Tag: tropical forests


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  • Altitudinal filtering of large-tree species explains above-ground biomass variation in an Atlantic Central African rain forest

Altitudinal filtering of large-tree species explains above-ground biomass variation in an Atlantic Central African rain forest

31 January, 2017

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Authors: Gonmadje, C.; Picard, N.; Gourlet-Fleury, S.; Réjou-Méchain, M.; Freycon, V.; Sunderland, T.C.H.; McKey, D.; Doumenge, C.

Patterns in above-ground biomass of tropical forests over short altitudinal gradients are poorly known. The aim of this study was to investigate the variation of above-ground biomass with altitude in old-growth forests and determine the importance of changes in floristic composition as a cause of this variation. We used a dataset from 15 1-ha permanent plots established from lowland (200 m asl) to submontane forests (900 m asl) in the Ngovayang Massif, south-western Cameroon. We analysed variation over altitude in two specific functional traits, the potential maximum tree height and the wood density. Forest above-ground biomass decreased from 500-600 Mg ha-1 in lowland plots to around 260 Mg ha-1 at the highest altitudes. The contribution to above-ground biomass of large-tree species (dbh = 70 cm) decreased with altitude, while the contribution of smaller trees was constant. Contribution of the Fabaceae subfamily Caesalpinioideae decreased with altitude, while those of Clusiaceae, Phyllanthaceae and Burseraceae increased. While potential maximum tree height significantly decreased, wood specific gravity displayed no trend along the gradient. Finally, the decrease in above-ground biomass along the short altitudinal gradient can be at least partially explained by a shift in species composition, with large-tree species being filtered out at the highest altitudes. These results suggest that global change could lead to significant shifts in the properties of montane forests over time.

Pages: 12p

Publication Year: 2017

ISSN: 0266-4674

Source: Journal of Tropical Ecology

DOI: https://doi.org/10.1017/S0266467416000602

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  • Natural regeneration as a tool for large-scale forest restoration in the tropics: prospects and challenges

Natural regeneration as a tool for large-scale forest restoration in the tropics: prospects and challenges

24 November, 2016

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Authors: Chazdon, R.L.; Guariguata, M.R.

A major global effort to enable cost-effective natural regeneration is needed to achieve ambitious forest and landscape restoration goals. Natural forest regeneration can potentially play a major role in large-scale landscape restoration in tropical regions. Here, we focus on the conditions that favor natural regeneration within tropical forest landscapes. We illustrate cases where large-scale natural regeneration followed forest clearing and non-forest land use, and describe the social and ecological factors that drove these local forest transitions. The self-organizing processes that create naturally regenerating forests and natural regeneration in planted forests promote local genetic adaptation, foster native species with known traditional uses, create spatial and temporal heterogeneity, and sustain local biodiversity and biotic interactions. These features confer greater ecosystem resilience in the face of future shocks and disturbances. We discuss economic, social, and legal issues that challenge natural regeneration in tropical landscapes. We conclude by suggesting ways to enable natural regeneration to become an effective tool for implementing large-scale forest and landscape restoration. Major research and policy priorities include: identifying and modeling the ecological and economic conditions where natural regeneration is a viable and favorable land-use option, developing monitoring protocols for natural regeneration that can be carried out by local communities, and developing enabling incentives, governance structures, and regulatory conditions that promote the stewardship of naturally regenerating forests. Aligning restoration goals and practices with natural regeneration can achieve the best possible outcome for achieving multiple social and environmental benefits at minimal cost.

Publication Year: 2016

ISSN: 1744-7429

Source: Biotropica 48(6): 716-730

DOI: 10.1111/btp.12381

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  • Assessing the effectiveness of subnational REDD+ initiatives by tree cover change analysis

Assessing the effectiveness of subnational REDD+ initiatives by tree cover change analysis

04 August, 2016

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This presentation was given by Astrid Bos Valerio Avitabile, Martin Herold, Amy Duchelle, Shijo Joseph, Claudio de Sassi, William Sunderlin, Erin Sills, Arild Angelsen, Sven Wunder at the Annual Meeting of the Association for Tropical Biology and Conservation in Monpellier 2016.

Given the key role of forests in mitigating climate change, it becomes increasingly important to monitor the carbon effectiveness of policies and programmes for reducing emissions from deforestation and forest degradation (REDD+). Performance assessment is essential to check progress, verify accountability, and learn from REDD+ implementation in general, with important bearings on funding for REDD+ in the long term. This study presents a new framework to assess the effectiveness of subnational REDD+ initiatives from 2000 to 2014 using tree cover change trajectories with and without REDD+ since its implementation.

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  • Agrarian change in tropical forests: A change for the better?

Agrarian change in tropical forests: A change for the better?

05 July, 2016

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This presentation was given by Terry Sunderland at the 53rd Annual Meeting of the Association for Tropical Biology and Conversation.

Agricultural expansion has resulted in losses to habitats, forests, ecosystems and biological diversity. Socio-ecological research methods were used to assess the livelihood impacts of agrarian change across the forest transition in six tropical landscapes in Zambia, Burkina Faso, Cameroon, Ethiopia, Indonesia and Bangladesh. Early findings suggest the transition from a forested landscape to a more agrarian-dominated system does not immediately result in better livelihood outcomes, and there may be unintended consequences.

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  • Mammalian biogeography and the Ebola virus in Africa

Mammalian biogeography and the Ebola virus in Africa

13 June, 2016

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Authors: Olivero, J.; Fa, J.E.; Real, R.; Farfán, M.A.; Márquez, A.L.; Vargas, J.M.; Paul Gonzales, J.; Cunningham, A.A.; Nasi, R.

  1. Ebola virus is responsible for the fatal Ebola virus disease (EVD).
  2. Identifying the distribution area of the Ebola virus is crucial for understanding the risk factors conditioning the emergence of new EVD cases. Existing distribution models have underrepresented the potential contribution that reservoir species and vulnerable species make in sustaining the presence of the virus.
  3. In this paper, we map favourable areas for Ebola virus in Africa according to environmental and zoogeographical descriptors, independent of human-to-human transmissions. We combine two different biogeographical approaches: analysis of mammalian distribution types (chorotypes), and distribution modelling of the Ebola virus.
  4. We first obtain a model defining the distribution of environmentally favourable areas for the presence of Ebola virus. Based on a review of mammal taxa affected by or suspected of exposure to the Ebola virus, we model favourable areas again, this time according to mammalian chorotypes. We then build a combined model in which both the environment and mammalian distributions explain the favourable areas for Ebola virus in the wild.
  5. We demonstrate that mammalian biogeography contributes to explaining the distribution of Ebola virus in Africa, although vegetation may also underscore clear limits to the presence of the virus. Our model suggests that the Ebola virus may be even more widespread than previously suspected, given that additional favourable areas are found throughout the coastal areas of West and Central Africa, stretching from Cameroon to Guinea, and extend further East into the East African Lakes region.
  6. Our findings show that the most favourable area for the Ebola virus is significantly associated with the presence of the virus in non-human mammals. Core areas are surrounded by regions of intermediate favourability, in which human infections of unknown source were found. The difference in association between humans and other mammals and the virus may offer further insights on how EVD can spread.
Published at Mammal Review 6 June 2016
Also at: Center for International Forestry Research (CIFOR)

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  • Managing and restoring natural tropical forests: discussion forum at GLF 2015

Managing and restoring natural tropical forests: discussion forum at GLF 2015

23 March, 2016

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Originally published at Global Landscapes Forum 2015

CIRAD’s Plinio Sist is an advocate of “tropical managed forests“. The Director of CIRAD’s Research unit BSEF made the case for the concept of tropical managed forests for example at the 2015 Global Landscapes Forum, with the discussion forum Managing and restoring natural tropical forests: Ensuring a sustainable flow of benefits for people in the context of global change. 

The obvious reasons to study tropical forests come from the sheer facts: they make up half of the earth’s forests, are home to half of the species on land, and they gather nearly a third of the terrestrial carbon stocks. At the same time, deforestation is concentrated in the tropics. The FAO estimated forest loss from 2010 to 2015 at close to nine million hectares (i.e. 90,000 km2) per year. That is nearly the size of Portugal or Hungary in forest cover lost every year.

Plinio Sist countered the view that deforestation equals logging and argued for Reduced Impact Logging (RIL) which disturbs the forest, but doesn’t destroy it. The main actors whose interests have to be balanced are forest companies, smallholder farmers and forest communities.

The discussion forum revolved around the challenges of

  • forest degradation, management and restoration (also in the context of landscape management)
  • tropical forests versus plantations
  • food production versus environmental services

Presentations focused on

  • FSC certification in the Brazilian Amazon,
  • concessions 2.0 in Central Africa, which suggests land-sharing through a hybrid of a company and a territorial institution
  • managing tropical forests in an era of change in South East Asia, in which FTA Director Robert Nasi and his co-presenter Michael Galante make the case for new approaches to managing logged-over forests and benefits
  • forest restoration as key component to tackle climate change, which argues that the underlying factors of deforestation have to do with governance

Also see the presentation here

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  • Why managing and restoring tropical forests matters

Why managing and restoring tropical forests matters


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CIRAD’s Plinio Sist is an advocate of “tropical managed forests“. The Director of CIRAD’s Research unit BSEF made the case for tropical managed forests for example at the 2016 Global Landscapes Forum, with the discussion forum Managing and restoring natural tropical forests: Ensuring a sustainable flow of benefits for people in the context of global change. 

The obvious reasons to study tropical forests come from the sheer facts: they make up half of the earth’s forests, are home to half of the species on land, and they gather nearly a third of the terrestrial carbon stocks. At the same time, deforestation is concentrated in the tropics. The FAO estimated forest loss from 2010 to 2015 at close to nine million hectares (i.e. 90,000 km2) per year. That is nearly the size of Portugal or Hungary in forest cover lost every year.

Plinio Sist countered the view that deforestation equals logging and argued for Reduced Impact Logging (RIL) which disturbs the forest, but doesn’t destroy it. The main actors whose interests have to be balanced are forest companies, smallholder farmers and forest communities.

The discussion forum revolved around the challenges of

  • forest degradation, management and restoration (also in the context of landscape management)
  • tropical forests versus plantations
  • food production versus environmental services

Presentations focused on

  • FSC certification in the Brazilian Amazon (slide 7-12),
  • concessions 2.0 in Central Africa, which suggests land-sharing through a hybrid of a company and a territorial institution (slide 13-25)
  • managing tropical forests in an era of change in South East Asia, in which FTA Director Robert Nasi and his co-presenter make the case for new approaches to managing logged-over forests and benefits (slide 26-34)
  • forest restoration as key component to tackle climate change, which argues that the underlying factors of deforestation have to do with governance (slides 35-47)

The presentation was originally published at Global Landscapes Forum 2015

Please contact us at cgiarforestsandtrees@cgiar.org if you need individual versions for each of the presentations.

 

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  • Relationships between population density, fine-scale genetic structure, mating system and pollen dispersal in a timber tree from African rainforest

Relationships between population density, fine-scale genetic structure, mating system and pollen dispersal in a timber tree from African rainforest

15 March, 2016

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Also published at Bioversity International

Authors: Duminil, J.; Dainou, K.; Kaviriri, D.K.; Gillet, P.; Loo, J.; Doucet, J.L.; Hardy, O.J.

The reproductive biology and genetic diversity of trees in the Congo Basin don’t seem to be affected by current logging practices. However, researcher recommend further investigations in low-density populations to evaluate (1) whether pollen limitation may reduce seed production and (2) the regeneration potential of the species.

This is the result from a study of genetic diversity, mating system and gene flow in three Central African populations of the self-compatible legume timber species Erythrophleum suaveolens with contrasting densities (0.11, 0.68 and 1.72 adults per ha).

Comparing reproductive biology processes and genetic diversity of populations at different densities can provide indirect evidence of the potential impacts of logging.

Selective logging could affect the demography, reproductive biology and evolutionary potential of forest trees. This is particularly relevant in tropical forests where natural population densities can be low and isolated trees may be subject to outcross pollen limitation and/or produce low-quality selfed seeds that exhibit inbreeding depression.

Researchers found that inbred individuals are eliminated between seedling and adult stages. Levels of genetic diversity, selfing rates (~16%) and patterns of spatial genetic structure (Sp ~0.006) were similar in all three populations.

However, the extent of gene dispersal differed markedly among populations: the average distance of pollen dispersal increased with decreasing density (from 200 m in the high-density population to 1000 m in the low-density one). In other words, at lower population densities, trees are still connected as a result of larger pollen dispersal distances.

The study was conducted by Bioversity International, the Université Libre de Bruxelles, Brussels, Belgium; Université de Liège, Gembloux, Belgium; Nature+ asbl, Wavre, Belgium; Université de Kisangani, Kisangani, Democratic Republic of Congo.

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