Chemical profiles in sediment and basalt at DSDP Hole 74-525A

Forty sediment and four basement basalt samples from DSDP Hole 525A, Leg 74, as well as nine basalt samples from southern and offshore Brazil, were subjected to instrumental neutron activation analysis. Thirty-two major, minor, and trace elements were determined. The downcore element concentration profiles and regression analyses show that the rare earth elements (REE) are present in significant amounts in both the carbonate and noncarbonate phases in sediments; Sr is concentrated in the carbonate phase, and most of the other elements determined exist mainly in the noncarbonate phase. The calculated partition coefficients of the REE between the carbonate phase and the free ion concentrations in seawater are high and increase with decreasing REE ionic radii from 3.9 x 10**6 for La to 15 x 10**6 for Lu. Calculations show that the lanthanide concentrations in South Atlantic seawater have not been changed significantly over the past 70 Ma. The Ce anomaly observed in the carbonate phase is a redox indicator of ancient seawater. Study of the Ce anomaly reveals that seawater was anoxic over the Walvis Ridge during the late Campanian. As the gap between South America and West Africa widened and the Walvis Ridge subsided from late Campanian to late Paleocene times, the water circulation of the South Atlantic improved and achieved oxidation conditions about 54 Ma that are similar to present seawater redox conditions in the world oceans. The chemical compositions of the basement rocks correspond to alkalic basalts, not mid-ocean ridge basalts (MORBs). The results add more evidence to support the hypothesis that the Walvis Ridge was formed by a series of volcanos moving over a "hot spot" near the Mid-Atlantic Ridge. From the chemical composition and REE pattern, one 112 Ma old basalt on the Brazilian continental shelf has been identified as an early stage MORB. To date, this is the oldest oceanic tholeiite recovered from the South Atlantic. This direct evidence indicates that the continental split between South America and Africa commenced > 112 Ma.

Geospatial analysis of groundwater depth for manual well drilling suitability in the Zinder Region, Niger

Manual and low-tech well drilling techniques have potential to assist in reaching the United Nations' millennium development goal for water in sub-Saharan Africa. This study used publicly available geospatial data in a regression tree analysis to predict groundwater depth in the Zinder region of Niger to identify suitable areas for manual well drilling. Regression trees were developed and tested on a database for 3681 wells in the Zinder region. A tree with 17 terminal leaves provided a range of ground water depth estimates that were appropriate for manual drilling, though much of the tree's complexity was associated with depths that were beyond manual methods. A natural log transformation of groundwater depth was tested to see if rescaling dataset variance would result in finer distinctions for regions of shallow groundwater. The RMSE for a log-transformed tree with only 10 terminal leaves was almost half that of the untransformed 17 leaf tree for groundwater depths less than 10 m. This analysis indicated important groundwater relationships for commonly available maps of geology, soils, elevation, and enhanced vegetation index from the MODIS satellite imaging system.

Table 1: Soil chemical properties of the analysed depth profiles in the Venice lagoon

Visual traces of iron reduction and oxidation are linked to the redox status of soils and have been used to characterise the quality of agricultural soils.We tested whether this feature could also be used to explain the spatial pattern of the natural vegetation of tidal habitats. If so, an easy assessment of the effect of rising sea level on tidal ecosystems would be possible. Our study was conducted at the salt marshes of the northern lagoon of Venice, which are strongly threatened by erosion and rising sea level and are part of the world heritage 'Venice and its lagoon'. We analysed the abundance of plant species at 255 sampling points along a land-sea gradient. In addition, we surveyed the redox morphology (presence/absence of red iron oxide mottles in the greyish topsoil horizons) of the soils and the presence of disturbances. We used indicator species analysis, correlation trees and multivariate regression trees to analyse relations between soil properties and plant species distribution. Plant species with known sensitivity to anaerobic conditions (e.g. Halimione portulacoides) were identified as indicators for oxic soils (showing iron oxide mottles within a greyish soil matrix). Plant species that tolerate a low redox potential (e.g. Spartina maritima) were identified as indicators for anoxic soils (greyish matrix without oxide mottles). Correlation trees and multivariate regression trees indicate the dominant role of the redox morphology of the soils in plant species distribution. In addition, the distance from the mainland and the presence of disturbances were identified as tree-splitting variables. The small-scale variation of oxygen availability plays a key role for the biodiversity of salt marsh ecosystems. Our results suggest that the redox morphology of salt marsh soils indicates the plant availability of oxygen. Thus, the consideration of this indicator may enable an understanding of the heterogeneity of biological processes in oxygen-limited systems and may be a sensitive and easy-to-use tool to assess human impacts on salt marsh ecosystems.

Meteorological data, stem radius measurements (SR) and derivates of SR of the three Swiss forest sites Visp, Davos and Lägeren

. Separating continuously measured stem radius (SR) fluctuations into growth-induced irreversible stem expansion (GRO) and tree water deficit-induced reversible stem shrinkage (TWD) requires a concept to decide on potential growth processes during periods of shrinking and expanding SR below a precedent maximum. Here we investigated two physiological concepts: the linear growth (LG) concept assuming linear growth vs. the zero growth (ZG) concept assuming no growth during periods of shrunken stems. . We evaluated the physiological mechanisms underlying these two concepts and assessed the respective plausibility with SR data obtained from 15 deciduous and evergreen trees. . The LG concept showed steady growth rates, whereas the ZG concept showed strongly varying growth rates over time, more in accordance with mechanistic expectations. Further, growth increased for maximally 120 min after periods of shrunken stems, indicating limited growth activity during that period. However, the fraction of this extra growth was found to be small. Furthermore, TWD of the ZG concept was better explained by a hydraulic plant model than TWD of the LG concept. . We conclude that periods of shrunken stems allow for very little growth in the four tree species investigated. However, further studies should focus on obtaining independent growth data to ultimately validate these findings.

Pollen and macrofossil profiles from six cores in Illinois, U.S.A

Pollen analysis of Wisconsinan sediments from eleven localities in northern and central Illinois, combined with the results of older studies, allows a first general survey of the vegetational changes in Illinois during the last glaciation. In the late Altonian (after 40,000 B.P.), pine was already the most prevalent tree type in northern Illinois. Probably because of the influence of the last Altonian ice advance to northern Illinois, pine migrated to the south and reached south-central Illinois, which was at that time a region of prairie, with oak and hickory trees in favorable sites. Likewise in the late Altonian, spruce appeared in northern Illinois. Spruce also expanded its area to the south during the Wisconsinan, reaching south-central Illinois only after 21,000 B.P., in the early Woodfordian. Deciduous trees (predominantly oak) were present in south-central Illinois throughout the Wisconsinan. Their prevalence decreased to the north. The vegetation during the different subdivisions of the last glacial period in Illinois was approximately as follows: Late Altonian: Pine/spruce forest with some deciduous trees in northern and central Illinois; prairie and oak/hickory stands in south-central Illinois; immigration of pine. Farmdalian: Pine/spruce forest in central Illinois; deciduous trees and pine in south-central Illinois, with areas of open vegetation, perhaps similar to the present-day transition of prairie to forest in the northern Great Plains. Woodfordian: Northern and central Illinois ice covered; in south central Illinois, spruce and oak as dominant tree types, but also pine and grassland. During the Woodfordian, pine and spruce disappeared again from south-central Illinois, and oak/hickory forest and prairie again prevailed. The ice-free areas of northern Illinois become populated temporarily with spruce, but later there is proof of deciduous forest in this region. Pollen investigations in south-central Illinois have shown convincingly that deciduous trees could survive relatively close (less than 60 km) to the ice margin. Therefore the frequently presented view that arctic climatic conditions prevailed in North America during the last glaciation far south of the ice margin can be refuted for the Illinois area, confirming the opinion of other authors resulting from investigations of fossil mollusks and frost-soil features. The small number of localities investigated still permits no complete reconstruction of the vegetation zones and their possible movements in Illinois. During the Altonian and Farmdalian in Illinois, a vegetational zonation probably existed similar to that of today in North America. As the ice pushed southward as far as 39° 20' N. lat in the early Woodfordian, this zonation was apparently broken up under the influence of a relatively moderate climate. In any case, the Vandalia area, which was only about 60 km south of the ice, was at that time neither in a tundra zone nor in a zone of boreal coniferous forest.

Vegetation community and geochemistry in the Uummannaq District, West Greenland

Beach and salt marsh vegetation of the Uummannaq District, northern West Greenland (c. 70°15' N - 72° N, 49° W - 54° W) was studied 1998 according to the Braun-Blanquet phytosociological approach. Habitat analyses included soil chemistry. Such vegetation locally occurs and is not developed over extensive areas. On gravely stony beaches a Mertensia maritima ssp. maritima community occurs, while a Honckenya peploides var. diffusa community is confined to sandy beaches. The association Honckenyo diffusae-Elymetum mollis Thannh. 1975 is confined to sandy shore walls and low dunes. All vegetation types are assigned to the alliance Honckenyo- Elymion arenariae Tx. 1966, which again is a unit of the order Honckenyo- Elymetalia arenariae Tx. 1966, which is sub ordered to the class Honckenyo-Elymetea arenariae Tx. 1966. On fine sediments along sheltered coasts salt marsh vegetation is locally developed mainly on fiord deltas and outwash plains of small rivers and streams. A distinct zonation pattern in vegetation can be observed from the lower to upper salt marsh: Puccinellietum phryganodis Hadac 1946 association, Caricetum subspathaceae Hadac 1946 association, Caricetum ursinae Hadac 1946 association (all assigned to the alliance Puccinellion phryganodis Hadac 1946) and Festuco-Caricetum glareosae Nordh. 1954 association (assigned to the alliance Armerion maritimae Br.-Bl. et de Leeuw 1936). Both alliances are units of the order Glauco- Puccinellietalia Beeftink et Westhoff in Beeftink 1965, which is assigned to the class Asteretea tripolii Westhoff et Beeftink in Beeftink 1962. TWINSPAN and CCA support the vegetation classification and the CCA with soil chemistry parameters shows that salinity (related to position above MHW) and Ncontent are strongly correlated with the floristical differentiation of the vegetation of the Honckenyo-Elymetea class. In the Asteretea tripolii class, position above MHW (negatively correlated with pH, conductivity and Clcontent) and fresh water supply are likely the main factors, which affect vegetation differentiation. A synoptic survey of vegetation types from Greenland based on published phytosociological tables is presented and distribution of the vegetation types is addressed, just as their position in a circumpolar context. Moreover a Cochlearia groenlandica-Melandrium triflorum community is described as a new vegetation type, occurring on shallow soil on cliffs influenced by salt spray.

Undergrowth removal in Salgesch: Soil volumetric water content and temperature time series, hourly time resolution, 2010-2015

In the Salgesch forest in the Canton of Valais in Switzerland, the understory has been removed to test whether effects on pine tree vitality. The data set published here compromises 120 time series of 60 soil temperature and 60 volumetric water content (VWC) sensors (EC-TM and 5-TM) (Decagon Devices, WA, USA) at three soil depth levels (5, 30, 60 cm) employed in the direct vicinity of six control trees and six trees with the undergrowth removed. At the levels 5 and 60 cm, three replications were made whereas 4 replications were made at level 30 cm. Six loggers recorded hourly data since 2010 with 18% gaps or 11% when not considering winter months December, January and February. The figure attached to this repository shows the average VWC and temperature of all measurements within the same depth and treatment specific setting aggregated in a defined time interval and period. In addition to that, the standard deviations are plotted as transparent polygons. In case of insufficient values for calculating standard deviations, the setting specific mean standard deviation of the considered time period are inserted.