Abstract: We present a multi-species model of one plant with two nectivore pollinators. This system has mutualism between the plant and the pollinators, and competition for food between pollinators. Both pollinators are different: the large pollinator can consume all the nectar offered by the plant in each visit; it permits the genetic interchange between plants from different patches, so, it avoids self-fertilization problems. The small pollinator consumes only a fraction of the flower nectar but the seeds produced by its pollination are less successful. The model gives different dynamics depending on both the differences between the pollinators’ growth rates and the inbreeding effect. Stronger oscillations occur when the growth rates are very different. Paradoxically, a high inbreeding causes an increment in populations. The three species system is biologically stable and the asymmetry between pollinator species results in different roles that enhance the global stability and persistence of the system.

Keywords: Pollination; mutualism; population dynamics; competition; mathematical models

Abstract: Exotic plantations of Eucalyptus are replacing large areas of extensive agroecosystems throughout the Mediterranean basin. A comparison of the abundance of ground macro-arthropods in some of major types of traditional land uses in southern Iberia (cork oak woodlands, olive groves, fallow fields, vineyards, and riparian vegetation) revealed that Eucalyptus plantations held the lowest abundances for most groups of arthropods. This indicates that the expansion of Eucalyptus plantations in the Mediterranean is very negative for ground arthropods, and for the many species of vertebrates that depend on them as prey.

Keywords: Exotic plantations, landscape management, ground arthropods

Abstract: Species composition, density, importance value index, diversity, dominance and tree population structure were studied in disturbed and undisturbed stands of tropical semi-evergreen forest in Lunglei District of Mizoram, North-East India. Total number of species in the undisturbed stand was 67 while in the disturbed stand 63 species were recorded. Number of tree and shrub species in the undisturbed stand were higher (32 and 18) than the disturbed stand (17 and 16). However, the number of herbaceous species remained higher in the disturbed stand (30) compared to the undisturbed stand (17). Castanopsis tribuloides (Smith) was common in both stands, and showed dominance in the undisturbed stand with a density of 90 individuals’ ha-1. However Schima wallichii (DC.) Korth Choicy was dominant in the disturbed stand with a density of 125 individuals’ ha-1. In both stands higher dbh classes showed lower density than that of the lower and intermediate girth classes. In general, the undisturbed forest stand showed more density of trees in each dbh classes and the intermediate girth class in particular. The study reveals that the anthropogenic disturbance causes disruption of forest structure and changes community composition which ultimately leads to disruption of tree population structure.

Keywords: Dominance, Species diversity, Floristic composition, Forest structure, Girth class

Abstract: The effect of salt stress on the growth of the Atriplex hortensis was determined by growing plants in soils receiving a one-time irrigation of nutrient solution containing low, medium, and high levels of NaCl. Atriplex plants were grown in sand culture under controlled greenhouse conditions. The experiment was compared to two varieties of A. hortensis. Growth and yield were progressively declined by increasing NaCl concentrations. Atriplex hortensis, an annual halophyte, exhibits significant reduction in height and biomass under saline stress conditions. The photosynthetic activity decreases when plants are grown under saline conditions leading to reduced growth and productivity. Low levels of salinity (5 g/l NaCl) did not cause substantial inhibition of growth but increasing concentrations of salt induced a progressive decline in length and weight of the plants. Salt stress induced a significant decrease in leaf area, but it had no significant effect on leaf water content. The results of present study indicate no differences in salinity tolerance in both Atriplex plants. Another possible conclusion is that improved tolerance to salt stress may be accomplished by decline in growth and photosynthetic activity. Based on these findings the tolerant Atriplex can be grown in moderately NaCl-contaminated soils.

Keywords: Atriplex; salt stress; biomass production; chlorophyll concentration; water content; stomatal conductance

Abstract: The inhibitory effects of heavy metals on self-purification processes in surface water were studied. Toxicities of the metals were evaluated on the grounds of the results of the Biochemical Oxygen Demand (BOD) test in river water. The BOD inhibitions depended on the concentrations of metals and on the incubation time. After one day’s incubation, a full inhibition was found to be caused by Ag at all tested concentrations above 0.02 mg.l–1 for Hg, Cd, Pb, and Cu above 1 mg.l–1, for Be above 2 mg.l–1, and for Co, Ni, and SnII above 5 mg.l–1. A strong inhibitory effect ranging from 50 to 80% was observed for Cd (from 0.2 to 0.7 mg.l–1), Cu (from 0.4 to 1.0 mg.l–1), Be (from 0.5 to 2.0 mg.l–1), Zn (from 1.2 to 5.0 mg.l–1), SnII (from 2.2 to 4.2 mg.l–1), and CrVI (above 4 mg.l–1). AsIII, AsV, MnII, SeIV and SeVI did not cause any BOD inhibition to 2 mg.l–1 (As) res. 5 mg.l–1 (other metals). The inhibitory effect of metals decreased significantly or disappeared with increasing incubation time. Being observed with all metals with toxic effects except for Be, SnII, and CrIII, the decrease was more intense at the beginning of the incubation period.

Keywords: self-purification, biochemical oxygen demand, heavy metals, toxicity

Abstract: Irish and UK uplands and peatlands are of international importance but are under threat from several factors, including heavy grazing pressure. Sheep preferentially graze patches of acid grassland with short dense swards, sometimes referred to as ‘grazing lawns’, and have been implicated in damage to uplands. The aim of this study was to increase our understanding of resource selection by grazers to further inform the design and implementation of conservation strategies. Grazing lawn frequency and habitat condition were mapped and GPS collars were used to track Scottish Blackface sheep on a hill farm in Ireland. Weighted compositional analysis (multivariate analysis of variance) was used to test for random use of different categories of grazing lawn frequency and habitat condition. Grazing lawn frequency was spatially uneven and habitat condition ranged from undamaged to very severely damaged areas. Typically, selection of differing categories of habitat condition was not significant (P>0.05), although the highest selection rank was consistently for the ‘moderate-undamaged’ category. Sheep most selected 1 ha grid squares containing numerous/extensive grazing lawns (P0.05) day, night and yearround. As a simple, efficient indicator of hill use by sheep, which would be a valuable input in models predicting grazing impact on hill vegetation, the mapping of grazing lawn frequency is suggested.

Keywords: agriculture; ecology; environment; resource management; resource selection

Abstract: Coccinellidae are well known predators in agroecosystems. In olive groves they may exert control against scales, such as the black scale, Saissetia oleae (Olivier, 1791). Laboratory studies on the consumption of three phenological stages (eggs, first and second instar nymphs) of S. oleae by four coccinellid species (Chilocorus bipustulatus, Scymnus (Pullus) subvillosus, Scymnus (Mimopullus) mediterraneus and Scymnus (Scymnus) interruptus) were carried out. C. bipustulatus presented a significantly high consumption of eggs, first and second instar nymphs compared with the other species. All coccinellids consumed eggs and first instar nymphs; however the second instar nymphs were only consumed by S. interruptus and C. bipustulatus. In a second experiment, larval stages of C. bipustulatus were reared on different phenological stages of S. oleae. Coccinellid larvae fed with eggs or first instar nymphs completed their life cycle, contrarily to those that were fed with second instar nymphs. The apparent voracity of C. bipustulatus on the different phenological stages of S. oleae is an aspect that suggests the possible use of this coccinellid species in biological control programs against this pest in olive groves.

Keywords: Predation, Chilocorus bipustulatus, Pullus (Mimopullus) mediterraneus, Scymnus (Pullus) subvillosus, Scymnus (Scymnus) interruptus, black scale