Impact of bark and foliage harvesting on fruit production of the multipurpose tree <Emphasis Type="Italic">Afzelia africana</Emphasis> in Burkina Faso (West Africa)

In sub-Saharan Africa, extraction for daily livelihood needs often results in uncontrolled exploitation of bark and leaves of valuable medicinal and fodder trees. However, overharvesting of bark and foliage can reduce fruit production and threaten reproduction. This study evaluates the impact of combined bark and foliage harvesting on the performance of fruit production of Afzelia africana in Burkina Faso. We compared fruit and seed production at different harvesting intensities. Data on fruit yields were collected by stratified random sampling of 91 trees with no, low, severe, and very severe harvesting intensities. The fruit production varied with harvesting intensity, tree size and number of branches. Fruit and seed quantity and quality decreased with increasing harvesting intensity. However, no significant difference was detected between trees without and trees under low harvesting. Trees of all size classes under very severe harvesting intensity had no fruits. Under low harvesting impact, large trees had twice as many fruits as the control, whereas fruits were reduced by half to 95 % for the small trees. High harvesting intensity is an unsustainable practice that should be completely prohibited in order to ensure longterm persistence of Afzelia africana. Low harvesting intensity should be allowed, but only on large reproductive individuals.     

Foaming and Emulsifying Properties of Fractions of Gluten Peptides Obtained by Limited Enzymatic Hydrolysis and Ultrafiltration

Gluten hydrolysates were prepared by limited enzymatic hydrolysis with a protease having a chymotryptic activity in the presence or in the absence of cysteine during the dispersion phase of the process. The hydrolysates were fractionated by ultrafiltration, using two inorganic membranes with different molecular weight cut-off (MWCO), 50 kg/mol and 150 kg/mol. The retentates were enriched in hydrophobic peptides and the permeates were enriched in hydrophilic peptides. The foaming and emulsifying properties of hydrolysates, retentates and permeates were analysed at two pHs (4 and 6·5) and two salt concentrations (0·2 and 2% NaCl). Hydrolysates displayed a foaming capacity, but the foams were not stable. Permeates generated foams at pH 6·5 only, and these foams had a very short life-time. Permeates displayed no emulsifying properties. Retentates yielded foams with a good stability and were more efficient than whole hydrolysates to stabilise emulsions. They provided a strong resistance to coalescence. The functional properties of retentates were only sightly influenced by pH and ionic strength. Neither cysteine addition, which helps gluten dispersion and increases the yield of soluble hydrolysate, nor the MWCO of the ultrafiltration membranes influenced the functionality of the hydrolysate fractions.     

Effects of brood size manipulation and common origin on phenotype and telomere length in nestling collared flycatchers

Background

Most species of brown macroalgae recruit exclusively sexually. However, Fucus radicans, a dominant species in the northern Baltic Sea, recruits new attached thalli both sexually and asexually. The level of asexual recruitment varies among populations from complete sexual recruitment to almost (> 90%) monoclonal populations. If phenotypic traits have substantial inherited variation, low levels of sexual activity will decrease population variation in these traits, which may affect function and resilience of the species. We assessed the level of inherited variation in nine phenotypic traits by comparing variation within and among three monoclonal groups and one group of unique multilocus genotypes (MLGs) sampled in the wild.

Results

Of the nine phenotypic traits, recovery after freezing, recovery after desiccation, and phlorotannin content showed substantial inherited variation, that is, phenotypic variation in these traits were to a large extend genetically determined. In contrast, variation in six other phenotypic traits (growth rate, palatability to isopod grazers, thallus width, distance between dichotomies, water content after desiccation and photochemical yield under ambient conditions) did not show significant signals of genetic variation at the power of analyses used in the study. Averaged over all nine traits, phenotypic variation within monoclonal groups was only 68% of the variation within the group of different MLGs showing that genotype diversity does affect the overall level of phenotypic variation in this species.

Conclusions

Our result indicates that, in general, phenotypic diversity in populations of Fucus radicans increases with increased multilocus genotype (MLG) diversity, but effects are specific for individual traits. In the light of Fucus radicans being a foundation species of the northern Baltic Sea, we propose that increased MLG diversity (leading to increased trait variation) will promote ecosystem function and resilience in areas where F. radicans is common, but this suggestion needs experimental support.     

PCB partitioning during sediment remobilization—a 1D column experiment

Purpose

Remobilization of polychlorobiphenyl (PCB)-contaminated sediments by anthropogenic activities (e.g. dredging) or natural flow conditions could lead to the release of PCBs into the water column and consequently increase the availability of PCBs to benthic organisms. The fate of the released PCBs following such events is not well understood and such knowledge is necessary for the management of contaminated sediments. The objective of this study was to understand the processes that control the fate of PCBs following remobilization of field-aged contaminated sediments.

Materials and methods

Sediments contaminated with PCBs collected from Lake Bourget (Savoie, France) were resuspended in a column experiment. The relationships between physical–chemical parameters—i.e. suspended particulate matter, pH, inorganic and organic carbon content, redox-sensitive species and the concentrations of dissolved PCBs both in the water column and in the interstitial water of the sediment—were investigated so as to determine the key processes controlling PCB fate.

Results and discussion

Following the simulated resuspension event (SRE), dissolved PCBs were found in much higher concentrations in the water column than under stationary conditions. Desorption of PCBs from the sediment depended on the degree of the hydrophobicity of the PCBs and the initial PCB content in the sediment. Principal component analysis showed that the variations in the concentrations of released PCBs over time and space closely followed those of suspended particulate matter (SPM) and not those of redox conditions. The partitioning behaviour of PCBs on SPM showed that equilibrium state was not attained within 40 days following the SRE. A particle size fractionation study, before and after remobilization of the sediment, showed the presence of PCBs in every fraction of the sediment, but with higher amounts in large particles with high organic matter content and in the finest fractions. Remobilization of contaminated sediment did not affect this distribution profoundly but a significant enrichment in PCBs of the clay-sized fraction was observed in the re-settled sediment.

Conclusions

Sediment resuspension induced non-equilibrium conditions in the water column for more than 5 weeks and led to the enrichment with PCBs of the newly formed surface bed sediment. This enrichment was due to the preferential re-sorption of PCBs on clay-sized particles during the SRE and to the physical segregation and accumulation of the less dense particles at the surface of the sediment column; such particles thought to be the principal carriers of contaminants. These changes concerned <0.05 % of the total PCB content.     

Utilisation de souches bacteriennes selectionees dans l'alimentation des larves de Mytilus galloprovincialis Lmk (Mollusque Bivalve) en elevages experimentauxUse of selected bacterial strains for feeding larvae of Mytilus galloprovincialis Lmk in experimental rearing

The authors studied the possibilities of using several bacterial strains, alive or heat-killed, alone or associated with an algal diet, as food for mussel larvae. Living bacteria offered with an algal culture improved larval growth, whereas the addition of heat-killed bacteria seemed to favour the appearance of an exogenous bacterial infection. Utilization of bacteria without algae sets the problems of their food value under these conditions and the concentration at which they should be used. Therefore, further complementary research will be necessary.     

Response to canopy opening does not act as a filter to Fagus sylvatica and Acer sp. advance regeneration in a mixed temperate forest

? In mixed-species forest stands, large losses in tree species diversity often occur during the regeneration phase. In a former coppice-with-standards, we investigated whether the limiting stage in the recruitment process of advance regeneration is the immediate seedling response to canopy release. Experimental canopy gaps were opened and the survival and growth of advance seedlings (Fagus sylvatica, Acer pseudoplatanus, Acer campestre, Acer platanoides) growing in the gaps or under closed canopy were monitored for three years.

? All species responded positively and rapidly to canopy release. Survival was not affected by gap opening. Diameter increment after gap opening was similar across species, and height increment was greater for Acer platanoides and for Acer pseudoplatanus. Post-release diameter and height growth were mainly determined by pre-release seedling size. Competition from neighbouring seedlings did not affect growth in the three years following canopy opening.

? In the recruitment process of F. sylvatica and Acer sp. advance regeneration, the recovery from canopy release did not appear as a limiting step that would filter against some species. Pre-release size was the main factor accounting for post-release growth and is probably a major determinant of long-term seedling dominance.

     

Effects of brood size manipulation and common origin on phenotype and telomere length in nestling collared flycatchers

ABSTRACT: BACKGROUND: Evidence is accumulating that telomere length is a good predictor of life expectancy, especially early in life, thus calling for determining the factors that affect telomere length at this stage. Here, we investigated the relative influence of early growth conditions and origin (genetics and early maternal effects) on telomere length of collared flycatchers (Ficedula albicollis) at fledging. We experimentally transferred hatchlings among brood triplets to create reduced, control (i.e. unchanged final nestling number) and enlarged broods. RESULTS: Although our treatment significantly affected body mass at fledging, we found no evidence that increased sibling competition affected nestling tarsus length and telomere length. However, mixed models showed that brood triplets explained a significant part of the variance in body mass (18%) and telomere length (19%), but not tarsus length (13%), emphasizing that unmanipulated early environmental factors influenced telomere length. These models also revealed low, but significant, heritability of telomere length (h2 = 0.09). For comparison, the heritability of nestling body mass and tarsus length was 0.36 and 0.39, respectively, which was in the range of previously published estimates for those two traits in this species. CONCLUSION: Those findings in a wild bird population demonstrate that telomere length at the end of the growth period is weakly, but significantly, determined by genetic and/or maternal factors taking place before hatching. However, we found no evidence that the brood size manipulation experiment, and by extension the early growth conditions, influenced nestling telomere length. The weak heritability of telomere length suggests a close association with fitness in natural populations.     

Allometric models to estimate foliage biomass of Tamarindus indica in Burkina Faso

Tamarindus indica L. is a multi-purpose tropical species. In West Africa the local people use its leaves daily as a source of food, medicine and income. To prevent the over-exploitation of this species for its use for non-timber forest products, the estimation of foliage production needs to be adressed. This study aimed to (1) assess the effects of distribution zone and tree size on foliage production of T. indica in Burkina Faso, and (2) develop allometric equations to estimate foliage biomass of this species. A semi-destructive method was used to assess foliage biomass of 120 trees over six stem-diameter size classes within two distribution zones (Sub-Sahelian and North-Sudanian). A two-way ANOVA was perfomed to test the effect of distribution zone and tree size class on foliage production. Allometric equations were fitted with 80% of the sample trees randomly selected and 20% were used for model validation. The results showed that between the two factors, tree size class exhibited a significant effect on foliage production of T. indica both in the Sub-Sahelian and North-Sudanian zones. Allometric equations to predict the foliage biomass of T. indica were similar for its distribution zones in Burkina Faso. Therefore, a general model is adequate for the prediction of foliage biomass of T. indica at a larger scale including a variety of ecological conditions. Stem diameter at 1.3 m aboveground was the most accurate predictor variable (adjusted R² = 0.81) with a prediction error of ?2.76%. This study opens up new potentials to develop and use allometric equations for West African trees of high socio-economic value in their effective and sustainable use for non-timber forest products.