The tolerance of four varieties of fenugreek (Trigonella foenum-graecum L.) to seven pre-emergence and six post-emergence herbicides was tested in the glasshouse and some were studied further in the field. Because fenugreek is slow to establish, pre-emergence herbicides will usually be necessary, supplemented perhaps by a post-emergence treatment. Of the pre-emergence compounds tested, fenugreek tolerated trifluralin; methazole; chlorthal-dimethyl plus methazole; metamitron; and nitrofen at realistic rates of application. Trifluralin was particularly promising. The tolerance of fenugreek to this and other dinitroaniline herbicides was studied both in the glasshouse and in the field. A simple technique was used to investigate the site of uptake of these herbicides. Entry through the root produced a greater response than shoot entry. Laboratory arid glasshouse studies of the effect of soil properties on the phytotoxicity of these compounds showed there was a negative correlation between activity and soil organic matter content. The selectivity values of the dinitroanilines between fenugreek and weeds were compared. Trifluralin and isopropalin showed good selectivity except with cruciferous weeds which were very resistant. EPTC is very effective against a wide spectrum of weed species including many which are unaffected by the dinitroanilines, but it is marginally tolerated by fenugreek. In an attempt to improve its selectivity, the effect of herbicide safeners was examined. R25788 and MON4606 as seed treatments gave good results in pot experiments. They protected fenugreek from up to 5 kg/ha EPTC. However, high rates of safeners adversely affected fenugreek growth. Eradicane (EPTC + R25788) as a seed dressing was effective against certain weeds, but it injured the crop. In pot and field experiments, nodulation of fenugreek was affected only when plant growth was reduced by the herbicides. Abnormally low protein content was associated with high diosgenin yield. In pot experiments EPTC with R25788 or with MON4606 reduced diosgenin yield but not protein content. Diquat was used as a desiccant to enhance maturity and reduce post-harvest fungal attack. Seed from desiccated plants yielded more diosgenin than from non-desiccated plants. Pre-planting soil incorporated trifluralin or isopropalin is recommended for weed control in fenugreek. Either MCPB or bentazone plus MCPB is recommended as a supplementary post-emergence treatment for resistant weeds.

Hornborgasjön är en grund och näringsrik slättsjö och är en av Sveriges viktigaste rastlokaler för sjöfåglar. Varje vår och höst samlas stora mängder av bl.a. rastande änder och svanar. Kransalger (Chara spp) är den dominerande undervattensväxten i sjön men där finns också axslinga (Myriophyllum spicatum) och olika typer av nate (Potamogeton spp) som vanligt förekommande. Syftet med den här studien var att ta reda på om det finns något samband mellan rastande sjöfåglar och den undervattensvegetation som finns i Hornborgasjön. Resultaten är framtagna utifrån data från simfågelräkningen och inventeringarna av undervattensvegetationsom utfördes mellan åren 1993–2015. Även sjöfåglarnas samband med abiotiska faktorer som vattenstånd och nederbörd var av intresse att undersöka. Tidigare studier har visat att vattenståndet spelar roll för sjöfåglars tillgänglighet på föda i sjöar och våtmarker. Högre vattennivåer under långa perioder gör att födan troligtvis inte blir lika lättillgängligt för vissa fågelarter men gynnar andra. I längden kanske detta också påverkar mängden och utbredningen av undervattensväxter. Eftersom vattenståndet verkar spela roll för tillgängligheten på föda för en del fågelarter så var det intressant att undersöka om även nederbördsmängden under perioder har en påverkan på mängden tillgänglig föda. Åtta arter av sjöfåglar som i viss utsträckning betar undervattensvegetation samt sex vegetationstyper ingick i studien. Resultaten pekar på att det finns ett signifikant samband mellan antalet rastande sjöfåglar och undervattensvegetation framförallt med kransalger och nate. Knölsvan (Cygnus olor), vigg (Aythya fuligula), brunand (Aythya ferina), snatterand (Anas strepera), och sothöna (Fulica atra) var de arter som påvisade starkast samband med den totala andelen undervattensvegetation. Inget signifikant samband mellan sjöfåglar och vattenstånd eller nederbörd kunde konstateras. / Lake Hornborga is a shallow and nutrient-rich floodplain lake and is one of Sweden's most important stopover points for waterfowl. Every spring and autumn large quantities of migrating ducks and swans gather. Stoneworts (Chara spp) is the dominant underwater plant in the lake,but there are also spiked water-milfoil (Myriophyllum spicatum) and various types of pondweed (Potamogeton spp) as common. The purpose of this study was to find out whether there is any relationship between the migrating waterfowl and the underwater vegetation found in Lake Hornborga. The results are derived from data from bird counts and inventories of underwatervegetation carried out between the years 1993-2015. Even waterfowl associated with abiotic factors such as water levels and precipitation was of interest to investigate. Previous studies have shown that water levels play a role in the availability of seabirds on food in lakes and wetlands. Higher levels of water for long periods make the feed probably less accessible to some bird species but benefit others. In the long run, this may also affect the amount and extent of underwater plants. Since water levels seem to play a role in the availability of food for some bird species, it was interesting to investigate whether the amount of precipitation during periods also has an effect on the amount of available food. Eight species of waterfowl that to some extent graze submerged vegetation and six vegetation types were included in the study. The results indicate that there is a significant correlation between the number of migrating waterfowl and underwater vegetation especially with stoneworts and pondweed. Mute Swan (Cygnusolor), tufted duck (Aythya fuligula), pochard (Aythya ferina), Gadwall (Anas strepera), and the coot (Fulica atra) were the species that showed the strongest relationship with the total percentage of underwater vegetation. No significant correlation between waterfowl and waterlevel or precipitation was found.

My Ph.D. research is based on nearly three years of fieldwork in Tanzania, from December 1978 to September 1981. It attempts to deduce the effects of certain ecological and biogeographic-factors on the structure and species composition of forest bird communities. My principal study areas were in the Usambara Mountains in north-eastern Tanzania, though other forests were visited. My research concentrated on three main aspects. 1. Factors affecting forest bird distribution. I compared the forest avifauna of the Usambaras with those of neighbouring forest areas to determine some of the factors that affect the distribution of forest birds. Altitude appears to have the most important influence on bird distribution and many species are either exclusively lowland or exclusively montane. A few species are restricted to narrow altitudinal bands at intermediate levels. Rainfall is another important factor. Forests in wetter areas tend to have rich avifaunas and several species are restricted to such moist forests. It seems likely that historical factors are also important. Localities in which forests are believed to have survived throughout the driest periods of the Pleistocene are the richest in species today. It appears that such localities often coincide with the areas of highest rainfall. Other factors, such as degree of isolation, vegetation sructure and inter-specific competition, have a less pronounced, though probably real, effect on the avifaunas. Latitude and forest area, however, have no noticeable influence. 2. Factors influencing avian altitudinal zonation. Birds are presumably not affected by altitude so much as by other factors which are themselves influenced by altitude. The Usambara Mountains proved to be an ideal study area for the altitudinal zonation of forest birds since a wide altitudinal span of easily accessible forest survives from only 150m up to over 2250m a.s.l. Birds were counted by means of mist-netting and line transect censuses. If the Usambara forest avifauna is analysed in terms of the presence or absence of species at each altitude, two major "breaks" are detected at 800m and 1650m respectively. Between these two altitudes there are large numbers of both lowland and montane species. In terms of the abundance of species, there is a major break at 450m, above which the avifauna changes in a continuous cline. Several factors probably contribute to this altitudinal zonation. Perhaps the most important is temperature. Many lowland forest species occur at high altitudes only on the forest edge and avoid the cold forest interior. There is a pariculariy noticeable "cut-off" altitude at 1650m, above which many insectivorous species are not found. This is the lowest altitude for the occurrence of cold season frosts. There is also some evidence of inter-specific competition with several pairs of lowland and montane species replacing each other altitudinally. Analyses of altitudinal zonation are greatly complicated by the seasonal vertical movements of forest birds, which I discovered to be far more extensive in eastern Tanzania than has hithertoo been realised. Many species breed at high altitudes in the hot season, moving to lower levels during the colder months. Also many frugivorous, gramrnivorous and nectivorous species are liable to erratic, apparently aseasonal movements in search for food. As a result care has had to be exercised in the interpretation of census results. 3. Comparisons between forest and non-forest bird communities. I also compared the avifaunas of forest and non-forest habitats in the Usambaras. On the Mazumbai Estate, a tea estate at 1500m in the West Usambaras, I had a number of study sites in several different habitat types. The birds were counted by line transect censuses and mist-netting and the habitat structure was measured by estimating the height of the vegetation layers. I also attempted to measure the ecological position of each study species by measuring ten habitat parameters in the territories of breeding birds. The results of these studies suggested that the rigid division of birds into forest and non-forest species, which many ornithologists in Africa have accepted, is simplistic. Many forest species are very conservative and unable to withstand too much interference with their habitat (and similarly many non-forest species avoid areas where there are trees). Several other species, however, are not easy to categorise and some birds characteristic of undisturbed forests are able to survive in some very degraded habitats. The rare and endemic birds in the Usambaras are all forest species and most tend to be among those less tolerant of habitat change. For this reason considerable concern has been ex pressed about the conservation of the Usambara forests. As a result of my research I have been able to draw up a conservation management plan. Forests also have important economic benefits, particularly in the preservation of water catchments and the prevention of soil erosion. Conclusion. In my discussion I have noted that tropical forest bird communities are particularly complex and require long field studies before trends and patterns can be clearly detected. In the past too many conclusions have been drawn from field studies lasting only weeks or months. The forest bird communities of eastern Tanzania may not be typical of those of the tropics as a whole. They appear to differ from those in West Africa and South America in at least three respects: (i). Forest area has little affect on the number of bird species. (ii). Interspecific corn petition does not appear to be particularly important. (iii). No species appears to require primary unexploited forest. I have suggested that these differences are due to the relatively impoverished forest avifauna in eastern East Africa. It seems probable that these forests lost many bird species during the dry periods of the Pleistocene and those that survive today are more adaptable and tolerant of reduction in forest area and exploitation of their habitat.

No description available.

No description available.

The fate of the herbicides isoproturon (formulated as Arelon) and 3,6-dichloropicolinic acid (formulated as Lontrel) and their effects on several microbiological populations and processes in soil and in the wheat rhizosphere were examined under field, glasshouse and laboratory conditions. Effects on pure microbial cultures were also studied. The herbicides took 1 to 6 weeks to reach 50% of their initial concentrations in soil. 14C-labelled isoproturon was transformed in soil, with or without wheat roots, by demethylation, hydrolysis and hydroxylation to release the aniline derivative. There were no significant 14C-containing soil bound residues. Arelon applied to field soil in autumn at 2.5 kg a.i. ha-1 (normal rate) and Lontrel sprayed late in the following spring on winter wheat (Zadok's code 19, 29, 30) at 0.625 kg a.e. ha -1 (5 times recommended rate) caused variable effects including occasional, transient increases and decreases in numbers of bacterial and fungal propagules but no changes in levels of NH4+-N, NO2--N, NO3--N or PO43- in soil. Inconsistent effects, without distinct trends, were also recorded on populations in planted soil during a glasshouse experiment using soil-applied Arelon (0.75 kg a.i. ha-1) and in laboratory - incubated soil treated with either Arelon (1.3 and 6.3 mug a.i. g-1 oven-dry soil) or Lontrel. (0.06 and 0.31 mug a.e. g-1 oven-dry soil). Although in the former study, populations of fluorescent pseudomonads and total bacteria in the rhizosphere were affected for long periods. Growth of pure cultures of bacteria and fungi was not prevented by Lontrel (0.1 to 10.0 mug a.e. ml -1). Arelon (1.0 to 60.0 mug a.i. ml-1) did not affect bacteria but at the highest concentration (about 50 times field rate) there was a decrease in colony growth and pigmentation of some fungi. The results suggest that Arelon and Lontrel, in practical use, are unlikely to have harmful effects on soil micro-organisms and so on soil fertility.

Certain aspects of the biology and ecology of selected wood-decaying, cord-forming fungi were investigated. These included identification of the major species involved and quantitative assessments of their importance in wood decay, particularly of virgin substrata and suppressed oak trees. Cord-forming fungi rapidly arid frequently colonized such substrata and came to occupy large volumes within them (particularly Phanerochaete velutina), first invading peripheral parts of wood in ground contact and then spreading to more central tissues, where they could persist for long periods. The form and extent of individual cord systems and their mode of development in soil were investigated. All species studied developed in a similar manner in non-sterile soil. i.e. growth occurred via fronts of fine cords ('fans') at the advancing edges of systems, which were superseded by more substantial cords behind them, linking the advancing fronts to food-bases. In sterile conditions, however, none of the species investigated (except Phallus impudicus to a limited extent) formed cords. In the field individual cord systems were commonly found to be over 20m in length. Studies involving intraspecific pairings between cord systems of Phanerochaete velutina in soil indicated that a mechanism exists for distinguishing 'like' from 'unlike' mycelial types. An analysis of the spatial di'stribution of a population of Tricholomopsis platyphylla revealed that this species has tetrapolar incompatibility and that a limited number of often extensive mycelial types were present at a woodland site of area 20.8ha. Certain cord-forming fungi physically overgrew Armillaria bulbosa and A. ostoyae in culture and may have been able to at least restrict the spread of Armil1aria species in the bases of suppressed oak trees Cords of selected species were often highly differentiated internally and the various types of constituent hyphae were considered in terms of function namely protection, strengthening and translocation.

A study was made of the susceptibility of young larvae of the tobacco hornworm moth, Manduca sexta, to the action of the benzoylurea diflubenzuron (Dimilin). This insecticide was a very effective stomach poison but ED50 values were lower when insects were maintained in an atmosphere with high rather than low relative humidity. The susceptibility of the insect also depended on the stage (instar) of the insect and its diet. In contrast to its effects on many other insect species, Dimilin exhibited contact toxicity against Manduca and high stomach doses reduced faecal output. There being no previous reports of the isolation of a parasitic fungus from Manduca, a screen was performed using isolates of four species of entomopathogenic fungus, Metarhizium anisopliae (M.E.I.) proved to be very effective and a reproducible bioassay was developed using a dipping technique. Interference from antifungal compounds in the artificial diet was circumvented by feeding experimental insects on tomato leaves. Conidia which were presoaked (P) for 20 h in distilled water prior to inoculation on Manduca larvae germinated more quickly than fresh conidia (F); as a consequence pre-soaked conidia were more pathogenic than fresh. Dual applications of Dimilin (ED50 dose) and Metarhizium anisopliae (ED50 dose) were synergistic in their action against second instax Manduca larvae (using Benz's (1971) criteria). The greater efficiency of pre-soaked conidia (P) was still apparent when they were applied in combination with Dimilin (D). DP treatment killed significantly more second instar larvae than DF. It was hoped that the greater pathogenicity of P and DP treatments would be translated into a reduced period of high relative humidity necessary for the initiation of infection. However, the results were disappointing. Most deaths in the combined insecticide/fungus treatments were due to mycosis, adding support for the hypothesis that the action of Dimilin on the cuticle facilitated the entry of the fungus into the insect. An ultrastructural study was carried out to seek direct support for this conclusion. Treatment with Dimilin did not stop the growth of abdominal tergal cuticle. Post-ecdysial Dimilin-affected cuticle, however, was characterised by the absence of lamellae and presence of globules of melanin-like material. Lateral growth of Metarhizium between the lamellae of normal cuticle was a prelude to vertical penetration primarily via pore canals. Progress towards the epidermis apparently did not occur in a step-wise fashion. Cuticle of Dimilin-treated insects provided little resistance to penetration by hyphae of Metarhizium. Widespread histolysis of post-ecdysial cuticle occurred. In addition, although lamellate pre-ecdysial cuticle was not affected by Dimilin, the cuticle of the pore canals was similar in appearance to, and presumably laid down at the same time as, the post-ecdysial cuticle. Pore canals were, therefore, areas of weakness in the pre-ecdysial cuticle which as a consequence failed to provide a mechanical barrier to the penetrating fungus.

<p>Native submerged aquatic vegetation (SAV) provides critical habitat for estuarine nekton. Relatively high nekton densities also are often associated with the nonnative, Eurasian Watermilfoil (Myriophyllum spicatum), a widely-distributed species in estuaries of the northern Gulf of Mexico. The goal of my study was to assess the habitat value of Myriophyllum with that of a common native SAV (Ruppia maritima) and SNB using two metrics (nekton density and growth of juvenile white shrimp Litopenaeus setiferus). Including estimates of vital rates such as growth together with density can give a more complete assessment. The nursery habitat provided by Myriophyllum for juvenile white shrimp appeared to match or exceed that of naturally occurring habitat types (Ruppia and SNB) in the oligohaline study area. Juvenile white shrimp densities in Myriophyllum (2.2 ? 0.47 m-2) were higher than those in Ruppia (1.0 ? 0.36 m-2). Similarly, white shrimp growth rates were higher in Myriophyllum (1.0 ? 0.07 mm TL d-1, 28.2 ? 2.83 mg d-1) than in Ruppia (0.6 ? 0.09 mm TL d-1, 14.1 ? 2.51 mg d-1). Myriophyllum also supported a nekton assemblage similar to that of Ruppia. Though differences were detected between SAV species, other factors derived from differences in SAV biomass may have driven differences in white shrimp growth rates and nekton densities. My study indicates that nonnative habitat forming species like Myriophyllum can provide an alternative to native habitat, though more research is needed to fully understand the mechanisms at work.

<p>Interactions between species are dynamic and are likely to shift with changes in species ranges due to climate change. With the expansion of new species into incumbent ecosystems a variety of abiotic and biotic factors shape the rate, pattern, and method of invasion. This dissertation utilizes one such boundary of transition, the salt marsh-mangrove ecotone, located in the northern Gulf of Mexico. This dynamic coastal wetland has recently seen the expansion of sub-tropical mangrove species into a previously salt marsh dominated system. This collection of works provides pointed case studies seeking to understand local and patch scale dispersal dynamics, expansion, recruitment, growth, and survival rates along an elevational gradient, and understanding interactions both above- and belowground between mature mangroves and the surround salt marsh. We find that dispersal is overwhelmingly dominated by propagule export, that black mangrove and smooth cordgrass differ in their ability to provide structural provisioning in the short term after restoration, and that mature mangroves have much greater belowground extent than aboveground. By better understanding species-specific interactions at the salt marsh-mangrove ecotone, a greater understanding of future expansion rates can be gained.