Policies to reduce emissions from deforestation and forest degradation largely depend on accurate estimates of tropical forest carbon stocks. Here we present the first field-based carbon stock data ...for the Central Congo Basin in Yangambi, Democratic Republic of Congo. We find an average aboveground carbon stock of 162 ± 20 Mg C ha(-1) for intact old-growth forest, which is significantly lower than stocks recorded in the outer regions of the Congo Basin. The best available tree height-diameter relationships derived for Central Africa do not render accurate canopy height estimates for our study area. Aboveground carbon stocks would be overestimated by 24% if these inaccurate relationships were used. The studied forests have a lower stature compared with forests in the outer regions of the basin, which confirms remotely sensed patterns. Additionally, we find an average soil carbon stock of 111 ± 24 Mg C ha(-1), slightly influenced by the current land-use change.
There is an increasing need for monitoring schemes that help understand the evolution of the global biodiversity crisis and propose solutions for the future. Indicators, including temporal baselines, ...are crucial to measure the change in biodiversity over time, to evaluate progress towards its conservation and sustainable use and to set conservation priorities. They help design and monitor national and regional policies on biodiversity; they also feed into national reporting on international agreements such as the Convention on Biological Diversity and the Sustainable Development Goals. We analyse the methodological approach of five small African projects resulting from a call to promote indicator development, improve monitoring capacity and strengthen the science-policy interface in the field of biodiversity. We compared their approach to existing guidance provided by the international community, specifically the Biodiversity Indicators Partnership. To this end, we assess whether internationally recommended steps are effectively applied to national/local biodiversity monitoring in selected developing countries. We also present lessons learnt from workshop interactions between partners involved in these projects. Through our pilot projects we identified data availability and data accessibility, together with the involvement of stakeholders, as critical steps in indicator development. Moreover, there is a need for a better awareness and a wider application of the indicator concept itself. Hence, training of key actors both in the policy and science spheres is needed to operationalize indicators and ensure their continuity and sustainability. We hope that these case studies and lessons learnt can stimulate and support countries in the Global South to formulate policy-relevant biodiversity indicators.
Plant functional traits have shown to be relevant predictors of forest functional responses to climate change. However, the trait-based approach to study plant performances and ecological strategies ...has mostly been focused on trait comparisons at the interspecific and intraspecific levels. In this study, we analyzed traits variation and association at the individual level. We measured wood and leaf traits at different height locations within the crown of five individuals of Pericopsis elata (Harms) Meeuwen (Fabaceae) from the northern tropical forest of the Democratic Republic of the Congo. All traits varied between and within individuals. The between-individual variation was more important for leaf traits (23%–48%) than for wood traits (~10%) where the within-individual variation showed to be more important (33%–39%). The sample location height within the crown was found to be the driving factor of this within-individual variation. In a gradient from the base to the top of the crown, theoretical specific hydraulic conductivity and specific leaf area decreased while the stomatal density increased. We found significant relationships among traits and between wood and leaf traits. However, these relationships varied with the position within the crown. The relationship between vessel size and vessel density was negative at the bottom part of the crown but positive upward. Also, the negative relationship between stomatal density and stomatal size became stronger with increasing height within the crown. Finally, the positive relationship between specific leaf area and theoretical specific hydraulic conductivity became stronger in higher parts of the crown, suggesting that P. elata constantly adapts its water use with respect to its water supply, more strongly at the top of the crown where the environment is more extreme and less buffered against environmental fluctuations.
The long-lived pioneer species Pericopsis elata is one of the rare tropical timbers on the list of the Convention on International Trade of Endangered Species, supporting the need for accurate and ...reliable growth data. In one planted and one natural forest in the Democratic Republic of Congo, respectively four and 37 Pericopsis stem disks were collected. The tree-ring series of planted trees were used to confirm annual tree-ring formation. For the natural forest, a tree-ring chronology with 24 stem disks ranged from 1852 up to 2008. This chronology was compared with time-series of local precipitation, resulting in a significant correlation with the second half of the rainy season (September-November). This seasonal precipitation was related with sea surface temperatures of the West Indian Ocean. Higher precipitation during El Niño years corresponded with higher tree-ring indices but differences were not significant. In addition, pointer years were rare and did not have a consistent link with extreme climatic conditions. The existence of annual tree rings encourages further tree-ring analyses of P. elata and other flagship timber species in order to further document climate-growth responses and to provide the long-term framework that is needed for sustainable management planning.
In equatorial regions, where tree rings are less distinct or even absent, the response of forests to high-frequency climate variability is poorly understood. We measured stable carbon and oxygen ...isotopes in anatomically distinct, annual growth rings of four Pericopsis elata trees from a plantation in the Congo Basin, to assess their sensitivity to recorded changes in precipitation over the last 50 y. Our results suggest that oxygen isotopes have high common signal strength (EPS = 0.74), and respond to multi-annual precipitation variability at the regional scale, with low δ18O values (28–29‰) during wetter conditions (1960–1970). Conversely, δ13C are mostly related to growth variation, which in a light-demanding species are driven by competition for light. Differences in δ13C values between fast- and slow-growing trees (c. 2‰), result in low common signal strength (EPS = 0.37) and are driven by micro-site conditions rather than by climate. This study highlights the potential for understanding the causes of growth variation in P. elata as well as past hydroclimatic changes, in a climatically complex region characterized by a bimodal distribution in precipitation.
Industrial logging has been the subject of strong debate, epitomised by the contentious positions around logging in the Congo Basin. Logging companies are often considered as homogeneous and rather ...static agents, which leads to sweeping generalisations about their performance and the subsequent technical and policy recommendations. This study covers 31 logging concessions in the five ITTO member countries of the Congo Basin. Based on a detailed questionnaire complemented by published statistics, the concessions are characterised by the country in which they operate, their legal status, age, size, origin of capital, and market focus. Concessions show patterns shaped by interactions between these factors, with different logging strategies associated with the resulting groupings. Our results lend partial support to some of the common generalisations about the performance of logging companies of different scales and geographic origin. For example, national concessions tend to have higher processing rates and often create more employment. However, the data also suggest nuances that can contradict some of the conventional views. Thus, some large concessions may well use better management tools than smaller ones while some national concessions may exert a higher pressure on their allocated forests. Some key parameters related to concessions’ performance (like species logged, productivity per hectare, percent of the concession logged per year and employment) work together in the specific environmental, economic and policy contexts of each country to produce a complex regional image that is sometimes oversimplified when submitted to anecdotal or special interest advocacy analyses.
Above-ground biomass and structure of 260 African tropical forests Lewis, Simon L.; Sonké, Bonaventure; Sunderland, Terry ...
Philosophical transactions of the Royal Society of London. Series B. Biological sciences,
09/2013, Letnik:
368, Številka:
1625
Journal Article
Recenzirano
We report above-ground biomass (AGB), basal area, stem density and wood mass density estimates from 260 sample plots (mean size: 1.2 ha) in intact closed-canopy tropical forests across 12 African ...countries. Mean AGB is 395.7 Mg dry mass ha⁻¹ (95% CI: 14.3), substantially higher than Amazonian values, with the Congo Basin and contiguous forest region attaining AGB values (429 Mg ha⁻¹) similar to those of Bornean forests, and significantly greater than East or West African forests. AGB therefore appears generally higher in palaeo-compared with neotropical forests. However, mean stem density is low (426 ± 11 stems ha⁻¹ greater than or equal to 100 mm diameter) compared with both Amazonian and Bornean forests (cf. approx. 600) and is the signature structural feature of African tropical forests. While spatial autocorrelation complicates analyses, AGB shows a positive relationship with rainfall in the driest nine months of the year, and an opposite association with the wettest three months of the year; a negative relationship with temperature; positive relationship with clay-rich soils; and negative relationships with C : N ratio (suggesting a positive soil phosphorus-AGB relationship), and soil fertility computed as the sum of base cations. The results indicate that AGB is mediated by both climate and soils, and suggest that the AGB of African closed-canopy tropical forests may be particularly sensitive to future precipitation and temperature changes.
The external factors that influence the environmental, social and economic performance of logging companies were studied using a questionnaire submitted to 30 logging concessions in five countries of ...the Congo Basin. This paper analyses socioeconomic constraints and environmental impacts experienced by these concessions, as well as their response to major external drivers of change. Concessionaires considered investment and operating finance their main constraint, followed by insufficient technical and human capacities, and inconsistent application of official regulations. Environmental problems directly produced by concessions' operations represented around one-third of the total score for environmental problems reported. Damage caused by construction of logging roads and erosion were identified as the main issues. Induced problems (two-thirds of the total score) were dominated by hunting, with encroachment and illegal logging perceived as much less significant. Policies, infrastructure, markets and technology are key external drivers of change in concessions' practices, while regional and international forestry institutions reportedly have the least influence, reflecting an emerging scepticism about the proliferation of international institutions and initiatives promoting sustainable forestry.
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