Search

Aims: We asked how geological substrate affects the distribution of plant species between forest interiors, forest edges, and steppe patches in the forest–steppe landscapes. Specifically, we sought for the presence of the edge effect at the forest–grassland transitions on different substrates. Location: Austria, Czech Republic, Hungary, Slovakia and western Ukraine. Methods: We recorded the occurrence of vascular plant species in forest interiors, at forest edges and in steppe patches on 40 forest–steppe sites located on four substrates (andesite, dolomite, limestone and loess). We compared the distribution of species diversity, beta diversity (using multivariate analysis), the number of shared species between habitats and the estimation of vegetation biomass among forest‐steppe habitats on different substrates. Results: The edge effect was observed on hard rocks, while it was absent on loess, where the ecotone species richness was intermediate between that of forest and steppe. Loess sites also had the lowest species turnover between forest and steppe and the lowest number of edge specialists. Conclusions: Substrate has a strong effect on the formation of forest–steppe mosaics. It shapes the assembly rules and plant community diversity within individual habitat mosaics. Plant communities on each substrate can respond differently to changing climate. The strong assembly rules on hard rocks may be more likely to result in species loss than on loess or similar soft sediments, where a larger number of species find their optimum in more than one forest–steppe habitat. [ABSTRACT FROM AUTHOR]

The launch of gravity-dedicated satellite missions at the beginning of the new millennium led to an accuracy improvement of global Earth gravity field models (GGMs). One of these missions was the Gravity field and steady-state Ocean Circulation Explorer (GOCE) launched in 2009. As the first European Space Agency's Earth Explorer Mission, the satellite carried a novel instrument, a 3-D gradiometer, which allowed measurement of the second-order directional derivatives of the gravitational potential (gravitational gradients) with a uniform quality and a near-global coverage. The main mission goal was to determine the static Earth's gravity field with the ambitious precision of 1-2 cm in terms of geoid heights and 1 mGal in terms of gravity anomalies for spatial resolution of 100 km (half wavelength at the equator). More than three years of the outstanding measurements resulted in three levels of data products (Level 0, Level 1b and Level 2), six releases of GGMs, and several global grids of gravitational gradients. The grids, which represent a step between gravitational gradients measured directly along the GOCE orbit and those represented by GGMs, found their usage mainly in geophysical applications. In this contribution, we validate the official Level 2 product GRD_SPW_2 using height anomalies over two test areas located in central and northern Europe (Czechia/Slovakia and Norway). A mathematical model based on the least-squares spectral weighting is employed with corresponding spectral weights estimated for validation of gravitational gradient grids. This model continues gravitational gradients from the mean orbital altitude of GOCE down to the irregular Earth's surface (not to a sphere) and transforms them to height anomalies in one computational step. Analytical downward continuation errors of the model are estimated using a closed-loop test. Prior to the comparison of height anomalies estimated from gravitational gradients with their reference values derived from Global Navigation Satellite Systems (GNSS)/levelling over the two test areas, the gravitational gradients and reference data are corrected for all systematic effects such as the tide system conversion. Moreover, the high-frequency part of the gravitational signal is estimated and subtracted from reference data as it is attenuated in the gravitational gradients measured by GOCE. A relative improvement between the release 6 and release 2 gradient grids reaches 48 % in terms of height anomalies in Czechia/Slovakia. The relative improvement in Norway is even more significant and reaches 55 % . The release 6 of the official Level 2 product GRD_SPW_2 gained the absolute accuracy with the standard deviation of 8.7 cm over Czechia/Slovakia and 9.3 cm over Norway. Article Highlights: A mathematical model based on the least-squares spectral weighting for validation of the official Level 2 product GRD_SPW_2 is presented Possibilities of the spectral combination method for the downward continuation of gravitational gradients and their transformation into height anomalies are investigated A review of quality of the official Level 2 product GRD_SPW_2 with respect to GNSS/levelling points over two test areas (Czechia/Slovakia and Norway) is provided [ABSTRACT FROM AUTHOR]