NE Germany Research Articles

Forest continuity, soil depth and tree species are important parameters for SOC stocks in an old forest (Templiner Buchheide, northeast Germany)

Forest mineral soils have the potential to accumulate large amounts of carbon (C). Numerous factors, which have often been insufficiently studied, affect soil organic C (SOC) stocks. Detailed knowledge of variation in SOC storage is important to assess the C accumulation potential of forest soils. To examine the impacts of forest continuity, soil depth and tree species on SOC stocks, 15 ancient (>230years of forest continuity) and 15 old (>100 but <200years of forest continuity) forest soils, topsoil and subsoil in the Templiner Buchheide (Brandenburg, NE Germany) were compared. The old forest sites were afforested on former grassland or wasteland. On all sites grew one of three dominant tree species: European beech (Fagus sylvatica), Scots pine (Pinus sylvestris) or oak (Quercus spec.). Pine forest sites had been underplanted with beech and were mixed-species stands. Soil samples were taken down to a mean depth of 55cm. Total contents of SOC, nitrogen (N), phosphorus (P), sulphur (S), calcium (Ca), potassium (K) and magnesium (Mg); soil pH; and bulk densities were determined.The soils of ancient forest sites stored significantly more total SOC, N, P, S, K and Mg than did the old ones. Mean total SOC stocks in ancient forests of all three tree species were 12–17% larger compared with those in old forests. Significant differences in SOC stocks between the two forest continuity groups appeared only in subsoil and not in topsoil. Pine forest stored larger SOC stocks than did beech and oak forests. Significant differences were found between ancient pine and oak forests and between ancient beech and oak forests. Soils in ancient beech and pine forests at depths of between 29 and 55cm contained, on average, even 50% larger SOC stocks than did soils at the same depths in ancient oak forests and in all old forests.Forest continuity significantly affected SOC stocks. These results support previous studies that old forests are still able to enrich SOC. Although soil samples were carried out to a mean depth of only 55cm, the results indicate that differences in SOC stocks between ancient and old forest could also be found in deeper soil layers. It was suggested that beech and mixed-species stands of beech and pine and total soil P stocks had a positive effect on SOC stocks in subsoil. To understand SOC accumulation in forests, especially in subsoil, with a forest continuity of >100years, the role of different tree species and of total P cycling in forests, deeper sampling depths and repeated sampling would be required.

Combining a root exclusion technique with continuous chamber and porous tube measurements for a pin‐point separation of ecosystem respiration in croplands

AbstractTo better assess ecosystem C budgets of croplands and understand their potential response to climate and management changes, detailed information on the mechanisms and environmental controls driving the individual C flux components are needed. This accounts in particular for the ecosystem respiration (Reco) and its components, the autotrophic (Ra) and heterotrophic respiration (Rh) which vary tremendously in time and space. This study presents a method to separate Reco into Ra [as the sum of Ra (shoot) and Ra (root)] and Rh in order to detect temporal and small‐scale spatial dynamics within their relative contribution to overall Reco. Thus, predominant environmental drivers and underlying mechanisms can be revealed. Reco was derived during nighttime by automatic chamber CO2 flux measurements on plant covered plots. Rh was derived from CO2 efflux measurements, which were performed in parallel to Reco measurements on a fallow plot using CO2 sampling tubes in 10 cm soil depth. Ra (root) was calculated as the difference between sampling tube CO2 efflux measurements on a plant covered plot and Rh. Ra (shoot) was calculated as Reco – Ra (root) – Rh. Measurements were carried out for winter wheat (Triticum aestivum L.) during the crop season 2015 at an experimental plot located in the hummocky ground moraine landscape of NE Germany. Reco varied seasonally from &lt; 1 to 9.5 g C m−2 d−1, and was higher in adult (a) and reproductive (r) than juvenile (j) stands (g C m−2 d−1: j = 1.2, a = 4.6, r = 5.3). Observed Ra and Rh were in general smaller compared to the independently measured Reco, contributing in average 58% and 42% to Reco. However, both varied strongly regarding their environmental drivers and particular contribution throughout the study period, following the seasonal development of soil temperature and moisture (Rh) as well as crop development (Ra). Thus, our results consistently revealed temporal dynamics regarding the relative contribution of Ra (root) and Ra (shoot) to Ra, as well as of Ra and Rh to Reco. Based on the observed results, implications for partitioning of Reco in croplands are given.

Variability of soil carbon stocks in a mixed deciduous forest on hydromorphic soils

Forests play an important role for carbon (C) storage and a large part of C in forest ecosystems is stored in the soil. Although large-scale inventories of soil C stocks have been published recently, detailed site-specific studies are still needed because C storage depends on various site specific soil, ecological and management factors. Quantification of soil C stocks is hampered by spatial and temporal variability. Here, we assess C stocks in an ancient forest site at a stand which has not been managed for >60years and analyse the spatial variability of C concentrations and stocks to evaluate inter-annual variability and elucidate possible causes. Samples were taken down to 1m depth by auger cores in May of three consecutive years (2013, 2014, 2015) on regular hexagonal grids covering an area of 0.25ha and 19 sampling spots. In addition, to address small scale variability, 36 auger cores were taken in November 2014 using a nested sampling design.C stocks were on average 34kgCm−2 (0–1m depth). This is distinctly higher than soil C stocks reported for most other forest sites in similar climatic conditions, and is likely caused by the interplay of several parameters, i.e., hydromorphic soil conditions, high biomass production due to high soil fertility, stand structure (tree age, species and density), and the management history of the site. The coefficients of variation for C concentrations (>50%) and for C stocks (30–50%) show that spatial variability is high. Geostatistical analysis revealed a larger scale component with ranges of 5–20m and a small scale component represented by high nugget effects in the semivariograms (>50%).As hydromorphic soil types are widespread in NE Germany, large amounts of organic C could be sequestered into soil under unmanaged old forests, thus contributing to alleviating the rise in anthropogenic CO2 concentrations in the atmosphere.

Riverine fen restoration provides secondary habitat for endangered and stenotopic rove beetles (Coleoptera: Staphylinidae)

Abstract Peatlands have undergone dramatic changes through anthropogenic activities in the last centuries, causing a substantial loss of fen‐specific biodiversity. Therefore, restoration of already degraded stands is an important conservation issue. The effectiveness of fen restoration was evaluated through rewetting in the valley of the river Peene, NE Germany, by comparing three fen types: drained fens, rewetted fens, and near‐natural fens. Rove beetles (Coleoptera: Staphylinidae) were used as indicators, comprising an ecologically important yet understudied insect group. 5,398 individuals from 121 staphylinid species were recorded by 30 pitfall traps per fen type, which were biweekly emptied between April and October 2012, and related to environmental parameters. Rove beetle assemblages differed markedly between fen types. Community structure was affected by peat degradation, the extent of organic matter, water level, and vegetation height. Fen rewetting favoured the establishment of a distinct, species‐rich beetle community within 15 years only, caused by an increase in hygrophilous wetland species partially replacing generalists. Nevertheless, this time span was not sufficient to restore communities characteristic for near‐natural fens, which harboured several particularly sensitive species that were not found on rewetted fens. Rewetting provided suitable habitats for a substantial number of stenotopic and threatened staphylinid beetles. Thus, the protection of pristine habitats along with restoration measures are both important strategies in peatland conservation.

Long-term soil hydrological data of a Pleistocene region in North-East Germany

Long-term soil hydrological studies were carried out at the ZALF Muencheberg Experimental Station. Muencheberg is located in a Pleistocene end moraine landscape in NE Germany about 50 km east of Berlin and 40 km west of the Oder river, the border with Poland. The soils are formed on Pleistocene parent material, classified as Haplic Albeluvisol with a Bt horizon mostly beginning at about 70 cm depth. From 1994-1999 the site was used as arable land managed by different farming systems (integrated, integrated with irrigation, ecological and low input). From 2000 to 2005 the effect of different tillage systems (plough and no till) was investigated. Furthermore, soil water was extracted by use of suction cups for analysing the soil water nitrate concentrations. The data were used for quantifying deep drainage rates and nitrate losses as described in (Schindler and Mueller, 2008 and Schindler et al., 2010). All basic data (soil water content, tension, precipitation, potential evapotranspiration and soil water nitrate concentrations) are accessible via DOI 10.4228/ZALF.1995.282.

Palaeoecological investigations and 230Th/U dating of the Eemian Interglacial peat sequence from Neubrandenburg-Hinterste Mühle (Mecklenburg-Western Pomerania, NE Germany)

The Eemian Interglacial sequence was explored in the gravel pit ‘Neubrandenburg-Hinterste Mühle’ near Neubrandenburg (NE Germany). The sequence is situated in a former kettle hole depression between underlying Late Saalian till (s. str. Warthe) covered by a Late Weichselian till. Today still visible a 3 m long and max. 2 m wide profile is located on the edge of the former Eemian depression. The limnic sedimentation began during the Late Saalian in a landscape characterized by open herbaceous vegetation. Cool, clear and calcium carbonate-rich lake water dominated, inhabited by Characeae that indicates a presence of stonewort meadows, most typical of waters up to 10 m in depth. The beginning of the Eemian Interglacial succession was characterized by a dominance of scarce birch forest followed by pine forest. The beginning of the mesocratic phase of the Eemian was characterized by the appearance of warm climate indicators and by the development of thermophilic forest communities dominated by oak forest with the appearance of warm climate indicators. The ensuing climate optimum was defined by the encroachment of hazel-oak forest and later by mixed deciduous forest. Limnic sedimentation ceased in the basin during this phase and the end of predominantly limnic conditions is marked by a decrease in the frequency of aquatic plants and an increase in the amount of brown mosses. During the interglacial optimum mixed forests reigned. This phase bears a record of oligotrophication leading to transition mire and raised bog and the aquatic plants vanished. The depression gradually became shallower and was overgrown by a forest cover. During the telocratic phase of the Eemian, communities with pine, birch and fir spread. The end of the interglacial was characterized by a disappearance of the riparian forest and a sporadic appearance of reedswamp plants. At the beginning of the Early Weichselian, a deterioration of climatic conditions resulted in the formation of widespread heaths on acid soils and trees disappeared. In the studied basin the water level fluctuated. The Hinterste Mühle sequence shows the development of a small kettle hole lake and its transformation to an overgrowing mire, including terrestrialization processes, during the Eemian Interglacial. The U/Th data obtained for five samples from the upper part of the studied profile, which have been analyzed by the TSD technique, has yielded an age of 116 ± 13/10 kyr. This date reflects the classification into the second half of the Eemian Interglacial and the Early Weichselian for the upper part of peat formation.

Divergent NEE balances from manual‐chamber CO2 fluxes linked to different measurement and gap‐filling strategies: A source for uncertainty of estimated terrestrial C sources and sinks?

AbstractManual closed‐chamber measurements are commonly used to quantify annual net CO2 ecosystem exchange (NEE) in a wide range of terrestrial ecosystems. However, differences in both the acquisition and gap filling of manual closed‐chamber data are large in the existing literature, complicating inter‐study comparisons and meta analyses. The aim of this study was to compare common approaches for quantifying CO2 exchange at three methodological levels. (1) The first level included two different CO2 flux measurement methods: one via measurements during mid‐day applying net coverages (mid‐day approach) and one via measurements from sunrise to noon (sunrise approach) to capture a span of light conditions for measurements of NEE with transparent chambers. (2) The second level included three different methods of pooling measured ecosystem respiration (RECO) fluxes for empirical modeling of RECO: campaign‐wise (19 single‐measurement‐day RECO models), season‐wise (one RECO model for the entire study period), and cluster‐wise (two RECO models representing a low and a high vegetation status). (3) The third level included two different methods of deriving fluxes of gross primary production (GPP): by subtracting either proximately measured RECO fluxes (direct GPP modeling) or empirically modeled RECO fluxes from measured NEE fluxes (indirect GPP modeling). Measurements were made during 2013–2014 in a lucerne‐clover‐grass field in NE Germany. Across the different combinations of measurement and gap‐filling options, the NEE balances of the agricultural field diverged strongly (–200 to 425 g CO2‐C m−2). NEE balances were most similar to previous studies when derived from sunrise measurements and indirect GPP modeling. Overall, the large variation in NEE balances resulting from different data‐acquisition or gap‐filling strategies indicates that these methodological decisions should be made very carefully and that they likely add to the overall uncertainty of greenhouse gas emission factors. Preferably, a standard approach should be developed to reduce the uncertainty of upscaled estimates.

Exceptionally preserved Leptolepidae (Actinopterygii, Teleostei) from the late Early Jurassic Fossil-Lagerstätten of Grimmen and Dobbertin(Mecklenburg-Western Pomerania, Germany).

Exceptionally well-preserved fishes of the family Leptolepidae (Actinopterygii, Teleostei) from the late Early Jurassic Fossil-Lagerstätten of Grimmen and Dobbertin (Mecklenburg-Western Pomerania, NE Germany) are reported and detailed anatomical descriptions are given. The described material specifically derives from the "Green Series", which represents a specific facies that falls within the lower part of the early Toarcian Harpoceras falciferum ammonite Zone. Complete skeletons are rare, and most specimens are represented by isolated skulls. Most of the skulls are fully articulated and show only a low degree of compaction, while some specimens are almost three-dimensionally preserved. The leptolepid fauna comprises Leptolepis coryphaenoides, L. normandica, L. jaegeri, a possible Proleptolepis, and two other taxa, which are described in open nomenclature. Several anatomical characters, such as the shape of premaxilla, maxilla, dentary, preopercle, the cephalic sensory canals, and the dentition of the jaws, are discussed and compared to former studies. The new material provides novel insights into morphology, diversity and palaeobiogeography of leptolepid fishes. The records of Leptolepis coryphaenoides, L. normandica and L. jaegeri from Grimmen and Dobbertin represent the northeastern-most occurrences of these species from Europe, suggesting that they inhabited the whole central European epicontinental sea during the early Toarcian. The possible occurrence of Proleptolepis in the lower Toarcian of Grimmen suggests that this genus might have had a much wider palaeobiogeographical and temporal distribution, since specimens attributed to Proleptolepis have previously been reported only from the Sinemurian of western Europe.

Long term subfossil Cladocera record from the partly varved sediment of Lake Tiefer See (NE Germany)

&lt;p&gt;The partly varved and well-dated sediment record of Lake Tiefer See (NE Germany) allowed the high resolution paleolimnological reconstruction of the lake evolution during the whole Holocene. This paper presents results of subfossil Cladocera analysis. During the Holocene, the fauna of subfossil cladoceran was represented by 36 species belonging to 6 families. Cladocera were dominated by typical open-water species, belonging especially of the Bosminidae family. The sediment record of Lake Tiefer See exhibited distinct decadal- to centennial-scale alternations of well- and non-varved intervals, which were related to changes in the thermal circulation of the lake water column. In general, well varved sediments were deposited during periods of reduced lake circulation, and were characterised by maximum abundance of Cladocera, whereas non-varved sedimentation phases occurred during periods of increased lake circulation and showed a lower number of Cladocera specimens. The most suitable conditions for the development of cladoceran fauna occurred during the early Holocene and from ~ 2055 – 725 yr cal BP. On the basis of the increasing number of species associated with high lake productivity, eight stages of increasing trophy were inferred. The first two were attributed to climate warming, while the next six to human impact. Higher human driven trophic conditions of Lake Tiefer See occurred in the periods 5750-5500 and 4500-4100 yr cal BP, and four times from 1000 to50 yr cal BP. During the last 750 years and in the period from 6000 to 2500 yr cal BP, the species of &lt;em&gt;Eubosmina&lt;/em&gt; produced extreme morphs. The cyclomorphosis of &lt;em&gt;Eubosmina &lt;/em&gt;was likely connected to more pronounced changes in the lake environmental conditions.&lt;/p&gt;

Paying the colonization credit: converging plant species richness in ancient and post-agricultural forests in NE Germany over five decades

Massive historical land cover changes in the Central European lowlands have resulted in a forest distribution that now comprises small remnants of ancient forests and more recently established post-agricultural forests. Here, land-use history is considered a key driver of recent herb-layer community changes, where an extinction debt in ancient forest remnants and/or a colonization credit in post-agricultural forests are being paid over time. On a regional scale, these payments should in theory lead toward a convergence in species richness between ancient and post-agricultural forests over time. In this study, we tested this assumption with a resurvey of 117 semi-permanent plots in the well-studied deciduous forests of the Prignitz region (Brandenburg, NE Germany), where we knew that the plant communities of post-agricultural stands exhibit a colonization credit while the extinction debt in ancient stands has largely been paid. We compared changes in the species richness of all herb layer species, forest specialists and ancient forest indicator species between ancient and post-agricultural stands with linear mixed effect models and determined the influence of patch connectivity on the magnitude of species richness changes. Species richness increased overall, but the richness of forest specialists increased significantly more in post-agricultural stands and was positively influenced by higher patch connectivity, indicating a convergence in species richness between the ancient and post-agricultural stands. Furthermore, the richness of ancient forest indicator species only increased significantly in post-agricultural stands. For the first time, we were able to verify a gradual payment of the colonization credit in post-agricultural forest stands using a comparison of actual changes in temporal species richness.

Late Saalian and Weichselian glaciations in the German Baltic Sea documented by Pleistocene successions at the southeastern margin of the Arkona Basin

Seismic profiles and numerous sediment cores of a planned offshore wind farm area northeast of Rügen Island provide a unique insight into the distribution and thickness of glacial deposits in the southern Baltic Sea. Fine gravel analysis enabled recognition of five tills that correspond to different ice advances. On the basis of a 3D structural model, the main Pleistocene events could be reconstructed and correlated with stratigraphical records in the circum‐Baltic area comprising Marine Isotope Stages (MIS) 6 to 2. The oldest till was deposited during the Late Saalian Warthe advance (qs2; c. 150–130 ka). It is only preserved in ENE–WSW trending subglacial channels incised into Upper Cretaceous soft chalk. Isolated rafts and remnants of two Middle Weichselian tills occur locally, whereas Eemian interglacial sediments are missing. The older till (qw*) has an unusual fine gravel composition and might have formed during ice advances known only from northern Denmark and northern Poland (c. 65–60 ka). The younger till represents the Warnow advance (qw0) in NE Germany that can be correlated with the Danish Ristinge advance (c. 55–50 ka). Furthermore, two tills deposited during the Late Weichselian Last Glacial Maximum (c. 24–16 ka) occur. One can be correlated with the Pomeranian advance (qw2), while the other has characteristics typical for the Mecklenburg advance (qw3). These advances eroded older Pleistocene deposits, thus probably also removing the till of the Brandenburg/Frankfurt advance (qw1) – in contrast to the onshore areas. The Pomeranian till is limited to the southeast, close to the shallow Adlergrund, but the Mecklenburg till covers the whole study area. This first detailed lithostratigraphical classification of till units from the Arkona Basin allows for the identification and correlation of Pleistocene successions in other parts of the southern Baltic Sea.

Discussing surface crack structures in the Schorfheide region, NE Germany

Abstract. Express Report

Effects of spring warming and mixing duration on diatom deposition in deep Tiefer See, NE Germany

Monitoring during three meteorologically different spring seasons in 2012, 2013, and 2014 revealed that temperature increase in spring, which influences spring lake mixing duration, markedly affected nutrient availability and diatom deposition in a sediment trap close to the bottom of deep Tiefer See, NE Germany. Deposition of Stephanodiscus taxa and small Cyclotella taxa was much higher after late ice out and a deep, short lake mixing period in spring 2013, compared to that after gradual warming and lengthy lake mixing periods in spring 2012 and 2014, when only brief or marginal ice cover occurred. Availability of dissolved Si and P was 33 and 20 % higher, respectively, in 2013 compared to 2014. The observed relation between high (low) diatom deposition and short (lengthy) mixing duration in spring was applied to varved sediments deposited between AD 1924 and 2008. Low detrital Si content in trapped material and a sediment core enabled use of µXRF-counts of Si as a proxy for diatom silica. The spring mixing duration for 1951–2008 was derived from FLake-model calculations. The spring warming duration related to lake mixing was approximated from air temperatures for 1924–2008 using the dates when daily mean air temperature exceeded 5 °C (start) and 10 °C (end). Diatom silica deposition showed a significant (p < 0.0001) inverse linear relationship with the modeled spring mixing duration (R2 = 0.36) and the spring warming duration (R2 = 0.28). In both cases, the relationship is strengthened when data from the period of low diatom production (1987–2005) is excluded (R2 = 0.59 and R2 = 0.35). Part of this low diatom production is related to external nutrient supply that favored growth of cyanobacteria at the expense of diatoms. This approach shows that diatom Si deposition was strongly influenced by the availability of light and nutrients, related to the duration of lake mixing and warming in spring, during most of the studied period. The remaining unexplained variability, however, indicates that additional factors influence Si deposition. Further tests in other deep, temperate lakes are necessary to verify if this relation is a common feature and consequently, if diatom Si can be used as a proxy for spring mixing duration in such lakes.

Land-use and hydroperiod affect kettle hole sediment carbon and nitrogen biogeochemistry

Kettle holes are glaciofluvially created depressional wetlands that collect organic matter (OM) and nutrients from their surrounding catchment. Kettle holes mostly undergo pronounced wet-dry cycles. Fluctuations in water table, land-use, and management can affect sediment biogeochemical transformations and perhaps threaten the carbon stocks of these unique ecosystems. We investigated sediment and water of 51 kettle holes in NE Germany that differ in hydroperiod (i.e. the duration of the wet period of a kettle hole) and land-use. Our objectives were 1) to test if hydroperiod and land management were imprinted on the isotopic values (δ13C, δ15N) and C:N ratios of the sediment OM, and 2) to characterize water loss dynamics and kettle hole-groundwater connectivity by measuring the stable δ18O and δD isotope values of kettle hole water over several years. We found the uppermost sediment layer reflected recent OM inputs and short-term processes in the catchment, including land-use and management effects. Deeper sediments recorded the degree to which OM is processed within the kettle hole related to the hydroperiod. We see clear indications for the effects of wet-dry cycles for all kettle holes, which can lead to the encroachment of terrestrial plants. We found that the magnitude of evaporation depended on the year, season, and land-use type, that kettle holes are temporarily coupled to shallow ground water, and, as such, kettle holes are described best as partially-closed to open systems.

Varve microfacies and varve preservation record of climate change and human impact for the last 6000 years at Lake Tiefer See (NE Germany)

The Holocene sediment record of Lake Tiefer See exhibits striking alternations between well-varved and non-varved intervals. Here, we present a high-resolution multi-proxy record for the past ~6000 years and discuss possible causes for the observed sediment variability. This approach comprises microfacies, geochemical and microfossil analyses and a multiple dating concept including varve counting, tephrochronology and radiocarbon dating. Four periods of predominantly well-varved sediment were identified at 6000–3950, 3100–2850 and 2100–750 cal. a BP and AD 1924–present. Except of sub-recent varve formation, these periods are considered to reflect reduced lake circulation and consequently, stronger anoxic bottom water conditions. In contrast, intercalated intervals of poor varve preservation or even extensively mixed non-varved sediments indicate strengthened lake circulation. Sub-recent varve formation since AD 1924 is, in addition to natural forcing, influenced by enhanced lake productivity due to modern anthropogenic eutrophication. The general increase in periods of intensified lake circulation in Lake Tiefer See since ~4000 cal. a BP presumably is caused by gradual changes in the northern hemisphere orbital forcing, leading to cooler and windier conditions in Central Europe. Superimposed decadal- to centennial-scale variability of the lake circulation regime is likely the result of additional human-induced changes of the catchment vegetation. The coincidence of major non-varved periods at Lake Tiefer See and intervals of bioturbated sediments in the Baltic Sea implies a broader regional significance of our findings.

Visualizing land‐use and management complexity within biogeochemical cycles of an agricultural landscape

AbstractCrop fields are cultivated across continuities of soil, topography, and local climate that drive biological processes and nutrient cycling at the landscape scale; yet land management and agricultural research are often performed at the field scale, potentially neglecting the context of the surrounding landscape. Adding to this complexity is the overlap of ecosystems and their biogeochemical legacies, as a patchwork of crops fields, natural grasslands, and forests develops across the landscape. Furthermore, as new technologies and policies are introduced, management practices change, including fertilization strategies, which further alter biological productivity and nutrient cycling. All of these environmental, biological, and historical legacies are potentially recorded in the isotopic signal of plant, soil, and sediment organic matter across the landscape. We mapped over 1500 plant, soil, and sediment isotopic values and generated an isotopic landscape (isoscape) over a 40‐km2 agricultural site in NE Germany. We observed distinct patterns in the isotopic composition of organic matter sampled from the landscape that clearly reflect the landscape complexity. C3 crop intrinsic water‐use efficiency reflected a precipitation gradient, while native forest and grassland plant species did not, suggesting that native plants are more adapted to predominant climatic conditions. δ13Csoil patterns reflected both the long‐term input of plant organic matter, which was affected by the local climate conditions, and the repeated cultivation of corn. Soil organic matter 15N isotopic values also revealed spatial differences in fertilization regimes. Forest fragments, in which the nitrogen cycle was relatively open, were more water‐use efficient. Sediments from small water bodies received substantial inputs from surrounding field vegetation but were also affected by seasonal drying. These isotopic maps can be used to visualize large spatial heterogeneity and complexity, and they are a powerful means to interpret past and current trends in agricultural landscapes.

As time goes by—Spatiotemporal changes of biogenic Si pools in initial soils of an artificial catchment in NE Germany

Accumulation and recycling of biogenic silicon (BSi) in terrestrial ecosystems influence fluxes of dissolved Si from the continents to the oceans, thus act as a filter in the global Si cycle. Although the biogenic control mechanism especially of phytogenic Si pools (phytoliths) has been generally recognized since decades quantitative information on other terrestrial BSi pools is surprisingly rare. For the first time terrestrial protophytic (diatom frustules), protozoic (testate amoeba shells) and zoogenic (sponge spicules) Si pools were quantified in soils of initial ecosystem states. We analyzed spatiotemporal changes of these Si pools in differently aged soils of the artificial catchment ‘Chicken Creek’ in NE Germany. Within a relatively short time span (<10 years) of ecosystem development protophytic, protozoic and zoogenic Si pool sizes increased markedly, whereat protozoic Si pools were the smallest ones with a maximum of 6.2mgm−2. Zoogenic Si pool size (max. 22.6mgm−2) is comparable to the one of protophytic Si pools (max. 30.5mgm−2) although only few sponge spicules (n=10) and spicule fragments (n=2) were found. Differences in quantities, dynamics and resistibility against dissolution of various BSi pools indicate their possibility to influence biogeochemical Si cycling relatively rapid (protophytic and protozoic Si pools) or slow (zoogenic Si pool). Spatiotemporal changes of protophytic and protozoic Si pools within the first decade of ecosystem development seem to be mainly controlled by (biotic) small-scale environmental conditions (e.g., vegetation, food sources).

A matter of dispersal: REVEALSinR introduces state-of-the-art dispersal models to quantitative vegetation reconstruction

The REVEALS model is applied in quantitative vegetation reconstruction to translate pollen percentage data from large lakes and peatlands into regional vegetation composition. The model was first presented in 2007 and has gained increasing attention. It is a core element of the Landcover 6k initiative within the PAGES project. The REVEALS model has two critical components: the pollen dispersal model and pollen productivity estimates (PPEs). To study the consequences of model settings, we implemented REVEALS in R. We use a state-of-the-art Lagrangian stochastic dispersal model (LSM) and compare model outcomes with calculations based on a conventional Gaussian plume dispersal model (GPM). In the LSM turbulence causes pollen fall speed to have little effect on the dispersal pattern whereas fall speed is a major factor in the GPM. Dispersal models are also used to derive PPEs. The unrealistic GPM produces PPEs that do not describe actual pollen productivity, but rather serve as a basin specific correction factor. A test with pollen and vegetation data from NE Germany shows that REVEALS performs best when applied with the LSM. REVEALS applications with the GPM can produce realistic results, but only if unrealistic PPEs are used. We discuss the derivation of PPEs and further REVEALS applications. Our REVEALS implementation is freely available as the ‘REVEALSinR’ function within the R package DISQOVER. REVEALSinR offers an environment for experimentation and analysing model sensitivities. We encourage further experiments and welcome comments on our tool.

Contributions to the European Pollen Database. 32. Endinger Bruch EB25 (NE Germany): from fen to bog

The Endinger Bruch (54° 14ʹ N, 12° 53ʹ E) is a large alder carr in northern Vorpommern (Western Pomerania, northeast Germany). Geomorphology and late-glacial vegetation history of the area are desc...

Contributions to the European Pollen Database. 31. Endinger Bruch ‘Hoher Birkengraben’ (NE Germany): from lake to carr

The Endinger Bruch (54° 14ʹ N, 12° 53ʹ E) is a large alder carr in northern Vorpommern (Western Pomerania, northeast Germany). Its central part consists of a c. 1 km wide former lake basin includin...