFM/LFM between large and small trees, but no significant difference in LA; (ii) the LA versus LFM, LA versus LDM, LFM versus PFM, LA versus PFM, and PL versus PFM scaling relationships of the two groups were allometric (i.e., not isometric); (iii) there were significant differences in the scaling exponents of LA versus LFM, LA versus PFM, PL versus PFM between the two groups, but there was no significant difference in the LFM versus PFM scaling relationship between the two groups of trees. The data were also consistent with the phenomenon known as "diminishing returns". These data indicate that tree size influences leaf biomass allocation patterns in ways that can potentially influence overall plant growth, and therefore have an important bearing on life‐history strategies. [ABSTRACT FROM AUTHOR]

Branch and cut is the dominant paradigm for solving a wide range of mathematical programming problems—linear or nonlinear—combining efficient search (via branch and bound) and relaxation-tightening procedures (via cutting planes, or cuts). While there is a wealth of computational experience behind existing cutting strategies, there is simultaneously a relative lack of theoretical explanations for these choices, and for the tradeoffs involved therein. Recent papers have explored abstract models for branching and for comparing cuts with branch and bound. However, to model practice, it is crucial to understand the impact of jointly considering branching and cutting decisions. In this paper, we provide a framework for analyzing how cuts affect the size of branch-and-cut trees, as well as their impact on solution time. Our abstract model captures some of the key characteristics of real-world phenomena in branch-and-cut experiments, regarding whether to generate cuts only at the root or throughout the tree, how many rounds of cuts to add before starting to branch, and why cuts seem to exhibit nonmonotonic effects on the solution process. [ABSTRACT FROM AUTHOR]

This article investigates smallest branch-and-bound trees and their computation. We first revisit the notion of hiding sets to deduce lower bounds on the size of branch-and-bound trees for certain binary programs, using both variable disjunctions and general disjunctions. We then provide exponential lower bounds for variable disjunctions by a disjoint composition of smaller binary programs. Moreover, we investigate the complexity of finding small branch-and-bound trees using variable disjunctions: We show that it is not possible to approximate the size of a smallest branch-and-bound tree within a factor of 2 1 5 n in time O (2 δ n) with δ < 1 5 , unless the strong exponential time hypothesis fails. Similarly, for any ε > 0 , no polynomial time 2 (1 2 - ε) n -approximation is possible, unless P = NP . We also show that computing the size of a smallest branch-and-bound tree exactly is # P -hard. Similar results hold for estimating the size of the tree produced by branching rules like most-infeasible branching. Finally, we discuss that finding small branch-and-bound trees generalizes finding short treelike resolution refutations, and thus non-automatizability results transfer from this setting. [ABSTRACT FROM AUTHOR]

Improving water-holding functions is an important purpose of sustainable forest management. However, few studies have examined whether there are differences in water-holding capacities between the forests dominated by trees associated with different mycorrhizal types and what are the main factors leading to the differences. Here, we investigated seven parameters of water-holding capacities of soils, litter, and canopy interception in 210 forest plots (10 m × 10 m). The plots were equally divided into three forest types associated with mycorrhizal types, including AM plots (arbuscular mycorrhizal trees > 75% in dominance), ECM plots (ectomycorrhizal trees > 75%), and AM + ECM plots (between 25 and 75%). We calculated tree diversity (richness, Shannon–wiener index, Simpson index, evenness), community structure (diameter at breast height, height, under branch height, density, neighborhood comparison-U, uniform angle index-W, and mingling index-M), and soil physics (soil bulk density and field water content). The results showed that: (1) ECM-dominated communities increased 1.6–2.0-fold in the litter water-holding capacities than those of AM and AM + ECM. The canopy interception of the ECM community was the highest (0.97 mm), significantly higher than that of the AM + ECM community (0.58 mm). (2) The ECM community had lower field soil water-holding capacity (p < 0.05) but 42–78% higher soil non-capillary water capacity than that of AM and AM + ECM (p < 0.05). (3) ECM forests were characterized by low tree species evenness, big-sized trees, and low bulk density, favoring increasing ecosystem water-holding capacities. Moreover, increasing ECM tree dominance enhanced the contribution of community structure to water-holding variations. (4) ECM trees increased ecosystem water-holding functions by direct effects (mainly on the litter) and indirect effects from soil physics (mainly on the soils) or tree size (mainly on the canopy) regulations. This study highlighted that ECM trees enhanced water-holding capacity, providing important information for planting and managing temperate water conservation forests. [ABSTRACT FROM AUTHOR]

Understanding the variation in fecundity, the reproductive capacity of individual trees, is crucial for predicting population dynamics and ecosystem functioning. However, estimating tree fecundity is challenging due to the large variation in seed production observed between trees and across years that necessitates logistically challenging long-term monitoring. This study aimed to investigate the factors influencing fecundity in rowan trees (Sorbus aucuparia) using a 22-year fruit-count dataset in 167 individual trees. We examined the relationship between fecundity and intrinsic (DBH, height, and leaf nutrient concentration) and extrinsic factors (soil nutrients, light availability, and neighborhood crowding). Our findings revealed that diameter at breast height (DBH) better explained variation in fecundity than height. After accounting for tree size using DBH, light availability had the strongest, positive effect on fecundity and was the major limiting factor for rowan's fecundity. At the same time, neighborhood crowding index with conspecifics also showed significant, but negative correlation with fecundity, suggesting competition for pollinators among rowan trees. Our findings contribute to a better understanding of seed production ecology and can inform management and conservation efforts that aim for increased fruit supply, either for plant populations or fruit consumers. [ABSTRACT FROM AUTHOR]

An important challenge in ecology is to link functional traits to plant survival for generalizable predictions of plant demographical dynamics. However, whether root and leaf traits are consistently associated with tree survival remains uncertain because of the limited representation of root traits. Moreover, the relationships between plant traits and survival are rarely linear and are likely to vary with tree size. We analyzed demographic data from 17 901 trees of 32 subtropical tree species under 3-year-old monocultures to test whether root and leaf traits have consistent relationships with tree survival and how the relationships between traits and tree survival vary with tree diameter. We discovered that leaf and root traits have inconsistent effects on tree survival. Specifically, while specific leaf area (SLA; an acquisition strategy) showed a marginally significant negative impact on survival, root diameter (RD; a conservative trait within the one-dimensional root economic spectrum) also demonstrated a significant negative effect on survival. Furthermore, we found size-dependent relationships between traits and tree survival. The effect of SLA, leaf phosphorus concentration and specific root length, on survival shifted from negative to positive with increasing tree size. However, species with high leaf thickness and RD were positively linked to survival only for small trees. The results highlight that to accurately predict the relationships between traits and tree survival, it is essential to consider both above- and belowground traits, as well as the size-dependent relationships between traits and tree survival. [ABSTRACT FROM AUTHOR]

Background: Understanding the influence of fires on terrestrial carbon stocks is important for informing global climate models and underpinning land management-based carbon markets. Aims: To quantify biomass carbon in south-western Australia's Great Western Woodlands – the world's largest extant Mediterranean-climate woodland – with time-since-fire and prior fire interval. Methods: Plot-based measurement of live and dead tree and shrub size, woody debris volume and litter mass across a ~400-year chronosequence to calculate biomass carbon. Key results: Biomass carbon increased with time-since-fire, reaching >65 Mg C ha−1, although the rate of increase declined in mature woodlands. Biomass carbon decreased after fire in these obligate-seeder woodlands, while a longer prior fire interval buffered carbon fluxes through retained large standing dead trees and fallen woody debris. Conclusions: The current age class distribution of the ~95,000 km2 of eucalypt woodlands in the region may support ~0.453 Pg C. Further refinement of carbon estimates explicitly considering variation in woodland type and climate, a continuous woodland age distribution and soil carbon are required to underpin a carbon methodology. Implications: Biomass carbon would be maximised by reducing the extent of bushfires impacting woodlands, focussing on existing mature stands that support the greatest carbon stocks. Fire regimes can have a significant bearing on terrestrial carbon stocks, with carbon markets potentially providing a mechanism to support land management activities. We quantify the effect of time-since-fire and prior fire interval on biomass carbon in the world's largest extant Mediterranean-climate woodland, located in south-western Australia. Photographs by C. Gosper. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Examining the changes in woody plant structural diversity along an inverse elevation-dependent warming gradient will enhance our mechanistic understanding of how warming affects forest communities because such an inverse elevational gradient reflects a warming trend in a mountain landscape. Here, we investigated the effects of warming on the patterns of species composition and structural diversity in a subtropical broadleaved forest. We calculated a warming index based on elevational difference and modeled the aspect-related potential incident radiation (PDIR) using nonparametric multiplicative regression. We tested the changes in structural diversity of three communities for significant differences along the warming gradient. We associated both the warming index and PDIR with the principal components and tested their relationships for significant differences. We found that trees of different sizes varied in their response to the warming gradient. While a significant decreasing trend was exhibited in both species diversity and size diversity for trees of all sizes and for adult trees along the warming gradient, no significant changes in seedlings were found, and the average basal area value was the highest for the warmest community. Our findings demonstrated that a short-range elevational gradient was adequate to separate the communities in species composition and structural diversity. Patterns of structural diversity along the warming gradient varied in size classes. The community at a higher elevation had more indicator species that were unique in separating the community from others. Principal component analysis showed that the first two principal components were negatively correlated with the warming index, indicating that warming destabilized species composition and community structure. Our study suggests that warming is the major driver of changes in structural diversity and species composition of woody plant communities in a subtropical broadleaved forest and that warming may promote tree productivity at the community level but reduce structural diversity at the quadrat level. [ABSTRACT FROM AUTHOR]

This article presents a new compressed representation of Boolean functions, called CFLOBDDs (for Context-Free-Language Ordered Binary Decision Diagrams). They are essentially a plug-compatible alternative to BDDs (Binary Decision Diagrams), and hence are useful for representing certain classes of functions, matrices, graphs, relations, and so forth in a highly compressed fashion. CFLOBDDs share many of the good properties of BDDs, but—in the best case—the CFLOBDD for a Boolean function can be exponentially smaller than any BDD for that function. Compared with the size of the decision tree for a function, a CFLOBDD—again, in the best case—can give a double-exponential reduction in size. They have the potential to permit applications to (i) execute much faster and (ii) handle much larger problem instances than has been possible heretofore. We applied CFLOBDDs in quantum-circuit simulation and found that for several standard problems, the improvement in scalability, compared to BDDs, is quite dramatic. With a 15-minute timeout, the number of qubits that CFLOBDDs can handle are 65,536 for Greenberger-Horne-Zellinger, 524,288 for Bernstein-Vazirani, 4,194,304 for Deutsch-Jozsa, and 4,096 for Grover's algorithm, besting BDDs by factors of 128×, 1,024×, 8,192×, and 128×, respectively. [ABSTRACT FROM AUTHOR]

We propose a random forest based estimation procedure for Quantile-Oriented Sensitivity Analysis—QOSA. In order to be efficient, a cross-validation step on the leaf size of trees is required. Our full estimation procedure is tested on both simulated data and a real dataset. Our estimators use either the bootstrap samples or the original sample in the estimation. Also, they are either based on a quantile plug-in procedure (the R-estimators) or on a direct minimization (the Q-estimators). This leads to 8 different estimators which are compared on simulations. From these simulations, it seems that the estimation method based on a direct minimization is better than the one plugging the quantile. This is a significant result because the method with direct minimization requires only one sample and could therefore be preferred. [ABSTRACT FROM AUTHOR]

Key message: Nested plot designs with concentric plots with increasing radii and size threshold underestimate tree species richness with respect to full census sampling with no tree size restrictions. Regeneration emerged as the most relevant pool for tree species richness estimation. Context: Nested or concentric plot designs, where trees are sampled according to their size and position, are common in National Forest Inventories (NFI) to reduce the sampling effort. However, this could bias the estimation of tree diversity such as species richness. Aims: The main goal of this study is to quantify the effect of the nested plot designs with increasing radii and diameter at breast height threshold on the number of tree species as well as to provide values for mean tree species richness per plot at the forest-type level using the Spanish NFI. Methods: We compared tree species richness according to the Spanish NFI nested plot design (radii ranging from 5 to 25 m with increasing minimum threshold in dbh from 7.5 to 42.5 cm as well as the regeneration compartment) with the richness estimate based on a full census (without restrictions in the location or size) in the Spanish NFI 25 m radius plot. Results: Our results confirmed the underestimation of tree species richness (around 32.5%) when using the nested design. The species omitted in the nested design sampling are often subordinates, typically with small diameters. Regeneration emerged as the main pool for tree species richness estimation. This pattern holds across the main forest types, indicating that it is a generalized rather than regional or local phenomenon. Conclusion: We strongly recommend using full census data for assessing tree species richness whenever available, as relying solely on nested designs can significantly underestimate tree species richness. [ABSTRACT FROM AUTHOR]

Estimating growing stock is one of the main objectives of forest inventories. It refers to the stem volume of individual trees which is typically derived by models as it cannot be easily measured directly. These models are thus based on measurable tree dimensions and their parameterization depends on the available empirical data. Historically, such data were collected by measurements of tree stem sizes, which is very time- and cost-intensive. Here, we present an exceptionally large dataset with section-wise stem measurements on 40'349 felled individual trees collected on plots of the Experimental Forest Management project. It is a revised and expanded version of previously unpublished data and contains the empirically derived coarse (diameter ≥7 cm) and fine branch volume of 27'297 and 18'980, respectively, individual trees. The data were collected between 1888 and 1974 across Switzerland covering a large topographic gradient and a diverse species range and can thus support estimations and verification of volume functions also outside Switzerland including the derivation of whole tree volume in a consistent manner. [ABSTRACT FROM AUTHOR]

When communities are assembled through processes such as filtering or limiting similarity acting on phylogenetically conserved traits, the evolutionary signature of those traits may be reflected in patterns of community membership. We show how the model of trait evolution underlying community-structuring traits can be inferred from community membership data using both a variation of a traditional eco-phylogenetic metric—the mean pairwise phylogenetic distance (MPD) between taxa—and a recent machine learning tool, Convolutional Kitchen Sinks (CKS). Both methods perform well across a range of phylogenetically informative evolutionary models, but CKS outperforms MPD as tree size increases. We demonstrate CKS by inferring the evolutionary history of freeze tolerance in angiosperms. Our analysis is consistent with a late burst model, suggesting freeze tolerance evolved recently. We suggest that multiple data types that are ordered on phylogenies, such as trait values, species interactions, or community presence/absence, are good candidates for CKS modeling because the generative models produce structured differences between neighboring points that CKS is well-suited for. We introduce the R package kitchen to perform CKS for generic application of the technique. [ABSTRACT FROM AUTHOR]

Forest above‐ground biomass (AGB) is often estimated by converting the observed tree size using allometric scaling between the dry weight and size of an organism. However, the variations in biomass allocation and scaling between tree crowns and stems due to survival competition during a tree's lifecycle remain unclear. This knowledge gap can improve the understanding of modelling tree biomass allometry because traditional allometries ignore the dynamics of allocation.Herein, we characterised allometric scaling using the dynamic ratio (r) of the stem biomass (SB) to AGB and a dynamic exponent. The allometric models were biologically parameterised by the r values for initial, intermediate and final ages rather than only a regression result. The scaling was tested using field measurements of 421 species and 2213 different‐sized trees in pantropical regions worldwide.We found that the scaling fluctuated with tree size, and this fluctuation was driven by the trade‐off relationship of biomass allocation between the tree crown and stem depending on the dynamic crown trait. The allometric scaling between SB and AGB varied from 0.8 to 1.0 for a tree during its entire lifecycle. The fluctuations presented a general law for the allometric scaling of the pantropical tree biomass and size. Our model quantified the trade‐off and explained 94.1% of the allometric relationship between the SB and AGB (93.8% of which between D2H and AGB) for pantropical forests, which resulted in a better fit than that of the traditional model. Considering the effects of the trade‐off on modelling, the actual biomass of large trees could be substantially greater than conventional estimates.These results highlight the importance of coupling growth mechanisms in modelling allometry and provide a theoretical foundation for better describing and predicting forest carbon accumulation. [ABSTRACT FROM AUTHOR]

Aim: At fine scales (<10 km in spatial resolution), only a few studies have evaluated the relationships between abiotic factors and the horizontal occurrence of vascular epiphytes. At fine scales, variation in abiotic variables can be attributed to topographic heterogeneity. For example, air humidity and wind speed are likely to vary along ridge–valley gradients, and differences in slope aspect cause variation in light intensity as well as temperature gradient along an elevation. We tested the hypothesis that the horizontal epiphyte occurrence at fine scales is influenced more by topographic gradients related to abiotic factors than by host tree size and species. We also assessed air humidity variation along the ridge–valley gradient at our study site as a way to explore its possible correlation with the epiphyte occurrence. Location: A coniferous/broadleaf evergreen mixed forest in a humid temperate zone of Kochi, southwest Japan. Methods: We surveyed epiphyte occurrence on 310 trees and recorded host tree size and species within a 52‐ha watershed with an elevational range of 378–777 m a.s.l. Epiphyte occurrence was modeled using three topographic variables (ridge–valley gradient, slope aspect differences and elevational gradient), host tree size and species. The effect sizes of each variable were then compared. Air humidity was measured on the valley bottom, slope and ridge throughout the year. Results: Epiphyte occurrence probability increased toward the valley bottom and on larger host trees; it also varied among host tree species. Slope aspect differences and elevational gradient were less effective. The ridge–valley gradient had a greater effect than host tree size on epiphyte occurrence. Air humidity was highest at the valley bottom and lowest on the ridge. Conclusions: Horizontal epiphyte occurrence was driven more by topographic gradient than by host tree size and species in a small watershed covered by a warm‐temperate broadleaf forest. This finding suggests the importance of forests at valley bottoms to support epiphyte occurrence. [ABSTRACT FROM AUTHOR]

This article shows how probability sampling and citizen science efforts can complement each other, using the USDA Forest Service's Forest Inventory and Analysis (FIA) program and the ongoing search by the National Register of Champion Trees (NRCT) for the largest specimen of each naturally occurring tree species in the United States as an example. We develop a ratio statistic (Z s ) that uses the difference in size of the largest tree of a species from each database to order the tree species according to the assumed ease with which a larger specimen than the current national champion might be found. Our results show ninety-two candidate species that have been recorded by FIA for which there is no national champion and sixty-five species for which a new champion should be easy to find. In a supplemental table, we show ninety-four species listed as observable by FIA in the NRCT but not recorded in the FIA sample. Study Implications: An interest in forests and forestry is always accompanied by an interest in trees, especially very big trees. Two very different ways of learning about trees are analyzed concurrently in a way that reveals their complementarity. The two efforts are the probability sample, conducted by the USDA Forest Service's Forest Inventory and Analysis (FIA) Program, and the citizen science effort known as the National Register of Champion Trees (NRCT). We develop a statistic that will help tree sleuths find champion trees and provide FIA practitioners with a quality control measure and an indication of which species would benefit from an increase in sample intensity. [ABSTRACT FROM AUTHOR]

Copyright of Fire Ecology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tropical forests continue to face deforestation in countries such as the Philippines. To look at the long-term behavior of forests in response to intrinsic and extrinsic factors, continual monitoring of forest dynamics is needed. To do this, we established a 2-ha permanent tropical forest plot in a low-disturbance area in Maluyon, Philippines. We addressed three main questions: 1) How does the plot change through time? 2) How do different species in the plot change through time? 3) Would the responses differ by tree size? We measured, mapped, and identified all trees >1 cm in diameter in 2011. In 2015, we re-measured surviving trees and measured, mapped, and identified recruits. A total of 177 tree species were found in the plot. The forest exhibited a mean growth rate of 0.054 cm/year, mortality rate of 0.011%/year, and recruitment rate of 0.019%/year. Overall growth and mortality rates were lower in Maluyon than in other plots, possibly due to the forest’s high tree density and low disturbance. Species-specific rates revealed the presence of both the growth-survival and the stature-recruitment trade-offs. Size class analysis showed higher growth rates in largesized than in small-sized trees. In contrast, small-sized trees exhibited a higher mortality rate compared to large-sized trees, likely due to density dependence. Key findings of the study may be utilized to increase the success rate of restoration efforts in this watershed. Using a mix of fast-growing, generalist species with high survival rates (e.g., Allophyllus cobbe and Anisoptera thurifera) is highly recommended. [ABSTRACT FROM AUTHOR]

The expansion of forested areas through afforestation and reforestation is widely recognized as a highly effective natural solution for mitigating climate change. Accurately assessing the potential carbon uptake capacity of newly afforested areas requires modelling tools to estimate biomass stocks, including site index curves and biomass models. Given the unique conditions in terms of tree size, uniform spacing, and tree allometries observed in young afforestations compared to natural stands, specific tools are necessary. In Spain, over 800,000 ha has been afforested with native forest species since 1992, but specific modelling tools for these plantations are lacking. Using data from 370 stem analyses collected across an extensive network of plots in young afforestations, we developed dynamic height growth and site index models for the main native species (five pines and five oaks) commonly used in afforestation in Spain. We compared various nonlinear models, such as ADA (algebraic difference approach) and GADA (generalized algebraic difference approach) expansions. The developed site index models were then used to predict the total biomass stored in the afforestation. Our results underscore the necessity for specific site index models tailored to afforestations, as well as the potential of the established site index in predicting biomass and carbon fixation capacity in these young forests. [ABSTRACT FROM AUTHOR]

Alberta's forest industry is predicted to be impacted by a medium-term decline in timber supply. Intensive silviculture tools, such as pre-commercial thinning, have been shown to increase individual tree growth, shorten rotation lengths, and improve stand merchantability in important commercial species such as lodgepole pine. However, lodgepole pine stands are susceptible to western gall rust infections, and thinning at an early stage may increase infection rates. This study collected tree and stand level data from 33 operational harvest origin lodgepole pine stands consisting of 11 stands thinned at age 17–19 years (PCT_18), 11 stands thinned at age 23–25 (PCT_24), and 11 unthinned stands. Approximately 40 years after pre-commercial thinning, merchantable volume is similar in all stands but thinned stands, regardless of timing, had greater individual tree size (~15% higher) compared to unthinned stands. Pre-commercially thinned stands also had a higher potential for commercial thinning since they have lower variability in tree size and longer live crown lengths. In addition, delayed thinning (PCT_24) reduced western gall rust infections and the severity of infections compared to both PCT_18 and unthinned stands. In conclusion, pre-commercial thinning should be considered for lodgepole pine stands in order to address timber supply issues in Alberta. [ABSTRACT FROM AUTHOR]

Secondary forests are increasingly important for biodiversity conservation and ecosystem functioning. Yet, we know little on how species interactions shift across the wide range of life history strategies in the context of forest succession, especially for non‐trophic animal social systems.Using data from mixed‐species flocks (hereafter MSFs) and life history and morphological traits from the 'fast‐slow' continuum, we utilized a novel combination of network theory and trait‐based ecology to examine the assembly of associations of MSFs among species with different fast‐slow strategies across stages of forest succession that exhibit different degrees of forest complexity.MSFs formed the most connected and cohesive network in the intermediate successional stage. In contrast, we observed the least connected and cohesive network in the early stage, and a strongly connected but intermediately cohesive network in the late stage. Fast species with smaller body size and mass, and larger clutch size, were gradually replaced by slow species during succession. Interspecific associations generally shifted from those among similarly fast species (early stage) to associations between fast and slow species (intermediate stage), and finally to those among similarly slow species (late stage).We suggest that vegetation complexity (e.g. tree size, height, diversity and canopy cover), related to the availability of resources and number of niches, shaped the network structure and functional composition of MSFs. Although the late successional forests play an irreplaceable role in protecting forest specialists (i.e. slow species), intermediate stage forests should be also protected, because the large‐sized networks formed by MSFs at intermediate stages can simultaneously conserve more species with varying ecological strategies. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Agricultural Sciences is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Each year, an average of 45 tropical cyclones affect coastal areas and potentially impact forests. The proportion of the most intense cyclones has increased over the past four decades and is predicted to continue to do so. Yet, it remains uncertain how topographical exposure and tree characteristics can mediate the damage caused by increasing wind speed. Here, we compiled empirical data on the damage caused by 11 cyclones occurring over the past 40 years, from 74 forest plots representing tropical regions worldwide, encompassing field data for 22,176 trees and 815 species. We reconstructed the wind structure of those tropical cyclones to estimate the maximum sustained wind speed (MSW) and wind direction at the studied plots. Then, we used a causal inference framework combined with Bayesian generalised linear mixed models to understand and quantify the causal effects of MSW, topographical exposure to wind (EXP), tree size (DBH) and species wood density (ρ) on the proportion of damaged trees at the community level, and on the probability of snapping or uprooting at the tree level. The probability of snapping or uprooting at the tree level and, hence, the proportion of damaged trees at the community level, increased with increasing MSW, and with increasing EXP accentuating the damaging effects of cyclones, in particular at higher wind speeds. Higher ρ decreased the probability of snapping and to a lesser extent of uprooting. Larger trees tended to have lower probabilities of snapping but increased probabilities of uprooting. Importantly, the effect of ρ decreasing the probabilities of snapping was more marked for smaller than larger trees and was further accentuated at higher MSW. Our work emphasises how local topography, tree size and species wood density together mediate cyclone damage to tropical forests, facilitating better predictions of the impacts of such disturbances in an increasingly windier world. [ABSTRACT FROM AUTHOR]

The existence of simple uncoupled no-regret learning dynamics that converge to correlated equilibria in normal-form games is a celebrated result in the theory ofmulti-agent systems. Specifically, it has been known for more than 20 years that when all players seek to minimize their internal regret in a repeated normalform game, the empirical frequency of play converges to a normal-form correlated equilibrium. Extensiveform (that is, tree-form) games generalize normal-form games by modeling both sequential and simultaneous moves, as well as imperfect information. Because of the sequential nature and presence of private information in the game, correlation in extensive-form games possesses significantly different properties than in normalform games, many of which are still open research directions. Extensive-form correlated equilibrium (EFCE) has been proposed as the natural extensive-form counterpart to the classical notion of correlated equilibrium in normal-form games. Compared to the latter, the constraints that define the set of EFCEs are significantly more complex, as the correlation device (a.k.a. mediator) must take into account the evolution of beliefs of each player as they make observations throughout the game. Due to that significant added complexity, the existence of uncoupled learning dynamics leading to an EFCE has remained a challenging open research question for a long time. In this article, we settle that question by giving the first uncoupled no-regret dynamics that converge to the set of EFCEs in n-player general-sum extensive-form games with perfect recall.We show that each iterate can be computed in time polynomial in the size of the game tree, and that, when all players play repeatedly according to our learning dynamics, the empirical frequency of play after T game repetitions is proven to be a O(1/√ T )-approximate EFCE with high probability, and an EFCE almost surely in the limit. [ABSTRACT FROM AUTHOR]

This study explores the resilience and damage dynamics of agroforests, a critically important yet understudied agroecological system, in the aftermath of Category-5 Cyclone Winston in Fiji. As agroforestry gains prominence globally as a versatile production system able to support agrobiodiversity and food security for climate resilience, understanding the characteristics that contribute to its resistance and resilience to disturbance becomes increasingly important. Here we examine the effects of individual and species-specific traits, and management (planted and fallow vs forest areas) on the probability of tree stem survival and damage, and discuss the resistant and resilient qualities of trees and management actions in these systems. We found that the probability of post-cyclone survival increased as a function of wood density, irrespective of management type. Damage severity increased with tree size (diameter at breast height). Some of the species with the highest wood density were native trees, emphasizing the role of native species in agroforests, and the value of agroforests to conservation. Overall, agroforest trees experienced relatively low stem mortality (12.2%), suggesting that these agroforests may resist extreme disturbances despite their potential vulnerabilities such as landscape edge effects and altered species compositions. Our study provides insight into the potential of agroforests as resilient agroecological systems capable of withstanding escalating cyclone intensities, and the role of effective management strategies for fostering resilience amid a rapidly changing climate. [ABSTRACT FROM AUTHOR]

Forest dynamics are undergoing profound alteration due to the fact that climate change is increasing the frequency and severity of abiotic and biotic forest disturbances. Because of the unpredictable nature of the drought periods and the variation in their severity, Mediterranean forests are typically more vulnerable. Mediterranean Pinus pinaster forests are showing decay symptoms linked to climate change. There is clear evidence that promoting mixtures can serve as an effective forest adaptation strategy. In this regard, we sought to better understand the responses of P. pinaster radial growth dynamics to various factors, in both mixed and pure forest stands, and provide valuable insights into P. pinaster dynamics when mixed with P. sylvestris. In this study, we examined the variation of intra-annual cumulative radial increment patterns in response to the climate of P. pinaster between pure and mixed stands with P. sylvestris. Using data from band dendrometers collected over five consecutive climatically distinct years (2016–2020), a nonlinear mixed-effect model approach was used to analyze the differences in intra-annual cumulative radial increment patterns for P. pinaster between years in mixed and pure stands. The intra-annual radial increment pattern of P. pinaster showed significant year-to-year variation and varied with tree size, with greater increment in larger trees. Trees in mixed stands had a higher mean radial increment compared to corresponding ones in pure stands. Increased summer maximum temperatures negatively affected tree cumulative annual increment regardless of composition, but with a lower impact on trees in pure stands. Spring precipitation increased the length of the growing season, while higher spring maximum temperatures triggered an earlier inflection point. Our results highlight the high plasticity of P. pinaster in adapting to varying intra- and inter-annual environmental conditions and competition with other species and suggest that promoting mixtures with P. sylvestris may be an interesting management strategy for adaptation to climate change. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the carbon and environmental service potential in the natural tourism zone of special purpose forest areas Mount Bromo. The study focused on understanding how this area, with its specific tree compositions and sizes, contributes to carbon absorption and environmental benefits, which can also translate into carbon credits, a form of state revenue. The methodology involved purposive sampling to create observational sample plots (OSP) of varying sizes based on tree diameter. These plots were designed to measure the biomass, carbon potential, and environmental service potential of the trees in a given area. The collected data included the composition of tree species, the number of each type of tree, their diameters, and heights. The study applied specific formulas to determine the potential of biomass, carbon, and environmental services in the area. Key findings revealed a dominance of mahogany trees (83 trees per hectare) among ten identified plant species, indicating a specific but lower biodiversity in this zone. The significant results of the study include the quantification of biomass potential, which was found to be 787.84 tons/ha above-ground and 228.47 tons/ha below-ground, totaling 1016.31 tons/hectare. The study also evaluated the environmental service potential, including CO2 absorption and O2 production. The CO2 absorption capacity of the area was estimated at 1753.04 tons/ha, with a corresponding high O2 production of 1279.72 tons/ha. Additionally, the potential for carbon credits in the area was calculated at approximately 70.12 US$/ha. This research is crucial in understanding how specific forest areas, like special purpose forest areas Mount Bromo, can play a significant role in global environmental sustainability efforts. [ABSTRACT FROM AUTHOR]

Phenological research is engaged in monitoring the influence of climate change on the natural environment. The International Phenological Gardens (IPG) network provides a valuable dataset of standardized tree phenology records dating back to the mid-20th century. To make best use of this actively growing record, it is important to investigate how network data can be applied to predict the timing of phenological events in natural populations. This study compared clonally propagated IPG downy birch (Betula pubescens Ehrh.) and hazel (Corylus avellana L.) specimens of central European provenance to nearby wild populations at the western-most margin of the IPG network, in the south-west of Ireland. In addition to monitoring by trained scientists, observations by citizen scientists were included. The order of the timing of phenological events among sites was consistent across 2 years, confirming reproducibility of the results. IPG trees had the earliest B. pubescens leaf unfolding and C. avellana flowering dates of the sites studied. In addition, leaf unfolding occurred later in the wild populations than expected from the temperature responses of the B. pubescens and C. avellana IPG clones. Natural variation in phenology also exceeded the historical change observed at the IPG site, suggesting a potential genetic basis for climate adaptation. Trunk circumference, reflecting the age-dependent increase in tree size, was found to influence C. avellana phenology, with earlier timing of phenological events in larger trees. This finding highlights tree size as an important consideration in the management of phenological gardens and tree phenology research in general. [ABSTRACT FROM AUTHOR]

Residual canopy transpiration (Emin_canop) is a key physiological trait that determines trees' survival time under drought after stomatal closure and after trees have limited access to soil water. Emin_canop mainly depends on leaf minimum conductance (gmin) and vapor pressure deficit. Here we determined the seasonal variation of gmin and how gmin is related to interspecies variation in leaf cuticular and stomatal traits for nine European tree species in a mature forest. In addition, we determined the species-specific temperature responses of gmin. With this newly obtained insight, we calculated Emin_canop for the nine species for one day at our research site during the 2022 central European hot drought. Our results show that at ambient temperatures gmin ranged from 0.8 to 4.8 mmol m−2 s−1 across the nine species and was stable in most species throughout the growing season. The interspecies variation of gmin was associated with leaf cuticular and stomatal traits. Additionally, gmin exhibited strong temperature responses and increased, depending on species, by a factor of two to four in the range of 25–50 °C. For the studied species at the site, during a single hot drought day, Emin_canop standardized by tree size (stem basal area) ranged from 2.0 to 36.7 L m−2, and non-standardized Emin_canop for adult trees ranged from 0.3 to 5.3 L. Emin_canop also exhibited species-specific rapid increases under hotter temperatures. Our results suggest that trees, depending on species, need reasonable amounts of water during a drought, even when stomates are fully closed. Species differences in gmin and ultimately Emin_canop can, together with other traits, affect the ability of a tree to keep its tissue hydrated during a drought and is likely to contribute to species-specific differences in drought vulnerability. [ABSTRACT FROM AUTHOR]