Forest biomass is an essential indicator for monitoring the Earth’s ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world’s forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities.

One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness.

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Background: Being the product of the same environment, soil and vegetation are mutually associated with each other, but the relationships between edaphic properties and vegetation characteristics are still far from clear. Accordingly, the specific aim of this study is to identify relationships between forest site types/forest types and the fertility of soil organic horizons in northwestern Russia. The relationships were assessed at the level of three large forest regions, the northern and middle taiga of the Republic of Karelia, and the Karelian Isthmus (Leningrad region), based on 37 spruce, 66 pine, and 16 birch plots which were integrated with the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). Results: Soil forming rock and land-use history partly explain the differences in the fertility of soil organic horizons between the forest ecosystems in northwestern Russia. Climatic factors are closely correlated with plant species richness, density and the fertility of soil organic horizons. Nutrient content in the organic horizons increased from poor to rich site types identified according to composition of understory vegetation and the occurrence of certain indicator species, i.e. Cajander's forest site types. The most informative parameters in explaining differences between Cajander's types were nitrogen, carbon to nitrogen ratio, exchangeable calcium, magnesium, potassium, and base saturation. Extractable phosphorus, carbon to nitrogen ratio, exchangeable calcium, magnesium, aluminum and base saturation were the most informative parameters in explaining differences between forest types identified within the Cajander types in accordance with the tree species composition, i.e. Sukachev's forest types. The organic horizons of spruce and birch-dominated forests contained significantly more nutrients, compared to those dominated by pine. These differences were explained by differences in litter quality, and the crown shape and density of tree species, which affect the intensity of nutrient leaching. Conclusions: The study presents new findings regarding the relationships between forest sites/types and the fertility of soil organic horizons in northwestern Russia. Differences in organic horizon's fertility between the taiga subzones are explained by differences in the soil forming rock, climatic conditions, land-use history and shares of forest site types/forest types.

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The objective of this study was to compare ecophysiological and morphological parameters of a regionally endangered orchid species, Epipactis atrorubens (Hoffm. ex Bernh.) Bess., growing in two forest communities (on serpentine and granite outcrops) of the Middle Urals, Russia. Biodiversity, dominance, and phytocoenosis studies showed the colonization of a wide range of plant species on both sites. The physicochemical properties of the soil, chemical composition and morphological features of E. atrorubens, growing under technogenic conditions (asbestos deposits), on serpentine outcrops and in the natural environment of the granite massif were studied for the first time. The serpentine substrate differed from the granite one by its greater stoniness, circumneutral pH and lower contents of available nitrogen and phosphorus. Extremely high concentrations of magnesium were found in the serpentine soil, some 79 times higher than in the granite substrate. High concentrations of nickel (94 times), chromium (59 times), cobalt (17 times), and iron (4 times) were found in the serpentine substrate, higher than in the granite substrate. The differences between the sites for available metal contents and for root and shoot metal contents were significantly less. Concentrations of most of the metals in the roots were higher than in the shoots. Despite higher metal concentrations and lower nitrogen and phosphorus levels in serpentine soils, E. atrorubens had a larger population and greater viability compared to those growing on granite. Plants on serpentine outcrops were characterized by the formation of a larger number of fruits, greater root lengths and thicker leaf blades, compared to plants on granites. The well-developed orchid mycorrhizae contributed to the survival of this species under unfavorable serpentine conditions. Hence, serpentine outcrops formed due to the mining of asbestos could be a suitable substrate for the light-demanding E. atrorubens due to its capacity to adapt to dry, rocky, nutrient-depleted soils and limited competition from other plants.

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