Impact of Macrotermes termitaria as a source of heterogeneity on tree diversity and structure in a Sudanian savannah under controlled grazing and annual prescribed fire (Burkina Faso)

Macrotermes termitaria are conspicuous features of savannah ecosystems in the Sudanian and Sahelian zones of West Africa. The mounds, alive or abandoned, are a major source of heterogeneity in the landscape. The purpose of the present study was to assess the impact of termitaria on tree community in a state forest of the Sudanian regional centre (Tiogo forest, Burkina Faso), under controlled burning and grazing experiments. A comparative inventory was carried out in a split-plot experiment (16 subplots of 2500 m²): 8 subplots where fire regime and grazing were controlled and 8 subplots exposed to grazing and with annual prescribed fire since 1992. All tree individuals (≥1.5 m) were recorded, both on termitaria and outside and their basal area at stump level was measured. A total of 61 observed (or 65.7 ± 2.4 estimated) tree species were recorded on 28 Macrotermes subhyalinus mounds (54 observed species or 60.8 ± 3.3 estimated), the immediate surroundings (44 observed and 59.0 ± 0.0 estimated species) and the rest of subplots (56 observed and 63.6 ± 0.0 estimated). Specific density was higher on mounds in comparison with the surroundings (P < 0.05). Results showed that termitaria played a key role in maintaining higher species diversity as compared to their surroundings (P < 0.05). Differences in species diversity between termitaria and immediate surroundings appeared more pronounced in disturbed plots (submitted to both fire and grazing). Some species, such as Tamarindus indica, Boscia senegalensis, Cadaba farinosa, Capparis sepiaria and Maerua angolensis are found solely on termitaria. Besides, the density of trees was significantly higher on termitaria compared to the surrounding (P < 0.05), as well as total basal area per unit of 100 m² area (P < 0.05). We concluded that Macrotermes termitaria play an important role as a source of heterogeneity in this Sudanian savannah woodland ecosystem. This role is particularly important in ecosystems under stresses. Termitaria acted as refuge for tree vegetation. The density and dynamics of M. subhyalinus termitaria should, therefore, be taken into account in the global strategy of the forest resources management and conservation.     

Bioaccumulation of ivermectin from natural and artificial sediments in the benthic organism <Emphasis Type="Italic">Lumbriculus variegatus</Emphasis>

Purpose  

Although ivermectin is a widely used lipophilic parasiticide, data on its potential bioaccumulation in aquatic invertebrates are scarce. In this study, bioaccumulation patterns of radiolabeled ³H-ivermectin from sediments into tissues of the sediment-dwelling worm Lumbriculus variegatus were investigated and assessed.     

The biodiversity of dictyostelids in mountain forests: A case study in the French Alps

Forest management can seriously modify the biodiversity of forest dwelling species, but the consequences are poorly known for certain taxa, particularly soil fauna, for which few studies have been published. We compared the biodiversity of dictyostelids cellular slime moulds in a managed and an unmanaged forest in the French Alps and analysed the influence of environmental factors on species richness and abundance of dictyostelids. To our knowledge, this study is the first one undertaken in the European Alps. We must better understand the influence of various environmental factors on the biodiversity of these organisms if we want to accurately define their functional role in the soil. In our study, dictyostelids showed lower levels of diversity compared to previously published results. The mean species richness of dictyostelids was marginally higher in unmanaged than in managed forests and biodiversity indices were significantly correlated with elevation and pH. This suggests that environmental factors have a predominant effect on the biodiversity of dictyostelids and that the effect of forest management is secondary.     

Changes in physicochemical characteristics and volatile constituents of strawberry (Cv. Cigaline) during maturation

Changes in the volatile composition of strawberries (cv. Cigaline) at six stages of maturity, from 28 to 44 days after anthesis, were investigated over two harvesting seasons. Volatiles were isolated by direct solvent extraction and analyzed by means of GC-FID and GC-MS, with special attention to the quantification of furanones. Firmness, skin color, soluble solids (SS), titratable acidity (TA), SS/TA ratio, organic acids, and sugars were also determined. With increasing maturity, soluble solids, SS/TA ratio, Minolta a value, and levels of sucrose, glucose, fructose, and malic acid increased, whereas Minolta L value, hue angle (), titratable acidity, and levels of citric acid decreased. Furanones and esters were generally not detected before half-red fruits, whereas C(6) compounds were the main compounds in immature fruits. During maturation, levels of these so-called green components decreased drastically, whereas levels of key flavor compounds increased significantly and were closely correlated with skin color development. Maximum volatile production was observed in fully red fruits.     

Phosphorus Fractionation and Short-term Mobility in the Surface Sediment of a Polymictic Shallow Lake Treated with a Low Dose of Alum (Courtille Lake,France)

Lake Courtille was a polymictic eutrophic lake prone to large pH variations and sediment resuspension. Short term P release (96 hr) under laboratory resuspension conditions for two sedimentsample types, surface sediments which represent sediment accumulated over several years and trap sediments which representcurrent year sediment, was studied. The experiments were carriedout in oxic conditions at different pH values. According to phosphorus fractionation, Fe-bound-P, Al-bound-P and Organic-bound-P comprised the largest phosphorus pool (80% of Total Phosphorus). Phosphorus release was from the Fe-P, Al-P and organic fractions. These represent 35% of the total phosphorus content at pH 10. At circumneutral pH, in oxic conditions, a lower quantity of P was released (roughly 4% of total P sediment content) than at pH 10. The organic matter mineralization occurring at the end of summer can also influenceP release as illustrated by the difference in total phosphoruscontent between sediment samples of 2000 and of the last five years. This type of P release was observed in Lake Courtille. High soluble reactive phosphorus content was measured in the water column at the end of summer. Aluminium treatment was thus not efficient in preventing P release. Moreover, a higher alum dose was needed to reduce P content in the water column in order to decrease primary productivity and subsequent organic matter sedimentation.     

Soil conservation policy measures to control wind erosion in northwestern Europe

Wind erosion is not as significant or a widespread problem in Europe as in dryer parts of the world, but it can cause major damage in small areas. The hazard is greatest in the lowlands of northwestern Europe with more than 3 million ha at high-potential wind erosion risk. Crop damage and off-site damage have prompted farmers and policymakers to pay more attention to wind erosion control. A great variety of measures have been developed in the last decades. Most farmers, however, only use measures to protect their high value crops. In existing policies, little attention is paid to the off-site effects and long-term effects of wind erosion. There are no direct policy measures at a European level to control soil erosion, and few measures exist in individual Member States. Agricultural or environmental EC policies offer different policy tools to approach the wind erosion problems related to agricultural practices. Tools like subsidies for the re-afforestation of arable land can help regional policy makers with the implementation of wind erosion control measures. A case study concerning the ‘Code of Good Agricultural Practice’ shows that regional differences result in different control measures that fits best given the physical, social and economic context. The formulation of the practical details of such code should therefore remain a task of the local or regional government. The main objectives of a Code of Good Agricultural Practice could be formulated at national or European level.