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.

Spatially explicit information on forest management at a global scale is critical for understanding the status of forests, for planning sustainable forest management and restoration, and conservation activities. Here, we produce the first reference data set and a prototype of a globally consistent forest management map with high spatial detail on the most prevalent forest management classes such as intact forests, managed forests with natural regeneration, planted forests, plantation forest (rotation up to 15 years), oil palm plantations, and agroforestry. We developed the reference dataset of 226 K unique locations through a series of expert and crowdsourcing campaigns using Geo-Wiki (https://www.geo-wiki.org/). We then combined the reference samples with time series from PROBA-V satellite imagery to create a global wall-to-wall map of forest management at a 100 m resolution for the year 2015, with forest management class accuracies ranging from 58% to 80%. The reference data set and the map present the status of forest ecosystems and can be used for investigating the value of forests for species, ecosystems and their services.

Carbon dioxide (CO2) and methane (CH4) are recognized as the main greenhouse gases causing climate warming. In forest ecosystems, the death of trees leads to the formation of coarse woody debris (CWD) that is one of the sources of greenhouse gas emissions due to wood decomposition. We quantified the CO2 and CH4 fluxes from CWD of larch (Larix gmelinii (Rupr.)) and birch (Betula tortuosa Ledeb.) collected in the northern boreal forests of Central Siberia. The CWD samples were incubated at +5, +15 and +25 °C. The CO2 and CH4 fluxes showed strong correlations with temperature, moisture, decomposition stage and the type of wood’s rot. The temperature coefficient Q10 indicated higher temperature sensitivity of CO2 flux within the temperature interval from +5 to +15 °C than from +15 to +25 °C. Methane flux had higher temperature sensitivity within the interval from +15 to +25 °C. It was found that, in boreal forests, CWD of early decay stage can serve as a source of methane to the atmosphere when air temperatures increased above +15 °C. Strong positive correlation between CH4 production and CO2 emission indicated a biological source and supported findings on aerobic origin of the main process contributing to the CH4 flux from decomposing CWD.

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In boreal forests developed on permafrost, landslide processes are widespread. They occur primarily in years of above average summer-autumn precipitation and can cover up to 20% of total area of slopes adjacent to rivers. Permafrost landslides will escalate with climate change. These processes are the most destructive natural disturbance events and result in complete disappearance of initial ecosystems (vegetation cover and soil). We have studied sites of landslides of different ages along the Nizhnyaya Tunguska River and the Kochechum River (key site Tura) to analyze postsliding ecosystem succession. Just after the event (as at the 1-year-old site), as compared to the non-affected control site we registered a drop in soil respiration, a 3 times lower microbial respiration rate, and a 4 times smaller mineral soil C and N content at G-plots-bare soil (melkozem) at middle location of a site. Results show that regeneration of soil respiration and ecophysiological status of microbial communities in soil during post disturbance succession starts with re-establishment of the vegetation and the following accumulation of the organic soil layer. During the 35-years succession under observation the, at the oldest site the accumulated litter contained similar C and N stocks as the control sites. However, the mineral soil C and N stocks and the microbial biomass even of the oldest landslide area did not reach the value of these parameters in control plots. We conclude that forested ecosystems in permafrost area disturbed after landsliding require decades for final successful restoration. In addition, the degradation of permafrost due to landslides clearly hinders the accumulation of soil organic matter in the mineral soil.