Storm disturbances in a Swedish forest-A case study comparing monitoring and modelling

A Norway spruce (Picea abies Karst) forest site in southwest Sweden was chosen to study the effects of storm disturbances over the period 1997-2009, during which two storms, 'Lothar' (December 1999) and 'Gudrun' (January 2005), affected the area. Monitored deposition data, soil water chemistry data and forest inventory data were compared with the predictions of an integrated ecosystem model, ForSAFE, in an effort to reveal and understand the effects of storms on acidification/recovery in forest soils. Both storms caused windthrow loss leading to increased nitrate and sulphate concentrations in soil water as a result of stimulated mineralization. Lothar led to increased concentrations of Na+, Mg2+, and Cl- in soil water due to sea-salt episode. No general sea-salt episode was seen following Gudrun, but small sea-salt episodes were observed in 2007 and 2008. Each sea-salt episode caused a temporary decrease of pH, and a subsequent recovery, but overall, the soil water pH decreased from 4.54 to 3.86 after Lothar. Modelling suggested that the site was recovering from acidification from 1990s, and would continue to recover in future. Both modelled and monitored data showed that storm caused disturbances in the recovery; monitored data even suggested that soil acidification happened due to storm disturbances. Sea-salt episode does not increase soil acidity in the long term, and will probably decrease the soil acidity by replenishing the base saturation. The modelled data also suggested that storms with only windthrow would not have effects on soil acidification recovery in the long term, but they may influence the soil fertility by losses of base cations. (C) 2015 Elsevier B.V. All rights reserved

La gestion de la fertilité des sols forestiers est-elle à un tournant ? Une conclusion transitoire

La gestion de la fertilité des sols forestiers est-elle à un tournant ? Une conclusion transitoir

Is the management of forest soil fertility at a turning point? A brief conclusion

Is the management of forest soil fertility at a turning point? A brief conclusio

Cytoplasmic Compartmentalization of the Fetal piRNA Pathway in Mice

Derepression of transposable elements (TEs) in the course of epigenetic reprogramming of the mouse embryonic germline necessitates the existence of a robust defense that is comprised of PIWI/piRNA pathway and de novo DNA methylation machinery. To gain further insight into biogenesis and function of piRNAs, we studied the intracellular localization of piRNA pathway components and used the combination of genetic, molecular, and cell biological approaches to examine the performance of the piRNA pathway in germ cells of mice lacking Maelstrom (MAEL), an evolutionarily conserved protein implicated in transposon silencing in fruit flies and mice. Here we show that principal components of the fetal piRNA pathway, MILI and MIWI2 proteins, localize to two distinct types of germinal cytoplasmic granules and exhibit differential association with components of the mRNA degradation/translational repression machinery. The first type of granules, pi-bodies, contains the MILI-TDRD1 module of the piRNA pathway and is likely equivalent to the enigmatic “cementing material” first described in electron micrographs of rat gonocytes over 35 years ago. The second type of granules, piP-bodies, harbors the MIWI2-TDRD9-MAEL module of the piRNA pathway and signature components of P-bodies, GW182, DCP1a, DDX6/p54, and XRN1 proteins. piP-bodies are found predominantly in the proximity of pi-bodies and the two frequently share mouse VASA homolog (MVH) protein, an RNA helicase. In Mael-mutant gonocytes, MIWI2, TDRD9, and MVH are lost from piP-bodies, whereas no effects on pi-body composition are observed. Further analysis revealed that MAEL appears to specifically facilitate MIWI2-dependent aspects of the piRNA pathway including biogenesis of secondary piRNAs, de novo DNA methylation, and efficient downregulation of TEs. Cumulatively, our data reveal elaborate cytoplasmic compartmentalization of the fetal piRNA pathway that relies on MAEL function

Conventional analysis methods underestimate the plant-available pools of calcium, magnesium and potassium in forest soils

The plant-available pools of calcium, magnesium and potassium are assumed to be stored in the soil as exchangeable cations adsorbed on the cation exchange complex. In numerous forest ecosystems, despite very low plant-available pools, elevated forest productivities are sustained. We hypothesize that trees access nutrient sources in the soil that are currently unaccounted by conventional soil analysis methods. We carried out an isotopic dilution assay to quantify the plant-available pools of calcium, magnesium and potassium and trace the soil phases that support these pools in 143 individual soil samples covering 3 climatic zones and 5 different soil types. For 81%, 87% and 90% of the soil samples (respectively for Ca, Mg and K), the plant-available pools measured by isotopic dilution were greater than the conventional exchangeable pool. This additional pool is most likely supported by secondary non-crystalline mineral phases in interaction with soil organic matter and represents in many cases (respectively 43%, 27% and 47% of the soil samples) a substantial amount of plant-available nutrient cations (50% greater than the conventional exchangeable pools) that is likely to play an essential role in the biogeochemical functioning of forest ecosystems, in particular when the resources of Ca, Mg and K are low

Fertilité chimique des sols forestiers : concepts de base

Les diagnostics de fertilité chimique en forêt assimilent généralement le sol à un réservoir de nutriments disponibles pour les végétaux, quantifié à un instant donné puis comparé à des normes de nutrition établies par essence. Ce concept hérité de l’agronomie est régulièrement mis en défaut et de nombreux écosystèmes forestiers développés sur sols très pauvres chimiquement (notamment en Ca, Mg, K) affichent une production remarquable. L’objectif de cet article est d’illustrer les limites du concept « fertilité = réservoir sol » et de proposer les bases d’un nouveau concept rendant compte de la spécificité de la fertilité chimique des écosystèmes forestiers. Une base de données regroupant les résultats acquis sur 11 sites expérimentaux depuis les années 1970 a été utilisée. Les résultats démontrent que le concept de fertilité chimique des écosystèmes forestiers ne doit pas se limiter à la seule prise en compte des stocks de nutriments disponibles dans les sols mais doit également intégrer la circulation et le recyclage d’éléments propres aux cycles biogéochimiques

Sleep, emotional and behavioral difficulties in children and adolescents.

Links between sleep and psychopathology are complex and likely bidirectional. Sleep problems and alteration of normal sleep patterns have been identified in major forms of child psychopathology including anxiety, depression and attention disorders as well as symptoms of difficulties in the full range. This review summarizes some key findings with regard to the links between sleep and associated difficulties in childhood and adolescence. It then proposes a selection of possible mechanisms underlying some of these associations. Suggestions for future research include the need to 1) use multi-methods to assess sleep; 2) measure sleep in large-scale studies; 3) conduct controlled experiments to further establish the effects of sleep variations on emotional and behavioral difficulties; 4) take an interdisciplinary approach to further understand the links between sleep and associated difficulties

Compensation des exportations minérales et remédiations aux dégradations des sols. Compte rendu de l’atelier 3

Les forêts françaises font face aujourd’hui à des pressions extérieures croissantes. Ces contraintes sont d’ordre nutritionnel ou sylvicole ou climatique et risquent d’impacter la durabilité des écosystèmes forestiers. Le sol peut être impacté, entraînant une dégradation de ses composantes chimique ou physique ou biologique. L’objectif de l’atelier était d’apporter des éléments de connaissance et de débat autour des différents types de dégradation, de remédiation et de restauration des sols. Cet atelier a également permis d’échanger autour de différentes approches permettant de soutenir la productivité forestière, par l’utilisation d’intrants de différentes natures (amendements/cendres, boues de stations d’épuration…) ou par l’utilisation des friches industrielles pour produire de la biomasse

Chemical fertility of forest ecosystems. Part 2: Towards redefining the concept by untangling the role of the different components of biogeochemical cycling

Many forest ecosystems are developed on acidic and nutrient-poor soils and it is not yet clearly understood how forests sustain their growth with low nutrient resources. In forestry, the soil chemical fertility is commonly defined, following concepts inherited from agronomy, as the pool of plant-available nutrients in the soil at a given time compared to the nutritional requirement of the tree species. In this two-part study, Part 1 (Hansson et al., 2020) showed, through the compiled dataset of 49 forest ecosystems in France, Brazil and Republic of Congo, the limits of this definition of soil chemical fertility in forest ecosystem contexts. In this study (Part 2), we investigated the nutrient pools and fluxes between the different ecosystem compartments at 11 of the 49 sites in order to better characterize the role of the biogeochemical cycling of nutrients in the chemical fertility of forest ecosystems, and in particular the roles of the biological and geochemical components of biogeochemical cycling. The analysis of our dataset shows different types of biogeochemical functioning. When the geochemical component (inputs through mineral weathering and/or atmospheric inputs, capillary rise) is predominant, sufficient nutrients are provided to the plant-soil system to ensure tree nutrition and growth. Conversely, when the geochemical component of the cycle brings too few nutrients to the plant-soil system, the biological component (litterfall, plant internal cycling) becomes predominant in tree nutrition and growth. In the latter case, forest production may be high even when pools of nutrients in the soil reservoir are low because small but active nutrient fluxes may continuously replenish the soil reservoir or may directly ensure tree nutrition by bypassing the soil reservoir. This study highlights the necessity to include biogeochemical cycling and recycling fluxes in the definition and diagnosis methods of soil chemical fertility in forest ecosystems. We show that the chemical fertility is not only supported by the soil in forest ecosystem but by the sum of all the ecosystem’s compartments and fluxes between these pools

Chemical fertility of forest ecosystems. Part 1: Common soil chemical analyses were poor predictors of stand productivity across a wide range of acidic forest soils

Forest soil fertility can be defined as a combination of physical, chemical and biological factors characterising the biomass production capacity of the soil. However, numerous ecological variables affect tree growth and the aim of the present study was to investigate the specific influence of soil chemical properties on tree productivity at 49 acidic forest sites. A standardized tree productivity index based on tree height expressed as dominant height of the studied stand divided by maximum tree height observed at the same age for the same species in the same climatic region was firstly computed at each site. This index is assumed to limit the influence of species, ages and climate. A soil database was also compiled with data on soil properties from 47 temperate (France) and two tropical (Congo, Brazil) sites. Data included seven tree species, varying in age from 1 to 175 years. Commonly used indicators such as C:N ratio, soil pH, as well as available and total pools of soil nutrients were compared to the standardized tree productivity index, to find the most reliable indicator(s). Nutrient pools at fixed mineral soil depths (down to 100 cm) were used, as well as (for 11 stands) the depth comprising 95% of fine roots. Our results show that none of the common soil chemical parameters tested in this paper could individually explain stand productivity. Combinations of different parameters were also tested using PCA and they could better explain the variability of the data set but without being able to separate the sites according to their standardized tree productivity index. Moreover, random Forests performed on our dataset were unable to properly predict the standardized tree productivity index. Our results reinforce the idea that the influence of the soil chemical fertility on stand productivity is complex and the soil chemical parameters alone (individually or combined) are poor predictors of tree productivity as assessed by the H0:Hmax index. In this paper we focused on static soil chemical indicator and more dynamic indictors, such as nutrient fluxes involved in the biogeochemical cycles, could better explain stand productivity. A companion paper (Legout et al., 2020) focuses on the connection between productivity and different components of the biogeochemical cycle, using data from 11 of the stands presented in this paper