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In this Letter, the middle initial of author G. J. Nabuurs was omitted, and he should have been associated with an additional affiliation: ‘Forest Ecology and Forest Management Group, Wageningen University and Research, Wageningen, The Netherlands’ (now added as affiliation 182). In addition, the following two statements have been added to the Supplementary Acknowledgements. (1): ‘We would particularly like to thank The French NFI for the work of the many field teams and engineers, who have made extraordinary efforts to make forest inventory data publicly available.’ (1): ‘Sergio de Miguel benefited from a Serra- Húnter Fellowship provided by the Generalitat of Catalonia.’ Finally, the second sentence of the Methods section should have cited the French NFI, which provided a national forestry database used in our analysis, to read as follows: ‘The GFBi database consists of individual-based data that we compiled from all the regional and national GFBi forest-inventory datasets, including the French NFI (IGN—French National Forest Inventory, raw data, annual campaigns 2005 and following, https://inventaire-forestier.ign.fr/spip.php?rubrique159, site accessed on 01 January 2015)’. All of these errors have been corrected online. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.

The first aim of this Ph.D. thesis is to investigate the impact of selective logging, which alter forest dynamics and cause loss of functional species, and could seriously affect tropical forests under a changing climate. I carried out researches on African tropical forests trying to find a significant answer to this issue. My findings suggest that the vertical structure of the logged forest are not largely different from those of a primary forest, while a remarkable difference in forest density, synthesized in some indicators, together with a concomitant invasion by vines, climbers and other weeds is pointed out. I show that the effects on species richness and biomass are greater than those expected from the simple removal of commercial species, implying that selective logging, unless it is practiced very carefully at very low harvest intensities, may significantly reduce the biomass density of a tropical forest for time scales spanning decades, and possibly longer, seriously diminishing the aboveground carbon storage and richness of the forest. Then, I present a simple deterministic model that describes the dynamics of tropical rainforest subject to selective logging to understand how and why weeds displace native species. I argue that the selective removal of tallest tropical trees carries out gaps of light that allow weeds, vines and climbers to prevail on native species, inhibiting the possibility of recovery of the original vegetation. The second aim of this Ph.D. thesis is to understand the relations between forest structure, productivity and biodiversity. By studying tropical forest of Africa and of the Earth I tried to shed light on competing hypothesis and to develop a unified theory which could explain the relations between forest structure, niche volume, climate and biodiversity. Ishow that there is a global positive correlation between forest canopy height and biodiversity and that it follows a latitudinal gradient. I combined the species pool size and the fractal nature of ecosystems to clarify some general patterns of this gradient. Finally, for the third purpose of the Ph.D. researches, I compared growth trends of old trees born in the pre-industrial age (17th century) with those of younger trees born in the modern age (20th century) to evaluate the changing forests behavior under a modified atmospheric chemistry. I show, as preliminary results, that the Sapele and Ayous species (African tropical forests) increased their growth trends during the last century (from 1900). Il primo obiettivo di questo dottorato di ricerca è quello di indagare l'impatto del taglio selettivo, che altera le dinamiche forestali e causa la perdita di specie funzionali, e potrebbe compromettere seriamente le foreste tropicali in un clima che cambia. Ho effettuato ricerche sulle foreste tropicali africane cercando di trovare una risposta significativa a questo problema. I miei risultati suggeriscono che la struttura verticale della foresta tagliata selettivamente non è molto diversa da quella di una foresta primaria, mentre è riscontrabile una notevole differenza di densità delle foreste, sintetizzabile in alcuni indicatori, insieme a un invasione concomitante di infestanti. Qui io mostro che gli effetti sulla ricchezza di specie e la biomassa sono maggiori di quelli attesi dalla semplice rimozione di specie commerciali, il che implica che il taglio selettivo, a meno che non sia praticato con molta attenzione a intensità di estrazione molto basse, può ridurre significativamente la densità di biomassa di una foresta tropicale per scale di tempo superiori ai decenni, e seriamente ridurre il deposito di carbonio nel soprasuolo (biomassa vegetale) e la ricchezza specifica del bosco. Poi, presento un modello deterministico semplice che descrive la dinamica di foresta pluviali tropicali soggette a taglio selettivo per capire come e perché le infestanti soppiantano le specie autoctone. Io sostengo che la rimozione selettiva di alti alberi tropicali crea gaps di luce che permettono alle infestanti e rampicanti di “soffocare” le specie autoctone, inibendo la possibilità di recupero della vegetazione originaria. Il secondo obiettivo di questo dottorato di ricerca è di comprendere le relazioni tra struttura del bosco, produttività e biodiversità. Studiando le foreste tropicali dell'Africa e della Terra ho cercato di fare luce sulle ipotesi concorrenti e di sviluppare una teoria unificata che potrebbe spiegare le relazioni tra struttura della foresta, volume di nicchia, clima e biodiversità. In questa parte mostro che esiste una correlazione positiva tra l'altezza globale della copertura forestale e la biodiversità e che questa relazione segue un gradiente latitudinale. Ho combinato la dimensione del pool di specie e la natura frattale degli ecosistemi per chiarire alcuni modelli generali di questo gradiente. Infine, per il terzo scopo del Dottorato di ricerca, ho confrontato i trend di crescita degli alberi secolari nati nell'era pre-industriale (17° secolo) con quelli di giovani alberi nati in età moderna (20° secolo), per valutare il comportamento delle foreste sotto una chimica atmosferica modificata. Mostro, come risultato preliminare, che le specie Sapele e Ayous (delle foreste tropicali africane) hanno aumentato le loro tendenze di crescita nel corso dell'ultimo secolo (dal 1900 in poi). Dottorato di ricerca in Ecologia forestale

This paper, developed under the framework of the RECCAP initiative, aims at providingimproved estimates of the carbon and GHG (CO2, CH4and N2O) balance of continentalAfrica. The various components and processes of the African carbon and GHG bud-get were considered, and new and available data derived by different methodologies (based on inventories, ecosystem fluxes, models, and atmospheric inversions) wereintegrated. The related uncertainties were quantified and current gaps and weaknessin knowledge and in the monitoring systems were also considered in order to provideindications on the future requirements. The vast majority of the results seem to agreethat Africa is probably a small sink of carbon on an annual scale, with an average value of−0.61±0.58 PgCyr−1. Nevertheless the emissions of CH4and N2O may turn Africainto a source in terms of CO2equivalents. At sub-regional level there is a significantspatial variability in both sources and sinks, mainly due to the biome’s differences andthe different anthropic impacts, with southern Africa as the main source and centralAfrica, with its evergreen tropical forests, as the main sink. Emissions from land use change in Africa are significant (around 0.32±0.05 PgCyr−1) and even higher than thefossil fuel ones; this is a unique feature among all the continents. In addition there canbe significant carbon losses from land even without changes in the land use (forest),as results from the impact of selective logging. Fires also play a significant role, with1.03±0.22 PgCyr−1of carbon emissions, mainly (90 %) originated by savanna and woodland burning. But whether fire carbon emissions are compensated by CO2up-take during the growing season, or are a non-reversible loss of CO2, remains unclear.Most of these figures are subjected to a significant interannual variability, on the orderof±0.5 PgCyr−1in standard deviation, accounting for around 25 % of the year-to-yearvariation in the global carbon budget. These results, even if still highly uncertain, show the important role that Africa playsin the carbon cycle at global level, both in terms of absolute values and variability, Biogeosciences Discussions, 10, ISSN:1810-6277, ISSN:1810-6285

This paper, developed under the framework of the RECCAP initiative, aims at providing improved estimates of the carbon and GHG (CO2, CH4 and N2O) balance of continental Africa. The various components and processes of the African carbon and GHG budget are considered, existing data reviewed, and new data from different methodologies (inventories, ecosystem flux measurements, models, and atmospheric inversions) presented. Uncertainties are quantified and current gaps and weaknesses in knowledge and monitoring systems described in order to guide future requirements. The majority of results agree that Africa is a small sink of carbon on an annual scale, with an average value of −0.61 ± 0.58 Pg C yr−1. Nevertheless, the emissions of CH4 and N2O may turn Africa into a net source of radiative forcing in CO2 equivalent terms. At sub-regional level, there is significant spatial variability in both sources and sinks, due to the diversity of biomes represented and differences in the degree of anthropic impacts. Southern Africa is the main source region; while central Africa, with its evergreen tropical forests, is the main sink. Emissions from land-use change in Africa are significant (around 0.32 ± 0.05 Pg C yr−1), even higher than the fossil fuel emissions: this is a unique feature among all the continents. There could be significant carbon losses from forest land even without deforestation, resulting from the impact of selective logging. Fires play a significant role in the African carbon cycle, with 1.03 ± 0.22 Pg C yr−1 of carbon emissions, and 90% originating in savannas and dry woodlands. A large portion of the wild fire emissions are compensated by CO2 uptake during the growing season, but an uncertain fraction of the emission from wood harvested for domestic use is not. Most of these fluxes have large interannual variability, on the order of ±0.5 Pg C yr−1 in standard deviation, accounting for around 25% of the year-to-year variation in the global carbon budget. Despite the high uncertainty, the estimates provided in this paper show the important role that Africa plays in the global carbon cycle, both in terms of absolute contribution, and as a key source of interannual variability., Biogeosciences, 11 (2), ISSN:1726-4170

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., Proceedings of the National Academy of Sciences of the United States of America, 119 (6), ISSN:0027-8424, ISSN:1091-6490

Maps represent powerful tools to show the spatial variation of a variable in a straightforward manner. A crucial aspect in map rendering for its interpretation by users is the gamut of colours used for displaying data. One part of this problem is linked to the proportion of the human population that is colour blind and, therefore, highly sensitive to colour palette selection. The aim of this paper is to present a function in R - \texttt{cblind.plot} - which enables colour blind people to just enter an image in a coding workflow, simply set their colour blind deficiency type, and immediately get as output a colour blind friendly plot. We will first describe in detail colour blind problems, and then show a step by step example of the function being proposed. While examples exist to provide colour blind people with proper colour palettes, in such cases (i) the workflow include a separate import of the image and the application of a set of colour ramp palettes and (ii) albeit being well documented, there are many steps to be done before plotting an image with a colur blind friendly ramp palette. The function described in this paper (\ttt{cblind.plot}), on the contrary, allows to (i) automatically call the image inside the function without any initial import step and (ii) explicitly refer to the colour blind deficiency type being experienced, to further automatically apply the proper colour ramp palette.

Tropical deforestation is well known to have serious negative consequences for biodiversity, terrestrial carbon sinks and the balance of atmospheric greenhouse gases. By contrast, selective logging of tropical forests is often regarded as having a lesser impact on the ecosystem particularly in long terms, even though there have been few critical evaluations of the practice, particularly in Africa. We compared field data from 511 plots in the tropical forest of Sierra Leone, Ghana, Cameroon and Gabon. These plots were subject to different forest management practices: no recent logging (primary forests), selective logging (up to 30years old) and re-grown secondary forests post clear-cutting (at least 20years ago). Our findings suggest that the vertical structure and plant richness of the selectively logged and secondary forests change in different amplitude from those of primary forests, but stem density and the prevalence of vine and weed species differ greatly. We show that the effects of selective logging are greater than those expected simply from the removal of commercial species, and can persist for decades. Selective logging, unless it is practiced at very low harvest intensities, can significantly reduce the biomass of a tropical forest for many decades, seriously diminishing aboveground carbon storage capacity, and create opportunities for weeds and vines to spread and slow down the ecological succession.

Treeline shift and tree growth often respond to climatic changes and it is critical to identify and quantify their dynamics. Some regions are particularly sensitive to climate change and the Altai Mountains, located in Central and East Asia, are showing unequivocal signs. The mean annual temperature in the area has increased by 1.3–1.7 °C in the last century. As this mountain range has ancient and protected forests on alpine slopes, we focus on determining the treeline structure and dynamics. We integrated in situ fine-scale allometric data with analyses from dendrochronological samples, high-resolution 3D drone photos and new satellite images to study the dynamics and underlying causal mechanisms of any treeline movement and growth changes in a remote preserved forest at the Aktru Research Station in the Altai Mountain. We show that temperature increase has a negative effect on mountain tree growth. In contrast, only younger trees grow at higher altitudes and we document a relatively fast upward shift of the treeline. During the last 52 years, treeline moved about 150 m upward and the rate of movement accelerated until recently. Before the 1950s, it never shifted over 2150–2200 m a.s.l. We suggest that a continuous upward expansion of the treeline would be at the expense of meadow and shrub species and radically change this high-mountain ecosystem with its endemic flora. This documented treeline shift represents clear evidence of the increased velocity of climate change during the last century.