Slow-growing Trees Research Articles

Resilience of Pinus pinea L. Trees to Drought in Central Chile Based on Tree Radial Growth Methods

The increasing occurrence of dry and hot summers generates chronic water deficits that negatively affect tree radial growth. This phenomenon has been widely studied in natural stands of native species but not in commercial plantations of exotic tree species. In central Chile, where the species is increasingly planted, the dynamics of stone pine (Pinus pinea L.) growth under drought have been little explored. We studied the impact of drought on four stone pine plantations growing in central Chile. We sampled and cross-dated a total of 112 trees from four sites, measured their tree-ring width (RWL) series, and obtained detrended series of ring width indices (RWIs). Then, we calculated three resilience indices during dry years (Rt, resistance; Rc, recovery; and Rs, resilience), and the correlations between the RWI series and seasonal climate variables. We found the lowest growth rate (1.94 mm) in the driest site (Peñuelas). Wet conditions in the previous winter and current spring favored growth. In the wettest site (Pastene), the growth rates were high (4.87 mm) and growth also increased in response to spring thermal amplitude. Overall, fast-growing trees were less resilient than slow-growing trees. Drought reduced stone pine stem growth and affected tree resilience to hydric deficit. At the stand level, growth rates and resistance were driven by winter and spring precipitation. Fast-growing trees were more resistant but showed less capacity to recover after a drought. In general, stone pine showed a high post-drought resilience due to a high recovery after drought events. The fact that we found high resilience in non-native habitats, opens new perspectives for stone pine cropping, revealing that it is possible to explore new areas to establish the species. We conclude that stone pine shows a good acclimation in non-native, seasonally dry environments.

THE PERSPECTIVITIES OF MICRICLONAL PROPAGATION OF ACER PLATANOIDES L. CRIMSON KING (ACEARCEAE JUSS.)

Clonal micropropagation – massive asexual propagation of plants from cell and tissue culture; the resulting plants are genetically identical to the original copy. The conservation of plants by tissue culture methods is of great interest and will probably become even more common in the future. The advantages of this method are numerous, but we find it most important that the initiation of cultivation requires only a single plant, a seed or a single explant (apex, meristem, bud, piece of leaf, stem etc.), thus, the available plant specimens (which can be only a few) will not be affected by harvesting them from their habitat. The state program “Developing of the scientific basis for the sustainable reproduction of valuable specimens of the botanical garden collection in in vitro culture” is being conducted in the laboratory of biotechnology of the Tashkent Botanical Garden of the Institute of Botany, Academy of Sciences of the Republic of Uzbekistan, directed at microclonal propagation of many valuable species presented in a single copy, as well as species in demand in urban greening programs. Acer platanoides L. Crimson King variety (Acearceae Juss.) is a deciduous, slow-growing tree, reaching 15 m with age. The crown shape is wide-round and even. The leaves are large, 5-7 lobed, deep purple, and do not change color throughout the growing season. The trunk is smooth, dark in color, with clearly defined longitudinal grooves. Because of its graceful shape, the Crimson King variety is extremely popular. It is actively planted in city yards, parks, and roadsides. Suitable for landscaping. Within this state program the protocol of microclonal propagation of A. platanoides Crimson King variety has been developed to propagate this species for Botanical Garden collection as well as for greening programs. Solutions of sodium hypochloride (4-6%), hydrogen peroxide (2-15%), silver nitrate (0.01%), Tween20, ethanol (70%), and some other sterilizing agents were tested for developing a protocol for sterilization of maple explants. “Belizna” solution, “Domestos” sterilizing soap, fungicides difenoconazole, mancoseb and metalaxyl, fludioxonil, propiconazole, antibiotics streptomycin, amoxicillin, gentamicin, and etc. were also implemented for explants sterilization. As a result of the studies, it was determined that the most optimal source of explants are branches with apical (10% regeneration) and lateral (100% regeneration) buds of the annual shoot of A. platanoides Crimson King variety. Plant growth environment is important in the success of in vitro propagation. Thus, explants obtained from trees growing in the arid areas of massive Kuylyuk in Tashkent, were characterized by low viability and a high degree of infection with fungal diseases in comparison with explants obtained from trees growing in Hastimom Square in Tashkent, where trees are watered daily. We found two ways of in vitro propagation of A. platanoides L. variety Crimson King: 1. With the use of microcuttings. 2. Indirect organogenesis with induction of callus. The best way for A. platanoides L. variety Crimson King became indirect organogenesis trough induction of the callus in the WPM - Wood Propagation Media, hormone free or with 6- benzilaminopurine in the media. The duration of the developing of a plant usually takes 6-9 months.

The timing of wood formation in peatland trees as obtained with different approaches

Dendrometers offer valuable insights into how tree growth responds to climatic variables and physiological processes over the course of a year. Yet, their applicability to extremely slow-growing trees, such as those in peatlands, has been limited due to the intricate and slow nature of growth, therefore rendering interpretation of results complex. In this study, we conducted a comprehensive monitoring of tree wood formation in both peatland and mineral soil ecosystems in southern Sweden (58.37 N, 12.17 E, 75 m asl) in 2021 and 2022, using both band and point dendrometers. To verify and validate the dendrometer data, we also sampled microcores every two weeks during both growing seasons. We find that peatland trees grow at approximately 30 % the rate of their neighbors on mineral soils. The onset of growth among peatland trees typically occurs between mid-May and early June, consistently lagging the start of the growing season in trees on mineral soils by one to three weeks. Notably, growth peaks are synchronized across peatland trees and coincide with the summer solstice. Both types of dendrometers exhibit varying degrees of accuracy depending on the phenological stages measured. They perform well in identifying growth onset and peak but are less effective at detecting growth cessation. Point dendrometers demonstrate superior accuracy as they better capture daily irreversible growth increments. In the case of band dendrometers, growth increments are obscured by greater reversible fluctuations in dead bark tissues. However, they remain valuable for tracking the wood phenology of trees with growth rates exceeding 2 mm/year. Based on our results, for an effective tree monitoring in peatlands, we strongly recommend (1) using point dendrometers and (2) removing the dead bark tissues on monitored trees.

Effects of Thinning on Carbon Storage in a Mixed Broadleaved Plantation in a Subtropical Area of China

Forest thinning is a widely used silvicultural method in forest management and has complex effects on carbon sequestration in different types of forest ecosystems. The present study examined the short-term effects of different thinning intensities on carbon storage in an 11-year-old mixed broadleaved plantation. The results partially supported that different thinning intensities have varying impacts on carbon storage in different parts of forest ecosystems. The main results were as follows: (1) The effect of thinning on promoting the growth of fast-growing tree species (Michelia macclurei Dandy and Schima superba Gardn. et Champ.) was earlier than that of slow-growing tree species (Castanopsis hystrix Miq.). (2) A greater thinning intensity conferred greater effects on promoting the tree biomass carbon growth, litter carbon storage, and understory plant diversity, in the order of 41%~50% > 31%~40% > 20%~30%, but these values were lower than those for the unthinned plots. (3) The soil carbon storage declined most in the 41%~50% thinned plots, due to the reduced carbon storage in the humus layer. (4) The 20%~30% thinning intensity promoted carbon sequestration in the short term in the mixed broadleaved plantation. The results suggested that a lower thinning intensity promoted carbon sequestration in the short term, a greater thinning intensity reduced carbon storage at first, but the negative effect on carbon storage exhibited trade-offs later by the growth of tree and understory plant biomass carbon and the accumulation of litter layer carbon.

Keanekaragaman Fungi Mikoriza Arbuskula pada Tegakan Kelicung (Diospyros macrophylla Blume) di KHDTK Rarung, Lombok Tengah

Kelicung tree (Diospyros macrophylla) is a native tree species of West Nusa Tenggara. It is a slow-growing tree with very good wood ornament, strength, and durability properties. Symbiotic mutualism between kelicung and mycorrhiza has not been documented. Mycrorrhiza is a mutualism symbiosis between fungi and plant roots that could improve plant growth due to increase nutrient and water absorbtion. Therefore, the objective of this study is to investigate mycorrhizal symbiosis in kelicung roots. Soil and root samples were taken in the Rarung Special Purpose Forest Area at 0 – 20 cm depth. Isolation and identification of arbuscular mycorrhizal fungi used screening and centrifugation methods to identify spore density, diversity, abundance, and frequency. Furthermore, root staining and colonization of arbuscular mycorrhizal fungi were carried out by observing the structure of vesicles, arbuscules, hyphae, and spores on Kelicung roots. The research results showed that the average number of spores found was 846 spores/50 g of soil. Spores were identified in two genera: Glomus sp and Acaulospora sp. Glomus spores found were round, the colour of the spores was yellow, the spores did not react when Melzer's solution was dropped, and the spore walls of the Arbuscular mycorrhizal fungi of the genus Glomus consisted of 1-2 layers of cell walls. Observation of root colonization, no structures of root arbuscular mycorrhizal fungi were found in Kelicung.
 Keywords: Acaulospora sp., Arbuscular mycorrhizal fungi, Diospyros macrophylla, Glomus sp., Kelicung

'Persistent germinal center responses: slow-growing trees bear the best fruits'.

Germinal centers (GCs) are key microanatomical sites in lymphoid organs where responding B cells mature and undergo affinity-based selection. The duration of the GC reaction has long been assumed to be relatively brief, but recent studies in humans, nonhuman primates, and mice indicate that GCs can last for weeks to months after initial antigen exposure. This review examines recent studies investigating the factors that influence GC duration, including antigen persistence, T-follicular helper cells, and mode of immunization. Potential mechanisms for how persistent GCs influence the B-cell repertoire are considered. Overall, these studies provide a blueprint for how to design better vaccines that elicit persistent GC responses.

Monitoring of the condition of woody plants in the central part of the city of Donetsk

The dendroflora of Donetsk has been studied the species composition of trees in stands has been determined, the age structure of plantings has been analyzed, the life condition of green spaces has been assessed, as well as morphometric parameters of trees have been evaluated and models of age dependences of the allometric coefficient of trees, characterized by high indicators of adequacy to the initial data, have been proposed for the first time. As part of the linear plantings of the surveyed streets, 45 species of trees were identified, including 13 species of the indigenous fraction of the local flora belonging to 24 genera and 17 families. Dominant are Populus bolleana Lauche, Acer platanoides L., Betula pendula Roth, Acer pseudoplatanus L., Robinia pseudoacacia L., Aesculus hippocastanum L. and Picea pungens Engelm. The plantings are dominated by species of European (48,85%), North American (22,49%) and Central Asian (18,02%) origin. The most numerous in trees is the age group of 4049 years. The vital condition of 41% of trees with a fast and medium growth rate is assessed as good with minor signs of weakening, and 59% of plants are marked as severely weakened or dying. For slow-growing trees, 91% of the sample consists of healthy plants with minor signs of weakening.

Effect of radial growth rate on wood properties variation of Sentang (Azadirachta excelsa) tree planted in Kelantan, Malaysia

Properties of Sentang wood planted in Kelantan, Malaysia, were studied, focusing on the effect of radial growth rate on variation in the fiber and vessel element dimensions, moisture content, density, shrinkage, bending, and compression strength at the breast height of the tree. The trees were categorized into slow-, average-, and fast-growth categories, based on their breast height diameter and standard deviation. The variations in properties were then examined from the pith to the bark. The fiber length and diameter tend to decrease until a certain distance from the pith, followed by an increase toward the bark. Contrastingly, the vessel element length and diameter tend to increase until a maximum size is reached and then exhibit a relatively constant size toward the bark. The fast-growing trees tended to have longer and larger fibers, while the slow-growing trees tended to have longer and larger vessel elements. In addition, the fast-growing trees tended to have a higher green moisture content and shrinkage, lower density, lower modulus of rupture (MOR), and lower compression strength. The results revealed that growth rate seems to influence the modulus of elasticity (MOE) less than the MOR and compression strength.

Dendrochronology and dendroclimatology of yew in Poland

This study concerns dendrochronology and dendroclimatology of yew growing in Poland. The yew (Taxus baccata L.), a long-lived, slow-growing tree, is regarded as a species threatened with extinction. The eastern boundary of its range transects Poland. The analyses were performed on 34 yew populations which are protected as parts of nature reserves, as nature monuments, or which are planned to be protected. Samples were collected using Pressler borer from a total of 774 trees yielding 1307 profiles. Classical dating techniques (including cross-dating method) were subsequently used to reconstruct 34 local chronologies. Average tree-ring width was 0.84 mm and ranged from 0.27 to 1.47 mm. For most stands, the age of the yew trees is overestimated. The studied populations most frequently are 100–200 years old, and the oldest yew trees in Poland are growing in the KS population (age estimated at 500–600 years). Average tree-ring width was found to be strongly dependent on the chronology length/tree age. The 674 pointer years calculated for the local chronologies served as a basis for determining pointer years for the entire study area. Negative years include: 1862, 1865, 1917, 1927, 1940, 1947, 1956, 1963, 1969, 1976, 1979, 1993, 1996, and 2003. Positive years are: 1884, 1914, 1916, 1965, 1977, 1988, 1997, and 2007. Analysis of weather conditions in those years demonstrated a strong relationship between tree-ring width and air temperature in winter, pre-spring, and early spring. Higher-than-average temperatures during those seasons correlate positively with yew tree-ring width. Response function analysis performed for local and regional chronologies point to a dominant role of air temperature in December of the year preceding growth and in January, February, and March of the current year (linear relationships). June precipitation is an additional factor affecting tree-ring width in some areas of northern and northwestern Poland: the higher the precipitation, the wider the tree-rings. The results obtained, particularly those concerning growth-climate relationships and dendroclimatic regionalisation, can be used in the on-going programme of yew restitution in Poland.

Isolation and Characterisation of Plant Growth-Promoting Bacterial and Fungal Endophytes from Himalayan Yew (Taxus wallichiana) - An Economically Imperative Plant of Himalayas

It is a known fact that the bacterial and fungal endophytes inhabit the plant tissues besides aiding in the better growth and health of the plants. The bark and leaves of Taxus wallichiana have drawn a lot of interest in recent years since they are the richest source of taxol, an anticancer drug. As it is a slow-growing tree that can only be regenerated via vegetative propagation, it has been classified as a critical rare species due to its extensive collection for medicinal and other purposes. Nonetheless, the use of endophytes as plant growth promoters is gaining much importance among environmentalists and agronomists because of their imperative role in crop production. Even then, there is hardly any information available regarding the growth-promoting endophytes isolated from bark and leaves associated with T. wallichiana commonly known as Himalayan Yew. Therefore, the present study was undertaken to isolate fungal and bacterial endophytes from T. wallichiana and to classify the growth-promoting properties of these endophytes. In total, seven fungal and ten bacterial endophytes were obtained from different parts of T. wallichiana. All of the isolated fungal and bacterial endophytes produced indole acetic acid while most of them also produced ammonia. Besides, the fungal and bacterial endophytes were also screened for antimicrobial and various enzymatic activities. Based on the above results, the two fungal endophytes were selected for their possible ability to promote seed growth. The results showed that the fungal endophytes isolated from T. wallichiana played an active role in increasing growth in other plant species and therefore, can be used as potential plant growth promoters.

Long-term soil water limitation and previous tree vigor drive local variability of drought-induced crown dieback in Fagus sylvatica

Ongoing climate warming is increasing evapotranspiration, a process that reduces plant-available water and aggravates the impact of extreme droughts during the growing season. Such an exceptional hot drought occurred in Central Europe in 2018 and caused widespread defoliation in mid-summer in European beech (Fagus sylvatica L.) forests.Here, we recorded crown damage in 2021 in nine mature even-aged beech-dominated stands in northwestern Switzerland along a crown damage severity gradient (low, medium, high) and analyzed tree-ring widths of 21 mature trees per stand. We aimed at identifying predisposing factors responsible for differences in crown damage across and within stands such as tree growth characteristics (average growth rates and year-to-year variability) and site-level variables (mean canopy height, soil properties).We found that stand-level crown damage severity was strongly related to soil water availability, inferred from tree canopy height and plant available soil water storage capacity (AWC). Trees were shorter in drier stands, had higher year-to-year variability in radial growth, and showed higher growth sensitivity to moisture conditions of previous late summer than trees growing on soils with sufficient AWC, indicating that radial growth in these forests is principally limited by soil water availability. Within-stand variation of post-drought crown damage corresponded to growth rate and tree size (diameter at breast height, DBH), i.e., smaller and slower-growing trees that face more competition, were associated with increased crown damage after the 2018 drought. These findings point to tree vigor before the extreme 2018 drought (long-term relative growth rate) as an important driver of damage severity within and across stands. Our results suggest that European beech is less likely to be able to cope with future climate change-induced extreme droughts on shallow soils with limited water retention capacity.

Characterizing Seasonal Radial Growth Dynamics of Balsam Fir in a Cold Environment Using Continuous Dendrometric Data: A Case Study in a 12-Year Soil Warming Experiment

Historical temperature records reveal that the boreal forest has been subjected to a significant lengthening of the thermal growing season since the middle of the last century, and climate models predict that this lengthening will continue in the future. Nevertheless, the potential phenological response of trees to changes in growing season length remains relatively undocumented, particularly for evergreen boreal tree species growing in cold environments. Here, we used the recently defined zero growth (ZG) concept to extract and characterize the metrics of seasonal radial growth dynamics for 12 balsam fir trees subjected to a 12-year soil warming experiment using high resolution radius dendrometer measurements. The ZG concept provides an accurate determination of growth seasonality (onset, cessation, duration, growth rates, and total growth) for these slow-growing trees characterized by significant shrinkage in tree diameter due to dehydration in the winter. Our analysis revealed that, on average, growth onset starts at day 152 ± 7 (±1 SE, 31 May–1 June) and ceases at day 244 ± 27 (31 August–1 September), for a growing season duration of about 3 months (93 ± 26 days) over a 12-year period. Growing season duration is mainly determined by growth cessation, while growth onset varies little between years. A large part (80%) of the total growth occurs in the first 50 days of the growing season. Given the dynamics of growth, early growth cessation (shorter growing season) results in a higher average seasonal growth rate, meaning that longer growing seasons are not necessarily associated with greater tree growth. Soil warming induces earlier growth cessation, but increases the mean tree growth rate by 18.1% and the total annual growth by 9.1%, on average, as compared to the control trees. Our results suggest that a higher soil temperature for warmed trees contributes to providing better growth conditions and higher growth rates in the early growing season, when the soil temperature is low and the soil water content is elevated because of snowmelt. Attaining a critical soil temperature earlier, coupled with lower soil water content, may have contributed to the earlier growth cessation and shorter growing season of warmed trees.

Development of a Climate-Sensitive Matrix Growth Model for Larix gmelinii Mixed-Species Natural Forests and Its Application for Predicting Forest Dynamics under Different Climate Scenarios

Larix gmelinii natural forests, which are of great ecological and economic importance, are mainly distributed in northeast China. Sustainable management of these forests play a vital role in ecological security in northeast China, especially in the context of climate change. Forest growth models, which support forest management decision-making, are lacking for Larix gmelinii natural forests, hampering the prescription of forest management strategies. In this study, we produced a climate-sensitive, transition-matrix model (CM) for Larix gmelinii natural forests. For comparison, a variable transition model without including climate change effects (NCM) and a fixed-parameter model (FM) were also built. We examined the performance of the CM, NCM, and FM by conducting short- (5 years) and long-term (100 years) simulations. The results showed that for short-term prediction, no significant difference was observed among the three predictive models. However, the long-term prediction ability of the CM under the three different RCPs was superior to that of the FM and NCM. The number of trees and basal area were predicted to increase under climate change, which might result in natural disasters, such as snow break, windthrow, and forest fire. Silvicultural practices, such as reducing the intermediate thinning interval and the enrichment planting of slow-growing trees, should be implemented to mitigate the deleterious effects of climate change.

A Band Model of Cambium Development: Opportunities and Prospects

More than 60% of tree phytomass is concentrated in stem wood, which is the result of periodic activity of the cambium. Nevertheless, there are few attempts to quantitatively describe cambium dynamics. In this study, we develop a state-of-the-art band model of cambium development, based on the kinetic heterogeneity of the cambial zone and the connectivity of the cell structure. The model describes seasonal cambium development based on an exponential function under climate forcing which can be effectively used to estimate the seasonal cell production for individual trees. It was shown that the model is able to simulate different cell production for fast-, middle- and slow-growing trees under the same climate forcing. Based on actual measurements of cell production for two contrasted trees, the model effectively reconstructed long-term cell production variability (up to 75% of explained variance) of both tree-ring characteristics over the period 1937−2012. The new model significantly simplifies the assessment of seasonal cell production for individual trees of a studied forest stand and allows the entire range of individual absolute variability in the ring formation of any tree in the stand to be quantified, which can lead to a better understanding of the anatomy of xylem formation, a key component of the carbon cycle.

Effects of culture medium type and plant growth regulators on in vitro culture of Sorbus persica Hedl.

Sorbus persica Hedl. is an Iranian endemic slow-growing tree (fam. rosaceae) and is endangered. It is important in terms of the gene storage, environmental protection, and medicinal uses. To in vitro propagate this species by the lateral bud culture, a factorial experiment was conducted in a completely randomized design in three levels of culture medium and three levels of cytokinin with three replications. For shooting, the DKW, WPM, and MS culture media containing the cytokinins BAP, Kin, and 2ip, and for rooting, the complete and modified DKW, WPM, and MS culture media containing the auxins NAA and IBA separately and in a consecutive application were investigated. The results showed that the best sterilization treatment was a consecutive application of sodium hypochlorite 20% (v/v, 15 min) and mercuric chloride 0.1% (3 min) in summer. The best proliferation and longitudinal growth of shoots was observed in the MS medium containing IBA (0.01 mg l-1), Kin (0.25 mg l-1), and BAP (3 mg l-1) growth regulators. Also, the best rooting was obtained in the DKW medium with a quarter of the concentration of macroelements containing the NAA+IBA hormones (0.3+0.3 mg l-1).

Tropical forest water source patterns revealed by stable isotopes: A preliminary analysis of 46 neighboring species

Stable isotope tracing of plant water use can illuminate plant water sources. But to date, the number of species tested at any given site has been minimal. Here, we sample 46 tropical hardwood tree species in a 0.32 ha plot with uniform soils. Soil water was characterized at 6 depths at 0.2 m intervals down to 1 m and showed simple and predictable depth patterns of δ2H and δ18O, and simple and spatially uniform isotope composition at each depth. Nevertheless, tree xylem water δ2H and δ18O showed remarkable variation covering the full range of soil composition, suggesting strong sorting and niche segregation across the small plot. Wood density, tree size and mean basal area increment together explained approximately 55% of the variance of xylem water isotope composition through principal component analysis. A Bayesian mixing model was applied to the data and showed that sampled trees were either sourcing their water from very shallow or deep soil layers, with very little contribution from the middle portion of the soil profile. The majority of the observed species relied on 0.0–0.2 m depth soil water. This layer contributed approximately 75% of the xylem water which was significantly higher than the contributions from all other depths. The contribution from shallow soil was highest for trees with high wood density, slow-growing trees and small-sized trees. Our work suggests that stable isotope tracers may aid a better understanding of tropical forest water uptake depths and their relation to tree functional traits and potential hydrological niche segregation among co-occurring tropical species.

A Comparison of Tree Growth in Two Sites near Schefferville, Quebec

This aim of this study is to determine if there are differences in tree growth between two sites near Schefferville, Quebec (located at 54°48′N,  66°50′W): the Ephemeral Lake and Airport Woodland site. Tree core samples were collected in order to determine if the “stressed” condition might make a difference in the growth of the trees within the site, and to evaluate how trees may adapt to particular conditions. Cores were collected from 20 trees in the 100x100 meter stressed site, Ephemeral Lake. Core samples were taken from 30 trees located in the in the 10x10 meter ideal site, Airport Woodland.Analysis of the tree cores showed that that there was no statistically significant difference in rate of trunk circumference (or diameter) growth, but rather, both the stressed and ideal forests displayed nearly identical growth rates. This seems to indicate that trees in both plots had similar amounts of water to facilitate their annual growth rate. However, average tree height and average vertical growth per year are highly statistically significant, and are thus found to be key factors. Trees in the stressed forest grow slower upwards (but not in thickness) than trees in the ideal forest, and they reach lower total height—by a factor of almost two—than trees in the ideal forest.If we assume, for example, that the stressed forest under study constitutes a random sample of trees that, in a sense, comes from a population of “all stressed forests,” and similarly for the “ideal forest,” then we may conclude that stressed forests—ones exposed to heavy winds and facing unreliable water supply—tend to produce shorter and slower-growing trees than do forests under “ideal” conditions. Equally, the non-significance of the width-growth variable can indicate that it is not necessarily true that tree-width and tree-width-growth-rate are adversely affected by stressed environment.On the other hand, there were differences in the heights—or lengths of trunks—of trees in the two groups. First, trees in the stressed group were less likely to be growing vertically. About half of the trees in the stressed group were tilted or growing with their main trunk underground. The trees in the ideal group, on the other hand, were nearly all growing vertically, with only a single tree identified as “slanted” rather than “straight.” Also, the trees in the stressed group grew upward at a slower rate than those in the ideal group, and displayed lower overall heights.&nbsp

Nitrogen accumulated and biologically fixed by uninoculated Anadenanthera peregrina (L.) Speg trees under monospecific stands in the Atlantic Forest biome

Nitrogen-fixing legumes are widely used to improve ecosystems. However, N accumulation in biomass, N2 amounts biologically fixed, and the effects on soil N status are poorly understood for plantations with slow-growing N2-fixing legume trees in seasonally dry environments. In this study, we assessed these questions in monospecific stands of uninoculated Anadenanthera peregrina (L.) var. peregrina (angico) trees established in the Atlantic Forest biome. Nine experimental plots with a stand density of 1111 tree ha−1 were examined about five to six years after tree planting. N content in the leaves, branches, bark, and wood was estimated using allometric equations and N concentration in the tissues. To assess the N content, the topsoil layer was sampled in each plot and in one pasture area. The annual N2 fixation rate at the stand scale was estimated by the natural abundance of 15N, using leaves of angico and a mix of leaves of herbs and shrubs growing in the understory in each plot. N accumulation in aboveground biomass was estimated at 260 kg ha−1 and N allocated in the leaves and branches was four-fold that in the tree stem. N derived from biological N2 fixation was estimated at 50% on average, with an annual rate of N fixed in the aboveground biomass of 22 kg ha−1 year−1. Soil N storage was similar between A. peregrina stands and the pasture area at six years after planting. Long-term gains of N2 fixation may be greatly improved by the adoption of breeding programs for this slow-growing species and the use of an adequate rhizobium strain.

Interaction between stem damage, crown vitality and growth performance of European yew in Central–East Europe

Abstract As long-lived, slow-growing tree species, European yew (Taxus baccata L.) has considerable potential for dendrochronological use. The increasing probability of decline and the worsening of yew health status endanger the species diversity of temperate forests. In 2015–2017, we sampled adult yew populations with scattered occurrence in limestone beech forests (Fagetum dealpinum), in which yew trees exhibit the top growth performance. Altogether, 150 trees were sampled (294 cores) at four localities. By using the general linear model, we investigated the interactions between stem and crown status, sex and growth performance of yew trees. Based on the previous results and innovative measures of competition and canopy closure, we explored the promotion of silviculture care for female over the male trees and formulated exact release cutting rules. The results demonstrate divergent growth trends between male and female trees and the pronounced negative effects of crown and stem damage on growth performance of European yew. Expected decreases in radial growth of damaged female trees in comparison with male ones is less confirmed. Despite this, making silvicultural treatments for females as a priority is recommendable. Our findings can improve the effectiveness of forest management and restoration activities in European temperate forests, where yew adults are threatened by the higher degree of shading and herbivory pressure.

The potential for using rare, native species in reforestation– A case study of yews (Taxaceae) in China

Ecosystem restoration is regarded as one of the most cost-effective ways of mitigating the effects of the ongoing climate- and anthropogenic changes and slow or revert the loss of biodiversity. Forest restoration has much potential to conserve forest specialist species and ecosystem services, by using multiple, native tree species to promote a high local diversity of trees, with likely positive effects on overall biodiversity and on ecosystem resilience. In this study, we assessed the potential of using two rare, native species of the yew family (Taxaceae) in forest restoration in China. Species of this family are only rarely used in reforestation despite their potential contribution to tree functional diversity as long-lived, shade-tolerant, evergreen understory trees with fleshy seed cones of value to frugivorous animals. By using species distribution modelling methods, we analysed national and local scale occurrence data for Taxus cuspidata and Torreya grandis to determine the climate-based potential ranges as well as important factors for growth on a local scale. The analyses showed that both species have large potential ranges driven mainly by precipitation and by comparing these ranges with the areas that have potential for sustaining forests, we found large areas available for forest restoration where these species could be included. On the local scale, we found that low light levels and low competition from co-occurring trees are more important for the growth of seedlings compared to the adult individuals of both species. If the ecological requirements for seedlings are ensured, i.e. by creating moderately shaded environments in which seedlings can escape competition, both Taxaceae species have high potential for reforestation in China and will increase the ecological qualities of a restored forest, and at the same time, the conservation of rare tree-species in their native ranges is ensured. Conclusively, both Ta. cuspidata and To. grandis are shade-tolerant, slow-growing trees that, by creating an evergreen scrubby layer, add to forest structural complexity and stability, thereby helping support ecosystem services and biodiversity, e.g. microhabitat and resources for birds and other animals.