Major Tree Research Articles

Biotic threats for 23 major non-native tree species in Europe

For non-native tree species with an origin outside of Europe a detailed compilation of enemy species including the severity of their attack is lacking up to now. We collected information on native and non-native species attacking non-native trees, i.e. type, extent and time of first observation of damage for 23 important non-native trees in 27 European countries. Our database includes about 2300 synthesised attack records (synthesised per biotic threat, tree and country) from over 800 species. Insects (49%) and fungi (45%) are the main observed biotic threats, but also arachnids, bacteria including phytoplasmas, mammals, nematodes, plants and viruses have been recorded. This information will be valuable to identify patterns and drivers of attacks, and trees with a lower current health risk to be considered for planting. In addition, our database will provide a baseline to which future impacts on non-native tree species could be compared with and thus will allow to analyse temporal trends of impacts.

Mass outbreaks and factors related to the spatial dynamics of spruce bark beetle (Ips typographus) dieback considering diverse management regimes in the Białowieża forest

Dealing with tree mortality caused by forest pests is one of the most demanding challenges in forest protection and management. The current spruce bark beetle infestation in the Polish part of the Białowieża Forest (BF), which started in 2012, is considered the largest in history and has nearly eliminated Norway spruce (Picea abies (L.) Karst) as a major forest tree species there. This research analyzed the dynamics and spatial extent of the BF outbreak from 2015 to 2019. The extensive beetle epidemic caused a more than six times higher number of infested trees in 2019 as compared to 2015. Under the conditions of the unprecedented ongoing I. typographus outbreak, the dynamics of spruce stand mortality varied across the study area. A lower spruce mortality was observed in Białowieża National Park as compared to other forest districts. Host and environmental factors influenced the timing of spruce mortality. Spruce height, stand age, the proportion of spruce, the share of area covered by tree crowns, excluding spruce and dominant species in the stands, were the key factors of bark beetle infestation. The most intensive outbreak progressed in stands older than 100 years dominated by spruce, and areas with the lowest dynamics of spruce dieback were localized in mixed young forests or pine stands. The methods and results presented in this study serve as baseline information, supporting the efforts to model the spread of bark beetles and future decision-making.

The hydraulic characteristics of the whole branch and its components of the major tree species in the eastern region of northeast China

The hydraulic characteristics of the whole branch and its components of the major tree species in the eastern region of northeast China

Stemflow variability across tree stem and canopy traits in the Brazilian Cerrado

The Cerrado savanna of Brazil is considered the most biodiverse savanna in the world and its vegetation acts as an interface between rainfall and recharge processes for the largest aquifer system (Guarani) in South America. Understanding how major Cerrado tree species affect the amount and patterns of rainfall at the surface, therefore merits scientific attention. Some rainfall that contacts the Cerrado canopy will be drained to a concentrated area around the stem base as ‘stemflow.’ Hypothetically, this spatially concentrated hydrologic flux may contribute nontrivially to recharge. Here, we examine stemflow variability over 13 months for 151 trees, representing 36 species common to the region, with a large range in stem and canopy structures. Bark texture, stem diameter at breast height (D) and the canopy height-to-width ratio (H:W) were measured for all trees, then individuals were sorted into three classes: smooth, scaled and furrowed bark texture; < 10, 10–20 and > 20 cm D; and < 1, 1,2 and > 2 canopy H:W. These data were used to investigate how tree morphological traits influence stemflow in the Cerrado. Stemflow over the study period represented 2.5% of rainfall, and the contribution of each morphological class to the region's scaled total stemflow yield was calculated. Although median stemflow volumes per storm were significantly different between bark textures (smooth > scaled > furrowed); the interrelated effects of canopy structure (H:W) and tree size (DBH) resulted in a relatively well-balanced representation of all bark classes to the Cerrado's total stemflow yield (41% from smooth-barked trees, 30% scaled-bark trees, and 29% furrowed-bark trees), regardless of the density of individuals belonging to each class analyzed. Large trees (D>20) with low canopy H:W<1 and scaled bark produced the lowest median stemflow fractions. The highest contribution to stand-scale stemflow yield in this Cerrado study was linked to the combination of stem and canopy traits in three ways: (1) trees with smooth bark dominated by D<10 and H:W1-2; (2) trees with D10–20 dominated by smooth bark and H:W1-2 ratio, and (3) trees with H:W1-2, dominated by smooth/furrowed bark trees and D<10. These findings highlight the importance of trait-based approaches in studying how tree stem (bark), size (DBH), and canopy (H:W) structural traits interact to affect stemflow generation, while filling a knowledge gap regarding the ecohydrology of the Brazilian Cerrado.

PHARMACOGNOSTIC AND PHYTO-PHYSICOCHEMICAL EVALUATION OF Solanum xanthocarpum Serb. &amp; Wendl.

Medicinal plants are the backbone of Traditional systems of medicine like Ayurveda and Siddha. Solanum xanthcarpum (Solanaceae) (SX) is one of the most widely used medicinal herbs in Ayurvedic Pharmacopia. Me- dicinal plants have been of age-long remedy for human diseases because they contain components of therapeutic value. Plants are rich sources of ecologically developed secondary metabolites, which are potential remedies for different ailments. Kantakari (SX) of the family Solanaceae is one of the ‘dasamoola' and widely used drugs in Ayurveda. Dasamoola means a combination of ten plant roots together. It comprises roots of five big or major trees (Brihat panchmoola) and roots of five small trees or major herbs (Laghu panchmoola). Various studies indicated that SX contains steroidal glycoalkaloid solasodine, β-solamagrine and solasonine. The indigenous uses of plants also indicate anti-inflammatory, Antispermatogenic, Antidiabetic, Antiasthmatic, Molluscidal activity, useful in in- fantile atopical dermatitis, Cytoprotective, anticancer, insecticidal, insect repellent properties and diuretic activities. Therefore, the present investigation was intended to evaluate the preliminary phytochemical characters of this plant. The data and results of Phytochemical studies in the present study would facilitate discovery for the synthesis of more potent drugs. Keywords: Solanum xanthocarpum, Dasamoola, ethnobotanical uses, pharmacognosy, pharmacological activities,

Histological dissection of cutting-inducible adventitious rooting in Platycladus orientalis reveals developmental endogenous hormonal homeostasis

De novo root regeneration in stem cutting is essential for massive propagation of Platycladus orientalis (L.) Franco, which is one of the major ecological and economic tree species in China. However, the details of adventitious root (AR) formation and how it is controlled by inherent hormones are still ambiguous. In this study, histological analysis, immunohistochemical localization combined with quantitative hormonal analysis were conducted to investigate how cutting induces the AR formation of P. orientalis. It was explicitly seen that AR emerged from either calli- or non-calli- covered barks. The anatomical structure showed that cutting initiated the inducible formation of AR primordia in multiple sites, including xylem, phloem, medullary ray, and annulus randomly. The tissue-specific accumulations of indole-3-acetic acid (IAA) surged in cambia-derived calli, basal boundaries of AR primordia, and AR, supporting the idea that the mode action of auxin was key to diverse types of root organogenesis. Meanwhile, the data showed that similar to that of IAA, the contents of abscisic acid (ABA) and zeatin (ZT) peaked at early stages of AR formation and deceased gradually in both phloem and xylem across the later stages, suggesting their indispensable roles in AR initiation. On contrary, jasmonic acid (JA) roughly maintained at extremely high levels in phloem comparing with the xylem tissues thoroughly, indicating its presence was involved in phloem-specific reorganization during AR formation. Collectively, the results provide a time-course histological dissection of AR formation, revealing developmental homeostasis of four main endogenous hormones, and providing theoretically a potential way to improve performance of stem-cutting in P. orientalis through regulating hormone actions in the future.

Effects of CaO on the Clonal Growth and Root Adaptability of Cypress in Acidic Soils

Cypress (Cupressus funebris Endl.) is a major tree species planted for forestland restoration in low-fertility soil and in areas where rocky desertification has occurred. Calcium (Ca) fertilizer can adjust the pH of soil and has an important effect on the growth of cypress. Soil and water losses are serious in Southern China, and soil acidification is increasing, which results in high calcium loss. However, the adaptability of cypress clones to different concentrations of calcium in acidic soils has not been studied. In this investigation, a potted-plant experiment was set up with three concentrations of calcium oxide (CaO) fertilizer (0, 3, and 6 g·kg−1) added under local soil conditions with 0 and 3 g·kg−1 nitrogen (N), phosphorus (P), and potassium (K) fertilizer. The effects of CaO on the growth, root development, and nutrient uptake and utilization efficiency of cypress clones were analyzed. The growth, root development, and nutrient absorption and utilization of cypress differed when calcium fertilizer was applied to acidic soils with different degrees of fertility. In the soil with 0 g·kg−1 NPK fertilizer, the 3 and 6 g·kg−1 CaO treatments significantly increased the clonal growth of cypress seedling height, basal diameter, and dry-matter weight. In addition, the length, surface area, and volume of the roots less than 2.0 mm of root diameter also significantly increased, indicating that the fine cypress roots were somewhat able to adapt to differing Ca levels under lower fertility conditions. Moreover, the efficiency of N, P, and Ca accumulation was highest in the 3 g·kg−1 CaO treatment. After adding 3 g·kg−1 CaO fertilizer to the soil with 3 g·kg−1 NPK fertilizer, only the root dry-matter weight increased significantly, indicating that root development (including root length, surface area, and volume) in the D1–D3 diameter classes (≤1.5 mm in diameter) was significantly elevated. When CaO application reached 6 g·kg−1, the seedling height, basal diameter, and dry-matter weight of each organ decreased, as did the length, surface area, and volume of the roots in the all diameter classes, indicating that the addition of excessive CaO to fertile soil could inhibit the growth and root development of cypress. In Ca-deficient low-quality acidic soils, adding CaO fertilizer can promote the development of fine roots and the uptake and utilization of N, P, and Ca. The results of this study provide a basis for determining the optimal fertilization strategy when growing cypress in acidic soils in Southern China.

Does coal fly ash influence the growth of mangroves?

A 1320-Megawatt capacity coal-fired power plant is establishing near the Ecologically Critical Area of the Sundarbans, Bangladesh. This power plant will generate 0.71 million tons of coal fly ash annually. Most of the previous studies concentrated on the soil amelioration and growth and yield of agricultural crops. However, this study investigated the effects of coal fly ash on the seedling growth (collar diameter, height, and biomass) of the major tree species (Bruguiera sexangula, Excoecaria agallocha, Heritiera fomes, and Xylocarpus mekongensis) of the Sundarbans, as well as to assess the nutrient (N, P, and K) partitioning in their parts (leaf, stem, and roots). Mangrove soil and coal fly ash were mixed to get seven treatments say T0, T1, T2, T3, T4, T5, and T7, which contained 0%, 5%, 10%, 20%, 30%, 40% and 50% of fly ash (w/w) respectively. A significant (p < 0.05) variation was observed among the species and treatments. Irrespective of species, almost similar growth for collar diameter, height, and biomass was observed for the treatments up to 10% of fly ash mixture. Collectively, a common decreasing trend for growth parameters was observed for the treatments of the higher proportion of fly ash. Similar to the growth pattern, nitrogen and potassium concentration in seedling parts showed a decreasing pattern at the higher proportion of fly ash. In conclusion, coal fly ash did not influence the growth of these studied mangrove species in a positive way but can tolerate up to 10% of fly ash mixture.

Isolation of high-quality RNA from plant seeds

The apple (Malus domestica Borkh.) is one of the major fruit tree crops, but it hasn’t been well-studied as a breeding object for molecular investigations. It is important to develop reliable and rapid methods that allow the preparation of plant material for future research. We introduce a quick and simple method for isolating high-quality RNA from lipid-rich apple seeds (M. domestica cv. Golden Delicious). Our method does not employ highly toxic reagents, because we exclude phenol, 2-mercaptoethanol and others. The chemical composition of the extraction buffer is simple and has a minimum level of toxicity. We showed that, in chaotropic conditions (i.e., with lithium chloride-urea), silica (SiO2) can bind with the lipids and RNA will remain in the solution. The extracted RNA was of high quality and we successfully used it for synthesizing cDNA and RT-PCR. The protocol developed by us can be useful for researchers working with RNA extraction from plant seeds.

Climate Analogues for Temperate European Forests to Raise Silvicultural Evidence Using Twin Regions

Climate analogues provide forestry practice with empirical evidence of how forests are managed in “twin” regions, i.e., regions where the current climate is comparable to the expected future climate at a site of interest. As the twin regions and their silvicultural evidence change with each climate scenario and model, we focus our investigation on how the uncertainty in future climate affects tree species prevalence. We calculate the future climate from 2000 to 2100 for three ensemble variants of the mild (representative concentration pathway (RCP) 4.5) and hard (RCP 8.5) climate scenarios. We determine climatic distances between the future climate of our site of interest ‘Roth’ and the current climate in Europe, generating maps with twin regions from 2000 to 2100. From forest inventories in these twin regions we trace how the prevalence of 23 major tree species changes. We realize that it is not the ‘how’ but the ‘how fast’ species’ prevalence changes that differs between the scenario variants. We use this finding to develop a categorization of species groups that integrates the uncertainty in future climate. Twin regions provide further information on silvicultural practices, pest management, product chains etc.

Phenological shifts induced by climate change amplify drought for broad-leaved trees at low elevations in Switzerland

Climate change alters the bioclimatic conditions during the growing period of trees directly, but also indirectly by causing shifts in spring and autumn leaf phenology that lead to changes in the timing and length of the growing period. Several studies researched the ecological consequences of direct climate change effects on bioclimatic conditions during the growing period of trees. However, the complementary and indirect effects through phenological shifts on these conditions have been insufficiently investigated. We analysed 49088 leaf unfolding and leaf colouring dates of six major European tree species from Switzerland, observed between 200 and 1900 m a.s.l. during 1961–2018. We estimated phenological trends, the resulting changes in bioclimatic conditions during the growing period, and the relative contributions of phenological shifts towards these changes. Our results show that climate change advanced leaf unfolding by up to –3.0 days/decade since 1985. Leaf colouring was mainly delayed at low elevations and was advanced or delayed at high elevations with species-specific rates between –3.1 and +4.0 days/decade. While the length of the growing period and growing degree-days increased for most species after 1985, precipitation during the growing period predominantly decreased by up to –43.6 mm/decade. Furthermore, drought intensity during the growing period (based on the number of days with negative water balance) increased significantly for most species, reaching +6.7 days/decade at low elevations. Phenological shifts amplified the trends towards drier conditions by up to +81% at low elevations for beech, rowan, and sycamore, but weakened them by up to –84% at high elevations for beech, rowan, sycamore, and larch. These findings indicate widely increased drought stress, especially at lower elevations. Further, we conclude that future forest net ecosystem productivity in Central Europe will depend strongly on elevation and species composition, despite a general lengthening of the growing period for trees.

Palaeoecological changes from 580 to 1220 CE from the Indo-Burma region: A biotic assessment from the Barak Valley of Assam, northeast India

The pollen and diatom analyses of soil samples from a 80-cm deep sedimentary core from the Barak valley of Assam provides an explicit understanding of vegetation, climatic and ecological change in the Indo-Burma region from 580 CE (1370 cal. years BP) to 1220 CE (730 cal. years BP). The impact of the Medieval Warm Period (MWP) has been well documented from palynological records. Based on changes in vegetation succession, the Mean Annual Temperature (MAT) and Mean Annual Precipitation (MAP) during four pollen phases CP (1–4) were calculated using the coexistence approach. Between 580 and 760 CE (pre-MWP), the occurrence of major riparian tree pollen taxa like Barringtonia, Duabanga and Sapotaceae along with scanty diatom occurrence indicates a warm and relatively less humid climate attributable to a weak Southwest monsoon with low seasonality. This changed to a strikingly enhanced seasonality from 760 to 940 CE (beginning of MWP), indicating the establishment of the dense forest around the lake under increased warm and humid climatic conditions. During the interval from 940 to 1220 CE (MWP peak), the average values of maximum MAT and MAP were the highest recorded (≈31 °C and ≈2250 mm, respectively). From 1220 CE onwards (post MWP), the decline in arboreal pollen coincides with an exponential rise in cereal pollen clumps and shrubby pollen like Melastoma, Clerodendrum and Justicia adhatoda along with the presence of anthropogenic indicator diatom taxa like Ulnaria ulna and Gomphonema indicating increased landscape changes due to human impact under a relatively less warm and humid climate. In many parts of the world, regional data coverage pertinent to the MCA warming has now reached a point which allows compiling palaeoclimate maps for well-defined time intervals. In this direction, future studies need to address the major climatic data gaps from the Indian sub-continent especially during the last millennia.

TREE SPECIES CULTIVATION ON SUBSISTENCE AGRICULTURAL FIELDS IN NORTHWESTERN ETHIOPIA

The study was intended to identify species preferences, the relationship between livelihood status and tree planting, and the major tree growing patterns of smallholder subsistence farmers in rural Ethiopia. Data was collected through household interviews and the total enumeration of all tree species on respondents’ landholdings. A total of 23 tree species were recorded integrated within the farming landscape as boundary plantings, scattered on crop fields, around the homestead and woodlots. There was a significant difference in the mean number of trees per household across the three wealth classes. Among the three wealth classes, the medium wealth category households have a relatively higher number of tree species than rich and poor households. Considering the ever-increasing population and the resulting demand for construction poles, fuelwood, household utensils, farm implements, and the fast-growing performance of the species, Eucalyptus camaldulensis Dehnh. was the first preferred tree species to households for planting. Tree integration in the farming landscape should be recognized since it will be invaluable in developing plans for agroforestry interventions. However, exotic tree species have dominated the status of indigenous tree species. Then, there should be a continuous and detailed extension system to upgrade the traditional management system and the tree selection to be integrated.

Closing the life cycle of forest trees: The difficult dynamics of seedling‐to‐sapling transitions in a subtropical rainforest

Abstract Experimental and observational studies on seedling dynamics posit mechanisms that can influence forest diversity, structure and function. However, high mortality and slow growth of seedlings make it difficult to evaluate the importance of this life‐history filter to total tree life history. Quantifying the duration and transition of the seedling phase would help us understand this ‘black box’ in tree population biology. We used a 16‐year dataset of comprehensive seedling‐to‐sapling demography from a subtropical rainforest to construct population models that capture temporal demographic fluctuations for eight major tree species. We used data‐driven demographic models and simulations to estimate the transition ratios from newly recruited seedlings to saplings of 2‐m height and the time taken to attain 2‐m height for a newly recruited seedling conditional on its survival. Projections among species estimated that as few as 57 to more than 40,000 seedlings (with a median of 2,087) were required to make a single 2‐m high sapling. Furthermore, it would take 22–200 years (with a median of 47) for a newly recruited seedling to become a 2‐m high sapling. We found that temporal variation in demographic rates could greatly reduce the number of seedlings per established sapling, but not passage times (PTs). We also identified the importance of consistently fast growth rates for seedlings to escape the high mortality of early stages. Synthesis. Our findings demonstrate that high mortality in the very early seedling stage severely limits the probability that a newly recruited seedling will transition to the sapling stage. Although the PTs vary, we found this to be true across species with a range of life‐history strategies. Only seedlings with consistently fast growth rates are expected to pass through this life‐history filter. Findings from seedling studies should consider how short‐term studies of seedling demography might capture the rare exceptional individuals and exceptional conditions that might define the dynamics of this seedling bottleneck.

Comprehensive analysis of the R2R3-MYB transcription factor gene family in Populus trichocarpa

The MYB proteins constitute one of the most important transcription factor families in plants, and are involved in various plant-specific processes, such as development, metabolism, and stress responses. Populus is a major industrial tree species for building, papermaking, furniture, and biofuels. This study presents a systematic genome-wide analysis of the MYB family in Populus. In total, 354 genes were identified as candidate MYB genes and divided into four subfamilies, of which 196 R2R3-MYBs were then investigated further. These Populus R2R3-MYBs were classified into 45 subgroups based on comparative phylogenetic analysis with Arabidopsis thaliana, which were solidly backed by highly conserved intron/exon structures and motifs outside the MYB domain. Many types of cis-regulatory elements were detected in the promoter region, mainly related to development, light response, phytohormone response, and environmental stress response, directly reflecting the functional diversification of Populus R2R3-MYB members. Collinearity analysis revealed that purifying selection became a primary driving force during R2R3-MYB gene evolution, and that segmental and tandem duplications played critical roles in the expansion of this family in Populus. Expression profiles from publicly available RNA-Seq data and real-time quantitative PCR analysis displayed distinct expression patterns of PtrMYB genes among tissues and organs, as well as in response to drought stress. Overall, this work establishes a solid foundation for further functional dissection of MYB gene families, as well as breeding improvement for stress resistance and wood properties in Populus.

Occurrence but not intensity of mortality rises towards the climatic trailing edge of tree species ranges in European forests

AbstractAimTree mortality is increasing world‐wide, leading to changes in forest composition and altering global biodiversity. Nonetheless, owing to the multifaceted stochastic nature of tree mortality, large‐scale spatial patterns of mortality across species ranges and their underlying drivers remain difficult to understand. Our main goal was to describe the geographical patterns and drivers of the occurrence of mortality (presence of a mortality event) and the intensity of tree mortality (amount of mortality related to that mortality event) in Europe. We hypothesized that the occurrence of mortality represents background mortality and is higher in the margin than in core populations, whereas the intensity of mortality could have a more even distribution according to the spatial and temporal stochasticity of die‐off events.LocationEurope (Spain, France, Germany, Belgium, Sweden and Finland).Major taxa studiedMore than 1.5 million trees belonging to 20 major forest tree species.MethodsWe developed binomial and truncated negative binomial models to tease apart the occurrence and intensity of tree mortality in National Forest Inventory plots at the range‐wide scale. The occurrence of mortality indicated that at least one tree had died in the plot, whereas the intensity of mortality referred to the number of dead trees per plot.ResultsThe highest occurrence of mortality was found in peripheral regions and the climatic trailing edge linked with drought, whereas the intensity of mortality was driven by competition, drought and high temperatures and was scattered uniformly across species ranges.Main conclusionsWe show that tree background mortality, but not die‐off, is generally higher in the trailing‐edge populations. It remains to be explored whether other demographic traits, such as growth, reproduction and regeneration, also decrease at the trailing edge of European tree populations.

Tropical tree allometry and crown allocation, and their relationship with species traits in central Africa

Common allometric patterns have been reported across the tropics and good performance on independent data was retrieved for the most recent pantropical model predicting tree aboveground biomass (AGB) from stem diameter, wood density and total height. General models are undoubtedly useful for the estimation and monitoring of biomass and carbon stocks in tropical forests, however specific allometry, allocation, and traits, are at the core of many models of vegetation dynamics, and there is lack of such information for some regions and species. In this study, we specifically evaluated how size-dependent changes in above-ground biomass and biomass allocation to crown relate to other allometric and life-history traits for tropical tree species. We gathered destructive data available in eight terra firme forest sites across central Africa and the combined dataset consisted of 1,023 trees belonging to 54 tropical tree species phylogenetically dispersed, with only two congeneric species. A huge body of field and laboratory measurements was used for computing AGB and crown mass ratio (CMR) at the tree level, and to derive key allometric traits at the species level. For the latter, species-specific relationships between tree diameter and total height, crown exposure to light, wood density, and bark thickness were fitted for 50 species. Our results show interspecific variation in the relationships relating tree diameter to both AGB and CMR, and including species traits in a multi-specific AGB model confirmed that interspecific variation in biomass allometry is primarily determined by species wood density. We also showed that the allocation of biomass to crown increases linearly with tree diameter for most species, and that interspecific variation in the CMR model is associated with the species dispersal mode and maximum height. Trait covariations among our set of tropical tree species widespread and/or locally abundant in central Africa, revealed a continuum between large-statured species, which tended to be light-demanding, deciduous and wind-dispersed, and species with opposite attributes. Information on allometry, allocation, and traits provided here could further be used in comparative ecology and for parameterizing dynamic and succession models. Also importantly, the species-specific AGB models fitted for major tree species, including most timber species of central Africa, will help improve biomass estimates.

Community structure in different successional stages in north temperate forests of Changbai Mountains, China.

Aims The Changbai Mountains had a large area of undisturbed temperate old-growth forest that was partly destroyed by large-scale industrial logging at the turn of the 20th century and replaced by secondary forests and plantations. Our objective was to further understand ecosystem devel-opment,community composition and structure,and spatial distribution of major tree populations. Methods Three long-term 5.2 hm2 forest plots were established in secondary Populus davidi-ana-Betula platyphylla forest (PBF),secondary conifer and broadleaved mixed forest (SCBMF) and Tilia amurensis-Pinus koraiensis mixed forest (TPMF) in the Changbai Mountains following the proto-cols of the Center for Tropical Forest Science forest dynamic plot. We tagged and recorded the species,diameter at breast height (DBH),height and crown diameter of all live and dead trees with DBH 1 cm. We determined the spatial distribution of five dominant canopy tree species by pair-correlation g(r) function and performed variation partitioning analysis to estimate the environmental effect on spatial distribution. Important findings We recorded 20 949,14 725 and 12 062 live individuals and basal areas of 24.74,32.07 and 56.64 m2.hm–2 in PBF,SCBMF and TPMF,respectively. Tilia amurensis,with the overall highest importance value and basal area,was the major dominant tree species in SCBMF,P. davidianaand B. platyphylla dominated PBF and P. koraiensis dominated TPMF. In the secondary forests BPF and SCBMF,the size-class distribution of Pinus koraiensis,Acer mono,Abies nephrolepis,Picea jezoensis and Tilia amurensis showed the reverse J-shape form,whereas P. koraiensis and T. amurensis showed normal distributions in TPMF. Paired-correlation g(r) function showed that the main tree species had aggregated distributions,and the aggregation intensity decreased with the increasing distances. Environment variables had a strong effect on tree distribution,but the interpretation power of environment variables was very low in TPMF.

Pathogenicity of Sirococcus tsugae on major coniferous tree species of Belgian forest

AbstractTo evaluate the potential impact of Sirococcus tsugae on Belgian coniferous forest, a pathogenicity test was conducted through wound inoculation of two‐year‐old seedlings of different tree species. Picea abies, Pseudotsuga menziesii, Pinus sylvestris, Larix x eurolepsis as well as Tsuga heterophylla and Cedrus atlantica were inoculated with an isolate of S. tsugae collected from the only known infected site in Belgium. The tested strain proved to be highly pathogenic towards seedlings not only of two known host species of the disease (T. heterophylla and C. atlantica) but also of L. x eurolepsis. This result highlights the risk that a possible emergence of S. tsugae might represent for some important forest tree species, including species currently not known as hosts of the disease. However, as the two main coniferous tree species in Belgium (P. abies and P. sylvestris) did not appear sensitive to S. tsugae, the potential impact of the pathogen on the Belgian forest is limited.

Intra- and interspecific variations on plant functional traits along a successional gradient in a Brazilian tropical dry forest

The present study aimed to determine how plant functional traits change both at the intra- and interspecific levels along three successional stages (early, intermediate and late) in a Brazilian tropical dry forest (TDF). Plants in early-successional plots are expected to exhibit conservative traits to increase photoprotection and water conservation, whereas late successional plants would invest on acquisitive traits. Sampling was conducted in three plots of 50 × 20 m per successional stage, where plant species composition and structural parameters were previously determined for individuals with DBH ≥ 5 cm. From each of three plots, the five tree species with the highest importance values were selected. This resulted in a total of 13 species from seven families selected for this study. We quantified specific leaf area (SLA), leaf slenderness, polyphenols and chlorophyll contents, and leaf lifespan. Based on leaf traits, we detected two major tree functional species groups: the early-intermediate and the late successional groups. Confirming our expectations, the former was positively associated with drought tolerance traits (polyphenols and slenderness) related to conservative resource use; and the latter was positively associated with acquisitive traits (SLA). This pattern was partially corroborated at the intraspecific level for species that occurred in more than one successional stage. We found a weak phylogenetic signal for the functional grouping (only for polyphenols). The analysis of variance structure across scales indicated that a very small proportion (up to 2.8%) of the general variance in leaf traits occurred at intraspecific level suggesting that, compared to interspecific variations, trait differences among individuals due to phenotypic plasticity are low. Although further studies with a larger number of species are needed, our findings suggest a decoupling between functional and structural/species composition regeneration, contradicting several studies on secondary succession where species composition is regarded as the main indicator of the regeneration of ecological functions.