References of "Van den Bulcke, Jan"
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See detailWood Specific Gravity Variations and Biomass of Central African Tree Species: The Simple Choice of the Outer Wood
Bastin, Jean-François ULg; Fayolle, Adeline ULg; Tarelkin, Yegor et al

in PLoS ONE (2015)

Context: Wood specific gravity is a key element in tropical forest ecology. It integrates many aspects of tree mechanical properties and functioning and is an important predictor of tree biomass. Wood ... [more ▼]

Context: Wood specific gravity is a key element in tropical forest ecology. It integrates many aspects of tree mechanical properties and functioning and is an important predictor of tree biomass. Wood specific gravity varies widely among and within species and also within individual trees. Notably, contrasted patterns of radial variation of wood specific gravity have been demonstrated and related to regeneration guilds (light demanding vs. shade-bearing). However, although being repeatedly invoked as a potential source of error when estimating the biomass of trees, both intraspecific and radial variations remain little studied. In this study we characterized detailed pith-to-bark wood specific gravity profiles among contrasted species prominently contributing to the biomass of the forest, i.e., the dominant species, and we quantified the consequences of such variations on the biomass. Methods: Radial profiles of wood density at 8% moisture content were compiled for 14 dominant species in the Democratic Republic of Congo, adapting a unique 3D X-ray scanning technique at very high spatial resolution on core samples. Mean wood density estimates were validated by water displacement measurements. Wood density profiles were converted to wood specific gravity and linear mixed models were used to decompose the radial variance. Potential errors in biomass estimation were assessed by comparing the biomass estimated from the wood specific gravity measured from pith-to-bark profiles, from global repositories, and from partial information (outer wood or inner wood). Results: Wood specific gravity profiles from pith-to-bark presented positive, neutral and negative trends. Positive trends mainly characterized light-demanding species, increasing up to 1.8 g.cm-3 per meter for Piptadeniastrum africanum, and negative trends characterized shade-bearing species, decreasing up to 1 g.cm-3 per meter for Strombosia pustulata. The linear mixed model showed the greater part of wood specific gravity variance was explained by species only (45%) followed by a redundant part between species and regeneration guilds (36%). Despite substantial variation in wood specific gravity profiles among species and regeneration guilds, we found that values from the outer wood were strongly correlated to values from the whole profile, without any significant bias. In addition, we found that wood specific gravity from the DRYAD global repository may strongly differ depending on the species (up to 40% for Dialium pachyphyllum). Main conclusion: Therefore, when estimating forest biomass in specific sites, we recommend the systematic collection of outer wood samples on dominant species. This should prevent the main errors in biomass estimations resulting from wood specific gravity and allow for the collection of new information to explore the intraspecific variation of mechanical properties of trees. [less ▲]

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See detailDensity variations and their influence on carbon stocks: case-study on two Biosphere Reserves in the Democratic Republic of Congo
De Ridder, Maaike; de Haulleville, Thalès ULg; Kearsley, Elizabeth et al

Poster (2014, April 28)

It is commonly acknowledged that allometric equations for aboveground biomass and carbon stock estimates are improved significantly if density is included as a variable. However, not much attention is ... [more ▼]

It is commonly acknowledged that allometric equations for aboveground biomass and carbon stock estimates are improved significantly if density is included as a variable. However, not much attention is given to this variable in terms of exact, measured values and density profiles from pith to bark. Most published case-studies obtain density values from literature sources or databases, this way using large ranges of density values and possible causing significant errors in carbon stock estimates. The use of one single fixed value for density is also not recommended if carbon stock increments are estimated. Therefore, our objective is to measure and analyze a large number of tree species occurring in two Biosphere Reserves (Luki and Yangambi). Nevertheless, the diversity of tree species in these tropical forests is too high to perform this kind of detailed analysis on all tree species (> 200/ha). Therefore, we focus on the most frequently encountered tree species with high abundance (trees/ha) and dominance (basal area/ha) for this study. Increment cores were scanned with a helical X-ray protocol to obtain density profiles from pith to bark. This way, we aim at dividing the tree species with a distinct type of density profile into separate groups. If, e.g., slopes in density values from pith to bark remain stable over larger samples of one tree species, this slope could also be used to correct for errors in carbon (increment) estimates, caused by density values from simplified density measurements or density values from literature. In summary, this is most likely the first study in the Congo Basin that focuses on density patterns in order to check their influence on carbon stocks and differences in carbon stocking based on species composition (density profiles ∼ temperament of tree species). [less ▲]

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See detailExploring ancient charcoal archives in Central Africa
Hubau, Wannes; Morin-Rivat, Julie ULg; Van den Bulcke, Jan et al

Conference (2012, July)

Fossil pollen and charcoal fragments are preserved in lake sediments, in forest soils and in ancient human settlements, were they can be accompanied by artifacts. As such, vegetation history is remarkably ... [more ▼]

Fossil pollen and charcoal fragments are preserved in lake sediments, in forest soils and in ancient human settlements, were they can be accompanied by artifacts. As such, vegetation history is remarkably well archived and sometimes closely linked to cultural history. Direct evidence for Central African vegetation history has been mainly derived from pollen analysis, while the charcoal archive remains hardly explored. However, analysis of charred wood remains has proven worthwhile for palaeovegetation reconstructions in temperate and arid regions. One of the main challenges for charcoal identification in tropical regions is species diversity. Therefore we developed and present a transparent charcoal identification protocol within an umbrella database of species names and metadata, compiled from the on-line database of wood-anatomical descriptions (InsideWood), the database of the world’s largest reference collection of Central African wood specimens (RMCA, Tervuren, Belgium) and inventory and indicator species lists. We applied the protocol on radiocarbon dated charcoal collections sampled in the Mayumbe forest (Bas-Congo, DRCongo), in human settlements along the Aruwimi and Lomami rivers (Province Orientale, DRCongo), along the Sangha river (Sangha department, Republic of the Congo) and in Pallisco logging concessions (East Province of Cameroon). First charcoal identification results are promising and sometimes seem to be taxonomically more precise than pollen identification. However, next to opportunities, we also present some pitfalls when exploring ancient charcoal archives. [less ▲]

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