Spatial pattern of trees influences species productivity in a mature oak-pine mixed forest

Spatial pattern has a key role in the interactions between species in plant communities. These interactions influence ecological processes involved in the species dynamics: growth, regeneration and mortality. In this study, we investigated the effect of spatial pattern on productivity in mature mixed forests of sessile oak and Scots pine. We simulated tree locations with point process models and tree growth with spatially explicit individual growth models. The point process models and growth models were fitted with field data from the same stands. We compared species productivity obtained in two types of mixture: a patchy mixture and an intimate mixture. Our results show that the productivity of both species is higher in an intimate mixture than in a patchy mixture. Productivity difference between the two types of mixture was 11.3% for pine and 14.7% for oak. Both species were favored in the intimate mixture because, for both, intraspecific competition was more severe than interspecific competition. Our results clearly support favoring intimate mixtures in mature oak-pine stands to optimize tree species productivity; oak is the species that benefits the most from this type of management. Our work also shows that models and simulations can provide interesting results for complex forests with mixtures, results that would be difficult to obtain through experimentation

Potencial de conservación de la biodiversidad de bosques y árboles en fincas del paisaje ganadero Catacamas, Honduras

El estudio evaluó el potencial de conservación de biodiversidad arbórea de diferentes usos de la tierra en el paisaje ganadero Catacamas, Honduras. Se planteó la hipótesis de que los diferentes usos contribuyen en la misma medida a la conservación de la diversidad de árboles a escala de parcela y paisaje. Se muestrearon árboles con un dap mínimo de medición de 10 cm en 448 parcelas (área total de 84,2 ha) ubicadas en diferentes usos forestales y agrícolas característicos del paisaje Catacamas: bosques secundarios continuos (BS), fragmentos de bosque secundario (BSF), plantaciones de café rústico (PLANT), agricultura (AGRI), pasturas (PAST), cercas vivas (CV) y bosques ribereños (BR). Con los datos se caracterizó la estructura, composición y diversidad arbórea en el paisaje y se comparó entre los usos de la tierra

Agroforesterie et services écosystémiques en zone tropicale

Respectueux de l’environnement et garantissant une sécurité alimentaire soutenue par la diversification des productions et des revenus qu’ils procurent, les systèmes agroforestiers apparaissent comme un modèle prometteur d’agriculture durable dans les pays du Sud les plus vulnérables aux changements globaux. Cependant, ces systèmes agroforestiers ne peuvent être optimisés qu’à condition de mieux comprendre et de mieux maîtriser les facteurs de leurs productions. L’ouvrage présente un ensemble de connaissances récentes sur les mécanismes biophysiques et socio-économiques qui sous-tendent le fonctionnement et la dynamique des systèmes agroforestiers. Il concerne, d’une part les systèmes agroforestiers à base de cultures pérennes, telles que cacaoyers et caféiers, de régions tropicales humides en Amérique du Sud, en Afrique de l’Est et du Centre, d’autre part les parcs arborés et arbustifs à base de cultures vivrières, principalement de céréales, de la région semi-aride subsaharienne d’Afrique de l’Ouest. Il synthétise les dernières avancées acquises grâce à plusieurs projets associant le Cirad, l’IRD et leurs partenaires du Sud qui ont été conduits entre 2012 et 2016 dans ces régions. L’ensemble de ces projets s’articulent autour des dynamiques des systèmes agroforestiers et des compromis entre les services de production et les autres services socio-écosystémiques que ces systèmes fournissent

Active restoration of secondary and degraded forests in the context of the UN Decade on Ecosystem Restoration

2021–2030 was declared in 2019 as the decade on ecosystems restoration by the United Nations General Assembly (www.decadeonrestoration.org). The declaration warns that ecosystem degradation already affects the well-being of almost the half of the world’s population. The declaration therefore emphasizes the urgent need of preventing, halting, reversing ecosystem degradation, and intensifying restoration of degraded and destroyed ecosystems worldwide. Besides its relevance for global issues like global warming and biodiversity loss, restoration of degraded ecosystems is essential to the achievement of the Sustainable Development Goals. The UN decade of ecosystems restoration declaration therefore recalls the resolutions of the United Nations Assembly for environment concerning conservation and restoration of vulnerable terrestrial ecosystems

Spatiotemporal patterns of Phytophthora megakarya infections in newly established cacao plantations in Cameroon

BGPI : équipe 5Studying spatial and temporal plant disease dynamics helps to understand pathogen dispersal processes, a necessary undertaking in epidemiology in order to improve disease control recommendations. In this study, plantations devoid of primary inoculum of Phytophthora megakarya (causal agent of cacao black pod disease), upon establishment in 2006, were monitored for presence of disease on a weekly basis from 2009 to 2016. Isolates of P. megakarya collected in these plantations were genotyped with 14 SSR markers. Ripley’s K functions were used to characterize spatial disease dynamics. The univariate K-function was used to describe spatial disease patterns and the bivariate K12-function was used to describe the relation between healthy and diseased cacao trees. Disease distribution maps show aggregated disease patterns in all plots. The K-function confirmed these results although it was not significant in all patterns, probably due to a limited number of diseased cocoa trees. Healthy and diseased cacao trees were mostly negatively correlated, indicating that cacao black pod disease dispersal is a clustered process preferentially affecting neighbors of already infected trees. Based on observations it appears that occurrence of black pod disease is not a complete randomized process. The neighboring environment can greatly influence disease dispersal processes. For instance, closeness to already infected cacao plantations can favor dispersal of disease propagules while the presence of a river can increase the disease incidence and pathogen diversity. According, to the results, black pod disease is mainly spread over relatively short distances. Isolation of newly established cacao plantations from infected ones appears therefore to be an effective approach to control of black pod

Spatiotemporal patterns of Phytophthora megakarya infections in newly established cacao plantations in Cameroon

BGPI : équipe 5Studying spatial and temporal plant disease dynamics helps to understand pathogen dispersal processes, a necessary undertaking in epidemiology in order to improve disease control recommendations. In this study, plantations devoid of primary inoculum of Phytophthora megakarya (causal agent of cacao black pod disease), upon establishment in 2006, were monitored for presence of disease on a weekly basis from 2009 to 2016. Isolates of P. megakarya collected in these plantations were genotyped with 14 SSR markers. Ripley’s K functions were used to characterize spatial disease dynamics. The univariate K-function was used to describe spatial disease patterns and the bivariate K12-function was used to describe the relation between healthy and diseased cacao trees. Disease distribution maps show aggregated disease patterns in all plots. The K-function confirmed these results although it was not significant in all patterns, probably due to a limited number of diseased cocoa trees. Healthy and diseased cacao trees were mostly negatively correlated, indicating that cacao black pod disease dispersal is a clustered process preferentially affecting neighbors of already infected trees. Based on observations it appears that occurrence of black pod disease is not a complete randomized process. The neighboring environment can greatly influence disease dispersal processes. For instance, closeness to already infected cacao plantations can favor dispersal of disease propagules while the presence of a river can increase the disease incidence and pathogen diversity. According, to the results, black pod disease is mainly spread over relatively short distances. Isolation of newly established cacao plantations from infected ones appears therefore to be an effective approach to control of black pod

Biomass of timber species in Central American secondary forests: Towards climate change mitigation through sustainable timber harvesting

Sustainable management of secondary forests for timber production offers the opportunity to combine nature-based climate change mitigation with direct improvement of human livelihoods in the tropics, but this dual potential has rarely been explored. We characterized aboveground biomass (AGB) in secondary forests (SF) in Nicaragua and Costa Rica in whole stands (ecological potential), individual trees of timber species (total timber potential), and currently harvestable timber (harvestable timber potential). We also linked the three types of AGB potential to climate and soil factors. Data on 302 sample plots were collected, most from national forest inventories (NFIs) concerning 168 plots in Nicaragua and 134 plots in Costa Rica

Relevance of secondary tropical forest for landscape restoration

Tropical Secondary Forests (SFs) are vulnerable forest systems growing in areas that have been subject to unsustainable human activities leading to deforestation. SFs account for swathes of tropical forest landscapes that have lost their capacity to provide a high level of goods and services. They are also located in highly dynamic and human-pressured landscapes and are vulnerable to natural and human-induced catastrophic events, such as hurricanes or fires. Without appropriate silvicultural management to increase their economic value and restore their ecological functions, they often become degraded and are sometimes cleared for more short-term economically productive activities. Given the increasing demand for tropical timber in recent decades that will continue in the near future, we suggest that active restoration geared towards wood production is an opportunity for SF conservation. Promoting sustainable wood production -i.e. associated with other environmental services- in these disturbed forest ecosystems is also a way to reduce logging pressure on the remaining intact primary tropical forests, indeed, this may be the most important reason to enhance active restoration aimed at wood production in tropical SFs worldwide. Future research in forest ecology and management should produce experimental evidence of enhanced production of wood and ecosystem services in SFs through appropriate silvicultural experimentations