Decrease In Radial Growth Research Articles

Heterobasidion annosum and Armillaria ostoyae significantly reduce radial growth during three years before stem death in infected Pinus pinaster

Butt and root-rot diseases caused by Armillaria sp. and Heterobasidion sp. are highly destructive to conifers worldwide. These diseases lead to loss of growth, wood degradation, and tree mortality, often necessitating premature logging. However, little is known about the effect of infection on the growth and mortality of adult pines during forest development. In this study, mature maritime pines were sampled from two forest sites in south-west France. In 2013, the Sanguinet site provided both healthy (asymptomatic) and Heterobasidion annosum-infected pines, while in 2019 the Mano site also provided Armillaria ostoyae-infected pines. Radial growth dynamics were compared between healthy and infected pines using two complementary approaches taking into account the diameter of each tree: 1. Compensation over 10 years and year by year comparisons of mean (dendrochronogram) between groups of pines with same Last Year of Radial Growth (LYRG); 2. Analysis of covariance by modeling the relationship between basal area increment and basal area in healthy or infected pines for each LYRG. Our results indicate that symptomatic trees infected by Heterobasidion annosum are characterised by a rapid reduction in radial growth across the entire tree circumference. The covariance method was more efficient to show that the radial growth of infected trees was significantly lower (between 25% and 72% loss) in the three years preceding the year of growth arrest, on both sites, i.e., for two different periods of years. For Armillaria ostoyae, growth data shows the same trends than for H. annosum, with a sharp decline over the last 2–3 years of growth. Covariance results for LYRG 2018 and 2019 reveal that infection symptoms significantly reduces the radial growth of infected trees compared to asymptomatic trees over the last three years of growth. These results show that infection of maritime pine by butt and root-rot fungi can lead to a rapid decrease in radial growth, and this decrease is independent of the calendar year of cambial death at breast height.

Did stand opening 60 years ago predispose a European beech population to death?

Widespread increases in tree mortality have fueled the debate on the mechanisms of heat- and drought-related tree death. While much research focused on the immediate causes of tree death, the role of predisposing factors for death is not well understood. We employed tree-ring and climate sensitivity analysis of growth to study the importance of legacy effects of past disturbances for growth patterns and a recent mortality burst in a protected European beech (Fagus sylvatica) forest, comparing groups of live and recently died trees in the same stand. Live and dead trees showed a decade-long decrease in radial growth since the severe 1976 drought, which indicates that the high mortality in the last two decades is not solely caused by recent drought spells, but that trees were apparently predisposed by previous events to death decades later. An even more distant event than the 1976 drought that has imprinted on the chronologies is the severe 1947 drought in combination with extensive logging at that time. It appears that stand opening 60 and 40 years ago due to high immediate drought mortality in conjunction with heavy logging resulted in much higher inter-annual ring width variability with more extreme negative and positive pointer years in the subsequent years, and led to permanent reduction in tree health. We identified the first derivative of the ring width curve as the most reliable early-warning signal of a predisposition to drought-induced death, while inter-annual growth variability and growth resistance and resilience to drought were less suited. We suggest that the causes of recent climate warming-related dieback of beech and other temperate hardwood forests may only be fully grasped, when the imprint of past stress events on growth and vitality is understood. The physiological mechanisms causing legacy effects with long delay of death require further study.

Recent global warming as a proximate cause of deforestation and forest degradation in northern Pakistan.

Instrumental climatological records such as weather stations data of northern areas of Pakistan are not sufficient to assess the forest extreme events reliably. To understand the past climatic variability, tree ring width based climatic reconstruction is the best alternative to trace climate variability that goes back in time. Quercus Incana is the most sensitive species to drought and climatic variation in northern Pakistan. However, very little research quantifies the rate of ongoing climatic changes. A total of 65 tree cores were collected from two sites to understand the radial growth of Q. Incana to extreme drought events. The radial growth is mainly affected by high temperatures during May-July. In addition, radial growth exhibits a positive correlation with February-June precipitation while it is negatively correlated with the September precipitation. The radial growth decrease, particularly in harsh climatic conditions. The reconstructed tree ring record was strongly coherent with the May-June self-calibrated Palmer drought severity index (scPDSI) and reliable in reconstructing drought variability for the period 1750–2014. During the past 264 years, wet periods were found during 1980–2010, 1812–1836, and 1754–1760, while dry periods were found during 1896–1922, 1864–1876, and 1784–1788. Our reconstruction explains 39.8% of the scPDSI variance. The extreme drought and wet years we arrived at were in close agreement with the drought and wet periods that occurred in northern Pakistan. Wavelet analysis revealed drought variability at periodicities of 2.2–2.5, 3.3, 3–4, 16.7, 16.8, and 68–78.8 years. Hence it is concluded that deforestation and forest degradation rate increased with extreme drought and wet years. Overall, the variation of drought in northern Pakistan seems to have been affected due to El Nino south oscillation, Pacific decadal oscillation, or Atlantic multi-decadal oscillations.

Alterations in Growth and Morphology of Ganoderma lucidum and Volvariella volvaceae in Response to Nanoparticle Supplementation

Use of nanoparticles (NPs) in several commercial products has led to emergence of novel contaminants of air, soil and water bodies. The NPs may exhibit greater ecotoxicity due to nano-scale dependent properties over their bulk counterparts. The present investigation explores the effect of in vitro supplementation of TiO2, silica and silver NPs on radial growth and ultrastructural changes in the hyphae and spores of two mushroom genera, Ganoderma lucidum and Volvariella volvaceae. A concentration dependent decrease in radial growth on NP amended potato dextrose agar medium was recorded. However, in comparison to control, there was decrease in radial diameter on supplementation with TiO2 NPs while an increase was recorded for silica and silver NPs amendments as compared to their bulk salts at same concentrations after 48 h of incubation. Optical microscopy studies showed decrease in the number of spores while increase in spore diameter and thinning of hyphal diameter on NPs supplementation. Scanning electron microscopy analysis of fungal growth showed presence of deflated and oblong spores in two fruiting strains of Ganoderma while Volvariella exhibited decreased sporulation. Further, hyphal thinning and branching was recorded in response to NP amendments in both the test mushrooms. Enhancement of protein content was observed on NP compared to bulk supplementation for all cultures, concentrations and hours of incubation except for TiO2 NPs. Likewise, bulk and NP supplementations (at 100 mg L −1) resulted in enhanced laccase activity with occurrence of laccase specific protein bands on SDS-PAGE analysis.

Growth mode control for direct-gap core/shell Ge/GeSn nanowire light emission

Germanium-tin is a promising semiconductor alloy system for novel light emitting devices and optical sensors in the mid-IR region. For sufficiently high Sn compositions, the material has a direct band-gap near 0.5 eV, and could have applications either as a detector or an emitter. Although high Sn compositions have been achieved in Ge1−xSnx through a variety of growth strategies, the understanding of how chemical vapor deposition conditions affect Sn composition and optical properties in core–shell Ge/Ge1−xSnx nanowires is still lacking. In this study, gas precursor partial pressures and shell growth temperatures are systematically varied to provide guiding principles to overcome obstacles for higher Sn incorporation. We achieve a direct band-gap material using an elastically compliant Ge core nanowire substrate. In the course of the growth study, we demonstrate several findings regarding the Ge1−xSnx shell growth mechanism. First, we observe an H2 passivation effect in which higher H2 to SnCl4 partial pressure ratio results in a concurrent increase in axial wire growth and decrease in radial growth. Second, we find that Ge1−xSnx shell growth in the studied CVD process is mass transport limited. Third, our results suggest that low shell growth temperature and high shell growth rate facilitate high Sn composition through metastable Sn solute trapping due to suppressed surface diffusion relative to the velocity of advancing shell surface steps. In this work, we demonstrate single nanowire photoluminescence at room temperature from core-shell Ge/Ge0.88Sn0.12 nanowires. Understanding the Ge1−xSnx shell growth mechanism via chemical vapor deposition (CVD) facilitates achieving minimal residual strain in the shell and the high crystalline quality and large Sn composition necessary for the observed optical properties. The results are universally applicable to Ge1−xSnx thin film epitaxy on compliant substrates including grown or etched nanowires, nanosheets, or free-standing 2D crystals.

A Histone Deacetylase, MoHDA1 Regulates Asexual Development and Virulence in the Rice Blast Fungus.

Interplay between histone acetylation and deacetylation is one of the key components in epigenetic regulation of transcription. Here we report the requirement of Mo-HDA1-mediated histone deacetylation during asexual development and pathogenesis for the rice blast fungus, Magnaporthe oryzae. Structural similarity and phylogenetic analysis suggested that MoHDA1 is an ortholog of Saccharomyces cerevisiae Hda1, which is a representative member of class II histone deacetylases. Targeted deletion of MoHDA1 caused a little decrease in radial growth and large reduction in asexual sporulation. Comparison of acetylation levels for H3K9 and H3K14 showed that lack of MoHDA1 gene led to significant increase in H3K9 and H3K14 acetylation level, compared to the wild-type and complementation strain, confirming that it is a bona fide histone deacetylase. Expression analysis on some of the key genes involved in asexual reproduction under sporulation-promoting condition showed almost no differences among strains, except for MoCON6 gene, which was up-regulated more than 6-fold in the mutant than wild-type. Although the deletion mutant displayed little defects in germination and subsequent appressorium formation, the mutant was compromised in its ability to cause disease. Woundinoculation showed that the mutant is impaired in invasive growth as well. We found that the mutant was defective in appressorium-mediated penetration of host, but did not lose the ability to grow on the media containing H2O2. Taken together, our data suggest that MoHDA1-dependent histone deacetylation is important for efficient asexual development and infection of host plants in M. oryzae.

A histone deacetylase, MoHOS2 regulates asexual development and virulence in the rice blast fungus

Histone acetylation/deacetylation represent a general and efficient epigenetic mechanism through which fungal cells control gene expression. Here we report developmental requirement of MoHOS2-mediated histone deacetylation (HDAC) for the rice blast fungus, Magnaporthe oryzae. Structural similarity and nuclear localization indicated that MoHOS2 is an ortholog of Saccharomyces cerevisiae Hos2, which is a member of class I histone deacetylases and subunit of Set3 complex. Deletion of MoHOS2 led to 25% reduction in HDAC activity, compared to the wild-type, confirming that it is a bona-fide HDAC. Lack of MoHOS2 caused decrease in radial growth and impinged dramatically on asexual sporulation. Such reduction in HDAC activity and phenotypic defects of ΔMohos2 were recapitulated by a single amino acid change in conserved motif that is known to be important for HDAC activity. Expression analysis revealed up-regulation of MoHOS2 and concomitant down-regulation of some of the key genes involved in asexual reproduction under sporulation-promoting condition. In addition, the deletion mutant exhibited defect in appressorium formation from both germ tube tip and hyphae. As a result, ΔMohos2 was not able to cause disease symptoms. Wound-inoculation showed that the mutant is compromised in its ability to grow inside host plants as well. We found that some of ROS detoxifying genes and known effector genes are de-regulated in the mutant. Taken together, our data suggest that MoHOS2-dependent histone deacetylation is pivotal for proper timing and induction of transcription of the genes that coordinate developmental changes and host infection in M. oryzae.

Variación en los patrones de crecimiento previo a la muerte de individuos de Austrocedrus chilensis a lo largo de un gradiente pluviométrico en el norte de la Patagonia Andina

Fil: Vega, Leticia Maria. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Economia, Politica y Administracion Rural.; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales; Argentina

Spatiotemporal evidence of tree-growth resilience to climate variations for Yezo spruce (Picea jezoensis var. komarovii) on Changbai Mountain, Northeast China

Global warming-induced changes in tree-growth resilience to climate variations have been widely reported for mid- and high-latitude regions around the world. Most studies have focused on the spatial variability of trees in radial growth–climate relationships on Changbai Mountain in Northeast China, but little is known about temporal changes in tree growth in response to climate. We explored the stability of effect of climate variables on radial growth of Yezo spruce [Picea jezoensis Carr. var. komarovii (V.Vassil.) Cheng et L.K.Fu] at 1200, 1400, and 1600 m above sea level, representing low, middle, and upper ranges of the spruce–fir mixed forest on Changbai Mountain. The results showed that the relation between tree growth and climate did not vary with altitude, but the stability of the tree-growth–climate relationship did vary with altitude as the climate changed. Radial growth of Yezo spruce at all three elevations was influenced primarily by maximum temperature during May (Tmax5) and mean minimum temperature from January to March (Tmin1–3). More specifically, the relationship strengthened significantly at lower elevations, but weakened significantly at higher elevation, and fluctuated at mid elevations since 1980. Increase in Tmin1–3 and decrease in Tmax5 were the main reasons for the decrease in the radial growth at three altitudes. The findings of this study clarified that the decrease in radial growth on Changbai Mountain is not a “divergence problem” of an unexpected decrease in tree growth in response to an increase in mean temperature and provides a reference for using tree-ring data to reconstruct climate patterns and/or predict the growth of trees under various climate change scenarios.

Respuesta climática de Pinus oocarpa Schiede Ex Schetol en el Bosque La Primavera, Jalisco

El Bosque La Primavera (BLP) constituye una reserva de importancia ecoturística y proveedora de servicios ambientales para la metrópoli de Guadalajara. Sin embargo, las actividades humanas han alterado la estabilidad de sus ecosistemas. El objetivo del estudio fue analizar la variabilidad hidroclimática de la especie dominante Pinus oocarpa de alta sensibilidad climática. Cronologías de madera temprana (EWI), tardía (LWI) y de anillo total (RWI), con 165 años de extensión (1850-2014), se generaron para la especie en BLP. La serie residual EWI se correlacionó significativamente con la precipitación acumulada octubre-mayo (r = 0.775, p < 0.000), de estaciones climáticas aledañas a la reserva y se utilizó para una reconstrucción de precipitación; asimismo, se encontró una asociación negativa, pero significativa, entre temperatura máxima promedio en enero-junio y la serie EWI (r = -0.622, p < 0.000).La sequía más prolongada en la reconstrucción se detectó de 1909 a 1925, otras más como las de las décadas 1850, 1890, 1950, 1990 y 2000 se encuentran presentes en otras reconstrucciones climáticas para Jalisco, lo que es indicativo de la influencia de fenómenos de circulación general como El Niño Oscilación del Sur (ENSO). El incremento en la temperatura máxima en las últimas tres décadas en el BLP ha afectado el crecimiento de la especie con una tendencia a reducirlo, situación que pone en riesgo la estabilidad de esta y de otras especies asociadas y, por ende, la provisión de servicios ecosistémicos a la metrópoli.

Imprisoned in the Cretan mountains: How relict Zelkova abelicea (Ulmaceae) trees cope with Mediterranean climate

We investigate the sensitivity of the relict, endemic Cretan tree species Zelkova abelicea (Lam.) Boiss. (Ulmaceae) to several climate variables (temperature, precipitation and drought). For this purpose, we establish the first centennial tree-ring chronology for the species, and the first ever tree-ring chronology for a broadleaved species on Crete. We demonstrate the strong sensitivity of Z. abelicea towards precipitation and drought in late spring to early summer and the absence of a significant response to abundant precipitation occurring during winter or early spring. Whereas the late spring sensitivity is strong and consistent through time, the species seems to be experiencing a loss of signal towards early summer conditions since the 1970s, interpreted as an earlier cessation of cambial activity due to the increase in summer drought conditions on Crete. However, despite a reduced vegetative period, no significant decrease in radial growth of Z. abelicea was observed in the tree-ring series for the last decades, thus highlighting the capacity of Z. abelicea to withstand changing environmental conditions.

Stem girdling indicates prioritized carbon allocation to the root system at the expense of radial stem growth in Norway spruce under drought conditions

The early culmination of maximum radial growth (RG) in late spring has been found in several coniferous species in a dry inner Alpine environment. We hypothesized that an early decrease in RG is an adaptation to cope with drought stress, which might require an early switch of carbon (C) allocation to belowground organs. To test this hypothesis, we experimentally subjected six-year-old Norway spruce saplings (tree height: 1.35m; n=80 trees) to two levels of soil water availability (watered versus drought conditions) and manipulated tree C status by physically blocking phloem transport at three girdling dates (GD). The influence of C availability and drought on tree growth (radial and shoot growth; root biomass) in response to girdling was analyzed in both treatments. Non-structural carbohydrates (NSCs, soluble sugars and starch) were measured in the stem, root and current leader to evaluate changes in tree C status due to girdling. The main finding was a significant increase in RG of the girdled trees compared to the controls above the girdling zone (UZ). At all girdling dates the RG increase was significantly more intense in the drought-stressed compared with watered trees (c. 3.3 and 1.9-fold higher compared with controls in the drought-stressed and watered trees, respectively), most likely indicating that an early switch of C allocation to belowground occurs as an adaptation to maintain tree water status under drought conditions. Reactivation of the cambium after the cessation of its regular activity was detected in UZ in drought-stressed trees, while below the girdling zone no xylem formation was found and the NSC content was strikingly reduced. Irrespective of water availability, girdling before growth onset significantly reduced the progression of bud break (P<0.05) and the length of the current leader shoot by −47% (P<0.01) indicating a reduction in xylem hydraulic conductance, which was corroborated by significantly reduced xylem sap flow (P<0.001). Based on our findings, we conclude that during the growing season drought stress prioritizes an early switch of C allocation to the root system as an adaptation to maintain adequate tree water status in drought-prone environments.

A synthesis of radial growth patterns preceding tree mortality.

Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-continental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1-100years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks.

English

The present investigation explores the effect of selenium supplementation on radial growth and ultrastructural alterations in the hyphae and spores of Ganoderma lucidum. A concentration dependent decrease in radial growth was observed on culturing G. lucidum on sodium selenate supplemented mushroom minimal agar post 24 h. However, in comparison to control, selenium supplementation slightly increased diameter of radial growth till 10 ppm after 48 h. The Scanning Electron Microscopy (SEM) studies of radial growth showed selenium concentration dependent gradual decrease in hyphal diameter suggesting thinning and extensive branching of mycelia in response to increased Se supplementation. Moreover, SE micrographs also depict selenium concentration dependent decrease in number of spores and spore size. A significant decrease in spore diameter was recorded for mushroom minimal agar supplemented with 20 and 25 ppm (5.64 and 1.26 μm, respectively) as compared to control (10.04 μm). The spore were morphologically altered from spherical to oval or oblong and inflated to constrict deformed on increasing selenium concentration. SEM-energy dispersive X-ray spectroscopy (SEM-EDS) studies of intact mycelia showed no traces of selenium. However, crushed mycelia samples exhibited Se signals probably due to presence of selenium as integral component of cytosolic moieties like selenoproteins. Atomic absorption spectroscopy (AAS) of mycelia showed an increasing trend in the uptake of selenium with increased selenium supplementation. Percentage absorption was found to be in range of 7.2 - 9.9% with maximum absorption at concentrations of 15 and 25 ppm. Hence, sodium selenate supplementation at 10 ppm (with maximum 15 ppm) can be used for Se fortification as Ganoderma can grow rapidly without significant alteration in structure and morphology to enhance its biomedicinal properties. Key words: Ganoderma, scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (SEM-EDS), selenium, selenoproteins.

Tree-ring records of the historic pollution along Novăţ river, Maramureş Mountains, (Romania)

Mining activities cause heavy metal pollution of the water, the soil and the air in the affected areas. Metal toxicity, acidic pH and changes in soil structure are supposed to induce a stress on the riparian forest. Coniferous trees affected by this type of human-induced environmental stress react by producing different anatomical changes, commonly the abrupt radial growth decrease and traumatic resin duct production. By analysing growth anomalies formed in tree-rings, it is therefore possible to reconstruct retrospectively the dynamics of forest under environmental polluted, conditions. On the 10th of March 2000 an ecological disaster occurred in Maramures Mountains, Romania. A tailing pond of the Baia Borsa mines (district Maramures) burst after heavy precipitations and thawing. About 20 000 t of heavy metal contaminated sludge flooded along Novaţ and Vaser Valleys and then reached the rivers Viseu and Tisa. The 2000 event severely pollutes with heavy metals (As, Cd, Cr, Ni, Pb, Zn etc.) the soil and ground water in the riparian forest areas. Moreover, these trees were buried under toxic sediments left after the passage of the flood. Riparian forest stands along Novaţ river are mainly composed by Norway spruce ( Picea abies (L) Karst.) trees. This tree species is known to have a high susceptibility to soil pollution, because of the shallow growing roots within the upper part of the soil profile. It has therefore a high potential for dendrochronological studies. In this mining area, so far relations between pollution events and the growth response of Norway spruce have not been tested.

Radial growth changes following hemlock woolly adelgid infestation of eastern hemlock

• Context Hemlock woolly adelgid (Adelges tsugae) is an invasive insect that is defoliating and killing eastern hemlock (Tsuga canadensis) in the USA.• Aims We quantified changes in tree-ring growth rates and wood anatomy for living trees infested with hemlock woolly adelgid across six sites from Massachusetts (42°41′N) to Georgia (34°53′N) to identify growth responses of eastern hemlock that had survived infestation.• Methods Annual ring widths from infested eastern hemlocks were cross-dated and measured. Growth rates before and after infestation were compared. Two infested trees from Virginia were cut, and thin sections were prepared to identify changes in cell properties.• Results At three sites, trees experienced a significant decrease in radial growth after hemlock woolly adelgid arrival; however, the other three sites showed no change or increase in growth. Latewood produced after hemlock woolly adelgid infestation had significantly smaller cells with reduced cell wall thickness compared to latewood prior to infestation.• Conclusion At half the sites where hemlock woolly adelgid infested eastern hemlock trees were sampled, radial growth increased or remained unchanged. This unexpected response may be due to reduced competition due to mortality of other eastern hemlocks or physiological compensatory responses of increased photosynthetic rate and increased water use efficiency experienced by eastern hemlock infested with hemlock woolly adelgid.

Tree-Line Structure and Dynamics at the Northern Limit of the Larch Forest: Anabar Plateau, Siberia, Russia

The goal of the study was to provide an analysis of climate impact before, during, and after the Little Ice Age (LIA) on the larch (Larix gmelinii) tree line at the northern extreme of Siberian forests. Recent decadal climate change impacts on the tree line, regeneration abundance, and age structure were analyzed.The location of the study area was within the forest-tundra ecotone (elevation range 170–450 m) in the Anabar Plateau, northern Siberia. Field studies were conducted along elevational transects. Tree natality/mortality and radial increment were determined based on dendrochronology analyses. Tree morphology, number of living and subfossil trees, regeneration abundance, and age structure were studied. Locations of pre-LIA, LIA, and post-LIA tree lines and refugia boundaries were established. Long-term climate variables and drought index were included in the analysis.It was found that tree mortality from the 16th century through the beginning of the 19th century caused a downward tree line recession. Sparse larch stands experienced deforestation, transforming into tundra with isolated relict trees. The maximum tree mortality and radial growth decrease were observed to have occurred at the beginning of 18th century. Now larch, at its northern boundary in Siberia, is migrating into tundra areas. Upward tree migration was induced by warming in the middle of the 19th century. Refugia played an important role in repopulation of the forest-tundra ecotone by providing a seed source and shelter for recruitment of larch regeneration. Currently this ecotone is being repopulated mainly by tree cohorts that were established after the 1930s. The last two decades of warming did not result in an acceleration of regeneration recruitment because of increased drought conditions. The regeneration line reached (but did not exceed) the pre-LIA tree line location, although contemporary tree heights and stand densities are comparatively lower than in the pre-LIA period. The mean rate of tree line upward migration has been about 0.35 m yr-1 (with a range of 0.21–0.58), which translates to a tree line response to temperature of about 55 m °C-1.

A Kunitz trypsin inhibitor from chickpea (&amp;lt;i&amp;gt;Cicer arietinum&amp;lt;/i&amp;gt; L.) that exerts an antimicrobial effect on Fusarium oxysporum f.sp. ciceris

Fusarium oxysporum f.sp. ciceris (Foc) is one of the most important fungal pathogens of chickpea and is regarded as a constant threat in tropical and subtropical countries. In order to correlate Fusarium wilt resistance/susceptibility in Cicer arietinum to the presence or absence of trypsin inhibitor (TI) in the crude extract, trypsin inhibitory assay (TIA) and in vitro activity of TI against Foc were studied. In the present study, a 20 kDa trypsin inhibitor was purified from Fusarium wilt resistant cultivar (viz. JG 2001-12) by ammonium sulfate precipitation, dialysis and chromatographies with Sephadex G-100 and Diethyl aminoethyl cellulose (DEAE-cellulose-52) ion-exchange column. Results of pathogenecity assay were found to be in correlation to the trypsin inhibitor assay where the Fusarium wilt resistant cultivar showed high trypsin inhibitory activity (99%) in the presence of trypsin enzyme using both natural and synthetic substrates. Preliminary studies using crude extracts of JG 2001-12 showed a decrease in radial growth of Foc. A 45%-82% reduction in conidium germination at 20 μg&middotmL-1 Cicer arietinum trypsin inhibitor (CaTI) concentration was observed, thereby, indicating the use of CaTI in suppression of pathogen and in its deployment through transgenic plants for the management of Fusarium wilt.

Dendrochronological research of Scots pine (Pinus sylvestris L.) radial growth in vicinity of industrial pollution

The aim of this research is to investigate changes in the annual radial increment of Scots pine (Pinus sylvestris L.) in the vicinity of intensive (3–10km) and moderate (11–20km) industrial pollution during different growth periods (growth promotion, inhibition, and recovery). Low level of emission was beneficial for tree growth during the growth promotion period, and the annual radial increment in the zones of intensive and moderate pollution increased by approximately 15–25% and 10%, respectively. Severe loss was reported to forests during the growth inhibition period when nitrogen and sulphur dioxide emissions were 37–40 thousand (thou.) tons per year. About 40–45% tree radial increment loss was observed in the stands closest to the pollution source, and 15–20% loss was observed for the most distant stands. The stabilization of radial growth decrease and the beginning of recovery of damaged stands began in 1988–1992, when the annual amount of industrial emissions and environmental pollution were considerably reduced. The stabilization of radial growth and the initiation of recovery after pollution reduction were high for the most damaged stands. Their radial increment was stable and close to that of the control stands in 2000–2011. Stands with less damage growing further from the pollution source were recovered earlier, and their radial increment stabilized near the control increment in 1995–1999. The results of linear regression analysis demonstrated that the impact of pollution is different for stands growing at different distances from the plant, and the impact decreases with distance (R2=0.78 and R2=0.75, respectively; p<0.05).

Timing of growth reductions in black spruce stem and branches during the 1970s spruce budworm outbreak1This article is one of a selection of papers from the 7th International Conference on Disturbance Dynamics in Boreal Forests.

Spruce budworm ( Choristoneura fumiferana (Clemens)) defoliation is known to regularly produce radial growth decrease in black spruce ( Picea mariana (Mill.) Britton, Sterns &amp; Poggenb.) in the boreal forest of Quebec. Some studies have already shown that the first year of defoliation does not induce growth losses in the stem but could occur in other tree parts. We therefore examined the timing and duration of the growth reduction caused by the last outbreak in black spruce by also considering the branches. More than 79% of branches and 65% of stems exhibited a &gt;40% growth decrease.The reduction was first registered in the upper part of the stem before being detected lower in the stem in 87% of the trees. Probabilities of growth reduction in the upper part of the stem were highest in 1976 and 1977. In the lower stem, the probabilities were highest in 1978. An interesting finding was that in 69% of the studied stands, the probability of growth reduction started earlier (1–2 years) in the branches than in the stem at 1.3 m. Branch analysis should be considered whenever questions arise in regard to the evolution of spruce budworm defoliation as well as the timing of observed growth reduction in black spruce.