Needle longevity, shoot growth and branching frequency in relation to site fertility and within-canopy light conditions in Pinus sylvestris

Changes in needle morphology, average needle age, shoot length growth, and branching frequency in response to seasonal average integrated quantum flux density ($Q_{\textrm{int}}$) were investigated in Pinus sylvestris L. in a fertile site (old-field) and an infertile site (raised bog). In the fertile site, the trees were 30 years old with a dominant height of 17–21 m, and with average $\pm$ SD nitrogen content (% of dry mass) of 1.53 $\pm$ 0.11 in the current-year needles. In the infertile site, 50 to 100-yr-old trees were 1–2 m tall, and needle N content was 0.86 $\pm$ 0.12%. Relationships between the variables were studied using linear correlation and regression analyses. With increasing irradiance, shoot length ($L_{\textrm{s}}$) and shoot bifurcation ratio ($R_{\textrm{b}}$, the number of current-year shoots per number of shoots formed in the previous year) increased in the fertile site, but not in the infertile site. Despite greater branching frequency, apical control was enhanced at higher irradiance in the fertile site. The shoot length distributions became more peaked (positive kurtosis) and biased towards lower values of $L_{\textrm{s}}$ (positive skewness) with increasing $Q_{\textrm{int}}$ in this stand. The shoot distributions were essentially normal in the infertile site. Large values of $R_{\textrm{b}}$ combined with the skewed distributions of shoot length resulted in conical crowns in the fertile site. In contrast, lower bifurcation ratio, normal shoot length distributions and low rates of shoot length growth led to flat-topped crowns in the bog. Average needle age was independent of $Q_{\textrm{int}}$, but was larger in the infertile site. Thus, reduced rates of foliage production in the infertile site were somewhat compensated for by increased foliage longevity, and we suggest that shoot growth rates may have directly controlled the needle life span via reduced requirements for nutrients for the growth and via reduced self-shading within the canopy. Needle age and $Q_{\textrm{int}}$ independently affected needle structure. Needle age only moderately altered needle nutrient contents, but the primary age-related modification was the scaling of needle density with age. The density was similarly modified by age in both sites, but the needles were denser in the infertile site. Given that denser needles are more resistant to mechanical injury, larger density may provide an additional explanation for enhanced longevity in the infertile site. Our study demonstrates that site fertility is an important determinant of the plastic modifications in crown geometry, and needle life span in P. sylvestris.Longévité des aiguilles, croissance des pousses et fréquence de ramification en relation avec la fertilité du site et les conditions de lumière dans la canopée de Pinus sylvestris. Les changements dans la morphologie des aiguilles, l'âge moyen des aiguilles, la croissance en longueur des pousses, la fréquence de la ramification ont été étudiés en réponse à la densité du flux quantique intégré ($Q_{\textrm{int}}$) moyen saisonnier chez Pinus sylvestris L. dans un site fertile (anciennement cultivé) et dans un site pauvre (tourbière). Dans le site fertile, les arbres étaient âgés de 30 ans, avec une hauteur dominante de 17–21 m, et une teneur en azote (g kg$^{-1}$ de matière sèche) moyenne de 15,3 $\pm$ 1,1 dans les aiguilles de l'année. Dans le site pauvre, les arbres, âgés de 50 à 100 ans, avaient une taille de 1 à 2 m, la teneur en azote des aiguilles était de 8,6 $\pm$ 1,2 g kg$^{-1}$. Les relations entre les variables ont été étudiées en utilisant les analyses de corrélation linéaire et de régression. Lorsque l'irradition est croissante, la longueur de la pousse ($L_{\textrm{s}}$) et le rapport de ramification ($R_{\textrm{b}}$, nombre de pousses de l'année par nombre de pousse formées au cours de l'année précédente) augmentent dans le site fertile, mais pas dans le site pauvre. Malgré une fréquence plus élevée de ramification, le contrôle apical est exacerbé par une irradiation plus élevée dans le site fertile. Les distributions des longueurs de pousse deviennent plus pointues (kurtosis positive) et biaisées vers les valeurs les plus faibles de $L_{\textrm{s}}$ (skewness positive) avec un $Q_{\textrm{int}}$ en augmentation dans ce site. Les fortes valeurs de $R_{\textrm{b}}$, combinées avec des distributions skewness des longueurs de pousses conduisent à des canopées coniques dans le site fertile. Par opposition, un rapport plus faible de la ramification, distributions normales des longueurs de pousses, et une faible croissance en longueur des pousses conduisent à la formation de canopées aplaties dans la tourbière. L'âge moyen des aiguilles était indépendant du $Q_{\textrm{int}}$, mais il était plus élevé dans le site le plus pauvre. Cependant, les taux réduits de production foliaire dans la station pauvre étaient, en quelque sorte, compensés par l'accroissement de longévité du feuillage, et nous suggérons que les taux de croissance des pousses peuvent avoir contrôlé directement la durée de vie des aiguilles par une réduction des besoins en nutriments pour la croissance et par une réduction de l'ombre dans la canopée. L'âge des aiguilles et $Q_{\textrm{int}}$ affectent indépendamment la structure des aiguilles. L'âge des aiguilles modifie seulement modérément la teneur en nutriments des aiguilles, mais la modification primaire liée à l'âge, était l'échelle de densité d'aiguilles. La densité était pareillement modifiée par l'âge dans les deux stations, mais les aiguilles étaient plus denses dans le site pauvre. étant donné que des aiguilles plus denses sont plus résistantes aux blessures mécaniques, une plus grande densité peut fournir une explication additionnelle à la longévité renforcée dans les stations pauvres. Notre étude démontre que la fertilité de la station est un important déterminant des modifications plastiques de la géométrie de la couronne et la durée de vie des aiguilles chez P. sylvestris

Potential Hazard of Lanthanides and Lanthanide-Based Nanoparticles to Aquatic Ecosystems: Data Gaps, Challenges and Future Research Needs Derived from Bibliometric Analysis

Lanthanides (Ln), applied mostly in the form of nanoparticles (NPs), are critical to emerging high-tech and green energy industries due to their distinct physicochemical properties. The resulting anthropogenic input of Ln and Ln-based NPs into aquatic environment might create a problem of emerging contaminants. Thus, information on the biological effects of Ln and Ln-based NPs is urgently needed for relevant environmental risk assessment. In this mini-review, we made a bibliometric survey on existing scientific literature with the main aim of identifying the most important data gaps on Ln and Ln-based nanoparticles’ toxicity to aquatic biota. We report that the most studied Ln for ecotoxicity are Ce and Ln, whereas practically no information was found for Nd, Tb, Tm, and Yb. We also discuss the challenges of the research on Ln ecotoxicity, such as relevance of nominal versus bioavailable concentrations of Ln, and point out future research needs (long-term toxicity to aquatic biota and toxic effects of Ln to bottom-dwelling species)

Toxicity of Plastic Additive 1-Hydroxycyclohexyl Phenyl Ketone (1-HCHPK) to Freshwater Microcrustaceans in Natural Water

Various potentially toxic compounds associated with plastic (e.g., plastic additives) can enter the environment during plastic fragmentation and/or weathering. 1-Hydroxycyclohexyl phenyl ketone (1-HCHPK) is a widely used photoinitiator, e.g., in UV-radiation-curable technologies such as 3D-printing, plastic coatings and construction materials. 1-HCHPK may reach aquatic ecosystems via various waste-flows, including leaching from consumer goods. However, knowledge of its potential environmental hazard is scarce. In the present study, we addressed this data gap by assessing the acute and long-term toxicity of 1-HCHPK to freshwater microcrustaceans in environmentally relevant conditions using natural waters. The results showed that the acute toxicity of 1-HCHPK (L(E)C50) to pelagic Thamnocephalus platyurus and Daphnia magna and benthic Heterocypris incongruens ranged between 27 and 55 mg/L. Further, the long-term exposure of D. magna to low levels of 1-HCHPK (0.1 and 1.0 mg/L) did not affect ephippia hatching or organismal fitness, even in three successive daphnid generations. Thus, 1-HCHPK did not pose a hazard to the freshwater microcrustaceans at concentrations < 1 mg/L in the environmentally relevant conditions (i.e., multigenerational life cycle tests conducted in lake water at low chemical exposure concentrations). The tests employed in this study allowed for the environmentally relevant hazard assessment of emerging pollutants such as a plastic additive 1-HCHPK

Toxicity and bioaccumulation of rare earth metals in Daphnia magna

International audienceThe Canadian Rare Earth Element (REE) Network aims producing and processing 20% of the global supply of critical REEs in Canada by 2018 which may lead to increased REE emissions into the environment. The potential hazard of elevated concentrations of REEs to biota is still insufficiently investigated and is fraught with potential methodological problems. In the current presentation, three aspects of REEs toxicity to Daphnia magna will be discussed: 1) effect of test medium on acute toxicity of REE; 2) chronic toxicity of REE; 3) toxicity and bioaccumulation of REE rich rock leachates. Daphnia magna is a particle-feeding zooplankton species with high potential of accumulating REEs. Acute and chronic toxicity of La, Ce, Pr, Nd and Gd nitrates to D. magna was evaluated according to OECD202 and OECD 211 guidelines. Acute toxicity was tested in OECD202 artificial freshwater (AFW) and natural lake water and chronic toxicity in natural lake water. To evaluate sedimentation, REEs' content in supernatants was measured by total reflection X-ray fluorescence spectroscopy (TXRF). Acute toxicity (48 h EC50 in mg REE/L) to D. magna, calculated based on nominal metal concentrations, was 19-31 in AFW and >50 in lake water. 48 h EC50 (mg REE/L), based on measured concentrations, was 0.2-1.5 in AFW and >0.2 in lake water. Chronic toxicity to D. magna , evaluated in lake water, was 0.3-0.5 mg REE/L. TXRF analyses showed that sedimentation of REEs was higher in AFW (at low concentrations) and at high test concentrations (in both test media). Bioavailability of REE from rock leachates was measured from REE rich monazite (MON) or allanite (ALA) bearing pegmatite rock material from Quebec (Canada). The materials were leached with artificial rainwater according to ISO/TS 21268-2 guideline. New leachate was produced at 6 leaching cycles performed during 28 days and analysed with ICP-MS and ICP-OES. Filtered eluates from day 1 and 28 were tested for acute toxicity (OECD202) to D. magna and those from day 14 to measure REE bioaccumulation in D. magna. Toxicity was seen only for MON eluates with significantly lower REE concentration compared to ALA. The toxicity did not decrease with weathering despite the decreasing REE content in the leachates. Thus, the toxicity of MON rock eluent was probably not (solely) induced by REE content. REE concentration in the eluates was low (<0.2 mg/L) compared to the concentration in the rocks (7000−12000 mg/kg). Almost no accumulation of REE from rock eluates was seen. In conclusion, in OECD202 and 211 test settings, REE solutions were more stable at low concentrations in organics-containing natural water (environmentally relevant conditions) compared to mineral artificial OECD202 test medium. The release of REEs from rock material in the leaching tests was low and decreased in time. Toxicity of rock eluents to Daphnia magna was not (only) related to REE content but (also) to additional factors that are yet to be specified. This work was supported by Estonian Research Council grant IUT23-5. The authors would like to acknowledge support by the COST Action TD1407 by means of a STSM Grant to Marge Muna

Changes in the canopies of Pinus sylvestris and Picea abies under alkaline dust impact in the industrial region of Northeast Estonia

Studies were carried out in 1999, 2005 and 2007 in the area of Kunda cement plant in Northeast Estonia on sample plots 3 km W and 2.5 and 5 km E of Kunda. As control stands, two plots for pine and spruce were established in Lahemaa National Park (34–38kmWof Kunda). The selected pine and spruce stands were 75–85-year-old Myrtillus site type, of 0.7–0.8 density and II quality class, with moderately dense or sparse understorey. The values concerning needle density and number of needle scars were higher for shoots formed in the period of higher pollution than for the shoots grown under a considerably lower pollution load. Although the cement dust pollution has notably decreased from year to year, the number of needle pairs per 1 cm of the shoot was 1.8–2.1 times greater in the shoots formed in 1998 than in those formed in 2003, whereas the changes were statistically reliable. Possibly the low temperatures at the time of shoot and needle formation affected the density of needles on all sample plots, and thus the number of needles on shoots formed in 2003 was many times smaller. After the significant fall in the pollution load since 1996 the length growth of needles intensified around Kunda cement plant, at the same time no changes occurred in the length growth of needles in the control area. As compared to the data from 1998, the length growth of pine needles had improved, especially 2.5 and 5 km E from the cement plant, needles being respectively 1.5 and 1.1cm longer than 6 years ago. The stimulation of the growth of pine and spruce needles 2.5 and 5 km E of the cement plant may be a sign of a positive effect of reduced doses of cement dust in soil. The greater length of pine and spruce needles is the reason for the larger biomass of the needlesVytauto Didžiojo universitetasŽemės ūkio akademij

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

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

Mapping the patchy legislative landscape of non-native tree species in Europe

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