Mission dans la plantation de cocotiers de RSUP à Pulau Burung/Sumatra/Indonésie, 3 novembre au 14 décembre 1997. Recherches sur les facteurs limitant le rendement du cocotier hybride PB121

Cette mission conjointe d'un entomologiste et d'un physiopathologiste spécialisé dans l'étude des systèmes racinaires a permis d'affirmer que les attaques de chenilles de #Sufetula# sont bien responsables, en partie, de la faible production des cocotiers de RSUP à Pulau Burung. Cependant ces chenilles ne sont très probablement pas à l'origine de la très grande hétérogénéité qui affecte la croissance des cocotiers. Celle-ci est principalement induite par d'autres facteurs, comme par exemple le niveau de la nappe d'eau. Il a été possible de montrer qu'il existe une bonne relation triangulaire entre la hauteur des cocotiers, le poids frais de leurs racines et le nombre de noix présentes sur les cocotier

bibliography on cashew 1995-2007

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The impact of herbivores on the natural regeneration of temperate deciduous woodland

Many studies have reported deficient or intermittent patterns of natural regeneration in temperate deciduous woodland. The present study aimed to assess the relative impact of herbivore-mediated plant mortality on the natural regeneration dynamics of representative tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior, Ilex aquifolium, Sorbus aucuparia, Taxus baccata and Ulmus glabra) in representative temperate deciduous woodland (Shipley Wood and Derwent Gorge, County Durham). Sapling density and the density, spatial association and size distribution of adult tree populations varied significantly between tree species and study sites, reflecting contrasting patterns of current and historical regeneration. Rates of post-dispersal seed predation and seedling herbivory were quantified using field-based 'cafeteria' trials. Rodents were the principal agents responsible for seed predation, whereas seedling herbivory was attributable to a mixed suite of herbivores including invertebrates, rodents and larger mammals. Rates of seed predation and seedling herbivory varied significantly between tree species, most likely reflecting individualistic, trade-off responses to chemical and physical attributes. Fine-scale spatial variation most likely reflected the preferential foraging of rodents beneath protective vegetation cover. There was no consistent evidence to support the hypothesis that dispersed seeds may escape disproportionately high offspring mortality beneath parent plants resulting from increased herbivore activity. Natural seedling density varied significantly between years and between tree species, according to the abundance of viable seeds produced by conspecific adult trees. Although seedling survivorship varied significantly between species, the survivorship of each species was similar between years and between cohorts of the same year. Canopy cover, field layer cover or correlated factors were significant determinants of seed germination and seedling emergence, establishment and survival, according to age- and species-specific tolerances. In relative terms, patterns of natural regeneration were primarily herbivore- limited (Acer and Taxus), microsite-limited (Betula, Fraxinus, Ilex and Ulmus) or limited by herbivores and microsites (Sorbus). The availability of viable seeds may have also limited the recruitment of Ilex, Sorbus, Taxus and Ulmus. Vegetative expansion, mast seeding, seed bank regeneration and repeated, prolonged reproduction may have reduced the actual impact of herbivory on natural regeneration, such that long-lived iteroparous tree species were unlikely to have been critically dependent on current recruitment

GROWTH DYNAMICS OF BLACK SPRUCE (PICEA MARIANA) ACROSS NORTHWESTERN NORTH AMERICA

The impacts of climate change have been widely documented around the world. One of the most rapidly changing areas is the boreal forest of North America. The extent of change has been such that there have been shifts in long-standing climate-growth relationships in many boreal tree species; while the growth of many of these high-latitude forests were formerly limited by temperature, warming has increased the evapotranspirative demands such that there is widespread drought stress limiting productivity in the boreal forest. With the importance of the boreal forest as a global carbon sink, it is imperative to understand the extent of these changes, and to predict the resilience of the boreal forest in the face of continued climate change. One area of the boreal forest that has not been extensively studied, despite some of the most extreme warming, is northwestern Canada. Black spruce, the most widespread and dominant of North American boreal trees, is particularly under-studied in this region. In my doctoral research, I have sought to fill some of these knowledge gaps regarding black spruce growth dynamics across its latitudinal extent in northwestern Canada through addressing three main objectives: (1) Investigate the effects of permafrost thaw on the growth dynamics of black spruce in a discontinuous permafrost peatland; (2) Compare the productivity and main climatic drivers of black spruce growth across the latitudinal extent of the species in northwestern Canada; (3) Quantify the degree of plasticity vs. local adaptation in determining black spruce growth responses to resource availability in a common garden study. The results of this research highlight the variability in black spruce growth dynamics across this broad climate and permafrost gradient. While productivity has increased at the northern and southern margins of the boreal forest, the mid-latitude site in the discontinuous permafrost peatland has demonstrated dramatic declines in productivity. I demonstrate that this can be attributed to the negative impacts of permafrost thaw-induced drought stress, wherein the thickening of the active layer is reducing the capacity of shallow-rooted black spruce to access the water table. Thus, decreased growth at this site is an indirect effect of warming. At the northern margins of black spruce, growth is increasing as a result of warming, likely as it can drive longer growing seasons and increased nutrient mineralization. Growth at the southern margin does not appear to be driven by either temperature or precipitation alone, however growth patterns appear to be influenced by water balance at the site as well as CO2 fertilization. The common garden study of seedlings from across the latitudinal extent of black spruce in northwestern Canada provided evidence for local adaptation in black spruce seedlings; the southern seedlings accumulated biomass rapidly at the cost of risking damage to new growth from the onset of harsh temperatures, while northern seedlings grew slowly and conservatively, reducing the risk of damage at the cost of lower growth rates than their southern counterparts. We did not see any significant effect of increased CO2 concentrations on any of the seedling traits studied, however seedlings in the high nutrient treatment showed more pronounced signs of a competitive, fast-growth strategy, which ultimately led to extensive mortality of this treatment. Given this knowledge about black spruce growth dynamics in natural forests and under controlled environment conditions, I can conclude that while the mid-latitude population on a discontinuous permafrost peatland is likely to face substantial declines in productivity and forest cover loss, the northern and southern populations have the potential to remain highly productive provided evapotranspirative demands are met by precipitation, and that no major disturbances influence competitive interactions with this species

Forests, carbon cycle and climate change

The results presented in this book summarize the main findings of the CARBOFOR project, which brought together 52 scientists from 14 research units to investigate the effects of future climate on the carbon cycle, the productivity and vulnerability of French forests. This book explains the current forest carbon cycle in temperate and Mediterranean climates, including the dynamics of soil carbon and the total carbon stock of French forests, based on forest inventories. It reviews and illustrates the main ground-based methods for estimating carbon stocks in tree biomass. Spatial variations in projected climate change over metropolitan France throughout the 21st century are described. The book then goes on to consider the impacts of climate change on tree phenology and forest carbon balance, evapotranspiration and production as well as their first order interaction with forest management alternatives. The impact of climate change on forest vulnerability is analysed. A similar simulation study was carried out for a range of pathogenic fungi, emphasizing the importance of both warming and precipitation changes. The consequences of climate change on the occurrence of forest fires and the forest carbon cycle in the Mediterranean zone are also considered.A valuable reference for researchers and academics, forest engineers and managers, and graduate level students in forest ecology, ecological modelling and forestry

Insights about saproxylic biodiversity living in old-growth forests of French Pyrénées

The symposium will span over four days, including a one day field trip. Keynote addresses will introduce morning sessions followed by parallel conference sessions. Scientific poster sessions, held in the late afternoon, will be combined with a cocktail buffet. A banquet will take place on Wednesday night. All events will be held at the Rouyn-Noranda Congress Center