Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment

Understanding the controls on event-driven dissolved organic carbon (DOC) export is crucial as DOC is an important link between the terrestrial and the aquatic carbon cycles. We hypothesized that topography is a key driver of DOC export in headwater catchments because it influences hydrological connectivity, which can inhibit or facilitate DOC mobilization. To test this hypothesis, we studied the mechanisms controlling DOC mobilization and export in the Große Ohe catchment, a forested headwater in a mid-elevation mountainous region in southeastern Germany. Discharge and stream DOC concentrations were measured at an interval of 15 min using in situ UV-Vis (ultraviolet–visible) spectrometry from June 2018 until October 2020 at two topographically contrasting subcatchments of the same stream. At the upper location (888 m above sea level, a.s.l.), the stream drains steep hillslopes, whereas, at the lower location (771 m a.s.l.), it drains a larger area, including a flat and wide riparian zone. We focus on four events with contrasting antecedent wetness conditions and event size. During the events, in-stream DOC concentrations increased up to 19 mg L−1 in comparison to 2–3 mg L−1 during baseflow. The concentration–discharge relationships exhibited pronounced but almost exclusively counterclockwise hysteresis loops which were generally wider in the lower catchment than in the upper catchment due to a delayed DOC mobilization in the flat riparian zone. The riparian zone released considerable amounts of DOC, which led to a DOC load up to 7.4 kg h−1. The DOC load increased with the total catchment wetness. We found a disproportionally high contribution to the total DOC export of the upper catchment during events following a long dry period. We attribute this to the low hydrological connectivity in the lower catchment during drought, which inhibited DOC mobilization, especially at the beginning of the events. Our data show that not only event size but also antecedent wetness conditions strongly influence the hydrological connectivity during events, leading to a varying contribution to DOC export of subcatchments, depending on topography. As the frequency of prolonged drought periods is predicted to increase, the relative contribution of different subcatchments to DOC export may change in the future when hydrological connectivity will be reduced more often.</p

Two centuries of masting data for European beech and Norway spruce across the European continent

Tree masting is one of the most intensively studied ecological processes. It affects nutrient fluxes of trees, regeneration dynamics in forests, animal population densities, and ultimately influences ecosystem services. Despite a large volume of research focused on masting, its evolutionary ecology, spatial and temporal variability and environmental drivers are still matter of debate. Understanding the proximate and ultimate causes of masting at broad spatial and temporal scales will enable us to predict tree reproductive strategies and their response to changing environment. Here we provide broad spatial (distribution range-wide) and temporal (century) masting data for the two main masting tree species in Europe, European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H. Karst.). We collected masting data from a total of 359 sources through an extensive literature review and from unpublished surveys. The dataset has a total of 1747 series and 18348 yearly observations from 28 countries and covering a time span of years 1677-2016 and 1791-2016 for beech and spruce, respectively. For each record, the following information is available: identification code; species; year of observation; proxy of masting (flower, pollen, fruit, seed, dendrochronological reconstructions); statistical data type (ordinal, continuous); data value; unit of measurement (only in case of continuous data); geographical location (country, Nomenclature of Units for Territorial Statistics NUTS-1 level, municipality, coordinates); first and last record year and related length; type of data source (field survey, peer reviewed scientific literature, grey literature, personal observation); source identification code; date when data were added to the database; comments. To provide a ready-to-use masting index we harmonized ordinal data into five classes. Furthermore, we computed an additional field where continuous series with length >4 years where converted into a five classes ordinal index. To our knowledge, this is the most comprehensive published database on species-specific masting behaviour. It is useful to study spatial and temporal patterns of masting and its proximate and ultimate causes, to refine studies based on tree-ring chronologies, to understand dynamics of animal species and pests vectored by these animals affecting human health, and it may serve as calibration-validation data for dynamic forest models.The paper was partly funded by the “Fondo di Ricerca Locale 2015-2016” of the University of Torino and by the Stiftelsen Stina Werners fond (grant SSWF 10-1/29-3 to I.D.)

Integrated Monitoring Programm an der Messstelle Forellenbach im Nationalpark Bayerischer Wald

Available from TIB Hannover: RN 8908(2000,383/2002) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Integrated Monitoring Programm an der Messstelle Forellenbach im Nationalpark Bayerischer Wald

Available from TIB Hannover: RN 8908(2000,383/2001) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Integrated Monitoring Programm an der Messstelle Forellenbach im Nationalpark Bayerischer Wald

SIGLEAvailable from TIB Hannover: RN 8908(2000,484) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

Variation of leaf angle distribution quantified by terrestrial LiDAR in natural European beech forest

Leaf inclination angle and leaf angle distribution (LAD) are important plant structural traits, influencing the flux of radiation, carbon and water. Although leaf angle distribution may vary spatially and temporally, its variation is often neglected in ecological models, due to difficulty in quantification. In this study, terrestrial LiDAR (TLS) was used to quantify the LAD variation in natural European beech (Fagus Sylvatica) forests. After extracting leaf points and reconstructing leaf surface, leaf inclination angle was calculated automatically. The mapping accuracy when discriminating between leaves and woody material was very high across all beech stands (overall accuracy = 87.59%). The calculation accuracy of leaf angles was evaluated using simulated point cloud and proved accurate generally (R-2 = 0.88, p &lt; 0.001; RMSE = 8.37 degrees; nRMSE = 0.16). Then the mean (theta(mean)), mode (theta(mode)), and skewness of LAD were calculated to quantify LAD variation. Moderate variation of LAD was found in different successional status stands (theta(mean) is an element of [36.91 degrees, 46.141 degrees,theta(mode) is an element of [17 degrees, 43 degrees] skewness is an element of [0.07, 0.48]). Rather than the previously assumed spherical distribution or reported planophile distribution, here we find that LAD tended towards a uniform distribution in young and medium stands, and a planophile distribution in mature stands. A strong negative correlation was also found between plot theta(mean) and plot median canopy height, making it possible to estimate plot specific LAD from canopy height data. Larger variation of LAD was found on different canopy layers (theta(mean) is an element of [33.64 degrees, 52.97 degrees], theta(mode) is an element of [14 degrees, 64 degrees], skewness is an element of [-0.30, 0.71]). Beech leaves grow more vertically in the top layer, while more obliquely or horizontally in the middle and bottom layer. LAD variation quantified by TL

Errichtung und Betrieb einer Messstelle fuer das ECE-Projekt Integrated Monitoring im Rahmen der ECE-Luftreinhaltekonvention

Since 1990 research stations and permanent plots were installed at Forellenbach area in the National Park Bayerischer Wald and the state of the ecosystem was described in order to provide the basis for long-term integrated monitoring. Immisions are dominated by ozone, sulphur and nitrogen oxides are of low concentrations. Thalli of sensitive lichens show distinct damages. The poor nutrient status of spruce and beech trees regarding calcium and magnesium on acid brown soils corresponds to the above-average portion of distinctively damaged tree individuals. Acid, nitrate and sulfate inputs as well as aluminium released in mineral soils are stored in the subsoil and buffered by silicate weathering respectively. Runoff water is of low ion strength and alkalinity. During snow melt acid and aluminium concentrations in this water increase to harmful levels regarding aquatic biota. Stabilization of this labile ecosystem requires reduced emissions of air pollutants. (orig.)Seit 1990 wurden im Forellenbachgebiet des Nationalparks Bayerischer Wald Messstationen und Dauerbeobachtungsflaechen eingerichtet, die naturraeumliche Ausstattung des Gebietes charakterisiert, und die Basis fuer ein langfristiges integriertes Monitoring gelegt. Das Immissionsklima ist O_3-betont mit geringen SO_2- und NO_x-Konzentrationen. Sensitive Flechtenarten weisen deutliche Thallusschaeden auf. Die schwache Naehrstoffversorgung von Fichten und Buchen v.a. mit Kalzium und Magnesium auf sauren Braunerden aus Fliesserden und Granitersatz korrespondiert mit dem ueberdurchschnittlich hohen Anteil deutlich geschaedigter Baeume. Die Saeure-, Nitrat- und Sulfateintraege und die im Mineralboden freigesetzten Aluminiumionen werden insb. unter Fichte erst im Untergrund gebunden bzw. ueber Silikatverwitterung abgepuffert. Das schwach mineralisierte Vorfluterwasser erreicht bei der Schneeschmelze unphysiologisch niedrige pH-Werte und hohe Aluminiumkonzentrationen. Die Stabilisierung dieses sensiblen Oekosystems erfordert eine weitere Reduzierung der atmosphaerischen Belastung. (orig.)SIGLEAvailable from TIB Hannover: RN 8908(95-057) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

Sulphur and nitrogen input-output budgets at ICP Integrated Monitoring sites in Europe

Vytauto Didžiojo universitetasŽemės ūkio akademij

Sulphur and nitrogen input-output budgets at ICP Integrated Monitoring sites

Vytauto Didžiojo universitetasŽemės ūkio akademij