Annual Growth Rings Research Articles

Ring-forming plants in the Egyptian deserts

The formation of annual growth rings is an imperative requirement for studying the dendroecological potential of plant species. Little is known about the distinctness of growth rings in the wood of desert plants in Africa, particularly in southern Mediterranean regions. To fill this knowledge gap, we collected and anatomically analyzed about 300 perennial desert plants from different areas in Egypt. Out of the 300 studied plant species, 94 species were identified as growth-ring forming plants. They belong to 78 genera and 33 families. Trees, shrubs/subshrubs, and perennial or short-lived herbs are represented by 7, 55, and 32 species, respectively. Trees and shrubs represent 7.4% and 58.5% of the total, respectively. The distinctness of growth rings in these species was indicated either by the type of wood porosity, fibers, marginal parenchyma layers or by a mixture of these characteristics. Ring porosity, fiber layer, and parenchyma were the main indicators for growth-ring distinctness in 77.7%, 60.6%, and 33.0% of growth-ring forming plants, respectively. We conclude that some of the desert plants form distinct growth rings depending on site conditions, while precipitation is the main driver for its formation. Further studies on the annual rhythm of xylem formation are required to confirm the annual nature of growth rings and potential dendroecological use of these plants.

Recruitment and growth dynamics of a temperate forest understorey species following wildfire in southeast Australia

In southeast Australia, fire regimes are changing. Conserving species into the future under these changing fire regimes will require understanding their recruitment and growth dynamics following historical fires. Where monitoring is absent, dendroecology provides a tool for reconstructing and quantifying these dynamics. The use of dendroecology in southeast Australia has been limited due to presumptions that many of the species do not produce annual growth rings. In this study, we determined the dendroecological potential of a fire-sensitive understorey tree species, Pomaderris aspera, as a case study species, to explore the potential to use of understorey species to provide insights into past fire history. We used growth patterns of this species to understand the role of resource limitation on growth and senescence. We found that P. aspera had distinct growth rings and high within tree correlation when cross-dated.Recruitment events of this species aligned with three known fire events. We found that the impacts of historical fire on tree canopy cover could be estimated. P. aspera grew rapidly post fire and then become suppressed within 9–15 years. Cycles of growth release and suppression were found with increasing incidence of suppression occurring over time. Increased suppression and reduced growth rates aligned with patterns of recorded senescence over time in the understories of a maturing.Eucalyptus canopy. Our results highlight the potential to use dendroecology to confirm past fire extents and amount of canopy disturbances and the impacts that these events have on the recruitment and growth dynamics of understorey species in southeast Australia.

Wood hydrosystem of three cultivars of Vitis vinifera L. is modified in response to contrasting soils

In Vitis vinifera L., the same genotype can express different phenotypic characteristics depending on the environmental conditions, e.g. soil deepness. Wood anatomy, specifically xylem vessel traits, provide information about the plant’s eco-physiological responses to the environment. Slight changes in vessel diameter and density may impact plant hydrosystem functionality, since large vessels are more efficient in the volume of transported water compared to narrower ones, although the latter are more effective in avoiding stress-induced embolism. The aim of this study was to analyze variations in the wood hydraulic structure of three grapevine cultivars, induced by soils with strong contrast in depth, texture and rock volume, providing evidence of their adaptative capacities. Anatomical and growth traits of each annual growth ring were measured in 8-year-old plants of Bonarda, Malbec and Tempranillo cultivars growing in contrasting depths of soils. Bonarda exhibited no differences in wood productivity between soils with different depths, showing the ability to modulate the earlywood vessel lumen area. Malbec and Tempranillo did show differences in wood productivity between the two types of soils, with major changes in the trade-off between vessel density and lumen area in Tempranillo, while in Malbec there were few changes in the vessel traits. Xylem hydraulic characteristics of the grapevine stems varied in response to soil environment and cultivar. This knowledge may help to select management strategies in areas of soil heterogeneity.

The usability of Cupressus arizonica annual rings in monitoring the changes in heavy metal concentration in air.

Air pollution, which has been increasing in recent years, has reached significant dimensions and has become one of the most important agenda topics of present day. Among air pollution components, heavy metals are of particular importance, since they are not easily decomposed, they tend to bioaccumulate, and some of them have toxic or carcinogenic effects even at low concentrations. Therefore, it is an extremely important subject to monitor the changes in heavy metal concentrations found in air. The most preferred method in determining the changes in heavy metal concentrations in the atmosphere is the use of biomonitors. From past to present, trees have been good biomonitors in determining the increase in heavy metal concentrations in the atmosphere. Particularly, with the help of the annual growth rings of trees, vital information can be obtained on the changes in heavy metal concentrations in air. In this study, after the annual rings were determined on the log taken from the main body of the cypress (Cupressus arizonica) tree cut from the Kisla park located in Kastamonu province, the concentrations of Bi, Cd, and Ni in the outer bark, inner bark, and wood were compared in the inward-facing and road-facing parts of these sections. Also, the changes in heavy metal concentrations in the annual rings were evaluated on a yearly basis. As a result of the study, it was found that the element concentrations in the outer bark of the road-facing part were generally at a higher level, and that the changes in the elements on a yearly basis generally followed a fluctuating course, but there had been a general increase in the Cd and Ni concentrations in recent years.

Electing drought-resistant pinus pinea L. (stone pine) using dendroclimatology

The purpose of this study is to determine the exceptional dry years of Pinus pinea L. (stone pine) by using dendroclimatology, and Selection drought-resistant trees depending on the differentiation in the width of the annual growth rings of exceptional dry years and adopting them as seed mothers. Method. Sixteen samples were taken from four different sites (A, B, C, and D) (four samples per site). Cores were extracted from 10 trees per sample and the transverse surfaces of all cores were smoothed to expose the tree rings. Cores were then scanned and annual ring widths were measured from 2019 to 2005 using ScopeImage Plus software. By using the Moving Average as a smoothing technique, the exceptional years of the time series for the width of the annual growth rings for each sample were determined. More specifically, results show that 2008 and 2014 are negatively exceptional years across all the sites. Furthermore, the correlation coefficients between the ring-widths, the annual precipitation, and temperature for each site show that the annual precipitation is the determinant of the occurrence of exceptional years and that 2008 and 2014 are the dry years in our chosen sites. When comparing the ring widths of the dry years, it was noticed that tress (Aa4, Ab6, Ac9, Ad2) in the site A, (Ba10, Bb1, Bc3, Bd1) in the site B, (Ca9, Cb5, Cc8, Cd1) in the site C and (Da1, Db3, Dc7, Dd3) in the site D are superior and have wide rings. Scientific novels. According to this study, these trees can be selected as drought-resistant and adopted as seeds mothers which can be used in the propagation of Pinus pinea.

Annual radial growth and climatic response of Quercus crassifolia bonpl. in northwestern Durango, Mexico

The oak species Q. crassifolia produces reliable annual rings with better climatic sensitivity than many conifer species commonly used for hydroclimatic reconstructions in Mexico. Most dendrochronological research in Mexico has been done with conifers, but broadleaf species have been underutilized. Mexican oaks are found among those species receiving limited attention for dendrochronological purposes, despite Mexico being a primary center of oak diversity with over 160 species. The objectives of this study were: (1) date the annual radial increments of oaks (Quercus crassifolia Bonpl.), and (2) analyze the dendrochronological potential and climatic response of the species to reconstruct historical climatic variability and the influence of ocean–atmospheric modes. The study was located at the Barajas site, municipality of Tepehuanes, Durango, Mexico. Wood samples consisted of 60 cross sections, 30 of them obtained at the base of the stem, and 30 more ca. 20–30 cm above the first cross section, which were analyzed by dendrochronological techniques. A tree-ring width chronology 177 years long (1840–2016) was developed indicating suitable values of series intercorrelation (0.52), mean sensitivity (0.26), signal-to-noise ratio (8.98), first-order autocorrelation (0.21), rbar (0.28), and expressed population signal (0.86) for the period 1890–2016. Dendrochronological parameters were similar or superior to those obtained from conifer species in the region. The chronology shows the strongest relationship with October–May precipitation, explaining ca. 60% of its variability (1951–1984, r = 0.78, p < 0.01), but a negative response to the average seasonal October–May temperature (1902–2016, r = -0.50, p < 0.01). The annual growth rings of Q. crassifolia showed a negative association (1890–1977, r = – 0.67, p < 0.01) with the El Nino-Southern Oscillation (reconstructed Southern Oscillation Index), and positive with the Pacific Decadal Oscillation Index (1948–2015, r = 0.39, p < 0.01, the reconstructed Palmer Drought Severity Index (1890–2012, r = 0.73, p < 0.01), and the seasonal winter–spring Standard Precipitation Index (1890–2016, r = 0.76, p < 0.01).

Quantitative assessment of the oxygen isotope composition of fish otoliths from Lake Mungo, Australia

AbstractThe Willandra Lakes region is a series of once interconnected and now-dry lake basins in the arid zone of southeastern Australia. It is a UNESCO World Heritage Site of cultural, archaeological, and geological significance, preserving records of Aboriginal occupation and environmental change stretching back to at least 50 ka. Linking the archaeology with the commensurate palaeoenvironmental information is complicated by the millennial time spans represented by the past hydrological record preserved in the sediment vs. the subdecadal evidence of each archaeological site. Oxygen isotope records across annual growth rings of fish otoliths (ear stones) can elucidate flooding and drying regimes on subannual scales. Otoliths from hearth sites (fireplaces) link lake hydrology with people eating fish on the lakeshore. Oxygen isotopic trends in hearth otoliths from the last glacial maximum (LGM) were previously interpreted in terms of high evaporation under dry conditions. However, this ignored hydrology-driven changes in water δ18O. Here, a mass balance model is constructed to test the effect lake desiccation has on water δ18O and how this compares with the LGM otolith records. Based on this modelling, we suggest that Lake Mungo otolith signatures are better explained by evaporation acting on full lakes rather than by lake drying.

A national tree-ring data repository for Canadian forests (CFS-TRenD): structure, synthesis, and applications

Understanding the magnitude and cause of variation in tree growth and forest productivity is central to sustainable forest management. Measurements of annual growth rings allow assessments of individual-tree, tree population, and forest ecosystem vulnerabilities to drought stress or other changing forest disturbance regimes (insects, diseases, fire), which can be used to identify areas at greatest risk of forest losses. Given a heightened demand for tree-ring data, we consolidated and synthesized tree-ring studies and datasets gathered over the past 30 years in Canada by scientists with the Canadian Forest Service and research partners. We incorporated these datasets into a data repository that currently contains tree-ring measurements from 40 206 tree samples from 4594 sites and 62 tree species from all Canadian provinces and territories. Through our synthesis, we demonstrate the value of such large ensembles of tree-ring data for identifying patterns in tree growth over large spatial scales by mapping pan-Canadian drought sensitivity. Overall, we found high coherence in the samples analyzed; low coherence was generally limited to data-poor regions and species. Drought sensitivity was widespread across species and regions: 34% of sampled trees displayed a significant positive relationship between annual growth increment and summer soil moisture index. Dependence upon water availability in species Picea mariana (Mill.) BSP, Pinus banksiana Lamb., Pinus contorta Douglas ex Loudon, and Pseudotsuga menziesii (Mirb.) Franco was more strongly expressed in the warmest regions of the species’ range; for species Picea glauca (Moench) Voss and Populus tremuloides Michx., drought sensitivity was stronger in the driest regions. This unprecedented consolidation and synthesis of tree-ring data will enable new research initiatives (e.g., meta-analyses) aimed at improved understanding of the drivers, patterns, and implications of changes in tree growth, as well as facilitating new research collaborations in earth and environmental sciences. Among other things, there is a need for expanding the spatial distribution of sites across Canada’s northern regions, increasing the number of samples collected from older stands and angiosperm species, and integrating datasets from studies that evaluate the effects of silvicultural experiments, including provenance and progeny trials, on tree growth.

Post-1980s shift in the sensitivity of tundra vegetation to climate revealed by the first dendrochronological record from Bear Island (Bjørnøya), western Barents Sea

Tundra vegetation dynamics are an excellent indicator of Arctic climate change. In many places in the Arctic, greening of tundra has been observed since the 1980s due to rapid increases in temperature. However, in some areas the opposite process has taken place in connection with a reduction in biomass production. The spatial patterns of tundra ‘greening’ and ‘browning’ constitute important issues in the contemporary analysis of polar ecosystems. The aim of our study was to assess recent tundra vegetation dynamics on the basis of changes in annual growth ring widths of the polar willow. Bjørnøya (Bear Island), located in the western part of the Barents Sea is an important site in the transition zone between the high and low Arctic. No dendrochronological studies have been conducted to date due to the island’s isolation, which makes access very difficult. In 2012 and 2016, 43 samples of Salix polaris Wahlenb. were taken from the south-eastern part of Bear Island. An average chronology of the 29 most closely correlated measurement series was then compiled, covering 95 years (1922–2016); however, the time span 1946–2016 was used for the climate-growth analysis. Beginning in the mid-1980s, an increase in the width of annual increments was observed, whereas over the last decade (since 2005) the growth rate has declined rapidly. Simple correlation analyses showed that temperatures in spring and summer had the positive influence on the radial growth of the polar willow; however, the results of the moving correlation analysis made it possible to conclude that this relationship is more complex and time-dependent. Sensitivity of radial growth to temperature was strongest in the years 1955–2005, whereas the decrease in the strength of positive correlation with temperature since 2005 has been accompanied by a significant increase in the importance of summer precipitation.

Development of Neonectria punicea Pathogenic Symptoms in Juvenile Fraxinus excelsior Trees.

When monitoring the state of health of Fraxinus excelsior trees, unusual symptoms were discovered within a F. excelsior plantation in Bosnia and Herzegovina. These symptoms included the appearance of necrosis and cankers in the basal parts of the trees, followed by the formation of fruiting bodies, however, none of these symptoms were found in the crowns. After sampling and isolation of the necrotic parts from the stem base, pathogen Neonectria punicea was isolated and identified from the characteristics of pure cultures, morphology of the fruiting bodies, and from multilocus sequencing. In field conditions, juvenile F. excelsior trees were inoculated with two N. punicea isolates obtained from the necrotic tissues of both juvenile F. excelsior and mature Fagus sylvatica trees. In both isolates, 12 months post inoculation, the lengths and widths of the necroses were significantly larger compared to the control. Necroses of significantly larger lengths, widths and surfaces were found again in both tested isolates 24 months post inoculation. In the case of the F. excelsior isolate, the lengths of the necroses at both the stem base and at breast height increased by 1.6 times, whereas the F. sylvatica isolate increased in size by up to 1.7 and 1.8 times, respectively. Trees inoculated without a previous bark wound showed no symptoms, similar to the control trees. Scanning electron microscopy and X-ray micro-computed tomography imaging revealed that N. punicea hyphae penetrated from the cankers to the woody outermost annual growth ring and that hyphae were present mostly in the large earlywood vessels and rarely in the axial parenchyma cells. Hyphae also spread radially through the pits in vessels. The infected trees responded with the formation of tyloses in the vessels to prevent a rapid fungal spread through the axial vascular transport pathway. The ability of N. punicea to cause necroses in juvenile ash trees was demonstrated for the first time during this study. It poses a serious threat to planted forests and natural regenerations of F. excelsior especially if F. sylvatica is considered as a possible inoculum reservoir for future infections. This pathogen should be integrated within future ash resistance or breeding programs.

In-situ quantification of microscopic contributions of individual cells to macroscopic wood deformation with synchrotron computed tomography

Wood-based composites hold the promise of sustainable construction. Understanding the influence on wood cellular microstructure in the macroscopic mechanical behavior is key for engineering high-performance composites. In this work, we report a novel Individual Cell Tracking (ICT) approach for in-situ quantification of nanometer-scale deformations of individual wood cells during mechanical loading of macroscopic millimeter-scale wood samples. Softwood samples containing > 104 cells were subjected to controlled radial tensile and longitudinal compressive load in a synchrotron radiation micro-computed tomography (SRµCT) setup. Tracheid and wood ray cells were automatically segmented, and their geometric variations were tracked during load. Finally, interactions between microstructure deformations (lumen geometry, cell wall thickness), cellular arrangement (annual growth rings, anisotropy, wood ray presence) with the macroscopic deformation response were investigated. The results provide cellular insight into macroscopic relations, such as anisotropic Poisson effects, and allow direct observation of previously suspected wood ray reinforcing effects. The method is also appropriate for investigation of non-linear deformation effects, such as buckling and deformation recovery after failure, and gives insight into less studied aspects, such as changes in lumen diameter and cell wall thickness during uniaxial load. ICT provides an experimental tool for direct validation of hierarchical mechanical models on real biological composites.

Phloem development, growth markers, and sieve-tube longevity in two Neotropical trees

Abstract This study provides a detailed analysis of phloem anatomy, development, the formation of cell types, differentiation, and sieve-tube element’s longevity in two tropical arboreal species, Cedrela fissilis (Meliaceae, Rosid) and Citharexylum myrianthum (Verbenaceae, Asterid), growing in natural populations in the semi-deciduous Atlantic Rainforest. We periodically collected samples from the main stem at breast height (1.3 m), during both the dry and the wet seasons. Differences in the cells produced at these different seasons suggest that annual growth increments in the phloem are present in both species, marked by files of terminal narrow sieve-tube elements radially grouped in Cedrela fissilis, and in assemblages of narrow sieve tubes and axial parenchyma in Cytharexylum myrianthum, both appearing at the end of the wet season. In Cedrela fissilis, where fiber bands are present, each fiber band marks the end of the early phloem, acting as an indirect annual growth ring marker. Sieve-tube element longevity varied for both species from 4–26 months, a result similar to that obtained in temperate species.

A study of selected features of Shan Tong variety of plantation paulownia and its wood properties

A study of selected features of Shan Tong variety of plantation paulownia and its wood properties. The study was conducted on three-year-old and representative paulownia tree of the Shan Tong variety, from a plantation in the Kujawsko-Pomorskie Voivodeship, Poland. The three-year-old paulownia tree was 4.2 m high and its diameter at butt level was of 11 cm. The tree provided material for the study from its three-year-old shoot, which was divided into three parts: leaves, branches and the main trunk. According to calculations, this typical paulownia tree (a three-year-old shoot) from a plantation accumulated 4.664 kg of carbon in the part above the ground level, which corresponds to the absorption of 17.101 kg of CO2 from the atmosphere. Taking into account the underground part of this plant, it can be estimated that it absorbed over 30 kg of CO2 (on average, ca. 10 kg CO2 per year). The density of paulownia wood in absolute dry state was ca. 250 kg/m3. The width of annual growth rings was ca. 1.5 cm. This kind of wood is highly porous, with porosity of about 85% (good thermal insulation), and at the same time it has favourable resistance properties characterized by the modulus of elasticity of 4.05 GPa.

Sperry’s packing rule affects the spatial proximity but not clustering of xylem conduits: the case of Fagus sylvatica L.

Abstract Sperry’s packing rule predicts the optimum packing of xylem conduits in woody plants, where the frequency of xylem conduits varies approximately inversely with the square of the conduit radius. However, it is well established that such anatomical disposition does not remain fixed but is subject to a suite of adaptations induced by physiological constraints driven by both ontogenetic development and environmental characteristics. Here we challenge the hypothesis that increasing frequency of xylem conduits, concomitant with the decrease in their lumen area along the xylem pathway, would affect the spatial distribution of vessels inside tree-rings and their aggregation. To this end, we measured the vessels’ anatomical characteristics inside each tree-ring along with a complete radial series taken at different stem heights of Fagus sylvatica L. trees. Point pattern analysis indicated a significant effect of the distance from the tree base and a weak effect of cambial age on the nearest neighbour distance among xylem vessels, suggesting that vessels were closer to each other near the apex, and became progressively more distant toward the base. The spatial pattern of xylem vessels violated the assumption of complete spatial randomness, vessel spatial arrangement followed a uniform distribution at different distances from the tree base. Although there was an increase in the intensity and proximity among vessels, we demonstrated that no patterns of aggregation between vessels were found in sampled F. sylvatica trees. Rather, point pattern profiles clearly highlighted a lack of aggregation of vessels in the face of a regular spatial distribution in the annual growth rings along the stems.

Climate warming drives Himalayan alpine plant growth and recruitment dynamics

Abstract Understanding how climate influences plant reproduction and growth at contrasting range limits is crucial for predicting how species' ranges may shift in response to ongoing climate change. Trees and shrubs have shown warming‐induced increases in performance at upper elevation limits but reduced performance at lower distributional limits due to warming‐driven drought limitation. Whether these differential responses are also valid for alpine forbs exposed to accelerated warming remains largely unknown. We examined climate signal recorded in annual growth and recruitment over the past 60 years in the alpine forb Potentilla pamirica in Western Himalayas, and tested whether the responses to recent climate warming differ between dry steppe, wet alpine and cold subnival zone within the species 5,250–5,900 m elevation range. We reconstructed recruitment and growth chronologies from 1,019 individuals spanning 1–73 years, and more than 21,500 annual growth rings. We identified contrasting climatic controls of recruitment and growth at opposite elevation range margins, as well as contrasting demographic trends identified from age distributions. In lower‐elevation steppes, recruitment increased with high late‐winter snowfall and decreased with high summer temperatures, while growth increased with high summer precipitation. Conversely, warm winters and summers in higher‐elevation alpine and subnival zones support growth and recruitment, while snowy winters reduce them, especially at their upper elevation limit. The age distribution revealed greater numbers of younger individuals, indicating healthy growing populations, in the alpine habitat, while evidence of ageing plant populations was observed in steppe and subnival zones. Accelerated warming since the 1990s reduced growth and recruitment in dry steppes while supporting plant performance in the alpine habitat. The recruitment in the subnival zone did not peak during the past warmest decade due to concomitant extreme snowfall events. Synthesis. Our results provide novel information on population‐specific climate dependency of plant recruitment, growth and population dynamics, suggesting the high vulnerability of high‐elevation Himalayan ecosystems to climate change. This is partly balanced by high species longevity and slow radial growth securing a long‐term population persistence. Continuing trends of extreme snowfall events at higher elevations and droughts at lower elevations may lead to species range contraction.

CRECIMIENTO RADIAL Y CONICIDAD DEL FUSTE EN PLANTACIONES CON ACLAREO DE Pinus patula SCHIEDE ex SCHLECHTENDAL &amp; CHAMISSO

Pinus patula Schiede ex Schlechtendal &amp; Chamisso es una especie endémica de México, con gran relevancia económica por su alto potencial productivo en plantaciones forestales y bosques naturales. La intensidad y frecuencia de las cortas de aclareo generalmente influyen en el grueso de los anillos anuales de crecimiento, la proporción de madera tardía y la conicidad del fuste. El objetivo del presente estudio fue evaluar el crecimiento radial y el grueso de los anillos de crecimiento y de sus componentes de madera temprana y tardía a diferentes alturas del fuste, así como el índice de conicidad del fuste en plantaciones jóvenes de Pinus patula con cortas de aclareo aplicadas a los nueve y 13 años de edad. Se seleccionaron y derribaron 10 árboles por parcela con diámetro normal similar al valor promedio de éstas, para obtener tres secciones transversales (rodajas) de 3 cm de grueso a diferentes alturas de cada árbol muestreado. Las cortas de aclareo causaron un impacto reducido en el grueso de los anillos anuales y sus componentes de madera temprana y tardía en la sección basal. El efecto de la corta se presentó sólo al año siguiente de su aplicación, con incrementos en el área basal y en el grueso de madera temprana; después, el ritmo de crecimiento radial regresó a su patrón original. El grueso de los anillos y de la madera temprana y tardía fue mayor en la parte intermedia y superior del fuste, lo que ocasionó una reducción gradual en la conicidad, lo cual corroboró que la aplicación de las cortas de aclareo fueron tardías, cuando la copa ya se había concentrado en la parte superior del árbol, por la elevada competencia por espacio de crecimiento.

Towards improving the assessment of rainforest carbon: Complementary evidence from repeated diameter measurements and dated wood

We explore whether a growth-ring analysis can produce additional information about carbon budgets in tropical forests. Such forests are characterized by a high number of species and by trees that rarely have anatomically distinct annual growth rings, which hampers the application of dendrochronological tools in carbon balance assessments in the tropics. We use forest inventory data and archived annual diameter measurements from the Luki Biosphere Reserve in the southwestern margin of the Congo Basin forest massif. In addition, dated wood data are available from the same location thanks to tag nail traces that allow for the measurement of growth increments over a period of 66 years.We find that precise increment measurements based on dated wood are advisable for small subsets of many less abundant species and for functional species groups characterized by slow growth. The dated wood approach shows that many understory trees with non-periodical rings remain in a steady state for long periods of time. These results suggest a dated wood approach is advisable for studies of growth trajectories of individual trees that might be of importance for carbon assessments in degraded forests.

Carbon-14 dating when there's no ring on it: Age of four Pondoland grassland geoxyles and lessons learned

Annual growth rings are absent in many long-lived grassland geoxyles. Thus, estimates of age for individuals are largely based on non-benchmarked assessments by experienced botanists. We wished to obtain a more precise estimate of age from the xylopodia of four geoxylic taxa (i.e. Berkheya insignis, Callilepis laureola, Protea simplex and Tephrosia kraussiana) growing in a Pondoland grassland, using both the gas proportional counting and Accelerated Mass Spectroscopy radiocarbon dating techniques. Plants sampled in 2008 fell within modern concentrations of carbon 14; therefore, radiocarbon dating generally yielded two ages for each plant, an older age (range: 45–51 years, mean=49, CV=3.6%) corresponding with the nuclear testing period, and a younger age (range: 10–29 years, mean=18, CV=35%), corresponding to the period after the Partial Nuclear Test Ban Treaty. Hence the older ages are much less variable than the younger ages. All plants had the older age estimate, and all but two had the younger age estimate. In addition, two plants each, had two similar older age estimates. P. simplex plants were 16, 24, 27 and 29, or 45, 46–49, 47 and 49 years, T. kraussiana 13, 15 and 16, or 50 and two of 51 years, C. laureola 12, 15 and 21, or 49–50 and two of 50 years and B. insignis were 10, or 49, 50 and 51 years old. Growth rings were not visible with the naked eye. However, using stereomicroscopy, ring-like patterns were visible to some extent at 7X magnification for B. insignis, P. simplex and T. kraussiana, but not C. laureola. Counts of these structures were much lower than the younger 14C dates, and hence are unlikely to be annual rings. Despite the ambiguity of multiple ages, these estimates are a useful starting point or benchmark for future empirical investigations of age for forbs with no clear annual rings. Most studies have used radiocarbon dating to estimate the age of woody tree stem tissue, whereas this study is one of few to measure the age of below-ground modern tissues of South African forbs. Suggestions for further refinement during collection and processing of geophytic sample material are made based on lessons learned from this investigation.

Dendroclimatological assessment of Polylepis rodolfo-vasquezii: A novel Polylepis species in the Peru highlands

In spite of enormous diversity in tree species, dendrochronological records in the tropical Andes are very scarce. Therefore, it is necessary to increase the search for new tree species with high dendrochronological characteristics in the tropical Andes, including the humid Puna of Peru. We present the first tree-ring chronology from Polylepis rodolfo-vasquezii, a recently described tree species in the Central Andes of Peru between 4000 and 4400 m elevation. Fifty trees were sampled in the district of Comas, Peru. After establishing the anatomical characteristics that delimit the annual growth rings, we developed a ring-width chronology by applying conventional dendrochronological techniques. The chronology covers the period 1869–2015 (157 years) and is well replicated from 1920 to present (> 20 samples). The statistics used to evaluate the quality of the chronology indicate that the P. rodolfo-vasquezii has similar values of MS, RBAR and EPS to those shown by other Polylepis spp chronologies. To determine the main climatic factors controlling the growth of P. rodolfo-vasquezii, we compared our chronology with local and regional temperature and precipitation records. Growth season temperature (November to May) seems to be the main climatic factor modulating inter-annual variations in the growth of this species. The sensitivity to inter-annual temperature variations highlights the potential of P. rodolfo-vasquezii to provide climatically sensitive dendrochronological records in the Central Andes. To our knowledge, this is the first tree-ring record in South America displaying significant relationships with temperature over the tropical Atlantic Ocean.

Decline and Passive Restoration of Forest Vegetation Around the Yeocheon Industrial Complex of Southern Korea

This study was carried out to clarify the vegetation decline due to air pollutants emitted in the process of industrial activities and the passive restoration of the vegetation due to socioeconomic changes after economic growth. To achieve this goal, we investigated the spatial distribution of vegetation, differences in species composition and diversity among vegetation types different in damage degree, vegetation dynamics, the age structure and annual ring growth of two dominant plant species, and the landscape change that occurred in this area over the last 50 years. Plant communities tended to be spatially distributed in the order of grassland, shrubland (dominated by Styrax japonicus Siebold and Zucc. community), and forests (dominated by Pinus thunbergii Parl. and Pinus densiflora Siebold and Zucc. communities), with increasing distance from the pollution source. The result of stand ordination based on vegetation data reflected the trend of such a spatial distribution. Species richness evaluated based on the species rank dominance curve was the highest in shrubland and the lowest in grassland; species richness in forests was intermediate. The size class distribution of woody plant species in four plant communities composing three vegetation types showed the possibility of them being replaced by forest in the late successional stage. However, the density of successor trees was relatively low, whereas the density of shrubby plants, which are resilient to air pollution, was very high. The age class distribution of a dominant species forming shrubland and pine forest showed that most of them were recruited after industrialization in this area. The period when young individuals in both vegetation types were recruited corresponded to the period when the annual ring growth of the pine trees that survived air pollution was reduced. An analysis of the landscape change in this area indicated that coniferous forest and agricultural field decreased greatly, whereas industrial area, residential area, mixed forest, and broadleaved forest showed increasing trends since construction of the industrial complex. As a result, the decrease in coniferous forest is usually due to vegetation decline and partially to succession, as the pine trees dominating the forest are not only sensitive to air pollution but are also shade-intolerant. The increase in mixed and broadleaved forests reflects vegetation decline or succession. Vegetation decline progressed for about 30 years after the construction of the industrial complex; it has begun to be restored passively since then, although the change has been slow. These results are in line with the environmental Kuznets curve hypothesis that environmental degradation increases in the early stages of economic growth to a certain point, and, after a turning point, economic development leads to environmental improvements—thus, there is an inverted U-shaped relationship between economic growth and environmental degradation.